Upscale influence of increased mesoscale heating in extratropical cyclones

We have previously shown that the intensity of individual extratropical cyclones and their aggregate behavior in the North Atlantic stormtrack are strongly sensitive to horizontal resolution. Current GCM resolutions are inadequate for representing mesoscale condensational heating, which plays an important role in cyclogenesis. Here we investigate the upscale effect of this GCM deficiency on the large-scale flow and the implications for a warmer world with increased atmospheric moisture. We use the Weather Research and Forecast (WRF) model configured globally with a high-resolution 2-way nest in the Northern Hemisphere mid-latitudes. Multiple years are simulated both with and without the nest for current and future scenarios. The future scenarios are forced using changes projected by CMIP5 models. Differences in cyclone dynamics develop as mesoscale latent heating is better resolved and the climatological storm tracks respond accordingly. This response is expressed in terms of the Lorenz energy cycle and through eddy statistics. The upscale influences of condensational heating are also shown for the warmer, moister environment. Our results allow for better understanding of potential biases in projections of stormtrack behavior and the role of extratropical cyclones in the general circulation under global warming.