Precipitable Water Vapor (PWV) is one of the most important quantities in meteorology and climate studies. PWV in Earth's atmosphere can be measured by Sun-photometer, the Atmospheric Infrared Sounder (AIRS), and radiosonde from surface, atmosphere and space-based systems, respectively. In this paper, we use PWV measured by Sun-photometer located in Institute for Advanced Studies in Basic Sciences (IASBS), AIRS and 29 Iranian synoptic stations data include temperature, dew-point temperature, pressure and relative humidity. For validation of AIRS data, the correlation coefficient between AIRS and Sun-photometer data calculated. The correlation is 90%. Average of PWV measured with sun-photometer and AIRS are 9.8 and 10.8 mm, respectively. Pearson's correlation coefficients between PWV of AIRS  data set and temperature, dew-point temperature, pressure and relative humidity for synoptic stations are calculated. Correlation between PWV and temperature, dew-point temperature, pressure, and humidity are 73%, 74%, -40% and -30%, respectively. PWV and temperature correlation coefficient map shows a positive trend between latitude and correlation coefficient. Rising a degree in latitude lead to increasing 2.8 percent in the correlation coefficient.

In this paper, aerosol optical depth measured by Caliop, MODIS, MISR, and OMI satellite sensors is compared with Sun-photometer data located in the Institute for Advanced Studies in Basic Sciences (IASBS) from December 2009 to December 2013 over Zanjan city. We computed figures for root mean square error (RMSE), mean absolute error (MAE) and root mean bias (RMB) between space-born and ground-based sensor measurements. The results show that the Caliop and MISR sensors have the highest correlation (0.61 and 0.54), respectively, with Sun-photometer measurements over Zanjan area. MISR, Caliop, and OMI sensors have the closest aerosol optical depth data to the Sun-photometer measurements (the fitted line slope is 0.68, 0.61 and 0.59, respectively) which represents the appropriate model used in the sensors to extract the aerosol optical depth. The variable monthly AOD figures obtained with different sensors indicate underestimation by MODIS and Caliop instruments (0.32 and 0.83 respectively) over Zanjan city relative to the Sun-photometer data, and overestimation by OMI and MISR instruments (1. 23 and 1.08 respectively).