Characteristics of Cloud Systems over the Tibetan Plateau and East China during Boreal Summer

Abstract

Constrained by ERA-Interim, a cloud-resolving model is employed to characterize cloud systems over the Tibetan Plateau (TP) and east China. The authors focus on analyzing the role of different physical processes on cloud macro- and microscale properties of the cloud systems, especially convective cloud systems between east China and the TP. It is found that convective clouds over the TP are thinner than over east China. This difference is also reflected in the albedo at the top of the atmosphere, where smaller albedos are found for the clouds over the TP. Furthermore, the lifetimes of the deep cloud systems over the TP are shorter than over east China. For the entire simulated period, the latent heat released by phase transitions contributes the most to the total heating and moisture budget, followed by eddy transport over all regions. In addition, radiative heating also plays a nonnegligible role in the total heating effects over the TP. These results also suggest that the influence of ice phase processes is more important over the TP than east China, especially during deep convective periods. Affected by strong surface heat flux, the cloud-top height of convective clouds over the TP exhibits a diurnal cycle, leading to a diurnal cycle of rainfall.

Large‐Scale Circulation Environment and Microphysical Characteristics of the Cloud Systems Over the Tibetan Plateau in Boreal Summer

“…PCC has its maximum cloud top in July and August in ETP, and it is August in WTP (Figures 7a and 7b). The PCC's cloud base is around 5 km ASL, which confirms the Cloud‐Resolving Model simulation reported by Chen et al (2017). Comparing with the WTP cloud, water vapor in ETP can condensate at a lower altitude in August due to the moister environment, resulting in a lower cloud base (Figure 7a).…”

“…Moisture will be transported from the south to the TP by the south flow. This provides a necessary moisture condition for the rainfall, which is also indicated by previous studies (e.g., Chen et al, 2017; Xu et al, 2014). Comparing with Case1, Case2 shows a dryer atmosphere over the ocean and a wetter atmosphere over the land (figure not shown), which implies that the moisture transport from the ocean to the land is more active.…”

“…This data set has been widely used to assess the model simulations and study the precipitation climatology over the TP (Xu et al, 2018; You et al, 2015; Zhou et al, 2014). Meanwhile, previous studies have shown different features of apparent heat source and moisture sink between the west TP (WTP) and ETP (e.g., Chen et al, 2017, 2019). Moreover, there are differences in the land cover between the ETP and the WTP (e.g., Cui & Graf, 2009), which can influence the surface fluxes (e.g., sensible and latent heat) and then the cloud and precipitation.…”

“…Convective clouds are believed to make great contributions to the summer precipitation. Although DCs over the TP are shallower than that over the flatland, it is still an important type of precipitating clouds and the ice processes are dominant for the rainfall events (Chen & Zhou, 2015; Chen et al, 2017). According to previous studies (e.g., Ge et al, 2019; Jiang et al, 2016; Luo & Yanai, 1984), the TP experiences a strong thermal driving force due to the strong surface heat flux, which makes a favorable environment for the trigger of convections or cumulus.…”

Modification of the convective adjustment time‐scale in the Kain–Fritsch eta scheme for the case of weakly forced deep convection over the Tibetan Plateau region

“…Meanwhile, since the water vapour amounts over the TP are relatively low in summer, the convective available potential energy (CAPE) is lower than in most other continental regions during this season (Fu and Liu, 2007). These characteristics contribute to convective clouds with short lifetimes (Chen et al, 2017). Luo et al (2011) compared the deep convection over South Asia and subtropical North America over the summer seasons from 2006 to 2009 with the data sourced from CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO).…”