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AIR TRANSPORT IN GHANA: SOME CLIMATIC CONSTRAINTS

AIR TRANSPORT IN GHANA: SOME CLIMATIC CONSTRAINTS AVIATION ISSN 1648-7788 print / ISSN 1822-4180 online 2012 Volume 16(3): 88–95 doi:10.3846/16487788.2012.732323 Abdul-Wadood Moomen Curtin University of Technology, West. Australia E-mail: wadood35@yahoo.com Received 09 May 2012; accepted 20 July 2012 Abdul-Wadood MOOMEN Education: BA, Geography and Resource Development, University of Ghana. Diploma in Basic Education, Bagabaga College of Education, Teaching experience: mathematics and geography, 2007 to 2012. Affiliation: Curtin University of Technology, Australia, Faculty of Science and Engineering, Department of Spatial Sciences, PhD student. Research interests: use of geographic information systems (GIS) in resource development. Publications: 2 articles. Abstract. Understanding a definite geographic context is essential for effective air transport management. To date, the consequences of changing weather conditions and climate on the transportation sector in Ghana has been grievous to the economy of the country. Unfortunately, the impact of climate change on the aviation industry has re- ceived very little attention in Ghanaian literature. Meanwhile, it is widely known that transport systems on the whole perform poorly under adverse weather and climatic conditions. This paper seeks to reflect a growing orientation in research and philosophy in the field of air transport and severe weather and climatic constraints. Understanding under - lying principles of climatic conditions and weather is essential to air navigation in Ghana. Clear air turbulence, ceiling and visibility, thunderstorms, electrical phenomenon, climate-induced seasonal variations, and vegetation are some of the threats to air transport across Ghana’s airspace. Information is derived from literature surveys, workplace counts, and an aviation researcher. Overall, large information technology investments, consolidation, and re-structuring are all major issues that must be addressed by stakeholders ambitious to stay afloat and competitive in Ghana’s airspace. Keywords: climatic conditions, adverse weather, severe, extreme, origin, destination, Ghana, navigation. 1. Introduction TROL see a doubling of two days air traffic by the year In the context of improving and expanding air travel 2020 (Eurocontrol 2003). This predetermines the degree in Ghana, the pertinent question that has remained un- of safety measures required on the national airspace of answered over the years is, ‘to what extent does the fre- Ghana. On 19 March 2012, for example, attempts by quency of bad weather and climatic conditions hamper some domestic commercial airliners to land at the Ta- the growth and development of air travel’? A key ques- male and Takoradi airports proved unsuccessful due to tion, according to the International Civil Aviation Or- poor visibility, and those flights had to return to their ganization, is ‘whether the international aviation com- origin. On 20 February 2012, Takoradi Airport was munity fully understands what potential medium-term closed due to poor visibility. The same conditions re- and long-term impacts there will be on commercial avi- peated throughout all the busy airports in Ghana except ation safety’, while stating that the physical impacts and Kotoka International Airport (KIA), where the situation the economic costs of climate change on transport sys- could be managed with the aid of instrument landing tems are subjects ‘for deeper study’ (Economic… 2005). systems (ILS). On 6 June 2000, an aircraft arriving at As the climate changes, extreme events are becoming KIA from Tamale crashed due to poor visibility (vibe. more frequent on average. Predictions by EUROCON- Copyright © 2012 Vilnius Gediminas Technical University (VGTU) Press Technika http://www.tandfonline.com/TAVI Aviation, 2012, 16(3): 88–95 89 com). What is happening in Ghana seems to t fi a lar - 2. Overview of the climate of Ghana ger pattern of frequent extreme weather and climatic 2.1. Wet and dry seasons events in other parts of the world. For example, the severe European heat wave that killed many thousands e w Th eather of a place refers to the day-to-day or hour- of people in 2003 and the powerful hurricanes that have to-hour conditions of the atmosphere. It is the state of struck China and the Americas in the past years are the atmosphere at any given time, whereas climate is the empirical evidence. In the wake of these global severe average spatial-temporal weather conditions (Minia, Z., weather trends, Ghana needs to commence preventive Ghana Meteorological Service). The amount of rainfall preparations or measures in order to stand shoulder varies in Ghana. Rainfall generally decreases north- high to the occasion, should any unfortunate event arise wards. This is explained by the movement of the low as a result of changing weather conditions. Though the pressure belt known as the Inter-tropical Convergence airspace of Ghana is ostensibly clear and gentle, the situ- Zone (ITCZ). The Inter-tropical Convergence Zone ation is gradually changing and might leap from a better (ITCZ) is the meeting point of the tropical continental yesterday to a good today and regrettably to a worse in air mass (CT) and the tropical maritime air mass (MT). the near future. ‘In order to maintain the present level From May to August, the moisture laden air mass (MT) st of development and to move steadily into the 21 cen- travels as far as to the Tropic of Cancer, thereby produ- tury it is absolutely necessary for Ghana to update, im- cing a lot of moisture, even in the northernmost part of prove and maintain facilities and equipment to ensure Ghana. This subsequently produces condition suitable the comfort and safety of the flying public. This should for both plant and animal life. From November to April, be treated as a matter of urgency; otherwise the dan- the tropical continental air mass (CT), which originates gerous bacteria of obsolescence will infest and impair in the Sahara, takes over. The CT travels as far as 5  ° the good work done over the years’ (Dwemoh 2007). latitude. Thus, the air mass is known variously as the The effects of adverse weather and climatic conditions North-East trade winds or the Harmattan (dry season). on transport, particularly air transport in Ghana, have It is generally dust laden, and severe cases for both air scarcely been documented. Rather, all efforts are har - and road navigation are usually recorded between Janu- nessed at mitigating accident situations related to road ary and March. traffic, which is the most patronised means of trans- 2.2. Climatic regions of Ghana port in Ghana. However, now is the time to place more Based on average spatial weather conditions with respect premiums on the prevention of accidents on other to time, Ghana is classified into four major climatic re- means of transport, especially air transport, which is gions. The climate of a geographic region is indispens- fast becoming the closest substitute or alternative op- able to the extent that climate determines the type of ve- tion to road traffic. A study by M. A. Rossetti shows that getation of an area. The major climatic regions of Ghana for 66 out of 5,700 accidents in the USA between 1993 are; tropical interior, wet semi-equatorial, dry equatorial, and 2002 the reported primary cause was weather (Ros- and wet equatorial. setti 2002). Poor visibility delayed about 14 domestic and international flights serving Beijing (December 2.2.1. Tropical interior 2011). Prominent causes of air flight delays range from This climatic region covers all three regions of north- extreme meteorological conditions and maintenance to ern Ghana and parts of the region of Brong-Ahafo. severe weather and climate (Koetse, Piet 2007). J. Evans, Of particular interest is Tamale Airport. The region S. Allan. and M. Robinson attempt to qualify the delay experiences short but heavy rainfall. Annual rainfall impact of convective weather noted that convective ranges between 1100 mm and 1250 mm. Cumulus and weather will reduce the capacity of an airport but rarely cumulonimbus are the cloud type peculiar to the re- will thunderstorms close traffic to both arrivals and de- gion. Rains become more intensive between August partures for more than 15 minutes (Evans et al. 2004). and September as the ITCZ is on its way back to the Weather is an integral component of climate. Hence, the equator. The rainfall types here are convectional, char - climatic regions within which most active airports op- acterised by massive thunderstorms, lightning, and erate must be understood well by all stakeholders (air- windstorms. This is a threat to air navigation. Lightning line operators, travellers, and air traffic management). and thunderstorms have the potential of striking down This review consists of four major sections after the in- flights at a certain flight level. For the aviation sector, troduction in section 1. Section 2 covers an overview of wind speeds are important because of their impact on the climate of Ghana. Section 3 analyses and synthesises safety. Extreme wind speed implies that aircraft are severe weather and its potential impacts on air naviga- not allowed to land at alternate aerodromes. This has tion in Ghana. Section 4 comprises conclusions and re- drastic cost implications for both airlines and travellers. commendations. 90 A-W. Moomen Air transport in Ghana: some climatic constraints Adversely, high winds imply that the departure of air- Less than 1000 mm, usually between 740 mm and craft will be delayed. Wind speeds and directions also 890  mm, of rainfall is annually recorded, however. e Th influence the use of runways and increase the probabil- effect of the harmattan is minimal. The region also ex- ity of accidents. For example, one of the largest aviation periences double maxima rainfall. But second rains accidents at Schipol Airport in the Netherlands in 1997, sometimes do occur in negligible amounts. This explains after the EL-AL Boeing catastrophe in 1992, was due why Accra is more feasible and favourable than other re- to the landing of a Transylvania plane with very strong gions in terms of navigation. Kotoka International Air- crosswinds. However, the tropical interior experiences port (KIA) is located in this region. Temperature varies single maxima rainfall, which usually starts in late April all year round, between 25 and 28°C. Relative humid- and lasts until early October. By late October, the rains ity ranges between 60 and 75%. Weather and climatic abruptly give way to the harmattan, which is accom- conditions in this region are moderate all year round, panied by wind shear stress. The dry season spans from supporting navigational activities. Thus, KIA’s location November to March. Hazy conditions become the dom- oer ff s it an advantage over all other airports in the coun- inant factors influencing air travel at this period of the try to handle landing and takeo, ex ff cept in extremely year. Relative humidity can fall as low as 20% in the dry severe cases. For example, average delays in Accra are 60 season and rise to over 80% in the rainy season. Tem- minutes for arrivals and 74 minutes for departures. peratures are quite steady in Tamale: 23°C minimum at 2.2.4. Wet equatorial/south-western equatorial night and 33°C on average during the day. This climatic region records the highest annual rainfalls 2.2.2. Wet semi-equatorial in Ghana. The region experiences showers throughout e Th wet semi-equatorial climate type covers the southern the year; of premium value in this discourse is Takoradi fringes of Brong-Ahafo, the entire Ashanti and Eastern military/public Airport. regions, and some parts of the Western Region (where Annual rainfall ranges between 1900  mm and Jasikan is located). Places of interest under this climatic 2100 mm. But due to climate change, annual rainfall in region are Sunyani Airport and Kumasi airport, both some years reaches about 2500  mm, a typical example serving domestic flights but can also serve as alternat- being the Axim area. Convectional rainfall occurs all ive aerodromes to international flights to Ghana or her over the world but especially within the tropics. It is usu- neighbours. The wet semi-equatorial region experiences ally heavy and accompanied by thunder and lightning. longer double maxima rainfall. The region sometimes Air navigational activities in this region are expected experiences convectional precipitation and other times to rise geometrically in the near future because of the experiences conventional precipitation within any of the discovery of oil and gas in commercial quantities in the two major rainy seasons in a year. No single precipita- region. Thus, conditions relating to weather and climate tion type is consistent. Convectional and conventional have come into the focus of organisations involved with rains are generally associated with thunder and light- aviation and the oil companies, as well as other symbi- ning. Such events contribute to the seasonal interrup- otic establishments. Precipitation characteristics in this tions on navigational activities in this region. It is risky region appear unfavourable to the much needed expan- to fly through convective weather conditions with their sion of air transport, especially commercial aviation. maximum accident potential. Temperatures in Takoradi area range between 21°C e Th first rains fall between April and July, whereas and 28°C, while relative humidity is approximately 80%. the second rains are oen exp ft ected between September e s Th kies above this region are generally areas where and November. The region experiences harmattan and icing takes place. In January or late December, when the its rippling effect between January and March. Hazy con- region experiences haze, visibility is impaired, making it ditions set in instantaneously, thereby resulting in flight difficult for landing or takeoff of flights. On 13 February delays and cancellations. Mean annual rainfall can exceed 2012, visibility impaired by haze did not allow commer- 1600 mm. Relative humidity is about 78% with temperat- cial flights to land at Takoradi Airport. ures around 28°C. That notwithstanding, current condi- 3. Severe weather tions are subject to changes as a result of climate change. Severe weather is the predominant cause of aviation 2.2.3. Dry equatorial accidents (Mahapatra 1999). In addition to cata- The dry equatorial region is found along the coast of strophic crashes, atmospheric turbulence originating Ghana. Major cities harbouring this type of climate are from severe weather creates discomfort and injury due Accra and Cape Coast, as well as the coastal fringes of to dislocation of cabin objects and passengers. Severe the Volta Region. The characteristics of the dry equat- weather disturbance includes thunderstorms, turbu- orial climate region are similar to those of the tropical lence, convection-induced ceiling and visibility, and interior. Aviation, 2012, 16(3): 88–95 91 in-flight icing (Kulesa 2002). The CPB has estimated track data during six thunder-storms in 1999 over the that a ‘wrongly’ configured airport like Schipol – im- Memphis, Tennessee Centre. They note that the main dif- plying that the number of hours the airport has to close ficulty with this study is the identification of deviations down is unnecessarily long–may lead to disadvantages since en route aircraft can generally avoid the storm edge for the aviation sector amounting to between 3 mil- by adjusting their course by as little as 10 to 20 degrees. lion and 1 billion euro (CPB 2002). Airlines have to Terminal area deviations require an aircraft to forfeit po- compensate passengers for delays, providing meals or sition in the landing queue and it is subsequently moved snacks or both. Flight delays at the airport of origin to the end of the queue at very busy airports like Heath- are less costly and safer for the flight operator than air - row in the UK. borne delays. Severe weather is estimated to cause 70% Convection, the upward motion of warm air that of all delays while also being an important contributory causes thunderstorms, is most prominent between June factor in 23% of all aviation accidents in the USA. Poor and July in Accra, May and June near Takoradi and Ku- visibility in the summer months and rain storms in the masi, and July and September near Sunyani and Tamale winter months lead to substantial delays and numer- in Ghana. Pilots are less likely to pass through line thun- ous cancellations (Eads et al. 2000). This alone explains derstorms since they have fewer gaps in the system and that weather is an integral component of the climate in are generally viewed as more hazardous (Jeffrey 2008). which flights navigate. o Th ugh turbulence is the primary concern for pilots, several harmful atmospheric effects may be experienced 3.1. Potential impact of severe weather on air near a thunderstorm (Mahapatra 1999). Lightning dam- navigation age can remove an aircraft from operation and result in Adverse weather conditions lead among others to an in- both loss of revenues and excess maintenance costs. It crease in the average travel time, increase in spread of is generally benign for aircraft with electrically condu- travel times, and an increased probability of accidents cive skins such as aluminium skins. The cumulonimbus (Koetse, Piet 2007). Thus, generalized costs of transport clouds that are common in Ghana contain ions that can are ae ff cted. Under severe weather conditions, people lead to the crash of a flight. consider cancelling certain trips, depending on the pur- 3.1.2. Downburst pose of the trip. A downburst is a strong downdraft which causes dam- 3.1.1. Thunderstorms/windstorms aging winds on or near the ground (National Weather A thunderstorm is a rain shower during which you Service Forecast Office, Columbia, SC). Cold air be- hear thunder. Since thunder comes from lightning, all gins to descend from the middle and upper levels of thunderstorms have lightning. A thunderstorm is clas- a thunderstorm (falling at speeds of less than 20 miles sified as ‘severe’ when it contains one or more of the an hour). A downburst is a localised area of damaging following: hail ¾  inch or greater, winds gusting in ex- winds caused by air rapidly flowing down and out of cess of 50 knots (57.5 mph), or a tornado. Worldwide, a thunderstorm (National Severe Storm Laboratory, there are an estimated 16 million thunderstorms each NSSL). Damage from downbursts can be so severe that it year. At any given moment, there are roughly 2,000 is mistaken for tornado damage. Downburst damage can thunderstorms in progress around the world (National cover hundreds of square miles or be limited to a single Oceanic and Atmospheric Administration, NOAA). field. Downburst induces haze-like conditions, thereby Windstorms make it difficult to control aircraft, espe- posing a threat to flights during landing or takeo.ff cially during landing. Underestimating wind shear and 3.1.3. Turbulence direction may mean that wrong decisions are taken on the design of airports in terms of the capacity and ori- In fluid dynamics, turbulence or turbulent flow is a entation of runaways. For instance, within the tropical flow regime characterised by chaotic and stochastic interior climate region of Ghana, rains are generally property changes. This includes low momentum dif- preceded by very strong windstorms that uproot very fusion, high momentum convection, and rapid vari- thick and large trees and damage buildings. Such winds ation of pressure and velocity in space and time. Nobel can be catastrophic for aircraft. Laureate Richard Feynman described turbulence as ‘the un Th derstorms can close airports, degrade airport most important unsolved problem of classical physics’. capacity for arriving and departing flights, and hinder Turbulence is air movement that normally cannot be or stop ground operations. Thunderstorms are a severe seen. It may occur when the sky appears to be clear weather event of great concern to aviation. D. Rhoda, and can happen unexpectedly. It can be created by any E. Kocab and M. Pawlak studies the deviations of pilots number of different conditions, including atmospheric from nominal flight routes due to weather (Rhoda et al . pressures, jet streams, mountain waves, cold or warm 2002). e Th human analysts studied 43.5 hours of flight fronts, or thunderstorms. There are several notable 92 A-W. Moomen Air transport in Ghana: some climatic constraints problems with clear air turbulence. It cannot always 3.1.5. Ceiling and visibility be foreseen, so there is no warning. It is usually felt Low ceiling and reduced visibility are safety hazards for at its mildest on the flight deck and is generally more all types of air navigation. Haze (dust-laden winds) dur- severe in the aft section. It can occur when no clouds ing harmattan and liquid water in the atmosphere (rain) are visible. Aircraft radar cannot detect it. It is common is the major causes of visibility ceiling. In the USA, stat- at high altitudes, where a cruising airliner can suddenly istics indicate that ceiling and visibility were cited as con- enter a turbulent area. Non-convective turbulence is a tributory factors in 24% of all general aviation accidents major aviation hazard. All aircraft are vulnerable to between 1989 and early 1997 (Gloria et al. 2003). Ghana turbulent motions. Non-convective turbulence can be had her own share in 2000, when an Air Force aircra ft present at any altitude and in a wide range of weather landed o ff the main runway at Kotoka International Air - conditions after occurring in relatively clear skies as port (KIA). The situation was a result the impairment clear air turbulence. The most hazardous clear air tur - of visibility caused by a heavy downpour. In Ghana, not bulence occurs in opposing motion to an aircraft. Any including KIA, at a certain visibility range only Air Force aircraft entering turbulent conditions is clearly vulner - flights can manage to land at Takoradi, Kumasi, Sunyani, able to damage; smaller aircraft are susceptible at lower or Tamale airports. Air Force flights have a light system levels of turbulent intensity than are large aircraft. Air - that aids visibility and enhances landing. Thus, commer - craft may experience jostling, which is a discomfort for cial airlines may have to delay or cancel flights because passenger and crews, to sudden accelerations that can of their visibility range policies. Depending on the size result in serious injury and temporary loss of aircra ft of aircraft, minimum visibility required before landing control. It further causes reduced flight operation and is 1800 meters. Low ceiling and poor visibility accidents delays. Turbulence is the leading cause of in-flight in- occur when pilots who are not properly rated or are y fl - juries. There are countless reports of occupants who ing an aircraft not equipped with the necessary instru- were seriously injured while moving about the passen- mentation encounter such conditions. This can result in ger cabin when clear air turbulence was encountered. loss of control or controlled flight into terrain. In 1991, the University of Illinois, USA, used simulated weather 3.1.4. Jet streams conditions to test twenty Visual Flight Rule (VFR) rated A jet stream is defined as a current of rapidly moving air pilots. When deprived of visual contact, each pilot ex- that is usually several thousand miles long and wide, but perienced loss of control. It on average took approxim- is relatively thin (Department of Atmospheric Sciences, ately 178 seconds, giving each pilot less than 3 minutes University of Illinois). They are found in the upper levels to live aer ft entering a cloud (Kulesa 2002). Low ceiling of Earth’s atmosphere at the tropopause, the boundary and poor visibility are not just safety issues. They can between the troposphere and stratosphere. Jet streams are also severely degrade the efficiency of commercial and important because they contribute to worldwide weather military aviation, reduce the capacity of an airport, and patterns and as such they help meteorologists forecast lead to airborne or ground delays that result in diver- weather based on their position. In addition, they are sion and cancellations, missed connections, and extra important to air travel because flying in or out of them operational costs. can reduce flight time and fuel consumption (NOAA). Inversely, jet streams moving in the opposite direction 3.1.6. In-flight icing to flight can lead to shortages of fuel and consequently This is the build up of ice on an aircraft during flight at flight may crash down. Thanks to research conducted altitudes above freezing. Hail (spherical or irregular pel- by pilots and meteorologists, it is understood today that lets of ice) is also a nuisance to air navigation. Sunshine there are two main jet streams, which are located in the determines the weight of wind and humidity. When it northern hemisphere. While jet streams do exist in the is sunny, the wind is light and support for aircraft lift southern hemisphere, they are strongest between the is minimal. When the temperature is low, humidity latitudes of 30°N and 60°N. The weaker subtropical jet increases, and the wind is heavy, aiding lift. But when stream is located closer to 30°N. The location of these temperatures become cold, cloud or ice formation be- jet streams shifts throughout the year however, and they comes possible. In icing situations, aircraft movement is are said to ‘follow the sun’ since they move north with ae ff cted. At altitudes where such icing occurs, ice may warm weather and south with cold weather. Jet streams build up on control surfaces, instrument orifices, pro - are also stronger in the rainy season because there is a pellers, and airspeed instrument. This alone can poten- large contrast between colliding Arctic and tropical air tially reduce airplane lift by 25%, increase drag, and lead masses. In the dry season, the temperature difference is to loss of control. In-flight icing causes approximately less extreme between the air masses and the jet stream 11% of all weather-related accidents among general avi- is weaker (NOAA). ation aircraft (Gloria et al. 2003). Aviation, 2012, 16(3): 88–95 93 3.1.7. Vegetation and birds finally a strong tailwind, representing an extreme situ- ation just prior to impact. During takeoff the pilot ex- Climate ae ff cts the vegetation of an area. e Th alternating periences a headwind and increased aircraft perform- effects of wet and dry seasons determine the life pro- ance, followed by a short period of decreased headwind, cesses of a region. During the rainy season, most grasses a downdraft, and finally a strong tailwind. and trees develop new flowers and leaves; insects gather Another finding of the study is that air turbulence around the new flowers and leaves, in turn serving as can be immensely catastrophic and hostile to air navig- prey to migrating birds such as sparrows, egrets and vul- ation. The effects of air turbulence range from jostling, tures. Thus, vegetation and forests, which are dependent loss of control, flight route deviation, stalling movement on climate, encourage bird habitation around an airport. to a crash. The biggest enemy of an aircraft is the bird, and since Moreover, in-flight icing has also been found to be aircraft cannot avoid birds during landing or takeoff, a severe weather condition that has the potential to de- disaster is bound to occur. Aircra ft that use jet propellers crease airspeed and even worse cause a flight to land pre- are especially vulnerable. If a bird flies into the propeller, maturely as it adds more weight than the capacity of the the engine will stop abruptly, leading to fatalities. Many flight. cases of accidents associated with birds have occurred in In terms of commercial use, the jet stream is im- the USA and Canada. portant for the airline industry. One of the most import- Forecast data parameters are applied to critical air- ant impacts of the jet stream though is that as a strong craft thresholds such as icing, turbulence, convection, current of rapidly moving air, it has the ability to push IFR conditions, winds, and crosswinds along a flight weather patterns around the world. As a result, most path. When critical weather thresholds are identified, the weather systems do not just sit over an area, but they are specific points are labeled to show favorable, marginal, instead moved forward with the jet stream. This phe- and unfavorable (or adverse) hazardous flight weather, nomenon hinders aircraft navigation. depending on the exceeded threshold. Thus, a tailored Since weather conditions can seriously restrict op- flight route weather effects field is created for each air - erations and levels of service available to system users, craft based on the aircra’ft s specific weather sensitivity the manner by which weather is observed and forecast thresholds (Knapp et al. 2006). and the way in which this information is disseminated 4. Conclusions and used in making air traffic management decisions must be addressed with optimal and innovative techno- The goal of the study is to inform air transport policy logy. and development planners and implementers in Ghana To estimate the impact of a convective weather sys- to create and protect safer and more efficient air trans- tem on en-route airspace, the distribution of the loca- port services in the country and also to enable them at tion and extent of the convective weather must be known all times to keep abreast of weather conditions within (FAA). It is therefore imperative to deduce from the liter- the skies of the country at all lengths and heights of ature that existing convective weather can be forecast by flight. comparing historical national convective weather for an e s Th tudy finds two major categories of climatic hour. This can only be accomplished by using convective conditions that influence air travel: short term (instant- weather detection products, which are lacking at airports aneous) and long term (seasonal). The study reveals that in Ghana, as a preventive measure against global severe ceiling and visibility are instantaneous climatic condi- weather trends hampering air transportation. tions (weather) mostly ae ff cting landing and takeoff at e m Th agnitude of aircraft delays during thunder - various origins and destinations. Ground and airborne storms and unclear weather conditions is large. Flights delays can consequently occur, adding to the operational can be re-routed through longer paths further from costs of airlines and providing immeasurable inconveni- their original flight plan instead of cancelling or delay- ence to passengers. ing. There should be a more rigorous method to define e p Th aper also finds that thunder, lightning and the area of impact of the severe weather system and the windstorms are seasonal convective weather phenom- flights that potentially could be ae ff cted. Unfortunately, ena that obstruct air navigation. These phenomena can you cannot look at a thunderstorm and see whether it is lead to loss of control by a pilot or even outright strike going to be severe. Doppler radar is able to look inside by lighting. thunderstorms and ‘see’ the movement of air, giving met- e s Th tudy finds that downbursts are dangerous to eorologists’ indications of microburst and allowing them navigation. The rapid change in wind speed and/or dir - to issue warnings to pilots. ection poses a very real threat to airplanes during takeo ff It is further learnt from the literature and reports and landing. During landings the airplane begins its des- of investigations that the use of integrated approaches cent, flying into a strong headwind, a downdraft, and 94 A-W. Moomen Air transport in Ghana: some climatic constraints to provide improved guidance of convective weather (GNSS). GNSS comprises all forms of satellite-based hazards for transoceanic flights could help mitigate navigation systems that provide global coverage and sig- potential hazards. The Ghana Civil Aviation Authority nals for navigation, positioning surveillance, and tim- (GCAA), together with other stakeholders, should de- ing information for aviation and space applications. The velop advanced concepts of using weather forecast mod- GNSS comprises three categories: GNSS-1, GNSS-2 and els to create probabilistic weather-related impact predic- GNSS-3. Ghana is under the GNSS-3 category, countries tions for today’s consumption by air-traffic management without the capacity or necessary infrastructure to de- planning in Ghana. This could necessarily be incorpor - ploy satellites but which have or seek to develop local ated into largely automated decision-support tools in the systems to explore the full potential of the global sys- near future. tems. GNSS signals integrated with additional informa- Today, movement of the jet stream north has tion layers enable air navigation and flight tracking. e Th been detected, indicating possible changes in climate. system includes waypoints as well as precise navigation Whatever the position of the jet stream though, it has collision avoidance, cargo monitoring, and search and a significant impact on the world’s weather patterns rescue operations. The European Global Navigational and severe weather events like floods and droughts. It is Operating System (EGNOS), which also is an aspect of therefore essential that meteorologists and other scient- GNSS-2, helps national, intercontinental, continental ists understand as much as possible about the jet stream flights identify alternate aerodromes whiles in-flight. and continue to track its movement, to in turn monitor EGNOS directly provides flight height reduction in angle such weather around Ghana. A detailed assessment of of approach (direct and curved), better lateral guidance, the primary and supplementary sensor network for each optimised routes and fewer diversions, increased airport of the major airports in Ghana should be conducted. capacity (for example, helicopters); allows operation in KIA is the only airport in Ghana that has an instrument non–ILS equipped airports; avoids expensive land-based landing system (ILS), which permits landing even dur- navigational aids and their maintenance; and above all ing severe weather. increases safety. When extreme weather and climate Worth acknowledging is the idea acquired from the conditions eventually lead to accidents and tragedies in literature reviewed that Ghana Airspace Management Ghana’s airspace, both passengers and freight transport needs to develop strategies and products for forecasting will suffer. The negative economic repercussions that the potential for icing. Such a tool or mechanism will may arise as a result might be incalculable. People want enable users to better anticipate where icing hazards are to travel and need to travel; we should therefore make likely to occur. It will further allow air traffic controllers it possible for each and every one of us now and in the to make more informed decisions when assigning alti- future. tudes to aircrafts. References Furthermore, an algorithm that can help forecast CPB. 2002. Gevolgen van uitbreiding schipol [Consequences turbulence is vital in Ghana’s airspace navigation. The al- of extension of schipol airport]. USA, Illinois University: gorithm should be able to forecast turbulence models, jet Den Haag. DAS. streams, mountain-induced turbulence, and convective Dwemoh, E. R. K. 2007. History of civil aviation in Ghana. induced turbulence. Great attention should be placed on Ghana Civil Aviation Authority. Aviation Digital Data Service. This is a tool available on Eads, G. C.; Kiefer, M.; Mendiratta, S., et al. 2000. Reducing weather related delays and cancellations at San Francisco the Internet. It allows pilots, airline dispatches, and other International Airport: CRA Report No. D01868-00. users’ easy access to weather data. “Flight path Tool” is a Eurocontrol. 2003. User manual for the base of aircraft data component of ADDs, which displays vertical cross-sec- (BADA): Revision 3.5. Technical Report. European Organ- tions of turbulence, icing, thunderstorms, and other avi- isation for the Safety of Air Navigation. ation weather hazards for specific flight altitudes and Evans, J.; Allan, S.; Robinson, M. 2004. Quantifying delay re- duction benefits for aviation convective weather decision flight paths selected by the user. th support systems, in 11 Conference on Aviation Range and e h Th azy conditions that negatively influence air Aerospace Meteorology. 4–8 October, 2004. Hyannis, MA. space navigation around Takoradi, Kumasi, Sunyani, Gloria, J. K.; Pace, D. J.; Fellner, W. L., et al. 2003. e F Th AA and Tamale airports in Ghana during harmattan could Aviation Weather Research Program’s Contribution to Air be checked with forestation. But that is not to suggest Transportation Safety and Efficiency. Washington DC: Fed- eral Aviation Administration,TRW Inc. that forests should be allowed to flourish around air - Review of Air Transport Developments in 2005. ICAO Annual ports. Grasses and trees around runways, taxiways and Report, 2005. aprons must be reduced to the barest minimum to avoid Jeffrey, M. H. 2008. Collaborative en route airspace manage- bird habitation and its consequences at the airport. ment considering stochastic demand, capacity, and weather e l Th atest technology that has proven crucial to the conditions: Dissertation. Virginia, Blacksburg: Virginia Polytechnic Institute. aviation industry is global navigation satellite systems Aviation, 2012, 16(3): 88–95 95 Knapp, D. I.; Raby, J.; Measure, E., et al. 2006. A weather de- th cision aid for unmanned aerial vehicle missions, in 12 Conference on Aviation, Range, & Aerospace Meteorology. 29 Jan–2 Feb. 2006. Atlanta, GA, Amer. Meteor. Soc., P 10.5. Koetse, M. J.; Piet, R. 2007. Climate Change, Adverse Weather Conditions, and Transport: A Literature Survey. The Neth- erlands, Amsterdam: VU University Department of Spatial Economics. Kulesa, G. 2002. Weather and aviation: How does weather af- fect the safety and operations of airports and aviation, and how does FAA work to manage weather – related effects?, in e P Th otential Impacts of Climate Change on Transport- ation Workshop. October 1–2, 2002, DOT Center for Cli- mate Change and Environmental Forecasting. Mahapatra, P. 1999. Aviation weather surveillance systems ad- vanced radar and surface sensors for flight safety and air traffic management, volume 183. Progress in Astronautics and Aeronautics. The American Institute of Aeronautics and Astronautics and e I Th nstitution of Electrical Engin- eers. http://dx.doi.org/10.1049/PBRA008E Rhoda, D.; Kocab, E.; Pawlak, M. 2002. Aircraft encounters with thunderstorms in en route vs. terminal airspace th above Memphis, Tennessee, in 10 Conference on Aviation, Range, and Aerospace Meteorology. 13–16 May, 2002. Port- land, OR: American Meteorological Society. Rossetti, M. A. 2002. Potential impacts of climate change on railroads, in The Potential Impacts of Climate Change on Transportation Workshop Summary. 1–2 October 2002 [on- line]. Available from Internet: http://climate.volpe.dot.gov/ workshop1002 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aviation Unpaywall

AIR TRANSPORT IN GHANA: SOME CLIMATIC CONSTRAINTS

Moomen, Abdul-Wadood
Aviation – Oct 2, 2012
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1648-7788
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10.3846/16487788.2012.732323
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AVIATION ISSN 1648-7788 print / ISSN 1822-4180 online 2012 Volume 16(3): 88–95 doi:10.3846/16487788.2012.732323 Abdul-Wadood Moomen Curtin University of Technology, West. Australia E-mail: wadood35@yahoo.com Received 09 May 2012; accepted 20 July 2012 Abdul-Wadood MOOMEN Education: BA, Geography and Resource Development, University of Ghana. Diploma in Basic Education, Bagabaga College of Education, Teaching experience: mathematics and geography, 2007 to 2012. Affiliation: Curtin University of Technology, Australia, Faculty of Science and Engineering, Department of Spatial Sciences, PhD student. Research interests: use of geographic information systems (GIS) in resource development. Publications: 2 articles. Abstract. Understanding a definite geographic context is essential for effective air transport management. To date, the consequences of changing weather conditions and climate on the transportation sector in Ghana has been grievous to the economy of the country. Unfortunately, the impact of climate change on the aviation industry has re- ceived very little attention in Ghanaian literature. Meanwhile, it is widely known that transport systems on the whole perform poorly under adverse weather and climatic conditions. This paper seeks to reflect a growing orientation in research and philosophy in the field of air transport and severe weather and climatic constraints. Understanding under - lying principles of climatic conditions and weather is essential to air navigation in Ghana. Clear air turbulence, ceiling and visibility, thunderstorms, electrical phenomenon, climate-induced seasonal variations, and vegetation are some of the threats to air transport across Ghana’s airspace. Information is derived from literature surveys, workplace counts, and an aviation researcher. Overall, large information technology investments, consolidation, and re-structuring are all major issues that must be addressed by stakeholders ambitious to stay afloat and competitive in Ghana’s airspace. Keywords: climatic conditions, adverse weather, severe, extreme, origin, destination, Ghana, navigation. 1. Introduction TROL see a doubling of two days air traffic by the year In the context of improving and expanding air travel 2020 (Eurocontrol 2003). This predetermines the degree in Ghana, the pertinent question that has remained un- of safety measures required on the national airspace of answered over the years is, ‘to what extent does the fre- Ghana. On 19 March 2012, for example, attempts by quency of bad weather and climatic conditions hamper some domestic commercial airliners to land at the Ta- the growth and development of air travel’? A key ques- male and Takoradi airports proved unsuccessful due to tion, according to the International Civil Aviation Or- poor visibility, and those flights had to return to their ganization, is ‘whether the international aviation com- origin. On 20 February 2012, Takoradi Airport was munity fully understands what potential medium-term closed due to poor visibility. The same conditions re- and long-term impacts there will be on commercial avi- peated throughout all the busy airports in Ghana except ation safety’, while stating that the physical impacts and Kotoka International Airport (KIA), where the situation the economic costs of climate change on transport sys- could be managed with the aid of instrument landing tems are subjects ‘for deeper study’ (Economic… 2005). systems (ILS). On 6 June 2000, an aircraft arriving at As the climate changes, extreme events are becoming KIA from Tamale crashed due to poor visibility (vibe. more frequent on average. Predictions by EUROCON- Copyright © 2012 Vilnius Gediminas Technical University (VGTU) Press Technika http://www.tandfonline.com/TAVI Aviation, 2012, 16(3): 88–95 89 com). What is happening in Ghana seems to t fi a lar - 2. Overview of the climate of Ghana ger pattern of frequent extreme weather and climatic 2.1. Wet and dry seasons events in other parts of the world. For example, the severe European heat wave that killed many thousands e w Th eather of a place refers to the day-to-day or hour- of people in 2003 and the powerful hurricanes that have to-hour conditions of the atmosphere. It is the state of struck China and the Americas in the past years are the atmosphere at any given time, whereas climate is the empirical evidence. In the wake of these global severe average spatial-temporal weather conditions (Minia, Z., weather trends, Ghana needs to commence preventive Ghana Meteorological Service). The amount of rainfall preparations or measures in order to stand shoulder varies in Ghana. Rainfall generally decreases north- high to the occasion, should any unfortunate event arise wards. This is explained by the movement of the low as a result of changing weather conditions. Though the pressure belt known as the Inter-tropical Convergence airspace of Ghana is ostensibly clear and gentle, the situ- Zone (ITCZ). The Inter-tropical Convergence Zone ation is gradually changing and might leap from a better (ITCZ) is the meeting point of the tropical continental yesterday to a good today and regrettably to a worse in air mass (CT) and the tropical maritime air mass (MT). the near future. ‘In order to maintain the present level From May to August, the moisture laden air mass (MT) st of development and to move steadily into the 21 cen- travels as far as to the Tropic of Cancer, thereby produ- tury it is absolutely necessary for Ghana to update, im- cing a lot of moisture, even in the northernmost part of prove and maintain facilities and equipment to ensure Ghana. This subsequently produces condition suitable the comfort and safety of the flying public. This should for both plant and animal life. From November to April, be treated as a matter of urgency; otherwise the dan- the tropical continental air mass (CT), which originates gerous bacteria of obsolescence will infest and impair in the Sahara, takes over. The CT travels as far as 5  ° the good work done over the years’ (Dwemoh 2007). latitude. Thus, the air mass is known variously as the The effects of adverse weather and climatic conditions North-East trade winds or the Harmattan (dry season). on transport, particularly air transport in Ghana, have It is generally dust laden, and severe cases for both air scarcely been documented. Rather, all efforts are har - and road navigation are usually recorded between Janu- nessed at mitigating accident situations related to road ary and March. traffic, which is the most patronised means of trans- 2.2. Climatic regions of Ghana port in Ghana. However, now is the time to place more Based on average spatial weather conditions with respect premiums on the prevention of accidents on other to time, Ghana is classified into four major climatic re- means of transport, especially air transport, which is gions. The climate of a geographic region is indispens- fast becoming the closest substitute or alternative op- able to the extent that climate determines the type of ve- tion to road traffic. A study by M. A. Rossetti shows that getation of an area. The major climatic regions of Ghana for 66 out of 5,700 accidents in the USA between 1993 are; tropical interior, wet semi-equatorial, dry equatorial, and 2002 the reported primary cause was weather (Ros- and wet equatorial. setti 2002). Poor visibility delayed about 14 domestic and international flights serving Beijing (December 2.2.1. Tropical interior 2011). Prominent causes of air flight delays range from This climatic region covers all three regions of north- extreme meteorological conditions and maintenance to ern Ghana and parts of the region of Brong-Ahafo. severe weather and climate (Koetse, Piet 2007). J. Evans, Of particular interest is Tamale Airport. The region S. Allan. and M. Robinson attempt to qualify the delay experiences short but heavy rainfall. Annual rainfall impact of convective weather noted that convective ranges between 1100 mm and 1250 mm. Cumulus and weather will reduce the capacity of an airport but rarely cumulonimbus are the cloud type peculiar to the re- will thunderstorms close traffic to both arrivals and de- gion. Rains become more intensive between August partures for more than 15 minutes (Evans et al. 2004). and September as the ITCZ is on its way back to the Weather is an integral component of climate. Hence, the equator. The rainfall types here are convectional, char - climatic regions within which most active airports op- acterised by massive thunderstorms, lightning, and erate must be understood well by all stakeholders (air- windstorms. This is a threat to air navigation. Lightning line operators, travellers, and air traffic management). and thunderstorms have the potential of striking down This review consists of four major sections after the in- flights at a certain flight level. For the aviation sector, troduction in section 1. Section 2 covers an overview of wind speeds are important because of their impact on the climate of Ghana. Section 3 analyses and synthesises safety. Extreme wind speed implies that aircraft are severe weather and its potential impacts on air naviga- not allowed to land at alternate aerodromes. This has tion in Ghana. Section 4 comprises conclusions and re- drastic cost implications for both airlines and travellers. commendations. 90 A-W. Moomen Air transport in Ghana: some climatic constraints Adversely, high winds imply that the departure of air- Less than 1000 mm, usually between 740 mm and craft will be delayed. Wind speeds and directions also 890  mm, of rainfall is annually recorded, however. e Th influence the use of runways and increase the probabil- effect of the harmattan is minimal. The region also ex- ity of accidents. For example, one of the largest aviation periences double maxima rainfall. But second rains accidents at Schipol Airport in the Netherlands in 1997, sometimes do occur in negligible amounts. This explains after the EL-AL Boeing catastrophe in 1992, was due why Accra is more feasible and favourable than other re- to the landing of a Transylvania plane with very strong gions in terms of navigation. Kotoka International Air- crosswinds. However, the tropical interior experiences port (KIA) is located in this region. Temperature varies single maxima rainfall, which usually starts in late April all year round, between 25 and 28°C. Relative humid- and lasts until early October. By late October, the rains ity ranges between 60 and 75%. Weather and climatic abruptly give way to the harmattan, which is accom- conditions in this region are moderate all year round, panied by wind shear stress. The dry season spans from supporting navigational activities. Thus, KIA’s location November to March. Hazy conditions become the dom- oer ff s it an advantage over all other airports in the coun- inant factors influencing air travel at this period of the try to handle landing and takeo, ex ff cept in extremely year. Relative humidity can fall as low as 20% in the dry severe cases. For example, average delays in Accra are 60 season and rise to over 80% in the rainy season. Tem- minutes for arrivals and 74 minutes for departures. peratures are quite steady in Tamale: 23°C minimum at 2.2.4. Wet equatorial/south-western equatorial night and 33°C on average during the day. This climatic region records the highest annual rainfalls 2.2.2. Wet semi-equatorial in Ghana. The region experiences showers throughout e Th wet semi-equatorial climate type covers the southern the year; of premium value in this discourse is Takoradi fringes of Brong-Ahafo, the entire Ashanti and Eastern military/public Airport. regions, and some parts of the Western Region (where Annual rainfall ranges between 1900  mm and Jasikan is located). Places of interest under this climatic 2100 mm. But due to climate change, annual rainfall in region are Sunyani Airport and Kumasi airport, both some years reaches about 2500  mm, a typical example serving domestic flights but can also serve as alternat- being the Axim area. Convectional rainfall occurs all ive aerodromes to international flights to Ghana or her over the world but especially within the tropics. It is usu- neighbours. The wet semi-equatorial region experiences ally heavy and accompanied by thunder and lightning. longer double maxima rainfall. The region sometimes Air navigational activities in this region are expected experiences convectional precipitation and other times to rise geometrically in the near future because of the experiences conventional precipitation within any of the discovery of oil and gas in commercial quantities in the two major rainy seasons in a year. No single precipita- region. Thus, conditions relating to weather and climate tion type is consistent. Convectional and conventional have come into the focus of organisations involved with rains are generally associated with thunder and light- aviation and the oil companies, as well as other symbi- ning. Such events contribute to the seasonal interrup- otic establishments. Precipitation characteristics in this tions on navigational activities in this region. It is risky region appear unfavourable to the much needed expan- to fly through convective weather conditions with their sion of air transport, especially commercial aviation. maximum accident potential. Temperatures in Takoradi area range between 21°C e Th first rains fall between April and July, whereas and 28°C, while relative humidity is approximately 80%. the second rains are oen exp ft ected between September e s Th kies above this region are generally areas where and November. The region experiences harmattan and icing takes place. In January or late December, when the its rippling effect between January and March. Hazy con- region experiences haze, visibility is impaired, making it ditions set in instantaneously, thereby resulting in flight difficult for landing or takeoff of flights. On 13 February delays and cancellations. Mean annual rainfall can exceed 2012, visibility impaired by haze did not allow commer- 1600 mm. Relative humidity is about 78% with temperat- cial flights to land at Takoradi Airport. ures around 28°C. That notwithstanding, current condi- 3. Severe weather tions are subject to changes as a result of climate change. Severe weather is the predominant cause of aviation 2.2.3. Dry equatorial accidents (Mahapatra 1999). In addition to cata- The dry equatorial region is found along the coast of strophic crashes, atmospheric turbulence originating Ghana. Major cities harbouring this type of climate are from severe weather creates discomfort and injury due Accra and Cape Coast, as well as the coastal fringes of to dislocation of cabin objects and passengers. Severe the Volta Region. The characteristics of the dry equat- weather disturbance includes thunderstorms, turbu- orial climate region are similar to those of the tropical lence, convection-induced ceiling and visibility, and interior. Aviation, 2012, 16(3): 88–95 91 in-flight icing (Kulesa 2002). The CPB has estimated track data during six thunder-storms in 1999 over the that a ‘wrongly’ configured airport like Schipol – im- Memphis, Tennessee Centre. They note that the main dif- plying that the number of hours the airport has to close ficulty with this study is the identification of deviations down is unnecessarily long–may lead to disadvantages since en route aircraft can generally avoid the storm edge for the aviation sector amounting to between 3 mil- by adjusting their course by as little as 10 to 20 degrees. lion and 1 billion euro (CPB 2002). Airlines have to Terminal area deviations require an aircraft to forfeit po- compensate passengers for delays, providing meals or sition in the landing queue and it is subsequently moved snacks or both. Flight delays at the airport of origin to the end of the queue at very busy airports like Heath- are less costly and safer for the flight operator than air - row in the UK. borne delays. Severe weather is estimated to cause 70% Convection, the upward motion of warm air that of all delays while also being an important contributory causes thunderstorms, is most prominent between June factor in 23% of all aviation accidents in the USA. Poor and July in Accra, May and June near Takoradi and Ku- visibility in the summer months and rain storms in the masi, and July and September near Sunyani and Tamale winter months lead to substantial delays and numer- in Ghana. Pilots are less likely to pass through line thun- ous cancellations (Eads et al. 2000). This alone explains derstorms since they have fewer gaps in the system and that weather is an integral component of the climate in are generally viewed as more hazardous (Jeffrey 2008). which flights navigate. o Th ugh turbulence is the primary concern for pilots, several harmful atmospheric effects may be experienced 3.1. Potential impact of severe weather on air near a thunderstorm (Mahapatra 1999). Lightning dam- navigation age can remove an aircraft from operation and result in Adverse weather conditions lead among others to an in- both loss of revenues and excess maintenance costs. It crease in the average travel time, increase in spread of is generally benign for aircraft with electrically condu- travel times, and an increased probability of accidents cive skins such as aluminium skins. The cumulonimbus (Koetse, Piet 2007). Thus, generalized costs of transport clouds that are common in Ghana contain ions that can are ae ff cted. Under severe weather conditions, people lead to the crash of a flight. consider cancelling certain trips, depending on the pur- 3.1.2. Downburst pose of the trip. A downburst is a strong downdraft which causes dam- 3.1.1. Thunderstorms/windstorms aging winds on or near the ground (National Weather A thunderstorm is a rain shower during which you Service Forecast Office, Columbia, SC). Cold air be- hear thunder. Since thunder comes from lightning, all gins to descend from the middle and upper levels of thunderstorms have lightning. A thunderstorm is clas- a thunderstorm (falling at speeds of less than 20 miles sified as ‘severe’ when it contains one or more of the an hour). A downburst is a localised area of damaging following: hail ¾  inch or greater, winds gusting in ex- winds caused by air rapidly flowing down and out of cess of 50 knots (57.5 mph), or a tornado. Worldwide, a thunderstorm (National Severe Storm Laboratory, there are an estimated 16 million thunderstorms each NSSL). Damage from downbursts can be so severe that it year. At any given moment, there are roughly 2,000 is mistaken for tornado damage. Downburst damage can thunderstorms in progress around the world (National cover hundreds of square miles or be limited to a single Oceanic and Atmospheric Administration, NOAA). field. Downburst induces haze-like conditions, thereby Windstorms make it difficult to control aircraft, espe- posing a threat to flights during landing or takeo.ff cially during landing. Underestimating wind shear and 3.1.3. Turbulence direction may mean that wrong decisions are taken on the design of airports in terms of the capacity and ori- In fluid dynamics, turbulence or turbulent flow is a entation of runaways. For instance, within the tropical flow regime characterised by chaotic and stochastic interior climate region of Ghana, rains are generally property changes. This includes low momentum dif- preceded by very strong windstorms that uproot very fusion, high momentum convection, and rapid vari- thick and large trees and damage buildings. Such winds ation of pressure and velocity in space and time. Nobel can be catastrophic for aircraft. Laureate Richard Feynman described turbulence as ‘the un Th derstorms can close airports, degrade airport most important unsolved problem of classical physics’. capacity for arriving and departing flights, and hinder Turbulence is air movement that normally cannot be or stop ground operations. Thunderstorms are a severe seen. It may occur when the sky appears to be clear weather event of great concern to aviation. D. Rhoda, and can happen unexpectedly. It can be created by any E. Kocab and M. Pawlak studies the deviations of pilots number of different conditions, including atmospheric from nominal flight routes due to weather (Rhoda et al . pressures, jet streams, mountain waves, cold or warm 2002). e Th human analysts studied 43.5 hours of flight fronts, or thunderstorms. There are several notable 92 A-W. Moomen Air transport in Ghana: some climatic constraints problems with clear air turbulence. It cannot always 3.1.5. Ceiling and visibility be foreseen, so there is no warning. It is usually felt Low ceiling and reduced visibility are safety hazards for at its mildest on the flight deck and is generally more all types of air navigation. Haze (dust-laden winds) dur- severe in the aft section. It can occur when no clouds ing harmattan and liquid water in the atmosphere (rain) are visible. Aircraft radar cannot detect it. It is common is the major causes of visibility ceiling. In the USA, stat- at high altitudes, where a cruising airliner can suddenly istics indicate that ceiling and visibility were cited as con- enter a turbulent area. Non-convective turbulence is a tributory factors in 24% of all general aviation accidents major aviation hazard. All aircraft are vulnerable to between 1989 and early 1997 (Gloria et al. 2003). Ghana turbulent motions. Non-convective turbulence can be had her own share in 2000, when an Air Force aircra ft present at any altitude and in a wide range of weather landed o ff the main runway at Kotoka International Air - conditions after occurring in relatively clear skies as port (KIA). The situation was a result the impairment clear air turbulence. The most hazardous clear air tur - of visibility caused by a heavy downpour. In Ghana, not bulence occurs in opposing motion to an aircraft. Any including KIA, at a certain visibility range only Air Force aircraft entering turbulent conditions is clearly vulner - flights can manage to land at Takoradi, Kumasi, Sunyani, able to damage; smaller aircraft are susceptible at lower or Tamale airports. Air Force flights have a light system levels of turbulent intensity than are large aircraft. Air - that aids visibility and enhances landing. Thus, commer - craft may experience jostling, which is a discomfort for cial airlines may have to delay or cancel flights because passenger and crews, to sudden accelerations that can of their visibility range policies. Depending on the size result in serious injury and temporary loss of aircra ft of aircraft, minimum visibility required before landing control. It further causes reduced flight operation and is 1800 meters. Low ceiling and poor visibility accidents delays. Turbulence is the leading cause of in-flight in- occur when pilots who are not properly rated or are y fl - juries. There are countless reports of occupants who ing an aircraft not equipped with the necessary instru- were seriously injured while moving about the passen- mentation encounter such conditions. This can result in ger cabin when clear air turbulence was encountered. loss of control or controlled flight into terrain. In 1991, the University of Illinois, USA, used simulated weather 3.1.4. Jet streams conditions to test twenty Visual Flight Rule (VFR) rated A jet stream is defined as a current of rapidly moving air pilots. When deprived of visual contact, each pilot ex- that is usually several thousand miles long and wide, but perienced loss of control. It on average took approxim- is relatively thin (Department of Atmospheric Sciences, ately 178 seconds, giving each pilot less than 3 minutes University of Illinois). They are found in the upper levels to live aer ft entering a cloud (Kulesa 2002). Low ceiling of Earth’s atmosphere at the tropopause, the boundary and poor visibility are not just safety issues. They can between the troposphere and stratosphere. Jet streams are also severely degrade the efficiency of commercial and important because they contribute to worldwide weather military aviation, reduce the capacity of an airport, and patterns and as such they help meteorologists forecast lead to airborne or ground delays that result in diver- weather based on their position. In addition, they are sion and cancellations, missed connections, and extra important to air travel because flying in or out of them operational costs. can reduce flight time and fuel consumption (NOAA). Inversely, jet streams moving in the opposite direction 3.1.6. In-flight icing to flight can lead to shortages of fuel and consequently This is the build up of ice on an aircraft during flight at flight may crash down. Thanks to research conducted altitudes above freezing. Hail (spherical or irregular pel- by pilots and meteorologists, it is understood today that lets of ice) is also a nuisance to air navigation. Sunshine there are two main jet streams, which are located in the determines the weight of wind and humidity. When it northern hemisphere. While jet streams do exist in the is sunny, the wind is light and support for aircraft lift southern hemisphere, they are strongest between the is minimal. When the temperature is low, humidity latitudes of 30°N and 60°N. The weaker subtropical jet increases, and the wind is heavy, aiding lift. But when stream is located closer to 30°N. The location of these temperatures become cold, cloud or ice formation be- jet streams shifts throughout the year however, and they comes possible. In icing situations, aircraft movement is are said to ‘follow the sun’ since they move north with ae ff cted. At altitudes where such icing occurs, ice may warm weather and south with cold weather. Jet streams build up on control surfaces, instrument orifices, pro - are also stronger in the rainy season because there is a pellers, and airspeed instrument. This alone can poten- large contrast between colliding Arctic and tropical air tially reduce airplane lift by 25%, increase drag, and lead masses. In the dry season, the temperature difference is to loss of control. In-flight icing causes approximately less extreme between the air masses and the jet stream 11% of all weather-related accidents among general avi- is weaker (NOAA). ation aircraft (Gloria et al. 2003). Aviation, 2012, 16(3): 88–95 93 3.1.7. Vegetation and birds finally a strong tailwind, representing an extreme situ- ation just prior to impact. During takeoff the pilot ex- Climate ae ff cts the vegetation of an area. e Th alternating periences a headwind and increased aircraft perform- effects of wet and dry seasons determine the life pro- ance, followed by a short period of decreased headwind, cesses of a region. During the rainy season, most grasses a downdraft, and finally a strong tailwind. and trees develop new flowers and leaves; insects gather Another finding of the study is that air turbulence around the new flowers and leaves, in turn serving as can be immensely catastrophic and hostile to air navig- prey to migrating birds such as sparrows, egrets and vul- ation. The effects of air turbulence range from jostling, tures. Thus, vegetation and forests, which are dependent loss of control, flight route deviation, stalling movement on climate, encourage bird habitation around an airport. to a crash. The biggest enemy of an aircraft is the bird, and since Moreover, in-flight icing has also been found to be aircraft cannot avoid birds during landing or takeoff, a severe weather condition that has the potential to de- disaster is bound to occur. Aircra ft that use jet propellers crease airspeed and even worse cause a flight to land pre- are especially vulnerable. If a bird flies into the propeller, maturely as it adds more weight than the capacity of the the engine will stop abruptly, leading to fatalities. Many flight. cases of accidents associated with birds have occurred in In terms of commercial use, the jet stream is im- the USA and Canada. portant for the airline industry. One of the most import- Forecast data parameters are applied to critical air- ant impacts of the jet stream though is that as a strong craft thresholds such as icing, turbulence, convection, current of rapidly moving air, it has the ability to push IFR conditions, winds, and crosswinds along a flight weather patterns around the world. As a result, most path. When critical weather thresholds are identified, the weather systems do not just sit over an area, but they are specific points are labeled to show favorable, marginal, instead moved forward with the jet stream. This phe- and unfavorable (or adverse) hazardous flight weather, nomenon hinders aircraft navigation. depending on the exceeded threshold. Thus, a tailored Since weather conditions can seriously restrict op- flight route weather effects field is created for each air - erations and levels of service available to system users, craft based on the aircra’ft s specific weather sensitivity the manner by which weather is observed and forecast thresholds (Knapp et al. 2006). and the way in which this information is disseminated 4. Conclusions and used in making air traffic management decisions must be addressed with optimal and innovative techno- The goal of the study is to inform air transport policy logy. and development planners and implementers in Ghana To estimate the impact of a convective weather sys- to create and protect safer and more efficient air trans- tem on en-route airspace, the distribution of the loca- port services in the country and also to enable them at tion and extent of the convective weather must be known all times to keep abreast of weather conditions within (FAA). It is therefore imperative to deduce from the liter- the skies of the country at all lengths and heights of ature that existing convective weather can be forecast by flight. comparing historical national convective weather for an e s Th tudy finds two major categories of climatic hour. This can only be accomplished by using convective conditions that influence air travel: short term (instant- weather detection products, which are lacking at airports aneous) and long term (seasonal). The study reveals that in Ghana, as a preventive measure against global severe ceiling and visibility are instantaneous climatic condi- weather trends hampering air transportation. tions (weather) mostly ae ff cting landing and takeoff at e m Th agnitude of aircraft delays during thunder - various origins and destinations. Ground and airborne storms and unclear weather conditions is large. Flights delays can consequently occur, adding to the operational can be re-routed through longer paths further from costs of airlines and providing immeasurable inconveni- their original flight plan instead of cancelling or delay- ence to passengers. ing. There should be a more rigorous method to define e p Th aper also finds that thunder, lightning and the area of impact of the severe weather system and the windstorms are seasonal convective weather phenom- flights that potentially could be ae ff cted. Unfortunately, ena that obstruct air navigation. These phenomena can you cannot look at a thunderstorm and see whether it is lead to loss of control by a pilot or even outright strike going to be severe. Doppler radar is able to look inside by lighting. thunderstorms and ‘see’ the movement of air, giving met- e s Th tudy finds that downbursts are dangerous to eorologists’ indications of microburst and allowing them navigation. The rapid change in wind speed and/or dir - to issue warnings to pilots. ection poses a very real threat to airplanes during takeo ff It is further learnt from the literature and reports and landing. During landings the airplane begins its des- of investigations that the use of integrated approaches cent, flying into a strong headwind, a downdraft, and 94 A-W. Moomen Air transport in Ghana: some climatic constraints to provide improved guidance of convective weather (GNSS). GNSS comprises all forms of satellite-based hazards for transoceanic flights could help mitigate navigation systems that provide global coverage and sig- potential hazards. The Ghana Civil Aviation Authority nals for navigation, positioning surveillance, and tim- (GCAA), together with other stakeholders, should de- ing information for aviation and space applications. The velop advanced concepts of using weather forecast mod- GNSS comprises three categories: GNSS-1, GNSS-2 and els to create probabilistic weather-related impact predic- GNSS-3. Ghana is under the GNSS-3 category, countries tions for today’s consumption by air-traffic management without the capacity or necessary infrastructure to de- planning in Ghana. This could necessarily be incorpor - ploy satellites but which have or seek to develop local ated into largely automated decision-support tools in the systems to explore the full potential of the global sys- near future. tems. GNSS signals integrated with additional informa- Today, movement of the jet stream north has tion layers enable air navigation and flight tracking. e Th been detected, indicating possible changes in climate. system includes waypoints as well as precise navigation Whatever the position of the jet stream though, it has collision avoidance, cargo monitoring, and search and a significant impact on the world’s weather patterns rescue operations. The European Global Navigational and severe weather events like floods and droughts. It is Operating System (EGNOS), which also is an aspect of therefore essential that meteorologists and other scient- GNSS-2, helps national, intercontinental, continental ists understand as much as possible about the jet stream flights identify alternate aerodromes whiles in-flight. and continue to track its movement, to in turn monitor EGNOS directly provides flight height reduction in angle such weather around Ghana. A detailed assessment of of approach (direct and curved), better lateral guidance, the primary and supplementary sensor network for each optimised routes and fewer diversions, increased airport of the major airports in Ghana should be conducted. capacity (for example, helicopters); allows operation in KIA is the only airport in Ghana that has an instrument non–ILS equipped airports; avoids expensive land-based landing system (ILS), which permits landing even dur- navigational aids and their maintenance; and above all ing severe weather. increases safety. When extreme weather and climate Worth acknowledging is the idea acquired from the conditions eventually lead to accidents and tragedies in literature reviewed that Ghana Airspace Management Ghana’s airspace, both passengers and freight transport needs to develop strategies and products for forecasting will suffer. The negative economic repercussions that the potential for icing. Such a tool or mechanism will may arise as a result might be incalculable. People want enable users to better anticipate where icing hazards are to travel and need to travel; we should therefore make likely to occur. It will further allow air traffic controllers it possible for each and every one of us now and in the to make more informed decisions when assigning alti- future. tudes to aircrafts. References Furthermore, an algorithm that can help forecast CPB. 2002. Gevolgen van uitbreiding schipol [Consequences turbulence is vital in Ghana’s airspace navigation. The al- of extension of schipol airport]. 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Published: Oct 2, 2012

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