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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 4 | Copyright
Atmos. Meas. Tech., 11, 1921-1936, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 06 Apr 2018

Research article | 06 Apr 2018

Validation of new satellite rainfall products over the Upper Blue Nile Basin, Ethiopia

Getachew Tesfaye Ayehu1,2,3, Tsegaye Tadesse2, Berhan Gessesse1, and Tufa Dinku4 Getachew Tesfaye Ayehu et al.
  • 1Earth observation research division, Entoto Observatory & Research Center, Addis Ababa, 33679, Ethiopia
  • 2National Drought Mitigation Center, School of Natural Resources, University of Nebraska-Lincoln, Lincoln, 830988, USA
  • 3Geospatial Data & Technology Center, Institute of Land Administration, Bahir Dar University, Bahir Dar, 79, Ethiopia
  • 4International Research Institute for Climate and Society, The Earth Institute at Columbia University, Palisades, NY 10964, USA

Abstract. Accurate measurement of rainfall is vital to analyze the spatial and temporal patterns of precipitation at various scales. However, the conventional rain gauge observations in many parts of the world such as Ethiopia are sparse and unevenly distributed. An alternative to traditional rain gauge observations could be satellite-based rainfall estimates. Satellite rainfall estimates could be used as a sole product (e.g., in areas with no (or poor) ground observations) or through integrating with rain gauge measurements. In this study, the potential of a newly available Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) rainfall product has been evaluated in comparison to rain gauge data over the Upper Blue Nile basin in Ethiopia for the period of 2000 to 2015. In addition, the Tropical Applications of Meteorology using SATellite and ground-based observations (TAMSAT 3) and the African Rainfall Climatology (ARC 2) products have been used as a benchmark and compared with CHIRPS. From the overall analysis at dekadal (10 days) and monthly temporal scale, CHIRPS exhibited better performance in comparison to TAMSAT 3 and ARC 2 products. An evaluation based on categorical/volumetric and continuous statistics indicated that CHIRPS has the greatest skills in detecting rainfall events (POD = 0.99, 1.00) and measure of volumetric rainfall (VHI = 1.00, 1.00), the highest correlation coefficients (r = 0.81, 0.88), better bias values (0.96, 0.96), and the lowest RMSE (28.45mmdekad−1, 59.03mmmonth−1) than TAMSAT 3 and ARC 2 products at dekadal and monthly analysis, respectively. CHIRPS overestimates the frequency of rainfall occurrence (up to 31% at dekadal scale), although the volume of rainfall recorded during those events was very small. Indeed, TAMSAT 3 has shown a comparable performance with that of the CHIRPS product, mainly with regard to bias. The ARC 2 product was found to have the weakest performance underestimating rain gauge observed rainfall by about 24%. In addition, the skill of CHIRPS is less affected by variation in elevation in comparison to TAMSAT 3 and ARC 2 products. CHIRPS resulted in average biases of 1.11, 0.99, and 1.00 at lower (<1000ma.s.l.), medium (1000 to 2000ma.s.l.), and higher elevation (>2000ma.s.l.), respectively. Overall, the finding of this validation study shows the potentials of the CHIRPS product to be used for various operational applications such as rainfall pattern and variability study in the Upper Blue Nile basin in Ethiopia.

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Short summary
The intent of this research paper is to rigorously validate the performance of satellite rainfall products to be used for various operational applications in data-scarce regions of the Upper Blue Nile (UBN) basin in Ethiopia. It was found that satellite rainfall products could be used as an alternative source of rainfall data in areas with no or poor ground observations. Their reliable performance could make more appropriate for various functions in complex topographic areas of the UBN basin.
The intent of this research paper is to rigorously validate the performance of satellite...