Analysis of the dynamical links between SST, boundary layer convergence, atmospheric fronts, and precipitation in the North Atlantic storm track

Climate models of standard resolution (e.g. approximately 1°) do not properly resolve phenomena such as atmospheric fronts or ocean mesoscale features. Much of the precipitation in mid-latitudes is associated with atmosphere fronts, particularly in the Extratropical storm tracks. In addition, ocean mesoscale features such as western boundary currents and eddies can induce convergence of the near-surface winds, which is an important factor governing precipitation. Thus, the standard resolution models may be missing some key aspects of processes that drive precipitation, with detrimental impacts on longer range predictability and S2S associated with evolution of the ocean mesoscale and fronts. This project will aim to understand linkages between sea surface temperature (SST), surface convergence and precipitation, using high resolution datasets, and use the results to assess standard resolution model results. Key aspects to this work are how the ocean mesoscale SST affects the atmospheric boundary layer and frontogenesis.
The proposed work falls into four steps: 1. Describe the co-variability of sea surface temperature, wind convergence and precipitation as a function of time and spatial scales from days to season, and from tens of kilometers to basin scale. 2. Investigate the atmospheric boundary layer responses to the ocean mesoscale in the presence of large-scale atmospheric forcing using a recently developed boundary layer model. 3. Characterize surface wind convergence and precipitation associated with atmospheric fronts using objective atmospheric frontal diagnostics, and explore linkages to the ocean mesoscale. 4. Explore how the responses of atmospheric boundary processes, atmospheric fronts, and mesoscale SST features, are related to each other. The state-of-the-art, high-resolution observational and model datasets to be used here include ERA5, CFSR reanalysis, high-resolution CESM, HighResMIP climate models, precipitation analyzed from satellite and in-situ data (IMERG) and scatterometer winds, and a recently developed boundary layer model (Schneider and Qiu 2015).