Climate Services (Dec 2023)

Seasonal forecasts of the rainy season onset over Africa: Preliminary results from the FOCUS-Africa project

  • Matteo Zampieri,
  • Andrea Toreti,
  • Michele Meroni,
  • Dragana Bojovic,
  • Sara Octenjak,
  • Raül Marcos-Matamoros,
  • Stefano Materia,
  • Ladislaus Chang'a,
  • Mecklina Merchades,
  • María del Mar Chaves Montero,
  • Felix Rembold,
  • Alberto Troccoli,
  • Indrani Roy,
  • Ibrahim Hoteit

Journal volume & issue
Vol. 32
p. 100417

Abstract

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Precipitation seasonality is the main factor controlling vegetation phenology in many tropical and subtropical regions. Anticipating the rain onset is of paramount importance for field preparation and seeding. This is of particular importance in various African countries that rely on agriculture as a main source of food, subsistence and income. In such countries, skilful and accurate onset forecasts could also inform early warning and early actions, such as aids logistics planning, for food security. Here, we assess the skill of the seasonal forecast data provided by the Copernicus Climate Change Service in predicting the rain onset over Africa. The skill, i.e. the accuracy of the seasonal forecasts simulation ensemble compared to the climatology, is computed in a probabilistic fashion by accounting for the frequencies of normal, early and late onsets predicted by the forecast system. We compute the skill using the hindcasts (forecast simulations conducted for the past) starting at the beginning of each month in the period 1993–2016. We detect the onset timing of the rainy season using a non-parametric method that accounts for double seasonality and is suitable for the specific time-window of the seasonal forecast simulations. We find positive skills in some key African agricultural regions some months in advance. Overall, the multi-model ensemble outperforms any individual model ensemble. We provide targeted recommendations to develop a useful climate service for the agricultural sector in Africa.

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