South Asian dust episode in June 2006: Aerosol observations in the central Himalayas

Abstract

A dust storm blew through the Thar Desert on 12 June 2006, which has significantly influenced aerosol physical and optical properties over the central Himalayas (Nainital, 29.4°N; 79.5°E, 1958 m amsl) on 13 June 2006. Aerosol number concentrations in the coarse and giant modes on 13 June 2006 are found to be five (26 × 10 6 m −3 ) and ten (17.2 × 10 3 m −3 ) times higher compared to their respective monthly mean values. Aerosol optical depth values also showed two to four times increase, particularly at longer wavelengths suggesting increase in the concentrations of coarse and giant particles. This is supported by three to five times increase in Ångström turbidity coefficient ( β ) and significant reduction in Ångström wavelength exponent ( α ). Absence of enhancements in black carbon and accumulation mode particles suggests negligible changes in the influences of anthropogenic activities at the site during the study period.