Analysis of dust wet deposition in the mid-latitudes of the Northern Hemisphere

Wet deposition is the efficient removal process for fine dust aerosol. Dust wet deposition in the mid-latitudes of the Northern Hemisphere is investigated in this study by analyzing the dust simulations with the Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model, measurements from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and the meteorological and hydrological fields from Modern Era-Retrospective Analysis for Research and Applications (MERRA) reanalysis. The dust aerosol optical depth (AOD) and dust extinction coefficient from CALIPSO observation and GOCART simulation, in conjunction with the wind field from MERRA, show that the dust plume extending eastward from Asia to Pacific in the mid-latitudes becomes strongest in spring, while Taklamakan, Sahara, and Gobi dust are the main components and distribute vertically in the upper, middle, and lower parts of the dust layer across North Pacific, respectively. The wet deposition of dust in the mid-latitudes is mainly in the large-scale wet removal process, which becomes strongest in spring. The occurrence of wet deposition is accompanied by dust loading or transport. The comparison of wet deposition from GOCART simulation with the cloud water mixing ratio and precipitation production rate from MERRA indicated that wet deposition is mainly related to the water amount in ice cloud, and has a positive relationship with the precipitation in ice cloud layer. On the other hand, over arid and semiarid regions in central and eastern Asia with high dust loading, the absence of cloud water caused by the semidirect effect of dust (Huang et al., Geophys Res Lett 33(19), 2006b), can lower the amount of wet deposition. The comparison of wet deposition from GOCART simulation with the cloud water mixing ratio and vertical pressure velocity from MERRA demonstrates that a large-scale dynamic process, the ascending motion in the subpolar low-pressure system over the North Pacific, can increase the water amount in cloud and cause much more wet deposition of dust, which explains the occurrence of the largest wet deposition over the North Pacific.