Aerosol characterization: comparison between measured and modelled surface radiative forcing over Bay of Bengal

Abstract

Under the aegis of Indian Space Research Organisation's ongoing climate change research programme, Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) was undertaken from 27 December 2008 to 30 January 2009 over the Bay of Bengal (BoB). Since measurements of this sort have not been made near the eastern-most coastline of BoB, a cruise was planned to have observations along the boundaries of the BoB. Here we report the columnar aerosol optical thickness (AOT), total water vapour (TWV), total ozone column (TOC) and aerosol direct surface forcing calculations by using a pair of handheld Microtops II (Ozonometer and Sunphotometer) and a gimbal-mounted short-wave (SW) pyranometer, with high temporal resolution (5 minutes). The presence of high aerosol loading and absorbing aerosols over the coastal and Andaman regions resulted in a diurnal mean aerosol surface radiative forcings of −24 and −35 W m⁻², respectively. These results are in good agreement with radiative transfer model estimations.

Acknowledgements

The study was carried out as a part of ARFI (Aerosol Radiative Forcing over India) project of ISRO-GBP (Indian Space Research Organization-Geosphere Biosphere Program). Authors are thankful to the Ministry of Earth Sciences for the shipboard facilities and cruise staff for comfortable sailing. The authors thank the Director of IITM for necessary support. The MODIS fire maps were obtained from the online MODIS Rapid Response system (NASA/GSFC). We are grateful to NOAA-CDC for the reanalysis data provided through their website http://www.cdc.noaa.gov/. The authors thank the editor and anonymous reviewers for their constructive and useful comments which improved the scientific content of the original article.