By using the conventional meteorological data, NCEP/NCAR 1°×1° and 2.5°×2.5° global reanalysis data, the influence systems and circulation evolution characteristics from long-term drought to rainstorm in May 2011 of Henan were analyzed. The results show that the rainstorm generated in a strong low-level convergence zone where it is in front of the upper trough, the south side of the low- level shear line and the left side of the export of low-level jet. Comparing and analyzing the large-scale circulation field during periods of drought and rainstorm, we found that the 500 hPa height field main- tained a long-term ＂west higher and east lower＂ circulation pattern during the drought period but the cir- culation adjusted to ＂east higher and west lower＂ quickly during the rainstorm period. The height anoma- lies and negative anomalies interchanged from drought period to rainstorm period both in upstream and downstream. The westerly jet and the main body of South Asia high were in the south during period of drought but they both moved to the north rapidly during the rainstorm period, and the rainstorm areas were just at the strong high-ahitude divergence areas where they joined each other. AO index and the NAO index were positive during period of drought. When they are negative value from positive value suc- cessively, it may indicate the rainstorm will occur later.
from long-term drought to rainstorminfluence systemcirculation evolution character- isticsindex feature
NETL
NSTL
维普
万方数据
