Size matters: Influence of multiple scattering on CALIPSO light-extinction profiling in desert dust
Article first published online: 18 MAY 2010
Copyright 2010 by the American Geophysical Union.
Geophysical Research Letters
Volume 37, Issue 10, May 2010
How to Cite
2010), Size matters: Influence of multiple scattering on CALIPSO light-extinction profiling in desert dust, Geophys. Res. Lett., 37, L10801, doi:10.1029/2010GL042815., , , , , and (
- Issue published online: 18 MAY 2010
- Article first published online: 18 MAY 2010
- Manuscript Accepted: 6 APR 2010
- Manuscript Revised: 31 MAR 2010
- Manuscript Received: 5 FEB 2010
- mineral dust;
- multiple scattering
 We investigate the discrepancies in measurements of light extinction and extinction-to-backsatter ratio (lidar ratio) of desert dust with CALIPSO and ground-based lidar systems. Multiwavelength polarization Raman lidar measurements in the Saharan dust plume performed at Praia, Cape Verde, 15.0°N, 23.5°W, during SAMUM–2 in June 2008 were analyzed and compared to results of nearby CALIPSO overflights. The particle extinction coefficients and thus the optical depth are underestimated in the CALIPSO products by about 30% compared to Raman lidar measurements. A pre-defined lidar ratio of 40 sr at 532 nm is used for mineral dust in the CALIPSO algorithms in agreement with values of 41 ± 6 sr found from constrained retrievals. However, the ground-based lidar observations show much larger values of the order of 55 ± 10 sr. The discrepancies can be explained by the influence of multiple scattering which is ignored in the CALIPSO retrievals. Based on recent observations of the size distribution of dust particles from airborne in-situ observations during SAMUM–1, our model calculations show that the multiple-scattering-related underestimation of the extinction coefficient in the CALIPSO lidar signals ranges from 10%–40%. We propose a method to overcome this underestimation.