26th Conference on Hurricanes and Tropical Meteorology


The influence of wind-induced atmosphere-ocean exchange on summertime east Pacific intraseasonal oscillations in the modified NCAR CAM2.0.1

Eric D. Maloney, Oregon State University, Corvallis, OR

Intraseasonal precipitation variability over the northeast Pacific warm pool during June-October in the National Center for Atmospheric Research Community Atmosphere Model 2.0.1 with relaxed Arakawa-Schubert convection is found to be strongly sensitive to wind-induced variations in surface latent heat flux. A control simulation with interactive surface fluxes produces northeast Pacific warm pool intraseasonal wind and precipitation variations that are of similar magnitude and structure to those associated with the observed intraseasonal oscillation (ISO). Periods of low-level westerly intraseasonal wind anomalies are associated with enhanced surface latent heat fluxes and enhanced precipitation, as in observations. Variations in surface wind speed primarily control the surface flux anomalies. A simulation in which eastern north Pacific oceanic latent heat fluxes are set to their climatological values produces intraseasonal precipitation variations that are significantly lower than that in the control simulation and in observations. These results support the observational findings of Maloney and Esbensen, who suggested that wind-induced latent heat flux variability is a significant driver of ISO-related convective variability over the northeast Pacific warm pool during Northern Hemisphere summer.

Summertime eastern north Pacific intraseasonal wind variability does not vary significantly between the control and fixed-evaporation simulations, and may due to a strong coupling between the east Pacific flow and convection over Central America. Such a coupling is not observed. The poor resolution of Central American orography in the model may contribute to this anomalous coupling.

extended abstract  Extended Abstract (532K)

Poster Session 1, Posters
Wednesday, 5 May 2004, 1:30 PM-1:30 PM, Richelieu Room

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