AbstractsPhysics

The trans-Pacific transport of dust in 2007 - a MODIS/CALIOP study

by Lu Wang




Institution: Rutgers University
Department: Environmental Science
Degree: MS
Year: 2012
Keywords: Dust – Asia; Dust—Measurement
Record ID: 1945734
Full text PDF: http://hdl.rutgers.edu/1782.1/rucore10002600001.ETD.000065067


Abstract

Asian dust transported to the west coast of the United States and Canada has an impact on the local air quality. Thus, it is important to investigate the trans-Pacific transport of dust. In this study, observations from two satellite instruments in 2007 were utilized to evaluate this eastward flux of Asian dust – the 550 nm column aerosol optical depth and fine-mode fraction from the Moderate Resolution Imaging Spectroradiometer (MODIS), and the 532 nm column aerosol optical depth and volume depolarization ratio from the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP). The satellite observations were then compared with the Geophysical Fluid Dynamics Laboratory Global Chemical Transport Model (GCTM) simulations. In both satellite studies, the eastward flux of dust displayed distinct meridional variations on both sides of the North Pacific, peaking between 30 and 40°N in the NW Pacific and between 40 and 50°N in the NE Pacific. Both MODIS and CALIOP revealed the same seasonal pattern of the eastward dust flux in 2007: maximum in spring, minimum in summer, relatively high in winter, and intermediate in fall between that in summer and winter. Despite large discrepancies in magnitude, the percentages of the seasonal contributions to the annual dust fluxes agreed well between the MODIS and CALIOP estimates. This satellite-observed seasonal pattern was different from that simulated by GCTM. Though also having the spring maximum, GCTM showed comparable dust fluxes in winter and fall which were both significantly lower than that in summer. The annual efficiency of the eastward dust transport was 64% as estimated by MODIS and 22% by CALIOP. Both approaches indicated seasonal variations in transport efficiencies with high efficiency observed in winter. In contrast, GCTM simulated relatively constant transport efficiencies throughout the year, averaged 13% for 2007. Overall, MODIS estimated greater dust fluxes than CALIOP, by about 5-fold for the NW Pacific and 14-fold for the NE Pacific. GCTM simulated even lower dust fluxes than CALIOP.