红水河汛期径流与印度洋海温异常的关系

使用1951—2014年广西河池市红水河龙滩站的月流量和同期海温、500 hPa位势高度、850 hPa矢量风资料，基于相关分析、EOF分析和合成分析，研究了红水河汛期流量与印度洋海温异常的关系，以及印度洋海温异常影响红水河流量的物理机制。结果表明，印度洋海温距平分布的三种模态，包括前期夏季印度洋海温距平EOF1_6—8、EOF1_2—4、印度洋海温距平EOF1_2—4和EOF3_2—4，与红水河汛期流量显著相关。用这三个模态的时间系数、龙滩站前期4—5月平均流量和南印度洋2、3和4月偶极子指数可以很好地模拟龙滩站汛期流量，因此，它们可以作为红水河径流预测的物理因子。印度洋海温异常影响红水河汛期流量的途径可以概括为，印度洋海温冷水年，冷异常可在四个季节持续。春季冷海温可使北半球春季南支气流上小槽波动强烈，南支槽加强，水汽输送显著增强；夏季可显著增强夏季风气流，使更多的水汽输送到红水河增大径流量；秋季和冬季，印度洋的冷海水减弱了北半球冬季环流形势，诱使西北太平洋水汽向中国东部地区输送，使红水河有更多的水汽汇集增大龙滩站流量。反之，印度洋海温暖水年时，四个季节的海温持续增暖，使北半球中纬度低气压系统变得不活跃，冬季形势进入早、而结束晚，中国东部受干燥气流控制时间长，春季和夏季副热带高压增强，同时，夏季风减弱，水汽输送较少，使汛期红水河流量减小。 

THE RELATIONSHIP BETWEEN FLOOD SEASON RUNOFF OF HONGSHUI RIVER AND SEA SURFACE TEMPERATURE OF INDIAN OCEAN

By using monthly runoff of Longtan Hydropower Station in the Hongshui River, SST data from NOAA, 500 hPa potential height, and 850 hPa vector wind from the NCEP reanalysis, during the year of 1951—2014, the relationship between the flood season runoff of Hongshui River and sea surface temperature anomalies (SSTA) of Indian Ocean and the mechanism of impact of SSTA of Indian Ocean on the flood season runoff of Hongshui River were studied, based on correlation analysis, empirical orthogonal function (EOF) and composite analysis. There are three SSTA distribution modes in the Indian Ocean, including EOF1_6-8 getting from EOF of summer SSTA of Indian Ocean, EOF1_2-4 and EOF3_2-4 getting from EOF of SSTA from February to April of Indian Ocean, that had significant effect on the flood season runoff of Hongshui River. The flood season runoff of Longtan station could be well simulated by seven factors, including the three modes, previous runoff from April to May of Longtan plus monthly South Indian Dipole Index(SIDI) from February to April. The way in which SSTA impacted flood season runoff was summarized as follows:As SSTA in the Indian Ocean was cold, cooling SSTA would be continued in four seasons. In spring, a southwesterly trough was enhanced by cooling SSTA, and then the water vapor could be transported to the eastern part of China. In summer, the monsoon could be enhanced dramatically, and then more water vapor was transported to Hongshui River to increase the runoff. In autumn and winter, the winter synoptic situation was weakened by cooling SSTA and water vapor from Northwest Pacific was assembled, and then the runoff would be increased. Whereas, when Indian Ocean SSTA was in a warm year, every season SSTA became warmer. The lower pressure systems in the middle latitude became inactive, and the winter synoptic situation appeared early and ended late, and then the drier air flow controlled eastern China longer than normal. The subtropical high in spring and summer was stronger than normal and summer monsoon would be weakened, so that water vapor could not be transported to eastern China, and then the runoff in Longtan would be decreased.