CALIPSO Observations of Sand and Dust Storms and Comparisons of Source Types near Kuwait City

Abstract

The Lidar on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission, makes robust measurements of dust and has generated a record that is significant both seasonally and interannually. We exploit this record to determine the properties of dust emanating from different source types during sand and dust storms (SDS). We use the relevant browsed images to describe the characteristics of the SDS layers qualitatively and the average properties quantitatively. In particular, we examine dust optical depths, dust layer frequencies, and layer heights during three sandstorms. The data are screened by using standard CALIPSO quality-assurance flags, cloud aerosol discrimination (CAD) scores, overlying features, and layer properties. To evaluate the effects of the SDS origin, phenomena such as morphology, vertical extent, and size of the dust layers, we compare probability distribution functions of the layer integrated volume depolarization ratios, geometric depths, and integrated attenuated color ratios as a function of source type. This study includes 17 individual dust storm cases observed near the city of Kuwait from three categories of sources: single source, combined sources, and unspecified sources. The strongest dust storms occurred in the summer months. The dust layers reached the highest altitudes for the combined cases. The layer top altitudes were approximately 3 km for the SDS from unspecified and single sources whereas the layer top altitudes averaged 4.1 km for the SDS from combined sources. Particles from single and combined sources recorded depolarization ratios of 0.22 and 0.23, respectively, whereas the depolarization ratios of SDS particles from unspecified sources were noticeably lower at 0.17. SDS from single sources resulted in the highest average AOD (0.66) whereas the SDS from combined sources and unspecified sources resulted in AODs of 0.41 and 0.28, respectively. Winter dust layers were disorganized, especially at night when the boundary layer was weak. The most well-organized layers close to the ground were observed in the daytime during the summer months.