Two contrasting dust-dominant periods over India observed from MODIS and CALIPSO data

Each year, prior to the onset of the Indian Summer Monsoon, the Gangetic Plains (GP), bounded by the highaltitude Himalayan mountains, are strongly influenced by the transport of dust outbreaks originating in the northwestern desert in India (known as the Thar Desert). Dust particles constitute the bulk of the regional aerosol loading which peaks annually during the pre-monsoon season. This paper integrates observations from space-borne sensors, namely MODIS and CALIPSO, together with ground sunphotometer measurements, to infer dust loading in the pre-monsoon aerosol build-up over source and sink regions in northern India. Detailed aerosol characterization from the synergetic observational assessment suggests that the two pre-monsoon seasons of 2007 and 2008 were strikingly contrasting in terms of the dust loading over both the Thar Desert and the GP. Further analysis of aerosol loading and optical properties, from the entire record of MODIS and sunphotometer observations, reveals that the 2007 pre-monsoon season was an unusually weak dustladen period. Our findings suggest the plausible role of the immediately preceding excess winter monsoon rainfall in the suppressed dust activity during the 2007 pre-monsoon season.