Characteristics of the Convection over the Tibetan Plateau Based on OLR Data

Based on the monthly mean NOAA outgoing longwave radiation (OLR) data and surface heat fluxes derived from ERA-5 reanalysis data from 1980 to 2019, the spatial and temporal distributions of OLR and convection over the Tibetan Plateau (TP) and the relationship between surface heat fluxes and convection were investigated. Results showed that the minimum value of OLR was located in the middle of the TP and increased outward. The OLR (convection) was lower (stronger) in the eastern plateau than in the western region. In the past 40 years, the OLR (convection) increased (decreased) gradually with a period of 6 a and 2–3 a over the TP. However, the tendency for convective activity had significant differences among different regions and seasons. A growing trend of convective activity occurred in boreal summer, while it weakened in the other seasons. The convection had a weakening trend in the vicinity of the Three Rivers’ Headstream region but increased in the north of the Himalayas on the TP. In the boreal summer, the surface latent heat flux was generally stronger than the surface sensible heat flux. The evolution of convection was significantly related to both surface sensible and latent heat fluxes. The surface sensible heat flux was highly negatively correlated to the evolution of convective activity, while there was an east-west dipole pattern of correlation between the surface latent heat flux and convection. A positive correlation between the surface latent heat flux and the evolution of the convection in the western plateau was observed, while a negative correlation was evident with that in the eastern region.