Identification of typical dust sources in Tarim Basin based on multi-wavelength Raman polarization lidar
Résumé
Asian mineral dust is one of the main aerosol sources in the Earth-atmosphere system, which generates significant effect on air quality, human health, and climate change. Meanwhile, knowledge of vertical optical properties of dust aerosol is crucially needed for identification of the dust source and improved understanding of radiative effect in climate model. In the study, triple-wavelength polarization Raman lidar observation combined with photometer, radiosonde and simultaneous model data was performed at Kashi in the northwestern of Tarim Basin. Taklimakan desert, located in the center of Tarim Basin, is the largest desert of Asia. Base on the measurement and model, two typical dust sources in different altitude were identified in the study, namely Taklimakan desert (East Road), Central Asia desert and Middle East desert (West Road). Particle size distribution of photometer shows that these cases were all coarse-mode-dominated with effective radius larger than 1.7 μm. The lidar observations revealed particle linear depolarization ratios (PLDR) of the Taklimakan dust ranged from 0.28 to 0.34 at 355 nm, 0.33 to 0.35 at 532 nm and 0.29-0.35 at 1064 nm, while lidar ratios (LR) ranged from 47 to 54 sr at 355 nm and from 42 to 51 sr at 532 nm wavelength. Spectral variation of LR and PLDR for Asian dust and Saharan dust was analyzed. All observed Asian dust present the consistent spectral variation that lidar ratio at 355 nm is higher than that of 532 nm, which however is not the case for Saharan dust. Both Saharan and Asian dust measurement PLDR at 532 nm is larger than that of 355 nm and 1064 nm. The measured dust properties provide particularly valuable information for dust simulation and dust climate model for different dust source.