A study of chloride aerosol, total aerosol and ice nuclei in the Indian regions

Atmospheric aerosols were sampled from aircraft at various levels over Riha nd in northern India during the monsoon season of 1974 and at surface level s at Calcutta, Delhi, Varanasi and Jodhpur during different seasons of 1970 and 1971. Millipore filter assembly was used for this purpose. Chloride nu clei, total aerosol and ice nuclei concentrations were evaluated from milli pore filters. At Rihand/Varanasi, during the monsoon, the chloride size spe ctrum was broader and the distribution bimodal at cloud base level while th e spectra were narrower and the distributions unimodal at other levels. At Rihand, chloride mass and larger giant chloride number were considerably hi gher, total aerosol higher while ice nuclei concentrations were lower on th e days with moderate rain as compared to those with light rain. Calcutta (m aritime) showed maximum while Varanasi (well-inland) showed minimum chlorid e number concentrations. As compared with Calcutta, Delhi (continental) had lower chloride and total aerosol, and markedly higher ice nuclei concentra tions. Varanasi (high rainfall region) showed all the values, except for sm all-sized chlorides, notably higher with respect to Jodhpur (low rainfall r egion). Ice nuclei concentration was lowest in winter and highest in summer at Delhi. Variations of the aerosols during different parts of the day/nig ht are also discussed.