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doi: 10.1002/qj.49707632902pmid: N/A
A consideration of the parameters best suited to characterising a circular vortex leads to the conclusion that an intensity factor, the central pressure defect (or excess) and a scale, or size factor are fundamental.
doi: 10.1002/qj.49707632903pmid: N/A
The paper gives an account of variations in thunderstorm severity in Great Britain based on statistics of breakdowns caused by lightning on the Grid system during the 14‐year period 1934 ‐ 1947. Data are given for the seasonal and diurnal variations and for the fluctuations from year to year. The breakdown data are compared with the corresponding statistics of thunderstorm‐days, and it is shown that the thunderstorm‐day observations, if used directly, do not give an adequate indication of storm severity. It is proposed to introduce a “severity index” (s) such that the severity is proportional to Ts, where T is the number of thunderstorm‐days. For the data examined, s has values of 1.4 and 1.9.
doi: 10.1002/qj.49707632904pmid: N/A
A previous observational study (Pasquill 1949 a) has been supplemented by further measurements of evaporation and the associated vertical profiles of wind velocity and vapour pressure in the first two metres above a clayland pasture with grass of moderate length, mainly in effectively adiabatic conditions of flow. The evaporation measurements, using a simple form of soil evaporimeter, included two series of statistically designed measurements, in order further to examine the “reliability” of the technique. The data so obtained, though not comprehensive, indicate no substantial error due to the necessary isolation of test soil from underlying layers, but there is a suggestion that the rates of evaporation ultimately adopted might be underestimates, owing to unavoidable disturbance of root and soil continuity in the vertical at the perimeters of the soil cores contained in the evaporimeters.
doi: 10.1002/qj.49707632905pmid: N/A
From a consideration of experimental measurements of the terminal velocity of water drops and of the drag coefficient of rigid spheres it is suggested that a formula of the type V = A exp bz { 1 – exp [– (d/a)n]} may be used to represent the terminal velocity of water drops which are larger than those to which Stokes's law is applicable and which are falling through a standard atmosphere. If V (the terminal velocity) is measured in cm/sec, z (the height) in km and d (the drop diameter) in mm the values of the constants are as follows:— I.C.A.N. atmosphere Summer tropical atmosphere Range of d mm A b a n A b a n 0.3 to 6.0 932 0.0405 1.77 1.147 958 0.0354 1.77 1.147 0.05 to 0.3 191 0.0290 0.316 1.754 188 0.0256 0.304 1.819 If the drops have diameter less than 0.05 mm, Stokes's law is applicable and V = A d2 exp bz where A is 3040 and 2840 in the I.C.A.N. and S.T. atmospheres respectively and b has the values 0.0191 and 0.0172 in these two atmospheres.
doi: 10.1002/qj.49707632906pmid: N/A
Evidence is produced to support the belief that temperatures at the tops of weather echoes are an indication of the relative strengths of the vertical currents within the echoes. Two types of weather echo are indicated according as the vertical currents are strong or weak, giving support to a theory for two different methods for the production of water drops of raindrop size in the atmosphere.
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