تقويم بيانات الإشعاع الشمسي الصافي (Rn)‎ المحسوبة باستخدام المعطيات الفضائية

Abstract EN

Net Radiation (Rn) is a driving force in many physical and biological processes, and it is demanded in different studies especially in computing reference evapotranspiration (ETo), the net radiation data are rarely available due to the technical and economical limitations associated with direct measurements.

In addition, net radiation measurements are usually limited to a small area and do not represent the spatial variaability which is needed for large scale evapotranspiration mapping.

This research was conducted to estimate net solar radiation (Rn) with the aid of satellite data by using: 1- air temperature from terrestrial metrological data, 2- solar radiation data from Solar Data Intelligent System SoDa – IS which was extracted from Meteosat Images using Heliosat method, 3- albedo and surface emissivity data extracted from MODIS Images.

The estimated net solar radiation data was then evaluated by comparing it with the net solar radiation data obtained from metrological station installed at Palmyra oasis in Syria during the period (from 30 March to 30 September) in the year 2005.

Results demonstrate that computing net radiation (Rn) by using satellite images gives accurate values of (Rn) and could be used when measured values are unavailable or of a questionable quality.

The mean values of root mean square error (RMSE), mean bias deviation (MBD), and correlation coeffficients (R2) for the daily data are 17.45% , -15.4% and 0.81 respectively, while for the hourly data they are 5.65%, -2.45 % and 0.635 respectively.