Impact of Tropical Cyclone Activity Observed by the TCI (2015) and SHOUT Field Campaigns and Explained by Cloud-Resolving Model Simulations

Detailed calculations of environmental energy transfer to the Upper Troposphere – Lower Stratosphere (UTLS) that occurred with 4 tropical cyclones during the 2015-2016 Atlantic and East Pacific Hurricane seasons are made using cloud resolving model simulations. Results are verified against in-situ field observations of the tropical cyclone outflow taken by high-flying aircraft that were conducted by the TCI and SHOUT field and campaigns. Results demonstrate that nearly all of the dry entropy gained by latent heating is transferred into UTLS isentropic layers having entropy equal to the moist entropy created at the base of the cyclone eye wall in the form of increased mass within those layers. The work expended to lift and expand the air as it moves up into those outflow layers increases the amount of suspended potential energy in those layers due to their increased mass. Anomalously low Potential vorticity (PV), a byproduct of the vertical profile TC latent heating and increased isentropic thickness of the outflow, is pumped into these same isentropic layers where it has important effects on the TC and away from the TC. For instance, the increased isentropic thickness gives rise to poleward moving Tropical Plumes in the UTLS for several cases and plumes of low potential PV contained in the tropical atmosphere for other cases. In either case, the reduced PV in these layers provides an environment of reduced inertial resistance to subsequent convection or tropical storm overturning reaching into these layers.