2005 Volume 83 Issue 2 Pages 137-152
We investigate the structure of a moist layer and sources of water in the southern region far from the Meiyu/Baiu front using GAME (GEWEX Asian Monsoon Experiment, GEWEX: Global Energy and Water Cycle Experiment) reanalysis data. In the period from July 4 to 15, 1998, the Meiyu/Baiu front was located over northern China (the Yellow River Valley) and the Korean Peninsula. Both regions over the plain area of mainland China (the eastern region of 112°E line) and the East China Sea have very moist air masses in this period; the total precipitable water over the regions is about 45 kgm−2. However, the structure of these moist layers is quite different. The moist layer over mainland China is deep, reaching 600 hPa. On the other hand, the moist layer over the East China Sea is shallow, with a thickness of up to 800 hPa. This difference in the structure of the moist layers can be attributed to the development of a moist convective mixing layer and the generation of shallow convective clouds in the daytime over mainland China, as a result of the supply of abundant latent and moderate sensible heat fluxes from the land surface.
We also examine the sources of water supplied into the Meiyu front using Colored Moisture Analysis (CMA). Though water vapor to generate the deep moist layer over mainland China is mainly transported from the upstream regions of the Asian summer monsoon, which include the Indian Ocean, the Indochina Peninsula, and the South China Sea, the rate of the contribution of water from the southeastern region of mainland China is over 15% of the total precipitable water, when the Meiyu front is located over northern China. This shows that the land surface over southeastern China is regarded as a major source of water to the Meiyu front.