Tropical Cyclone Structure and Size across Climates

We examine how the size and structure of tropical cyclones vary in climate simulations that span from the Last Glacial Maximum (LGM) to those with high values of carbon dioxide (CO₂). Storms statistically downscaled with the Coupled Hurricane Intensity Prediction Scheme (CHIPS) have fixed outer radii by construction, but the structure of the inner core winds shows variability with climate: the distribution of the radius of maximum winds is concentrated at values smaller than 80 km in the LGM, but larger inner cores occur more frequently in warmer simulations. In general the radius of maximum winds varies inversely with storm intensity, but storms of all sizes spread to higher latitudes with warming. Tropical cyclones gradually expand into subtropical and middle latitudes as temperatures rise from the LGM to the 20^th century to a warm climate forced with 8-times preindustrial era levels of carbon dioxide. In the hottest case examined (32-times preindustrial era levels of CO₂), tropical cyclones become infrequent at low latitudes but become common in middle and high latitudes as deep convection becomes routinely supported outside the tropics. The distribution of actual intensities follows changes in the potential intensity, which increases with warming before asymptoting when surface temperatures pass ~32^oC as the net infrared flux into the ocean tends to zero under high CO₂ concentrations. We compare these results to the distribution of the sizes, structures, and locations of tropical cyclones explicitly simulated and resolved in paleoclimate GCM simulations.