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Public Data used in the manuscript: The Effect of Advection on the Three Dimensional Distribution of Turbulent Kinetic Energy and its Generation in Idealized Tropical Cyclone Simulations. The data in this repository is for the four runs analyzed the manuscript: CAT5-WA, CAT5-NA, CAT1-WA, CAT1-NA. CAT5 represents the category-5 simulations and CAT-1 represents the category-1 simulations. -WA represents simulations with TKE advection and -NA represents simulations without TKE advection turned on. All the simulations run for 6 days and an individual NETCDF file of post-processed relevant variables is made for every half day. The first 12 hours per day are noted under the file extension “_P1” and the second 12 hours per day are noted under the file extension “_P2”. That means there are 12 files per simulation for a total of 48 files. Each file is gziped for space. The total space of the uncompressed files is about ~875 GB. Only data from the innermost domain is shown which is solely what the manuscript analyzes. The variables in each file are: heights: interpolated heights for all of the 4-D variables u_east: zonal wind speed v_north: meridional wind speed w_up: vertical wind speed tke: turbulent kinetic energy tke_shear: shear budget term of TKE tke_buoy: buoyancy budget term of TKE tke_diss: dissipation budget term of TKE tke_wt: vertical transport budget term of TKE dtke: change in TKE between time steps the_advect: calculated advection of TKE Psfc: surface pressure Pressure: full pressure field u10: zonal wind speed at 10-m altitude v10: meridional wind speed at 10-m altitude reflectivity: simulated radar reflectivity Temperature: air temperature Theta_e: air equivalent potential temperature (θe) sst: sea surface temperature ocean_temperature: full ocean temperature profile ocean_levels: ocean vertical levels latentHF: latent heat flux sensibleHF: sensible heat flu

On the hyperbolicity of the bulk air-sea heat flux functions: Insights into the efficiency of air-sea moisture disequilibrium for tropical cyclone intensification

Sea-to-air heat fluxes are the energy source for tropical cyclone (TC) development and maintenance. In the bulk aerodynamic formulas, these fluxes are a function of surface wind speed U10 and air-sea temperature and moisture disequilibrium (ΔT and Δq, respectively). Although many studies have explained TC intensification through the mutual dependence between increasing U10 and increasing sea-to-air heat fluxes, recent studies have found that TC intensification can occur through deep convective vortex structures that obtain their local buoyancy from sea-to-air moisture fluxes, even under conditions of relatively low wind. Herein, a new perspective on the bulk aerodynamic formulas is introduced to evaluate the relative contribution of wind-driven (U10) and thermodynamically driven (ΔT and Δq) ocean heat uptake. Previously unnoticed salient properties of these formulas, reported here, are as follows: 1) these functions are hyperbolic and 2) increasing Δq is an efficient mechanism for enhancing the fluxes. This new perspective was used to investigate surface heat fluxes in six TCs during phases of steady-state intensity (SS), slow intensification (SI), and rapid intensification (RI). A capping of wind-driven heat uptake was found during periods of SS, SI, and RI. Compensation by larger values of Δq . 5 gkg-1 at moderate values of U10 led to intense inner-core moisture fluxes of greater than 600Wm22 during RI. Peak values in Δq preferentially occurred over oceanic regimes with higher sea surface temperature (SST) and upper-ocean heat content. Thus, increasing SST and Δq is a very effective way to increase surface heat fluxes-this can easily be achieved as a TC moves over deeper warm oceanic regimes

The Relationship between Spatial Variations in the Structure of Convective Bursts and Tropical Cyclone Intensification as Determined by Airborne Doppler Radar

The relationship between radial and azimuthal variations in the composite characteristics of convective bursts (CBs), that is, regions of the most intense upward motion in tropical cyclones (TCs), and TC intensity change is examined using NOAA P-3 tail Doppler radar. Aircraft passes collected over a 13-yr period are examined in a coordinate system rotated relative to the deep-layer vertical wind shear vector and normalized by the low-level radius of maximum winds (RMW). The characteristics of CBs are investigated to determine how the radial and azimuthal variations of their structures are related to hurricane intensity change. In general, CBs have elevated reflectivity just below the updraft axis, enhanced tangential wind below and radially outward of the updraft, enhanced vorticity near the updraft, and divergent radial flow at the top of the updraft. When examining CB structure by shear-relative quadrant, the downshear-right (upshear left) region has updrafts at the lowest (highest) altitudes and weakest (strongest) magnitudes. When further stratifying by intensity change, the greatest differences are seen upshear. Intensifying storms have updrafts on the upshear side at a higher altitude and stronger magnitude than steady-state storms. This distribution provides a greater projection of diabatic heating onto the azimuthal mean, resulting in a more efficient vortex spinup. For variations based on radial location, CBs located inside the RMW show stronger updrafts at a higher altitude for intensifying storms. Stronger and deeper updrafts inside the RMW can spin up the vortex through greater angular momentum convergence and a more efficient vortex response to the diabatic heating

Downdrafts and the Evolution of Boundary Layer Thermodynamics in Hurricane Earl (2010) before and during Rapid Intensification

Abstract Using a combination of NOAA P-3 aircraft tail Doppler radar, NOAA and NASA dropsondes, and buoy- and drifter-based sea surface temperature data, different types of downdrafts and their influence on boundary layer (BL) thermodynamics are examined in Hurricane Earl (2010) during periods prior to rapid intensification [RI; a 30-kt (15.4 m s−1) increase in intensity over 24 h] and during RI. Before RI, the BL was generally warm and moist. The largest hindrances for intensification are convectively driven downdrafts inside the radius of maximum winds (RMW) and upshear-right quadrant, and vortex-tilt-induced downdrafts outside the RMW in the upshear-left quadrant. Possible mechanisms for overcoming the low entropy (θe) air induced by these downdrafts are BL recovery through air–sea enthalpy fluxes and turbulent mixing by atmospheric eddies. During RI, convective downdrafts of varying strengths in the upshear-left quadrant had differing effects on the low-level entropy and surface heat fluxes. Interestingly, the stronger downdrafts corresponded with maximums in 10-m θe. It is hypothesized that the large amount of evaporation in a strong (>2 m s−1) downdraft underneath a precipitation core can lead to high amounts of near-surface specific humidity. By contrast, weaker downdrafts corresponded with minimums in 10-m θe, likely because they contained lower evaporation rates. Since weak and dry downdrafts require more surface fluxes to recover the low entropy air than strong and moist downdrafts, they are greater hindrances to storm intensification. This study emphasizes how different types of downdrafts are tied to hurricane intensity change through their modification of BL thermodynamics

Thermodynamic Characteristics of Downdrafts in Tropical Cyclones as Seen in Idealized Simulations of Different Intensities

AbstractThe thermodynamic effect of downdrafts on the boundary layer and nearby updrafts are explored in idealized simulations of category-3 and category-5 tropical cyclones (Ideal3 and Ideal5). In Ideal5, downdrafts underneath the eyewall pose no negative thermodynamic influence because of eye-eyewall mixing below 2-km altitude. Additionally, a layer of higher θe between 1 and 2 km altitude associated with low-level outflow that extends 40 km outward from the eyewall region creates a “thermodynamic shield” that prevents negative effects from downdrafts. In Ideal3, parcel trajectories from downdrafts directly underneath the eyewall reveal that low-θe air initially moves radially inward allowing for some recovery in the eye, but still enters eyewall updrafts with a mean θe deficit of 5.2 K. Parcels originating in low-level downdrafts often stay below 400 m for over an hour and increase their θe by 10-14 K, showing that air-sea enthalpy fluxes cause sufficient energetic recovery. The most thermodynamically unfavorable downdrafts occur ~5 km radially outward from an updraft and transport low-θe mid-tropospheric air towards the inflow layer. Here, the low-θe air entrains into the updraft in less than five minutes with a mean θe deficit of 8.2 K. In general, θe recovery is a function of minimum parcel altitude such that downdrafts with the most negative influence are those entrained into the top of the inflow layer. With both simulated TCs exposed to environmental vertical wind shear, this study underscores that storm structure and individual downdraft characteristics must be considered when discussing paradigms for TC intensity evolution.</jats:p