Spatial-temporal analysis of the 1970’s Sahel drought

The drought in the Sahel region during most of the 1970’s is one of the most recent mega-drought episodes. Drought-caused famine killed more than 100,000 people, and left more than 750,000 dependent on international aid.

Analyzing past drought episodes may help us better understand the onset and development of droughts, especially if we are able to relate them to their genuine causes. With this goal in mind, we are working on a tool for identifying and analyzing drought episodes, based on our SPEIbase drought dataset. This tool is able to automatically isolate drought episodes given a set of criteria, and produce summary statistics and time series for their analysis.

Drought parameters

Major drought parameters: duration, magnitude (shaded area) and maximum intensity.

As an example, we have put online a preliminar analysis of the 1970’s drought in the Sahel and Ethiopia regions. Only the SPEI values below ‑0.83 were retained on the analysis. The time series of monthly SPEI maps between the early onset of the drought in 1968 until its last manifestation in 1980 can be animated using the keyboard cursor arrows. It is interesting noting how the drought moved from mainly the Sahel region during the first half of the 1970’s to the Ethiopia — Somalia area during the second half. The last three maps on the menu report the summary of the drought episode. The integral (created by summing up all the SPEI values during the episode) is probably the better way to summarize the magnitude of the whole drought episode, showing clearly two geographical poles. The other two maps (duration and maximum intensity) complete the information on the episode.

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