In China these depressions develop most of the time over the Southwestern provinces and move East oF ONE-ward, Many times they are not really formed depressions until they each the sea, owing to the orographic influence of the regions they must cross, Sometimes they are more clearly defined and a position of the centre can be given as certain, some Where over Kiangs! or even Szechuer Me. rain. in these extra-trepleai cyclones fs formed as drizzle just before the line of discontinuity dividing {he warm sector from the gold sector.
10 rain belonging to this type of dis turbance becomes heavier and. sho-
\wory as soon as the cold sector (so times two cold fronts) invade the To try to check the location of these two sectors. (warm and cold) by the temperatures at the surface is openly ejected by all the leading meteorolo-Hlsts of the world. Only upper air ridings, as they are done elsewhere China, can show these two sectors with fair certainty, Tu the southwest part of these pressions just before the showery type thoro fs frequently a short duration of thundery rain, '$0 much that for alreratt it ts safer fo pass a depression centre flying through the North part fof it as they will avoid these dan-porous ups and downs duo to the thundery clouds.
This explains how even In Shoughal in winter we get thunderstorms. some-{imes quite vivid, although short rived. Nevertheless these thunderstorms fol-tow the depression-contr al! atong ts track, The other type of eyclonine rain Is caused by the tropteal cyclone, Momogencous Tropleal Alr This rain Is of the showery type and fat Mest is intermittent, squally and as the contre gets nearer, the squalls are more frequent and the rain heavier. There seems to be a period of five to eight seconds in the successives showers, as in this case the rain makes the wind. The typhoon core being homogeneous tropical trade alr (at least at the surface and most probably also to about 2,000 metres), the dis tribution of rain is almost lhomogenerous all round the cyclone.
Thundery showers are absent; they are present only In the outskirts of the typhoon and so do not belong to the thermodynamics of this kind of atmospheric disturbance. Only when (typhoon Is decreasing and filing up, fs there a thundery display, as then another type of air stream is mixing, with the former homogeneous trade alr core.
The quantity of rain to be expected with a depression centre can reach 50 millimetre in 24 hours. With a typhoon 400 to even 00 millimetre can be reckoned with, In the same 24 hour interval. Another difference with the depression is that a typhoon Alls up when crossing the continent; then the heaviest rain downpours are registered and this deluge can last several days flooding the district
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