West African summer monsoon precipitation variability as represented by reanalysis datasets

Quagraine, Kwesi Akumenyi; Nkrumah, Francis; Klein, Cornelia ORCID: https://orcid.org/0000-0001-6686-0458; Klutse, Nana Ama Browne; Quagraine, Kwesi Twentwewa. 2020 West African summer monsoon precipitation variability as represented by reanalysis datasets. Climate, 8 (10), 111. 18, pp. https://doi.org/10.3390/cli8100111

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Abstract/Summary

Focusing on West Africa, a region riddled with in situ data scarcity, we evaluate the summer monsoon monthly rainfall characteristics of five global reanalysis datasets: ERA5, ERA-Interim, JRA-55, MERRA2, and NCEP-R2. Their performance in reproducing the West African monsoon (WAM) climatology, interannual variability, and long-term trends for the main monsoon months are compared to gauge-only and satellite products. We further examine their ability to reproduce teleconnections between sea surface temperatures and monsoon rainfall. All reanalyses are able to represent the average rainfall patterns and seasonal cycle; however, regional biases can be marked. ERA5, ERA-Interim, and NCEP-R2 underestimate rainfall over areas of peak rainfall, with ERA5 showing the strongest underestimation, particularly over the Guinea Highlands. The meridional northward extent of the monsoon rainband is well captured by JRA-55 and MERRA2 but is too narrow in ERA-Interim, for which rainfall stays close to the Guinea Coast. Differences in rainband displacement become particularly evident when comparing strong El Niño Southern Oscillation (ENSO) years, where all reanalyses except ERA-Interim reproduce wetter Sahelian conditions for La Niña, while overestimating dry conditions at the coast except for NCEP-R2. Precipitation trends are not coherent across reanalyses and magnitudes are generally overestimated compared to observations, with only JRA-55 and NCEP-R2 displaying the expected positive trend in the Sahel. ERA5 generally outperforms ERA-Interim, highlighting clear improvements over its predecessor. Ultimately, we find the strengths of reanalyses to strongly vary across the region.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.3390/cli8100111
UKCEH and CEH Sections/Science Areas:	Hydro-climate Risks (Science Area 2017-)
ISSN:	2225-1154
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
Additional Keywords:	reanalysis, precipitation, West Africa, monsoon, teleconnection, climate monitoring
NORA Subject Terms:	Meteorology and Climatology
Date made live:	04 Nov 2020 16:20 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/528838

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