共查询到20条相似文献，搜索用时 442 毫秒
1.
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
2.
G. Schädler 《Boundary-Layer Meteorology》1990,51(1-2):1-29
A two-dimensional mesoscale soil-atmosphere model is used to simulate the triggering of atmospheric convection by horizontally varying soil water content. The variation is periodic with a wavelength between 4 and 40 km, which is considered a realistic scale for the variation of land surface characteristics. Three stages of convection can be clearly discerned: a short initial stage when convection sets in and where the size of the conective cells is determined by , a mature stage with well developed cells whose size is still determined by , and a decay/transformation stage, characterized by the formation of narrow regions of strong updrafts and wide regions of moderate downdrafts, independent of . Parameters relevant for the transition are given, and the importance of the feedback between soil and atmosphere is demonstrated. The dependence of convective parameters, e.g., height of the convective layer, vertical velocity and fluxes of heat and moisture on is investigated. The calculations of the mature stage are compared with the predictions of a linear model. 相似文献
3.
Uncertainties in the climate response to a doubling of atmospheric CO2 concentrations are quantified in a perturbed land surface parameter experiment. The ensemble of 108 members is constructed by systematically perturbing five poorly constrained land surface parameters of global climate model individually and in all possible combinations. The land surface parameters induce small uncertainties at global scale, substantial uncertainties at regional and seasonal scale and very large uncertainties in the tails of the distribution, the climate extremes. Climate sensitivity varies across the ensemble mainly due to the perturbation of the snow albedo parameterization, which controls the snow albedo feedback strength. The uncertainty range in the global response is small relative to perturbed physics experiments focusing on atmospheric parameters. However, land surface parameters are revealed to control the response not only of the mean but also of the variability of temperature. Major uncertainties are identified in the response of climate extremes to a doubling of CO2. During winter the response both of temperature mean and daily variability relates to fractional snow cover. Cold extremes over high latitudes warm disproportionately in ensemble members with strong snow albedo feedback and large snow cover reduction. Reduced snow cover leads to more winter warming and stronger variability decrease. As a result uncertainties in mean and variability response line up, with some members showing weak and others very strong warming of the cold tail of the distribution, depending on the snow albedo parametrization. The uncertainty across the ensemble regionally exceeds the CMIP3 multi-model range. Regarding summer hot extremes, the uncertainties are larger than for mean summer warming but smaller than in multi-model experiments. The summer precipitation response to a doubling of CO2 is not robust over many regions. Land surface parameter perturbations and natural variability alter the sign of the response even over subtropical regions. 相似文献
4.
Tropospheric photodissociation rate coefficients (J values) were calculated for NO2, O3, HNO2, CH2O, and CH3CHO using high spectral resolution (0.1 mm wavelength increments), and compared to the J values obtained with numerically degraded resolution (=1, 2, 4, 6, 8, and 10 nm, and several commonly used nonuniform grids). Depending on the molecule, substantial errors can be introduced by the larger increments. Thus for =10 nm, errors are less than 1% for NO2, less than 2% for HNO2, +6.5% to -16% for CH2O, -6.9% to +24% for CH3CHO, and -24% to +110% for O3. The errors for CH2O arise from the fine structure of its absorption spectrum, and are prevalently negative (underestimate of J). The errors for O3, and to a lesser extent for CH3CHO, arise mainly from under-resolving the overlap of the molecular action spectrum and the tropospheric actinic flux in the wavelength region of stratospheric ozone attenuation. The sign of those errors depends on whether the actinic flux is averaged onto the grid before or after the radiative transfer calculation. In all cases studied, grids with 2 nm produced errors no larger than 5%. 相似文献
5.
The potential of aircraft-induced ozone changes to force a substantial climate impact is investigated by means of simulations
with an atmospheric general circulation model, coupled to a mixed layer ocean model. We present results from several numerical
experiments that are based on ozone change patterns for 1992 aviation and on a future scenario for the year 2015. In both
cases, the climate signal is statistically significant. The strength of the ozone impact is of comparable magnitude to that
arising from aircraft CO2 emissions, thus meaning a non-negligible contribution to the total climate effect of aviation emissions. There are indications
of a characteristic signature of the aircraft ozone related temperature response pattern, distinctly different from that associated
with the increase of well-mixed greenhouse gases. Likewise, the climate sensitivity to non-uniform ozone changes including
a strong concentration perturbation at the tropopause may be higher than the climate sensitivity to uniform changes of a greenhouse
gas. In a hierarchy of experiments, for which the spatial structure of an aircraft-related ozone perturbation was left fixed,
while the amplitude of the perturbation was artificially increased, the climate signal depends in a non-linear way on the
radiative forcing.
Received: 10 September 1998 / Accepted: 4 May 1999 相似文献
6.
Sensitivity Analysis of Emissions Corridors for the 21st Century 总被引：1，自引：1，他引：0
We investigate the sensitivity of emissions corridors for the 21st century to various factors that are currently under debate in the climate change arena. Emissions corridors represent the range of admissible emissions futures that observe some predefined guardrails on the future development of the human-climate system. They are calculated on the conceptual and methodological basis of the tolerable windows approach. We assess the sensitivity of the corridors to the choice of time-resolved as well as intertemporally aggregated guardrails that exclude an intolerable amount of climate change on the one hand and unbearable mitigation burdens on the other. In addition, we investigate the influence of climate sensitivity on the corridors.Results show a large dependence of emissions corridors on the choice of guardrails and the value of climate sensitivity T
2CO
2. If the guardrail on climate change is specified in terms of a maximum admissible global mean temperature increase T
max to be observed at any time, the size of the corridors is predominantly determined by a climate impact resilience parameter =T
max/T
2CO
2. As is varied from values below 0.5 to values above 1.5, we move from cases where no emissions profile whatsoever can observe all guardrails, to cases where no significant emissions reduction seems necessary given the range of emissions scenarios for the 21st century. The limits on admissible mitigation efforts influence predominantly the timing and the economic viability of emissions reductions. A large mitigation flexibility allows for wait then run emissions paths, while low flexibility asks for a significantly more prudent approach. 相似文献
7.
《大气与海洋》2013,51(3):224-237
Abstract The University of Victoria's (UVic) Earth System Climate model is used to conduct equilibrium atmospheric CO2 sensitivity experiments over the range 200–1600 ppm in order to explore changes in northern hemisphere snow cover and feedbacks on terrestrial surface air temperature (SAT). Simulations of warmer climates predict a retreat of snow cover over northern continents, in a northeasterly direction. The decline in northern hemisphere global snow mass is estimated to reach 33% at 600 ppm and 54% at 1200 ppm. In the most northerly regions, annual mean snow depth increases for simulations with CO2 levels higher than present day. The shift in the latitude of maximum snowfall is estimated to be inversely proportional to the CO2 concentration. The northern hemisphere net shortwave radiation changes are found to be greater over land than over the ocean, suggesting a stronger albedo feedback from changes in terrestrial snow cover than from changes in sea ice. Results also reveal high sensitivity of the snow mass balance under low CO2 conditions. The amplification feedback (defined as the zonal SAT anomaly caused by doubling CO2 divided by the equatorial anomaly) is greatest for scenarios with less than 300 ppm, reaching 1.9 at the pole for 250 ppm. The stronger feedback is attributed to the significant albedo changes over land areas. The simulation with 200 ppm triggers continuous accumulation of snow ('glaciation') in regions which, according to paleo‐reconstructions, were covered by ice during the last glacial cycle (the Canadian Arctic, Scandinavia, and the Taymir Peninsula). 相似文献
8.
STAR (System for Transfer of Atmospheric Radiation) was developed to calculate accurately and efficiently the irradiance, the actinic flux, and the radiance in the troposphere. Additionally a very efficient calculation scheme to computer photolysis frequencies for 21 different gases was evolved. STAR includes representative data bases for atmospheric constituents, especially aerosol particles. With this model package a sensitivity study of the influence of different parameter on photolysis frequencies in particular of O3 to Singlet D oxygen atoms, of NO2, and of HCHO was performed. The results show the quantitative effects of the influence of the solar zenith angle, the ozone concentration and vertical profile, the aerosol particles, the surface albedo, the temperature, the pressure, the concentration of NO2, and different types of clouds on the photolysis frequencies.Notation
I
A(, )
actinic flux
-
I
H(, )
irradiance
-
L(, , , )
radiance
-
wavelength
-
azimuth angle
-
cosine of zenith angle
-
s
cosine of solar zenith angle
-
optical depth
-
s
scattering coefficient
-
c
extinction coefficient
-
o
single scattering albedo
-
p
mix
mixed phase function
-
g
mix
mixed asymmetry factor
-
J
gas
photolysis frequency 相似文献
9.
Concurrent measurements of the surface energy balance components (net radiation, heat storage, and sensible and latent heat fluxes) were made in three communities (open water, Phragmites australis, Scirpus acutus) in a wetland in north-central Nebraska, U.S.A., during May-October, 1994. The Bowen ratio – energy balance method was used to calculate latent and sensible heat fluxes. This paper presents results from the open water area. The heat stored in water (G) was found to play a major role in the energy exchange over the water surface. During daytime, G consumed 45–60% of R
n
, the net radiation (seasonally averaged daytime G was about 127 W m–2). At night, G was a significant source of energy (seasonally averaged nighttime G was about -135 Wm–). The diurnal pattern of latent heat flux ( E) did not follow that of R
n
. On some days, E was near zero during midday periods with large R
n
. The diurnal variability in E seemed to be significantly affected by temperature inversions formed over the cool water surface. The daily evaporation rate (E) ranged from 2 to 8 mm during the measurement period, and was generally between 70 and 135% of the equilibrium rate. 相似文献
10.
Simon F. B. Tett Richard Betts Thomas J. Crowley Jonathan Gregory Timothy C. Johns Andy Jones Timothy J. Osborn Elisabeth Öström David L. Roberts Margaret J. Woodage 《Climate Dynamics》2007,28(1):3-34
A climate simulation of an ocean/atmosphere general circulation model driven with natural forcings alone (constant “pre-industrial” land-cover and well-mixed greenhouse gases, changing orbital, solar and volcanic forcing) has been carried out from 1492 to 2000. Another simulation driven with natural and anthropogenic forcings (changes in greenhouse gases, ozone, the direct and first indirect effect of anthropogenic sulphate aerosol and land-cover) from 1750 to 2000 has also been carried out. These simulations suggest that since 1550, in the absence of anthropogenic forcings, climate would have warmed by about 0.1 K. Simulated response is not in equilibrium with the external forcings suggesting that both climate sensitivity and the rate at which the ocean takes up heat determine the magnitude of the response to forcings since 1550. In the simulation with natural forcings climate sensitivity is similar to other simulations of HadCM3 driven with CO2 alone. Climate sensitivity increases when anthropogenic forcings are included. The natural forcing used in our experiment increases decadal–centennial time-scale and large spatial scale climate variability, relative to internal variability, as diagnosed from a control simulation. Mean conditions in the natural simulation are cooler than in our control simulation reflecting the reduction in forcing. However, over certain regions there is significant warming, relative to control, due to an increase in forest cover. Comparing the simulation driven by anthropogenic and natural forcings with the natural-only simulation suggests that anthropogenic forcings have had a significant impact on, particularly tropical, climate since the early nineteenth century. Thus the entire instrumental temperature record may be “contaminated” by anthropogenic influences. Both the hydrological cycle and cryosphere are also affected by anthropogenic forcings. Changes in tree-cover appear to be responsible for some of the local and hydrological changes as well as an increase in northern hemisphere spring snow cover.
相似文献
| Simon F. B. TettEmail: |
11.
L. Schulze 《Theoretical and Applied Climatology》1956,7(2):223-239
Zusammenfassung Nach einem Überblick über Möglichkeiten und Schwierigkeiten der Strahlungsmessung in der Lichttechnik wird auf die physikalisch teilweise gleichen, teilweise andersartigen Verhältnisse bei der Pflanze hingewiesen. Die Fehlerquellen bei den bisher in der Ökologie verwendeten Verfahren werden aufgesucht und ihre Gründe dargestellt.Es wird vorgeschlagen, an Stelle der AugenempfindlichkeitskurveV
bei einem analogen Meßverfahren dieWirkungskurve der CO
2
-Assimilation W
zu verwenden. Dabei sollen Assimilationslichteinheiten eingeführt werden, die den Maßeinheiten der Lichttechnik entsprechen, wofür eine Anschlußmöglichkeit aufgezeigt wird. Da die Assimilation nur einen Teil der Wachstumsvorgänge darstellt, ist eine Farbkennzeichnung der Lichtquellen erforderlich und soll entsprechend derYoung-Helmholtzschen Dreifarbentheorie des Sehens mit anderen Farbreizkurven durchgeführt werden. Ein theoretisches Verfahren zur Ermittlung der Assimilationslichtgrößen und Farbkoordinaten wird dargestellt und die Anwendung durch Beispiele einiger Lampentypen gezeigt. Einige pflanzenphysiologische Versuchsreihen, die zur Prüfung und zur Verbesserung nötig sind, werden vorgeschlagen.
Mit 4 Textabbildungen 相似文献
Summary After a general review on the possibilities and the difficulties of measuring radiation in the illumination technique, the author refers to physical conditions among plants which are partly different and partly similar. He discusses the sources of errors of the hitherto prevailing methods in ecology and their causes.He proposes to use the curve of assimilation effectivity of CO2 (W ) instead of that of eye sensibility (V ). For this purpose it is necessary to introduce assimilation light units which correspond to the measuring units of illumination technique. As assimilation represents only a part of the processes of growing, a characterization of the colours of the light sources is necessary and has to be performed in accordance with theYoung-Helmholtz three colour theory of vision but with other colour sensibility curves. The author describes a theoretical method for the determination of assimilation light values and of colour coordinates as well as its application to several types of lamps. Furthermore he proposes some series of botanical experiments in order to test and perfect the method.
Résumé Après avoir donné un aperçu des possibilités et des difficultés de la mesure du rayonnement dans la technique de l'éclairage, l'auteur insiste sur les conditions physiques parfois semblables et parfois différentes qui règnent chez les plantes. Il recherche les sources d'erreurs des méthodes employées jusqu'ici en écologie et décrit leurs causes.L'auteur propose d'utiliser la courbe d'effectivité et de l'assimilation du CO2 (W ) au lieu de celle de la sensibilité de l'oeil (V ). Il faut alors introduire des unités de lumière d'assimilation qui correspondent aux unités de mesure dans la technique de l'éclairage. Etant donné que l'assimilation ne représente qu'une partie des éléments de croissance, il y a lieu de déterminer les couleurs des sources de lumière; ceci doit être fait selon la théorie des trois couleurs de la vision deYoung-Helmholtz mais avec d'autres courbes de sensibilité de couleur. L'auteur décrit une méthode théorique de détermination des grandeurs de lumière d'assimilation et des coordonnées de couleurs ainsi que son application à l'aide de quelques types de lampes. Il propose encore quelques séries d'expériences botaniques qui seraient propres à examiner et à améliorer la méthode.
Mit 4 Textabbildungen 相似文献
12.
Antonie Verkholantzeff-Wegener 《Theoretical and Applied Climatology》1955,7(1):96-116
Zusammenfassung Bisher wurde der Umkehreffekt vonGötz nur mittels Photozelle oder Zählrohr untersucht. Die Anwendung des Multipliers als Meßinstrument bietet wegen dessen wesentlich größerer Empfindlichkeit viele Vorteile. So kann damit noch bei Zenitdistanzen der Sonnez>90° bei kleineren Wellenlängen als bisher und bei engerem Spalt des Spektrometers (bessere Monochromasie) gemessen werden.Resultate: 1. Die Verschiebung der Minima der Umkehrkurven,i
n
/i
m
=f(z), erfolgtgleichsinnig mit abnehmender Wellenlänge
n
nach kleineren Zenitdistanzen (entgegen den Angaben vonSchein undStoll, aber in Übereinstimmung mit der Theorie nachGötz undDobson). 2. Zum ersten Mal beziehen sich hier die Angaben aufeffektive Wellenlängen, die ihrerseits noch eine Funktion vonz sind. 3. Aus den Messungen bei den kleinsten, bisher noch nicht zugänglichen Wellenlängen folgt, daß deren Streuniveaus bei tiefen Sonnenständen oberhalb der Schichten größten Ozongehaltes liegen müssen.
Mit 9 Textabbildungen 相似文献
Summary Until now the Umkehr-effect of Götz (inversion of intensity-ratio in zenith-scattered sunlight) has been investigated only by means of photocells or Geiger counters. The application of the multiplier as measuring instrument is of greater advantage because of its much higher sensitivity. Measurements can be made with it even with the sun's zenith distancesz>90° at shorter wave-lengths and with a narrower slit of the spectrometer (better monochromasy).Results: (1) The shift of the minima of the Umkehr-curvesi n /i m =f(z), erfolgtgleichsinnig mit abnehmender Wellenlänge n shows the same sense with decreasing wave-length n to shorter zenith distances (in opposition to the assertions ofSchein andStoll, but in agreement with the theory ofGötz andDobson). (2) For the first time the statements refer here to effective wave-lengths which in their turn are a function ofz. (3) From measurements of the shortest wave-lengths which until now have not yet been accessible, it can be concluded that at low sun heights the scattering level is situated above the layers with the greatest ozone content.
Résumé Jusqu'à présent le «Umkehreffect» deGötz, c. à d. l'effet d'inversion des relations d'intensité dans le rayonnement solaire zénithal diffus, n'a été étudié qu'au moyen de cellules photo-électriques ou de compteurs Geiger. En utilisant le multiplicateur comme instrument de mesure on obtient l'avantage d'une bien plus grande sensibilité. Ainsi il est possible de mesurer encore à des distances zénithales du soleil dez>90° par longueurs d'ondes plus courtes que jusqu'ici et avec une fente du spectromètre plus étroite, ce qui nous garantit une meilleure monochromasie.Résultats: 1) Le déplacement des minima des courbes d'inversioni n /i m =f(z), erfolgtgleichsinnig mit abnehmender Wellenlänge n s'effectue dans le même sens que la diminution des longuers d'ondes n , par distances zénithales plus petites (contrairement aux assertions deSchein et deStoll, mais en concordance avec la théorie selonGötz etDobson). — 2) Pour la première fois les données se rapportent ici à des longueurs d'ondes effectives qui, de leur côté, sont encore fonctions dez. — 3) Il ressort des mesures des plus courtes longueurs d'ondes, qui, jusqu'ici, restaient hors d'atteinte, que pour des hauteurs du soleil basses, leur niveau de fiffusion se trouve au-dessus des couches ayant le plus grand contenu d'ozone.
Mit 9 Textabbildungen 相似文献
13.
Robert G. Watts 《Climatic change》1980,2(4):387-408
This article is a review of the modeling of potential CO2 effects on climate, intended for an interdisciplinary audience of mathematically oriented scientists and engineers. The carbon dioxide (CO2) content of the atmosphere has shown a systematic increase each year since regular measurements began in 1958. A major source of CO2 is the combustion of fossil fuels. A number of studies of the sensitivity of climate to increases in the CO2 content of the atmosphere have been published. This report is an assimilation of the results of some of these studies. The climate sensitivity problem is introduced through a discussion of the various atmospheric feedbacks and the ice albedo feedback. The most recent estimates of the various feedbacks are used to estimate upper and lower bounds of the globally averaged temperature increase that would accompany a doubling of atmospheric CO2 content. The results of a CO2 doubling experiment using a simple general circulation model are reviewed, and the possible response of the cryosphere is discussed. 相似文献
14.
A photochemical scheme which includes a detailed treatment of multiple scattering up to solar zenith angles of 96° (developed for use in a GCM) has been used to study partitioning within chemical families. Attention is drawn to the different zenith angle dependence of diffuse radiation for the two spectral regions <310 nm and >310 nm. The effect that this has on the so-called 40 km ozone problem is discussed. The importance of correctly including multiple scattering for polar ozone studies is emphasised. 相似文献
15.
The sensitivity of climate to orbitally-related changes in solar radiation at 9000 yr BP (before present) is examined using fixed and interactive soil moisture versions of a low resolution general circulation model. In both versions of the model increased solar radiation for June–August at 9000 yr BP (compared to present) produced enhanced northern monsoons and warmer continental interiors in comparison to present whereas decreased solar radiation at 9000 yr BP in December–February produced weaker southern monsoons. The increased rainfall in the northern tropics in summer increased soil moisture and runoff at 9000 yr BP in the interactive model; in the southern hemisphere decreased rainfall in summer led to decreased soil moisture and runoff. Conditions in summer became drier (decreased soil moisture and runoff) at 9000 yr BP in the northern extratropics.The experiments showed that the magnitude (but not the sign) of model sensitivity to 9000 yr BP radiation is altered by the effects of interactive soil moisture. Decreased soil moisture (about 20%) over northern Eurasia in the interactive model led to smaller evaporative increases, greater temperature increases and greater reduction of precipitation than for the model with fixed soil moisture. Over northern tropical lands, slightly smaller temperature increases and greater evaporation and precipitation increases in the interactive model are linked to the simulation of increased soil moisture at 9000 yr BP. The differences in sensitivity between the two versions of the model over northern Eurasia are statistically significant at the 95% level whereas those for the tropics are not.Overall, the results of the simulations are generally supported by the geologic evidence for 9000 yr BP; however, the evidence lacks sufficient precision and the model resolution is too coarse for detailed model/data comparisons and for assessment of the relative accuracy of the two 9000 yr BP experiments.The computed sensitivities of temperature and soil moisture to 9000 yr BP radiation differ from those simulated under equilibrium conditions in the various general circulation model experiments for increased atmospheric concentration of CO2. In contrast to the effects of the enhanced seasonal cycle of solar radiation at 9000 yr BP, a CO2 increase causes a broad warming of both the ocean and land with little modification of land/ocean temperature difference. The experiments for 9000 yr BP indicate a clearer signal for summer drying than is obtained in the experiments for increased CO2. The results suggest that the 9000 yr BP climate may be of limited utility as an analog to future warm climates. 相似文献
16.
The radiative flux perturbations and subsequent temperature responses in relation to the eruption of Mount Pinatubo in 1991
are studied in the ten general circulation models incorporated in the Coupled Model Intercomparison Project, phase 3 (CMIP3),
that include a parameterization of volcanic aerosol. Models and observations show decreases in global mean temperature of
up to 0.5 K, in response to radiative perturbations of up to 10 W m−2, averaged over the tropics. The time scale representing the delay between radiative perturbation and temperature response
is determined by the slow ocean response, and is estimated to be centered around 4 months in the models. Although the magniude
of the temperature response to a volcanic eruption has previously been used as an indicator of equilibrium climate sensitivity
in models, we find these two quantities to be only weakly correlated. This may partly be due to the fact that the size of
the volcano-induced radiative perturbation varies among the models. It is found that the magnitude of the modelled radiative
perturbation increases with decreasing climate sensitivity, with the exception of one outlying model. Therefore, we scale
the temperature perturbation by the radiative perturbation in each model, and use the ratio between the integrated temperature
perturbation and the integrated radiative perturbation as a measure of sensitivity to volcanic forcing. This ratio is found
to be well correlated with the model climate sensitivity, more sensitive models having a larger ratio. Further, if this correspondence
between “volcanic sensitivity” and sensitivity to CO2 forcing is a feature not only among the models, but also of the real climate system, the alleged linear relation can be used
to estimate the real climate sensitivity. The observational value of the ratio signifying volcanic sensitivity is hereby estimated
to correspond to an equilibrium climate sensitivity, i.e. equilibrium temperature increase due to a doubling of the CO2 concentration, between 1.7 and 4.1 K. Several sources of uncertainty reside in the method applied, and it is pointed out
that additional model output, related to ocean heat storage and radiative forcing, could refine the analysis, as could reduced
uncertainty in the observational record, of temperature as well as forcing. 相似文献
17.
A one-dimensional coupled climate and chemistry model has been developed to estimate past and possible future changes in atmospheric temperatures and chemical composition due to human activities. The model takes into account heat flux into the oceans and uses a new tropospheric temperature lapse rate formulation. As found in other studies, we estimate that the combined greenhouse effect of CH4, O3, CF2Cl2, CFCl3 and N2O in the future will be about as large as that of CO2. Our model calculates an increase in average global surface temperatures by about 0.6°C since the start of the industrial era and predicts for A.D. 2050 a twice as large additional rise. Substantial depletions of ozone in the upper stratosphere by between 25% and 55% are calculated, depending on scenario. Accompanying temperature changes are between 15°C and 25°C. Bromine compounds are found to be important, if no rigid international regulations on CFC emissions are effective. Our model may, however, concivably underestimate possible effects of CFCl3, CF2Cl2, C2F3Cl3 and other CFC and organic bromine emissions on lower stratospheric ozone, because it can not simulate the rapid breakdown of ozone which is now being observed worldwide. An uncertainty study regarding the photochemistry of stratospheric ozone, especially in the region below about 25 km, is included. We propose a reaction, involving excited molecular oxygen formation from ozone photolysis, as a possible solution to the problem of ozone concentrations calculated to be too low above 45 km. We also estimate that tropospheric ozone concentrations have grown strongly in the northern hemisphere since pre-industrial times and that further large increases may take place, especially if global emissions of NOx from fossil fuel and biomass burning were to continue to increase. Growing NOx emissions from aircraft may play an important role in ozone concentrations in the upper troposphere and low stratosphere. 相似文献
18.
R. A. Colman 《Climate Dynamics》2001,17(5-6):391-405
This study addresses the question: what vertical regions contribute the most to water vapor, surface temperature, lapse rate and cloud fraction feedback strengths in a general circulation model? Multi-level offline radiation perturbation calculations are used to diagnose the feedback contribution from each model level. As a first step, to locate regions of maximum radiative sensitivity to climate changes, the top of atmosphere radiative impact for each feedback is explored for each process by means of idealized parameter perturbations on top of a control (1?×?CO2) model climate. As a second step, the actual feedbacks themselves are calculated using the changes modelled from a 2?×?CO2 experiment. The impact of clouds on water vapor and lapse rate feedbacks is also isolated using `clear sky' calculations. Considering the idealized changes, it is found that the radiative sensitivity to water vapor changes is a maximum in the tropical lower troposphere. The sensitivity to temperature changes has both upper and lower tropospheric maxima. The sensitivity to idealized cloud changes is positive (warming) for upper level cloud increases but negative (cooling) for lower level increases, due to competing long and shortwave effects. Considering the actual feedbacks, it is found that water vapor feedback is a maximum in the tropical upper troposphere, due to the large relative increases in specific humidity which occur there. The actual lapse rate feedback changes sign with latitude and is a maximum (negative) again in the tropical upper troposphere. Cloud feedbacks reflect the general decrease in low- to mid-level low-latitude cloud, with an increase in the very highest cloud. This produces a net positive (negative) shortwave (longwave) cloud feedback. The role of clouds in the strength of the water vapor and lapse rate feedbacks is also discussed. 相似文献
19.
The water balance model KAUSHA (Halldin, 1989) was applied to a 100-year-old beech (Fagus sylvatica L.) forest in northern Germany. Overall, a satisfying agreement between modelled evapotranspiration values and independent micrometeorological measurements (Bowen ratio energy balance method) could be observed, although for rainy days KAUSHA showed a tendency to overestimate evapotranspiration. The model was used to predict the effects of a climate warming on the water budgets of the forest. It is shown that a temperature increase of 2°C due to a rising CO2 content of the atmosphere will not change the yearly totals of evapotranspiration significantly, but could have serious effects on the soil water balance during the vegetation period. Because under climate change conditions a higher amount of the available soil water has already been evaporated in winter and spring, soil water content will limit the transpiration of the trees from July to September much more strongly. Therefore, the yield of beech forest might also suffer from drought effects. It can be concluded that a better knowledge of the seasonal distribution of rainfall under climate change conditions is indispensable for predicting effects of rising temperatures and CO2 concentrations on ecosystems. 相似文献
20.
Sigmund Fritz 《Meteorology and Atmospheric Physics》1951,4(1):343-350
Summary In order to investigate the effect of increased solar ultraviolet radiation on total atmospheric ozone, ozone observations have been made during sudden ionospheric disturbances (S. I. D.). If one can assume that the ratio of the extraterrestrial intensity of sunlight at 3110 Å to that at 3300 Å (the wavelengths observed by the measuring instrument) remains unchanged during days with S. I. D., it is found that ozone changes associated with S. I. D. s are small or absent, in agreement with qualitative theoretical expectation.
With 4 Figures. 相似文献
Zusammenfassung Um die Auswirkung einer Zunahme der ultravioletten Sonnenstrahlung auf das atmosphärische Ozon zu untersuchen, wurden beim Auftreten desMögel-Dellinger-Effekts (Sudden Ionospheric Disturbances, S. I. D.) Ozonmessungen angestellt. Unter der Annahme, daß an den Tagen mit S. I. D. das Verhältnis der Intensität der extraterrestrischen Sonnenstrahlung bei 3110 Å zu der bei 3300 Å konstant bleibt, findet man, daß die gleichzeitigen Ozonänderungen entweder sehr klein sind oder ganz fehlen, was in Übereinstimmung mit dem theoretisch zu erwartenden Verhalten ist.
Résumé Pour examiner l'effet de croissance de la radiation solaire ultraviolette sur l'ozone total atmosphérique, des mesures de l'ozone ont été faites pendant certains jours avec des perturbations ionosphériques brusques (Sudden Ionospheric Disturbances, S. I. D.) qui apparaissent ordinairement simultanément avec une éruption solaire. Si l'on suppose que le quotient de l'intensité extra-terrestre du rayonnement solaire pour -3110 Å à celle pour =3300 Å est constant, on constate que les variations de l'ozone coïncidentes avec les S. I. D. sont petites ou manquent complètement ce qui est en bon accord qualitatif avec la théorie.
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