Analysis of local land atmosphere coupling characteristics over Tibetan Plateau in the dry and rainy seasons using observational data and ERA5

摘要

The local land atmosphere coupling (LoCo) focuses on the interactions between the soil states, surface fluxes, planetary boundary-layer (PBL) growth, and entrainments, offering a unique opportunity to understanding the interactions between the land and atmosphere over Tibetan Plateau (TP). This study investigates the LoCo characteristics over TP in the dry and rainy seasons by applying a mixing diagram method to the observational data at Nyingchi, Nam Co, Qomolangma, and Ngari in 2014 and the reanalysis data ERA5 from 2011 to 2014. Comparisons between the observed rainfall, T_(2m), q_(2m). surface sensible and latent heat fluxes (H_(sfc) and LE_(sfc)) and PBLH and these variables in ERA5 indicates that these variables of ERA5 are relatively reliable despite the wet and dry bias in ERA5. Comparisons of the mixing diagram based on the observation and ERA5 indicate that the ERA5 can produce relatively reliable information of the LoCo characteristics at Nam Co and Qomolangma in the June, August, and November. Analysis of the temporal variation in PBL energy budgets from 2011 to 2014 indicates that PBL energy budgets at the four stations show clear seasonal variations, indicating the influenced of the Southern Asian monsoon and the westerly jet stream on the LoCo characteristics. Analysis of LoCo characteristics over TP indicates that the spatial distributions of monthly mean PBL energy budgets over TP are strongly influenced by the snow cover in the dry season and by the soil moisture in the rainy season. The result also suggests that the relationships between H_(sfc) and PBLH are strongly influenced by the snow cover in the dry season and by the soil moisture in the rainy season.