عنوان مقاله [English]
All objects whose temperature exceeds absolute zero (-273 ° C) can emit energy. The amount of energy emitted from the objects depends on its temperature and can be measured according to Stephan-Boltzmann's law. The maximum emission of this energy is at a certain wavelength defined by Planck's law. With respect to the surface temperature of the sun, it emits maximum energy at a wavelength of 0.48 microns, in the middle of visible waves, while the earth emits its maximum energy at 10 microns (Infrared) wavelengths. This radiation, which starts from 3 microns and continues to 100 microns (infrared), is known Outgoing Long Radiation(OLR). Measuring this radiation is very important for understanding the energy balance and the temperature of the earth. With regards to the difficulty of measuring this radiation, the use of remote sensing data can effectively help in understand the Tempo-Spatial Variations of OLR. The purpose of this study is to estimate the seasonal Trend of Iran’s Outgoing Longwave Radiation by using National Oceanic and Atmospheric Administration (NOAA) satellites. In this study, the daily mean Outgoing Longwave Radiation data for the period 1988/3/21 to 2018/3/20, with 1° spatial coverage, were extracted in a global scale from the United State Climate Data Record (CDR) database. Then, Based on nearly 700 million Pixels, the seasonal mean of Iran’s Outgoing Longwave Radiation was calculated each year, and for each season a time-space Matrix was obtained in the dimensions of 154*30, where the rows of that location (Pixels) and columns, The time (season) is shown. Then for each season of the year, the non-parametric test of Man-Kendall was calculated at a confidence level of %90 for each individual Pixel. The results showed that there was no negative trend in different season in Iran, and only in winter, the more extensive Iran land has a positive trend. Hence, the Outgoing Longwave Radiation does not show trends in other seasons of the year. The positive trend of Outgoing Longwave Radiation during winter is due to cloudiness and snow in most of Iran. Also, in this study, the long-term mean Outgoing Longwave Radiation pattern of Iran was calculated for each season separately. The long-term mean findings of the season showed that Outgoing Longwave Radiation, in addition to latitude, also follows the topography of the earth. So that the highest Outgoing Longwave Radiation is seen in low and flat latitudes (especially in summer) and the lowest in high and uneven latitudes (especially in winter).