1960-2016年广东冬季降水变化特征及成因

Characteristics of Winter Precipitation Evolution and Its Causes in Guangdong from 1960 to 2016

【目的】探究大气环流与热带太平洋海温异常(尤其是ENSO事件)对广东省冬季降水的影响,揭示降水变化的物理机制。【方法】利用1960年12月-2017年2月广东省地面常规观测资料、NCEP/NCAR再分析资料,运用相关分析和合成分析方法,探讨广东省冬季降水时空变化特征,分析降水变化的原因。【结果与结论】1)广东冬季降水自南向北递增,高值中心在粤北地区,近57 a降水总量呈不显著的增加趋势(4.25 mm/10a,P=0.58),降水强度显著增加(0.48(mm/d)/10a,P<0.01),降雨日数在显著减少(-1.19 d/10a,P<0.05)。2)广东冬季降水偏多时,我国大部分地区气压偏高,近地面冷高压活动频繁;500 hPa位势高度场上,中高纬度亚欧大陆自东向西出现“+-+”型相关分布,乌拉尔山附近阻塞高压偏弱,冷空气易南下影响我国,南支槽偏强,西太平洋副热带高压偏强,有利于向广东地区输送水汽。3)广东冬季降水与热带太平洋海温异常也存在密切联系,冬季降水与同期海表温差(SSTA)相关场呈类似厄尔尼诺年的SSTA分布。而厄尔尼诺年广东恰处于西太平洋副热带高压西北角,受西南气流控制,且850 hPa来自南海与孟加拉湾的水汽在广东上空辐合,造成降水偏多。而拉尼娜年副热带高压强度偏弱,位置偏东,南海上空受气旋性环流控制,广东地区以干冷东北偏东风为主,较难形成降雨。

【Objective】To explore the impact of atmospheric circulation and tropical Pacific sea temperature anomalies(especially ENSO events)on winter precipitation in Guangdong Province,and reveal the physical mechanism of precipitation changes.【Methods】Using conventional ground observation data of Guangdong Province along the coast of South China from 1960 to 2017 and the NCEP/NCAR re-analysis data,the temporal and spatial changes of winter precipitation in south China coastal area were explored and the possible causes of the precipitation changes were analyzed through the use of correlation analysis and synthetic analysis.【Results and Conclusions】(1)The winter precipitation in Guangdong increases from south to north,and the high value center is in northern Guangdong.The total precipitation in the past 57 years has shown an insignificant increase trend(4.25 mm/10a,P=0.58),and the precipitation intensity has increased significantly[0.48(mm/d)/10a,P<0.01],the number of rainy days is significantly reduced(-1.19 d/10a,P<0.05).(2)When there is more winter precipitation in Guangdong Province,the pressure is higher in most areas in China and the cold high pressure activity near the ground is frequent.The Eurasian continent in the mid-high latitudes shows a“+-+”type correlation distribution from east to west on the 500 hPa geopotential height field,and the high blocking near the Ural Mountain is weak,causing the cold airwave move south readily to influence China;the southern branch trough and the subtropical high over the Western Pacific(WPSH)are relatively strong,which was conducive to transporting water vapor to Guangdong Province.(3)The correlation between winter precipitation and SSTA in the same period is similar to the El Niño-like SSTA distribution.During El Niño years,Guangdong Province was at the northwest corner of the WPSH,controlled by the south westerly airflow,and the water vapor from the South China Sea and the Bay of Bengal converged over Guangdong Province on the 850 hPa geopotential height field,resulting in more precipitation.However,in La Niña years,the intensity of WPSH is weaker to the east,and there is a cyclonic circulation over the South China Sea.Therefore,Guangdong Province is dominated by dry and cold northeast easterly winds,making it difficult to form rainfall.