Mechanisms of Climate Variability and Change

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Low-frequency variability of the troposphere in the form of near-annular variability will be studied in a non-zonally averaged context. Using reanalysis data products and models, where appropriate, the role of zonal asymmetries of the time-mean state on the maintenance of these anomalies and their transitions will be investigated. The role of large-scale convective heating in driving the zonal wind structure and tropopause temperature in the equatorial region will be investigated using global models. The effect of seasonality, equatorial symmetry and zonal asymmetry on the equatorial zonal wind and tropopause temperature will be investigated in a series of controlled experiments, which will be compared to observations. In addition, the role of the radiative cooling of tropical and subtropical stratiform cloud decks in driving shallow circulations, and their interaction with deep convection will be investigated in a simple modeling context and within the context of climate models that predict convective heating. The interaction of the stratosphere and the troposphere and particularly the role of stratospheric warmings in forcing tropospheric climate will be investigated. This will include modeling studies using the Whole Atmosphere Community Climate Model (WACCM1b) and the Community Climate System Model's current atmospheric component (known as CAM), as well as available observations. The connections to the tropics through stratospheric and tropospheric pathways will be investigated and compared.Broader Impacts:Three graduate students will be supported under this grant. One of them will be from an underrepresented group within the sciences. The work will contribute to the validation and testing of the community climate models supported by NSF, the CAM and the WACCM models. The PI will test the utilization of these models on inexpensive cluster computers and provide guidance to others on how to build and maintain this climate modeling infrastructure in a small group setting. The work has potentially important implications for seasonal forecasting and climate change projections.