贵州和四川盆地是我国云量最多的地区,素有“天无三日晴”和“蜀犬吠日”之说,盆地西缘的雅安古时还有“雅州天漏”的谚语。从全球日照百分率分布推知,川黔地区也是世界上天气最阴沉的地区之一。

It is always said that: "There arn’t three clear days" in Guizhou, and "Sichuan’s dog barks at the sun". In this article, the data of all stations with 30 years(1951 - 1980) in this areas are used, the main results are as follows:1. In these areas, mean annual total cloud amount reaches 8.0 - 8.9, and low-level cloud amount is about 5 - 7.The radio of low-level cloud amount to total cloud cover is 50 - 70% over Sichuan basin and 70 - 90% over Guizhou plateau.2. In the cloudest areas, the continuous clear sky for five days never occured in past 30 years.3. The curve of annual total cloud amounthave two peaks and two lows, but only one peak and one low in low-level cloud amount. The investigated area not only has much cloud amount, but also has different pattern of annual change of cloud amount than surounding areas.4. In four regular observations there are more cloud amount in early morning (08 h), and least amount the evening (20 h) usually.5. The standard deviation of mean annaul total cloud amount is about 0.15 - 0.25,one-tenth in these investigate areas but it is rather different for low cloud amount.6. The common cloud form over Sichuan basin and Guizhou plateau is low-level cloud,, and in which the commonest is the Stratocumulus(Sc).For example, in January the ratio of the times of the appearence of Sc to all low-level cloud are about 57.7 - 72.1%.Bat from winter to summer, the frequency of Sc reduces and Cu increases.7. The commonest height of cloud base of Sc is between 1000 - 2500 m.The height of Sc are 520 m higher over Sichuan basin than over Guizhou plateau.The height of Sc is higher in Summer and lower in Winter, and higher in 14 h than in 02 h.