Study on the Climatic Characteristics of the Quasi-stationary Front in Yunnan and Guizhou and its Frontal Rainfall in Winter in Guizhou

The quasi-stationary front in Yunnan and Guizhou is one of the most important weather systems in Guizhou in winter， and it is difficult to forecast.This paper analyzes the winter climate characteristics of the quasi-stationary front in Yunnan and Guizhou and frontal rainfall characteristics of different magnitudes in Guizhou by using the daily ground conventional observation station data of five provinces （cities， districts） of Yunnan， Guizhou， Sichuan， Chongqing， Guangxi from 2007 to 2021 and the daily precipitation data of Guizhou from 08:00 to 08:00.The results show that： （1） There are 52.8 days of the quasi-stationary front weather in Guizhou in winter on average.The impact of the quasi-stationary front is most serious in January， followed by February and December.（2） In winter， the front direction of the quasi-stationary front in Yunnan and Guizhou is the most south-north type， averaging near Qujing； The second is the northwest southeast type， which is located in the west of Guizhou on average； There are few east-west types； The moderate intensity quasi-stationary front is the most and tends to occur in the early winter， the strong quasi-stationary front is the second and tends to occur in the late winter， and the weak quasi-stationary front is the least.（3） The frontal precipitation is dominated by rainfall （rain or freezing rain）.The stronger the quasi-stationary front is， the fewer the days of frontal precipitation are， and the proportion of the days of frontal precipitation increases with the weakening of the quasi-stationary front； The frontal rainfall is mainly concentrated below 5.0 mm， and the frontal rainfall probability is inversely proportional to the rainfall and is proportional to the rainfall range.When the frontal rainfall is weak， the frontal rainfall probability is unimodal with the increase of rainfall and bimodal with the expansion of rainfall range.（4） The results of EOF and REOF classification show that there are two types of frontal precipitation with different magnitudes that affect Guizhou： the frontal precipitation in the central and eastern regions is mostly in the early winter and more south-north， with moderate or weak intensity and prone to large-scale rainfall of 0.1~1.0 mm magnitude； The southwest type frontal rainfall is mostly in the late winter， and it is mostly north-south type or north-west southeast type.The intensity is strong， and the small-scale rainfall of 1.1~5.0 mm is easy to occur.（5） The climate tendency rate of the average annual rainfall in the middle-east type is negative， and the cumulative anomaly changes are roughly in the "M" shape； The climate tendency rate of annual average rainfall in the southwest type is positive， with obvious stage characteristics， and the cumulative anomaly changes are roughly "W" shaped； Both of them have quasi 4 years and quasi 8 years periodic oscillations； In recent years， the frontal rainfall in the middle-east has decreased， while that in the southwest has increased.The results can provide an important climate background for the prediction of quasi - stationary front weather in winter in Guizhou.