Sources of origin and meteorological importance of hygroscopic and ice-forming nuclei1

The hygroscopic nuclei whose source region during the monsoon is the sea penetrate far into the interior and play important role in development of precipitation well inland. The fraction of such nuclei present in the total aerosol constitutes a more dependable criterion for distinguishing maritime airmasses from those of others.

Development of rain frequently by all-water and ice-crystal mechanisms have been suggested by the large concentrations noticed of the hygroscopic and ice-forming aerosols respectively.

While it is seen that there is a major identifiable singular source, which is the sea, for hygroscopic aerosols at Delhi, it does not appear to be so in the case of ice-forming nuclei. The latter are of varied origin and might be maritime, continental, stratospheric etc.