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

RONG Yan-shu; HU Yu-heng; ZHANG Liang; QUAN Sheng-lan; LI Chong-hao; ZHU Lin

doi:10.16032/j.issn.1004-4965.2017.06.004

Abstract：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 EOF16-8 getting from EOF of summer SSTA of Indian Ocean,EOF12-4 and EOF32-4 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.