September 2017 - The Great Horn of Africa Drought

By Katherine Hegewisch.

The current drought on the Great Horn of Africa is a regional humanitarian crisis with severe impacts in food security particularly among livestock-owning communities where water is scarce, pasture lands are barren, and harvests have been poor during consecutive seasons.  Climate Engine illustrates this drought using precipitation from CHIRPS over the past year across the great horn of Africa.

The 2016/2017 Horn of Africa Drought  

From mid 2016 to present 2017, a severe drought (see Fig. 1) is occurring across the Great Horn of Africa (Somalia/Ethiopia), making this the second year of consecutive drought in this region. Reduced surface water availability during the drought has severely affected both agricultural and pastoral livelihoods.  In late August 2017, the Famine Early Warning System (FEWS) network stated that the food security impacts from this drought are severe and continue to persist particularly for Somalia and Ethiopia, where close to 12 million people across Ethiopia, Kenya and Somalia in need of food assistance.

Fig 1: CHIRPS standardized precipitation index (SPI) for Jun 2016 - May 2017 showing precipitation more than 2 standard deviations below average (dark red regions) for southern Somalia.  Interactive View on Climate Engine: (Click Here)

Fig 1: CHIRPS standardized precipitation index (SPI) for Jun 2016 - May 2017 showing precipitation more than 2 standard deviations below average (dark red regions) for southern Somalia.  Interactive View on Climate Engine: (Click Here)

The cause for the severe drought was a delay in the onset of the 2017 rainy season leaving areas like the Addun pastoral (sheep,goats,camels)  livelihood zone (see Fig. 2B) in Southern Somalia with a 30 day delay and shorter season of replenishing rains (see Fig. 2A).

The delay was most acute in sorghum growing areas in southern Somalia, where the rainy season brought less than half of its typical value (see Fig. 3).   

Fig 2A: CHIRPS cumulative precipitation  since Dec 1, 2016 for the Addun region   of Southern Somalia  shows a 30-day delay and a shorter season for the 2017 Mar-Jun long rains.  Interactive View on Climate Engine: (Click Here) 

Fig 2A: CHIRPS cumulative precipitation  since Dec 1, 2016 for the Addun region   of Southern Somalia  shows a 30-day delay and a shorter season for the 2017 Mar-Jun long rains.  Interactive View on Climate Engine: (Click Here) 

FIG 2B: the Addun PASTORAL ZONE of Southern Somalia (where pastoral livelihoods depend on mixed sheep, goats and camels).

FIG 2B: the Addun PASTORAL ZONE of Southern Somalia (where pastoral livelihoods depend on mixed sheep, goats and camels).

Fig 3: CHIRPS precipitation percent of average for the month of delay (March 1-31,2017) of the long rains (which usually start in March) showing that much of southern Somalia is between 5-50% of avg precipitation.  Interactive View on Climate Engine: (Click Here) 

Fig 3: CHIRPS precipitation percent of average for the month of delay (March 1-31,2017) of the long rains (which usually start in March) showing that much of southern Somalia is between 5-50% of avg precipitation.  Interactive View on Climate Engine: (Click Here) 

How is it measured?

Drought is any shortage of water. This drought was characterized by a prolonged period of unusually low rainfall. We can measure this shortage of rainfall by looking at changes in precipitation from that which is expected for the region (i.e. from historical averages of many years of observed precipitation). To see the relative impacts of the changes between locations, we can also look at precipitation as a percentage of average precipitation, where 100% means that the precipitation is average.  Another measure of drought is to standardize the precipitation by converting it to a  Z-score (i.e. the number of standard deviations the precipitation is from average). The resulting standardized precipitation index (SPI) has a value of 0 when precipitation is average with negative values when the precipitation is below average (see Fig. 1).


About Climate Engine

Climate Engine provides the ability to map climate and remotely sensed datasets globally for several datasets archived and regularly updated through Google’s Earth Engine. Users can select from datasets and variables, as well as choose to view the raw data or data expressed as a deviation from some baseline or expected value (e.g., long term averages). Users can choose from a set of variables and time periods, examine percentiles or anomalies, and customize the maps to their liking.  Users can also add features to the maps. For example, in the maps shown here, we added country boundaries, livelihood zones and crop zones to aid the geographical orientation of the drought locations with respect to those aspects of livelihoods that would be impacted.