Estimation of the distribution of the total net radiative flux from satellite and automatic weather station data in the
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ORIGINAL PAPER
Estimation of the distribution of the total net radiative flux from satellite and automatic weather station data in the Upper Blue Nile basin, Ethiopia Eyale Bayable Tegegne 1,2,3 & Yaoming Ma 1,2,4 Zhangwei Ding 1 & Zhikun Zhu 1
&
Xuelong Chen 1,4 & Weiqiang Ma 1,4 & Bingbing Wang 1 &
Received: 10 February 2020 / Accepted: 16 September 2020 # The Author(s) 2020
Abstract Net radiation is an important factor in studies of land–atmosphere processes, water resource management, and global climate change. This is particularly true for the Upper Blue Nile (UBN) basin, where significant parts of the basin are dry and evapotranspiration (ET) is a major mechanism for water loss. However, net radiation has not yet been appropriately parameterized in the basin. In this study, we estimated the instantaneous distribution of the net radiation flux in the basin using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the Terra satellite and Automatic Weather Station (AWS) data. Downward shortwave radiation and air temperature usually vary with topography, so we applied residual kriging spatial interpolation techniques to convert AWS data for point locations into gridded surface data. Simulated net radiation outputs were validated through comparison with independent field measurements. Validation results show that our method successfully reproduced the downward shortwave, upward shortwave, and net radiation fluxes. Using AWS data and residual kriging spatial interpolation techniques makes our results robust and comparable to previous works that used satellite data at a finer spatial resolution than MODIS. The estimated net shortwave, longwave, and total radiation fluxes were in close agreement with ground truth measurements, with mean bias (MB) values of − 14.84, 5.7, and 20.53 W m−2 and root mean square error (RMSE) values 83.43, 32.54, and 78.07 W m−2, respectively. The method presented here has potential applications in research focused on energy balance, ET estimation, and weather prediction for regions with similar physiographic features to those of the Nile basin.
1 Introduction
* Yaoming Ma [email protected] * Xuelong Chen [email protected] 1
Institute of Tibetan Plateau Research, Chinese Academy of Sciences, 100101 Beijing, People’s Republic of China
2
University of Chinese Academy of Sciences, 100864 Beijing, People’s Republic of China
3
College of Natural and Computational Sciences, Center for Environmental Science, Addis Ababa University, Addis Ababa, Ethiopia
4
CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, 100101 Beijing, People’s Republic of China
The net radiation flux is the most important for land surface energy transformations, such as sensible heat, soil heat flux, and evapotranspiration (ET). It is an important quantity for research into land–atmosphere interactions (Blad et al. 1998; Monteith 1965; Niemelä et al. 2001; Nishida et al. 2003; Priestley and Taylor 1972; Rosenberg et al. 1983; Su 2002; Zeng et
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