Group Longwave Radiation

Allie Jones, Catrin Mills, Andy VanLoocke, Kirstin Gleicher

Scheme DifferencesRRTM

RRTMg (control)-a simplified version of RRTMApproximates radiative transfer with fewer points

Like wider rectangles approximating an integral

CAM 3.0Fewer absorbing gasses and spectral bandsEmissivity and absorptivity updated every 12 hrs

Neglects dependence on T, WV, Ozone Explains lack of diurnal cycle

Not an issue when clouds are present-dominant impact calculated at every call of rad. phys

U-WindCAM

RRTMG

RRTM

V-WindRRTM CAM

RRTMG

W-WindRRTM CAM

RRTMG

TemperatureRRTM

RRTMG

CAM

Temperature Difference Fields

Relative HumidityRRTM

RRTMG

CAM

RH Difference Fields

Surface and TOA Longwave Radiation

Surface Heat Fluxes

TOA and Surface Shortwave Flux

Ground Flux

Conclusions

Little difference in RRTM and RRTMG

CAM shows major differences in RH at top and bottom of atmosphere.Also shows major difference in TOA outgoing LW

radiation