CMA results (v1.1 and v1.2)

This page evaluates CKD models generated by the "CMA" tool. Note that these models are only intended for use with present-day greenhouse-gas concentrations, so have not been evaluated in alternative climate scenarios.

Longwave (v1.1)

CMA version 1.1 uses the CKDMIP "narrow" band structure (13 bands) in the longwave and the model evaluated has a total of 124 g-points.  The performance of broadband heating rates and fluxes in present-day conditions is as follows, evaluated using line-by-line calculations on the 50 CKDMIP "Evaluation-1" profiles:

The evaluation in each of the 13 bands is shown here (in order of increasing wavenumber):

or equivalently plotted in terms of the error in each band:

We see that the Outgoing Longwave Radiation (OLR) is overestimated by on average 4 W m-2.  This bias has contributions from multiple bands so appears not to be associated with errors in representing one particular gas. The OLR error increases with the absolute OLR, which may provide a clue as to the cause of this bias.

Shortwave (v1.2)

CMA version 1.2 uses the CKDMIP "narrow" band structure (13 bands) in the shortwave and a total of 140 g-points. The evaluation of present-day fluxes and heating rates is here:

and the evaluation in individual bands is here:

or equivalently plotted in terms of errors compared to line-by-line:

The main error is an overestimate of surface downwelling by around 5 W m-2, on average, which also leads to too much reflection upwards. This has contributions from several bands; for example, there appears to be too little tropospheric absorption in the 250-2600 cm-1 band, which could be due to water vapour absorption being underestimated. There may also be scope for refining the treatment of Rayleigh scattering in the 12850-16000 cm-1 band.