Climatology of Iran's Albedo using MODIS Data during Period of 2001-2021

Albedo is one of the key parameter in climatic studies. Investigation of the Climatology of Albedo can be a tool to recognize environmental changes. The land surface albedo amount varies spatially and evolves seasonally which depends on many factors including land cover, land use, vegetation and its growth, soil moisture and the state of the surface. Satellite remote sensing is an essential technique for estimating land surface albedo at various spatial and temporal resolutions. Earth albedo is relevant for practically all earth orbiting satellites. The amount of solar radiation reflected by the earth towards a satellite. The MODIS continuously produces the land surface albedo on a global scale and with the appropriate spatial resolution and makes it available to researchers. In this research, in order to analyze the climatology albedo of Iran, firstly, the data produced by the MODIS sensor MCD43A4 product in the range of Iran in the period from 1/1/2001 to 12/30/2021 with a spatial resolution of 500 meters and a daily temporal resolution was taken from the NASA website. After the necessary pre-processing, the long-term average monthly, seasonal and annual albedo of Iran was calculated. The findings on a monthly scale showed that in the months of Jan, Feb, and Mar which are known as Iran's snow-covered months, Iran's albedo was maximum and decreased in the transition months, and then in the warm months of the year (June, July, and Aug) increases again due to the dryness of the land and the increase in the land surface temperature. This two-way behavior is also evident in the seasonal scale. These calculations were made in the worst conditions (July) on 98% of the area of Iran and in the best conditions (Jan) on 99.97% of the area of Iran. In other words, in the July, the albedo time series data was complete for about 98% of Iran's area, and there was a statistical gap in about 2% of Iran's area. In the research of Kefayat Motlagh et al. (2021), the albedo data gap values of the MODIS sensor have been investigated in different seasons and annually. The maximum distribution of albedo in winter and autumn seasons corresponds to the snow-covered heights of Alborz, Zagros and the northwest of the country. But in the spring and especially in the summer, with the increase in air temperature and surface temperature, most of the wetlands dry up. With the drying of the bottom of Jazmurian, Hamon, Shadgan, Maharlo and salt lakes and Urmia, salt flats appear. These salt marshes also show a high albedo due to their white color. On the coastal of the Caspian Sea, low albedo is seen due to the decrease in land surface temperature and increase in soil moisture.