Potential Temperature Budget Research Articles

Entrainment Rates and Their Synoptic Dependence on Wind Speed Aloft in California's Central Valley

Daytime atmospheric boundary layer (ABL) dynamics—including potential temperature budgets, water vapour budgets, and entrainment rates—are presented from in situ flight data taken on six afternoons near Fresno in the San Joaquin Valley (SJV) of California during July/August 2016. The flights took place as a part of the California Baseline Ozone Transport Study aimed at investigating transport pathways of air entering the Central Valley from offshore and mixing down to the surface. Midday entrainment velocity estimates ranged from 0.8 to 5.4 cm s−1 and were derived from a combination of continuously determined ABL heights during each flight and model-derived subsidence rates, which averaged -2.0 cm s−1 in the flight region. A strong correlation was found between entrainment velocity (normalized by the convective velocity scale) and an inverse bulk ABL Richardson number, suggesting that wind shear at the ABL top plays a significant role in driving entrainment. Similarly, we found a strong correlation between the entrainment efficiency (the ratio of entrainment to surface heat fluxes with an average of 0.23 ± 0.15) and the wind speed at the ABL top. We explore the synoptic conditions that generate higher winds near the ABL top and propose that warm anomalies in the southern Sierra Nevada mountains promote increased entrainment. Additionally, a method is outlined to estimate turbulence kinetic energy, convective velocity scale (w*), and the surface sensible heat flux in the ABL from a slow, airborne wind measurement system using mixed-layer similarity theory.

A Comparison between Moist and Dry Tropical Cyclones: The Low Effectiveness of Surface Sensible Heat Flux in Storm Intensification

Abstract Recent numerical modeling studies demonstrate that dry tropical cyclones can be stably sustained via a supply of surface sensible heat flux. This raises questions of whether surface sensible heat flux (SHX) and latent heat flux (LHX) have the same effect on the intensity evolution of tropical cyclones. An estimation of equivalent potential temperature budget in the boundary layer shows that LHX leads to larger increase in equivalent potential temperature than SHX even when they possess the same magnitude. By formulating these two kinds of surface heat fluxes with the same mathematical framework, the simulated intensifications of moist and dry tropical cyclones are compared, with the former driven exclusively by LHX and the latter by SHX. Results show significantly larger intensification rates for the tropical cyclone driven by LHX than that by SHX, revealing low effectiveness of SHX in the intensification of tropical cyclones. The diabatic heating in the moist tropical cyclone occurs accompanying the convection, while it is merely pronounced near the surface in the dry tropical cyclone and is decoupled from the dry convection. A new surface pressure tendency equation is proposed, without incorporating the implicit pressure tendency term on the right-hand side. The budget analysis indicates that the SHX is less effective than LHX in lowering surface central pressure and therefore in tropical cyclone intensification. A series of sensitivity experiments suggest that the threshold of energy input required for spinning up a tropical cyclone is lower in the form of LHX than that of SHX.

Intensity Change of Binary Tropical Cyclones (TCs) in Idealized Numerical Simulations: Two Initially Identical Mature TCs

AbstractThis study investigates the intensity change of binary tropical cyclones (TCs) in idealized cloud-resolving simulations. Four simulations of binary interaction between two initially identical mature TCs of about 70 m s−1 with initial separation distance varying from 480 to 840 km are conducted in a quiescent f-plane environment. Results show that two identical TCs finally merge if their initial separation distance is within 600 km. The binary TCs presents two weakening stages (stages 1 and 3) with a quasi-steady evolution (stage 2) in between. Such intensity change of one TC is correlated with the upper-layer vertical wind shear (VWS) associated with the upper-level anticyclone (ULA) of the other TC. The potential temperature budget shows that eddy radial advection of potential temperature induced by large upper-layer VWS contributes to the weakening of the upper-level warm core and thereby the weakening of binary TCs in stage 1. In stage 2, the upper-layer VWS first weakens and then restrengthens with relatively weak magnitude, leading to a quasi-steady intensity evolution. In stage 3, due to the increasing upper-layer VWS, the nonmerging binary TCs weaken again until their separation distance exceeds the local Rossby radius of deformation of the ULA (about 1600 km), which can serve as a dynamical critical distance within which direct interaction can occur between two TCs. In the merging cases, the binary TCs weaken prior to merging because highly asymmetric structure develops as a result of strong horizontal deformation of the inner core. However, the merged system intensifies shortly after merging.

Intensification and Maintenance of a Double Warm-Core Structure in Typhoon Lan (2017) Simulated by a Cloud-Resolving Model

AbstractKnowledge of the development and maintenance processes of double warm cores in tropical cyclones is important for full understanding of the dynamics of storm intensity changes. During its mature stage, Typhoon Lan (2017) had a clear double warm-core structure, which was observed by dropsondes. In this study, to investigate the intensification and maintenance of the double warm-core structure, a numerical simulation of the storm is performed with a cloud-resolving model and verified by dropsonde and satellite observations. A potential temperature budget and backward trajectories are diagnosed to examine intensification and maintenance processes in the simulated eye. The budget analysis indicates that, during the most rapidly intensifying stage, a double warm core is enhanced by axisymmetric subsidence warming in the eye. In the mature stage, upper-core warming is mostly canceled by ventilation due to vertical wind shear, but the lower core continues to warm by asymmetric advection, possibly associated with dynamical instability in the eyewall. The results raise a topic of interest: it is difficult to fully explain the axisymmetric subsidence warming process during the most rapidly intensifying stage by the dynamical response in an axisymmetric balanced vortex. The back-trajectory analysis indicates that the air mass associated with the subsidence is partly induced by inward acceleration in subgradient regions (unbalanced processes) in the eyewall.

The Role of Radiation in Heating the Clear-Air Convective Boundary Layer: Revisiting CASES-97

Using data for 3 days in the Cooperative Atmosphere-Surface Exchange Study 1997 field experiment that are analyzed in LeMone et al. (Boundary-Layer Meteorol 104:1–52, 2002, hereafter L2002), it is shown that direct radiative heating can have a significant role in warming the nearly cloudless fair-weather convective boundary layer (CBL). Radiative heating becomes especially important in the presence of aerosols in the CBL, with a moist layer above the CBL also contributing. Not only does inclusion of radiative heating help “close” their potential-temperature budgets, but it affects entrainment estimates. Combined, radiative heating rates are of the order of 0.2 K h−1, based on calculations using the Rapid-Radiative Transfer Model for general circulation models (RRTMG) code in a single-column version of the Advanced Research Weather Research and Forecasting model and estimates of aerosol heating published in L2002. Our current estimates of clear-air direct radiative heating differ from the estimates in L2002 because the surface skin temperature was not included in the earlier calculations. Upwelling and downwelling longwave radiation computed using the RRTMG code agrees with aircraft measurements within 10–15 W m−2.

Intensity Change of Typhoon Nancy (1961) during Landfall in a Moist Environment over Japan: A Numerical Simulation with Spectral Nudging

Abstract Intensity change of tropical cyclones (TCs) as they make landfall is closely linked to sustained periods of high surface winds and heavy precipitation. Few studies have investigated the intensity change of intense TCs that make landfall in middle latitudes such as Japan because few intense typhoons make landfall in middle latitudes. In this study, a numerical simulation of intense Typhoon Nancy (1961) was used to understand the intensity change that occurred when Nancy made landfall in Japan. A spectral nudging technique was introduced to reduce track errors in the simulation. During landfall, the simulated storm exhibited the salient asymmetric structure and rapid eyewall contraction. A tangential wind budget indicated that the maximum wind speed decreased concurrent with an increase in surface friction and advection associated with low-level asymmetric flows. Detailed evolution of the storm’s warm core was analyzed with a potential temperature budget. In the upper part of the warm core centered at a 12-km height, cooling due to ventilation by asymmetric flows and longwave radiation overcame heating due to condensation and shortwave radiation during the contraction of eyewall clouds. In the lower part of the warm core, adiabatic cooling more than offset warm-air intrusions associated with asymmetric flows and condensational heating. The condensation was supplied by an abundance of moisture due to evaporation from the ocean in the well-developed typhoon based on a moisture budget. Sensitivity experiments revealed that environmental baroclinicity in the midlatitudes, orography, and radiative processes made minor contributions to the weakening. The weakening was instead controlled by inner-core dynamics and interactions with land surfaces.

Evolution of the Warm-Core Structure during the Eyewall Replacement Cycle in a Numerically Simulated Tropical Cyclone

Abstract This study examines the evolution of the warm-core structure during the secondary eyewall formation (SEF) and the subsequent eyewall replacement cycle (ERC) in a numerically simulated tropical cyclone (TC) under idealized conditions. Results show that prior to the SEF, the TC exhibited a double warm-core structure centered in the middle and upper troposphere in the eye region, and as the storm intensified with a rapid outward expansion of tangential winds, the warm core strengthened and a secondary off-center warm ring developed between 8- and 16-km heights near the outer edge of the eye. During the SEF, both the upper-level warm core and the secondary off-center warm ring rapidly strengthened. As the secondary eyewall intensified and contracted and the primary eyewall weakened and dissipated, the off-center warm ring extended inward and merged with the inner warm core to form a warm core typical of a single-eyewall TC. Results from the azimuthal-mean potential temperature budget indicate that the warming in the eye is due to subsidence and the warming above 14-km height outside the eye is largely contributed by radial warm advection in the outflow. The development of the off-center warm ring is largely due to the subsidence warming near the inner edge of the primary eyewall and in the moat area and the warming by diabatic heating in the upper part of the inner eyewall below 14-km height. Further analysis indicates that the eddy advection also played some role in the warming above 12-km height in the upper troposphere.

Convection, latent heating and potential temperature budget in the rapidly intensifying Typhoon Mujigae (2015)

AbstractBased on a 72‐hr simulation of the rapidly intensifying Typhoon Mujigae (2015), the spatiotemporal evolutions of various inner‐core convections and the associated latent heating (LH) features were investigated. Results showed two interesting turning points from the pre‐rapid intensification (RI) stage to RI onset. One was a change from convective–stratiform mixed precipitation to a convective precipitation (CP)‐dominant trend, while the other happened inside the CP. As the major contributor to LH, during the CP, the dramatic increase and radially inward movement of deep convection and associated LH release from −4 to −2 hr relative to RI, provided some useful clues for predicting the RI of a tropical cyclone (TC). But how do distinct convections act on the RI of a TC? From the potential temperature budget and flow vector intuitive display, there were upper‐ and lower‐level warm cores, fed by the centripetal transport from deep‐convection‐related LH sources and lower‐level radial inflow of weak‐to‐moderate convection‐associated LH sources. The former brought about higher heating efficiency, embodied by a higher rate (2.5 times greater) of pressure decline during RI. Thus, by comparing the LH effects of diverse convections on warm‐core formation, and the role of the warm core in the RI of a TC, the link between various convections and TC intensification can be established.

Effect of the Eyewall Cold Pool on the Inner Rainband of a Tropical Cyclone

AbstractThe low‐level cold pool just under a tropical cyclone eyewall and its effect on the formation of inner rainbands are studied, through idealized convection‐permitting simulations. Analysis of the potential temperature budget indicates that the formation of the eyewall cold pool (ECP) results from the evaporation of eyewall rainfall. The ECP is a barrier to boundary layer inflow, which results in clear convergence and vertical updraft at its outer edge. A budget analysis of the vertical motion tendency also indicates that the sum of the buoyancy and vertical pressure gradient terms makes a large contribution to the vertical updraft at the outer edge of the ECP. This then promotes the formation of convection cells and an inner rainband. Two sensitivity experiments further verify that the intensity of the ECP‐triggered inner rainbands is positively correlated with the magnitude of the radial gradient of potential temperature at the outer edge of the ECP.

Structure and Maintenance Mechanism of Long-Lived Concentric Eyewalls Associated with Simulated Typhoon Bolaven (2012)

Abstract Typhoons with long-lived concentric eyewalls (CEs) are more intense than those with short-lived CEs. It is important for more accurate prediction of typhoon intensity to understand the maintenance mechanism of the long-lived CEs. To study the mechanism of the long-term maintenance of CEs, a numerical experiment of Typhoon Bolaven (2012) is performed using a nonhydrostatic model with full physics. Two aspects of the maintenance of simulated CEs are investigated: the maintenance of the inner eyewall and the contraction of the outer eyewall. To examine the maintenance of the inner eyewall, the equivalent potential temperature budget and air parcel trajectories of the simulated inner eyewall are calculated. The results show that the entropy supply to the inner eyewall is sufficient to maintain the inner eyewall after secondary eyewall formation (SEF). During the early period after SEF, entropy is supplied by an axisymmetric inflow, and later it is supplied by nonaxisymmetric flows of the outer eyewall. To examine the contraction of the outer eyewall, the potential vorticity (PV) budget of the outer eyewall is diagnosed. The result reveals that the negative contribution to the contraction of the outer PV peak (i.e., the outer eyewall) in the early period is the negative PV generation due to axisymmetric advection and diabatic heating just inside of the outer PV peak. In the later period, the negative PV generation due to nonaxisymmetric structure is important for the prevention of contraction. The present study reveals that the structure of the outer eyewall plays important roles in the maintenance of long-lived CEs.

The inner core thermodynamics of the tropical cyclone boundary layer

Although considerable progress has been made in understanding the inner-core dynamics of the tropical cyclone boundary layer (TCBL), our knowledge of the inner-core thermodynamics of the TCBL remains limited. In this study, the inner-core budgets of potential temperature (\(\theta\)), specific humidity (q), and reversible equivalent potential temperature (\(\theta _\mathrm{e}\)) are examined using a high-resolution multilevel boundary layer model. The potential temperature budgets show that the heat energy is dominated by latent heat release in the eyewall, evaporative cooling along the outer edge of the eyewall, and upward surface fluxes of sensible and latent heat from the underlying warm ocean. It is shown that the vertical \(\theta\) advection overcompensates the sum of radial advective warming from the boundary layer outflow jet and latent heating for the development of cooling in the eyewall within the TCBL. The moisture budgets show the dominant upward transport of moisture in the eyewall updrafts, partly by the boundary-layer outflow jet from the bottom eye region, so that the eyewall remains nearly saturated. The \(\theta _\mathrm{e}\) budgets reveal that the TCBL is maintained thermodynamically by the upward surface flux of higher-\(\theta _\mathrm{e}\) air from the underlying warm ocean, the radial transport of low-\(\theta _\mathrm{e}\) air from the outer regions of the TCBL, and the dry adiabatic cooling associated by eyewall updrafts. These results underscore the significance of vertical motion and the location of the boundary layer outflow jet in maintaining the inner core thermal structure of the TCBL.

The summer diurnal cycle of coastal cloudiness over west Iberia using Meteosat/SEVIRI and a WRF regional climate model simulation

The summer time cloud diurnal cycle over western Iberia is analysed here using a satellite climate data record of fractional cloud cover based on 9 years of Meteosat Second Generation observations which is distributed by the EUMETSAT's Climate Monitoring Satellite Applications Facility. These observations were complemented with a corresponding mean cloud diurnal cycle using SYNOP reports on six locations over the studied domain. It is shown that the main coastal mountain range separates regions that are characterized by two very different cloud regimes: stratocumulus-topped boundary layer convection dominates the region towards the coast and continental cumulus convection dominates the region to the east of these mountains. To explain the observed variability, a long-term regional climate model [Weather Research and Forecasting model (WRF)] simulation over Iberia was used. A comparison of the observations against model output for the common period between observations and simulation shows that although the model generally underestimates cloudiness, it is able to represent the diurnal cycle in a realistic manner. It is shown that the observed cloud diurnal evolution is linked to the thermal circulations generated by the land-sea contrast and orography. The extent to which the cloud deck penetrates inland is closely related to the coastal orography: although smaller hills tend to enhance cloudiness, larger mountains block the progression of the marine boundary layer further inland, as it behaves as a density current. Larger mountains also produce katabatic flow and a rather strong subsidence aloft during the night. The warming due to this subsidence helps the blocking of the cloud deck as it is partially responsible for evaporating clouds, as shown by a potential temperature budget analysis.

On the Warm Core of a Tropical Cyclone Formed near the Tropopause

Abstract On the basis of numerical results of a three-dimensional model diagnosed using balance dynamics, a mechanism by which the upper-level warm core of tropical cyclones (TCs) forms is proposed. The numerical results reveal that an upper-level warm core develops when TCs intensify just prior to reaching the mature stage. Potential temperature budget analysis reveals that for the tendency of potential temperature, the azimuthal-mean component of advection is dominant at the upper level of the eye at the mature stage. Sawyer–Eliassen diagnosis shows that tendencies due to forced flow by diabatic heating and diffusion of tangential wind are dominant in the eye and are negatively correlated to each other. The distributions of the diabatic heating in the simulated TC are not peculiar. Therefore, it is unlikely that the heating distribution itself is the primary cause of the flow from the lower stratosphere. The analyses of forced circulations of idealized vortices show that the upper-level subsidence is enhanced in the eye when the vortex is sufficiently tall to penetrate the statically stable stratosphere. This result is deduced because the stronger inertial stability extends the response to the heating of the lower stratosphere and causes upper-level adiabatic warming. Therefore, the upper-level warm core emerges if angular momentum is transported into the lower stratosphere due to processes such as convective bursts. The present analysis suggests that TCs can be even stronger than that expected by theories in which the TC vortex is confined in the troposphere.

Contributions of Surface Sensible Heat Fluxes to Tropical Cyclone. Part I: Evolution of Tropical Cyclone Intensity and Structure

Abstract The contributions of surface sensible heat fluxes (SHX) to the evolution of tropical cyclone (TC) intensity and structure are examined in this study by conducting cloud-resolving simulations. Results suggest that although the peak values of SHX could account for nearly 30% of those of the total surface latent and sensible heat fluxes, the impact of SHX on TC intensification is nonetheless not distinct. However, the TC size shows great sensitivity to the SHX that the storm is shrunk by over 20% after removing the SHX. A potential temperature budget analysis indicates that the adiabatic cooling accompanying the radial inflow is largely balanced by the transfer of sensible heat fluxes rather than the entrainment of subsiding air from aloft. If there is upward transfer of SHX from underlying ocean so that the near-surface potential temperature decreases upward, the SHX will play a vital role; instead, if the upward SHX are absent so that the potential temperature increases upward near the surface, the downward sensible heat fluxes become the dominant contributor to warm the inflow air. The changes in TC size are found to be primarily caused by the rainband activities. The SHX help maintain high convective available potential energy as well as the cold pool feature outside the eyewall, thus being crucial for the growth of outer rainbands. If without upward transport of SHX, the outer-rainband activities could be largely suppressed, thereby leading to a decrease of the TC size.

Cold‐pool formation in a narrow valley

AbstractA numerical model simulation of the formation of a cold pool within a narrow valley during a clear calm night is presented. The results are compared with measurements made during the COLd air Pooling EXperiment (COLPEX). It is demonstrated that the model provides a realistic simulation of the observed cold pool. The cold pool begins to form approximately 1.5 hours before sunset, when the near‐surface air within the valley starts to cool more rapidly than the air on the surrounding hills. The model potential temperature budget is used to determine which physical processes are most important for the evolution of the cold pool. The results show that sheltering provided by the valley causes a turbulent heat flux divergence over the lowest 5 m above the valley floor, which is large compared with the other terms in the budget. This causes relatively rapid cooling of the air adjacent to the ground. On the surrounding hills the turbulent heat flux divergence is larger than in the valley, but the enhanced cooling this provides is approximately balanced by an almost equally large warming tendency from advection. The net effect of these two terms is small compared with that in the valley and therefore the cooling rate is smaller. Above 5 m, the cooling in the valley is dominated by local transport of cold air away from the surface into the interior valley atmosphere.

How Does the Eye Warm? Part I: A Potential Temperature Budget Analysis of an Idealized Tropical Cyclone

Abstract In this first part of a two-part study, the mechanisms that accomplish the warming in the eye of tropical cyclones are investigated through a potential temperature budget analysis of an idealized simulation. The spatial structure of warming varies substantially with time. During rapid intensification (RI), the warming is maximized at midlevels, and as a consequence, the perturbation temperature is always maximized in this region. At the start of RI, total advection of potential temperature is the only significant term contributing to warming the eye. However, for a substantial portion of RI, the region of most rapid warming actually undergoes mean ascent. The net advective warming is shown to be a result of eddy radial advection of potential temperature, dominated by a wavenumber-1 feature that is likely due to a dynamic instability. At a sufficient intensity, mean vertical advective warming becomes concentrated in a narrow zone just inward of the eyewall. In agreement with prior studies, this advective tendency is largely canceled by diabatic cooling. Subgrid-scale horizontal diffusion of potential temperature plays a surprisingly large role in the maintenance of the warm-core structure, and when the storm is intense, yields a negative tendency that can be of the same magnitude as advective warming.

Mechanism of Concentric Eyewall Replacement Cycles and Associated Intensity Change*

Abstract To understand the mechanisms responsible for the secondary eyewall replacement cycles and associated intensity changes in intense tropical cyclones (TCs), two numerical experiments are conducted in this study with the Weather Research and Forecasting (WRF) model. In the experiments, identical initial conditions and model parameters are utilized except that the concentration of ice particles is enhanced in the sensitivity run. With enhanced ice concentrations, it is found that the secondary eyewall forms at an increased radius, the time required for eyewall replacement is extended, and the intensity fluctuation is relatively large. The enhanced concentrations of ice particles at the upper tropospheric outflow layer produces a noticeable subsidence region (moat) surrounding the primary eyewall. The presence of the moat forces the secondary eyewall to form at a relatively large radius. The axisymmetric equivalent potential temperature budget analysis reveals that the demise of the inner eyewall is primarily due to the interception of the boundary layer inflow supply of entropy by the outer convective ring, whereas the advection of low entropy air from the middle levels to the boundary inflow layers in the moat is not essential. The interception process becomes inefficient when the secondary eyewall is at a large radius; hence, the corresponding eyewall replacement is slow. After the demise of the inner eyewall, the outer eyewall has to maintain a warm core not only in the previous eye, but also in the moat. The presence of low equivalent potential temperature air in the moat results in the significant weakening of storm intensity. The results found here suggest that monitoring the features of the moat and the outer eyewall region can provide a clue for the prediction of TC intensity change associated with eyewall replacement.

Precipitating convection in cold air: Virtual potential temperature structure

AbstractSimulations of precipitating convection are used to illustrate the importance of the turbulent kinetic energy (TKE) budget in determining the virtual potential‐temperature structure of the convecting atmosphere. Two sets of simulations are presented: in one the surface temperature was increased to simulate cold air flowing over a warmer surface and in the second a cooling profile, representing cold‐air advection, was imposed. It is shown that the terms in the TKE budgets for both sets of simulations scale in the same way, but that the non‐dimensional profiles are different. It is suggested that this is associated with the effects of sublimation of ice.It is shown that the magnitudes of the transport and precipitation terms in the virtual potential temperature budget are determined by the scaling of the TKE budget. Some implications of these results for parametrizations of moist convection are discussed. Copyright © 2007 Royal Meteorological Society

Spatial evolution of foehn flows in the Rhine Valley area: quantification using high resolution simulations

The Rhine valley was one target area chosen during the Mesoscale Alpine Programme (MAP) field experiment to study Foehn flows. The dense data set available has allowed the computation and validation of high resolution simulations. This paper quantifies the distribution of the Foehn flow between the different valleys for different simulated cases. Mass fluxes are computed inside the valley at different stages of Foehn life time. The part played in the penetration of the Foehn to the ground by the presence of a cold air mass in the valley is highlighted. The computation of the potential temperature budget for one case shows that advection and turbulence are the two main physical processes involved in the evolution rate of potential temperature.

Abyssal Mixing in the Brazil Basin*

One of the major objectives of the Deep Basin Experiment, a component of the World Ocean Circulation Experiment, was to quantify the intensity and spatial distribution of deep vertical mixing within the Brazil Basin. In this study, basin-averaged estimates of deep vertical mixing rates are calculated using two independent methodologies and datasets: 1) vertical fluxes are derived from large-scale temperature and density budgets using direct measurements of deep flow through passages connecting the Brazil Basin to surrounding basins and a comprehensive hydrographic dataset within the basin interior and 2) vertical mixing rates are estimated from finescale bathymetry and hydrographic data using a functional relationship between turbulent dissipation and bathymetric roughness, deduced from localized measurements of ocean microstructure obtained during the Deep Basin Experiment. The space‐time mean estimates of vertical mixing diffusivities across representative surfaces within the Antarctic Bottom Water layer fell in the range ; 1‐5(3 1024 m2 s 21) and were indistinguishable k from each other within the estimation uncertainties. The mixing rates inferred from potential temperature budgets update, and are consistent with, earlier estimates that were based on less data. Mixing rates inferred from budgets bounded by neutral surfaces are not significantly different from the former. This implies that lateral eddy fluxes along isopycnals are not important in the potential temperature budgets, at least within the large estimation uncertainties. Unresolved processes, such as cabbeling and low frequency variability, which complicate inference of mixing from large-scale budgets, have been considered. The agreement between diffusivity estimates based on a modeled relationship between bathymetric roughness and turbulent dissipation, with those inferred from large-scale budgets, provides independent confirmation that the mixing rates have been accurately quantified.