Connection between Summer Precipitation over Haihe Basin and Northern Hemisphere Circulation Anomalies
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Abstract:
Using the monthly precipitation data of stations over the Haihe basin and NCEP/NCAR reanalysis data, the largescale relation between summer precipitation over the Haihe basin and Northern Hemisphere circulation anomalies from 1981 to 2013 is examined. The singular value decomposition (SVD) analysis is applied to reveal the connection between two fields. Results show that the leading two SVDcoupled modes explain more than half of the squared covariance between those two fields. It is found that tropical 500hPa height anomalies affect the precipitation anomalies of the whole basin, and the subtropical 500 height anomolies has significant effects on the summer precipitation anomalies over the southeast part of the basin. Tropical and subtropical circulation indices are then defined, according to the spatial patterns of the leading two SVD modes, to analyze possible mechanisms of the mentioned coupling connections. Composite analysis with respect to the above indices suggests that anomalous subtropical westerly jet and water vapor transports are associated with the anomalous indices. In weak tropical index years and especially strong subtropical index years, there can be seen a stronger and northward subtropical westerly jet, as well as significant anomalous water vapor flux convergence accumulation near the basin region. Especially, anomalous water vapor transports associated with the two anomalous indices are from different origins.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.