Potential impact of carbonaceous aerosols on the Upper Troposphere and Lower Stratosphere (UTLS) during Asian summer monsoon in a global model simulation

Abstract. Recent satellite observations show efficient vertical transport of Asian pollutants from the surface to the upper level anticyclone by deep monsoon convection. In this paper, we examine the transport of carbonaceous aerosols including Black Carbon (BC) and Organic Carbon (OC) into the monsoon anticyclone using of ECHAM6-HAM, a global aerosol climate model. Further, we investigate impacts of enhanced (doubled) carbonaceous aerosols emissions on the UTLS from sensitivity simulations. These model simulations show that boundary layer aerosols are transported into the monsoon anticyclone by the strong monsoon convection from the Bay of Bengal, southern slopes of the Himalayas and the South China Sea. Doubling of emissions of BC and OC aerosols, each, over the South East Asia (10° S–50° N; 65° E–155° E) shows that lofted aerosols produce significant warming in the mid/upper troposphere. These aerosols lead to an increase in temperature by 1 K–3 K in the mid/upper troposphere and in radiative heating rates by 0.005 K/day near the tropopause. They alter aerosol radiative forcing at the surface by −1.4 W/m2; at the Top Of the Atmosphere (TOA) by +1.2 W/m2 and in the atmosphere by 2.7 W/m2 over the Asian summer monsoon region (20° N–40° N, 60° E–120° E). Atmospheric warming increases vertical velocities and thereby cloud ice in the upper troposphere. An anomalous warming over the Tibetan Plateau (TP) facilitate the relative strengthening of the monsoon Hadley circulation and elicit enhancement in precipitation over India and north east China.