Seasonal and diurnal variations of cloud systems over the East Tibetan
Plateau and the East China: A Cloud-Resolving model study
Abstract
Seasonal and diurnal variations of the cloud are profoundly affected by
the large-scale environment and the local topography. In this study, the
one-year-long simulation was conducted by a two-dimensional Cloud
Resolving Model over the eastern Tibetan Plateau (ETP) and two
sub-region of East China (EC), which are the middle and low reaches of
the Yangtze River and Pearl River Delta. It found that deep convections
(DCCs) can hardly happen in the cold season over the ETP while it can
happen all the year around over the EC, and it is about 20-30% thinner
in the ETP than in the EC. Most of EC rainfall events (Precipitation
Intensity, PI> 2.5 mm hr) relates to DCCs with cloud ice
processes during the warm season. Because of the high elevation, the ETP
warm-season freezing level is much lower than that of EC, making a
favorable condition for cloud ice processes. DCCs are responsible for
the diurnal variations of warm-season rainfall in all the regions.
Warn-season DCCs have the greatest total cloud water content and
frequency in the afternoon over the ETP, resulting in the afternoon peak
of rainfall events. Besides the afternoon peak, rainfall events also
have a nocturnal peak due to the DCCs over the ETP in spring, summer,
and autumn. Strong surface heat fluxes around noon can trigger or
promote DCCs in spring, summer, and autumn over the ETP, but only
produce cumulus in winter due to the cold and dry environment.