Physical Parameterizations for Climate Simulations

Researchers at Atmospheric and Environmental Research (AER) are developing physical parameterizations to contribute to the overall improvement of climate and weather prediction. This includes the application of improved thermal and solar radiative transfer, as well as investigations concerning enhancements in the simulation of convective processes in climate models.

AER has experience with a wide range of global climate models and numerical weather prediction (NWP) models, and we have collaborated with many dynamical modeling centers around the world to improve and to validate simulations of Earth’s climate and weather.

Improved Radiation Modeling

With funding from the U.S. Department of Energy, AER has developed the highly accurate and efficient radiative transfer code RRTMG for application to global models.

The accuracy of RRTMG is verified through comparison to AER’s reference radiation code LBLRTM, which is directly validated with atmospheric measurements provided by high-quality spectral measurements from satellite-, aircraft- and ground-based instruments.

Further information on RRTMG and all of AER’s radiation models is available at the AER radiative transfer web site.

Application to Climate and Weather Simulations

RRTMG is currently in operational use in numerous climate and weather models around the world including:

  • NCAR Community Atmosphere Model (CAM5)
  • NCAR Community Earth System Model (CESM1)
  • European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) and the ERA-40 Reanalysis
  • National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) weather forecast model
  • NCEP Climate Forecast System (CFS)
  • Max Planck Institute (Germany) ECHAM5 climate model
  • China Meteorological Administration (CMA) Global/Regional Assimilation and Prediction System (GRAPES)
  • NCEP Rapid Update Cycle (RUC) forecast model
  • National Center for Atmospheric Research (NCAR) Weather Research and Forecasting (WRF-ARW) model
  • Laboratory for Dynamical Meteorology (France) LMDZ climate model
  • Meteo-France Meso-NH meso-scale atmospheric model

Improved Convection Modeling

With funding from DOE, NSF and MIT, AER scientists have collaborated to investigate the impact of the MIT convection and cloud scheme in the NCAR CAM climate model. This research has demonstrated that the new convection parameterization improves the simulation of the diurnal cycle of convection over land areas in the CAM model.

Climate and Weather Model Validation

AER research funded by NASA and DOE has utilized surface and satellite measurements to verify the accuracy of climate and weather models in the context of the improved radiation parameterization with a focus on the simulation of water vapor, which is the most important greenhouse gas in the troposphere.

AER scientists have used spectral radiance measurements from the NASA Atmospheric Infrared Sounder (AIRS) instrument on board the Earth Observing System (EOS) Aqua satellite to evaluate the simulation of temperature and water vapor in the NCAR CAM climate model. Direct comparison of the radiances predicted by the model to those observed by AIRS in the thermal spectral regions dominated by water vapor absorption provides a means of assessing the simulation of water vapor in the climate model at the high level of detail provided by spectral measurements.

In another study, a multi-year time series of surface radiative fluxes and other atmospheric properties measured by a DOE climate program are being used at AER to evaluate radiative fluxes and to validate forecasts of surface temperature and other properties in the Weather Research and Forecasting (WRF) regional model.

To learn more about the development and application of improved physical parameterizations for global models, please contact us.