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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-560
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
30 Aug 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Characterising energy budget variability at a Sahelian site: a test of NWP model behaviour
Anna Mackie1, Paul I. Palmer1,2, and Helen Brindley3 1School of GeoSciences, The University of Edinburgh, Edinburgh, UK
2National Centre for Earth Observation, The University of Edinburgh, Edinburgh, UK
3National Centre for Earth Observation, Imperial College London, London, UK
Abstract. We use observations of surface and top-of-the-atmosphere (TOA) broadband radiation fluxes determined from the Atmospheric Radiation Measurement program Mobile Facility, and GERB/SEVIRI,and a range of meteorological variables, at a site in the Sahel to test the ability of the ECMWF Integrated Forecasting System cycle 43r1 to describe energy budget variability. The model has daily average bias of −12 W m-2 and 18 W m-2 for outgoing longwave and reflected shortwave TOA radiation fluxes, respectively. Using multivariate linear models of observation minus model differences, we attribute radiation flux discrepancies to physical processes, and link surface and TOA fluxes. We find that model biases in surface radiation fluxes are mainly due to a low bias in ice-water path (IWP), poor description of surface albedo, and model-observation differences in surface temperature. At the TOA, the low IWP impacts the amount of reflected shortwave radiation while biases in outgoing longwave radiation are additionally coupled to discrepancies in the surface upwelling longwave flux and atmospheric humidity.

Citation: Mackie, A., Palmer, P. I., and Brindley, H.: Characterising energy budget variability at a Sahelian site: a test of NWP model behaviour, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-560, in review, 2017.
Anna Mackie et al.
Anna Mackie et al.
Anna Mackie et al.

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Short summary
We compare the balance of solar and thermal radiation at the surface and the top-of-the-atmosphere from a forecasting model to observations at a site in Niamey, Niger, in the Sahel. To interpret the energy budgets we examine other factors, such as cloud properties, water vapour and aerosols, which we use to understand the differences between the observation and model. We find that some differences are linked to lack of ice in clouds, underestimated aerosol loading and surface temperatures.
We compare the balance of solar and thermal radiation at the surface and the...
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