Study on the Atmospheric Boundary Layer Structure of the Qinghai-Xizang Plateau under the South Branch of the Westerly Wind and the Plateau Monsoon Circulation Field

Abstract

Using the second comprehensive scientific expedition of the Qinghai-Xizang Plateau "Land-Atmosphere Interaction and Climate Effect" three-dimensional comprehensive enhanced observation experiment May， July and October 2019 sounding data at the Mount Everest， Nyingchi， Nagqu， Shiquanhe sites and ERA5 reanalysis data.The characteristics of the atmospheric boundary layer structure of the plateau and its relationship with sensible heat and latent heat flux under the control of different wind fields in the south branch of the westerly wind and the plateau monsoon are discussed.Results show that the height of the atmospheric boundary layer at each station under the westerly south branch wind field is higher than that under the summer monsoon wind field.The height of the convective boundary layers of Mount Everest， Nyingchi， Nagqu and Shiquan River in the southwest wind field are 3250， 2250， 2760 and 3500 m respectively.while the height of the convective boundary layers of Mount Everest， Nyingchi， Nagqu and Shiquan River under the plateau monsoon field are 2000 m， 2100 m， 1650 m and 2000 m.The specific humidity of the surface layer at all site is larger on July than it on other months.The specific humidity of the surface layer in Linzhi area is larger than that of the other three regions， and it reaches 12.88 g·kg-1 at the maximum.The wind direction on Mount Everest over 1200 m is dominated by westerly winds in May and October.The wind direction on Nyingchi above 1500 m is dominated by westerly winds in May and October， and in July， winds above 1200 m is dominated by southerly winds.The wind direction of Shiquan River in May and October is dominated by west-southwest wind， and the wind direction of Shiquan River in July is dominated by west-northwest wind.The high-altitude wind speeds of Mount Everest， Nyingchi and Shiquanhe in May and October are much stronger than those in July.The sensible heat flux at each station under the west wind south branch wind field is dominated， and the latent heat flux at each station under the plateau summer wind field is dominated.

Keywords

• qinghai-xizang plateau
• westerly south branch
• plateau monsoon
• atmospheric boundary layer
• sensible heat and latent heat fluxes