A comparative study of the atmospheric circulations associated with rainy-season floods between the Yangtze and Huaihe River Basins

Here we present the results from the composite analyses of the atmospheric circulations and physical quantity fields associated with rainy-season for the selected floods cases over the Yangtze and Huaihe River basins for the 21 years (1990–2010), using the daily rain gauge measurements taken in the 756 stations throughout China and the NCEP/reanalysis data for the rainy-seasons (June–July) from 1990 to 2010. The major differences in the atmospheric circulations and physical quantity fields between the Yangtze and Huaihe River basins are as follows: for flooding years of the Yangtze River Basin, the South Asia high center is located further east than normal, the blocking high over the Urals and the Sea of Okhotsk maintains, and the Meiyu front is situated near 30°N whereas for flooding years of the Huaihe River Basin, the South Asia high center is further west than normal, the atmospheric circulations over the mid and high latitudes in the Northern Hemisphere are of meridional distribution, and the Meiyu front is situated near 33°N. In addition, there are distinct differences in water vapor sources and associated transports between the Yangtze and Huaihe River basins. The water vapor is transported by southwesterly flows from the Bay of Bengal and monsoon flows over the South China Sea for flooding years of the Yangtze River Basin whereas by southeast monsoons from the eastern and southern seas off China and monsoon flows over the South China Sea for flooding years of the Huaihe River Basin.