A22D-05
CALIPSO observations of changes in dust properties during transatlantic transport

Tuesday, 15 December 2015: 11:20
3004 (Moscone West)
Alexander Marshak, NASA Goddard Space Flight Center, Greenbelt, MD, United States, Weidong Yang, Universities Space Research Association Greenbelt, Greenbelt, MD, United States, Tamas Varnai, University of Maryland Baltimore County, JCET, Baltimore, MD, United States and Alexander B Kostinski, Michigan Technological University, Houghton, MI, United States
Abstract:
The vertical distribution of dust shape and size is highly important for understanding and estimating dust radiative forcing. We used CALIPSO nighttime datasets to examine the vertical structure and evolution of Saharan dust during transatlantic transport. The results show that most Saharan dust is lifted to high altitude and descends after traveling thousands of km-s. Initially, the depolarization ratio and color ratio of Saharan dust are uniformly distributed along altitude, suggesting vertically constant particle size and shape distributions. During transport, the depolarization ratio of Saharan dust drops at lower altitudes, suggesting that particle shapes become less irregular; while at relatively high altitudes, the depolarization ratio of dust increases during transport. The changes observed during transport likely come from the effects of gravitational sorting caused by variations in particle shape and size. A simple model with only two shapes qualitatively captures these features and confirms that shape-induced differential settling contribute significantly to the observed vertical stratification of dust properties. In addition, the effect of clouds on dust properties will be also discussed.