  Measurements of the small-, intermediate-, and large-ion concentrations and
the atmospheric electric conductivity of both polarities have been made over
the Arabian Sea on four cruises of ORV Sagarkanya during the Arabian Sea
Monsoon Experiment (ARMEX)during the monsoon and pre-monsoon seasons of 2002
and 2003. Seasonally averaged values of the total as well as polar conductivity
are much higher during the monsoon than pre-monsoon season. Surprisingly,
however, the concentration of small ions are less and those of large and
intermediate ions are more during the monsoon than pre-monsoon season. The
diurnal variations observed during the pre-monsoon season show that the
nighttime small ion concentrations are about an order of magnitude higher than
their daytime values. On the contrary, the daytime concentrations of the
intermediate and large ions are much higher than those of their nighttime
values. No such diurnal variations in ion concentrations are observed in
monsoon season. Also examined are the variations in ion concentrations of
different categories with distance from the coastline in different seasons and
the ion-concentration changes associated with the precipitation of various
types that occurred over ORV Sagarkanya. It is sufficient to invoke the
ion-aerosol attachment process to explain our pre-monsoon observations.
However, the generation of highly charged large ions by the bubble-breaking
process caused by the wave breaking due to strong southwesterly surface winds
ten to twenty meter per second over the Arabian Sea is postulated to explain
the monsoon season observations.
