Temporal And Spatial Characteristics Of The Wind Field In The West Pacific Warm Pool And Its Impact On The Fog In South China

This paper uses monthly mean SST temperature of NOAA satellite to define the Warm Pool area.Based on monthly averaged data of ECMWF wind field,the four levels(1000hPa,925 hPa,850hPa and 500hPa)over the west Pacific warm pool over 444 months from January 1979 to December 2015 are analyzed.The seasonal,interannual and interdecadal variations of 1000 hPa,925hPa,850 hPa and 500 hPa wind fields over the WSPH are analyzed by empirical orthogonal functional decomposition(EOF),power spectrum analysis and one-dimensional linear regression.At the same time,the seasonal variation and interannual variation of the fog days in South China during 1979 ~ 2015 were analyzed by using the fog days data provided by the National Climate Information Center.The correlation analysis was also used to study the South China region,and draw the following conclusions:(1)Western Pacific Warm Pool wind there seasonal variation characteristics: the Western Pacific Warm Pool 1000 hPa layer northeast monsoon prevails in winter,wind speed,summer easterly winds prevailing southeast wind speed is small.(2)There is a significant one-to-three-year period variation of the 925 hPa wind anomaly field in the Warm Pool of the Warm-Warm Pool.The 850 hPa wind anomaly field has a nine years and eighteen years interdecadal variation;the 500 hPa wind anomaly field has a significant one to two years of annual cycle,and twelve years and eighteen years of inter-decadal cycle characteristics.(3)In summer,the number of fog days decreased in the summer,and the maximum fog days were only about sixty days in summer,and some areas were not The maximum number of fog days is one hundred and fifty days,which is the largest in the eastern part of Guangdong.In winter,fog days are the largest in four seasons and the maximum is two hundred days.(4)The winter fog days in South China show a unimodal structure.During the twenty years between the 1880 s and the early 2000 s,the winter fog days in South China did not increase or decrease,but they increased at the beginning of the 21 st century and reached the maximum.The number of winter fog days in South China declined gradually after 2010,and the spring fog days in South China showed two bimodal structures,which had a very high value in the early 1980 s and then gradually declined,but in the early 20 th century,The number of fog days increased significantly in spring,after the spring of 2010,fog days and gradually smaller.The fog days in South China have a tendency to decrease gradually,and the annual average fog days distribution is very uneven.The fog days in Guangdongare obviously larger than those in Guangxi.(5)The results show that the number of foggy days in South China is closely related to the change of winter monsoon and subtropical high intensity in the Wentai warm pool.The summer subtropical high index is closely related to the westerly warm pool in winter And the winter wind anomaly of the west Pacific warm pool is weakened(enhanced).The500 hPa winter monsoon in the west Pacific warm pool is positively correlated with the winter fog days in South China during the same period.When the winter monsoon of500 hPa in the warm pool increased,the fog days in South China increased.When the subtropical high became stronger(weakened),the fog days in South China increased more(decreased)in the following spring.