福建省2018年3—6月干旱环流的变化特征

利用福建省66个气象站逐日降水资料、NCEP/NCAR再分析资料和NOAA逐日OLR资料,分析福建省2018年3—6月干旱事件的大尺度环流及其变化特征。结果表明:福建省2018年3—6月降水均偏少,暴雨日偏少,持续性暴雨过程弱,导致严重气象干旱。受拉尼娜的滞后影响,福建处在下沉气流中心,阻塞高压偏弱,西太平洋副热带高压较常年偏弱、偏南、偏东,福建处于水汽通量辐散异常中心区,这是造成福建该时段干旱的环流背景。环流变化显示,前期的阻塞高压、副热带高压和热带对流北传均不活跃,导致暴雨日偏少,干旱发展;后期环流呈现阶段性振荡特征,南北系统的有效配合为持续性暴雨发生提供了有利的环流条件,干旱得以缓解。

Variation characteristics of drought circulation in Fujian Province from March to June 2018

Based on the daily precipitation data of 66 meteorological stations in Fujian Province, NCEP/NCAR reanalysis data and NOAA daily OLR data, the large-scale circulation characteristics and it’s variation of drought events in Fujian Province from March to June 2018 were analyzed. The results show that less precipitation in every month, less rainstorm days and weakness of persistent rainstorm process led to severe meteorological drought in Fujian Province from March to June 2018. Affected by the La Ni1 a event, Fujian was in the center of downdraft. The blocking highs were weaker, the West Pacific subtropical high was weaker and moving to the south and the east than usual, Fujian Province was in the anomalous center of water vapor flux divergence, which was the circulation background of drought. The variation of circulation showed that the blocking highs, the subtropical high and the northward propagation of tropical convection were not active in the earlier period, leading to less rainstorm days and drought development. In the later period, the circulation presented the characteristics of periodic oscillation, and the effective cooperation of the north and south system provided favorable circulation conditions for occurrence of persistent rainstorm, which alleviated the drought.