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https://doi.org/10.5194/amt-2017-294
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
01 Nov 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).
Validation of new satellite rainfall products over the Upper Blue Nile Basin, Ethiopia
Getachew Tesfaye Ayehu1,3, Tsegaye Tadesse2, Berhan Gessesse1, and Tufa Dinku4 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 (poor) ground observations) or through integrating with rain gauge measurements. In this study, the newly available Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) data has been evaluated in comparison to rain gauge data for the period of 2000 to 2015 across the Upper Blue Nile basin in Ethiopia. Besides, the Tropical Applications of Meteorology using SATellite and ground-based observations (TAMSAT) version 2 and 3 (TAMSAT 2 and TAMSAT 3) and the African Rainfall Climatology (ARC 2) products have been used as a benchmark and compared with CHIRPS. The TAMSAT 2 rainfall estimate was used in this study mainly to assess the improvements made with the recent version of a TAMSAT product (TAMSAT 3). From the overall analysis at dekadal and monthly temporal scale, CHIRPS exhibited higher skills and the best bias value in comparison to ARC 2 but overestimates the frequency of rainfall occurrence particularly during the dry months. On the other hand, TAMSAT 3 has shown very comparable performance with that of CHIRPS product, particularly with regards to bias. The ARC 2 product was found to have the weakest performance underestimating rainfall amounts by about 24 %. The skill of CHIRPS is less affected by variation in elevation in comparison to TAMSAT 3 and ARC 2 products. While ARC 2 was found to be affected by elevation with the average biases of 1.53, 0.86 and 0.77 at lower (< 1000 m a.s.l), medium (1000 to 2000 m a.s.l) and higher elevation (> 2000 m a.s.l), respectively. Comparing the overall performance of the three products, CHIRPS exhibited the best performance followed closely by TAMSAT 3. This validation study also shows that the TAMSAT 3 has overcome the main weaknesses of TAMSAT 2, which is underestimation of high rainfall amounts by up to 31 % in this study. Overall, the finding of this validation study shows the potentials of CHIRPS product to be used for various operational applications such as rainfall pattern and variability study in the Upper Blue Nile basin in Ethiopia.

Citation: Ayehu, G. T., Tadesse, T., Gessesse, B., and Dinku, T.: Validation of new satellite rainfall products over the Upper Blue Nile Basin, Ethiopia, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2017-294, in review, 2017.
Getachew Tesfaye Ayehu et al.
Getachew Tesfaye Ayehu et al.
Getachew Tesfaye Ayehu et al.

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Short summary
The intent of this research paper is to rigorously validate the performance 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 satellite rainfall...
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