2015年广东开汛前后旱涝急转特征及成因分析

ANALYSIS OF THE ABRUPT ALTERNATION FROM DROUGHT TO FLOOD AROUND THE ONSET OF RAINY SEASON IN GUANGDONG IN 2015

利用1961—2015年广东86站3—5月逐日降水资料、NCEP/NCAR再分析资料及NOAA的Hysplit后向轨迹模式资料和海温资料,分析了2015年广东开汛前后旱涝异常特征,旱涝急转前后的大气环流和水汽条件转变及成因。(1)2015年5月第1候广东发生了严重的旱涝急转事件,旱涝急转前全省严重干旱,旱涝急转后广东大部地区降水异常偏多。(2)旱涝急转前后,500 hPa中高纬度由"两槽两脊"转为"两脊一槽"和"两槽一脊",副高持续加强,广东地区高层辐散和低层辐合加强,地面由冷空气控制广东转为冷暖空气在广东交汇;水汽输送通道由北部湾和长江中下游地区转为南海南部和中南半岛南部海面,广东低层水汽净流入增加。(3)黑潮区、北太平洋中部、Nino3、Nino4区及印度洋和南海的海温异常增暖造成了旱涝急转前后大气环流和水汽的转变。

Based on the daily precipitation data from 86 stations in Guangdong Province during MarchMay from 1961 to 2015,NCEP/NCAR reanalysis data,NOAA Hysplit backward trajectory model data and SST data,the present study analyzed the characteristics and the cause of an abrupt alternation from drought to flood around the onset of rainy season in 2015.The results showed that:(1)Serious abrupt alternation from drought to flood occurred in Guangdong in the first pentad of May,2015.Severe drought in the whole province was found before the alternation,but after that,abnormally high precipitation occurred in most areas of Guangdong.(2)Before and after the abrupt alternation,the circulation pattern in the middle-high latitudes at 500 hPa changed from“2-trough and 2-ridge”to“2-ridge and 1-trough”and“2-trough and 1-ridge”pattern.The Western Pacific Subtropical High continued to strengthen,so did the upper level divergence and lower level convergence in Guangdong.On the surface,Guangdong was controlled by cold air before the alternation,and then warm air strengthened and meet the cold air there.The water vapor transport channel changed from the Beibu Gulf and the middle-lower reaches of the Yangtze River to the southern parts of South China Sea(SCS)and Indochina Peninsula,and the net inflow in the low level in Guangdong increased.(3)The anomalous warming of SST in Kuroshio,the central part of North Pacific,Nino3 and Nino4,Indian Ocean and SCS resulted in the variations of atmospheric circulation and water vapor before and after the abrupt alternation.