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Intraseasonal variability in the far-east pacific: investigation of the role of air–sea coupling in a regional coupled model

Intraseasonal variability in the far-east pacific: investigation of the role of air–sea coupling in a regional coupled model,10.1007/s00382-010-0786-2

Intraseasonal variability in the far-east pacific: investigation of the role of air–sea coupling in a regional coupled model   (Citations: 4)
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Intraseasonal variability in the eastern Pacific warm pool in summer is studied, using a regional ocean–atmosphere model, a linear baroclinic model (LBM), and satellite observations. The atmospheric component of the model is forced by lateral boundary conditions from reanalysis data. The aim is to quantify the importance to atmospheric deep convection of local air–sea coupling. In particular, the effect of sea surface temperature (SST) anomalies on surface heat fluxes is examined. Intraseasonal (20–90 day) east Pacific warm-pool zonal wind and outgoing longwave radiation (OLR) variability in the regional coupled model are correlated at 0.8 and 0.6 with observations, respectively, significant at the 99% confidence level. The strength of the intraseasonal variability in the coupled model, as measured by the variance of outgoing longwave radiation, is close in magnitude to that observed, but with a maximum located about 10° further west. East Pacific warm pool intraseasonal convection and winds agree in phase with those from observations, suggesting that remote forcing at the boundaries associated with the Madden–Julian oscillation determines the phase of intraseasonal convection in the east Pacific warm pool. When the ocean model component is replaced by weekly reanalysis SST in an atmosphere-only experiment, there is a slight improvement in the location of the highest OLR variance. Further sensitivity experiments with the regional atmosphere-only model in which intraseasonal SST variability is removed indicate that convective variability has only a weak dependence on the SST variability, but a stronger dependence on the climatological mean SST distribution. A scaling analysis confirms that wind speed anomalies give a much larger contribution to the intraseasonal evaporation signal than SST anomalies, in both model and observations. A LBM is used to show that local feedbacks would serve to amplify intraseasonal convection and the large-scale circulation. Further, Hovmöller diagrams reveal that whereas a significant dynamic intraseasonal signal enters the model domain from the west, the strong deep convection mostly arises within the domain. Taken together, the regional and linear model results suggest that in this region remote forcing and local convection–circulation feedbacks are both important to the intraseasonal variability, but ocean–atmosphere coupling has only a small effect. Possible mechanisms of remote forcing are discussed.
Journal: Climate Dynamics - CLIM DYNAM , vol. 36, no. 5, pp. 867-890, 2011
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    • ...To support inferences on convective activity provided by the OLR in both the tropical and subtropical oceans, we also analyzed the 1° × 1° Global Precipitation Climatology Project (GPCP) precipitation data, the 2.5° × 2.5° Climate Prediction Center (CPC) merged analysis of precipitation (CMAP) product, and 0.7° × 0.7° European Center for Medium‐Range Weather Forecasts (ECMWF) Reanalysis (ERA) Interim ...

    Wei Yuet al. Observations of eastward propagation of atmospheric intraseasonal osci...

    • ...By using a regional coupled model, a recent study by Small et al. (2011) illustrates that both the MJO forcing from the west and local convection‐circulation feedbacks are important for the ISV over the EPAC, whereas the air-sea coupling only plays a minor role...
    • ...This is in agreement with regional model results by Small et al. (2011), which suggest that the phase of the ISV over the EPAC is determined by remote forcing associated with the MJO...
    • ...EPAC is closely linked to the eastward propagating ISV signals from the Indian Ocean/WPAC, which is largely consistent with previous regional model results that the phase of the ISV over the EPAC is determined by remote forcing associated with the MJO (Small et al. 2011)...

    Xianan Jianget al. Simulation of the intraseasonal variability over the Eastern Pacific I...

    • ...Maloney and Kiehl 2002a; Small et al. 2010)...

    Luke P. Van RoekelEricet al. Mixed layer modeling in the East Pacific warm pool during 2002

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