Contrasts of Atmospheric Circulation and Associated Tropical
Convection between Huaihe River Valley and Yangtze River Valley Mei-yu Flooding |
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Authors: | HONG Jieli and LIU Yimin |
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Institution: | State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing} 100029,
Graduate University of Chinese Academy of Sciences, Beijing 100049 |
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Abstract: | The significant differences of atmospheric circulation between flooding in the Huaihe
and Yangtze River valleys during early mei-yu (i.e., the East Asian rainy season in June) and the
related tropical convection were investigated. During the both flooding cases, although the
geopotential height anomalies always exhibit equivalent barotropic structures in middle to high
latitudes at middle and upper troposphere, the phase of the Rossby wave train is different over
Eurasian continent. During flooding in the Huaihe River valley, only one single blocking anticyclone
is located over Baikal Lake. In contrast, during flooding in the Yangtze River valley,
there are two blocking anticyclones. One is over the Ural Mountains and the other is over Northeast
Asia. In the lower troposphere a positive geopotential height anomaly is located at the western
ridge of subtropical anticyclone over Western Pacific (SAWP) in both flooding cases, but the
location of the height anomaly is much farther north and west during the Huaihe River mei-yu
flooding. Furthermore, abnormal rainfall in the Huaihe River valley and the regions north of
it in China is closely linked with the latent heating anomaly over the Arabian Sea and Indian
peninsula. However, the rainfall in the Yangtze River valley and the regions to its south in
China is strongly related to the convection over the western tropical Pacific. Numerical
experiments demonstrated that the enhanced latent heating over the Arabian Sea and Indian peninsula
causes water vapor convergence in the region south of Tibetan Plateau and in the Huaihe River
valley extending to Japan Sea with enhanced precipitation; and vapor divergence over the Yangtze
River valley and the regions to its south with deficient precipitation. While the weakened
convection in the tropical West Pacific results in moisture converging over the Yangtze River and
the region to its south, along with abundant rainfall. |
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Keywords: | Huaihe River Yangtze River mei-yu flooding tropical convection heating anomaly |
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