Construction of an Inexpensive Sun Photometer to Measure Aerosol Optical Depth and Comparisons between the Measured Data and Satellite Observations

At present the absorption and scattering of solar radiation by aerosols have been recognized as important parameters for climate change. A way of probing the atmosphere from the ground is to measure the effects of the atmosphere on sunlight transmitted to Earth's surface. This indirect technique provides information about the entire atmosphere above the observer. This paper describes a new kind of inexpensive two channels LED sun photometer for monitoring aerosols that provide long-term stability. In this study, we have constructed a handheld sun photometer and used it to measure and monitor the aerosol optical depth (AOD) and compared the measured values with the satellite data. The ground based measurements of AOD at 550nm from a handheld sun photometer is compared with the Terra and Aqua MODerate Resolution Imaging Spectroradiometers (MODIS) AOD retrievals over the region of Rajshahi division, Bangladesh for the 15 days duration of June 2012. The results indicate that the constructed handheld sun photometer measurements have good correlations with Terra and Aqua MODIS retrievals with correlation coefficients r = 0.88 for Terra and r = 0.55 for Aqua whereas correlation coefficients between Terra and Aqua is 0.65. AOD at 625nm is also documented to find out the relation of AOD at different wavelengths.