Characterization of properties and spatiotemporal fields of mineral aerosol and its radiative impact using calipso data in conjunction with A-train satellite and ground-based observations and modeling

Atmospheric mineral aerosol (or dust) plays an important role in the Earth.s system. However, quantification of dust impacts has long been associated with large uncertainties because of the complex nature of mineral aerosol. A better understanding of the properties and spatiotemporal distribution of atmospheric dust on the regional and global scales is needed to improve predictions of the impact that dust radiative forcing and heating/cooling rates have on the weather and climate. The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission provides unique measurements of vertical profiles of aerosols and clouds and their properties during day and nighttime over all types of surfaces. This information has the potential to significantly improve our understanding of the properties and effects of aerosol and clouds.;This dissertation presents the results of a comprehensive analysis of CALIPSO lidar (version 2 and version 3.01) data in conjunction with A-Train satellite and ground-based observations aimed at characterizing mineral aerosol in East Asia and other major dust sources. The specific objectives were to characterize the spatial distribution and properties of atmospheric dust in the dust source regions using new CALIOP (version 3.01) data in conjunction with satellite MODIS, OMI, and CloudSat data and ground-based meteorological and lidar data; investigate changes in the vertical distribution and properties of dust during mid- and long-range transport; perform a modeling of the optical properties of nonspherical dust particles, and assess the radiative forcing and heating/cooling rates of atmospheric dust by performing radiative transfer modeling constrained by satellite data in major dust source regions.;Our research revealed significant biases in CALIPSO version 2 data, especially in the presence of dense dust plumes and dust-cloud mixed scenes. Aerosol optical depth (AOD) retrieved from CALIOP backscatter profiles was unrealistically low in many instances. Analyses on the new version 3.01 data show significant improvements in a discrimination between dust and clouds and more accurate retrievals of the aerosol extinction profiles and AOD.;Dust events observed by CALIPSO in the world.s major dust source regions and downwind were analyzed on a case-by-case basis in the springs from 2007-2010. The main focus was on dust sources in East Asia and contrasting the regional features of Asian dust to those of dusts in Central Asia, India, Arabian Peninsula, Australia, USA, and Northern Africa. Some important similarities between regional dusts were found. The particulate (aerosol) linear depolarization ratio ( deltap) exhibit high values (up to 0.3-0.35) in all dust source regions and in many instances downwind. This finding shows the importance of dust nonsphericity not only for fresh emitted particles but also for aged ones, stressing the need to account for dust nonsphericity in the models and passive remote sensing. The particulate color ratio ( chip) tends to decrease with height in dust plumes in the source regions. This is most likely due to vertically varying proportion of fine and coarse dust particles.;To aid in the retrievals and in the interpretation of CALIOP data, we have performed intensive optical simulations aimed at examining the extent to which the microphysical properties of dust particles affect the aerosol optical characteristics used in lidar remote sensing (e.g., lidar ratio, particulate depolarization, single scattering albedo). Optical modeling was performed by merging the T-matrix method and the Improved Geometric Optics Method (IGOM) enabling us to account for fine and coarse particles. Constrained by recent microphysical data, modeling results show that representing dust particles by a mixture of spheroids can reproduce some CALIPSO and ground-based lidar observations. We found that deltap at the 532 nm lidar wavelength has relatively low sensitivity to particle size distribution. In contrast, the lidar ratio Sa varies in a wide range. This finding questions the applicability of a fixed S a value adopted in the CALIPSO algorithm.;Radiative transfer modeling with CALIPSO dust vertical profiles representative of different regions was performed to assess the radiative forcing and heating rates. We found a positive forcing of dust at the top of the atmosphere (TOA) over all dust sources at high Sun angle. However, a negative forcing was found for low Sun angle, with the exception of dust source regions with high (0.3-0.35) surface albedo (e.g., Northern Africa). In the transported areas, the vertical distribution of aerosol and clouds and their optical properties are the major controlling factors, with the predominantly positive radiative forcing of dust above clouds.