On the Relation between Various Meteorological Elements and Diurnal Variation of Cloud Amount

[摘要] The author studied the relation between diurnal variation of cloud amount in Japan and various meteorological elements, such as, daily mean humidity, daily mean lapse rate of lower atmosphere, daily mean wind speed, daily most frequent wind direction, and daily change of pressure. Thus he found the following types.a) After passage of a trough and when the air is dry:- one maximum of cloud amount in the afternoon.b) After passage of a trough:- main maximum in evening and secondary maximums at just before noon and midnight, and distinct minimum in early morning.c) When wind force is very weak:- similar as above, but a very sharp maximum at midnight.d) Northerly or northeasterly winds:- two maximums in morning and afternoon.e) Southerly or southeasterly:- maximum in morning and minimum in evening, hence a typical morning overcast occurs.f) Low approaching:- similar as above, but one maximum before noon and minimum in night time.g) Wind force strong:- four maximums at about 6h, 12h, 18h and 24h, hence cloud amount is variable.h) Stratus or fogs:- minimum in day time and maximum at night.

[学科分类] 大气科学