Climate Dynamics

, Volume 44, Issue 5–6, pp 1583–1594 | Cite as

Significant impacts of radiation physics in the Weather Research and Forecasting model on the precipitation and dynamics of the West African Monsoon

  • R. LiEmail author
  • J. Jin
  • S.-Y. Wang
  • R. R. Gillies


Precipitation from the West African Monsoon (WAM) provides food security and supports the economy in the region. As a consequence of the intrinsic complexities of the WAM’s evolution, accurate simulations of the WAM and its precipitation regime, through the application of regional climate models, are challenging. We used the coupled Weather Research and Forecasting (WRF) and Community Land Model (CLM) to explore impacts of radiation physics on the precipitation and dynamics of the WAM. Our results indicate that the radiation physics schemes not only produce biases in radiation fluxes impacting radiative forcing, but more importantly, result in large bias in precipitation of the WAM. Furthermore, the different radiation schemes led to variations in the meridional gradient of surface temperature between the north that is the Sahara desert and the south Guinean coastline. Climate diagnostics indicated that the changes in the meridional gradient of surface temperature affect the position and strength of the African Easterly Jet as well as the low-level monsoonal inflow from the Gulf of Guinea. The net result was that each radiation scheme produced differences in the WAM precipitation regime both spatially and in intensity. Such considerable variances in the WAM precipitation regime and dynamics, resulting from radiation representations, likely have strong feedbacks within the climate system and so have inferences when it comes to aspects of predicted climate change both for the region and globally.


Regional climate modeling WRF-CLM African Monsoon Climate change Radiation Surface temperature gradient 



This work was supported by the Utah Agricultural Experiment Station, and grants NNX13AC37G and WaterSMART R13AC80039. This research was carried out using the high performance computing resources at Utah State University.


  1. Afiesimama EA, Pal JS, Abiodun BJ, Gutowski WJ Jr, Adedoyin A (2006) Simulation of West African monsoon using the RegCM3. Part I: model validation and interannual variability. Theor Appl Climatol 86:23–37CrossRefGoogle Scholar
  2. Bonan GB, Oleson KW, Vertenstein M, Levis S, Zeng XB, Dai YJ, Dickinson RE, Yang ZL (2002) The land surface climatology of the community land model coupled to the NCAR community climate model. J Clim 15:3123–3149CrossRefGoogle Scholar
  3. Chou C, Neelin JD (2003) Mechanisms limiting the northward extent of the northern summer monsoons over North America, Asia, and Africa. J Clim 16:406–425CrossRefGoogle Scholar
  4. Clough SA, Shephard MW, Mlawer E, Delamere JS, Iacono M, Cady-Pereira K, Boukabara S, Brown PD (2005) Atmospheric radiative transfer modeling: a summary of the AER codes. J Quant Spectrosc Radiat Transfer 91:233–244CrossRefGoogle Scholar
  5. Collins WD et al (2006) The formulation and atmospheric simulation of the Community Atmosphere Model version 3 (CAM3). J Clim 19:2144–2161CrossRefGoogle Scholar
  6. Cook KH (1999) Generation of the African easterly jet and its role in determining West African precipitation. J Clim 12:1165–1184CrossRefGoogle Scholar
  7. Darnell WL, Staylor WF, Gupta SK, Denn FM (1988) Estimation of surface insolation using sun-synchronous satellite data. J Clim 1:820–835CrossRefGoogle Scholar
  8. Druyan LM, Koster RD (1989) Sources of sahel precipitation for simulated drought and rainy seasons. J Clim 2:1438–1446CrossRefGoogle Scholar
  9. Dudhia J (1989) Numerical study of convection observed during the winter monsoon experiment using a mesoscale two-dimensional model. J Atmos Sci 46:3077–3107CrossRefGoogle Scholar
  10. Flaounas E, Bastin S, Janicot S (2011) Regional climate modelling of the 2006 West African monsoon: sensitivity to convection and planetary boundary layer parameterisation using WRF. Clim Dyn 36:1083–1105CrossRefGoogle Scholar
  11. Gallee H et al (2004) A high-resolution simulation of a West African rainy season using a regional climate model. J Geophys Res Atmos 109:D05108CrossRefGoogle Scholar
  12. Gupta SK, Darnell WL, Wilber AC (1992) A parameterization for longwave surface radiation from satellite data—recent improvements. J Appl Meteorol 31:1361–1367CrossRefGoogle Scholar
  13. Iacono MJ, Mlawer EJ, Clough SA, Morcrette JJ (2000) Impact of an improved longwave radiation model, RRTM, on the energy budget and thermodynamic properties of the NCAR community climate model, CCM3. J Geophys Res Atmos 105:14873–14890CrossRefGoogle Scholar
  14. Iacono MJ, Mlawer EJ, Delamere JS, Clough SA, Morcrette J, Hou Y (2005) Application of the shortwave radiative transfer model, RRTMG_SW, to the National Center for Atmospheric Research and National Centers for Environmental Prediction General Circulation Models. In: Fifteenth ARM science team meeting proceedings, Daytona Beach, FL, March 14–18, 2005Google Scholar
  15. Iacono MJ, Delamere JS, Mlawer EJ, Shephard MW, Clough SA, Collins WD (2008) Radiative forcing by long-lived greenhouse gases: calculations with the AER radiative transfer models. J Geophys Res Atmos 113:D13103CrossRefGoogle Scholar
  16. Jin J, Wen L (2012) Evaluation of snowmelt simulation in the Weather Research and Forecasting model. J Geophys Res Atmos 117:D10110CrossRefGoogle Scholar
  17. Kalnay E et al (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteorol Soc 77:437–471CrossRefGoogle Scholar
  18. Kiladis GN, Thorncroft CD, Hall NMJ (2006) Three-dimensional structure and dynamics of African easterly waves. Part I: observations. J Atmos Sci 63:2212–2230CrossRefGoogle Scholar
  19. Mathon V, Laurent H, Lebel T (2002) Mesoscale convective system rainfall in the Sahel. J Appl Meteorol 41:1081–1092CrossRefGoogle Scholar
  20. Mlawer E, Taubman S, Brown P, Iacono M, Clough S (1997) Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave. J Geophys Res Atmos 102:16663–16682CrossRefGoogle Scholar
  21. Morcrette J, Barker HW, Cole JNS, Iacono MJ, Pincus R (2008a) Impact of a new radiation package, McRad, in the ECMWF integrated forecasting system. Mon Weather Rev 136:4773–4798CrossRefGoogle Scholar
  22. Morcrette J, Mozdzynski G, Leutbecher M (2008b) A reduced radiation grid for the ECMWF integrated forecasting system. Mon Weather Rev 136:4760–4772CrossRefGoogle Scholar
  23. Nicholson SE, Tucker CJ, Ba MB (1998) Desertification, drought, and surface vegetation: an example from the West African Sahel. Bull Am Meteorol Soc 79:815–829CrossRefGoogle Scholar
  24. Pal JS et al (2007) Regional climate modeling for the developing world—the ICTP RegCM3 and RegCNET. Bull Am Meteorol Soc 88:1395–1409CrossRefGoogle Scholar
  25. Pu B, Cook KH (2012) Role of the West African westerly jet in Sahel rainfall variations. J Clim 25:2880–2896CrossRefGoogle Scholar
  26. Ramanathan V, Downey P (1986) A nonisothermal emissivity and absorptivity formulation for water-vapor. J Geophys Res-Atmos 91:8649–8666CrossRefGoogle Scholar
  27. Saha S et al (2010) The NCEP climate forecast system reanalysis. Bull Am Meteorol Soc 91:1015–1057CrossRefGoogle Scholar
  28. Solomon S et al (2007) Technical summary. In: Solomon S et al (eds) Climate change 2007 the physical science basis—contribution of working group I to the fourth assessment report of the intergovernmental panel on climate change. Cambridge University Press, CambridgeGoogle Scholar
  29. Steiner AL, Pal JS, Rauscher SA, Bell JL, Diffenbaugh NS, Boone A, Sloan LC, Giorgi F (2009) Land surface coupling in regional climate simulations of the West African monsoon. Clim Dyn 33:869–892CrossRefGoogle Scholar
  30. Stephens GL (1978) Radiation profiles in extended water clouds. 2. Parameterization schemes. J Atmos Sci 35:2123–2132CrossRefGoogle Scholar
  31. Subin ZM, Riley WJ, Jin J, Christianson DS, Torn MS, Kueppers LM (2011) Ecosystem Feedbacks to climate change in california: development, testing, and analysis using a coupled regional atmosphere and land surface model (WRF3-CLM3.5). Earth Interact 15:1–38. doi: 10.1175/2010EI331.1 CrossRefGoogle Scholar
  32. Thorncroft CD, Blackburn M (1999) Maintenance of the African easterly jet. Q J R Meteorol Soc 125:763–786Google Scholar
  33. Vizy EK, Cook KH (2002) Development and application of a mesoscale climate model for the tropics: influence of sea surface temperature anomalies on the West African monsoon. J Geophys Res Atmos 107:4023CrossRefGoogle Scholar
  34. Wang SY, Gillies RR (2011) Observed change in Sahel rainfall, circulations, African easterly waves, and Atlantic hurricanes since 1979. Int J Geophys 259529Google Scholar
  35. Whitlock CH et al (1995) First global WCRP shortwave surface radiation budget dataset. Bull Am Meteorol Soc 76:905–922CrossRefGoogle Scholar
  36. Wild M, Cechet R (2002) Downward longwave radiation in general circulation models: a case study at a semi-arid continental site. Tellus Ser A Dyn Meteorol Oceanogr 54:330–337CrossRefGoogle Scholar
  37. Willmott CJ, Robeson SM, Feddema JJ (1994) Estimating continental and terrestrial precipitation averages from rain-gauge networks. Int J Climatol 14:403–414CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Utah Climate CenterUtah State UniversityLoganUSA
  2. 2.Department of Plants, Soils, and ClimateUtah State UniversityLoganUSA
  3. 3.Department of Watershed SciencesUtah State UniversityLoganUSA

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