K. Ueno, CHARACTERISTICS OF PLATEAU-SCALE PRECIPITATION IN TIBET ESTIMATED BY SATELLITE DATA DURING 1993 MONSOON SEASON, Journal of the Meteorological Society of Japan, 76(4), 1998, pp. 533-548
Precipitation distribution around the Tibetan Plateau was examined by
using satellite data of the Geostationary Meteorological Satellite Inf
rared channel (GMS/IR) and Special Sensor Microwave/Imager (SSM/I). Th
ese data were compared with observed precipitation and a product of Xi
e and Arkin (1997), in 1993 monsoon season. Three kinds of algorithms
were used based on an index of fractional coverage of clouds, meso-sca
le convection centers, and scattering signal of the microwave. IR-base
d estimates showed two increased centers in the southern and southeast
ern plateau with a zonal gap behind the Himalayas, but the SSM/I-based
estimate failed to yield representative distribution due to infrequen
t data sampling. IR-based estimates were combined, and the differences
between daytime and nighttime precipitation and distribution variabil
ity were clarified, in relation to the onset of the rainy season. The
differences between the daytime and nighttime precipitation depend on
the larger-scale topography. The stepwise onset of the rainy season is
known to be related to different circulation patterns around the plat
eau. In the middle of June, the first heavy precipitation was observed
in the southeastern plateau, associated with a strong southwesterly m
oisture inflow from the meandering of westerlies at the 500 hPa level
south of the plateau. After the middle of July, a stable Tibetan antic
yclone was established, and continuous precipitation prevails only in
the southern plateau. The importance of studies on the regional activi
ties of meso-scale convection and the transitional period ushering in
the mature rainy season are discussed.