No abstract

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.