Climatology and interannual variability of boreal spring wet season precipitation in the eastern Horn of Africa and implications for its recent decline

Brant Liebmann; Ileana Blade; Dave Allured; Xiao-Wei Quan; Chris Funk; Martin P Hoerling; Andrew Hoell; Peter Peterson; Wassila Mamadou Thiaw

doi:10.1175/jcli-d-16-0452.1

USGS · 70249440

Climatology and interannual variability of boreal spring wet season precipitation in the eastern Horn of Africa and implications for its recent decline

Brant Liebmann·Ileana Blade·Dave Allured·Xiao-Wei Quan·Chris Funk·Martin P Hoerling·Andrew Hoell·Peter Peterson·Wassila Mamadou Thiaw

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Abstract

The 1981–2014 climatology and variability of the March–May eastern Horn of Africa boreal spring wet season are examined using precipitation, upper- and lower-level winds, low-level specific humidity, and convective available potential energy (CAPE), with the aim of better understanding the establishment of the wet season and the cause of the recent observed decline. At 850 mb, the development of the wet season is characterized by increasing specific humidity and winds that veer from northeasterly in February to southerly in June and advect moisture into the region, in agreement with an earlier study. Equally important, however, is a substantial weakening of the 200-mb climatological easterly winds in March. Likewise, the shutdown of the wet season coincides with the return of strong easterly winds in June. Similar changes are seen in the daily evolution of specific humidity and 200-mb wind when composited relative to the interannual wet season onset and end, with the easterlies decreasing (increasing) several days prior to the start (end) of the wet season. The 1981–2014 decrease in March–May precipitation has also coincided with an increase in 200-mb easterly winds, with no attendant change in specific humidity, leading to the conclusion that, while high values of specific humidity are an important ingredient of the wet season, the recent observed precipitation decline has resulted mostly from a strengthening of the 200-mb easterlies. This change in the easterly winds appears to be related to an increase in convection over the Indonesian region and in the associated outflow from that enhanced heat source.

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Journal of Climate Article

Source-reported bounding extent: -13.410994034322911° to 22.59372606392911° latitude; 32.656250000000796° to 55.5078125000002° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Brant Liebmann, Ileana Blade, Dave Allured, Xiao-Wei Quan, Chris Funk, Martin P Hoerling, Andrew Hoell, Peter Peterson, Wassila Mamadou Thiaw. 2017-05-02. Climatology and interannual variability of boreal spring wet season precipitation in the eastern Horn of Africa and implications for its recent decline. https://doi.org/10.1175/jcli-d-16-0452.1

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