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1.
We here use a coupled atmosphere-surface single column climate model to illustrate how the CFRAM, a new climate feedback analysis
framework formulated in Part I of the two-part series papers, can be applied to isolate individual contributions to the total
temperature change of a climate system from the external forcing alone, and from each of individual physical and dynamical
processes associated with the energy transfer with the space and within the climate system. We demonstrate that the isolation
of individual feedbacks in the CFRAM is achieved without referencing to a virtual climate system as in the online feedback
suppression method. We show that partial temperature changes estimated by the online feedback suppression method include the
“compensating effects” of other feedbacks when the feedback under consideration is suppressed. The partial temperature changes
are addable in the CFRAM but they are not in the online feedback suppression method. We also apply the CFRAM to isolate the
contributions to the lapse rate feedback from individual physical and dynamical feedback processes. We show that the lapse
rate feedback includes not only the partial effect of each feedback that directly contributes to energy flux perturbations
at the TOA (such as water vapor feedback), but also the total effects of those feedbacks that do not contribute to energy
flux perturbations at the TOA (such as evaporation and moist convection feedbacks). Because the contributions to the lapse
rate feedback from various physical and dynamical processes tend to cancel one another, the net lapse rate feedback is a residual
of many large terms. This leads to a large uncertainty not only in estimating the lapse rate feedback itself, but also in
other feedbacks whose effects are either partially or totally lumped into the lapse rate feedback. 相似文献
2.
This paper examines several prominent thermodynamic and dynamic factors responsible for the meridional and vertical warming
asymmetries using a moist coupled atmosphere–surface radiative transportive four-box climate model. A coupled atmosphere–surface
feedback analysis is formulated to isolate the direct response to an anthropogenic greenhouse gas forcing from individual
local feedbacks (water vapor, evaporation, surface sensible heat flux, and ice-albedo), and from the non-local dynamical feedback.
Both the direct response and response to water vapor feedback are stronger in low latitudes. The joint effect of the ice-albedo
and dynamical greenhouse-plus feedbacks acts to amplify the high latitude surface warming whereas both the evaporation and
dynamical greenhouse-minus feedbacks cause a reduction of the surface warming in low latitudes. The enhancement (reduction)
of local feedbacks in high (low) latitudes in response to the non-local dynamic feedback further strengthens the polar amplification
of the surface warming. Both the direct response and response to water vapor feedback lead to an increase of lapse rate in
both low and high latitudes. The stronger total dynamic heating in the mean state in high latitudes is responsible for a larger
increase of lapse rate in high latitudes in the direct response and response to water vapor feedback. The local evaporation
and surface sensible heat flux feedbacks reduce the lapse rate both in low and high latitudes through cooling the surface
and warming the atmosphere. The much stronger evaporation feedback leads to a final warming in low latitudes that is stronger
in the atmosphere than the surface. 相似文献
3.
Statistical and dynamical assessment of vegetation feedbacks on climate over the boreal forest 总被引:1,自引:1,他引:0
Vegetation feedbacks over Asiatic Russia are assessed through a combined statistical and dynamical approach in a fully coupled
atmosphere–ocean–land model, FOAM-LPJ. The dynamical assessment is comprised of initial value ensemble experiments in which
the forest cover fraction is initially reduced over Asiatic Russia, replaced by grass cover, and then the climatic response
is determined. The statistical feedback approach, adopted from previous studies of ocean–atmosphere interactions, is applied
to compute the feedback of forest cover on subsequent temperature and precipitation in the control simulation. Both methodologies
indicate a year-round positive feedback on temperature and precipitation, strongest in spring and moderately substantial in
summer. Reduced boreal forest cover enhances the surface albedo, leading to an extended snow season, lower air temperatures,
increased atmospheric stability, and enhanced low cloud cover. Changes in the hydrological cycle include diminished transpiration
and moisture recycling, supporting a reduction in precipitation. The close agreement in sign and magnitude between the statistical
and dynamical feedback assessments testifies to the reliability of the statistical approach. An additional statistical analysis
of monthly vegetation feedbacks over Asiatic Russia reveals a robust positive feedback on air temperature of similar quantitative
strength in two coupled models, FOAM-LPJ and CAM3–CLM3, and the observational record.
CCR Contribution # 931. 相似文献
4.
The radiative forcings and feedbacks that determine Earth’s climate sensitivity are typically defined at the top-of-atmosphere (TOA) or tropopause, yet climate sensitivity itself refers to a change in temperature at the surface. In this paper, we describe how TOA radiative perturbations translate into surface temperature changes. It is shown using first principles that radiation changes at the TOA can be equated with the change in energy stored by the oceans and land surface. This ocean and land heat uptake in turn involves an adjustment of the surface radiative and non-radiative energy fluxes, with the latter being comprised of the turbulent exchange of latent and sensible heat between the surface and atmosphere. We employ the radiative kernel technique to decompose TOA radiative feedbacks in the IPCC Fourth Assessment Report climate models into components associated with changes in radiative heating of the atmosphere and of the surface. (We consider the equilibrium response of atmosphere-mixed layer ocean models subjected to an instantaneous doubling of atmospheric CO2). It is shown that most feedbacks, i.e., the temperature, water vapor and cloud feedbacks, (as well as CO2 forcing) affect primarily the turbulent energy exchange at the surface rather than the radiative energy exchange. Specifically, the temperature feedback increases the surface turbulent (radiative) energy loss by 2.87 W m?2 K?1 (0.60 W m?2 K?1) in the multimodel mean; the water vapor feedback decreases the surface turbulent energy loss by 1.07 W m?2 K?1 and increases the surface radiative heating by 0.89 W m?2 K?1; and the cloud feedback decreases both the turbulent energy loss and the radiative heating at the surface by 0.43 and 0.24 W m?2 K?1, respectively. Since changes to the surface turbulent energy exchange are dominated in the global mean sense by changes in surface evaporation, these results serve to highlight the fundamental importance of the global water cycle to Earth’s climate sensitivity. 相似文献
5.
‘Modelling the Arctic Boundary Layer: An Evaluation of Six Arcmip Regional-Scale Models using Data from the Sheba Project’ 总被引:3,自引:0,他引:3
Michael Tjernström Mark Žagar Gunilla Svensson John J. Cassano Susanne Pfeifer Annette Rinke Klaus Wyser Klaus Dethloff Colin Jones Tido Semmler Michael Shaw 《Boundary-Layer Meteorology》2005,117(2):337-381
A primary climate change signal in the central Arctic is the melting of sea ice. This is dependent on the interplay between
the atmosphere and the sea ice, which is critically dependent on the exchange of momentum, heat and moisture at the surface.
In assessing the realism of climate change scenarios it is vital to know the quality by which these exchanges are modelled
in climate simulations. Six state-of-the-art regional-climate models are run for one year in the western Arctic, on a common
domain that encompasses the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment ice-drift track. Surface variables,
surface fluxes and the vertical structure of the lower troposphere are evaluated using data from the SHEBA experiment. All
the models are driven by the same lateral boundary conditions, sea-ice fraction and sea and sea-ice surface temperatures.
Surface pressure, near-surface air temperature, specific humidity and wind speed agree well with observations, with a falling
degree of accuracy in that order. Wind speeds have systematic biases in some models, by as much as a few metres per second.
The surface radiation fluxes are also surprisingly accurate, given the complexity of the problem. The turbulent momentum flux
is acceptable, on average, in most models, but the turbulent heat fluxes are, however, mostly unreliable. Their correlation
with observed fluxes is, in principle, insignificant, and they accumulate over a year to values an order of magnitude larger
than observed. Typical instantaneous errors are easily of the same order of magnitude as the observed net atmospheric heat
flux. In the light of the sensitivity of the atmosphere–ice interaction to errors in these fluxes, the ice-melt in climate
change scenarios must be viewed with considerable caution. 相似文献
6.
Yoo-Geun Ham Jong-Seong Kug In-Sik Kang Fei-Fei Jin Axel Timmermann 《Climate Dynamics》2010,34(6):905-917
The impacts of diurnal atmosphere–ocean (air–sea) coupling on tropical climate simulations are investigated using the SNU
coupled GCM. To investigate the effect of the atmospheric and oceanic diurnal cycles on a climate simulation, a 1-day air–sea
coupling interval experiment is compared to a 2-h coupling experiment. As previous studies have suggested, cold temperature
biases over equatorial western Pacific regions are significantly reduced when diurnal air–sea coupling strategy is implemented.
This warming is initiated by diurnal rectification and amplified further by the air–sea coupled feedbacks. In addition to
its effect on the mean climatology, the diurnal coupling has also a distinctive impact on the amplitude of the El Nino-Southern
Oscillation (ENSO). It is demonstrated that a weakening of the ENSO magnitude is caused by reduced (increased) surface net
heat fluxes into the ocean during El Nino (La Nina) events. Primarily, decreased (increased) incoming shortwave radiation
during El Nino (La Nina) due to cloud shading is responsible for the net heat fluxes associated with ENSO. 相似文献
7.
The sensitivity of the global climate is essentially determined by the radiative damping of the global mean surface temperature
anomaly through the outgoing radiation from the top of the atmosphere (TOA). Using the TOA fluxes of terrestrial and reflected
solar radiation obtained from the Earth radiation budget experiment (ERBE), this study estimates the magnitude of the overall
feedback, which modifies the radiative damping of the annual variation of the global mean surface temperature, and compare
it with model simulations. Although the pattern of the annually varying anomaly is quite different from that of the global
warming, the analysis conducted here may be used for assessing the systematic bias of the feedback that operates on the CO2-induced warming of the surface temperature. In the absence of feedback effect, the outgoing terrestrial radiation at the
TOA is approximately follows the Stefan-Boltzmann’s fourth power of the planetary emission temperature. However, it deviates
significantly from the blackbody radiation due to various feedbacks involving water vapor and cloud cover. In addition, the
reflected solar radiation is altered by the feedbacks involving sea ice, snow and cloud, thereby affecting the radiative damping
of surface temperature. The analysis of ERBE reveals that the radiative damping is weakened by as much as 70% due to the overall
effect of feedbacks, and is only 30% of what is expected for the blackbody with the planetary emission temperature. Similar
feedback analysis is conducted for three general circulation models of the atmosphere, which was used for the study of cloud
feedback in the preceding study. The sign and magnitude of the overall feedback in the three models are similar to those of
the observed. However, when it is subdivided into solar and terrestrial components, they are quite different from the observation
mainly due to the failure of the models to simulate individually the solar and terrestrial components of the cloud feedback.
It is therefore desirable to make the similar comparison not only for the overall feedback but also for its individual components
such as albedo- and cloud-feedbacks. Although the pattern of the annually-varying anomaly is quite different from that of
global warming, the methodology of the comparative analysis presented here may be used for the identification of the systematic
bias of the overall feedback in a model. A proposal is made for the estimation of the best guess value of climate sensitivity
using the outputs from many climate models submitted to the Intergovernmental panel on Climate Change. 相似文献
8.
In this study, a coupled atmosphere-surface “climate feedback-response analysis method” (CFRAM) was applied to the slab ocean model version of the NCAR CCSM3.0 to understand the tropospheric warming due to a doubling of CO2 concentration through quantifying the contributions of each climate feedback process. It is shown that the tropospheric warming displays distinct meridional and vertical patterns that are in a good agreement with the multi-model mean projection from the IPCC AR4. In the tropics, the warming in the upper troposphere is stronger than in the lower troposphere, leading to a decrease in temperature lapse rate, whereas in high latitudes the opposite it true. In terms of meridional contrast, the lower tropospheric warming in the tropics is weaker than that in high latitudes, resulting in a weakened meridional temperature gradient. In the upper troposphere the meridional temperature gradient is enhanced due to much stronger warming in the tropics than in high latitudes. Using the CFRAM method, we analyzed both radiative feedbacks, which have been emphasized in previous climate feedback analysis, and non-radiative feedbacks. It is shown that non-radiative (radiative) feedbacks are the major contributors to the temperature lapse rate decrease (increase) in the tropical (polar) region. Atmospheric convection is the leading contributor to temperature lapse rate decrease in the tropics. The cloud feedback also has non-negligible contributions. In the polar region, water vapor feedback is the main contributor to the temperature lapse rate increase, followed by albedo feedback and CO2 forcing. The decrease of meridional temperature gradient in the lower troposphere is mainly due to strong cooling from convection and cloud feedback in the tropics and the strong warming from albedo feedback in the polar region. The strengthening of meridional temperature gradient in the upper troposphere can be attributed to the warming associated with convection and cloud feedback in the tropics. Since convection is the leading contributor to the warming differences between tropical lower and upper troposphere, and between the tropical and polar regions, this study indicates that tropical convection plays a critical role in determining the climate sensitivity. In addition, the CFRAM analysis shows that convective process and water vapor feedback are the two major contributors to the tropical upper troposphere temperature change, indicating that the excessive upper tropospheric warming in the IPCC AR4 models may be due to overestimated warming from convective process or underestimated cooling due to water vapor feedback. 相似文献
9.
J. Venkata Ratnam Filippo Giorgi Akshara Kaginalkar Stefano Cozzini 《Climate Dynamics》2009,33(1):119-139
A regional coupled atmosphere–ocean model was developed to study the role of air–sea interactions in the simulation of the
Indian summer monsoon. The coupled model includes the regional climate model (RegCM3) as atmospheric component and the regional
ocean modeling system (ROMS) as oceanic component. The two-way coupled model system exchanges sea surface temperature (SST)
from the ocean to the atmospheric model and surface wind stress and energy fluxes from the atmosphere to the ocean model.
The coupled model is run for four years 1997, 1998, 2002 and 2003 and the results are compared with observations and atmosphere-only
model runs employing Reynolds SSTs as lower boundary condition. It is found that the coupled model captures the main features
of the Indian monsoon and simulates a substantially more realistic spatial and temporal distribution of monsoon rainfall compared
to the uncoupled atmosphere-only model. The intraseasonal oscillations are also better simulated in the coupled model compared
to the atmosphere-only model. These improvements are due to a better representation of the feedbacks between the SST and convection
and highlight the importance of air–sea coupling in the simulation of the Indian monsoon. 相似文献
10.
Aaron Anthony Boone Isabelle Poccard-Leclercq Yongkang Xue Jinming Feng Patricia de Rosnay 《Climate Dynamics》2010,35(1):127-142
The West African monsoon (WAM) circulation and intensity have been shown to be influenced by the land surface in numerous
numerical studies using regional scale and global scale atmospheric climate models (RCMs and GCMs, respectively) over the
last several decades. The atmosphere–land surface interactions are modulated by the magnitude of the north–south gradient
of the low level moist static energy, which is highly correlated with the steep latitudinal gradients of the vegetation characteristics
and coverage, land use, and soil properties over this zone. The African Multidisciplinary Monsoon Analysis (AMMA) has organised
comprehensive activities in data collection and modelling to further investigate the significance land–atmosphere feedbacks.
Surface energy fluxes simulated by an ensemble of land surface models from AMMA Land-surface Model Intercomparison Project
(ALMIP) have been used as a proxy for the best estimate of the “real world” values in order to evaluate GCM and RCM simulations
under the auspices of the West African Monsoon Modelling Experiment (WAMME) project, since such large-scale observations do
not exist. The ALMIP models have been forced in off-line mode using forcing based on a mixture of satellite, observational,
and numerical weather prediction data. The ALMIP models were found to agree well over the region where land–atmosphere coupling
is deemed to be most important (notably the Sahel), with a high signal to noise ratio (generally from 0.7 to 0.9) in the ensemble
and a inter-model coefficient of variation between 5 and 15%. Most of the WAMME models simulated spatially averaged net radiation
values over West Africa which were consistent with the ALMIP estimates, however, the partitioning of this energy between sensible
and latent heat fluxes was significantly different: WAMME models tended to simulate larger (by nearly a factor of two) monthly
latent heat fluxes than ALMIP. This results due to a positive precipitation bias in the WAMME models and a northward displacement
of the monsoon in most of the GCMs and RCMs. Another key feature not found in the WAMME models is peak seasonal latent heat
fluxes during the monsoon retreat (approximately a month after the peak precipitation rates) from soil water stores. This
is likely related to the WAMME northward bias of the latent heat flux gradient during the WAM onset. 相似文献
11.
Radiative forcing has been widely used as a metric of climate change, i.e. as a measure by which various contributors to a net surface temperature change can be quantitatively compared. The extent to which this concept is valid for spatially inhomogeneous perturbations to the climate system is tested. A series of climate model simulations involving ozone changes of different spatial structure reveals that the climate sensitivity parameter is highly variable: for an ozone increase in the northern hemisphere lower stratosphere, it is more than twice as large as for a homogeneous CO2 perturbation. A global ozone perturbation in the upper troposphere, however, causes a significantly smaller surface temperature response than CO2. The variability of the climate sensitivity parameter is shown to be mostly due to the varying strength of the stratospheric water vapour feedback. The variability of the sea-ice albedo feedback modifies climate sensitivity of perturbations with the same vertical structure but a different horizontal structure. This feedback is also the origin of the comparatively larger climate sensitivity to perturbations restricted to the northern hemisphere extratropics. As cloud feedback does not operate independently from the other feedbacks, quantifying its effect is rather difficult. However, its effect on the variability of for horizontally and vertically inhomogeneous perturbations within one model framework seems to be comparatively small.This revised version was published online March 2005 with corrections to table 5. 相似文献
12.
The dynamic greenhouse: Feedback processes that may influence future concentrations of atmospheric trace gases and climatic change 总被引:3,自引:0,他引:3
Daniel A. Lashof 《Climatic change》1989,14(3):213-242
The sensitivity of the climate system to anthropogenic perturbations over the next century will be determined by a combination of feedbacks that amplify or damp the direct radiative effects of increasing concentrations of greenhouse gases. A number of important geophysical climate feedbacks, such as changes in water vapor, clouds, and sea ice albedo, are included in current climate models, but biogeochemical feedbacks such as changes in methane emissions, ocean CO2 uptake, and vegetation albedo are generally neglected. The relative importance of a wide range of feedbacks is assessed here by estimating the gain associated with each individual process. The gain from biogeochemical feedbacks is estimated to be 0.05–0.29 compared to 0.17–0.77 for geophysical climate feedbacks. The potentially most significant biogeochemical feedbacks are probably release of methane hydrates, changes in ocean chemistry, biology, and circulation, and changes in the albedo of the global vegetation. While each of these feedbacks is modest compared to the water vapor feedback, the biogeochemical feedbacks in combination have the potential to substantially increase the climate change associated with any given initial forcing.The views expressed are the author's: They do not express official views of the U.S. Government or the Environmental Protection Agency. 相似文献
13.
Filip Lefebre Xavier Fettweis Hubert Gallée Jean-Pascal Van Ypersele Philippe Marbaix Wouter Greuell Pierluigi Calanca 《Climate Dynamics》2005,25(1):99-116
A simulation of the 1991 summer has been performed over south Greenland with a coupled atmosphere–snow regional climate model
(RCM) forced by the ECMWF re-analysis. The simulation is evaluated with in-situ coastal and ice-sheet atmospheric and glaciological
observations. Modelled air temperature, specific humidity, wind speed and radiative fluxes are in good agreement with the
available observations, although uncertainties in the radiative transfer scheme need further investigation to improve the
model’s performance. In the sub-surface snow-ice model, surface albedo is calculated from the simulated snow grain shape and
size, snow depth, meltwater accumulation, cloudiness and ice albedo. The use of snow metamorphism processes allows a realistic
modelling of the temporal variations in the surface albedo during both melting periods and accumulation events. Concerning
the surface albedo, the main finding is that an accurate albedo simulation during the melting season strongly depends on a
proper initialization of the surface conditions which mainly result from winter accumulation processes. Furthermore, in a
sensitivity experiment with a constant 0.8 albedo over the whole ice sheet, the average amount of melt decreased by more than
60%, which highlights the importance of a correctly simulated surface albedo. The use of this coupled atmosphere–snow RCM
offers new perspectives in the study of the Greenland surface mass balance due to the represented feedback between the surface
climate and the surface albedo, which is the most sensitive parameter in energy-balance-based ablation calculations. 相似文献
14.
利用卫星和再分析数据,评估了区域气候模式Reg CM4对中国东部地区辐射收支的基本模拟能力,重点关注地表净短波(SNS)、地表净长波(SNL)、大气顶净短波(TNS)、大气顶净长波(TNL)4个辐射分量。结果表明:1)短波辐射的误差值在夏季较大,而长波辐射的误差值在冬季较大。但各辐射分量模拟误差的空间分布在冬、夏季都有较好的一致性。2)对于地表辐射通量,SNS表现为正偏差(向下净短波偏多),在各分量中误差最大,区域平均误差值近50 W/m2;SNL表现为负偏差(向上净长波偏多);对于大气顶辐射通量,TNS和TNL分别表现为"北负南正"的误差分布和整体正偏差。3)利用空间相关和散点线性回归方法对4个辐射分量的模拟误差进行归因分析,发现在云量、地表反照率、地表温度三个直接影响因子中,云量模拟误差的贡献最大,中国东部地区云量模拟显著偏少。 相似文献
15.
Quantifying the AMOC feedbacks during a 2×CO2 stabilization experiment with land-ice melting 总被引:1,自引:0,他引:1
The response of the Atlantic Meridional Overturning Circulation (AMOC) to an increase in atmospheric CO2 concentration is analyzed using the IPSL-CM4 coupled ocean–atmosphere model. Two simulations are integrated for 70 years
with 1%/year increase in CO2 concentration until 2×CO2, and are then stabilized for further 430 years. The first simulation takes land-ice melting into account, via a simple parameterization,
which results in a strong freshwater input of about 0.13 Sv at high latitudes in a warmer climate. During this scenario, the
AMOC shuts down. A second simulation does not include this land-ice melting and herein, the AMOC recovers after 200 years.
This behavior shows that this model is close to an AMOC shutdown threshold under global warming conditions, due to continuous
input of land-ice melting. The analysis of the origin of density changes in the Northern Hemisphere convection sites allows
an identification as to the origin of the changes in the AMOC. The processes that decrease the AMOC are the reduction of surface
cooling due to the reduction in the air–sea temperature gradient as the atmosphere warms and the local freshening of convection
sites that results from the increase in local freshwater forcing. Two processes also control the recovery of the AMOC: the
northward advection of positive salinity anomalies from the tropics and the decrease in sea-ice transport through the Fram
Strait toward the convection sites. The quantification of the AMOC related feedbacks shows that the salinity related processes
contribute to a strong positive feedback, while feedback related to temperature processes is negative but remains small as
there is a compensation between heat transport and surface heat flux in ocean–atmosphere coupled model. We conclude that in
our model, AMOC feedbacks amplify land-ice melting perturbation by 2.5. 相似文献
16.
E. D. Nadezhina E. K. Mol’kentin A. A. Kiselev A. A. Semioshina I. M. Shkol’nik 《Russian Meteorology and Hydrology》2011,36(6):371-382
An effect is studied of parameterization method of the methane flux from the wetlands of Siberia on the results of model estimates
carried out using the one-dimensional model of heat transfer in the soils. The results of computations of the regional climate
model of the Main Geophysical Laboratory are used as the input data of this model. The computation estimates of seasonal methane
flux variations at certain observation points are compared with the measured values of the methane flux. It is shown that
the optimal choice of methane flux parameterization at the use of the grid climate model data as the forcing should correspond
to the conditions of prevailing subgrid natural complex of one or another type of wetlands. A spatial distribution of methane
emission intensity under conditions of the present-day climate and at the end of the 21st century is obtained. The analysis
revealed that the methane fluxes in Western Siberia will increase by 1.5–2.5 times by the end of the 21st century. 相似文献
17.
The spatial and temporal variability of land carbon flux over the past one hundred years was investigated based on an empirical
model directly calculating soil respiration rate. Our model shows that during 1901–1995, about 44-89 PgC (equals to 0.5, 0.9
PgC/yr respectively) were absorbed by terrestrial biosphere. The simulated net ecosystem productivity (NEP) after the 1930s
was close to the estimated value of “ missing C sink” from deconvolution analysis. Most of the total carbon sink happened
during 1951–1985 with the estimated value of 33–50 PgC. Three major sinks were located in the tropics (10°S–10°N), Northern
mid-latitudes (30°–60°N) and Southern subtropics (10°–40°S). During 1940s-mid-1970s, carbon sinks by terrestrial ecosystem
increased with time, and decreased after the mid-1970s. These may be due to the changing of climate condition, as during the
1940s–1970s, temperature decreased and precipitation increased, while after the mid-1970s, an opposite climate situation occurred
with evident increasing in temperature and decreasing in precipitation. Usually, warmer and dryer climate condition is not
favor for carbon absorption by biosphere and even induces net carbon release from soil, while cooler and wetter condition
may induce more carbon sink. Our model results show that the net carbon flux is particularly dependent on moisture / precipitation
effect despite of temperature effect. The changing of climate in the past century may be a possible factor inducing increases
in carbon sink in addition to CO2 and N fertilizer.
This research was funded by CAS One Hundred Talents project and Knowledge Innovation Project of CAS(KZCX2-201). 相似文献
18.
19.
Peter H. Stone 《Dynamics of Atmospheres and Oceans》1978,2(2):123-139
The factors which control the total flux of energy across a latitude belt in the atmosphere—ocean system are determined by comparing the flux resulting from various approximations with the observed flux, and by using a one-dimensional heat-balance climate model to calculate the sensitivity of the flux to the efficiency of the dynamical transports. The results show that, as long as a hemisphere is in equilibrium and as long as the structure of the atmosphere—ocean system is dominated by the planetary scale, the total flux is constrained to peak near 35° latitude, the flux per unit area to peak near 45° latitude, and the magnitude of the flux is determined primarily by the solar constant, the size of the earth, the tilt of the earth's axis, and the hemispheric mean albedo. The magnitude of the flux is insensitive to the structure and dynamics of the atmosphere—ocean system, in part because of the high efficiency of the dynamical transport mechanisms and in part because of the negative correlation between local planetary albedo and local thermal emissions to space. These results explain why the total flux and its latitudinal distribution calculated in various experiments with the GFDL general circulation model experienced relatively little modification when the hydrological cycle, mountains, or oceans were removed from the system. 相似文献
20.
Arthur Prigent Joke F. Lbbecke Tobias Bayr Mojib Latif Christian Wengel 《Climate Dynamics》2020,54(5):2731-2744
A prominent weakening in equatorial Atlantic sea surface temperature (SST) variability, occurring around the year 2000, is investigated by means of observations, reanalysis products and the linear recharge oscillator (ReOsc) model. Compared to the time period 1982–1999, during 2000–2017 the May–June–July SST variability in the eastern equatorial Atlantic has decreased by more than 30%. Coupled air–sea feedbacks, namely the positive Bjerknes feedback and the negative net heat flux damping are important drivers for the equatorial Atlantic interannual SST variability. We find that the Bjerknes feedback weakened after 2000 while the net heat flux damping increased. The weakening of the Bjerknes feedback does not appear to be fully explainable by changes in the mean state of the tropical Atlantic. The increased net heat flux damping is related to an enhanced response of the latent heat flux to the SST anomalies (SSTa). Strengthened trade winds as well as warmer SSTs are suggested to increase the air–sea specific humidity difference and hence, enhancing the latent heat flux response to SSTa. A combined effect of those two processes is proposed to be responsible for the weakened SST variability in the eastern equatorial Atlantic. The ReOsc model supports the link between reduced SST variability, weaker Bjerknes feedback and stronger net heat flux damping. 相似文献