Integration of vulnerability assessments into the satellite-derived combined drought index

Markus Enenkel gives initial results of his YSSP project which focused on the development of i) a new, transparent drought index derived from satellite data and ii) a mobile phone application to speed up the assessment of food security-related vulnerabilities.

M. Enenkel

M. Enenkel


Droughts statistically exceed all other natural disasters in spatio-temporal extent, number of people affected, or financial loss. Food insecurity, triggered by crop failure, is a major manifestation of agricultural drought and water scarcity. However, other socio-economic precursors, such as chronically low levels of disaster preparedness or hampered access to food are equally important factors. Consequently, new and more holistic drought preparedness strategies have to link atmospheric anomalies to real-time assessments of socioeconomic vulnerabilities


This study has two main objectives. The first  focuses on the development of a new, transparent drought index derived from satellite data and based on precipitation, temperature, soil moisture, and vegetation. The second concentrates on the development of a mobile phone application to speed up the assessment of food security-related vulnerabilities. All developments are carried out in collaboration with Doctors without Borders (MSF).

Data and Methodology

The revised Combined Drought Index (CDI) is based on temperature, rainfall, soil moisture, and vegetation health. Temperature and Rainfall measurements are derived from the Global Land Data Assimilation System (GLDAS). A smoothed version of the Normalized Difference Vegetation Index (NDVI) was obtained from the University of Natural Resources and Life Sciences (Vienna, Austria). The soil moisture component is provided via the Climate Change Initiative of the European Space Agency (ESA). The application of an infiltration model facilitates the estimation of global root zone soil moisture. The Geo-Wiki land cover product is used to create a mask for further investigation. Time series analysis and the identification of time lags between all parameters enable the adjustments of weights for each variable (rainfall, temperature, etc.) in the overall index. Based on “hindcasts,”  a higher weight is assigned to index values that are ahead of actual observations. The questions in the mobile phone application were chosen based on discussions, literature review, and internal documents of aid organizations. By combining the alert levels of the drought index with the results of the mobile phone assessments, a more holistic and quicker picture of food security levels can be obtained. 

Results and Conclusions

The revised CDI is being tested over East Africa and Southeast Asia. First results indicate the suitability of satellite-derived soil moisture as a proxy for future conditions of vegetation. Surprisingly, calculating the vegetation component with a simple z-score (standard score) yields better results (forecasting capabilities) than with the original method from UN FAO. The implementation of a mobile phone app to provide outputs of the index to staff in the field is currently in the process of development. In its final version the app will also facilitate on-site validation via GPS tracking and photo upload. The key questions on socioeconomic vulnerability can be answered at any time and will be uploaded automatically when a network is available.


Markus Enenkel of the Vienna University of Technology is an Austrian citizen. He was funded by Austria's National Member Organization and worked in the Ecosystems Services and Management (ESM) Program while with the YSSP.

Please note these Proceedings have received limited or no review from supervisors and IIASA program directors, and the views and results expressed therein do not necessarily represent IIASA, its National Member Organizations, or other organizations supporting the work.

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Last edited: 19 August 2015


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