New Approaches to the Parameterization of Gravity-Wave and Flow-Blocking Drag due to Unresolved Mesoscale Orography Guided by Mesoscale Model Predictability Research

2012 ◽  
Author(s):  
Stephen D. Eckermann
Keyword(s):  
Gravity Wave ◽  
Mesoscale Model ◽  
New Approaches

scholarly journals Simulation of Inertia–Gravity Waves in a Poleward-Breaking Rossby Wave

2006 ◽  
Vol 63 (12) ◽  
pp. 3253-3276 ◽  
Author(s):  
Christoph Zülicke ◽  
Dieter Peters
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Rossby Wave ◽  
Rossby Waves ◽  
Mesoscale Model ◽  
Wave Packets ◽  
The Impact ◽  
Jet Streak ◽  
Horizontal Wavelength ◽  
Inertia Gravity Waves

Poleward-breaking Rossby waves often induce an upper-level jet streak over northern Europe. Dominant inertia–gravity wave packets are observed downstream of this jet. The physical processes of their generation and propagation, in such a configuration, are investigated with a mesoscale model. The study is focused on an observational campaign from 17 to 19 December 1999 over northern Germany. Different simulations with the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) have been performed. For a high-resolution process study, three domains were set up that encompass the evolution of Rossby waves and that of inertia–gravity waves. To minimize the impact of model damping, the horizontal and vertical resolution has been adjusted appropriately. With a novel statistical approach, the properties of inertia–gravity wave packets have been estimated. This method uses the horizontal divergence field and takes into account the spatial extension of a wave packet. It avoids the explicit treatment of the background field and works for arbitrary wavelength. Two classes of inertia–gravity waves were found: subsynoptic waves with a horizontal wavelength of about 500 km and mesoscale waves with a horizontal wavelength of about 200 km. The subsynoptic structures were also detected in radiosonde observations during this campaign. The similarity between simulated and observed wavelengths and amplitudes suggests that the simulations can be considered as near realistic. Spontaneous radiation from unbalanced flow is an important process of inertia–gravity wave generation. Synoptic-scale imbalances in the exit region of the upper-tropospheric jet streak were identified with the smoothed cross-stream Lagrangian Rossby number. In a number of simulations with different physics, it was found that the inertia–gravity wave activity was related to the tropospheric jet, orography, and moist convection. The upward propagation of inertia–gravity waves was favored during this event of a poleward-breaking Rossby wave. The presence of the polar vortex induced background winds exceeding the critical line. Consequently, the activity of inertia–gravity waves in the lower stratosphere increased by an order of magnitude during the case study. The successful simulation of the complex processes of generation and propagation showed the important role of poleward Rossby wave breaking for the appearance of inertia–gravity waves in the midlatitudes.

scholarly journals Gravity wave reflection and its influence on the consistency of temperature- and wind-based momentum fluxes simulated above Typhoon Ewiniar

2012 ◽  
Vol 12 (2) ◽  
pp. 6263-6282 ◽  
Author(s):  
Y.-H. Kim ◽  
H.-Y. Chun ◽  
P. Preusse ◽  
M. Ern ◽  
S.-Y. Kim
Keyword(s):  
Gravity Wave ◽  
Momentum Flux ◽  
Wave Reflection ◽  
Mesoscale Model ◽  
Satellite Measurements ◽  
Stability Change ◽  
Propagating Waves ◽  
Momentum Fluxes ◽  
Flux Profile

Abstract. For a case study of Typhoon Ewiniar performed with a mesoscale model, we compare stratospheric gravity wave (GW) momentum flux determined from temperature variances by applying GW polarization relations and by assuming upward propagating waves with GW momentum flux calculated from model winds, which is considered as a reference. The temperature-based momentum-flux profile exhibits positive biases which fluctuate with altitude and have peak values of 17–39% at 20–40 km. We found that this deviation stems from the interference between upward and downward propagating waves. The downward propagating GWs are due mainly to partial reflections of upward propagating waves at altitudes where the background wind and stability change with height. When the upward and downward propagating waves are decomposed and their momentum fluxes are calculated separately from temperature perturbations, the fraction of the momentum flux arising from the downward propagating waves is about 4.5–8.2%. The net momentum flux of upward and downward propagating GWs agrees well with the reference from the model wind perturbations. Global distributions of GW momentum flux can be deduced from satellite measurements of temperatures also employing GW polarization relations but using different analysis methods. The implications of this study for the GW momentum-flux observations from satellites are discussed.

scholarly journals Boundary Layer Convergence Induced by Strong Winds across a Midlatitude SST Front*

2014 ◽  
Vol 27 (4) ◽  
pp. 1698-1718 ◽  
Author(s):  
Thomas Kilpatrick ◽  
Niklas Schneider ◽  
Bo Qiu
Keyword(s):  
Boundary Layer ◽  
Gravity Wave ◽  
Mesoscale Model ◽  
Vertical Motion ◽  
Internal Gravity Wave ◽  
Front Surface ◽  
Internal Boundary Layer ◽  
Internal Boundary ◽  
Free Atmosphere ◽  
Sst Front

Abstract Recent studies indicate that the influence of midlatitude SST fronts extends through the marine atmospheric boundary layer (MABL) into the free atmosphere, with implications for climate variability. To better understand the mechanisms of this ocean-to-atmosphere influence, SST-induced MABL convergence is explored here with the Weather Research and Forecasting mesoscale model in an idealized, dry, two-dimensional configuration, for winds crossing from cold to warm SST and from warm to cold SST. For strong cross-front winds, O(10 m s−1), changes in the turbulent mixing and MABL depth across the SST front lead to MABL depth-integrated convergence in the cold-to-warm case and depth-integrated divergence in the warm-to-cold case. The turbulent stress divergence term changes over a shorter length scale than the pressure gradient and Coriolis terms, such that the MABL response directly above the SST front is governed by nonrotating, internal boundary layer–like physics, which are consistent with the vertical mixing mechanism. An important consequence is that the increment in the cross-front surface stress diagnoses the vertical motion at the top of the MABL. These physics are at variance with some previously proposed SST frontal MABL models in which pressure adjustments determine the MABL convergence. The SST-induced MABL convergence results in vertical motion that excites a stationary internal gravity wave in the free atmosphere, analogous to a mountain wave. For a 15 m s−1 cross-front wind, the gravity wave forced by an SST increase of 3°C over 200 km is comparable to that forced by an 80-m change in topography.

scholarly journals Gravity wave reflection and its influence on the consistency of temperature- and wind-based momentum fluxes simulated above Typhoon Ewiniar

2012 ◽  
Vol 12 (22) ◽  
pp. 10787-10795 ◽  
Author(s):  
Y.-H. Kim ◽  
H.-Y. Chun ◽  
P. Preusse ◽  
M. Ern ◽  
S.-Y. Kim
Keyword(s):  
Gravity Wave ◽  
Momentum Flux ◽  
Wave Reflection ◽  
Mesoscale Model ◽  
Background Wind ◽  
Stability Change ◽  
Propagating Waves ◽  
Momentum Fluxes ◽  
Flux Profile

Abstract. For a case study of Typhoon Ewiniar performed with a mesoscale model, we compare stratospheric gravity wave (GW) momentum flux determined from temperature variances by applying GW polarization relations and by assuming upward propagating waves, with GW momentum flux calculated from model winds which is considered as a reference. The temperature-based momentum-flux profile exhibits positive biases relative to the reference, which fluctuate significantly with altitude. The vertically-averaged magnitude of the positive biases is about 14% of the reference momentum flux. We found that this deviation from the reference stems from the interference between upward and downward propagating waves. The downward propagating GWs are due mainly to partial reflections of upward propagating waves at altitudes where the background wind and stability change with height. When the upward and downward propagating waves are decomposed and their momentum fluxes are calculated separately from temperature perturbations, the fraction of the momentum flux arising from the downward propagating waves is about 4.5–8.2% of that from the upward propagating waves. The net momentum flux of upward and downward propagating GWs agrees well with the reference from the model wind perturbations. The implications of this study for the GW momentum-flux observations from satellites are discussed.

The Impact of Coastal Boundaries and Small Hills on the Precipitation Distribution across Southern Connecticut and Long Island, New York

2007 ◽  
Vol 135 (3) ◽  
pp. 933-954 ◽  
Author(s):  
Brian A. Colle ◽  
Sandra E. Yuter
Keyword(s):  
New York ◽  
Gravity Wave ◽  
Doppler Radar ◽  
Mesoscale Model ◽  
Long Island ◽  
Heavy Precipitation ◽  
Radar Data ◽  
Surface Precipitation ◽  
The Impact ◽  
Precipitation Enhancement

Abstract The modification of precipitation by the coastal land areas of Long Island (LI), New York, and southern Connecticut (CT) is examined for an extratropical cyclone over the northeast United States on 1 December 2004, which produced strong southerly flow (15–30 m s−1) below 900 mb and heavy precipitation over LI. The differential surface roughness at the coast and the hills of LI (30–80 m) and southern CT (100–250 m) enhanced the surface precipitation by 30%–50% over these regions compared with the nearby water region of LI Sound. The three-dimensional precipitation structures are shown using composite Weather Surveillance Radar-1988 Doppler radar data interpolated to a Cartesian grid, which is compared with a 4-km simulation using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5). As the low-level stratification and flow increased at low levels, the MM5 produced a terrain-forced gravity wave over LI and CT upward through 6 km MSL. Precipitation enhancement (2–3 dBZ) occurred from the surface upward to around the freezing level (3 km MSL) across central LI and southern CT, while there was a localized precipitation minimum over LI Sound. A factor separation on a few sensitivity MM5 runs was performed to isolate the impact of small hills and differential friction across the LI coastline. Both the hills and frictional effects have similar contributions to the total precipitation enhancement and the vertical circulations below 3 km. The hills of LI enhanced the gravity wave circulations slightly more than the differential friction above 3 km, while there was little flow and precipitation interaction between the hills and differential friction. A sensitivity simulation without an ice/snow cloud above 3 km MSL revealed that the seeder-feeder process enhanced surface precipitation by about a factor of 4.

scholarly journals Inertia gravity waves in the upper troposphere during the MaCWAVE winter campaign – Part II: Radar investigations and modelling studies

2006 ◽  
Vol 24 (11) ◽  
pp. 2863-2875 ◽  
Author(s):  
A. Serafimovich ◽  
Ch. Zülicke ◽  
P. Hoffmann ◽  
D. Peters ◽  
P. Dalin ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Mesoscale Model ◽  
Wave Activity ◽  
Model Data ◽  
Vhf Radar ◽  
Upper Troposphere ◽  
Radar Measurements ◽  
Horizontal Momentum ◽  
Inertia Gravity Waves

Abstract. We present an experimental and modelling study of a strong gravity wave event in the upper troposphere/lower stratosphere near the Scandinavian mountain ridge. Continuous VHF radar measurements during the MaCWAVE rocket and ground-based measurement campaign were performed at the Norwegian Andoya Rocket Range (ARR) near Andenes (69.3° N, 16° E) in January 2003. Detailed gravity wave investigations based on PSU/NCAR Fifth-Generation Mesoscale Model (MM5) data have been used for comparison with experimentally obtained results. The model data show the presence of a mountain wave and of an inertia gravity wave generated by a jet streak near the tropopause region. Temporal and spatial dependencies of jet induced inertia gravity waves with dominant observed periods of about 13 h and vertical wavelengths of ~4.5–5 km are investigated with wavelet transform applied on radar measurements and model data. The jet induced wave packet is observed to move upstream and downward in the upper troposphere. The model data agree with the experimentally obtained results fairly well. Possible reasons for the observed differences, e.g. in the time of maximum of the wave activity, are discussed. Finally, the vertical fluxes of horizontal momentum are estimated with different methods and provide similar amplitudes. We found indications that the derived positive vertical flux of the horizontal momentum corresponds to the obtained parameters of the jet-induced inertia gravity wave, but only at the periods and heights of the strongest wave activity.

Beyond autism: Challenging unexamined assumptions about social motivation in typical development

2019 ◽  
Vol 42 ◽  
Author(s):  
Karen Bartsch ◽  
David Estes
Keyword(s):  
Social Interest ◽  
Social Motivation ◽  
Typical Development ◽  
Typically Developing ◽  
New Approaches

Abstract In challenging the assumption of autistic social uninterest, Jaswal & Akhtar have opened the door to scrutinizing similar unexamined assumptions embedded in other literatures, such as those on children's typically developing behaviors regarding others’ minds and morals. Extending skeptical analysis to other areas may reveal new approaches for evaluating competing claims regarding social interest in autistic individuals.

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