Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 3 2008 10.5194/acpd-8-8715-2008 http://www.atmos-chem-phys-discuss.net/8/8715/2008/ http://www.atmos-chem-phys-discuss.net/8/8715/2008/acpd-8-8715-2008.html http://www.atmos-chem-phys-discuss.net/8/8715/2008/acpd-8-8715-2008.pdf 8715 8742 2008-05-13 Asian dust outflow in the PBL and free atmosphere retrieved by NASA CALIPSO and an assimilated dust transport model Y. Hara hara.yukari@nies.go.jp K. Yumimoto I. Uno A. Shimizu N. Sugimoto Z. Liu D. M. Winker National Institute for Environmental Study, Tsukuba, Ibaraki, Japan Dept. of Earth System Science and Tech., Kyushu University, Fukuoka, Japan Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan National Institute of Aerospace, Hampton, VA 23666, USA NASA Langley Research Center, Hampton, VA23681, USA Three-dimensional structures of Asian dust transport in the planetary boundary layer (PBL) and free atmosphere occurring successively during the end of May 2007 were clarified using results of space-borne backscatter lidar, Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), and results simulated using a data-assimilated version of a dust transport model (RC4) based on a ground-based NIES lidar network. Assimilated results mitigated overestimation of dust concentration by reducing 17.4% of dust emissions and improved the root mean square difference (RMSD) of dust AOT between the model and NIES lidar by 31.2–66.9%. The dust layer depths, vertical and horizontal structure simulated by RC4 agreed with CALIOP from the dust source region to a long-range downwind region for which 3-D distribution of dust clouds had not been clarified previously. Based on CALIOP and RC4, two significant transport mechanisms of Asian dust in the PBL and free atmosphere were clarified: a low level dust outbreak within the dry slot region of a well developed low-pressure system, and formation of an elevated dust layer within the warm sector of a low-pressure system. Finally, the aging of pure dust particles was investigated using the particle depolarization ratio (PDR) at 532 nm and the color ratio (CR) at 1064 nm and 532 nm for the low-altitude dust transport case. Aerosols with high PDR were observed uniformly over the dust source region. 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