REMOTE SENSING APPLICATIONS OF THE RAINFALL FORECASTING OVER THE BLUE NILE BASIN
Ibrahim Hamouda El-Sebaie;
Abstract
The ability of producing reliable rainfall estimates is studied using satellite infrared data. These estimates could be used by hydrological models to predict and simulate the flow into High Aswan Dam in Egypt. The Blue Nile Basin, which supplies 85 % of the water that reaches Aswan, has been selected to be the study area. The topography of the selected area influences the storms during the flood period thus causing significant variability of precipitation.
Currently available data from operational meteorological satellites includes information on the temperature of the surface below the satellite and its reflectivity in different parts of the solar spectrum. Also, the principles of most of the current techniques for estimating rainfall from temperature of the cloud tops are to associate rainfall with cold (high) clouds assuming that these are the tops of active storms.
In this study, the satellite images and real time observed data through the meteosat satellite for previous years (1992-1996) July & August (during the flood season) were accumulated. The satellite images were analyzed and processed. Estimates to the amount of rainfall over the Blue Nile Basin on daily basis were obtained by applying different techniques. The validity and reliability of the satellite estimates compared to the measured • values were investigated and verified at the available stations located in the Blue Nile Basin and on the average basis.
The results showed that there are some differences between the raingages data and the satellite estimates. Two techniques (Nfs-clim & GPI) gave better results but their estimates vary from month to month and year to year. The overall correlation coefficient between the satellite estimate and the measured mean areal precipitation over the Blue Nile Basin is found to be around 0.60 and it ranges between 0.40 to 0.69 on the individual ground stations •
One of these techniques (Nfs-clim) was thus applied to forecast the amount of rainfall over the Blue Nile Basin. It is further recommended to collect more satellite data, incorporate the other kinds of the satellite images for use with the infrared images and integrate more techniques to enhance the reliability of the satellite estimates.
Currently available data from operational meteorological satellites includes information on the temperature of the surface below the satellite and its reflectivity in different parts of the solar spectrum. Also, the principles of most of the current techniques for estimating rainfall from temperature of the cloud tops are to associate rainfall with cold (high) clouds assuming that these are the tops of active storms.
In this study, the satellite images and real time observed data through the meteosat satellite for previous years (1992-1996) July & August (during the flood season) were accumulated. The satellite images were analyzed and processed. Estimates to the amount of rainfall over the Blue Nile Basin on daily basis were obtained by applying different techniques. The validity and reliability of the satellite estimates compared to the measured • values were investigated and verified at the available stations located in the Blue Nile Basin and on the average basis.
The results showed that there are some differences between the raingages data and the satellite estimates. Two techniques (Nfs-clim & GPI) gave better results but their estimates vary from month to month and year to year. The overall correlation coefficient between the satellite estimate and the measured mean areal precipitation over the Blue Nile Basin is found to be around 0.60 and it ranges between 0.40 to 0.69 on the individual ground stations •
One of these techniques (Nfs-clim) was thus applied to forecast the amount of rainfall over the Blue Nile Basin. It is further recommended to collect more satellite data, incorporate the other kinds of the satellite images for use with the infrared images and integrate more techniques to enhance the reliability of the satellite estimates.
Other data
| Title | REMOTE SENSING APPLICATIONS OF THE RAINFALL FORECASTING OVER THE BLUE NILE BASIN | Other Titles | تقدير كمية الامطار لنظام نهر النيل بتطبيق نظم الاستشعار عن بعد | Authors | Ibrahim Hamouda El-Sebaie | Issue Date | 1999 |
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