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Open AccessArticle

Spatio–temporal Assessment of Drought in Ethiopia and the Impact of Recent Intense Droughts

1
Center for Space and Remote Sensing Research, National Central University, No. 300, Jhongda Rd., Jhongli Dist., Taoyuan City 32001, Taiwan
2
Taiwan Group on Earth Observations, Zhubei City, Hsinchu County 30274, Taiwan
3
Taiwan International Graduate Program (TIGP), Earth System Science Program, Academia Sinica and National Central University, Taipei 112, Taiwan
4
College of Science, Bahir Dar University, P.O. Box 79, Bahir Dar, Ethiopia
*
Author to whom correspondence should be addressed.
Remote Sens. 2019, 11(15), 1828; https://doi.org/10.3390/rs11151828
Received: 16 June 2019 / Revised: 26 July 2019 / Accepted: 30 July 2019 / Published: 5 August 2019
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Abstract

The recent droughts that have occurred in different parts of Ethiopia are generally linked to fluctuations in atmospheric and ocean circulations. Understanding these large-scale phenomena that play a crucial role in vegetation productivity in Ethiopia is important. In view of this, several techniques and datasets were analyzed to study the spatio–temporal variability of vegetation in response to a changing climate. In this study, 18 years (2001–2018) of Moderate Resolution Imaging Spectroscopy (MODIS) Terra/Aqua, normalized difference vegetation index (NDVI), land surface temperature (LST), Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) daily precipitation, and the Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System (FLDAS) soil moisture datasets were processed. Pixel-based Mann–Kendall trend analysis and the Vegetation Condition Index (VCI) were used to assess the drought patterns during the cropping season. Results indicate that the central highlands and northwestern part of Ethiopia, which have land cover dominated by cropland, had experienced decreasing precipitation and NDVI trends. About 52.8% of the pixels showed a decreasing precipitation trend, of which the significant decreasing trends focused on the central and low land areas. Also, 41.67% of the pixels showed a decreasing NDVI trend, especially in major parts of the northwestern region of Ethiopia. Based on the trend test and VCI analysis, significant countrywide droughts occurred during the El Niño 2009 and 2015 years. Furthermore, the Pearson correlation coefficient analysis assures that the low NDVI was mainly attributed to the low precipitation and water availability in the soils. This study provides valuable information in identifying the locations with the potential concern of drought and planning for immediate action of relief measures. Furthermore, this paper presents the results of the first attempt to apply a recently developed index, the Normalized Difference Latent Heat Index (NDLI), to monitor drought conditions. The results show that the NDLI has a high correlation with NDVI (r = 0.96), precipitation (r = 0.81), soil moisture (r = 0.73), and LST (r = −0.67). NDLI successfully captures the historical droughts and shows a notable correlation with the climatic variables. The analysis shows that using the radiances of green, red, and short wave infrared (SWIR), a simplified crop monitoring model with satisfactory accuracy and easiness can be developed. View Full-Text
Keywords: drought; NDVI; NDLI; VCI; ENSO; time series analysis drought; NDVI; NDLI; VCI; ENSO; time series analysis
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Liou, Y.-A.; Mulualem, G.M. Spatio–temporal Assessment of Drought in Ethiopia and the Impact of Recent Intense Droughts. Remote Sens. 2019, 11, 1828.

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