The Efficiency of Upward Wave Propagation Near the Tropopause

2021 ◽  
Author(s):  
Israel Weinberger ◽  
Chaim Garfinkel
Keyword(s):  
Heat Flux ◽  
Wave Propagation ◽  
Inversion Layer ◽  
Vertical Component ◽  
Reanalysis Data ◽  
Extreme Heat ◽  
Index Of Refraction ◽  
Scale Model ◽  
Buoyancy Frequency ◽  
Transmission And Reflection Coefficients

<p>Extreme states of the polar stratospheric vortex are typically followed by anomalous surface circulation. These extreme stratospheric vortex states are in turn often associated with extreme heat flux between the tropopause and 100 hPa. </p><p>The goal of this work is to better understand upward wave propagation between the tropopause and the bottom of the vortex near 100 hPa using both theory and reanalysis data.</p><p>Following Charney and Drazin (1961) we analytically solve a quasi-geostrophic planetary-scale model with three different layers: troposphere, tropopause inversion layer (TIL) and stratosphere. We allow for different buoyancy frequencies in each layer and show the dependence of transmission and reflection coefficients on the buoyancy frequencies, TIL depth and mean-state zonal wind. The dependence of heat flux in the TIL and stratosphere, as well as phase-lines for the wave solution, are presented. This analysis highlights the key role that the TIL and jumps in buoyancy frequency play for upward wave propagation.</p><p>We then use reanalysis data to consider the importance of this effect in observations. Four different specifications of the index of refraction are compared: that derived by Charney and Drazin in 1961, that derived by Matsuno in 1970, and two that relax some of the assumptions used in the derivations of the first two. The Charney and Drazin index of refraction includes terms ignored by Matsuno that are critical for understanding upward wave propagation just above the tropopause in both the climatology and associated with extreme heat flux events. By adding these ignored terms to the Matsuno index of refraction, it is possible to construct a useful tool that describes wave flux immediately above the tropopause and at the same time also describes the role of meridional gradients within the stratosphere. Specifically, a stronger tropopause inversion layer (TIL) tends to restrict upward wave propagation. It is also shown that while only 38% of extreme wave-1 Eliassen-Palm flux vertical component (F<sub>z</sub>) at 100hPa events are preceded by extreme F<sub>z</sub> at 300hPa, there are almost no extreme events at 100hPa in which the anomaly at 300hPa is of opposite sign or very weak.  </p>

scholarly journals The Efficiency of Upward Wave Propagation Near the Tropopause: importance of the form of the refractive index

2021 ◽  
Author(s):  
Israel Weinberger ◽  
Chaim I. Garfinkel ◽  
Ian P. White ◽  
Thomas Birner
Keyword(s):  
Wave Propagation ◽  
Inversion Layer ◽  
Vertical Component ◽  
Index Of Refraction ◽  
Buoyancy Frequency ◽  
Level Data ◽  
Wave Flux ◽  
Drazin Index ◽  
Vertical Gradients

AbstractThe connection between the polar stratospheric vortex and the vertical component of the Eliassen-Palm flux in the lower stratosphere and upper troposphere is examined in model level data from the ERA-5 reanalysis. The particular focus of this work is on the conditions that lead to upward wave propagation between the tropopause and the bottom of the vortex near 100 hPa. The ability of four different versions of the index of refraction to capture this wave propagation are evaluated. The original Charney and Drazin index of refraction includes terms ignored by Matsuno that are shown to be critical for understanding upward wave propagation just above the tropopause in both the climatology and during extreme heat flux events. By adding these terms to the Matsuno index of refraction, it is possible to construct a useful tool that describes wave flux immediately above the tropopause and at the same time also describes the role of meridional variations within the stratosphere. It is shown that a stronger tropopause inversion layer tends to restrict upward wave propagation. It is also shown that while only 38% of extreme wave-1 Eliassen-Palm flux vertical component (Fz) at 100hPa events are preceded by extreme Fz at 300hPa, there are almost no extreme events at 100hPa in which the anomaly at 300hPa is of opposite sign or very weak. Overall, wave propagation near the tropopause is sensitive to vertical gradients in buoyancy frequency, and these vertical gradients may not be accurately captured in models or reanalysis products especially with lower vertical resolutions.

The Efficiency of Upward Wave Propagation Near the Tropopause

2020 ◽  
Author(s):  
Israel Weinberger ◽  
Chaim Garfinkel ◽  
Thomas Birner
Keyword(s):  
Heat Flux ◽  
Wave Propagation ◽  
Index Of Refraction ◽  
Buoyancy Frequency ◽  
Median Percentage ◽  
Weather Forecasts ◽  
The Difference ◽  
The Impact ◽  
Positive Index ◽  
Anomalous Heat

<p>Recent work has highlighted that not all periods with anomalous heat flux at 100hPa were preceded by anomalous heat flux in the troposphere (Birner and Alberts 2017; White et al 2019; Camara et al 2019), and the goal of this work is to understand the factors that govern the efficiency of upward wave propagation near the tropopause. The index of refraction of Matsuno (1970) has been used to offer guidance on the direction of wave propagation within the stratosphere. Specifically, waves are preferentially refracted towards regions with a more positive index of refraction and ducted away from regions in which the index of refraction is more negative. However, the index of refraction was derived under the assumption that buoyancy frequency is constant at all height levels, which is clearly not true near the tropopause. This assumption allowed Matsuno to ignore certain height dependent buoyancy frequency terms, and here we explore the impact of these terms near the tropopause.</p><p>Using the dataset of the European Center for Medium-Range Weather Forecasts Reanalysis version 5 (ERA5) we defined 'transmitting' composites consisting of more efficient upward propagation events between 300hPa and 100hPa. Similarly, periods of less efficient upward propagation events between 300hPa and 100hPa are composited as 'decaying' events. We computed the index of refraction profile using a median, percentage of negative days and the trimmed mean (Wilks 2011), and also consider the terms neglected by Matsuno. We find that  the index of refraction can account for the difference between the decaying and transmitting composite.</p>

Impact of the Horizontal Heat Flux in the Mixed Layer on an Extreme Heat Event in North China: A Case Study

2018 ◽  
Vol 36 (2) ◽  
pp. 133-142 ◽  
Author(s):  
Ying Na ◽  
Riyu Lu ◽  
Bing Lu ◽  
Min Chen ◽  
Shiguang Miao
Keyword(s):  
Heat Flux ◽  
Mixed Layer ◽  
North China ◽  
Extreme Heat ◽  
Extreme Heat Event ◽  
Heat Event

scholarly journals Dynamics of Extreme Stratospheric Negative Heat Flux Events in an Idealized Model

2018 ◽  
Vol 75 (10) ◽  
pp. 3521-3540 ◽  
Author(s):  
Etienne Dunn-Sigouin ◽  
Tiffany Shaw
Keyword(s):  
Heat Flux ◽  
Wave Propagation ◽  
Recent Work ◽  
Wave Interaction ◽  
Higher Order ◽  
Negative Events ◽  
Flow Mechanism ◽  
Mean Flow ◽  
Idealized Model

Recent work has shown that extreme stratospheric wave-1 negative heat flux events couple with the troposphere via an anomalous wave-1 signal. Here, a dry dynamical core model is used to investigate the dynamical mechanisms underlying the events. Ensemble spectral nudging experiments are used to isolate the role of specific dynamical components: 1) the wave-1 precursor, 2) the stratospheric zonal-mean flow, and 3) the higher-order wavenumbers. The negative events are partially reproduced when nudging the wave-1 precursor and the zonal-mean flow whereas they are not reproduced when nudging either separately. Nudging the wave-1 precursor and the higher-order wavenumbers reproduces the events, including the evolution of the stratospheric zonal-mean flow. Mechanism denial experiments, whereby one component is fixed to the climatology and others are nudged to the event evolution, suggest higher-order wavenumbers play a role by modifying the zonal-mean flow and through stratospheric wave–wave interaction. Nudging all tropospheric wave precursors (wave-1 and higher-order wavenumbers) confirms they are the source of the stratospheric waves. Nudging all stratospheric waves reproduces the tropospheric wave-1 signal. Taken together, the experiments suggest the events are consistent with downward wave propagation from the stratosphere to the troposphere and highlight the key role of higher-order wavenumbers.

Analytical Study of Cylindrical P-Wave Propagation across Jointed Rock Masses

2014 ◽  
Vol 988 ◽  
pp. 502-507 ◽  
Author(s):  
Shao Bo Chai ◽  
Jian Chun Li ◽  
Hai Bo Li ◽  
Ya Qun Liu
Keyword(s):  
Wave Propagation ◽  
Rock Joint ◽  
Jointed Rock ◽  
P Wave ◽  
Displacement Discontinuity ◽  
Linear Elastic ◽  
Transmission And Reflection Coefficients ◽  
Conservation Of Momentum ◽  
Elastic Rock ◽  
Transmission And Reflection

According to the displacement discontinuity method and the conservation of momentum at the wave fronts, analysis for cylindrical P-wave propagation across a linear elastic rock joint is carried out. Considering the energy variation for wave propagation in one medium, the wave propagation equation was derived and expressed in an iterative form. The transmission and reflection coefficients are then obtained from the equation. By verification, the results agree very well with those from the existing results.

scholarly journals Influence of Early Winter Upward Wave Activity Flux on Midwinter Circulation in the Stratosphere and Troposphere

2004 ◽  
Vol 17 (22) ◽  
pp. 4443-4452 ◽  
Author(s):  
Alexei Karpetchko ◽  
Grigory Nikulin
Keyword(s):  
Heat Flux ◽  
Reanalysis Data ◽  
Wave Activity ◽  
Heat Fluxes ◽  
Early Winter ◽  
Polar Night ◽  
Wave Refraction ◽  
Eddy Heat Flux ◽  
Wave Flux

Abstract Using NCEP–NCAR reanalysis data the authors show that the November–December averaged stratospheric eddy heat flux is strongly anticorrelated with the January–February averaged eddy heat flux in the midlatitude stratosphere and troposphere. This finding further emphasizes differences between early and midwinter stratospheric wave flux behavior, which has recently been found in long-term variations. Analysis suggests that the intraseasonal anticorrelation of stratospheric heat fluxes results from changes in the upward wave propagation in the troposphere. Stronger (weaker) upward wave fluxes in early winter lead to weaker (stronger) upward wave fluxes from the troposphere during midwinter. Also, enhanced equatorward wave refraction during midwinter (due to the stronger polar night jet) is associated with weak heat flux in the early winter. It is suggested that the effect of enhanced midwinter upward wave flux from the troposphere in the years with weak early winter heat flux overcompensates the effect of increased equatorward wave refraction in midwinter, leading to a net increase of midwinter upward wave fluxes into the stratosphere.

scholarly journals Simulation of Land Surface Climate over China with RegCM4.5: Verification and Analysis

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Minghao Yang ◽  
Ruiting Zuo ◽  
Liqiong Wang ◽  
Xiong Chen
Keyword(s):  
Heat Flux ◽  
Soil Moisture ◽  
Surface Temperature ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Land Surface Temperature ◽  
South China ◽  
Land Surface ◽  
Reanalysis Data ◽  
Surface Evaporation

The ability of RegCM4.5 using land surface scheme CLM4.5 to simulate the physical variables related to land surface state was investigated. The NCEP-NCAR reanalysis data for the period 1964–2003 were used to drive RegCM4.5 to simulate the land surface temperature, precipitation, soil moisture, latent heat flux, and surface evaporation. Based on observations and reanalysis data, a few land surface variables were analyzed over China. The results showed that some seasonal features of land surface temperature in summer and winter as well as its magnitude could be simulated well. The simulation of precipitation was sensitive to region and season. The model could, to a certain degree, simulate the seasonal migration of rainband in East China. The overall spatial distribution of the simulated soil moisture was better in winter than in summer. The simulation of latent heat flux was also better in winter. In summer, the latent heat flux bias mainly arose from surface evaporation bias in Northwest China, and it primarily arose from vegetation evapotranspiration bias in South China. In addition, the large latent heat flux bias in South China during summer was probably due to less precipitation generated in the model and poor representation of vegetation cover in this region.

Higher Order Moments in the Entrainment Zone of Turbulent Penetrative Thermal Convection

1986 ◽  
Vol 108 (2) ◽  
pp. 323-329 ◽  
Author(s):  
R. Kumar ◽  
R. J. Adrian
Keyword(s):  
Heat Flux ◽  
Inversion Layer ◽  
Interfacial Region ◽  
Interfacial Zone ◽  
Stable Layer ◽  
Third Order ◽  
Beam Laser ◽  
Dual Beam ◽  
Entrainment Zone ◽  
Instantaneous Values

In a simulation of the lifting of an atmospheric inversion layer in the laboratory, measurements have been made to understand the dynamics in the interfacial region capped by a stable, linearly stratified layer. Instantaneous values of vertical and horizontal components of velocity have been measured using a two-component dual-beam laser Doppler anemometer. Temperature fluctuations have been made simultaneously. Detailed measurements of all relevant horizontally averaged one-point moments including heat flux and third-order joint vertical velocity–temperature moments have been obtained. The negative heat flux region is well defined in the entrainment zone, and varies in thickness with different stable layer temperature gradients. The entrainment mechanism is probably most important only in the top part of the interfacial zone. The present data supplement data obtained in the atmosphere, and they compare favorably with the existing data in the literature.

scholarly journals Resolution Dependence of Turbulent Structures in Convective Boundary Layer Simulations

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 986 ◽  
Author(s):  
Mary-Jane M. Bopape ◽  
Robert S. Plant ◽  
Omduth Coceal
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Convective Boundary Layer ◽  
Inversion Layer ◽  
Lower Boundary ◽  
Quadrant Analysis ◽  
Turbulent Structures ◽  
Convective Boundary ◽  
Large Eddy ◽  
Lower Boundary Layer

Large-eddy simulations are performed using the U.K. Met Office Large Eddy Model to study the effects of resolution on turbulent structures in a convective boundary layer. A standard Smagorinsky subgrid scheme is used. As the grid length is increased, the diagnosed height of the boundary layer increases, and the horizontally- and temporally-averaged temperature near the surface and in the inversion layer increase. At the highest resolution, quadrant analysis shows that the majority of events in the lower boundary layer are associated with cold descending air, followed by warm ascending air. The largest contribution to the total heat flux is made by warm ascending air, with associated strong thermals. At lower resolutions, the contribution to the heat flux from cold descending air is increased, and that from cold ascending air is reduced in the lower boundary layer; around the inversion layer, however, the contribution from cold ascending air is increased. Calculations of the heating rate show that the differences in cold ascending air are responsible for the warm bias below the boundary layer top in the low resolution simulations. Correlation length and time scales for coherent resolved structures increase with increasing grid coarseness. The results overall suggest that differences in the simulations are due to weaker mixing between thermals and their environment at lower resolutions. Some simple numerical experiments are performed to increase the mixing in the lower resolution simulations and to investigate backscatter. Such simulations are successful at reducing the contribution of cold ascending air to the heat flux just below the inversion, although the effects in the lower boundary layer are weaker.

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