| Based on the observation and reanalysis data from 1979 to 2014,using the atmospheric moist static energy < MSE > diagnostic equation,this paper mainly studies the characteristics of atmospheric unstable energy before and after the occurrence of extreme precipitation in the pre and post flood season in South China from the perspective of atmospheric energy.On this basis,it further reveals the influence of the tropical Indian Ocean and tropical Pacific sea surface temperature anomalies on the extreme precipitation in the pre and post flood season in South China The influence mechanism of water.The main conclusions are as follows:(1)The correlation between the total amount of extreme precipitation and time series in the pre flood season and post flood season in South China is low or even negative,and the correlation coefficient is-0.34.In this paper,we use the extreme precipitation index,including the total amount and frequency of extreme precipitation.The extreme precipitation index of South China has obvious interannual variation and upward trend.The frequency of extreme precipitation in the first flood season has a period of 4-8 years,and that in the later flood season has a period of 2-6 years.The significant periods of both are mainly after the1990 s.The spatial distribution of extreme precipitation index in South China is quite different between the pre flood season and the post flood season.The pre flood season is mainly distributed in Guangdong,Guangxi,the junction of Fujian and Jiangxi,and the southern coastal area,while the post flood season is mainly in the southern coastal area of Guangxi and Guangdong.(2)Similar to the tropical intraseasonal oscillation(ISO),the atmospheric wet static energy < MSE > is charged and released before and after the extreme precipitation events in the pre flood season and post flood season in South China,and the < MSE > reaches its peak one day earlier than the extreme precipitation.Before the occurrence of extreme precipitation,South China is controlled by the anomaly of cyclonic circulation,whose southwest wind anomaly brings tropical warm and humid water vapor into South China,resulting in the increase of < MSE > horizontal advection and atmospheric charging in South China;during the occurrence of extreme precipitation,the abnormal upward movement transports the relatively small climate MSE in the lower layer to the upper layer,resulting in the decrease of MSE in the whole layer and atmospheric energy release.(3)On the interannual scale,when the total amount of extreme precipitation in the first flood season of South China is more than normal,there is an anticyclone circulation anomaly in the Northwest Pacific when the extreme precipitation in the first flood season of South China increases.The anticyclone is excited by the iobm of the tropical Indian Ocean,which helps to increase the water vapor input in the southern boundary of South China and increase the anomaly of < MSE > in South China;in the year when the total amount of extreme precipitation in the later flood season is more than normal,there is an anticyclone circulation anomaly in the Northwest Pacific There is cyclonic circulation anomaly in the stratosphere,which is northward than the anticyclone anomaly in the previous flood season.The Northeast air flow in the northwest direction helps to reduce the water vapor outflow from the north boundary of South China and increase the < MSE > anomaly in South China.The cyclone is affected by ENSO in the development stage.The cold sea temperature near the oceanic continent and the warm sea temperature in the equatorial central Pacific can stimulate the Matsuno gill response and produce a cyclone in the Northwest Pacific The abnormal circulation was observed.The Indian Ocean warm sea surface temperature and the Pacific dipole sea surface temperature affect the summer extreme precipitation in South China by adjusting the < MSE > on the interannual scale before and after the flood season in South China. |
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