Spring-Time Enhancement in Aerosol Burden over a High-Altitude Location in Western Trans-Himalaya:Results from Long-Term Observations

Abstract

Long-term measurements (from August 2009 to December 2014) of aerosol black carbon mass concentration (M BC) and spectral aerosol optical depth (AOD) were carried out from a high-altitude location, Hanle in western trans-Himalaya as part of the Regional Aerosol Warming Experiment. Both M BC and AOD showed distinct annual pattern with a clear springtime enhancement (April–June) with significant inter-annual variability associated with the changes in source processes. The potential source regions contributing to the springtime enhancement in aerosol loading are the dust-dominated west Asian region as well as biomass burning from NW India. The overall annual mean value of M BC over Hanle is extremely low compared to many other Himalayan locations, including the Ganges Valley Aerosol Experiment campaign site at Nainital, which also showed springtime (pre-monsoon) enhancement. The vertical extents of elevated aerosol layers, which contribute to the springtime enhancement, are found to be in the range 5–7 km amsl from the analysis of vertical profiles of extinction coefficients from CALIPSO data.