US EPA

3280777 

Journal Article 

Climate effects of the deep continental stratus clouds generated by the Tibetan Plateau 

Yu, RC; Wang, B; Zhou, TJ 

2004 

Yes 

Journal of Climate
ISSN: 0894-8755
EISSN: 1520-0442 

17 

13 

2702-2713 

WOS:000222703800015 

Evidence is presented to show that the maximum annual mean
cloud optical depth between 60degreesS and 60degreesN is located on the lee side of the Tibetan
Plateau. This largest cloud optical depth is produced by persistent deep stratus clouds (
primarily the nimbostratus and altostratus) during winter and spring. These deep stratus clouds
are generated and maintained by the frictional and blocking effects of the Tibetan Plateau. The
plateau slows down the overflow, inducing downstream midlevel divergence; meanwhile it forces the
low-level flows to converge downstream, generating sustained large-scale lifting and stable
stratification that maintain the thick stratus clouds. These stratus clouds produce extremely
strong cloud radiative forcing at the top of the atmosphere, which fundamentally influences the
local energy balance and climate change. Analysis of the long-term meteorological station
observations reveals that the monthly mean anomalous cloudiness and surface temperature vary in
tandem. In addition, the surface warming leads to destabilization and desaturation in the
boundary layer. This evidence suggests a positive feedback between the continental stratus clouds
and surface temperature through changing lower-tropospheric relative humidity and stratification.
It is shown that the positive feedback mechanism is more robust during the period of the surface
cooling than during the surface warming. It is suggested that the positive climate feedback of
the continental stratus cloud may be instrumental in understanding the long-term climatic trend
and variations over East Asia.