Upscaling impact of wind/sea surface temperature mesoscale interactions on southern Africa austral summer climate

Fabien Desbiolles*, Ross Blamey, Serena Illig, Rachel James, Rondrotiana Barimalala, Lionel Renault, Chris Reason

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

17 Citations (Scopus)

Abstract

Mesoscale sea surface temperature (SST) variability plays an important role in shaping local atmospheric boundary layers through thermodynamic processes. This study focuses on the upscaling effects of mesoscale SST gradients in sensitive areas on the southern Africa regional atmospheric circulation. Using regional atmospheric model sensitivity experiments which differ only in the mesoscale SST forcing characteristics (either the full spectrum of SST variability or only its large-scale components are included), we first quantify the importance of SST gradients on regional atmospheric conditions. Agulhas eddies and meanders influence the vertical air column up to the troposphere, and mesoscale ocean patterns significantly modify incoming landwards moisture fluxes. The austral summer mean state is then modified in terms of air temperature, cloud cover and mean rainfall, with notable differences in tropical rainbands over southwestern Africa. Mesoscale SST variability favours tropical–extra-tropical interactions and cloudband development over the continent. These results stress the importance of high-resolution ocean forcing for accurate atmospheric simulations.

Original languageEnglish
Pages (from-to)4651-4660
Number of pages10
JournalInternational Journal of Climatology
Volume38
Issue number12
DOIs
Publication statusPublished - 5 Aug 2018

Bibliographical note

Funding Information:
information Natural Environment Research Council; NERCThis research was supported by NERC (Natural Environment Research Council), as part of the UMFULA project funded by the FCFA (Future Climate For Africa) program. F.D., R.B., R.J., R.B., and C.J.C.R. are directly linked to the project. Support for this study has also been provided by UCT for F.D., R.B., R.J., R.B., and C.J.C.R., IRD (Institut de Recherche et de Developement) for S.I. and L.R., by the National Research Foundation (NRF) for L.R. Authors thanks Dr. Aude Illig for fruitful discussions on statistics. All data used in this study are freely available by the following ftp or url, namely, OSTIA SST (ftp://podaac-ftp.jpl.nasa.gov/allData/ghrsst/data/L4/GLOB/UKMO/OSTIA/), MUR SST (https://podaac.jpl.nasa.gov/dataset/JPL-L4UHfnd-GLOB-MUR), AVHRR SST (ftp://eclipse.ncdc.noaa.gov/pub/OI-daily-v2/NetCDF/), and QuikSCAT L3 data (ftp://ftp.ifremer.fr/ifremer/cersat/products/gridded/MWF/L3/QuikSCAT/Daily/Netcdf/). The model configurations have been developed using facilities provided by ICTS High Performance Computing team at UCT (http://hpc.uct.ac.za) and the CSAG computing facility CORE. The ensemble-simulations have been run on the national UK Cluster ARCHER.

Funding Information:
This research was supported by NERC (Natural Environment Research Council), as part of the UMFULA project funded by the FCFA (Future Climate For Africa) program. F.D., R.B., R.J., R.B., and C.J.C.R. are directly linked to the project. Support for this study has also been provided by UCT for F.D., R.B., R.J., R.B., and C.J.C.R., IRD (Institut de Recherche et de Developement) for S.I. and L.R., by the National Research Foundation (NRF) for L.R. Authors thanks Dr. Aude Illig for fruitful discussions on statistics. All data used in this study are freely available by the following ftp or url, namely, OSTIA SST (ftp://podaac-ftp.jpl.nasa. gov/ allData/ghrsst/data/L4/GLOB/UKMO/OSTIA/), MUR SST (https://podaac.jpl.nasa.gov/dataset/JPL-L4UHfnd-GLOB-MUR), AVHRR SST (ftp://eclipse.ncdc.noaa.gov/ pub/OI-daily-v2/NetCDF/), and QuikSCAT L3 data (ftp:// ftp.ifremer.fr/ifremer/cersat/products/gridded/MWF/L3/Quik SCAT/Daily/Netcdf/). The model configurations have been developed using facilities provided by ICTS High Performance Computing team at UCT (http://hpc.uct.ac.za) and the CSAG computing facility CORE. The ensemble-simulations have been run on the national UK Cluster ARCHER.

Publisher Copyright:
© 2018 The Authors. International Journal of Climatology published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society.

Keywords

  • atmospheric circulation
  • mesoscale SST forcing
  • rainfall variability
  • southern Africa summer climate
  • upscaling effects of mesoscale air–sea interactions

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