Recent Developments in the GFDL Extended-Range Forecasting System

• Published in: Journal of the Meteorological Society of Japan Vol. 64A; pp. 359 - 363
• Main Authors: Pierrehumbert, R., Miyakoda, K., Stern, W., Sirutis, J., Ploshay, J.
• Format: Journal Article
• Language: English
• Published: Meteorological Society of Japan 1986
• ISSN: 0026-1165; 2186-9057
• DOI: 10.2151/jmsj1965.64A.0_359

An assessment is made of the areas of focus for improving extended-range forecasting. Two topics currently being researched involve the reduction of systematic error by improving a GCM’s accuracy and the refinement of the transition between the data assimilation phase and the forecasting phase.  Subgrid-scale orographic parameterizations have been the subject of recent model improvement activities. Results are shown for an envelope orography with an N48L9 gridpoint model and using a mountain gravity wave drag scheme with an R42L18 spectral model. In both cases there is an encouraging reduction in the systematic errors.  Proper initialization of tropical features, i. e. 40-50 day waves, may be crucial for extended-range predictions in the extra-tropics as well as the tropics. Using a continuous data assimilation scheme the 40-50 day oscillations in the tropics appear to be well maintained from the assimilation to the forecast phase. However, the assimilation system underestimates precipitation and evaporation rates.