汉江流域秋汛期典型旱涝年与前期海温的关系研究

Study on the relationship between typical drought/flood years in autumn flood season in Hanjiang River basin and preceding sea surface temperature

利用汉江流域16个气象观测台站1961—2010年秋汛期(9—10月)逐候降水资料,计算了降水集中度(PCD)和集中期(PCP),并建立了相应的序列,结合秋汛期降水距平百分率,确定汉江流域秋汛期典型旱涝年。同时,利用美国国家环境预测中心及国家大气研究中心(NCEP/NCAR)提供的同期海温和500 hPa高度场资料,采用合成和相关分析方法,探讨了典型旱涝年与前期海温的关系。结果表明,印度洋、赤道中太平洋、北太平洋为3个海温关键区,当这3个海区海温发生异常时,影响汉江流域秋雨的主要系统(印缅槽、贝湖槽、东西伯利亚高压和乌拉尔山高压)也相应发生变化,从而导致PCD和降雨量异常,引发汉江流域洪涝或干旱灾害。在一定程度上,可将前期海温异常作为判断汉江流域秋汛期降水量多少及PCD强弱的前兆信号。

Based on pentad precipitation data from 16 meteorological observing stations in Hanjiang River Basin in the autumn flood season from September to October during 1961-2010, this paper has calculated the precipitation concentration degree （PCD） and precipitation concentration period （PCP）. Combined with time series of PCD and precipitation anomalous percentage in the autumn flood season, typical drought/flood years were determined. Meanwhile, using sea surface temperature （SST） and 500 hPa height field data from NCEP/NCAR in the same period, the relationship between these typical years and SST was discussed by composite and correlation analysis method. The results show that there are three SST key areas located in Indian Ocean, equatorial middle Pacific and North Pacific respectively. When the SST in these sea areas show anomaly, the main synoptic systems, including India-Burma trough, Baikal trough, East Siberia high and Ural Mountains high, influencing autumn rainfall in Hanjiang River Basin change accordingly, which lead to anormaly of PCD and rainfall, and then initiate drought and flood disaster in Hanjiang River Basin. Anomaly of preceding SST in the three key sea areas can be regarded as a precursor signal to judge the amount of precipitation and the strength of PCD in the autumn flood season in Hanjiang River Basin to a certain extent.