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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 16, issue 8
Hydrol. Earth Syst. Sci., 16, 2893–2913, 2012
https://doi.org/10.5194/hess-16-2893-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.
Hydrol. Earth Syst. Sci., 16, 2893–2913, 2012
https://doi.org/10.5194/hess-16-2893-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 22 Aug 2012

Research article | 22 Aug 2012

Towards an integrated soil moisture drought monitor for East Africa

W. B. Anderson1, B. F. Zaitchik2, C. R. Hain3, M. C. Anderson4, M. T. Yilmaz4, J. Mecikalski5, and L. Schultz5 W. B. Anderson et al.
  • 1Department of Geography and Environmental Engineering, The Johns Hopkins University, Baltimore, MD, USA
  • 2Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, MD, USA
  • 3Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
  • 4Hydrology and Remote Sensing Laboratory, USDA-ARS, Beltsville, MD, USA
  • 5Atmospheric Science Department, National Space Science and Technology Center, University of Alabama in Huntsville, Huntsville, AL 35805, USA

Abstract. Drought in East Africa is a recurring phenomenon with significant humanitarian impacts. Given the steep climatic gradients, topographic contrasts, general data scarcity, and, in places, political instability that characterize the region, there is a need for spatially distributed, remotely derived monitoring systems to inform national and international drought response. At the same time, the very diversity and data scarcity that necessitate remote monitoring also make it difficult to evaluate the reliability of these systems. Here we apply a suite of remote monitoring techniques to characterize the temporal and spatial evolution of the 2010–2011 Horn of Africa drought. Diverse satellite observations allow for evaluation of meteorological, agricultural, and hydrological aspects of drought, each of which is of interest to different stakeholders. Focusing on soil moisture, we apply triple collocation analysis (TCA) to three independent methods for estimating soil moisture anomalies to characterize relative error between products and to provide a basis for objective data merging. The three soil moisture methods evaluated include microwave remote sensing using the Advanced Microwave Scanning Radiometer – Earth Observing System (AMSR-E) sensor, thermal remote sensing using the Atmosphere-Land Exchange Inverse (ALEXI) surface energy balance algorithm, and physically based land surface modeling using the Noah land surface model. It was found that the three soil moisture monitoring methods yield similar drought anomaly estimates in areas characterized by extremely low or by moderate vegetation cover, particularly during the below-average 2011 long rainy season. Systematic discrepancies were found, however, in regions of moderately low vegetation cover and high vegetation cover, especially during the failed 2010 short rains. The merged, TCA-weighted soil moisture composite product takes advantage of the relative strengths of each method, as judged by the consistency of anomaly estimates across independent methods. This approach holds potential as a remote soil moisture-based drought monitoring system that is robust across the diverse climatic and ecological zones of East Africa.

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