Microphysical characteristics of convective clouds over ocean and land from aircraft observations

Abstract

The Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX) is a field campaign conducted in India with an instrumented research aircraft. On 29 October 2010, a cyclonic circulation over the Bay of Bengal persisted throughout the day. A special mission was conducted over the Bay of Bengal on this day with the objective of characterizing marine and continental clouds on the same day and finding contrasting/similar signatures of their microphysical properties. The research aircraft sampled growing convective clouds over the ocean and over land. High concentrations of aerosol and cloud condensation nuclei (CCN) were observed over land compared to ocean. Over ocean, higher liquid water content (LWC) and lower cloud droplet number concentrations (Nc) were observed, and droplets reached the threshold of precipitation initiation at lower cloud depths. Over land, clouds contained lower LWC and higher Nc, hence droplets did not reach the threshold of precipitation initiation at a warm temperature as in ocean clouds. Over the ocean larger droplets or drizzle were observed at lower cloud depth than over land. The maximum LWC was found to be very similar at higher altitudes. The convective clouds over land were modified by pollution aerosol with contrasting microphysical properties to those over the ocean.