Simulation of ENSO-related surface winds in the tropical Pacific by an atmospheric general circulation model forced by observed sea surface temperatures
- Indian Institute of Science, Bangalore (India)
- International Institute for Earth, Environmental and Marine Sciences and Technologies, Trieste (Italy)
The authors present the simulation of the tropical Pacific surface wind variability by a low-resolution (R15 horizontal resolution and 18 vertical levels) version of the Center for Ocean-Land-Atmosphere Interactions, Maryland, general circulation model (GCM) when forced by observed global sea surface temperature. The authors have examined the monthly mean surface winds and precipitation simulated by the model that was integrated from January 1979 to March 1992. Analyses of the climatological annual cycle and interannual variability over the Pacific are presented. The annual means of the simulated zonal and meridional winds agree well with observations. The only appreciable difference is in the region of strong trade winds where the simulated zonal winds are about 15%-20% weaker than observed. The amplitude of the annual harmonics are weaker than observed over the intertropical convergence zone and the South pacific convergence zone regions. The amplitudes of the interannual variation of the simulated zonal and meridional winds are close to those of the observed variation. The first few dominant empirical orthogonal functions (EOF) of the simulated, as well as the observed, monthly mean winds are found to contain a large amount of high-frequency intraseasonal variations. While the statistical properties of the high-frequency modes, such as their amplitude and geographical locations, agree with observations, their detailed time evolution does not. When the data are subjected to a 5-month running-mean filter, the first two dominant EOFs of the simulated winds representing the low-frequency El Nino-Southern Oscillation fluctuations compare quite well with observations. However, the location of the center of the westerly anomalies associated with the warm episodes is simulated about 15{degrees} west of the observed locations. 33 refs., 17 figs., 1 tab.
- OSTI ID:
- 90913
- Journal Information:
- Monthly Weather Review, Vol. 123, Issue 6; Other Information: PBD: Jun 1995
- Country of Publication:
- United States
- Language:
- English
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