共查询到10条相似文献，搜索用时 109 毫秒
1.
M. Y. Totagi 《大气科学进展》1994,11(4):491-498
The study of large-scale atmospheric turbulence and transport processes is of vital importance in the general circulation of the atmosphere. The governing equations of the power and cross-spectra for the atmospheric motion and transports in the domain of wave number frequency space have been derived. The contributions of the nonlinear interactions of the atmospheric waves in velocity and temperature fields to the conversion of kinetic and potential energies and to the meridional transports of angular momentum and sensible heat in the atmosphere have been discussed. 相似文献
2.
We analyze the sensitivity of the oceanic thermohaline circulation (THC) regarding perturbations in fresh water flux for a range of coupled oceanic general circulation — atmospheric energy balance models. The energy balance model (EBM) predicts surface air temperature and fresh water flux and contains the feedbacks due to meridional transports of sensible and latent heat. In the coupled system we examine a negative perturbation in run-off into the southern ocean and analyze the role of changed atmospheric heat transports and fresh water flux. With mixed boundary conditions (fixed air temperature and fixed surface fresh water fluxes) the response is characterized by a completely different oceanic heat transport than in the reference case. On the other hand, the surface heat flux remains roughly constant when the air temperature can adjust in a model where no anomalous atmospheric transports are allowed. This gives an artificially stable system with nearly unchanged oceanic heat transport. However, if meridional heat transports in the atmosphere are included, the sensitivity of the system lies between the two extreme cases. We find that changes in fresh water flux are unimportant for the THC in the coupled system. 相似文献
3.
Leads and polynyas have a great impact on the energy budget of the polar ocean and atmosphere. Since atmospheric general
circulation models are not able to resolve the spatial scales of these inhomogeneities, it is necessary to include the effect
of fractional sub-grid scale sea-ice inhomogeneities on climate by a suitable parametrization. In order to do this we have
divided each model grid-cell into an ice-covered and an ice-free part. Nevertheless, a numerical model requires effective
transports representative for the whole grid-box. A simple procedure would be to use grid averages of the surface parameters
for the calculation of the surface fluxes. However, as the surface fluxes are non-linearly dependent on the surface properties,
the fluxes over ice and open water should be calculated separately according to the individual surface-layer structure of
each surface type. Then these local fluxes should be averaged to obtain representative fluxes. Sensitivity experiments with
the Hamburg atmospheric general circulation model ECHAM3 clearly show that a subgrid scale distribution of sea ice is a dominant
factor controlling the exchange processes between ocean and atmosphere in the Arctic. The heat and water vapour transports
are strongly enhanced leading to a significant warming and moistening of the polar troposphere. This affects the atmospheric
circulation in high- and mid-latitudes; e.g. the stationary lows are modified and the transient cyclonic activity over the
subpolar oceans is reduced. A pronounced impact of sub-grid scale sea-ice distribution on the model climate can only be obtained
when the non-linear behaviour of the surface exchange processes is considered by a proper, physically based, averaging of
the surface fluxes. A simple linear averaging of surface parameters is not sufficient.
Received: 13 September 1994 / Accepted: 25 July 1995 相似文献
4.
S. Rahmstorf 《Climate Dynamics》1996,12(12):799-811
The 'conveyor belt' circulation of the Atlantic Ocean transports large amounts of heat northward, acting as a heating system
for the northern North Atlantic region. It is widely thought that this circulation is driven by atmospheric freshwater export
from the Atlantic catchment region, and that it transports freshwater northward to balance the loss to the atmosphere. Using
results from a simple conceptual model and a global circulation model, it is argued here that the freshwater loss to the atmosphere
arises mainly in the subtropical South Atlantic and is balanced by northward freshwater transport in the wind-driven subtropical
gyre, while the thermohaline circulation transports freshwater southward. It is further argued that the direction of freshwater transport is closely linked to the dynamical regime and stability
of the 'conveyor belt': if its freshwater transport is indeed southward, then its flow is purely thermally driven and inhibited
by the freshwater forcing. In this case the circulation is not far from Stommel's saddle-node bifurcation, and a circulation
state without NADW formation would also be stable.
Received: 10 February 1996 / Accepted: 30 May 1996 相似文献
5.
The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled model without flux adjustments 总被引：47，自引：17，他引：30
C. Gordon C. Cooper C. A. Senior H. Banks J. M. Gregory T. C. Johns J. F. B. Mitchell R. A. Wood 《Climate Dynamics》2000,16(2-3):147-168
Results are presented from a new version of the Hadley Centre coupled model (HadCM3) that does not require flux adjustments
to prevent large climate drifts in the simulation. The model has both an improved atmosphere and ocean component. In particular,
the ocean has a 1.25° × 1.25° degree horizontal resolution and leads to a considerably improved simulation of ocean heat transports
compared to earlier versions with a coarser resolution ocean component. The model does not have any spin up procedure prior
to coupling and the simulation has been run for over 400 years starting from observed initial conditions. The sea surface
temperature (SST) and sea ice simulation are shown to be stable and realistic. The trend in global mean SST is less than 0.009 °C
per century. In part, the improved simulation is a consequence of a greater compatibility of the atmosphere and ocean model
heat budgets. The atmospheric model surface heat and momentum budget are evaluated by comparing with climatological ship-based
estimates. Similarly the ocean model simulation of poleward heat transports is compared with direct ship-based observations
for a number of sections across the globe. Despite the limitations of the observed datasets, it is shown that the coupled
model is able to reproduce many aspects of the observed heat budget.
Received: 1 October 1998 / Accepted: 20 July 1999 相似文献
6.
大气探测高技术及应用研究进展 总被引：7，自引：1，他引：6
大气探测技术是支撑大气科学,特别是大气物理和大气环境学科发展的重要基础,其主要任务是发展新的探测和试验手段、原理和方法,为认识大气运动以及大气中各种物理、化学、生物过程的基本规律及其与周围环境的相互作用提供技术手段和方法。除了充分利用国内外已有的成熟技术和产品对大气科学发展提供支持外,大气探测还存在一系列科学与技术问题需要研究和开发,这也是大气探测科学与高技术的前沿。本文从强对流和降水探测技术、雷电探测技术、云特性探测技术、臭氧和气溶胶等大气成分探测技术、地基GPS观测反演大气和海洋参数、大气与环境综合探测平台六个方面综述近五年来中国科学院大气物理研究所在地面大气探测高技术研发、实验观测及相关研究领域所取得的一些主要进展,并对未来发展进行展望。 相似文献
7.
J. Bendtsen 《Climate Dynamics》2002,18(7):595-609
A simple coupled ocean, atmosphere and sea-ice model is presented. The idealised model consists of a zonally averaged land and ocean strip of constant angular width extending from pole to pole. The meridional energy transport in the ocean is modelled by contributions from the large scale thermohaline overturning cells and from horizontal diffusive fluxes. The atmospheric meridional energy transports are parametrised as diffusive fluxes in addition to advective transports in the Hadley domain. This parametrisation resolves the equatorward moisture transport as well as the poleward transport of potential energy in the upper branch of the Hadley circulation. The model reproduces the annual averaged meridional energy transports in the climate system with a small number of free model parameters. The basic feedbacks between the three climatic components are studied by investigating the model's sensitivity towards reductions in the solar insolation. It is found that the meridional energy transport in the ocean does not amplify the ice albedo feedback. This has important implications for modelling the climate sensitivity in atmosphere-only models, as these would exaggerate the sensitivity to changes in the solar insolation if their parametrisations of the meridional energy transport are constrained by surface temperatures. The role of the dependence of the atmospheric transports on the meridional temperature gradient is shown to have a significant influence on the sensitivity on the coupled model, and the inclusion of seasonal cycles greatly increase the models sensitivity. The Hadley circulation does significantly alter the strength of the ice-albedo feedback in the coupled model. The idealised configuration of the model makes it a useful tool for studying the feedbacks in the ocean-atmosphere-sea ice system in the context of the "Snowball Earth" hypothesis. 相似文献
8.
The global heat balance: heat transports in the atmosphere and ocean 总被引：10，自引：0，他引：10
The heat budget has been computed locally over the entire globe for each month of 1988 using compatible top-of-the-atmosphere radiation from the Earth Radiation Budget Experiment combined with European Centre for Medium Range Weather Forecasts atmospheric data. The effective heat sources and sinks (diabatic heating) and effective moisture sources and sinks for the atmosphere are computed and combined to produce overall estimates of the atmospheric energy divergence and the net flux through the Earth's surface. On an annual mean basis, this is directly related to the divergence of the ocean heat transport, and new computations of the ocean heat transport are made for the ocean basins. Results are presented for January and July, and the annual mean for 1988, along with a comprehensive discussion of errors. While the current results are believed to be the best available at present, there are substantial shortcomings remaining in the estimates of the atmospheric heat and moisture budgets. The issues, which are also present in all previous studies, arise from the diurnal cycle, problems with atmospheric divergence, vertical resolution, spurious mass imbalances, initialized versus uninitialized atmospheric analyses, and postprocessing to produce the atmospheric archive on pressure surfaces. Over land, additional problems arise from the complex surface topography, so that computed surface fluxes are more reliable over the oceans. The use of zonal means to compute ocean transports is shown to produce misleading results because a considerable part of the implied ocean transports is through the land. The need to compute the heat budget locally is demonstrated and results indicate lower ocean transports than in previous residual calculations which are therefore more compatible with direct ocean estimates. A Poisson equation is solved with appropriate boundary conditions of zero normal heat flux through the continental boundaries to obtain the ocean heat transport. Because of the poor observational data base, adjustments to the surface fluxes are necessary over the southern oceans. Error bars are estimated based on the large-scale spurious residuals over land of 30 W m–2 over 1000 km scales (1012 m2). In the Atlantic Ocean, a northward transport emerges at all latitudes with peak values of 1.1±0.2 PW (1 standard error) at 20 to 30°N. Comparable values are achieved in the Pacific at 20°N, so that the total is 2.1±0.3 PW. The peak southward transport is at 15 to 20°S of 1.9±0.3 PW made up of strong components from both the Pacific and Indian Oceans and with a heat flux from the Pacific into the Indian Ocean in the Indonesian throughflow. The pattern of poleward heat fluxes is suggestive of a strong role for Ekman transports in the tropical regions. 相似文献
9.
Kevin E. Trenberth 《Dynamics of Atmospheres and Oceans》1979,4(1):57-64
A survey is made of the published estimates of the components of the poleward flux of energy by the atmosphere in the Southern Hemisphere in order to determine the total atmospheric transport. Together with recent measurements by satellite of the Earth's radiation budget this allows a new estimate of the required poleward energy transport by the oceans in the Southern Hemisphere for mean annual conditions. Results show that the ocean and atmosphere each contribute similar amounts for 0–30°S and that the ocean probably also transports about one third of the total at 60°S. The latter is in contrast to similar latitudes in the Northern Hemisphere where the ocean transport is negligible, but consistent with the different distribution of land and sea in the two hemispheres. 相似文献
