Impact-based seasonal rainfall forecasting to trigger early action for droughts

Tim Busker; Hans de Moel; Bart van den Hurk; Jeroen C J H Aerts

doi:10.1016/j.scitotenv.2023.165506

Impact-based seasonal rainfall forecasting to trigger early action for droughts

Sci Total Environ. 2023 Nov 10:898:165506. doi: 10.1016/j.scitotenv.2023.165506. Epub 2023 Jul 15.

Authors

Tim Busker¹, Hans de Moel², Bart van den Hurk³, Jeroen C J H Aerts³

Affiliations

¹ Institute for Environmental Studies (IVM), Vrije Universiteit Amsterdam, Amsterdam, the Netherlands. Electronic address: tim.busker@vu.nl.
² Institute for Environmental Studies (IVM), Vrije Universiteit Amsterdam, Amsterdam, the Netherlands.
³ Institute for Environmental Studies (IVM), Vrije Universiteit Amsterdam, Amsterdam, the Netherlands; Deltares, Delft, the Netherlands.

PMID: 37454848
DOI: 10.1016/j.scitotenv.2023.165506

Abstract

The Horn of Africa faces an ongoing multi-year drought due to five consecutive failed rainy seasons, a novel climatic event with unpreceded impacts. Beyond the starvation of millions of livestock, close to 23 million individuals in the region are currently facing high food insecurity in Kenya, Somalia and Ethiopia alone. The severity of these impacts calls for the urgent upscaling and optimisation of early action for droughts. However, drought research focuses mainly on meteorological and hydrological forecasting, while early action triggered by forecasts is seldom addressed. This study investigates the potential for early action for droughts by using seasonal forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) SEAS5 system for the March-April-May (MAM) and October-November-December (OND) rainy seasons. We show that these seasonal rainfall forecasts reflect major on-the-ground impacts, which we identify from drought surveillance data from 21 counties in Kenya. Subsequently, we show that the SEAS5 drought forecasts with short lead times have substantial potential economic value (PEV) when used to trigger action before the OND season across the region (PEV_max = 0.43). Increasing lead time to one or two months ahead of the season decreases PEV, but the benefits persist (PEV_max = 0.2). Outside of Kenya, MAM forecasts have limited value. The existence of opportunities for early action during the OND season in Kenya and Somalia is demonstrated by high PEV values, with some regions recording PEV_max values close to 0.8. To illustrate the practical value of this research, we point to a dilemma that a pastoralist in the Kenyan drylands faces when deciding whether to adopt early livestock destocking. This study underscores the importance to determine the value of early actions for forecast users with different action characteristics, and to disseminate this value alongside the standard forecasts themselves. This allows users to trigger effective actions before drought impacts develop.

Keywords: Anticipatory action; Drought impact; Drought risk management; Drylands; Early warning; Humanitarian aid.

MeSH terms

Droughts*
Forecasting
Humans
Kenya
Rain
Seasons
Weather*