The effect of a regional increase in ocean surface roughness on the tropospheric circulation: a GCM experiment

The sensitivity of the atmospheric circulation to an increase in ocean surface roughness in the Southern Hemisphere storm track is investigated in a paired general circulation model experiment. Such a change in sea roughness could be induced by ocean waves generated by storms. Two extended permanent-July runs are made. One with standard sea surface roughness, the other with ten times as a large surface roughness over open sea poleward of 40° S. The regional increase in ocean surface roughness significantly modifies the tropospheric circulation in the Southern Hemisphere. The strongest effect is the reduction of tropospheric winds (by 2 m/s or 10%) above the area with increased roughness. The poleward eddy momentum flux is reduced in the upper troposphere and the meridional eddy sensible heat flux is reduced in the lower troposphere. Zonal mean and eddy kinetic energy are consistently reduced.     

Seasonal oceanic heat transports computed from an atmospheric model

Seasonal estimates of the oceanic poleward heat transport are obtained using a climate model that is a global atmospheric general circulation model on an 8° × 10° grid. The climate model is used to calculate the surface heat flux into each ocean grid point for each day of the year. The rate of ocean heat storage is calculated using climatological surface temperatures, mixed layer depths, and ice amounts. By assuming that the rate of change of heat storage in the deep ocean is spatially constant, the horizontal transports are calculated from the vertical fluxes and the upper ocean storage rates. The oceanic meridional transport for each latitude and for each ocean basin are derived, and results are compared with other calculations of the seasonal transports. In the Northern Hemisphere, comparisons between the simulated seasonal transports indicate that the annual variation is much greater in the Pacific than in the Atlantic.     

Annual oceanic heat transports computed from an atmospheric model

Mean annual estimates of the oceanic poleward energy transport are obtained using a global atmospheric general circulation model. The computations are carried out by using the atmospheric model to determine the net annual heat flux into the ocean on an 8° × 10° grid. Assuming no net annual heat storage, the annual surface heat fluxes into any zonal band must be accompanied by a corresponding meridional heat transport in the ocean. Heat is transported northward at all latitudes in the Atlantic Ocean and is transported poleward in both hemispheres in the Pacific Ocean. To account for the net northward transport throughout the Atlantic, heat is transported into the Atlantic from the Indian and Pacific basins. The results are compared with several recent direct and indirect calculations of oceanic meridional heat transports.     

On the response of the oceanic wind-driven circulation to atmospheric CO2 increase

A global, flux-corrected climate model is employed to predict the surface wind stress and associated wind-driven oceanic circulation for climate states corresponding to a doubling and quadrupling of the atmospheric CO₂ concentration in a simple 1% per year CO₂ increase scenario. The model indicates that in response to CO₂ increase, the position of zero wind stress curl in the mid-latitudes of the Southern Hemisphere shifts poleward. In addition, the wind stress intensifies significantly in the mid-latitudes of the Southern Hemisphere. As a result, the rate of water circulation in the subpolar meridional overturning cell in the Southern Ocean increases by about 6 Sv (1 Sv=10⁶ m³ s⁻¹) for doubled CO₂ and by 12 Sv for quadrupled CO₂, implying an increase of deep water upwelling south of the circumpolar flow and an increase of Ekman pumping north of it. In addition, the changes in the wind stress and wind stress curl translate into changes in the horizontal mass transport, leading to a poleward expansion of the subtropical gyres in both hemispheres, and to strengthening of the Antarctic Circumpolar Current. Finally, the intensified near-surface winds over the Southern Ocean result in a substantial increase of mechanical energy supply to the ocean general circulation.     

热带印度洋与全球大气相互作用的信息传输特征分析

基于气象场信息源汇概念和定义方法, 使用海表温度(SST)和位势高度场(GH)资料计算热带印度洋和全球大气相互作用过程中的信息传递, 给出了热带印度洋(20°S～20°N, 50°E～100°E)与热带地区、北半球和南半球大气之间的信息传递的区域分布特征, 并分析热带印度洋与大气相互作用中信息传递特征的季节差异和年代际变化。研究结果表明, 热带印度洋信息源主要分布在(10°S～10°N, 60°E～90°E)的区域内, 北半球和南半球大气信息汇均呈现显著的带状分布, 且主要分布在中纬度地区, 而热带地区的大气信息汇则主要分布于热带中东太平洋上空。热带印度洋对处在冬半年的半球的影响更强, 不同季节下热带印度洋与大气相互作用中的信息源汇证实了这一可能性。同时, 热带印度洋与大气之间的信息传递特征在20世纪70年代末期的年代际气候转型前后南北半球的变化不太一致:北半球大气对热带印度洋的响应存在不同程度的减弱, 南半球则存在不同程度的增强。     

The ice-covered Earth instability in a model of intermediate complexity

The ice-covered Earth instability found in energy balance models is studied with a zonal mean statistical dynamical atmospheric model coupled to a global mixed layer ocean model. The response of the model to changes in solar constant is examined in two parallel studies, one with and one without a fixed meridional heat transport (a Q-flux) being included in the ocean model. The Q-flux is derived so as to make the climate with the current value of the solar constant resemble the earths current climate. In both cases the climate displays a hysteresis loop as the solar constant decreases and then increases, with two equilibrium states being possible for a range of values of the solar constant. In the case without a Q-flux, as in energy balance models, one state corresponds to an ice-covered Earth, and the other is partially covered. In the case with a Q-flux, because the poleward Q-flux is stronger in the Southern Hemisphere, one state corresponds to an ice-covered Northern Hemisphere, but a Southern Hemisphere that is only partially ice-covered; the other state has much reduced ice-cover in both hemispheres. In the case when the Q-flux is present, the sensitivity of the state with smaller ice-cover is about half as much, and the hysteresis loop extends over a smaller range of values of the solar constant. Also in this case there is a strong ice-covered Earth instability that sets in when the solar constant is about 13–14% below the current value. However in the case without a Q-flux the ice-covered Earth instability virtually disappears. The different behavior is attributed to the much lower efficiency of the meridional heat transport in the case with no Q-flux. The behavior in this case may be more realistic for cold climates. The results in both cases confirm the simple analytical relation between global mean surface temperature and global ice area found in energy balance models.     

Energy transports by ocean and atmosphere based on an entropy extremum principle. Part II: Two-dimensional transports

Summary The maximum entropy production (MEP) principle used in Part J has been extended to separate the two-dimensional required energy transports determined from Nimbus 7 satellite net radiation measurements into atmospheric and oceanic components. In terms of the meridional component of the ocean transport vectors, results show northward ocean transports throughout the entire Atlantic ocean from southern hemisphere high latitudes to northern hemisphere polar regions, southward transports throughout the entire Indian Ocean, and poleward transports separated at approximately 10°S in the Pacific Ocean. The ocean transport patterns are consistent with well-known features concerning heat transport within the three ocean basins. However, uncertainty remains in the magnitudes of the transports. Because of the large remaining discrepancies between published estimates based on direct measurements and indirect estimates derived from energy budget methods, assessing the accuracy of the magnitudes is difficult, although there is evidence that the limited model resolution leads to synergistic biases in the North Atlantic and North Pacific. In terms of the crossmeridional energy transport component, results suggest that most of the net energy transfer in the tropics takes place within the ocean. In the southern hemisphere high latitudes, the Pacific and Indian Oceans export heat cross-meridionally to the Atlantic Ocean through the passages below Cape Horn and the Cape of Good Hope, although the magnitudes of these inter-ocean heat exchanges are small. Another important aspect of the southern hemisphere results is that poleward transports are dominated by the atmospheric component with strong zonal asymmetry. By contrast, in the northern hemisphere, atmospheric transports over the ocean are generally weaker than the corresponding southern hemisphere terms, indicating that the northern hemisphere oceans are relatively more effective in transferring heat poleward. Finally, poleward atmospheric transports over the continental areas exceed those over the ocean at equivalent latitudes as a result of the generally greater energy deficits over the land areas.With 7 Figures     

全球大气能量的时空特征及变化趋势分析

大气能量学是大气科学重要的组成部分，了解大气能量的时空分布和变化特征，能够为大气科学研究，尤其是气候变化研究提供新的思路和手段。本文基于1948～2016年NCEP逐月再分析资料，从大气的总能量及其内能、位能、潜热和动能的分布、变化趋势和主模态变化等方面阐释了全球大气能量变化的整体特征。主要结论如下:（1）除高海拔地区外，总能量呈现从赤道向两极逐渐递减的分布，且全球大部分地区呈增加趋势，内能和位能的分布和变化与总能量较为接近；潜热能的极大值区和显著变化区均位于赤道及低纬地区；动能的极大值区分布在中纬度长波槽和西风急流出口区，其在南半球双西风急流区的变化最为显著。（2）总能量呈现出不连续的阶段性跳跃式增长特征；北半球的总能量多于南半球，而增速却慢于南半球，即两半球间的能量呈趋同趋势；海洋上空的总能量多于陆地，且海陆间差额有增大趋势；火山爆发事件可能对大气能量在年际尺度上的减少有重要作用。（3）大气各能量第一模态的空间特征与其各自变化趋势分布非常相似，并先后在1975年左右发生了年代际突变。就第二模态而言，大气的总能量、内能和位能从整体上反映出南北极与其它地区呈反向变化的特征；部分低纬度地区的潜热能与其它地区呈反向变化；动能主要呈现从热带太平洋向南北两极的经向波列分布；它们的时间系数均有一定的多年代际变化特征，可能与气候系统的内部变率有关。     

Low-frequency climate variability of an aquaplanet

The long-term variability of an aquaplanet climate is analyzed with a coupled atmosphere–ocean–sea ice general circulation model. The main result of the 20,000 years simulation is a very dominant low-frequency oscillation with a period of approximately 700 years. All compartments of the aquaplanet (atmosphere, ocean, and sea ice) are involved as the climate alternates between warmer and colder states. Comprehensive time series analyses, as well as a comparison between mean states of cold and warm phases, give a detailed picture of the life cycle of the low-frequency oscillation. The warm phases are characterized by ice-free polar waters and a weaker meridional overturning circulation. During cold phases, the poles are completely covered by sea ice (down to 65^° N/S) and the overturning cells in the ocean are stronger. The climate state changes throughout atmosphere and ocean; however, surface areas in high latitudes are especially affected due to the changing sea ice cover. The meridional energy transport in atmosphere and ocean alternates with the climate regime, since the ocean is more efficient in transporting heat poleward when the poles are ice-free.     

Some dynamical consequences of Greenhouse gas warming

Abstract

The change in December‐February climate simulated by the CCC GCM for a doubling of CO₂ is viewed from a Northern Hemisphere middle‐latitude persepctive. The simulated change in temperature is such as to reduce equator‐to‐pole and ocean‐to‐land temperature gradients in the body of the troposphere and this is expected to result in less baroclinicity and baroclinic instability, weaker eddies and transports and generally to a decrease in synoptic activity or, in other words, to more “summer‐like” conditions.

The overall “rate of working” of the atmosphere, as measured by the generation of available potential energy, its conversion to kinetic energy and subsequent dissipation, decreases by some 12%. However, while the amount of available potential energy in the atmosphere decreases by about the same amount, the amount of kinetic energy is unchanged. Differences to the mean zonal, standing and transient eddy components of available potential and kinetic energies and to their rates of generation and conversion show that the energy cycle has changed in ways that might not be immediately expected.

Despite the general decrease in activity, the net poleward transport of energy by the atmosphere is remarkably unchanged. This is accomplished with the expected decrease in the transport of dry static energy being off‐set by an increase in latent energy transport. This is true both for mean zonal and eddy transports. That the same amount of energy is transported by a generally less active atmosphere shows that, in a sense, the flow structures are more “efficient” in the warmer climate and calculations are made to quantify this. The transport of energy in latent form is much more efficient due to the strong increase in moisture content that accompanies the temperature increase.     

Effects of the seasonal variation on forming the steady state of an atmosphere-ocean coupled system

 A three-dimensional, coupled atmosphere-ocean general circulation model is developed and effects of the seasonal variation on forming a steady-state coupled atmosphere-ocean system are studied. Case studies are carried out for a basin of idealized geometry by changing the period of the seasonal variation in the solar forcing. The coupled system shows significant differences depending on the existence of the seasonal variation, where the heat transport by the oceanic circulation plays a central role. For the regular seasonal variation, a stronger oceanic meridional circulation, which accompanies larger poleward heat transport, is realized compared with that for the annual-mean solar forcing. The stronger meridional circulation is associated with a larger wintertime meridional gradient of the sea surface temperature. The meridional gradient of the annual-mean sea surface temperature is smaller for the regular seasonal variation, which results in a smaller atmospheric poleward heat transport. In consequence, the total of the atmospheric and the oceanic poleward heat transport is almost identical for the two cases. Cases with the seasonal variation of the doubled period and with the time-filtered flux exchange between the atmosphere and the ocean are also studied, showing that the system is not sensitive to those factors.     

Changes in storm tracks and energy transports in a warmer climate simulated by the GFDL CM2.1 model

Storm tracks play a major role in regulating the precipitation and hydrological cycle in midlatitudes. The changes in the location and amplitude of the storm tracks in response to global warming will have significant impacts on the poleward transport of heat, momentum and moisture and on the hydrological cycle. Recent studies have indicated a poleward shift of the storm tracks and the midlatitude precipitation zone in the warming world that will lead to subtropical drying and higher latitude moistening. This study agrees with this key feature for not only the annual mean but also different seasons and for the zonal mean as well as horizontal structures based on the analysis of Geophysical Fluid Dynamics Laboratory (GFDL) CM2.1 model simulations. Further analyses show that the meridional sensible and latent heat fluxes associated with the storm tracks shift poleward and intensify in both boreal summer and winter in the late twenty-first century (years 2081?C2100) relative to the latter half of the twentieth century (years 1961?C2000). The maximum dry Eady growth rate is examined to determine the effect of global warming on the time mean state and associated available potential energy for transient growth. The trend in maximum Eady growth rate is generally consistent with the poleward shift and intensification of the storm tracks in the middle latitudes of both hemispheres in both seasons. However, in the lower troposphere in northern winter, increased meridional eddy transfer within the storm tracks is more associated with increased eddy velocity, stronger correlation between eddy velocity and eddy moist static energy, and longer eddy length scale. The changing characteristics of baroclinic instability are, therefore, needed to explain the storm track response as climate warms. Diagnosis of the latitude-by-latitude energy budget for the current and future climate demonstrates how the coupling between radiative and surface heat fluxes and eddy heat and moisture transport influences the midlatitude storm track response to global warming. Through radiative forcing by increased atmospheric carbon dioxide and water vapor, more energy is gained within the tropics and subtropics, while in the middle and high latitudes energy is reduced through increased outgoing terrestrial radiation in the Northern Hemisphere and increased ocean heat uptake in the Southern Hemisphere. This enhanced energy imbalance in the future climate requires larger atmospheric energy transports in the midlatitudes which are partially accomplished by intensified storm tracks. Finally a sequence of cause and effect for the storm track response in the warming world is proposed that combines energy budget constraints with baroclinic instability theory.     

Global ocean circulation and equator-pole heat transport as a function of ocean GCM resolution

To determine whether resolution of smaller scales is necessary to simulate large-scale ocean climate correctly, I examine results from a global ocean GCM run with different horizontal grid spacings. The horizontal grid spacings span a range from coarse resolutions traditionally used in climate modeling to nearly the highest resolution attained with today's computers. The experiments include four cases employing 4°, 2°, 1° and 1/2° spacing in latitude and longitude, which were run with minimal differences among them, i.e., in a controlled experiment. Two additional cases, 1/2° spacing with a more scale-selective sub-gridscale mixing of heat and momentum, and approximate 1/2° spacing, are also included. The 1/2° run resolves most of the observed mesoscale eddy energy in the ocean. Artificial constraints on the model tend to minimize differences among the different resolution cases. Nevertheless, the simulations show significant changes as resolution increases. These changes generally but not always bring the model into better agreement with observations. Differences are typically more noticeable when comparing the 4° and 2° runs than when comparing the 2° and 1° runs or the 1° and 1/2° runs. A reasonable conclusion to draw for current studies with coupled ocean-atmosphere GCMs is that the ocean grid spacing could be set to about 1° to accrue the benefits of enhanced resolution without paying an excessively steep price in computer-time cost. The model's poleward heat transport at 1/2° grid spacing peaks at about 1 × 10¹⁵ W in the Northern Hemisphere and 0.5 × 10¹⁵ W in the Southern Hemisphere. These values are significantly below observations, a problem typical of ocean GCMs even when they are less constrained than in the present study. This present problem is alleviated somewhat in the 1/2° run. In this case, however, the eddies resolved by the model generally act to counter rather than to reinforce the heat transport of the mean flow. Improved heat transport may result less from enhanced resolution than from other changes made in this version of the model, such as more accurate wind forcing.     

The effect of sea-ice on the transient atmospheric eddies of the Southern Hemisphere

 Two 10 y simulations with a full seasonal cycle and 96×72×19 resolution were carried out with a version of the LMD GCM to diagnose the role of sea-ice on the extratropical climatology of the Southern Hemisphere. The control integration used the usual observed sea-ice distribution, while the anomaly simulation imposed a scenario in which all sea-ice was entirely replaced by open ocean. The simulated control climate was compared with available observational-based analyses. Relevant diagnostics of the time mean and indicators of the transient eddy activity have been evaluated for both integrations. The impact was shown throughout the troposphere and was larger and more organised in winter. We found reduced westerly flow and both falls and rises in sea level pressure in the region from which sea-ice was removed. The removal of ice in the Southern Ocean affects the baroclinic structure of the atmosphere. Changes in baroclinicity and eddy activity are consistent with changes in the mean climate. In general, the meridional wind variance, the poleward transient temperature flux and the eddy flux convergence of westerly momentum were weaker over the Southern Ocean. However, a strengthening of the variance downstream of the subtropical jet was found. The position of the main storm track tends to be slightly displaced equatorward in the anomaly case. Received: 24 February 1998 / Accepted: 13 March 1999     

The Role of Ocean Dynamics in the Cross-equatorial Energy Transport under a Thermal Forcing in the Southern Ocean

Under external heating forcing in the Southern Ocean, climate models project anomalous northward atmosphere heat transport (AHT) across the equator, accompanied by a southward shift of the intertropical convergence zone (ITCZ). Comparison between a fully coupled and a slab ocean model shows that the inclusion of active ocean dynamics tends to partition the cross-equatorial energy transport and significantly reduce the ITCZ shift response by a factor of 10, a finding which supports previous studies. To understand how ocean dynamics damps the ITCZ's response to an imposed thermal heating in the Southern Ocean, we examine the ocean heat transport (OHT) and ocean circulation responses in a set of fully coupled experiments. Results show that both the Indo-Pacific and the Atlantic contribute to transport energy across the equator mainly through its Eulerian-mean component. However, different from previous studies that linked the changes in OHT to the changes in the wind-driven subtropical cells or the Atlantic meridional overturning circulation (AMOC), our results show that the cross-equatorial OHT anomaly is due to a broad clockwise overturning circulation anomaly below the subtropical cells (approximately bounded by the 5℃ to 20℃ isotherms and 50°S to 10°N). Further elimination of the wind-driven component, conducted by prescribing the climatological wind stress in the Southern Ocean heat perturbation experiments, leads to little change in OHT, suggesting that the OHT response is predominantly thermohaline-driven by air-sea thermal interactions.     

大气对南极冰异常的遥响应及其季节内振荡

运用ＩＡＰＡＧＣＭ模式证实了大气对南极冰异常的强迫遥响应是激发产生全球大气季节内振荡的重要机制,进而着重考察了候平均偏差结果的时间序列,并且通过带通滤波处理,特别分析了响应场中３０～６０ｄ低频振荡的特征及其活动。通过分析发现：大气对南极冰减退的响应是一种具有３０～６０ｄ周期的低频遥响应,并呈现出清楚的二维Ｒｏｓｓｂｙ波列特征;强迫场中的３０～６０ｄ季节内振荡具有着同实际大气中的低频振荡相类似的垂直结构和传播特征。大气响应场中３０～６０ｄ振荡能量在垂直方向上随高度的增加而增加,在纬向上表现出明显的区域性特征,即季节内振荡的最大动能区（由于ＣＩＳＫ机制）分布在大洋内;ＥＵＰ,ＰＮＡ,ＡＳＡ和ＲＳＡ波列可能是全球大气低频扰动传播的主要路径,３０～６０ｄ低频扰动在波列路径上的传播具有很大的一致性和系统性,从而使中高纬和热带地区、以及南北半球的３０～６０ｄ大气振荡相互联系起来,而且可以认为,赤道中太平洋和赤道中大西洋地区是南北半球３０～６０ｄ低频振荡间相互作用和相互联系的重要通道。     

OBSERVATIONAL STUDY OF MERIDIONAL VARIATION OF UV-B RADIATION DURING VOYAGES TO THE ARCTIC AND ANTARCTIC REGIONS*

Based on 1999-2000 observations made by the first Arctic and sixteenth Antactic scientific voyages,a study is undertaken about the meridional surface UV-B (B band ultraviolet rays) variations in 75°N-70°S.It is mitigated as a function of latitudes and marked by lower radiation averaged over the Northern Hemisphere (NH) than over the Southern Hemisphere (SH),with its daily course basically similar to that of total radiation.Around polar summer noon hours (localtime) and where ice albedo is maximum,the strongest UV-B irradiance on the surface perpendicular to sun's beams as found at equatorial latitudes is measured sometimes.In the areas near Zhongshan Station the increase of surface UV-B radiation shows a close relation to the decrease of ozone in the higher atmosphere but it has a less intimate relation with its concentration at ground.     

On the climate response to zero ozone

Although ozone appears in the Earth’s atmosphere in a small abundance, it plays a key role in the energy balance of the planet through its involvement in radiative processes. Its absorption of solar radiation leads to the temperature increase with height defining the tropopause and the stratosphere. Moreover, excluding water vapor, O₃ is the third most important contributor (after CO₂ and CH₄) to the greenhouse radiative forcing. Thus, the total removal of O₃ content in an Earth-like atmosphere may cause interesting response of the climate system that deserves further investigation. The present paper addresses this issue by means of a global climate model where the atmosphere is coupled with a passive ocean of a given depth. The model, after reaching the statistical equilibrium under present climate conditions, is perturbed by a sudden switch off of the O₃ content. Results obtained for the new equilibrium suggest that the model gets in a colder state mainly because of the water vapor content decrease. Most of the cooling occurs in the Southern Hemisphere while in the Northern Hemisphere the ice cap melts quite consistently. This process appears to be governed by the northward cross-equatorial heat transports induced by changes in the general circulation.     

The role of the individual air-sea flux components in CO2-induced changes of the ocean's circulation and climate

 In this study we investigate the role of heat, freshwater and momentum fluxes in changing the oceanic climate and thermohaline circulation as a consequence of increasing atmospheric CO₂ concentration. Two baseline integrations with a fully coupled ocean atmosphere general circulation model with either fixed or increasing atmospheric CO₂ concentrations have been performed. In a set of sensitivity experiments either freshwater (precipitation, evaporation and runoff from the continents) and/or momentum fluxes were no longer simulated, but prescribed according to one of the fully coupled baseline experiments. This approach gives a direct estimate of the contribution from the individual flux components. The direct effect of surface warming and the associated feedbacks in ocean circulation are the dominant processes in weakening the Atlantic thermohaline circulation in our model. The relative contribution of momentum and freshwater fluxes to the total response turned out to be less than 25%, each. Changes in atmospheric water vapour transport lead to enhanced freshwater input into middle and high latitudes, which weakens the overturning. A stronger export of freshwater from the Atlantic drainage basin to the Indian and Pacific ocean, on the other hand, intensifies the Atlantic overturning circulation. In total the modified freshwater fluxes slightly weaken the Atlantic thermohaline circulation. The contribution of the modified momentum fluxes has a similar magnitude, but enhances the formation of North Atlantic deep water. Salinity anomalies in the Atlantic as a consequence of greenhouse warming stem in almost equal parts from changes in net freshwater fluxes and from changes in ocean circulation caused by the surface warming due to atmospheric heat fluxes. Important effects of the momentum fluxes are a poleward shift of the front between Northern Hemisphere subtropical and subpolar gyres and a southward shift in the position of the Antarctic circumpolar current, with a clear signal in sea level. Received: 3 May 1999 / Accepted: 11 December 1999     

The global heat balance: heat transports in the atmosphere and ocean

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.