Using Historical Ensembles for Context in an African Food and Water Security Decision Support System

Comparing current agrometeorological conditions to historic events helps analysts and decision-makers judge the potential impact that anomalous rainfall and temperatures will have on the availability and accessibility of food and water resources. We present results from the Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System (FLDAS), which is used to produce multi-model and rainfall ensembles of the water balance over semi-arid Africa from 1982-2014. The ensemble approach allows us to assess confidence in our estimates, which is critical given that food and water insecure regions in Africa are data-poor are characterized by complex interactions and feedbacks that cause deterministic hydrologic modeling approaches to fall short. We then use the ensemble of water balance estimates to calculate drought severity (derived from modeled soil moisture), and the Water Requirement Satisfaction Index (a function of atmospheric water demand). We compare these indices to the GIMMS 30-year vegetation data product from AVHRR, and the ESA ECV 30 year microwave soil moisture. These historical time series (with confidence bounds) allow us to improve our quantitative understanding of drought thresholds, to explore sources of parameter and model uncertainty, and to better contextualize current operational drought monitoring efforts in Africa.