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1.
THE ROLE PLAYED BY THE STRATOSPHERE IN GREENHOUSE EFFECT   总被引：1，自引：0，他引：1       下载免费PDF全文
Two one-dimensional radiative-convective models with the same scheme and the different ranges that one is fromsurface to stratopause and the other is from surface to tropopause,have been developed to study the role played by thestratosphere in greenhouse effect.It is shown that the addition of stratospheric response may lead to an increase of 7—50percent in radiative forcing at the tropopause,and an increase of 20—60 percent in surface temperature when the con-centration of the same gas in the two models increases at the same time;and when the same change in radiative forcing atthe tropopause due to the same agent in the two models occurs,the addition of stratospheric response may lead to an in-crease of 5—20 percent in surface temperature;and allowing for the stratospheric adjustment means that the tempera-ture responses to the same flux change due to different causes are in far disagreement.  相似文献   

2.
The radiative impacts of the stratosphere in global warming simulations are investigated using abrupt CO2 quadrupling experiments of the Coupled Model Inter-comparison Project phase 5 (CMIP5), with a focus on stratospheric temperature and water vapor. It is found that the stratospheric temperature change has a robust bullhorn-like zonal-mean pattern due to a strengthening of the stratospheric overturning circulation. This temperature change modifies the zonal mean top-of-the-atmosphere energy balance, but the compensation of the regional effects leads to an insignificant global-mean radiative feedback (?0.02 ± 0.04 W m?2 K?1). The stratospheric water vapor concentration generally increases, which leads to a weak positive global-mean radiative feedback (0.02 ± 0.01 W m?2 K?1). The stratospheric moistening is related to mixing of elevated upper-tropospheric humidity, and, to a lesser extent, to change in tropical tropopause temperature. Our results indicate that the strength of the stratospheric water vapor feedback is noticeably larger in high-top models than in low-top ones. The results here indicate that although its radiative impact as a forcing adjustment is significant, the stratosphere makes a minor contribution to the overall climate feedback in CMIP5 models.  相似文献   

3.
Global aerosol and ozone distributions and their associated radiative forcings were simulated between 1850 and 2100 following a recent historical emission dataset and under the representative concentration pathways (RCP) for the future. These simulations were used in an Earth System Model to account for the changes in both radiatively and chemically active compounds, when simulating the climate evolution. The past negative stratospheric ozone trends result in a negative climate forcing culminating at ?0.15 W m?2 in the 1990s. In the meantime, the tropospheric ozone burden increase generates a positive climate forcing peaking at 0.41 W m?2. The future evolution of ozone strongly depends on the RCP scenario considered. In RCP4.5 and RCP6.0, the evolution of both stratospheric and tropospheric ozone generate relatively weak radiative forcing changes until 2060–2070 followed by a relative 30 % decrease in radiative forcing by 2100. In contrast, RCP8.5 and RCP2.6 model projections exhibit strongly different ozone radiative forcing trajectories. In the RCP2.6 scenario, both effects (stratospheric ozone, a negative forcing, and tropospheric ozone, a positive forcing) decline towards 1950s values while they both get stronger in the RCP8.5 scenario. Over the twentieth century, the evolution of the total aerosol burden is characterized by a strong increase after World War II until the middle of the 1980s followed by a stabilization during the last decade due to the strong decrease in sulfates in OECD countries since the 1970s. The cooling effects reach their maximal values in 1980, with ?0.34 and ?0.28 W m?2 respectively for direct and indirect total radiative forcings. According to the RCP scenarios, the aerosol content, after peaking around 2010, is projected to decline strongly and monotonically during the twenty-first century for the RCP8.5, 4.5 and 2.6 scenarios. While for RCP6.0 the decline occurs later, after peaking around 2050. As a consequence the relative importance of the total cooling effect of aerosols becomes weaker throughout the twenty-first century compared with the positive forcing of greenhouse gases. Nevertheless, both surface ozone and aerosol content show very different regional features depending on the future scenario considered. Hence, in 2050, surface ozone changes vary between ?12 and +12 ppbv over Asia depending on the RCP projection, whereas the regional direct aerosol radiative forcing can locally exceed ?3 W m?2.  相似文献   

4.
Increasing greenhouse gases and likely ozone recovery will be the two most important factors influencing changes in stratospheric temperatures in the 21st century. The radiative effect of increasing greenhouse gases will cause cooling in the stratosphere, while ozone recovery will lead to stratospheric warming. To investigate how stratospheric temperatures change under the two opposite forcings in the 21st century, we use observed ozone and reanalysis data as well as simulation results from four coupled oceanic and atmo- spheric general circulation models （GISS-ER, GFDL-CM20, NCAR-CCSM3, and UKMO-HadCM3） used in the IPCC （Intergovernment Panel for Climate Change） Fourth Assessment Report （AR4）. Observational analysis shows that total column ozone and lower stratospheric temperatures all show increasing in the past 10 years, while middle stratospheric temperatures demonstrate cooling. IPCC AR4 simulations show that greenhouse forcing alone will lead to stratospheric cooling. However, with forcing of both increasing greenhouse gases and ozone recovery, the middle stratosphere will be cooled, while the lower stratosphere will be warmed. Warming magnitudes vary from one model to another. UKMO-HadCM3 generates relatively strong warming for all three greenhouse scenarios, and warming extends to 40 hPa. GFDL-CM20 and NCAR-CCSM3 produce weak warming, and warming mainly exists at lower levels, below about 60 hPa. In addition, we also discuss the effect of temperature changes on ozone recovery.  相似文献   

5.
The European Centre for Medium-Range Weather Forecasts Re-Analysis Interim (ERA-Interim) meteorology and measurements from the Microwave Limb Sounder, High Resolution Dynamics Limb Sounder, and Ozone Monitoring Instrument onboard the Earth Observing System Aura satellite were applied to analyze the dynamical and chemical features of a cutoff low (COL) event over northeast China in early July 2007. The results showed the polar stratospheric origin of an upper-level warm-core cyclone at 100--300 hPa, associated with a funnel-shaped tropopause intruding into the mid-troposphere just above the COL center. The impacts of the stratospheric intrusion on both column ozone and ozone profiles were investigated using satellite measurements. When the intensity of the COL peaked on 10 July 2007, the total column ozone (TCO) increase reached a maximum (40--70 DU). This could be dynamically attributed to both the descent of the tropopause (～75%) and the downward transport of stratospheric ozone across the tropopause (～25%). Analysis of the tropospheric ozone profiles provided evidence for irreversible transport/mixing of ozone-rich stratospheric air across the tropopause near the upper-level front region ahead of the COL center. This ozone intrusion underwent downstream transport by the upper tropospheric winds, leading to further increase in TCO by 12--16 DU over broad regions extending from east China toward the northern Japan Sea via South Korea. Meteorological analysis also showed the precedence of the stratospheric intrusion ahead of the development of cyclones in the middle and lower troposphere.  相似文献   

6.
On summing the components of radiative forcing of climate change   总被引：1，自引：0，他引：1  
 Radiative forcing is a useful concept in determining the potential influence of a particular mechanism of climate change. However, due to the increased number of forcing agents identified over the past decade, the total radiative forcing is difficult to assess. By assigning a range of probability distribution functions to the individual radiative forcings and using a Monte-Carlo approach, we estimate the total radiative forcing since pre-industrial times including all quantitative radiative forcing estimates to date. The resulting total radiative forcing has a 75–97% probability of being positive (or similarly a 3–25% probability of being negative), with mean radiative forcing ranging from +0.68 to +1.34 W m−2, and median radiative forcing ranging from +0.94 to +1.39 W m−2. Received: 14 March 2001 / Accepted: 1 June 2001  相似文献   

7.
NUMERICAL INVESTIGATION OF QBO IN OZONE   总被引：1，自引：0，他引：1  
In this paper, a two-dimensional primitive equation model, coupling dynamical, radiative andphotochemical processes, is used to simulate the quasi-biennial oscillation (QBO) in ozone. TheQBO in total ozone has been successfully simulated when the forcing of equatorial stratosphericQBO in zonal wind is imposed. The simulated characters of QBO in ozone are in close agreementwith those observed. We further analyzed the mechanism of formation and maintenance of QBO inozone. In the different phases of QBO in equatorial stratospheric wind field, the global circulationhas so great difference that it makes the effects of advection transfer and eddy transfer present aquasi-biennial periodical variation. Chemical effect and dynamical effect are basically out-of-phase.They together form and maintain the QBO in ozone. Total variation rate is a tiny difference of thetwo large amounts. At the lower level of middle-high latitudes, however, it has a phase differenceof about 1-2 months between dynamical and negative chemical effects, where the dynamical effectis comparatively greater. QBO in ozone has no clear counter effects on atmospheric circulation. The experiment resultsshow that the effects of QBO in ozone on temperature field and wind field are very small.  相似文献   

8.
We summarize an on-line coupled meteorological–emissions–photochemical modelling system that allows feedback from air-quality/chemistry to meteorology via radiative forcing. We focus on the radiative-forcing impacts (direct effects) of ozone. We present an application of the coupled modelling system to the episode of 23–31 July 1998 in Portland, Oregon, U.S.A. Results suggest that the inclusion of radiative-forcing feedback produces small but accountable impacts. For this region and episode, stand-alone radiative transfer simulations, i.e., evaluating the effects of radiative forcing independently of changes in meteorology or emissions, suggest that a change of 1 ppb in ground-level ozone is approximately equivalent to a change of 0.017 W m−2 in radiative forcing. In on-line, coupled, three-dimensional simulations, where the meteorological dependencies are accounted for, domain-wide peak ozone concentrations were higher by 2–4 ppb (relative to a simulated peak of 119.4 ppb) when including the effects of radiative-forcing feedback. A scenario of 10% reduction in anthropogenic emissions produced slightly larger decreases in ozone, an additional 1 ppb in local-peak reductions, relative to scenarios without feedback.  相似文献   

9.
The Earth System Climate Model from the University of Victoria is used to investigate changes in ocean properties such as heat content, temperature, salinity, density and circulation during 1500 to 2000, the time period which includes the Little Ice Age (LIA) (1500–1850) and the industrial era (1850–2000). We force the model with two different wind-stress fields which take into account the North Atlantic Oscillation. Furthermore, temporally varying radiative forcings due to volcanic activity, insolation changes and greenhouse gas changes are also implemented. We find that changes in the upper ocean (0–300 m) heat content are mainly driven by changes in radiative forcing, except in the polar regions where the varying wind-stress induces changes in ocean heat content. In the full ocean (0–3,000 m) the wind-driven effects tend to reduce, prior to 1700, the downward trend in the ocean heat content caused by the radiative forcing. Afterwards no dynamical effect is visible. The colder ocean temperatures in the top 600 m during the LIA are caused by changes in radiative forcing, while the cooling at the bottom is wind-driven. The changes in salinity are small except in the Arctic Ocean. The reduced salinity content in the subsurface Arctic Ocean during the LIA is a result from reduced wind-driven inflow of saline water from the North Atlantic. At the surface of the Arctic Ocean the changes in salinity are caused by changes in sea–ice thickness. The changes in density are a composite picture of the temperature and salinity changes. Furthermore, changes in the meridional overturning circulation (MOC) are caused mainly by a varying wind-stress forcing; the additional buoyancy driven changes due to the radiative forcings are small. The simulated MOC is reduced during the LIA as compared to the industrial era. On the other hand, the ventilation rate in the Southern Ocean is increased during the LIA.  相似文献   

10.
To analyze the mechanism by which water vapor increase leads to cooling in the stratosphere, the effects of water-vapor increases on temperature in the stratosphere were simulated using the two-dimensional, interactive chemical dynamical radiative model (SOCRATES) of NCAR. The results indicate that increases in stratospheric water vapor lead to stratospheric cooling, with the extent of cooling increasing with height, and that cooling in the middle stratosphere is stronger in Arctic regions. Analysis of the radiation process showed that infrared radiative cooling by water vapor is a pivotal factor in middle-lower stratospheric cooling. However, in the upper stratosphere (above 45 km), infrared radiation is not a factor in cooling; there, cooling is caused by the decreased solar radiative heating rate resulting from ozone decrease due to increased stratospheric water vapor. Dynamical cooling is important in the middle-upper stratosphere, and dynamical feedback to temperature change is more distinct in the Northern Hemisphere middle-high latitudes than in other regions and signiffcantly affects temperature and ozone in winter over Arctic regions. Increasing stratospheric water vapor will strengthen ozone depletion through the chemical process. However, ozone will increase in the middle stratosphere. The change in ozone due to increasing water vapor has an important effect on the stratospheric temperature change.  相似文献   

11.
J. Ray Bates 《Climate Dynamics》2012,38(3-4):455-473
A theoretical investigation of climate stability and sensitivity is carried out using three simple linearized models based on the top-of-the-atmosphere energy budget. The simplest is the zero-dimensional model (ZDM) commonly used as a conceptual basis for climate sensitivity and feedback studies. The others are two-zone models with tropics and extratropics of equal area; in the first of these (Model A), the dynamical heat transport (DHT) between the zones is implicit, in the second (Model B) it is explicitly parameterized. It is found that the stability and sensitivity properties of the ZDM and Model A are very similar, both depending only on the global-mean radiative response coefficient and the global-mean forcing. The corresponding properties of Model B are more complex, depending asymmetrically on the separate tropical and extratropical values of these quantities, as well as on the DHT coefficient. Adopting Model B as a benchmark, conditions are found under which the validity of the ZDM and Model A as climate sensitivity models holds. It is shown that parameter ranges of physical interest exist for which such validity may not hold. The 2?×?CO2 sensitivities of the simple models are studied and compared. Possible implications of the results for sensitivities derived from GCMs and palaeoclimate data are suggested. Sensitivities for more general scenarios that include negative forcing in the tropics (due to aerosols, inadvertent or geoengineered) are also studied. Some unexpected outcomes are found in this case. These include the possibility of a negative global-mean temperature response to a positive global-mean forcing, and vice versa.  相似文献   

12.
The global three-dimensional Lagrangian chemistry-transport model STOCHEM has been used to follow changes in the tropospheric distributions of methane CH4 and ozone O3 following the emission of pulses of the oxides of nitrogen NO x . Month-long emission pulses of NO x produce deficits in CH4 mixing ratios that bring about negative radiative forcing (climate cooling) and decay away with e-folding times of 10–15 years. They also produce short-term excesses in O3 mixing ratios that bring about positive radiative forcing (climate warming) that decay over several months to produce deficits, with their attendant negative radiative forcing (climate cooling) that decays away in step with the CH4 deficits. Total time-integrated net radiative forcing is markedly influenced by cancellation between the negative CH4 and long-term O3 contributions and the positive short-term O3 contribution to leave a small negative residual. Consequently, total net radiative forcing from NO x emission pulses and the global warming potentials derived from them, show a strong dependence on the magnitudes, locations and seasons of the emissions. These dependences are illustrated using the Asian continent as an example and demonstrate that there is no simple robust relationship between continental-scale NO x emissions and globally-integrated radiative forcing. We find that the magnitude of the time-integrated radiative forcing from NO x -driven CH4 depletion tends to approach and outweigh that from ozone enhancement, leaving net time-integrated radiative forcings and global warming potentials negative (climate cooling) in contrast to the situation for aircraft NO x (climate warming). Control of man-made surface NO x emissions alone may lead to positive radiative forcing (climate warming).  相似文献   

13.
平流层对对流层的作用是准确评估、预测对流层气候变化的一个重要方面。其中平流层成分尤其是臭氧的变化,可以改变平流层乃至对流层的辐射平衡,从而影响平流层、对流层的热动力过程。本文从辐射、动力2个角度介绍了平流层臭氧影响对流层气候变化的若干研究进展。平流层臭氧可以通过长短波辐射的方式对对流层大气造成辐射强迫,利用大气化学气候模式可以定量计算平流层臭氧变化引起的辐射强迫,但是辐射强迫的估算受模式中辐射传输模块本身缺陷的影响存在不确定性。动力方面,平流层臭氧变化产生的辐射效应可以改变温度的垂直和经向梯度,造成波折射指数的变化,进而影响平流层甚至对流层内波的折射与反射,通过上对流层下平流层区域内的波—流相互作用,对对流层气候产生影响。另外,南极臭氧损耗可通过大气环状模影响冬春季中高纬度对流层的天气气候,但是其影响的强度大小以及物理机制仍需进一步的确认。值得注意的是,北极平流层臭氧的变化与北半球中高纬度气候变化之间的关系相比南半球要更加复杂,需要更为深入的研究。  相似文献   

14.
An improved stratospheric representation has been included in simulations with the Hadley Centre HadGEM1 coupled ocean atmosphere model with natural and anthropogenic forcings for the period 1979–2003. An improved stratospheric ozone dataset is employed that includes natural variations in ozone as well as the usual anthropogenic trends. In addition, in a second set of simulations the quasi biennial oscillation (QBO) of stratospheric equatorial zonal wind is also imposed using a relaxation towards ERA-40 zonal wind values. The resulting impact on tropospheric variability and trends is described. We show that the modelled cooling rate at the tropopause is enhanced by the improved ozone dataset and this improvement is even more marked when the QBO is also included. The same applies to warming trends in the upper tropical troposphere which are slightly reduced. Our stratospheric improvements produce a significant increase of internal variability but no change in the positive trend of annual mean global mean near-surface temperature. Warming rates are increased significantly over a large portion of the Arctic Ocean. The improved stratospheric representation, especially the QBO relaxation, causes a substantial reduction in near-surface temperature and precipitation response to the El Chichón eruption, especially in the tropical region. The winter increase in the phase of the northern annular mode observed in the aftermath of the two major recent volcanic eruptions is partly captured, especially after the El Chichón eruption. The positive trend in the southern annular mode (SAM) is increased and becomes statistically significant which demonstrates that the observed increase in the SAM is largely subject to internal variability in the stratosphere. The possible inclusion in simulations for future assessments of full ozone chemistry and a gravity wave scheme to internally generate a QBO is discussed.  相似文献   

15.
Summary  A new technical procedure is introduced to determine the stratosphere adjusted radiative forcing at the tropopause in the framework of the 3-D climate model ECHAM4. However, the procedure appears to be appropriate for other GCMs as well. It allows to study in a straightforward way the problem of the general usefulness of radiative forcing as a reliable predictor of climate change. Some examples are given for illustration. It is, once again, confirmed that the climate sensitivity is practically equal for experiments with increased solar insolation and increased CO2 concentration. However, a higher climate sensitivity is obtained for ozone perturbations with a horizontally or vertically inhomogeneous distribution. The latter finding is in qualitative agreement with respective results reported in other studies, whereas the value of the climate sensitivity is exceptionally high in our model. The physical reasons for the unique model behaviour in the ozone experiments are currently not understood. Received August 28, 2000 Revised January 2, 2001  相似文献   

16.
Five simple indices of surface temperature are used to investigate the influence of anthropogenic and natural (solar irradiance and volcanic aerosol) forcing on observed climate change during the twentieth century. These indices are based on spatial fingerprints of climate change and include the global-mean surface temperature, the land-ocean temperature contrast, the magnitude of the annual cycle in surface temperature over land, the Northern Hemisphere meridional temperature gradient and the hemispheric temperature contrast. The indices contain information independent of variations in global-mean temperature for unforced climate variations and hence, considered collectively, they are more useful in an attribution study than global mean surface temperature alone. Observed linear trends over 1950–1999 in all the indices except the hemispheric temperature contrast are significantly larger than simulated changes due to internal variability or natural (solar and volcanic aerosol) forcings and are consistent with simulated changes due to anthropogenic (greenhouse gas and sulfate aerosol) forcing. The combined, relative influence of these different forcings on observed trends during the twentieth century is investigated using linear regression of the observed and simulated responses of the indices. It is found that anthropogenic forcing accounts for almost all of the observed changes in surface temperature during 1946–1995. We found that early twentieth century changes (1896–1945) in global mean temperature can be explained by a combination of anthropogenic and natural forcing, as well as internal climate variability. Estimates of scaling factors that weight the amplitude of model simulated signals to corresponding observed changes using a combined normalized index are similar to those calculated using more complex, optimal fingerprint techniques.  相似文献   

17.
In most climate simulations used by the Intergovernmental Panel on Climate Change 2007 fourth assessment report, stratospheric processes are only poorly represented. For example, climatological or simple specifications of time-varying ozone concentrations are imposed and the quasi-biennial oscillation (QBO) of equatorial stratospheric zonal wind is absent. Here we investigate the impact of an improved stratospheric representation using two sets of perturbed simulations with the Hadley Centre coupled ocean atmosphere model HadGEM1 with natural and anthropogenic forcings for the 1979–2003 period. In the first set of simulations, the usual zonal mean ozone climatology with superimposed trends is replaced with a time series of observed zonal mean ozone distributions that includes interannual variability associated with the solar cycle, QBO and volcanic eruptions. In addition to this, the second set of perturbed simulations includes a scheme in which the stratospheric zonal wind in the tropics is relaxed to appropriate zonal mean values obtained from the ERA-40 re-analysis, thus forcing a QBO. Both of these changes are applied strictly to the stratosphere only. The improved ozone field results in an improved simulation of the stepwise temperature transitions observed in the lower stratosphere in the aftermath of the two major recent volcanic eruptions. The contribution of the solar cycle signal in the ozone field to this improved representation of the stepwise cooling is discussed. The improved ozone field and also the QBO result in an improved simulation of observed trends, both globally and at tropical latitudes. The Eulerian upwelling in the lower stratosphere in the equatorial region is enhanced by the improved ozone field and is affected by the QBO relaxation, yet neither induces a significant change in the upwelling trend.  相似文献   

18.
Increases in chlorinated and brominated halocarbons are believed to be responsible for the depletion of stratospheric ozone observed over much of the globe in the past decade or so. Ozone depletion is in turn believed to lead to a negative radiative forcing, tending to cool the stratosphere and the surface. We show that the increasing atmospheric concentrations of ozone-depleting halocarbons and onset of related ozone depletion likely led to a negative forcing of the climate system in the 1980s that slowed significantly the rate of change of total anthropogenic radiative forcing due to the combined effect of all greenhouse gases over that decade. Within the next decade, emissions of these halocarbons are expected to rapidly decrease, with corresponding impacts on ozone and radiative forcing. As the emissions of ozone-depleting gases are reduced and eventually phased out, the rate of ozone depletion is expected to decrease and eventually reverse. All other things being equal, we show that the change from deepening ozone depletion in the 1980s to ozone increases in the future should lead to a pronounced increase in the decadal rate of change of anthropogenic greenhouse forcing of the next few decades, perhaps to levels unprecedented in this century.  相似文献   

19.
From multi-ensembles of climate simulations using the Community Climate System Model version 3, global climate changes have been investigated focusing on long-term responses to stabilized anthropogenic forcings. In addition to the standard forcing scenarios for the current international assessment, an overshoot scenario, where radiative forcings are decreased from one stabilized level to another, is also considered. The globally-averaged annual surface air temperature increases during the twenty-first century by 2.58 and 1.56°C for increased forcings under two future scenarios denoted by A1B and B1, respectively. These changes continue but at much slower rates in later centuries under forcings stabilized at year 2100. The overshoot scenario provides a different pathway to the lower B1 level by way of the greater A1B level. This scenario results in a surface climate similar to that in the B1 scenario within 100 years after the forcing reaches the B1 level. Contrasting to the surface changes, responses in the ocean are significantly delayed. It is estimated from the linear response theory that temperature changes under stabilized forcings to a final equilibrium state in the A1B (B1) scenario are factors of 0.3–0.4, 0.9, and 17 (0.3, 0.6, and 11) to changes during the twenty-first century, respectively, for three ocean layers of the surface to 100, 100–500, and 500 m to the bottom. Although responses in the lower ocean layers imply a nonlinear behavior, the ocean temperatures in the overshoot and B1 scenarios are likely to converge in their final equilibrium states.  相似文献   

20.
The variability of Antarctic total column ozone in 1980–2018 is considered. The study analyzes trends in Antarctic total column ozone during the study period as well as the physical and chemical processes affecting the seasonal variability of total column ozone. The main attention is paid to the influence of dynamical processes on the stability of the Antarctic polar vortex, to the formation of polar stratospheric clouds, and to the influence of gas-phase and heterogeneous processes on the surface of polar stratospheric clouds and sulfate aerosol. The method of research is the analysis of the results of ground and satellite observations and numerical modeling of physical and chemical processes over the Antarctic using a global chemistry transport model with the dynamical parameters specified from reanalysis data.  相似文献   

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