Thumbnail
Access Restriction
Open

Author Miller, M. J. ♦ Beljaars, A. C. M. ♦ Palmer, T. N.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ENVIRONMENTAL SCIENCES ♦ GENERAL CIRCULATION MODELS ♦ SENSITIVITY ♦ SEAS ♦ EVAPORATION ♦ ANNUAL VARIATIONS ♦ ATMOSPHERIC CIRCULATION ♦ ATMOSPHERIC PRECIPITATIONS ♦ CONVECTION ♦ COUPLING ♦ FORECASTING ♦ HEAT ♦ MOISTURE ♦ OCEANIC CIRCULATION ♦ RAIN ♦ SCALING ♦ SEASONAL VARIATIONS ♦ SIMULATION ♦ STABILITY ♦ TEMPERATURE MONITORING ♦ TROPICAL REGIONS ♦ WIND ♦ ENERGY ♦ ENERGY TRANSFER ♦ HEAT TRANSFER ♦ MASS TRANSFER ♦ MATHEMATICAL MODELS ♦ MONITORING ♦ PHASE TRANSFORMATIONS ♦ SURFACE WATERS ♦ VARIATIONS 540110*
Abstract Stimulated by the results of a simple SST anomaly experiment with the ECMWF forecast model, a study was carried out to examine the model parameterization of evaporation from the tropical oceans. In earlier versions of the model, these fluxes were parameterized with neutral transfer coefficients in accordance with the Chamock relation with equal coefficients for momentum, heat, and moisture. Stability correction was applied using Monin-Obukhov theory. This parameterization resulted in an extremely weak coupling between atmosphere and ocean at wind speeds below 5 m s[sup [minus]1]. The transfer coefficients for heat and moisture have now been modified for low wind speeds to bring them in accordance with the empirical scaling law for free convection. It is shown that these revisions to the transfer coefficients at very low wind speeds (<5 m s[sup [minus]1]) have a dramatic positive impact on almost all aspects of the model's simulation of the tropics. These include much improved seasonal rainfall distributions (with the virtual elimination of a tendency to generate a double ITCZ in both winter and summer), a much improved Indian monsoon circulation, and substantially reduced tropical systematic efforts. The model previously had an easterly bias in the zonal-mean upper tropical troposphenic flow with a corresponding cold bias in the deep tropics; it is shown that the flux revision substantially reduces this. Furthermore, the revision to the fluxes greatly enhances the model's ability to represent interannual and intraseasonal variability (see also the companion paper by Palmer et al.).
ISSN 08948755
Educational Use Research
Learning Resource Type Article
Publisher Date 1992-05-01
Publisher Place United States
Journal Journal of Climate
Volume Number 5
Issue Number 5


Open content in new tab

   Open content in new tab