Modeling the contributions of Northern Hemisphere dust sources to dust outflow from East Asia

Mineral dust aerosols can substantially influence the Earth's climate by altering the radiation budget and modifying cloud microphysical and radiative properties. Through long-range transport, dust aerosols could have a global impact. Here, using a fully coupled meteorology-chemistry model (WRF-Chem) and the tracer-tagging technique, we conduct quasi-global simulations to investigate the characteristics of dust intercontinental transport in the Northern Hemisphere and the source contributions to dust outflow from East Asia. Model results show that total dust emission from the main deserts (i.e., North Africa desert (NFD), Middle East desert (MED) and East Asia desert (EAD)) is about 4531 Tg yr(-1), in which 66% is from NFD, 24% is from MED and 10% is from EAD. During long-range transport, the NFD and MED dust plumes are separated into two branches by the Tibetan Plateau, with higher dust concentration of 4 mu g m(-3) in the northern branch (37 degrees N-60 degrees N). The imported dust mass from NFD and MED to East Asia is 16.0 Tg yr(-1) and 33.8 Tg yr(-1), respectively; the local dust mass emitted from EAD can circumnavigate and import about 0.41 Tg yr(-1) of dust into East Asia. As part of the "Asian outflow", the MED and NFD dust is transported above 600 hPa with concentration of 2 mu g m(-3), while the EAD dust is mainly transported below 600 hPa with concentration of 3 mu g m(-3). The total outflow dust mass from East Asia is 12.0, 9.7 and 7.7 Tg yr(-1) from EAD, NFD and MED, respectively. Dust particles dominate the aerosol mass concentration with a fraction of 56.5% in southern East Asia and 75.4% in northern East Asia. Moreover, dust number from EAD dominates the total aerosol number north of 37 degrees N below 600 hPa, with a size range of 0.156-0.625 mu m, but the NFD dust number is mainly above 600 hPa. MED dust number dominates the total column aerosol number south of 37 degrees N, with a size range of 0.312-0.625 mu m. Quantifying dust source contributions and the associated dust number loading and size distribution over East Asia is important for understanding the role of East Asian dust outflow in climate and hydrological cycle.