Air pollution in Pakistan is causing damage to health, environment and quality of life. Air pollution in Pakistan is not effectively monitored due to heavy cost involved in setting up ground stations. However, Satellite remote sensing can effectively monitor the air pollution in terms of Aerosol Optical Depth (AOD) at regional as well as global level. However, algorithms used to derive AOD from different sensors have some inherited differences which can pose challenges in monitoring regional AOD at high temporal resolution using more than one sensor. Therefore, this study focuses on comparison of four major satellite based AOD products namely Moderate Resolution Imaging SpectroRadiometer (MODIS), Multi-angle Imaging SpectroRadiometer (MISR), Ozone Monitoring Instrument multiwavelength (OMI) aerosol product and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) with the ground based AErosol RObotic NETwork (AERONET) AOD which is only available from Lahore and Karachi in Pakistan. The correlation of various AOD products with AERONET AOD is estimated statistically through coefficient of determination (R 2 ), Root Mean Square Error (RMSE), slope and intercept. It is noticed that MODIS is relatively accurate and reliable for monitoring air quality on operational bases over the land cover area of Lahore (R 2 = 0.78; RMSE = 0.18), whereas MISR over the coastal areas of Karachi (R 2 = 0.82; RMSE = 0.20). The results of the study will help the stakeholders in planning additional ground stations for operational monitoring of air quality at regional level.

Air pollution in Pakistan is causing damage to health, environment and quality of life. Air pollution in Pakistan is not effectively monitored due to heavy cost involved in setting up ground stations. However, Satellite remote sensing can effectively monitor the air pollution in terms of Aerosol Optical Depth (AOD) at regional as well as global level. However, algorithms used to derive AOD from different sensors have some inherited differences which can pose challenges in monitoring regional AOD at high temporal resolution using more than one sensor. Therefore, this study focuses on comparison of four major satellite based AOD products namely Moderate Resolution Imaging SpectroRadiometer (MODIS), Multi-angle Imaging SpectroRadiometer (MISR), Ozone Monitoring Instrument multiwavelength (OMI) aerosol product and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) with the ground based AErosol RObotic NETwork (AERONET) AOD which is only available from Lahore and Karachi in Pakistan. The correlation of various AOD products with AERONET AOD is estimated statistically through coefficient of determination (R2), Root Mean Square Error (RMSE), slope and intercept. It is noticed that MODIS is relatively accurate and reliable for monitoring air quality on operational bases over the land cover area of Lahore (R2 = 0.78; RMSE = 0.18 ), whereas MISR over the coastal areas of Karachi (R2 = 0.82; RMSE = 0.20 ). The results of the study will help the stakeholders in planning additional ground stations for operational monitoring of air quality at regional level.

This study aims at ground based atmosphere monitoring for Islamabad region (33.7167°N and 73.667°E, 508 m altitude) using locally designed dual channels, (Green (550nm) and red (625nm)) LED based handheld sunphotometer. Calibration was done by using improvised transfer of calibration method employing pre-calibrated GLOBE (Global Learning and Observation to Benefit Environment) sunphotometer. Aerosol optical thickness (AOT) of said region for the month of July, August 2017 was calculated using acquired data for red and green channels. Matching trends (correlation up to 95%) were observed for AOT obtained with GLOBE and local sunphotometer. AOT of Islamabad region generated by satellitebased Moderate Resolution Imaging Spectro-radiometer (MODIS) instrument board on AQUA and Terra satellites has also been presented for calibration period (Oct 2016-Feb 2017) to qualify our findings. The inter-comparison of data with MODIS instrument AQUA and Terra from Oct 2016 to Feb. 2017 with the local sunphotometer green channel yielded a correlation coefficients in range of 0.51-0.55 approaching the previously reported range values of (∼0.55-0.60) for similar comparison. Along with AOT, in this study, the average daily Angstrom exponent α, and angstrom turbidity constant , have also been reported. The average of angstrom exponent for recorded data is 1.42, this implies moderately polluted urban atmosphere of area under study, while the 19 th and 20 th July are clearest day for monitoring period with = 0.07 and = 0.083 respectively.