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ESRL/PSD Seminar Series

Equatorial Rossby and Mixed Rossby-gravity Waves in the Simulated Asian Monsoon

Charlotte DeMott
Atmospheric Sciences, Colorado State University

Abstract


Simulations of the Asian monsoon by three general circulation models (GCMs) using various combinations of 1) a coupled versus prescribed oceans and 2) conventional versus super-parameterized (SP) convection are studied, where super-parameterization refers to an embedded cloud resolving model used to estimate convective tendencies. CCSM is a coupled model with conventionally parameterized convection, SP-CAM is an uncoupled model with super-parameterized convection, and SP-CCSM is a coupled model with super-parameterized convection. SP-CCSM is the only model of the three to reasonably simulate the magnitude and spatial distribution of the eastward-, westward-, and northward-propagating components of the Asian monsoon. SP-CCSM produces a rich variety of tropical waves whose spectral characteristics exhibit unusually close agreement with observations. The simulation of equatorial Rossby (ER) and mixed Rossby-gravity (MRG) waves in the three models leads to a different simulation of the NPISO in each model. All three models exhibit at least some northward propagation for ER waves, but only SP-CCSM produces northward-propagating MRG waves, as is seen in observations. The combination of northwestward- versus southwestward- or westward-propagating ER and MRG waves over the Indian Ocean influences the spatio-temporal structure of the NPISO, and contributes to the differences seen in each model. Influences of the models' different basic state environment, air-sea coupling, and convective treatment and their impact on the simulated will also be considered.


1D-403
Wednesday, February 9
2:00pm

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