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1.
S. Manabe R. T. Wetherald P. C. D. Milly T. L. Delworth R. J. Stouffer 《Climatic change》2004,64(1-2):59-76
It has been suggested that, unless a major effort is made, the atmospheric concentration of carbon dioxide may rise above four times the pre-industrial level in a few centuries. Here we use a coupled atmosphere-ocean-land model to explore the response of the global water cycle to such a large increase in carbon dioxide, focusing on river discharge and soil moisture. Our results suggest that water is going to be more plentiful in those regions of the world that are already `water-rich'. However, water stresses will increase significantly in regions and seasons that are already relatively dry. This could pose a very challenging problem for water-resource management around the world. For soil moisture, our results indicate reductions during much of the year in many semi-arid regions of the world, such as the southwestern region of North America, the northeastern region of China, the Mediterranean coast of Europe, and the grasslands of Australia and Africa. In some of these regions, soil moisture values are reduced by almost a factor of two during the dry season. The drying in semi-arid regions is likely to induce the outward expansion of deserts to the surrounding regions. Over extensive regions of both the Eurasian and North American continents in high and middle latitudes, soil moisture decreases in summer but increases in winter, in contrast to the situation in semi-arid regions. For river discharge, our results indicate an average increase of ～ 15% during the next few centuries. The discharges from Arctic rivers such as the Mackenzie and Ob' increase by much larger fractions. In the tropics, the discharges from the Amazonas and Ganga-Brahmaputra also increase considerably. However, the percentage changes in runoff from other tropical and many mid-latitude rivers are smaller. 相似文献
2.
DJ Karoly JA Cohen GA Meehl JFB Mitchell AH Oort RJ Stouffer RT Wetherald 《Climate Dynamics》1994,10(1-2):97-105
As an example of the technique of fingerprint detection of greenhouse climate change, a multivariate signal or fingerprint of the enhanced greenhouse effect is defined using the zonal mean atmospheric temperature change as a function of height and latitude between equilibrium climate model simulations with control and doubled CO2 concentrations. This signal is compared with observed atmospheric temperature variations over the period 1963 to 1988 from radiosonde-based global analyses. There is a significant increase of this greenhouse signal in the observational data over this period.These results must be treated with caution. Upper air data are available for a short period only, possibly too short to be able to resolve any real greenhouse climate change. The greenhouse fingerprint used in this study may not be unique to the enhanced greenhouse effect and may be due to other forcing mechanisms. However, it is shown that the patterns of atmospheric temperature change associated with uniform global increases of sea surface temperature, with El NinoSouthern Oscillation events and with decreases of stratospheric ozone concentrations individually are different from the greenhouse fingerprint used here. 相似文献
3.
Richard T. Wetherald 《Climatic change》2010,102(3-4):651-670
This paper examines the subject of hydrologic variability and its changes in two separate integrations of a coupled ocean-atmosphere general circulation model developed at the Geophysical Fluid Dynamics Laboratory/NOAA assuming a 1% per year increase to a doubling and quadrupling of CO2, respectively. Changes in time mean state and variability of precipitation, runoff and soil moisture are evaluated using monthly and seasonal mean data derived from these integrations. Various statistical tests are then performed on the resulting time mean and variability changes. The patterns of hydrologic change for these three quantities are similar to those obtained from previous studies. In northern middle to higher latitudes for the time means, the changes include increases in monthly mean precipitation, increases in monthly mean runoff during the fall, winter and spring seasons and decreases of monthly mean soil moisture during summer. Many of these changes are found to be statistically significant at the 5% significance level for both the time mean and variability especially for the results where CO2 is quadrupled such as monthly mean precipitation. Significant changes also include increases of runoff variability during spring, winter and spring and increases of soil moisture variability during the summer season. These results support statements made in previous IPCC reports that increasing greenhouse gases can lead to more severe and frequent floods and droughts depending upon season and latitude. This study also indicates that the approaches to equilibrium of these two integrations, and the resulting hydrologic changes, take place over time scales of hundreds of years in agreement with several previous investigations. 相似文献
4.
西秦岭凤太矿集区丝毛岭金矿床地质地球化学特征 总被引：1，自引：0，他引：1
西秦岭凤太矿集区丝毛岭金矿床位于八卦庙造山型金矿床西侧5km左右,是一个新探明的剪切带型金矿。其成矿作用过程可分为早期石英-绢云母-硫化物阶段、中期多金属-硫化物阶段和晚期碳酸盐阶段。对早、中期的石英流体包裹体测试结果表明,丝毛岭金矿床成矿流体以富CO2、中温、低盐度为特征,总体上属于中温低盐度CO2-H2O体系,流体包裹体类型的多样性是流体不混溶性的产物。从早阶段到主成矿阶段成矿流体的温度、压力和盐度均有降低,硫逸度增高,有利于金的沉淀富集。H、O、S、C同位素研究结果,以及与八卦庙金矿床的对比分析表明,二者的成矿流体具有相似性和同源性,都是以深部来源为主的多源流体。由于丝毛岭金矿床产出的层位高于八卦庙金矿床,其成矿环境相对开放。 相似文献
5.
Richard T. Wetherald 《Climatic change》2011,109(3-4):569-582
The effects that low clouds in sub-tropical to tropical latitudes have in determining a given model’s climate sensitivity is investigated by analyzing the cloud data produced by 16 “slab” or mixed-layer models submitted to the PCMDI and CFMIP archives and their respective response to a doubling of CO2. It is found that, within the context of the 16 models analyzed, changes of these low clouds appear to play a major role in determining model sensitivity but with changes of middle cloud also contributing especially from middle to higher latitudes. It is noted that the models with the smallest overall cloud change produce the smallest climate sensitivities and vice versa although the overall signs of the respective cloud feedbacks are positive. It is also found that the amounts of low cloud as simulated by the respective control runs have very little correlation with their respective climate sensitivities. In general, the overall latitude-height patterns of cloud change as derived from these more recent experiments agree quite well with those obtained from much earlier studies which include increases of the highest cloud, decreases of cloud lower down in the middle and lower tropospheric and small increases of low clouds. Finally, other mitigating factors are mentioned which could also affect the spread of the resulting climate sensitivities. 相似文献
6.
East Asian winter monsoon: results from eight AMIP models 总被引：6，自引：0，他引：6
Y. Zhang K. R. Sperber J. S. Boyle M. Dix L. Ferranti A. Kitoh K. M. Lau K. Miyakoda D. Randall L. Takacs R. Wetherald 《Climate Dynamics》1997,13(11):797-820
This study evaluates simulations of the East Asian winter monsoon in eight GCMs that participated in the Atmospheric Model
Intercomparison Project (AMIP). In addition to validating the mean state of the winter monsoon, the cold surge and its transient
properties, which includes the frequency, intensity, preferred propagation tracks, and the evolution patterns of the surges,
are examined. GCM simulated temporal distribution of the Siberian high and cold surges is also discussed. Finally, the forcing
of the cold surges on the tropical surface wind and convection, along with their interannual variation is analyzed. The mean
state of the winter monsoon is generally portrayed well in most of the models. These include the climatological position of
the Siberian high, the 200 hPa divergent center, and the large-scale wind patterns at the surface and the 200 hPa. Models
display a wide range of skill in simulating the cold surge and its transient properties. In some of the models, the simulated
cold surge trajectory, intensity, frequency, propagation patterns and source regions are in general agreement with those from
the observed. While in others, the models cannot adequately capture these observed characteristics. The temporal distribution
of the Siberian high and cold surges were realistically reproduced in most GCMs. Most models were able to simulate the effect
of the cold surges on the tropical surface wind, although a few models unrealistically generated subtropical southerly wind
in the mid-winter. The relationship between cold surges and the tropical convection was not satisfactorily simulated in most
models. The common discrepancies in the winter monsoon simulation can be attributed to many factors. In some models, the reason
is directly related to the improper location of the large-scale convective center near the western Pacific. The satisfactory
simulations of the monsoon circulation and the cold surges are partly due to the topographical characteristics of the East
Asian continent, i.e., the Tibetan Plateau to the west and the oceans to the east. The correct simulation of the interannual
variation of the surface wind near the South China Sea (SCS) and the maritime continent is a demanding task for most of the
models. This will require adequate simulations of many aspects, including tropical convection, the Siberian cold dome, the
extratropical-tropical linkage, and the air-sea interaction. The discrepancies noted here furnish a guide for the continuing
improvement of the winter monsoon simulations. Improved simulations will lead to an adequate delineation of the surface wind
and convection near the maritime continent, which is essential for portraying the winter monsoon forcing in a coupled model.
Received: 10 March 1997/Accepted: 4 June 1997 相似文献
7.
Review of simulations of climate variability and change with the GFDL R30 coupled climate model 总被引：5，自引：0，他引：5
T. Delworth R. Stouffer K. Dixon M. Spelman T. Knutson A. Broccoli P. Kushner R. Wetherald 《Climate Dynamics》2002,19(7):555-574
A review is presented of the development and simulation characteristics of the most recent version of a global coupled model for climate variability and change studies at the Geophysical Fluid Dynamics Laboratory, as well as a review of the climate change experiments performed with the model. The atmospheric portion of the coupled model uses a spectral technique with rhomboidal 30 truncation, which corresponds to a transform grid with a resolution of approximately 3.75° longitude by 2.25° latitude. The ocean component has a resolution of approximately 1.875° longitude by 2.25° latitude. Relatively simple formulations of river routing, sea ice, and land surface processes are included. Two primary versions of the coupled model are described, differing in their initialization techniques and in the specification of sub-grid scale oceanic mixing of heat and salt. For each model a stable control integration of near millennial scale duration has been conducted, and the characteristics of both the time-mean and variability are described and compared to observations. A review is presented of a suite of climate change experiments conducted with these models using both idealized and realistic estimates of time-varying radiative forcing. Some experiments include estimates of forcing from past changes in volcanic aerosols and solar irradiance. The experiments performed are described, and some of the central findings are highlighted. In particular, the observed increase in global mean surface temperature is largely contained within the spread of simulated global mean temperatures from an ensemble of experiments using observationally-derived estimates of the changes in radiative forcing from increasing greenhouse gases and sulfate aerosols. 相似文献
8.
The role of cloud cover in determining the sensitivity of climate has been a source of great uncertainty. This article reviews the distributions of cloud cover change from several climate sensitivity experiments conducted at the Geophysical Fluid Dynamics Laboratory of NOAA (GFDL) and other institutions. Two of the sensitivity experiments conducted at GFDL used a general circulation model with a limited computational domain and idealized geography, whereas three other experiments were conducted by the use of a global model with realistic geography. A thermal forcing imposed was either a change of solar constant or that of the CO2-concentration in the atmosphere. It was found that in all five cases, clouds were decreased in the moist, convectively active regions such as the tropical and middle latitude rainbelts, whereas they increased in the stable region near the model surface from middle to higher latitudes. In addition, cloud also increased in the lower model stratosphere and generally decreased in the middle and upper troposphere for practically all latitudes.A comparison of the cloud changes obtained from investigations carried out at other institutions reveals certain qualitative (but not necessarily quantitative) similarities to the GFDL results. These similarities include a general reduction of tropospheric cloud cover especially in the vicinity of the rainbelts, a general increase of lower stratospheric cloud cover for almost all latitudes and an increase of low stratiform cloud in high latitudes. 相似文献
9.
To investigate the hydrologic changes of climate in response to an increase of CO2-concentration in the atmosphere, the results from numerical experiments with three climate models are analyzed and compared
with each other. All three models consist of an atmospheric general circulation model and a simple mixed layer ocean with
a horizontally uniform heat capacity. The first model has a limited computational domain and simple geography with a flat
land surface. The second model has a global computational domain with realistic geography. The third model is identical to
the second model except that it has a higher computational resolution. In each numerical experiment, the CO2-induced change of climate is evaluated based upon a comparison between the two climates of a model with normal and four times
the normal concentration of carbon dioxide in air.
It is noted that the zonal mean value of soil moisture in summer reduces significantly in two separate zones of middle and
high latitudes in response to the increase of the CO2-concentration in air. This CO2-induced summer dryness results not only from the earlier ending of the snowmelt season, but also from the earlier occurrence
of the spring to summer reduction in rainfall rate. The former effect is particularly important in high latitudes, whereas
the latter effect becomes important in middle latitudes. Other statistically significant changes include large increases in
both soil moisture and runoff rate in high latitudes of a model during most of the annual cycle with the exception of the
summer season. The penetration of moisture-rich, warm air into high latitudes is responsible for these increases. 相似文献
10.
Global climate change is a qualitatively distinct, and very significant, addition to the spectrum of environmental health
hazards encountered by humankind. Historically, environmental health concerns have focused on toxicological or microbiological
risks to health from local exposures. However, the scale of environmental health hazards is today increasing; indeed, the
burgeoning human impact on the environment has begun to alter global biophysical systems (such as the climate system). As
a consequence, a range of larger-scale environmental hazards to human population health has emerged. This includes the health
risks posed by climate change, stratospheric ozone depletion, loss of biodiversity, stresses on terrestrial and ocean food-producing
systems, changes in hydrological systems and the supplies of freshwater, and the global spread of persistent organic pollutants.
Appreciation of this scale and type of influence on human health entails an ecological perspective — a perspective that recognises
that the foundations of long-term good health in populations reside in the continued stability and functioning of the biosphere's
"life-supporting" ecological and physical systems.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献