sabal algorithm

The sun is known as the source of energy, the beginning of life and the source of all other energies. The global radiation of the sun is considered one of the fundamental structures of every climate. Therefore, knowing the characteristics and predicting these basic structures has a great impact on energy-related planning. The use of satellite images and remote sensing models as a suitable and low-cost tool for estimating solar radiation has been in recent years. In order to carry out this research, the images of 2020 Landsat 8 satellite OLI sensor and TIRS sensor and Sabal algorithm were used. ENVI software was used for geometrical, atmospheric and radiometric corrections of satellite images, as well as the execution of calculations related to the Sabal model, and ArcGIS software was used for creating a database, spatial analysis, cartographic operations and finally implementing the model. The results show that the average maximum incoming shortwave radiation was 901 watts per square meter on 08/09/2020 and the lowest value was 302 watts per square meter in February. Meanwhile, the lowest amount of net radiation on 10/28/2020 is 355 watts per square meter. The difference in the amount of net radiation reaching the earth in the studied area is caused by the difference in the angle of the sun and the number of sunny hours in different months of the year. Finally, it can be concluded that the solar radiation in the region has the necessary potential for the implementation of solar photovoltaic projects in the year under review. 

The sun is known as the source of energy, the beginning of life and the source of all other energies. The global radiation of the sun is considered one of the fundamental structures of every climate. Therefore, knowing the characteristics and predicting these basic structures has a great impact on energy-related planning. The use of satellite images and remote sensing models as a suitable and low-cost tool for estimating solar radiation has been in recent years. In order to carry out this research, the images of 2020 Landsat 8 satellite, OLI sensor, TIRS sensor and Sabal algorithm were used. ENVI software was used for geometrical, atmospheric and radiometric corrections of satellite images, as well as the execution of calculations related to the Sabal model, and ArcGIS software was used for creating a database, spatial analysis, cartographic operations and finally implementing the model. The results show that the average maximum incoming shortwave radiation was 816 watts per square meter in July and the lowest value was 302 watts per square meter in February. Meanwhile, the highest amount of net radiation in June is in the range of 602-680 W/m2 with a value of 32%. The difference in the amount of net radiation reaching the earth in the studied area is caused by the difference in the angle of the sun and the number of sunny hours in different months of the year. Finally, it can be concluded that the solar radiation in the region has the necessary potential for the implementation of solar photovoltaic projects in the year under review.

Estimation of plant water consumption or evapotranspiration is necessary for management and planning of water and agricultural resources, hydrological balance as well as approximate estimation of crop yield. There are various methods for determining evapotranspiration on a small scale using field measurements such as lysimeters, which are highly accurate but are not widely used due to their high cost and difficulty. For this reason, methods based on telemetry and the use of satellite imagery have received more attention from researchers. Therefore, due to the importance of the subject in this study, the evapotranspiration in the Chah region of Sistan and Baluchestan was estimated using satellite images and Sabal algorithm. In this research, Landsat 8 satellite images for 1396 and 1398 have been used and to compare the results obtained from the remote sensing method (Sabal), from the data of the synoptic meteorological station of Zahak city to estimate evapotranspiration by FAO-Penman-Montith method has been used. Using statistical indicators such as relative error and explanatory coefficient, the ability and performance of remote sensing and Sabal algorithm were investigated. Thus, the values of statistical indices in 1396 and 1398 for the coefficient of determination are 0.82 and 0.95, respectively, for the root mean square error (RMSE) with values of 2.15 and 1.27, respectively, as well as the mean error Absolute (MAE) values are 1.49 and 1.11, respectively, and finally the mean oblique error (MBE) is 0.27 and 0.09, respectively.The results indicate the acceptable accuracy of the Sabal algorithm in estimating actual evapotranspiration.