How important is the isothermal expansion effect in elevating equivalent potential temperature in the hurricane inner core?

2012 ◽  
Vol 139 (670) ◽  
pp. 70-74 ◽  
Author(s):  
Roger K. Smith ◽  
Michael T. Montgomery
Keyword(s):  
Inner Core ◽  
Potential Temperature ◽  
Equivalent Potential Temperature ◽  
Equivalent Potential ◽  
Isothermal Expansion ◽  
Expansion Effect

The Structure and Evolution of Hurricane Elena (1985). Part I: Symmetric Intensification

2005 ◽  
Vol 133 (10) ◽  
pp. 2905-2921 ◽  
Author(s):  
Kristen L. Corbosiero ◽  
John Molinari ◽  
Michael L. Black
Keyword(s):  
Inner Core ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Relative Vorticity ◽  
Equivalent Potential Temperature ◽  
Constructive Interference ◽  
Wind Maximum ◽  
Radial Gradient ◽  
Equivalent Potential ◽  
Tangential Wind

Abstract One of the most complete aircraft reconnaissance and ground-based radar datasets of a single tropical cyclone was recorded in Hurricane Elena (1985) as it made a slow, 3-day anticyclonic loop in the Gulf of Mexico. Eighty-eight radial legs and 47 vertical incidence scans were collected aboard NOAA WP-3D aircraft, and 1142 ground-based radar scans were made of Elena’s eyewall and inner rainbands as the storm intensified from a disorganized category 2 to an intense category 3 hurricane. This large amount of continuously collected data made it possible to examine changes that occurred in Elena’s inner-core symmetric structure as the storm intensified. On the first day of study, Elena was under the influence of vertical wind shear from an upper-tropospheric trough to the west. The storm was disorganized, with no discernable eyewall and nearly steady values of tangential wind and relative vorticity. Early on the second day of study, a near superposition and constructive interference occurred between the trough and Elena, coincident with upward vertical velocities and the radial gradient of reflectivity becoming concentrated around the 30-km radius. Once an inner wind maximum and eyewall developed, the radius of maximum winds contracted and a sharp localized vorticity maximum emerged, with much lower values on either side. This potentially unstable vorticity profile was accompanied by a maximum in equivalent potential temperature in the eyewall, deeper and stronger inflow out to 24 km from the eyewall, and mean outflow toward the eyewall from the eye. Within 6–12 h, intensification came to an end and Elena began to slowly weaken. Vorticity and equivalent potential temperature at 850 hPa showed indications of prior mixing between the eye and eyewall. During the weakening stage, an outflow jet developed at the eyewall radius. A strong 850-hPa updraft accompanied the outflow jet, yet convection was less active aloft than before. This feature appeared to represent a shallow, outward-sloping updraft channel associated with the spindown of the storm.

scholarly journals Impacts of Evaporation of Rainwater on Tropical Cyclone Structure and Intensity—A Revisit

2015 ◽  
Vol 72 (4) ◽  
pp. 1323-1345 ◽  
Author(s):  
Qingqing Li ◽  
Yuqing Wang ◽  
Yihong Duan
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Potential Temperature ◽  
Outer Core ◽  
Cold Pool ◽  
Equivalent Potential Temperature ◽  
Core Size ◽  
Size Change ◽  
Equivalent Potential ◽  
The Impact

Abstract The impact of evaporation of rainwater on tropical cyclone (TC) intensity and structure is revisited in this study. Evaporative cooling can result in strong downdrafts and produce low–equivalent potential temperature air in the inflow boundary layer, particularly in the region outside the eyewall, significantly suppressing eyewall convection and reducing the final intensity of a TC. Different from earlier findings, results from this study show that outer rainbands still form but are short lived in the absence of evaporation. Evaporation of rainwater is shown to facilitate the formation of outer rainbands indirectly by reducing the cooling due to melting of ice particles outside the inner core, not by the cold-pool dynamics, as previously believed. Only exclusion of evaporation in the eyewall region or the rapid filamentation zone has a very weak effect on the inner-core size change of a TC, whereas how evaporation in the outer core affects the inner-core size depends on how active the inner rainbands are. More (less) active inner rainbands may lead to an increase (a decrease) in the inner-core size.

Combined Effects of Midlevel Dry Air and Vertical Wind Shear on Tropical Cyclone Development. Part II: Radial Ventilation

2020 ◽  
Author(s):  
Joshua J. Alland ◽  
Brian H. Tang ◽  
Kristen L. Corbosiero ◽  
George H. Bryan
Keyword(s):  
Tropical Cyclone ◽  
Wind Shear ◽  
Inner Core ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Equivalent Potential Temperature ◽  
Dry Air ◽  
Equivalent Potential ◽  
Radial Outflow

AbstractThis study demonstrates how midlevel dry air and vertical wind shear (VWS) can modulate tropical cyclone (TC) development via radial ventilation. A suite of experiments was conducted with different combinations of initial midlevel moisture and VWS environments. Two radial ventilation structures are documented. The first structure is positioned in a similar region as rainband activity and downdraft ventilation (documented in Part I) between heights of 0 and 3 km. Parcels associated with this first structure transport low-equivalent potential temperature air inward and downward left-of-shear and upshear to suppress convection. The second structure is associated with the vertical tilt of the vortex and storm-relative flow between heights of 5 and 9 km. Parcels associated with this second structure transport low-relative humidity air inward upshear and right-of-shear to suppress convection. Altogether, the modulating effects of radial ventilation on TC development are the inward transport of low-equivalent potential temperature air, as well as low-level radial outflow upshear, which aid in reducing the areal extent of strong upward motions, thereby reducing the vertical mass flux in the inner core, and stunting TC development.

Combined Effects of Midlevel Dry Air and Vertical Wind Shear on Tropical Cyclone Development. Part I: Downdraft Ventilation

2020 ◽  
Author(s):  
Joshua J. Alland ◽  
Brian H. Tang ◽  
Kristen L. Corbosiero ◽  
George H. Bryan
Keyword(s):  
Tropical Cyclone ◽  
Mass Flux ◽  
Wind Shear ◽  
Inner Core ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Equivalent Potential Temperature ◽  
Areal Extent ◽  
Dry Air ◽  
Equivalent Potential

AbstractThis study examines how midlevel dry air and vertical wind shear (VWS) can modulate tropical cyclone (TC) development via downdraft ventilation. A suite of experiments was conducted with different combinations of initial midlevel moisture and VWS. A strong, positive, linear relationship exists between the low-level vertical mass flux in the inner core and TC intensity. The linear increase in vertical mass flux with intensity is not due to an increased strength of upward motions but, instead, is due to an increased areal extent of strong upward motions (w > 0:5 m s−1). This relationship suggests physical processes that could influence the vertical mass flux, such as downdraft ventilation, influence the intensity of a TC.The azimuthal asymmetry and strength of downdraft ventilation is associated with the vertical tilt of the vortex: downdraft ventilation is located cyclonically downstream from the vertical tilt direction and its strength is associated with the magnitude of the vertical tilt. Importantly, equivalent potential temperature of parcels associated with downdraft ventilation trajectories quickly recovers via surface fluxes in the subcloud layer, but the areal extent of strong upward motions is reduced. Altogether, the modulating effects of downdraft ventilation on TC development are the downward transport of low-equivalent potential temperature, negative-buoyancy air left-of-shear and into the upshear semicircle, as well as low-level radial outflow upshear, which aid in reducing the areal extent of strong upward motions, thereby reducing the vertical mass flux in the inner core, and stunting TC development.

What are the Best Thermodynamic Quantity and Function to Define a Front in Gridded Model Output?

2019 ◽  
Vol 100 (5) ◽  
pp. 873-895 ◽  
Author(s):  
Carl M. Thomas ◽  
David M. Schultz
Keyword(s):  
Real Time ◽  
Potential Temperature ◽  
Thermodynamic Quantity ◽  
Kinematics And Dynamics ◽  
Horizontal Gradient ◽  
Model Output ◽  
Equivalent Potential Temperature ◽  
Thermal Front ◽  
Equivalent Potential ◽  
Definition Of

AbstractFronts can be computed from gridded datasets such as numerical model output and reanalyses, resulting in automated surface frontal charts and climatologies. Defining automated fronts requires quantities (e.g., potential temperature, equivalent potential temperature, wind shifts) and kinematic functions (e.g., gradient, thermal front parameter, and frontogenesis). Which are the most appropriate to use in different applications remains an open question. This question is investigated using two quantities (potential temperature and equivalent potential temperature) and three functions (magnitude of the horizontal gradient, thermal front parameter, and frontogenesis) from both the context of real-time surface analysis and climatologies from 38 years of reanalyses. The strengths of potential temperature to identify fronts are that it represents the thermal gradients and its direct association with the kinematics and dynamics of fronts. Although climatologies using potential temperature show features associated with extratropical cyclones in the storm tracks, climatologies using equivalent potential temperature include moisture gradients within air masses, most notably at low latitudes that are unrelated to the traditional definition of a front, but may be representative of a broader definition of an airmass boundary. These results help to explain previously published frontal climatologies featuring maxima of fronts in the subtropics and tropics. The best function depends upon the purpose of the analysis, but Petterssen frontogenesis is attractive, both for real-time analysis and long-term climatologies, in part because of its link to the kinematics and dynamics of fronts. Finally, this study challenges the conventional definition of a front as an airmass boundary and suggests that a new, dynamically based definition would be useful for some applications.

scholarly journals MSE Minus CAPE is the True Conserved Variable for an Adiabatically Lifted Parcel

2015 ◽  
Vol 72 (9) ◽  
pp. 3639-3646 ◽  
Author(s):  
David M. Romps
Keyword(s):  
Potential Energy ◽  
Thermodynamic Equilibrium ◽  
Convective Available Potential Energy ◽  
Potential Temperature ◽  
Equivalent Potential Temperature ◽  
Moist Static Energy ◽  
Neutral Buoyancy ◽  
Equivalent Potential ◽  
Nonhydrostatic Pressure ◽  
Static Energy

Abstract For an adiabatic parcel convecting up or down through the atmosphere, it is often assumed that its moist static energy (MSE) is conserved. Here, it is shown that the true conserved variable for this process is MSE minus convective available potential energy (CAPE) calculated as the integral of buoyancy from the parcel’s height to its level of neutral buoyancy and that this variable is conserved even when accounting for full moist thermodynamics and nonhydrostatic pressure forces. In the calculation of a dry convecting parcel, conservation of MSE minus CAPE gives the same answer as conservation of entropy and potential temperature, while the use of MSE alone can generate large errors. For a moist parcel, entropy and equivalent potential temperature give the same answer as MSE minus CAPE only if the parcel ascends in thermodynamic equilibrium. If the parcel ascends with a nonisothermal mixed-phase stage, these methods can give significantly different answers for the parcel buoyancy because MSE minus CAPE is conserved, while entropy and equivalent potential temperature are not.

scholarly journals Thermodynamic Analysis of Supercell Rear-Flank Downdrafts from Project ANSWERS

2007 ◽  
Vol 135 (1) ◽  
pp. 240-246 ◽  
Author(s):  
Matthew L. Grzych ◽  
Bruce D. Lee ◽  
Catherine A. Finley
Keyword(s):  
Potential Temperature ◽  
Surface Wind ◽  
Thermodynamic Characteristics ◽  
General Concept ◽  
Equivalent Potential Temperature ◽  
Near Surface ◽  
Project Analysis ◽  
Equivalent Potential ◽  
Virtual Potential Temperature ◽  
Convective Inhibition

Abstract Data collected during Project Analysis of the Near-Surface Wind and Environment along the Rear-flank of Supercells (ANSWERS) provided an opportunity to test recently published associations between rear-flank downdraft (RFD) thermodynamic characteristics and supercell tornadic activity on a set of 10 events from the northern plains. On average, RFDs associated with tornadic supercells had surface equivalent potential temperature and virtual potential temperature values only slightly lower than storm inflow values. RFDs associated with nontornadic supercells had mean group equivalent potential temperature and virtual potential temperature values that were colder relative to storm inflow values than their respective tornadic counterparts. Additionally, the analysis revealed that RFDs associated with tornadic supercells had higher CAPE and lower convective inhibition than the RFDs of nontornadic supercells, on average. The results of this study provide further support for the general concept that a thermodynamic delineation generally exists between the RFDs of tornadic and nontornadic supercells.

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