Effects of dust-in-snow forcing over the Tibetan Plateau on the East Asian dust cycle during the Last Glacial Maximum

Abstract

The improved Community Atmosphere Model version 4 with a Bulk Aerosol Model parameterizations of the dust size distribution (CAM4-BAM) was used to investigate the dust-in-snow radiative forcing (SRF) over the Tibetan Plateau (TP) and its feedbacks on the regional climate and the dust cycle in spring, the season with the strongest dust activity, over East Asia during the Last Glacial Maximum (LGM). Simulated results show that the dust in snow can cause a large positive SRF and significant warming at the TP surface, reaching more than 45 W m−2 and 3–5 °C warming in western TP during the LGM. The SRF increases the East Asian dust emissions, dry deposition and wet deposition by 71.6 Tg (8.1%), 34.5 Tg (7.0%) and 7.9 Tg (16.0%), respectively, in spring during LGM. Further analysis reveals that, the SRF warms the TP surface and enhances the thermal effect of the TP in spring by increasing the surface shortwave radiative forcing, sensible and latent heat fluxes. A mid-upper level anticyclonic circulation anomaly is generated, thus increases the regional westerly wind over the East Asian dust source region, and in turn enhances the dust emission and dust transport over East Asia. In general, SRF over the TP creates a positive feedback loop of enhancing the East Asian dust cycle during LGM.