Transport of black carbon from Central and West Asia to the Tibetan Plateau: Seasonality and climate effect

Abstract

Black carbon (BC) exerts potential effect on climate, especially in the Tibetan Plateau (TP), where the cryosphere and environment are very sensitive to climate change. Although transport of atmospheric BC from South and East Asia to the TP has been comprehensively investigated, transport of BC from Central and West Asia (CWA) to the TP and its climate effect on the region have received little attention and are warrant investigation. Therefore, based on the observation and ERA-Interim reanalysis data, this study investigated transport of atmospheric BC from CWA to the TP, its seasonality and climate effect over the TP using WRF-Chem model. On an annual scale, BC from CWA contributes to 5.8% of total BC over the TP. Seasonally, the contribution rates were 5.1%, 5.9%, 6.2%, and 5.7% in spring, summer, autumn, and winter, respectively. The area-averaged surface radiative forcing over the TP induced by BC from CWA ranged from −0.14 to −0.04 W m−2, with the largest and smallest negative radiative forcing occurring in autumn and winter, respectively. Affected by BC from CWA, the area-averaged surface temperature over the TP increased by 0.033 °C in summer, whereas it decreased by 0.002, 0.005, and 0.001 °C in spring, autumn and winter, respectively. In the atmosphere over the TP, the positive radiative forcing with values of 0.17, 0.20, 0.04, and 0.07 W m−2 were induced by BC from CWA in spring, summer, autumn, and winter, respectively. At the top of the atmosphere over the TP, the calculated radiative forcing associated with BC from CWA were 0.08, 0.14, −0.1, and 0.03 W m−2 in spring, summer, autumn, and winter, respectively. On an annual scale, the radiative forcing in the atmosphere and at the top of the atmosphere over the TP caused by BC from CWA were 0.12 W m−2 and 0.04 W m−2, respectively. This study enriched the theoretical connotation of transboundary transport of BC aerosols to the TP.