Comparison of precipitable water vapor derived from AIRS and SPM measurements and its correlation with surface temperature of 29 synoptic stations over Iran

Distribution of atmospheric water vapor is highly variable in time and space across the Earth; the knowledge of its distribution is essential in climate studies. In Iran, atmospheric water vapor measurements using conventional ground-based methods such as radiosondes are limited. In this paper, a comparison of precipitable water vapor (PWV) estimated by a ground-based sunphotometer (SPM) with atmospheric infrared sounder (AIRS) satellite sensor is presented over Zanjan, a city in northwest Iran for a period from December 2009 to December 2013. The PWV of SPM and AIRS have a good agreement (R2  = 93%). The seasonal bias between PWV estimated by SPM and AIRS (PWV SPM - PWV AIRS) over Zanjan city is −3.35, −5.15, −2.27, −0.95 mm during spring, summer, autumn, and winter, respectively. Average of AIRS PWV over Iran shows that the largest amount of PWV occurs along the seas (Caspian Sea, Oman Sea, and the Persian Gulf) and its lowest value happens in high altitude mountainous regions of the country. Also, correlation coefficients between AIRS PWV and surface temperature of 29 synoptic stations are calculated over Iran from September 2002 to December 2016. The average of correlation coefficients over the stations is 0.73.