The Effect of Advection On The Distribution of Turbulent Kinetic Energy and Its Generation In Idealized Tropical Cyclone Simulations

Abstract

The distribution of turbulent kinetic energy (TKE) and its budget terms is estimated in simulated tropical cyclones (TCs) of various intensities. Each simulated TC is subject to storm motion, wind shear, and oceanic coupling. Different storm intensities are achieved through different ocean profiles in the model initialization. For each oceanic profile, the atmospheric simulations are performed with and without TKE advection. In all simulations, the TKE is maximized at low levels (i.e., below 1 km) and ∼0.5 km radially inward of the azimuthal-mean radius of maximum wind speed at 1-km height. As in a previous study, the axisymmetric TKE decreases with height in the eyewall, but more abruptly in simulations without TKE advection. The largest TKE budget terms are shear generation and dissipation, though variability in vertical turbulent transport and buoyancy production affect the change in the azimuthal-mean TKE distribution. The general relationships between the TKE budget terms are consistent across different radii, regardless of storm intensity. In terms of the asymmetric distribution in the eyewall, TKE is maximized in the front-left quadrant where the sea surface temperature (SST) is highest and is minimized in the rear-right quadrant where the SST is the lowest. In the category-5 simulation, the height of the TKE maximum varies significantly in the eyewall between quadrants and is between ∼400 m in the rear-right quadrant and ∼1,000 m in the front-left quadrant. When TKE advection is included in the simulations, the maximum eyewall TKE values are downwind compared to the simulations without TKE advection. Key Points The study determines how turbulent kinetic energy (TKE) advection influences tropical cyclone simulations subject to storm motion and ocean coupling The inclusion of TKE advection changes the storm-relative location of maximum TKE and the vertical distribution of TKE in each quadrant The inclusion of TKE advection produces a more realistic distribution of TKE and should be used in closure schemes when possible Plain Language Summary Accurately predicting the distribution and transport of wind energy is important for accurate forecasting of hurricanes by computer models. This study aims to improve our understanding of the energy associated with small-scale eddies and gusts that are known as turbulence. Computer simulations were first analyzed to study the distributions of turbulent energy in the simulated hurricanes. The maximum of this energy is located below 1-km altitude and inward of the region of strongest winds. We examined how hurricane structure and intensity are affected by enabling the model to more realistically transport the turbulence and its energy. This energy transport increases the turbulence in upper levels of the strongest winds while reducing it near the surface. The transport of this energy also pushes the region of maximum turbulent energy downwind of its location without the transport being included. These changes made the simulated turbulent energy field more consistent with observations. This study suggests that enabling the realistic transport of turbulence will improve simulations and forecasts of hurricanes.