24 Aug 2022
24 Aug 2022
Status: this preprint is currently under review for the journal WCD.

Effects on Early Monsoon Rainfall in West Africa due to Recent Deforestation in a Convection-permitting Ensemble

Julia Crook1, Cornelia Klein2,3, Sonja Folwell2, Christopher M. Taylor2,4, Douglas J. Parker1,5,6, Adama Bamba7, and Kouakou Kouadio7,8 Julia Crook et al.
  • 1School of Earth and Environment, University of Leeds, UK
  • 2UK Centre for Ecology and Hydrology, Wallingford, UK
  • 3Department of Atmospheric and Cryospheric Sciences, University of Innsbruck, Austria
  • 4National Centre for Earth Observation, Wallingford, UK
  • 5National Centre for Atmospheric Science, University of Leeds, UK
  • 6NORCE Norwegian Research Centre AS
  • 7Laboratory of Material Sciences, Environment and Solar Energy (LASMES), University Felix Houphouet Boigny (UFHB), Abidjan, Cote d’Ivoire
  • 8Geophysical Station of Lamto, BP 31, N’Douci, Cote d’Ivoire

Abstract. Tropical deforestation can have a significant effect on climate, but research attention has been directed mostly on Amazonian deforestation. The southern part of West Africa (a region dependent on rain-fed agriculture and vulnerable to droughts and flooding) has seen significant deforestation since the 1950s. Many previous tropical deforestation studies have used idealized and exaggerated deforestation scenarios and parameterized convection models. In this study we estimate realistic historical deforestation from the Land Use Harmonization dataset in West Africa and simulate the impacts in a 5-day ensemble forecast in June using a convection-permitting regional climate model. We find that sensible heat flux increases at the expense of latent heat flux in most deforested regions and rainfall increases by an average of 8.4 % over deforested pixels from 18:00–6:00 UTC, whereas changes are much less pronounced during the day. Over large areas of deforestation ~300 km inland (e.g., West Guinea) the roughness-length- and thermally induced enhanced convergence during the afternoon and evening occurs over the deforested areas resulting in increases in rainfall with little impact from reduced daytime humidity. In areas of coastal deforestation (e.g., Cote d’Ivoire), increased winds drive the sea breeze convection inland, resulting in evening rainfall reductions over the deforested area but increases further inland, in line with observations. We suggest our results would not be replicated in parameterized convection models, which are known to struggle with capturing peak convective activity in the late afternoon and long-lived nocturnal rainfall, and with reproducing observed surface-rainfall feedbacks.

Julia Crook et al.

Status: open (until 08 Oct 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2022-49', Anonymous Referee #1, 17 Sep 2022 reply
  • RC2: 'Comment on wcd-2022-49', Anonymous Referee #2, 20 Sep 2022 reply

Julia Crook et al.

Julia Crook et al.


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Short summary
This is the first study to analyze the impact of realistic historical deforestation in West Africa using a model that does not rely on parameterization of convection. Unlike previous studies, we find rainfall increases from 18:00 to 6:00 with changes driven by changes in mesoscale circulations, in line with observations in the region. This shows the potential for future studies using similar models to examine the impact of realistic deforestation in West Africa on multi-annual time scales.