Extended Abstract (84K)16B.1
eastern Pacific Intraseasonal precipitation and SST variations in a GCM coupled to a slab ocean model
Eric D. Maloney, NCAR, Boulder, CO; and J. T. Kiehl
Coupling the NCAR CCM3.6 with relaxed Arakawa-Schubert convection to a slab ocean model (SOM) improves the simulation of eastern Pacific convection during a composite June-November intraseasonal oscillation (ISO) lifecycle. Intraseasonal oscillations in the SOM simulation produce convective variability over the tropical northeastern Pacific that is similar to that produced by the observed Madden-Julian oscillation (MJO). A composite ISO lifecycle in the SOM simulation exhibits stronger, more coherent, and more widespread eastern Pacific warm pool convective anomalies than in a control simulation using climatological SSTs. Competing convective forcings over land and ocean make eastern Pacific low-level circulation anomalies more complex in the SOM simulation than in the observed MJO.
Off-equatorial eastern Pacific SST variations of more than 0.6 degC are associated with the June-November SOM simulation ISO. These variations are similar to those observed with the MJO. No significant equatorial east Pacific SST anomalies occur in the model, supporting the contention that observed MJO SST anomalies on the equator are caused by ocean dynamics. Positive off-equatorial SOM simulation SST anomalies are nearly in phase with enhanced precipitation during significant MJO events, whereas observed SST anomalies lead enhanced precipitation by just under 10 days. Latent heat flux and surface shortwave radiation anomalies are the dominant terms in controlling east Pacific intraseasonal SST in the SOM simulation, and are also the dominant terms controlling intraseasonal SST variations in observations. Positive latent heat flux and shortwave radiation anomalies (positive defined as downward into the ocean) lead enhanced SST by about 10 days during significant ISO events in the SOM simulation.
Supplementary URL: http://www.cgd.ucar.edu/~maloney/som/som.html
Session 16B, Inraseasonal Variability II (Parallel with Sessions 16A and 16C)
Friday, 3 May 2002, 9:00 AM-10:30 AM
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