Extended Abstract (168K)3.9
Investigating the role of air-sea coupling on the Madden Julian Oscillation
Andrew Marshall, Monash University, Clayton, Vic., Australia; and O. Alves, H. Hendon, and D. J. Karoly
The type of convection employed in an atmosphere general circulation model (AGCM) can play a major role in determining the dynamical structure of the model atmosphere. Previous studies have found that a model's ability to simulate the Madden Julian Oscillation (MJO) is improved if the convective parameterisation is closed on buoyancy rather than moisture convergence. Our recent analysis of two versions of the BMRC AGCM (BAM), using moisture convergence and CAPE convection regimes, confirmed these results. The intra-seasonal variability in BAM with CAPE closure showed MJO-like eastward propagating disturbances on intra-seasonal time scales.
Since intra-seasonal SST fluctuations are coherent with the MJO, air-sea interaction may be important for the dynamics of the MJO. Some recent studies have shown that the variability of eastward propagation in GCMs at MJO scales is better when coupled to an ocean model than when forced with observed sea surface temperatures. In our initial stages of determining the role of ocean-atmosphere coupling on the dynamics of the MJO, we coupled the CAPE version of BAM to a simple ocean slab model to show that the simulation of the MJO in BAM was improved compared to the uncoupled case. We also used wavenumber-frequency spectral analysis techniques to investigate the dependence of the MJO on ocean slab layer depth.
Session 3, The Southern Hemisphere oceans and air-sea interactions I
Monday, 24 March 2003, 10:30 AM-3:00 PM
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