辽宁省夏季典型旱涝年降水低频特征分析

Characteristics of low-frequency of summer rainfall in typical flood and drought years over Liaoning province

利用1962—2013年NCEP/NCAR逐日再分析资料和辽宁省53个气象站逐日降水资料,分析辽宁省夏季典型旱涝年降水低频的特征。结果表明:1962—2013年辽宁省夏季旱年降水的30—60 d振荡显著,涝年低频振荡不显著,以小于10 d的高频振荡为主。旱涝年低频涡度和散度的传播方向明显不同。辽宁省夏季干旱的发生与低频涡度和散度自低纬度北传及中高纬度南传并同位相汇合于辽宁地区有关,高低层低频涡度和散度在动力上表现出协调一致性。小于10 d高频振荡的累积效应使辽宁地区夏季易发生洪涝,30—60 d振荡叠加高频过程,易使辽宁地区夏季发生干旱。

Based on the NCEP/NCAR daily reanalysis data and daily rainfall data at 53 weather stations in Liaon- ing province from 1962 to 2013, characteristics of low-frequency of summer rainfall in typical flood and drought years were analyzed using a composite analysis method. The results indicate that there is a significant 30-60 days cycle for summer precipitation in drought years from 1962 to 2013 in Liaoning province, while low-frequency os- cillation is not significant and high-frequency less than 10 days is dominant in flood years. Transport directions of low-frequency vorticity and divergence in flood and drought years are different. Summer drought occurrence in Li- aoning province is associated with convergence of the northward propagation of low-frequency vorticity and diver- gence over low latitudes and southward propagation from mid-high latitudes. Low-frequency vorticity and diver- gence both are consistent in relationship with dynamic field. The cumulative effect of high-frequency oscillation less than 10 days leads to more flood events in summer,while 30-60 days Oscillation superimposed on high-fre- quency process is easy to generate drought events.