Aerosol and atmospheric dynamics over the tropical Indian ocean: A study from the IInd international Indian Ocean expedition

Abstract

The study addresses the aerosol distribution, boundary layer dynamics and associated shortwave radiative forcing over the Tropical Indian Ocean. The observations were carried out onboard Ocean Research Vessel Sagar Nidhi in December 2015 as a part of the International Indian Ocean Expedition-II (IIOE-II). The dominance of continentally originated aerosols was observed near the coast because of northeasterly winds, while marine aerosols abounded offshore. The uneven distribution of aerosols in the study region was due to varying atmospheric conditions triggered by various convective processes, wherein the convective available potential energy and convective inhibition energy ranged between 0.0274 and 2535.2 J kg sup(-1) and 0 and -387.5 J kg sup(-1), respectively. The atmospheric forcing varied in tandem with aerosol loading. It was evident from the high forcing values (17.98 W m sup(-2)) and corresponding heating rate of 0.504 K day sup(-1) observed near the coast. The average heating rate in the far offshore (stations 6-10) region was 0.063 plus or minus 0.017 K day sup(-1), which amounted to an approx. 87 percent decrease from the coastal location.