High accuracy radiation observation as performed within the Baseline Surface Radiation network (BSRN) enables detailed evaluation of our knowledge on radiation transfer in the atmosphere as laid down in atmospheric radiation models. Since 2004 a BSRN site is run at Cabauw.
In an earlier study (Wang et al. (2009) it was shown that a state of the art model simulates the surface flux of short wave incoming radiation for a clear sky correct within the uncertainty of the observations.
Clear-sky evaluation. (a) Scatterplot of DAK simulations versus BSRN measurements of direct irradiance for
72 clear-sky cases (left panel) and differences between DAK simulations and BSRN measurements of
direct irradiance (right panel). (b) The same as in (a) but for diffuse irradiance. © The same as
in (a) but for global irradiance.
In a recent study Wang et al. (2011) show that also for a cloudy atmosphere a satisfactory comparison between model and the observations is possible. For a case with water clouds and total cloud cover the short wave incoming radiation at the surface was simulated with the Doubling-Adding KNMI radiation transport model (DAK) and compared with radiation measured with the Pyranometer of the BSRN Cabauw site. Cloud water path, the most important cloud parameter for this study, was measured with a microwave radiometer (HATPRO). The figure shows that the DAK model and the BSRN observations give nearly equal values.
Cloudy sky evaluation. Time series of the simulated (Gsim) and measured (Gmeas) global irradiances and the differences DG = Gsim - Gmeas (right y-axis) for all the selected cases. (b) Scatter density plot of simulated and measured global irradiances for all the selected cases. The color indicates the number of the cases on a logarithmic scale. The dashed line is the one-to-one line.
References
Wang, P., W.H. Knap, P. Kuipers Munneke and P. Stammes, Clear-sky shortwave radiative closure for the Cabauw Baseline Surface Radiation Network site, the Netherlands
J. Geophys. Res., 2009, 114, doi:10.1029/2009JD011978.
Wang, P., W. H. Knap, and P. Stammes (2011), Cloudy-sky shortwave radiative closure for a Baseline Surface Radiation Network site, J. Geophys. Res., doi:10.1029/2010JD015141, in press: http://www.agu.org/journals/jd/papersinpress.shtml#id2010JD015141
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