Atmospheric response to Atlantic tropical instability waves in Community Atmosphere Model version 3
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Tropical instability waves (TIWs) are 20 to 40day waves that appear along the sea surface temperature (SST) front of the equatorial cold tongues. In this study, we investigate the atmospheric planetary boundary layer response to TIWinduced SST variations in the tropical Atlantic Ocean using Community Atmosphere Model version 3 (CAM3) developed at the National Center for Atmospheric Research and compare the model simulation with available satellite measurements. CAM3 is used to simulate the response to Atlantic TIWs with T85 and T42 horizontal resolutions forced with daily Tropical Rainfall Measuring Mission microwave imager (TMI) SSTs and T85 horizontal resolution forced with weekly TMI and Reynolds SSTs. All four runs exhibit an atmospheric response to the SST anomalies, but the amplitude of the response is different in each case. The model simulates winds, convergence, columnintegrated water vapor, and precipitation perturbations associated with TIWs that are similar in many respects to the satellite observations. However, the wind convergence and divergence anomalies in the satellite observations are located west of the SST anomalies. In the CAM3 simulations the wind convergence is more in phase with SST anomalies. Differences between the observations and the model simulations appear to be due to both differences in the boundary layer response and differences in the horizontal advection process.
