Progress in Use of Parameterized Physics at the National Centers for Environmental Prediction (NCEP)
Abstract
The NCEP operational forecast suite encompasses time scales from hours to one year. Currently, global model resolution ranges from 35 km (weather forecast to 7 days) to 200 km (seasonal forecast). Even with a doubling of computer capability every 18 months (Moore's Law), parameterized convection will be required for many years to come in operational forecast models. Since introduction of a Simplified Arakawa-Schubert (SAS) convective parameterization in 1993, the NCEP Global Forecast System (GFS) has been continually improved both in horizontal and vertical resolution but also in the accuracy and capability of component physical parameterizations. One of the major improvements to the model tropical climate occurred in 2001, when cloud condensate become included as an explicit prognostic variable and was used directly in the radiative transfer calculation. Other major changes in the tropical climate have occurred through upgrades to the Planetary Boundary Layer (PBL) and Longwave Radiation. Over the past 5 years, NCEP has emphasized a strategy of unifying weather and short-term (< 1 year) climate by utilizing a weather model, coupled to the GFDL Modular Ocean Model (MOM), for seasonal prediction, including the ENSO. From an operational viewpoint, the necessity for parameterized physics at NCEP places many requirements on the parameterized physics suite. These include: realistic radiative-convective equilibrium and daily tropical activity (Easterly waves, hurricane cyclogenesis, etc); simulation of the Intraseasonal Oscillation and ENSO, both involving interactions with the underlying ocean; and convergence of parameterized physics solutions to resolved-scale solutions (Jung and Arakawa, 2004). It has been very difficult to understand the impact of individual physical processes, such as cumulus convection, across multiple applications, multiple models and multiple choices of other parameterizations (e.g. radiation, PBL). Substitution of individual parameterizations into other packages has not resulted in increased understanding of the impacts of each parameterization on total diabatic processes. Total physics packages, however, can now be compared more easily using the advanced code restructuring principles incorporated into the Earth System Modeling Framework (ESMF). NCEP's GFS will be ESMF compliant by the summer of 2006, with separate dynamics and physics modules available by the end of 2007. The opportunity to compare various total packages available from the community may result in improved choices for NCEP over the next 5 years.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2006
- Bibcode:
- 2006AGUSM.A52B..01L
- Keywords:
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- 1626 Global climate models (3337;
- 4928);
- 3314 Convective processes