Assessment of Trans-Pacific Dust Transport and Its Contributions to North America based on Satellite Measurements

Many types of aerosols have lifetimes long enough for their trans-continental transport, making them potentially important contributors to air quality and climate change in remote locations. Currently such assessment for the most part has been based on global model simulations and remains very uncertain. Today's constellation of passive and active satellite sensors have made it feasible to elucidate the evolution of aerosol plumes during the cross-ocean transport and generate measurement-based estimates of aerosol intercontinental transport on seasonal and annual time scales. Here we integrate satellite measurements from the Moderate resolution Imaging Spectroradiometer (MODIS) and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) to characterize the three-dimensional distributions of trans-Pacific dust transport. We estimate that, on an annual basis, 140 Tg (1 Tg = 1012 g = 106 tons) of dust is exported from East Asia. After the trans-Pacific transport, 56 Tg of dust reaches the west coast of North America. The trans-Pacific dust transport occurs predominantly above the boundary layer. Only about 3 Tg or 5.4% of dust enters North America through the lowest 2 km layer. This trans-Pacific dust transport is comparable with the total mass of particles emitted domestically in North America. Comparisons with GOCART and GMI model simulations will be presented. Implications of such intense import will be discussed.