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Author : Kevin E. Trenberth
Release : 1972
Genre :
Kind : eBook
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Book Synopsis The Dynamic Coupling of the Stratosphere with the Troposphere and Sudden Stratospheric Warmings by : Kevin E. Trenberth
Download or read book The Dynamic Coupling of the Stratosphere with the Troposphere and Sudden Stratospheric Warmings written by Kevin E. Trenberth. This book was released on 1972. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Huang Yang
Release : 2015
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Book Synopsis Dynamic Coupling and Chemical Transport Between the Stratosphere and the Troposphere by : Huang Yang
Download or read book Dynamic Coupling and Chemical Transport Between the Stratosphere and the Troposphere written by Huang Yang. This book was released on 2015. Available in PDF, EPUB and Kindle. Book excerpt: Although the stratosphere and troposphere are separately different in many aspects (thermal structure, dynamic circulation, chemical composition and etc.), studies in recent decades have indicated a much stronger connection between these two distinct layers. Dynamically, the stratospheric circulation is driven by the eddies that are dominantly generated in the troposphere, whereas the troospheric circulation varies, in some ocassion, mostly due to the circulation and eddy perturbation originated in the stratosphere. The exchange and transport between the two layers, on the other hand, tend to alter the chemical compostion on both sides, and hence induce subsequent influences on the chemistry and radiation within the two layers. In this study, we further enrich the understanding on the connection between the stratosphere and troposphere by examining their dynamic coupling and chemical exchange. We first investigate the dynamic impact from the troposphere to the stratosphere by examining the role of tropical sea surface temperature (SST). By designing several idealized SST forcing simulations in an aqua-planet model, we find that the zonal distribution of SST perturbations has a major impact on the vertical and meridional structure of the BDC as compared with other SST characteristics. Zonally localized SST heatings tend to generate a shallow acceleration of the stratospheric residual circulation, whereas SST heatings with a zonally symmetric structure tend to produce a deep strengthening of the stratospheric residual circulation. The shallow versus deep strengthening of the stratospheric residual circulation change has been linked to wave propagation and dissipation in the subtropical lower stratosphere rather than wave generation in the troposphere. The dynamic impact from the stratosphere to the troposphere is then discussed by focusing on the downward influence of polar stratospheric ozone depletion. Three possible mechanisms are examined in an idealized dry model: the polar stratospheric cooling impacts tropospheric synoptic eddies via (a) the direct influences on the lower stratospheric synoptic eddies, (b) the planetary wave-induced residual circulation, and (c) the planetary eddy - synoptic eddy nonlinear interaction. It is argued that the planetary wave-induced residual circulation is not the dominant mechanism, and that the planetary eddies and further nonlinear interaction with synoptic eddies are more likely the key to the downward influence of the ozone depletion-like cooling. Last, the chemical interaction between the stratosphere and troposphere is explored by quantifying the stratosphere-troposphere exchange (STE) of ozone. The specified dynamics (SD) version of the Whole Atmosphere Community Climate Model (WACCM) is used to estimate the ozone STE along different isentropic surfaces (isentropic ozone STE herein). Net troposphere-to-stratosphere ozone STE is diagnosed in the subtropics (350 K - 380 K), while net stratosphereto-troposphere ozone STE is diagnosed in the extratropics (280 K - 350 K), with different magnitudes and seasonalities over different isentropic (meridional) regions. Potential vorticity (PV) sources induced by both differential diabatic heating and isentropic mixing contribute to the diagnosed isentropic ozone STE flux, but the latter is slightly larger. Moreover, results in the SD-WACCM are generally consistent with the analysis in a different model, the SD version of the Canadian Middle Atmosphere Model (CMAM), but the SD-CMAM diagnoses a smaller STE flux. This difference is associated with the different extent of isentropic mixing between the two models.
Author : PLUMB
Release : 2013-11-21
Genre : Science
Kind : eBook
Book Rating : 256/5 ( reviews)
Book Synopsis Middle Atmosphere by : PLUMB
Download or read book Middle Atmosphere written by PLUMB. This book was released on 2013-11-21. Available in PDF, EPUB and Kindle. Book excerpt: PAGEOPH, stratosphere, these differences provide us with new evidence, interpretation of which can materially help to advance our understanding of stratospheric dynamics in general. It is now weil established that smaller-scale motions-in particular gravity waves and turbulence-are of fundamental importance in the general circulation of the mesosphere; they seem to be similarly, if less spectacularly, significant in the troposphere, and probably also in the stratosphere. Our understanding of these motions, their effects on the mean circulation and their mutual interactions is progressing rapidly, as is weil illustrated by the papers in this issue; there are reports of observational studies, especially with new instruments such as the Japanese MV radar, reviews of the state of theory, a laboratory study and an analysis of gravity waves and their effects in the high resolution "SKYHI" general circulation model. There are good reasons to suspect that gravity waves may be of crucial significance in making the stratospheric circulation the way it is (modeling experience being one suggestive piece of evidence for this). Direct observational proof has thus far been prevented by the difficulty of making observations of such scales of motion in this region; in one study reported here, falling sphere observations are used to obtain information on the structure and intensity of waves in the upper stratosphere.
Author : K. Mohanakumar
Release : 2008-07-03
Genre : Science
Kind : eBook
Book Rating : 177/5 ( reviews)
Book Synopsis Stratosphere Troposphere Interactions by : K. Mohanakumar
Download or read book Stratosphere Troposphere Interactions written by K. Mohanakumar. This book was released on 2008-07-03. Available in PDF, EPUB and Kindle. Book excerpt: Stratospheric processes play a signi?cant role in regulating the weather and c- mate of the Earth system. Solar radiation, which is the primary source of energy for the tropospheric weather systems, is absorbed by ozone when it passes through the stratosphere, thereby modulating the solar-forcing energy reaching into the t- posphere. The concentrations of the radiatively sensitive greenhouse gases present in the lower atmosphere, such as water vapor, carbon dioxide, and ozone, control the radiation balance of the atmosphere by the two-way interaction between the stratosphere and troposphere. The stratosphere is the transition region which interacts with the weather s- tems in the lower atmosphere and the richly ionized upper atmosphere. Therefore, this part of the atmosphere provides a long list of challenging scienti?c problems of basic nature involving its thermal structure, energetics, composition, dynamics, chemistry, and modeling. The lower stratosphere is very much linked dynamically, radiatively,and chemically with the upper troposphere,even though the temperature characteristics of these regions are different. The stratosphere is a region of high stability, rich in ozone and poor in water - por and temperature increases with altitude. The lower stratospheric ozone absorbs the harmful ultraviolet (UV) radiation from the sun and protects life on the Earth. On the other hand, the troposphere has high concentrations of water vapor, is low in ozone, and temperature decreases with altitude. The convective activity is more in the troposphere than in the stratosphere.
Author : Daniela Iris Vera Domeisen
Release : 2012
Genre :
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Book Synopsis Stratosphere - Troposphere Interaction During Stratospheric Sudden Warming Events by : Daniela Iris Vera Domeisen
Download or read book Stratosphere - Troposphere Interaction During Stratospheric Sudden Warming Events written by Daniela Iris Vera Domeisen. This book was released on 2012. Available in PDF, EPUB and Kindle. Book excerpt: The stratosphere and the troposphere exhibit a strong coupling during the winter months. However, the coupling mechanisms between the respective vertical layers are not fully understood. An idealized spectral core dynamical model is utilized in the present study in order to clarify the coupling timing, location and mechanisms. Since the coupling between the winter stratosphere and troposphere is strongly intensified during times of strong stratospheric variability such as stratospheric warmings, these events are simulated in the described model for the study of stratosphere - troposphere coupling, while for comparison the coupling is also assessed for weaker stratospheric variability. While the upward coupling by planetary-scale Rossby waves in the Northern Hemisphere is well understood, the Southern Hemisphere exhibits traveling wave patterns with a weaker impact on the stratospheric ow. However the tropospheric generation mechanism of these waves is not well understood and is investigated in this study. It is found that in the model atmosphere without a zonally asymmetric wave forcing, traveling waves are unable to induce a significant wave ux into the stratosphere. In the absence of synoptic eddy activity, however, the tropospheric ow is baroclinically unstable to planetary-scale waves, and the generated planetary waves are able to propagate into the stratosphere and induce sudden warmings comparable in frequency and strength to the Northern Hemisphere. While baroclinic instability of long waves may be further strengthened by the addition of moisture, the real atmosphere also exhibits strong synoptic eddy activity, and it will have to be further explored if the atmosphere exhibits periods where synoptic eddies are weak enough to allow for baroclinic instability of long waves. In order to further investigate the coupling between the stratosphere and the troposphere, cases of strong coupling are investigated in the analysis of a Northern Hemisphere - like winter atmosphere. A realistic frequency and strength of sudden warmings is obtained using a zonal wave-2 topographic forcing. An angular momentum budget analysis yields that the Eliassen-Palm (EP) flux is closely balanced by the residual circulation dominated by the Coriolis term on a daily basis, while the change in zonal wind is a small residual between these dominant terms. In the stratosphere, the EP flux term and the Coriolis term balance well in time but not exactly in magnitude, yielding a polar stratospheric weakening of the zonal mean wind as observed during stratospheric warmings. In the troposphere, the loss of angular momentum before a sudden warming induces a weak negative annular mode response, which is amplified by the downward propagating signal about three weeks after the sudden warming. The angular momentum budget does not reveal the mechanism of downward influence, but it nevertheless clarifies the momentum balance of the stratosphere - troposphere system, indicating that the effects of the waves and the residual circulation have to be considered at the same time. Since the annular mode response cannot be directly investigated using the angular momentum budget, the annular mode coupling between the stratosphere and the troposphere is further investigated using a statistical approach. The annular mode response is often framed in terms of Empirical Orthogonal Functions (EOFs), but it is here found that for the stratosphere - troposphere system with its strong vertical pressure gradient, EOFs are strongly dependent on the weighting of the data, while Principal Oscillation Patterns (POPs) are considerably less sensitive to an applied weighting while returning the dominant structures of variability. This encourages further research and application of POP modes for the use of stratosphere - troposphere coupling. These findings represent an improvement of the understanding of stratosphere - troposphere coupling and the results are another step in the direction of finding the mechanism of stratosphere - troposphere coupling and the downward influence after the occurrence of a stratospheric sudden warming, which may influence long-term weather prediction in the troposphere.
