摘要
利用1958—2012年海河流域30个气象站月降水资料、NCEP/NCAR月平均再分析资料及1974—2012年月平均向外长波辐射资料,分析了海河流域盛汛期旱涝急转事件及其与大气环流异常的关系。结果表明,南亚高压和西太平洋副高在盛汛期的月际振荡是海河流域旱涝急转形成的一个重要原因。涝转旱年及旱转涝年涝期对应于"西低东高"的流型(海河流域上游为低槽区,下游为高压区),冷暖空气活跃且易于较长时间在流域交绥,低层水汽输送较强且有正涡度异常,高层辐散和上升运动偏强,流域多雨偏涝;旱期则对应于"西高东低"的流型,西风带环流较为平直,低层有负涡度异常且水汽输送偏弱,高层辐散和上升运动偏弱,海河流域因而少雨偏旱。海河流域旱急转涝(涝急转旱)事件易发生在南亚夏季风偏弱(强)的背景下。海河流域盛汛期旱涝急转与初汛期流域上空气压场强度以及北太平洋涛动(NPO)、南半球环状模(SAM)存在显著的正相关,上述因子可能是旱涝急转事件的前期信号。
Based on monthly rainfall data of 30 meteorological stations in Haihe River Basin （HRB） and NCEP/NCAR monthly reanalysis data in the years of 1958-2012, and outgoing long-wave radiation data for the period of 1974-2012, the drought-flood abrupt alternation （DFAA） events over HRB and their relationships with the anomalous atmospheric circulation in main rainy season （MRS） are analyzed. The results show that the inter-monthly oscillation of western Pacific subtropical high and South Asia high in MRS is an important factor that leads to the DFAA over HRB. The flood-period in the years of sharp turn from flood to drought （ST-FTD） and sharp turn from drought to flood （ST-DTF） corresponds to the pattern of ＂west-low-east-high＂ （ HRB＇s up- stream is low trough areas and its downstream belongs to high pressure regions）, the active cold and warm air mass easily converges in HRB for a longer period and there exist strong moisture transport and anomalous posi- tive vorticity in the low level. Divergence in the high level and ascending movement are strong. The above-mentioned factors result in significant more precipitation over HRB. The drought-period belongs to the pattern of ＂west-high-east-low＂, the circulation in westerly belt is straighter, and there are anomalous negative vorticity and weak moisture transport in the low level. The divergence in the high level and descending movement are weak. The previous situations facilitate less rainfall over HRB. Events of ST-DTF （ST-FTD） may easily occur in the background of weak （strong） South Asian summer monsoon. Additionally, the DFAA over HRB in MRS is remarkably positively correlated with the pressure intensities over HRB, North Pacific oscillation and Southern Hemisphere annual mode in the preceding June, which offers some possible previous signals for the DFAA events over HRB.
出处
《热带气象学报》
CSCD
北大核心
2016年第4期515-523,共9页
Journal of Tropical Meteorology
基金
中国气象局气象关键技术集成与应用项目(CMAGJ2015M03)
中国气象局气象关键技术集成与应用项目(CMAGJ2014M05)
中国气象局预报员专项项目(CMAYBY2014-004)
天津市气象局科研项目(201513)共同资助
关键词
海河流域
盛汛期
旱涝急转
大气环流异常
Haihe River Basin
MRS
DFAA
anomalous atmospheric circulation
