Monitoring of Temporal-Spatial Distribution of Precepitable Water (PW) in Iranian Atmosphere Using Aqua/AIRS Data

Precepitable Water (PW) which is one of the most important variables studied in meteorology and cloud physics, plays an important role in predicting air and rainfall. In this study, AIRS's sensor Aqua satellite PW data were used with monthly and spatial time steps of 1°´1° for the statistical period of 2003-2019. The AIRS sensor is one of the six Aqua satellite sensors designed to help researchers to investigate change of climate and improve air forecasting. The sensor has a very wide range of resolution, which is tens of times more powerful than similar devices before it. The extracted data, after qualitative control and pre-processing, were used by specialized softwares such as ENVI, ArcGIS and Grads to build raster, vector and information tables based on the geographical boundary of Iran. The data used are numerical and their numerical values are the amount of PW in millimeters (mm) per pixel or cell that was estimated for annual, sesonal and monthly observations. The average PW in the atmosphere of Iran is 13 mm, which is lower than the average PW of the global atmosphere (22 mm). On the other hand, the amount of PW in the atmosphere of Iran does not have a homogeneous time and space distribution. So, among the studied months, the highest amount is related to July and the lowest amount is related to January. Among the seasons, the highest (lowest) amount of PW was estimated in summer (winter). Meanwhile, local factors such as remoteness and proximity to moisture sources, play an important role in the distribution of PW in the atmosphere prevailing in Iran. According to the observations, the prevailed atmosphere over the heights (especially the Zagros mountains) has very low PW concentration, in contrast to the coastal shores of the Persian Gulf, Oman Sea and Caspian Sea. It is because of having huge sources of moisture nutrition in the regions with the highest rainfall in Iran. However, the amount of PW in the atmosphere of Iran is more dependent on topography, distance, and proximity to moisture sources than on latitude (as opposed to global distribution). On the other hand, the PW behavior of the atmosphere of Iran over time, indicates that its trend is increasing. In addition to being a form of feedback on rising temperatures across Iran, the increasing trend of PW is also important in terms of climate change.