EFFECTS OF ANOMALOUS SST IN TROPICAL INDIAN OCEAN AND PACIFIC OCEAN
ON NEXT JUNE RAINFALL OVER THE YANGTZE RIVER BASIN AND AREA SOUTH OF THE BASIN
Li Yan Wang Yafei Wei Dong
State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences,
Beijing 100081
Abstract
Based on the Sea Surface Temperature Anomaly (SSTA) of NCEP/NCAR data and rainfalls
at 160 stations in China from 1951 to 2000, we examined the impact of SSTAs in tropical
Indian Ocean and tropical Pacific Ocean on next June rainfall in the Yangtze River
basin and area south of the basin by the correlation coefficient analysis and
composite analysis. The results show as follows: the contemporaneous correlation
between the Indian Ocean dipole (IOD) index and Nino3 index varied with season, with
the closest correlation being 0.523 (P<0.01) in autumn, and in the autumn El
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Ni n o/IOD positive phase year, the Nino3 index lagged the IOD index by about two
months, with the former's peak value in December and the latter's in September
October; the correlation coefficients of autumn Nino3 index, IOD
index, and newly constructed IODN3 index (a mix of Nino3 index and IOD index) with
the next June rainfall exhibited a similar distributive character the significant
correlation area in the Yangtze River basin and area south of the basin, but IODN3's
correlation is most significant, and the area of significant correlation is also
largest; June anomalous 500 hPa geopotential heights, vertical motion, and water
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vapor fluxes after an autumn El Ni n o/IOD positive phase year displayed distributive
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characters opposite to those after an autumn El Ni n o/IOD negative phase year,
indicating that the SSTAs significantly affected precipitation over the Yangtze
River basin and area south of the basin, leading to more and less June rainfall over
the basin in the next year, respectively; if Nino3/IOD positive phases conoccurred
in autumn, then the anticyclonic circulation around the Philippine Islands would
tend to enhance and maintain in next June, which is favor to precipitation in the
Yangtze River basin.
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Key words: Tropical Indian Ocean dipole, El Ni n o, Yangtze River basin, June
rainfall.