Analysis of total column ozone, water vapour and aerosol optical thickness over Ahmedabad, India

Abstract

A preliminary study was performed to investigate the quality of total column ozone (TCO), water vapour (WV) and aerosol optical thickness (AOT) available from satellite and reanalysis from atmospheric models along with in situ observations over Ahmedabad (23.03 ∘ N, 72.5 ∘ E, 55 m above mean sea level), India. Ground-based measurements from a MICROTOPS II ozonometer as well as space-based satellite retrieved products from the moderate resolution imaging spectroradiometer (MODIS) and an ozone monitoring instrument were analysed during December 2014 to March 2015. The European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-Interim) created TCO and WV were also used to assess the skill of global model reanalysis over the western part of India. An increasing trend was found in the TCO and WV parameters from the winter to summer period. Investigations showed that MODIS satellite retrieved and ERA-Interim reanalysis WV are able to capture the trends compared with ground-based hand-held MICROTOPS II observations. Higher TCO was found in the MODIS data, whereas the ERA-Interim and ozone monitoring instrument TCO matched well with ground-based observations. Larger differences were found with the MODIS AOT in comparison to MICROTOPS II AOT observations. Further, analysis showed that ERA-Interim has sufficient potential to be used for various meteorological applications over the western Indian region. Furthermore, the variations of TCO, WV and AOT were studied over the orographic region of Mount Abu (∼110 km aerial distance from Ahmedabad), located in the Aravali range of mountains. Ground-based measurements at different altitudes (0.3, 1.1 and 1.67 km above mean sea level) revealed significant variations in WV and AOT. The WV varies 17.1% (30.3%) and the AOT varies 53.8% (57.5%) in 1.1 km (1.67 km), whereas no noteworthy variations are observed in the TCO in this field campaign.