近60年洪泽湖流域汛期降水特征及其与EASM关系

Precipitation Change in Flood Season and Its Relationship with EASM in the Hongze Lake Catchments in Recent 60 Years

洪泽湖流域近60 a来汛期降水的综合分析表明,汛期降水呈现总体增加的趋势,且未来仍呈增加趋势。汛期降水在2000年出现突变,此后呈现明显增加特征,是2000年来洪涝频繁的主要因素。SPI旱涝等级显示,旱涝以1960 s波动最为显著,而2000 s以来SPI值明显偏高。汛期降水与东亚夏季风(EASM)指数存在6 a左右和准2 a的共振周期。在1960～1972年间的6 a左右共振周期上,EASM越强,降水越少;而在1986～1992年的6 a左右共振周期上,EASM与汛期降水呈较弱正相关。1996～2004年间准2 a左右的共振周期上,EASM与汛期降水呈反相关系。

The methods of anomaly analysis, Mann-Kendall analysis, Rescaled Range Analysis, Standardized Precipitation Index and the wavelet analysis are applied t to detect the characteristics of the precipitation in flood season in the Hongze Lake catchments. Result shows that the precipitation in flood season undergoes an insignificant upward trend in the recent 60 years, and it would continue to be an increasing trend in the near fu- ture. Abrupt change of precipitation in flood season occurred in 2000 and it increased greatly in the nearest 10 years which resulted in more flood in 2000s. Result of the Standardized Precipitation Index analysis also con- firmed that the 1960s experienced the greatest fluctuations for the precipitation while the 1980s was quite steady and the 2000s had a higher SP! value in general. 1965, 1951, 1954, 1956, 1991,2000, 2003,2005 and 2007 are the years in which the SPI value is lager than 1.0, which means a flood year. While in 1966, 1953, 1973, 1978, 1985, 1988, 1994, 1999 and 2004, the SPI value is smaller than -1.0, which implied a drought year accordingly. Wavelet coherence analysis suggests that a syntonic period of about 2 a and 6 a can be found be- tween East Asia summer monsoon and precipitation in flood season. At period of about 6 a in 1960-1972, it ap- pears to be a stronger monsoon accompanied by less precipitation, but in 1986-1992, it is demonstrated to be a stronger monsoon with more precipitation relatively. The flood year of 1991 and the drought year of 1988 are the typical in phase years. However, at period of about 2 a in 1996-2004, anti-phase between the East Asia sum- mer monsoon and precipitation in flood season resulted in flood year in 2003 and drought year in 1999 and 2004 respectively.