scholarly journals Convective gravity wave propagation and breaking in the stratosphere: comparison between WRF model simulations and lidar data

2015 ◽  
Vol 33 (9) ◽  
pp. 1155-1171 ◽  
Author(s):  
L. Costantino ◽  
P. Heinrich ◽  
N. Mzé ◽  
A. Hauchecorne
Keyword(s):  
Potential Energy ◽  
Gravity Wave ◽  
Drag Force ◽  
Lower Stratosphere ◽  
Lidar Data ◽  
Time Averaging ◽  
Grid Spacing ◽  
Mean Flow ◽  
Energy Propagation ◽  
Vertical Grid

Abstract. In this work we perform numerical simulations of convective gravity waves (GWs), using the WRF (Weather Research and Forecasting) model. We first run an idealized, simplified and highly resolved simulation with model top at 80 km. Below 60 km of altitude, a vertical grid spacing smaller than 1 km is supposed to reliably resolve the effects of GW breaking. An eastward linear wind shear interacts with the GW field generated by a single convective thunderstorm. After 70 min of integration time, averaging within a radius of 300 km from the storm centre, results show that wave breaking in the upper stratosphere is largely dominated by saturation effects, driving an average drag force up to −41 m s−1 day−1. In the lower stratosphere, mean wave drag is positive and equal to 4.4 m s−1 day−1. In a second step, realistic WRF simulations are compared with lidar measurements from the NDACC network (Network for the Detection of Atmospheric Composition Changes) of gravity wave potential energy (Ep) over OHP (Haute-Provence Observatory, southern France). Using a vertical grid spacing smaller than 1 km below 50 km of altitude, WRF seems to reliably reproduce the effect of GW dynamics and capture qualitative aspects of wave momentum and energy propagation and transfer to background mean flow. Averaging within a radius of 120 km from the storm centre, the resulting drag force for the study case (2 h storm) is negative in the higher (−1 m s−1 day−1) and positive in the lower stratosphere (0.23 m s−1 day−1). Vertical structures of simulated potential energy profiles are found to be in good agreement with those measured by lidar. Ep is mostly conserved with altitude in August while, in October, Ep decreases in the upper stratosphere to grow again in the lower mesosphere. On the other hand, the magnitude of simulated wave energy is clearly underestimated with respect to lidar data by about 3–4 times.

scholarly journals Spatial and Temporal Variations of Gravity Wave Parameters. Part I: Intrinsic Frequency, Wavelength, and Vertical Propagation Direction

2005 ◽  
Vol 62 (1) ◽  
pp. 125-142 ◽  
Author(s):  
Ling Wang ◽  
Marvin A. Geller ◽  
M. Joan Alexander
Keyword(s):  
Gravity Wave ◽  
Lower Stratosphere ◽  
Radiosonde Data ◽  
High Latitudes ◽  
Background Wind ◽  
Energy Propagation ◽  
Wind Speeds ◽  
Wave Parameters ◽  
Propagation Effects ◽  
Vertical Propagation

Abstract Five years (1998–2002) of U.S. high vertical resolution radiosonde data are analyzed to derive important gravity wave parameters, such as intrinsic frequencies, vertical and horizontal wavelengths, and vertical propagation directions in the lower stratosphere and troposphere. Intrinsic frequencies ω̂ increase with increasing latitude, with larger values in the troposphere. In the lower stratosphere, ω̂ is higher in winter than in summer, especially at mid- and high latitudes. Intrinsic frequencies divided by the Coriolis parameter f are ∼4 in the troposphere, and ∼2.4–3 in the lower stratosphere. The lower-stratospheric ω̂/f generally decreases weakly with increasing latitude. The latitudinal distributions of the lower-stratospheric ω̂/f are explained largely by the propagation effects. The seasonal variations of ω̂ in the lower stratosphere are found to be related to the variations of the background wind speeds. Dominant vertical wavelengths decrease with increasing latitude in the lower stratosphere, and maximize at midlatitudes (35°–40°N) in the troposphere. They are generally longer in winter than in summer. The variations of the dominant vertical wavelengths are found to be associated with the similar variations in gravity wave energies. Dominant horizontal wavelengths decrease with increasing latitude, with larger values in the lower stratosphere. Approximately 50% of the tropospheric gravity waves show upward energy propagation, whereas there is about 75% upward energy propagation in the lower stratosphere. The lower-stratospheric fraction of upward energy propagation is generally smaller in winter than in summer, especially at mid- and high latitudes. The seasonal variation of upward fraction is likely an artifice due to the analysis method, although a small part of it may be interpreted by the variations in background wind speeds. Results suggest that propagation effects are much more important than source variations for explaining the large-scale time-average properties of waves observed by radiosondes.

scholarly journals Investigating the Spatio-Temporal Distribution of Gravity Wave Potential Energy over the Equatorial Region Using the ERA5 Reanalysis Data

Atmosphere ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 311
Author(s):  
Shih-Sian Yang ◽  
Chen-Jeih Pan ◽  
Uma Das
Keyword(s):  
Potential Energy ◽  
Gravity Wave ◽  
Zonal Wind ◽  
Thermal Structure ◽  
Temporal Distribution ◽  
Energy Coupling ◽  
Equatorial Region ◽  
Mean Flow ◽  
Wave Potential ◽  
Wind Shears

Atmospheric gravity waves play a crucial role in affecting atmospheric circulation, energy transportation, thermal structure, and chemical composition. Using ERA5 temperature data, the present study investigates the tropospheric to the lower mesospheric gravity wave potential energy (EP) over the equatorial region to understand the vertical coupling of the atmosphere. EP is mainly controlled by two factors. The first is zonal wind through wave–mean flow interactions, and thus EP has periodic variations that are correlated to the zonal wind oscillations and enhances around the altitudes of zero-wind shears where the zonal wind reverses. The second is the convections caused by atmospheric circulations and warm oceans, resulting in longitudinal variability in EP. The lower stratospheric and the lower mesospheric EP are negatively correlated. However, warm oceanic conditions can break this wave energy coupling and further enhance the lower mesospheric EP.

Self-Acceleration in the Parameterization of Orographic Gravity Wave Drag

2010 ◽  
Vol 67 (8) ◽  
pp. 2537-2546 ◽  
Author(s):  
John F. Scinocca ◽  
Bruce R. Sutherland
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Wave Train ◽  
Leading Edge ◽  
Wave Theory ◽  
Wave Drag ◽  
Tuning Parameter ◽  
Mean Flow ◽  
Propagating Waves ◽  
The Impact

Abstract A new effect related to the evaluation of momentum deposition in conventional parameterizations of orographic gravity wave drag (GWD) is considered. The effect takes the form of an adjustment to the basic-state wind about which steady-state wave solutions are constructed. The adjustment is conservative and follows from wave–mean flow theory associated with wave transience at the leading edge of the wave train, which sets up the steady solution assumed in such parameterizations. This has been referred to as “self-acceleration” and it is shown to induce a systematic lowering of the elevation of momentum deposition, which depends quadratically on the amplitude of the wave. An expression for the leading-order impact of self-acceleration is derived in terms of a reduction of the critical inverse Froude number Fc, which determines the onset of wave breaking for upwardly propagating waves in orographic GWD schemes. In such schemes Fc is a central tuning parameter and typical values are generally smaller than anticipated from conventional wave theory. Here it is suggested that self-acceleration may provide some of the explanation for why such small values of Fc are required. The impact of Fc on present-day climate is illustrated by simulations of the Canadian Middle Atmosphere Model.

scholarly journals Gravity-wave effects on tracer gases and stratospheric aerosol concentrations during the 2013 ChArMEx campaign

2016 ◽  
Author(s):  
Fabrice Chane Ming ◽  
Damien Vignelles ◽  
Fabrice Jegou ◽  
Gwenael Berthet ◽  
Jean-Batiste Renard ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Lower Stratosphere ◽  
Weather Forecasting ◽  
Stratospheric Aerosol ◽  
Thin Layers ◽  
Vertical Wind ◽  
Specific Humidity ◽  
Small Scale ◽  
Strong Activity ◽  
Dynamical Parameters

Abstract. Coupled balloon-borne observations of Light Optical Aerosol Counter (LOAC), M10 meteorological global positioning system (GPS) sondes, ozonesondes and GPS radio occultation data, are examined to identify gravity-wave (GW) induced fluctuations on tracer gases and on the vertical distribution of stratospheric aerosol concentrations during the 2013 ChArMEx (Chemistry-Aerosol Mediterranean Experiment) campaign. Observations reveal signatures of GWs with short vertical wavelengths less than 4 km in dynamical parameters and tracer constituents which are also correlated with the presence of thin layers of strong local enhancements of aerosol concentrations in the upper troposphere and the lower stratosphere. In particular, this is evident from a case study above Ile du Levant (43.02 °N, 6.46 °E) on 26–29 July 2013. Observations show a strong activity of dominant mesoscale inertia GWs with horizontal and vertical wavelengths of 370–510 km and 2–3 km respectively, and periods of 10–13 h propagating southward at altitudes of 13–20 km and eastward above 20 km during 27–28 July which is also captured by the European Center for Medium range Weather Forecasting (ECMWF) analyses. Ray-tracing experiments indicate the jet-front system to be the source of observed GWs. Simulated vertical profiles of dynamical parameters with large stratospheric vertical wind maximum oscillations ± 40 mms−1 are produced for the dominant mesoscale GW using the simplified linear GW theory. Parcel advection method reveals signatures of GWs in the ozone mixing ratio and the specific humidity. Simulated vertical wind perturbations of the dominant GW and small-scale perturbations of aerosol concentration (aerosol size of 0.2–0.7 μm) are in phase in the lower stratosphere. Present results support the importance of vertical wind perturbations in the GW-aerosol relation. The observed mesoscale GW induces a strong modulation of the amplitude of tracer gases and the stratospheric aerosol background.

scholarly journals Gravity Wave Behavior in Lower Stratosphere During Tropical Cyclones Over the Bay of Bengal

Radio Science ◽  
2018 ◽  
Vol 53 (11) ◽  
pp. 1356-1367 ◽  
Author(s):  
Gargi Rakshit ◽  
Soumyajyoti Jana ◽  
Animesh Maitra
Keyword(s):  
Gravity Wave ◽  
Tropical Cyclones ◽  
Bay Of Bengal ◽  
Lower Stratosphere

scholarly journals The Influence of Sea Surface Temperatures on the Northern Winter Stratosphere: Ensemble Simulations with the MAECHAM5 Model

2006 ◽  
Vol 19 (16) ◽  
pp. 3863-3881 ◽  
Author(s):  
E. Manzini ◽  
M. A. Giorgetta ◽  
M. Esch ◽  
L. Kornblueh ◽  
E. Roeckner
Keyword(s):  
Lower Stratosphere ◽  
Southern Oscillation ◽  
Internal Variability ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Mean Flow ◽  
Enso Events ◽  
Surface Temperatures ◽  
Northern Winter ◽  
Mean State

Abstract The role of interannual variations in sea surface temperatures (SSTs) on the Northern Hemisphere winter polar stratospheric circulation is addressed by means of an ensemble of nine simulations performed with the middle atmosphere configuration of the ECHAM5 model forced with observed SSTs during the 20-yr period from 1980 to 1999. Results are compared to the 40-yr ECMWF Re-Analysis (ERA-40). Three aspects have been considered: the influence of the interannual SST variations on the climatological mean state, the response to El Niño–Southern Oscillation (ENSO) events, and the influence on systematic temperature changes. The strongest influence of SST variations has been found for the warm ENSO events considered. Namely, it has been found that the large-scale pattern associated with the extratropical tropospheric response to the ENSO phenomenon during northern winter enhances the forcing and the vertical propagation into the stratosphere of the quasi-stationary planetary waves emerging from the troposphere. This enhanced planetary wave disturbance thereafter results in a polar warming of a few degrees in the lower stratosphere in late winter and early spring. Consequently, the polar vortex is weakened, and the warm ENSO influence clearly emerges also in the zonal-mean flow. In contrast, the cold ENSO events considered do not appear to have an influence distinguishable from that of internal variability. It is also not straightforward to deduce the influence of the SSTs on the climatological mean state from the simulations performed, because the simulated internal variability of the stratosphere is large, a realistic feature. Moreover, the results of the ensemble of simulations provide weak to negligible evidence for the possibility that SST variations during the two decades considered are substantially contributing to changes in the polar temperature in the winter lower stratosphere.

scholarly journals Impact of Global Warming on Gravity Wave Momentum Flux in the Lower Stratosphere

SOLA ◽  
2005 ◽  
Vol 1 ◽  
pp. 189-192 ◽  
Author(s):  
Shingo Watanabe ◽  
Tatsuya Nagashima ◽  
Seita Emori
Keyword(s):  
Global Warming ◽  
Gravity Wave ◽  
Momentum Flux ◽  
Lower Stratosphere ◽  
Wave Momentum
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