Summertime variability of aerosols and covariates over Saudi Arabia using remote sensing

The summer season is the longest in Saudi Arabia and thus significantly modifies the aerosol concentration in the country. Hydrometeorological parameters when exposed to and interacting with multiple source aerosols produce a radiative climatic response. This study was made to analyze the space-time dynamics of aerosol optical depth (AOD) with prevailing meteorological and surface parameters from the summer of 2003 to 2016. Level 3 daily products from Moderate Resolution Imaging Spectroradiometer (MODIS) and Multiangle Imaging Spectroradiometer (MISR) were used. Covariates such as surface temperature, ozone, and relative humidity (RH) from AIRS, and SO2, dust column mass density (CMD), and dust surface mass concentration (SMC) were also used on a daily time scale. The spatial distribution of AOD showed high concentration (0.5-0.9) over southern and southeastern regions, whereas relatively low concentrations were present in the northern and northwestern regions. For trend observation of AOD, the Mann-Kendall trend test was used, which manifested an increasing trend in the southern and southwestern regions, whereas a decreasing trend in the northern and central regions of Saudi Arabia was observed. Correlation analysis was performed between AOD and meteorological parameters, in which slightly similar patterns were observed for the same variables. Wavelet analysis displays significant periodicity in the 16-64 band. The wavelet coherency analysis provides the abundance of in-phase, anti-phase, leading, and lagging situations in the 16-64 periodic band, along with a few interjections of the 64-128 periodic band. Through this, an obvious difference was concluded in space-time patterns between MODIS and MISR datasets. These findings may prove useful for short-term and long-term studies including oscillating features of AOD and covariates.