Editorial Type:
Article
Article Type:
Research Article

First Evaluation of the Day-1 IMERG over the Upper Blue Nile Basin

Dejene Sahlu Ethiopian Institute of Water Resources, Addis Ababa University, Addis Ababa, Ethiopia

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Efthymios I. Nikolopoulos Department of Physics, University of Athens, and Innovative Technologies Center S.A., Athens, Greece

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Semu A. Moges School of Civil and Environmental Engineering, Addis Ababa Institute of Technology, Addis Ababa University, Addis Ababa, Ethiopia

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Emmanouil N. Anagnostou Civil and Environmental Engineering, University of Connecticut, Storrs, Connecticut

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Dereje Hailu School of Civil and Environmental Engineering, Addis Ababa Institute of Technology, Addis Ababa University, Addis Ababa, Ethiopia

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Print Publication:
01 Nov 2016
DOI:
https://doi.org/10.1175/JHM-D-15-0230.1
Page(s):
2875–2882
Restricted access

Abstract

This work presents a first evaluation of the performance of the Integrated Multisatellite Retrievals for GPM (IMERG) precipitation product over the upper Blue Nile basin of Ethiopia. One of the unique features of this study is the availability of hourly rainfall measurements from an experimental rain gauge network in the area. Both the uncalibrated and calibrated versions of IMERG are evaluated, and their performance is contrasted against another high-resolution satellite product, which is the Kalman filter (KF)-based Climate Prediction Center (CPC) morphing technique (CMORPH). The analysis is performed for hourly and daily time scales and at spatial scales that correspond to the nominal resolution of satellite products, which is 0.1° spatial resolution. The period analyzed is focused on a single wet season (May–October 2014). Evaluation is performed using several statistical and categorical error metrics, as well as spatial correlation analysis to assess the ability of satellite products to represent spatial variability of precipitation in the area. Results show that both IMERG products have a better bias ratio and correlation coefficient on both time scales as compared to CMORPH. Comparison statistics show a slight improvement in the skill of detecting rainfall events in IMERG products compared to CMORPH. Results also show a decreasing trend in the detection ability of satellite products for increasing threshold values, highlighting the need to further improve detection during heavy precipitation.

Corresponding author address: Prof. Semu Moges, P.O. Box 385, Addis Ababa Institute of Technology, Addis Ababa University, Addis Ababa, Ethiopia. E-mail: semu_moges_2000@yahoo.com

Abstract

This work presents a first evaluation of the performance of the Integrated Multisatellite Retrievals for GPM (IMERG) precipitation product over the upper Blue Nile basin of Ethiopia. One of the unique features of this study is the availability of hourly rainfall measurements from an experimental rain gauge network in the area. Both the uncalibrated and calibrated versions of IMERG are evaluated, and their performance is contrasted against another high-resolution satellite product, which is the Kalman filter (KF)-based Climate Prediction Center (CPC) morphing technique (CMORPH). The analysis is performed for hourly and daily time scales and at spatial scales that correspond to the nominal resolution of satellite products, which is 0.1° spatial resolution. The period analyzed is focused on a single wet season (May–October 2014). Evaluation is performed using several statistical and categorical error metrics, as well as spatial correlation analysis to assess the ability of satellite products to represent spatial variability of precipitation in the area. Results show that both IMERG products have a better bias ratio and correlation coefficient on both time scales as compared to CMORPH. Comparison statistics show a slight improvement in the skill of detecting rainfall events in IMERG products compared to CMORPH. Results also show a decreasing trend in the detection ability of satellite products for increasing threshold values, highlighting the need to further improve detection during heavy precipitation.

Corresponding author address: Prof. Semu Moges, P.O. Box 385, Addis Ababa Institute of Technology, Addis Ababa University, Addis Ababa, Ethiopia. E-mail: semu_moges_2000@yahoo.com
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