SPATIAL AND TEMPORSL ANALYSIS OF WINTER FOG OVER SOUTH ASIA BY USING SATELLITE OBSERVATIONS

Abstract

Fog is a meteorological/environmental phenomena that occurs across the Indo-Gangetic Plains (IGP) and leads to significant social and economic problems. Especially, it pose significant threats to public health, air and road traffic mobility. Meteorological stations can provide limited information regarding fog characteristic as these are only point observations. However for ccontinuous monitoring, as well as a spatially coherent picture of fog characterization is only possible through the use of satellite observations. This study focuses on fog episodes over the South Asia region using the Moderate Resolution Image Spectrometer (MODIS), the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) during winter period of 2012-15. The main objective of the study was to map the spatial extent of fog as well as to monitor its causes. Also to analyse the Aerosol Optical Depth (AOD) over south Asia with particular focus over Lahore, Pakistan. Current study involved ground observations of Particulate Matter (PM) which was conducted in the 2014-15 winter period only. Overall, this study is part of a larger multi-year and multi-country project supported by the International Centre for Integrated Mountain Development (ICIMOD) whereby Bangladesh, India and Nepal also conducted measurements in their countries starting from 2014-15 winter period. A significant correlation between MODIS (AOD) and AERONET Station (AOD) data was identified. Mass concentration of PM10 over all sampling sites exceeded the National Environmental Quality Standards (NEQS) levels at most occasions. Smoke and absorbing aerosol were found to be major constituents of fog over South Asia. Furthermore, an extended span of fog was also observed over Lahore city, Pakistan during the winter of 2014-15. The Vertical Feature Mask (VFM) provided by CALIPSO satellite indicated low lying aerosol layers, instead of clouds for the vertical profiles over Pakistan.