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1.
To assess the performances of state-of-the-art global climate models on simulating the Arctic clouds and surface radiation balance, the 2001–2014 Arctic Basin surface radiation budget, clouds, and the cloud radiative effects(CREs) in 22 coupled model intercomparison project 6(CMIP6) models are evaluated against satellite observations. For the results from CMIP6 multi-model mean, cloud fraction(CF) peaks in autumn and is lowest in winter and spring, consistent with that from three satellite observation products(Cloud Sat-CALIPSO, CERESMODIS, and APP-x). Simulated CF also shows consistent spatial patterns with those in observations. However,almost all models overestimate the CF amount throughout the year when compared to CERES-MODIS and APP-x.On average, clouds warm the surface of the Arctic Basin mainly via the longwave(LW) radiation cloud warming effect in winter. Simulated surface energy loss of LW is less than that in CERES-EBAF observation, while the net surface shortwave(SW) flux is underestimated. The biases may result from the stronger cloud LW warming effect and SW cooling effect from the overestimated CF by the models. These two biases compensate each other,yielding similar net surface radiation flux between model output(3.0 W/m~2) and CERES-EBAF observation(6.1 W/m~2). During 2001–2014, significant increasing trend of spring CF is found in the multi-model mean,consistent with previous studies based on surface and satellite observations. Although most of the 22 CMIP6 models show common seasonal cycles of CF and liquid water path/ice water path(LWP/IWP), large inter-model spreads exist in the amounts of CF and LWP/IWP throughout the year, indicating the influences of different cloud parameterization schemes used in different models. Cloud Feedback Model Intercomparison Project(CFMIP)observation simulator package(COSP) is a great tool to accurately assess the performance of climate models on simulating clouds. More intuitive and credible evaluation results can be obtained based on the COSP model output. In the future, with the release of more COSP output of CMIP6 models, it is expected that those inter-model spreads and the model-observation biases can be substantially reduced. Longer term active satellite observations are also necessary to evaluate models' cloud simulations and to further explore the role of clouds in the rapid Arctic climate changes.  相似文献   

2.
气候反馈通常是利用与全球平均表面温度升高相关的辐射效应变化来评估的。但是反馈的不确定性不仅仅是全球平均表面温度升高的函数。全球气候模式的预测表明，海表面温度变化的地域不同，给区域尺度上的大气环流和降水响应带来了重大不确定性。在本文中我们证明了表面增暖的空间格局是造成水汽-直减率综合反馈的不确定性的主要因素。基于运用辐射核理论计算的31个气候模型中，气温和相对湿度变化的全球平均辐射效应证明了这一观点。我们的结果突出了区域气候变化对气候反馈不确定性的重要贡献，并确定了世界上限制表面增暖形态对提高气候预测能力最有效的区域。  相似文献   

3.
基于第五次国际间耦合模式比较计划(The phase 5 of the Coupled Model Intercomparison Project,CMIP5)中在4.5 W/m^2的典型浓度路径(Representative Concentration Pathway,RCP4.5)试验结果,本文通过能量框架分析方法研究了全球变暖不同阶段热带辐合带(Intertropical Convergence Zone,ITCZ)的南北移动及其主要机制,发现在温室气体持续增加的海洋快响应和温室气体达到稳定后的海洋慢响应两个阶段,ITCZ的移动都和跨赤道的大气能量输送(Atmosphere Heat Transport,AHT)变化显著相关,但两者变化的原因在两个阶段中是不同的。在快响应阶段,ITCZ位置的移动以及跨赤道AHT受大气层顶(Top of the Atmosphere,TOA)的能量变化驱动,主要与南大洋云短波辐射响应、北半球中高纬度云和地表的短波辐射响应有关,气溶胶减少引起的辐射响应变化使得ITCZ在大多数模式中表现出向北移动的特征。在慢响应下辐射强迫保持稳定,ITCZ在大多数模式中表现出向南移动的特征。这一时期ITCZ的移动由大气表面能量通量变化驱动,主要与潜热通量变化的南北半球差异有关。全球变暖不同阶段ITCZ移动与大气能量输送变化的关系差异反映了海洋对于气候变化的重要调控作用。  相似文献   

4.
The means, variances, and three-dimensional spatial covariances of the ocean temperature and salinity anomalies in the upper 1400 m layer have been estimated using data of the Argo profiling floats from 2005 to 2007. The results of data processing suggest the continuation of general warming of the ocean waters noted in a number of papers based on earlier data. A pronounced geographical and vertical nonuniformity characterizes this warming but, as a whole, it is mostly distinct in the upper 100 m layer both in the tropics and midlatitudes. For the first time, the unique characteristics of the Argo observing system allowed us to obtain previously unfeasible estimates of the spatial statistics for salinity field. In particular, it has been demonstrated that the spatial structure of salinity anomalies is similar to those of temperature, excluding the case of the near-surface layer.  相似文献   

5.
The problem of stationary vertical distribution of saturated moist air thermodynamic parameters that takes place, for example, in an eyewall cloud of a tropical cyclone is considered. Based on these distributions, the cloud-growth dynamics problem is also considered. The heat and moisture fluxes from the ocean surface are determined by the wind and temperature difference and subcloud layer condition and last after the beginning of cloud formation. They change the condition of both the cloud and the subcloud layer. The coexistence and interaction of the two different regions require additional conditions. We assume continuity of the temperature and humidity profiles at the lower cloud boundary. The problem of cloud formation over the warmer ocean with account for water-phase transformations is considered in the present study. The cloud boundaries (the upper and the lower) in the process are determined and the temperature and moisture profiles within the cloud are also investigated. The lower boundary dipping is determined while taking the subcloud moisture into account. An approximate analytical model of these processes is formulated, and the corresponding equations are solved numerically. Approximate equations govern the vertical cloud structure well.  相似文献   

6.
Assimilation systems absorb both satellite measurements and Argo observations. This assimilation is essential to diagnose and evaluate the contribution from each type of data to the reconstructed analysis, allowing for better configuration of assimilation parameters. To achieve this, two comparative reconstruction schemes were designed under the optimal interpolation framework. Using a static scheme, an in situ-only field of ocean temperature was derived by correcting climatology with only Argo ...  相似文献   

7.
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8.
Evaporation and vertical moisture and heat transfer from the underlying surface are the basis of cloud formation. The situation when the coming relatively cold stably stratified air moves over a warm ocean is a typical problem in the development of a turbulent convective layer. The problem of cloud formation is also of scientific and practical interest. This paper considers the problems of the formation of a turbulent convective layer over a warmer ocean and the vertical distribution of relative humidity. The results of the theoretical model are compared with the data of observations of the development of the turbulent convective layer at low latitudes (in the Indian Ocean) and at higher latitudes (in autumn over Lake Michigan). Approximate equations describe well the dynamics of temperature and humidity of the layer as a function of the difference between the temperatures of the approaching and near-surface air layers. The theoretical results are compared with the data on measurements of the condensation heights obtained at the Novosibirsk Tolmachevo Airport. Some discrepancy between them is due to the unsteadiness measurement and the approximations adopted in the theoretical model.  相似文献   

9.
Ensemble numerical experiments with the climate model of intermediate complexity developed at the A.M. Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences (IAP RAS CM) are conducted to estimate the efficiency of controlled climate forcing (geoengineering) due to stratospheric sulfate aerosol (SSA) emissions in order to compensate for global warming under the SRES A1B anthropogenic emission scenario. Full (or even excessive) compensation for the expected anthropogenic warming in the model is possible with sufficiently intense geoengineering. For ensemble members with values of the governing parameters corresponding to those obtained for the Mt. Pinatubo eruption, global warming is reduced by no more than 0.46 K in the second half of the 21st century, with a residual rise in the global surface temperature T g comparative to 1961–1990 of 1.0–1.2 K by 2050 and 1.9–2.2 K by 2100. The largest reduction in global warming (with the other parameters of the numerical experiment being equal) is found not for a meridional distribution of SSA concentration peaked at low latitudes (despite the largest (in magnitude) global compensation instantaneous radiative forcing), but for a uniform horizontal aerosol distribution and for a distribution with the SSA concentration maximum in the middle and subpolar latitudes of the Northern Hemisphere. The efficiency of geoengineering in terms of T g in the second half of the 21st century between the most efficient and the least efficient meridional distributions of stratospheric aerosols differs by as much as one-third, depending on the values of other governing parameters. For meridional distributions of SSA concentration, which produce the largest deceleration of global warming, such a deceleration is regionally most pronounced over high- and subpolarlatitude land areas and in the Arctic. In particular, this is expressed in the smallest reduction in the sea-ice extent and permafrost area under climate warming in the model. The compensation forcing also decelerates a general increase in global annual precipitation P g during warming. The relative deceleration in precipitation increase is most pronounced in land regions outside the tropics, where a significant deficit in precipitation is currently observed. After the theoretical completion of geoengineering in the first or second decade, its temperature effect vanishes with an abrupt acceleration of global and regional surface warming. For individual members of the ensemble experiment, the global temperature change in this period is five times as large as that in the experiment without geoengineering and ten times as large regionally (in northeastern Siberia).  相似文献   

10.
基于中国第29次南极科学考察期间获取的GPS探空观测数据,分析了东南印度洋和西南太平洋经向断面大气垂直结构的基本特征、季节变化和纬向差异。不同断面的大气垂向结构差异显著,但也具有共同特征,4000 m以下低空的气温和湿度明显高于高空,而低空风速明显小于高空风速,8000 m以上高空各个观测要素的垂直变化较小,整个断面主要以西风为主,整个垂直剖面湿度异常偏高(偏低)的区域通常对应上升(下沉)气流。给出了3个观测断面的大气锋面位置和类型,P1断面的大气锋面在47°~50°S,P2和P3断面的大气锋面在52°~58°S,P1和P2的锋面属于暖锋,P3的锋面由于气旋的影响分类不明显。东南印度洋大气剖面结构具有明显的季节变化,秋季和春季相比,秋季具有风速小,气温高特征,大气锋面更加偏南。东南印度洋和西南太平洋断面的大气剖面结构差异明显,二者相比,东南印度洋具有风速大、气温高及相对湿度小的特征,但大气锋面位置相同。  相似文献   

11.
The sensitivity of the characteristics of atmospheric centers of action (ACAs) in the Northern Hemisphere to global climate changes is analyzed on the basis of models of different complexity, including the climate model of intermediate complexity of the Institute of Atmospheric Physics, Russian Academy of Sciences and the ECHAM4/OPYC3 and HadCM3 general circulation models of the atmosphere and ocean. The emphasis is on the analysis of trends of the change in ACA characteristics in winter, when the long-term global warming is most considerable. The global climate models are shown to be able to describe not only the intermediate regimes of ACAs but also their dynamics. In particular, ECHAM4/OPYC3 is capable of reproducing the statistically significant connection of the characteristics of the North Pacific centers of action with El Niño/La Niña events, revealed from observational data. With the use of the results of the global climate models, the possible changes in the characteristics of centers of action in the 21st century are estimated for an increased content of greenhouse gases in the atmosphere.  相似文献   

12.
On the basis of the radiation-cloudiness model and the available long-term satellite data, we study the correlations of the greenhouse effect with the surface temperature of air and effective cloudiness equal to the product of the cloud amount by the conditional optical density of the clouds. We deduce the relations of satellite monitoring of the behavior of the anomalies of global air temperature caused by the excess amounts of volcanic products and greenhouse gases (formed as a result combustion of the fossil fuel) in the atmosphere. Realistic estimates of the processes of cooling and warming of the currently existing climate are obtained. Under the condition of preservation of the existing linear trends in the behaviors of the short-and long-wave flows of radiation into the outer space (observed according to satellite data for the last 20 yr), the global temperature in the second part of the current century can increase by 1.6–2.0°C. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 13–28, November–December, 2006.  相似文献   

13.
The sensitivities of two climate-model versions—INMCM4 which participated in the Coupled Model Intercomparison Project, Phase 5 (CMIP5), and a new INMCM5 version with increased vertical and horizontal resolutions in its atmospheric block—to the quadrupled concentration of CO2 are studied. When the CO2 concentration is quadrupled, the equilibrium increase in surface temperature amounts to about 4.2 K for INMCM4, which is lower than that for other models that participated in the CMIP5. When the CO2 concentration increases, the cloud radiative forcing in the model decreases; in this case, one portion of this decrease occurs during the first year after the concentration of CO2 is quadrupled and the other portion almost linearly depends on the value of global warming. The results of additional numerical experiments with the model show that a rapid decrease in cloud-radiative forcing results from variations in stratification in the atmospheric surface boundary layer and associated increased cloudiness. The portion of a linear decrease in cloud-radiative forcing with increased temperature is associated with an increase in the water content of model clouds at higher temperatures. The elimination of these two mechanisms allows one to increase the model sensitivity to the quadrupled concentration of CO2 up to 5.2 K.  相似文献   

14.
Because of its vast volume and heat capacity, the ocean contains most of the memory of the earth's ocean - atmosphere coupled system. It has been suggested that the ocean may delay global warming by absorbing large amounts of heat, that it may cause ab- rupt climate change due to its disrupted thermohaline circulation, and that it may set the time-scales for various climate oscilla- tions. Although the slow pace and persistence of oceanic variations give hope to long-range prediction, there still exist large uncer- tainties in climate predictability. Presently available observations and models are generally inadequate for studying and predicting long-term climate changes. However, some short-term fluctuations such as ENSO have been well studied and shown to be highly predictable even with simplified models.  相似文献   

15.
由于分辨率不足等原因，当前大部分全球耦合气候模式对南海等海洋区域的模拟能力仍然较低。本文基于超高分辨率（Ultra high-resolution） CESM-UHR耦合模式（大气和海洋水平分辨率分别达到约25 km和约10 km）研究了南海动力海平面对全球变暖的响应。研究发现：（1） CESM-UHR能够较好地模拟出南海冬、夏季节性动力海面高度和表层环流变化；（2）在四倍二氧化碳试验下，冬季南海动力海平面变化呈现出中部低、近岸高的分布特征；夏季则呈现出西北部低、东南部高的分布特征，分别对应冬、夏表层地转流增强趋势；（3）冬、夏动力海平面变化特征与风应力旋度变化具有很好的对应关系；（4）全球变暖下南海海平面变化存在季节循环放大效应，这将增大南海极端水位灾害风险。  相似文献   

16.
The impacts of dust loaded, Saharan Air Layer (SAL) during the life cycle of African Easterly Waves (AEWs) is a many-faceted scientific problem. It entails possible radiative effects of dust aerosols, impacts of dust on cloud physics, and the cloud nuclei of condensation, advective effects, that is, intrusions of dry dusty air versus humid air into the interior of storms. This paper addresses several such AEWs of the eastern Atlantic Ocean, where we have made use of special aircraft reconnaissance data sets that include wind and humidity profiles in the vertical. Using what are called adaptive observational strategies within a mesoscale model, we show the impacts of adding such observations in the analysis and in short-range forecasts of several AEWs. We do not have the direct and indirect effects of aerosols, but we do include the advective component. Our results show that the inclusion of humidity profiling distinguishes between developing versus nondeveloping AEWs from the use of these additional data sets via the adaptive observational strategies.  相似文献   

17.
李志  孟强  薛亮 《海洋科学进展》2020,38(2):199-210
孟加拉湾与其他热带海盆不同,在季风影响下,该地区热带气旋具有双气旋季的独特结构(4—5月的春季转换期和10—11月的秋季转换期)。虽然孟加拉湾气旋频数在10—11月较多,但是4—5月超强气旋(Saffir-Simpson 4,5级)的生成率却远高于10—11月。1981—2016年,春季转换期内孟加拉湾超强气旋都与第一支北传季节内振荡(First Northward-propagating Intra-Seasonal Oscillation,FNISO)相应而生,然而并不是所有伴随FNISO发生的气旋都能发展成为超强气旋。因此本研究以气旋生成指数为基础,利用气旋最佳轨道数据以及NCEP的海气参量数据,诊断指出孟加拉湾夏季风形成的强垂直风速剪切配合低层大气旋度和气旋潜在强度抵消夏季风期间水汽对气旋生成的促进作用,造成双峰分布,而中层大气相对湿度差异双峰不对称的主因。FNISO强度的不同与深对流中心与气旋中心的相对位置的差异,使得部分气旋受季节内振荡影响更大,强深对流的超越作用导致更显著的高低层大气温差,促使气旋具有且达到更大的潜在强度。在年际尺度上大气高低层温差的不同也是引起气旋潜在强度不同的主要原因。当季节内尺度和年际尺度共同作用,使得部分气旋发展成为超强气旋。  相似文献   

18.
Climate of the last millennium: a sensitivity study   总被引：2，自引：0，他引：2  
Seventy-one sensitivity experiments have been performed using a two-dimensional sector-averaged global climate model to assess the potential impact of six different factors on the last millennium climate and in particular on the surface air temperature evolution. Both natural (i.e, solar and volcanism) and anthropogenically-induced (i.e. deforestation, additional greenhouse gases, and tropospheric aerosol burden) climate forcings have been considered.
Comparisons of climate reconstructions with model results indicate that all the investigated forcings are needed to simulate the surface air temperature evolution. Due to uncertainties in historical climate forcings and temperature reconstructions, the relative importance of a particular forcing in the explanation of the recorded temperature variance is largely function of the forcing time series used. Nevertheless, our results indicate that whatever the historical solar and volcanic reconstructions may be, these externally driven natural climate forcings are unable to give climate responses comparable in magnitude and time to the late–20th-century temperature warming while for earlier periods combination of solar and volcanic forcings can explain the Little Ice Age and the Medieval Warm Period. Only the greenhouse gas forcing allows the model to simulate an accelerated warming rate during the last three decades. The best guess simulation (largest similarity with the reconstruction) for the period starting 1850 AD requires however to include anthropogenic sulphate forcing as well as the impact of deforestation to constrain the magnitude of the greenhouse gas twentieth century warming to better fit the observation. On the contrary, prior to 1850 AD mid-latitude land clearance tends to reinforce the Little Ice age in our simulations.  相似文献   

19.
热带太平洋是影响全球气候系统的重要区域,热带太平洋海表温度(SST)的长期变化趋势模拟是国际研究领域关注的热点。基于12个参加第六期国际耦合模式比较计划(CMIP6)的模式结果,本研究对1950年至1999年间多模式模拟得到的热带太平洋SST增暖现象进行了初步评估。结果表明,不同模式对热带太平洋SST增暖的模拟能力差别较大,特别在赤道东太平洋区域,部分模式模拟得到了偏强的SST降温趋势,与实际观测中的SST增温趋势相反,多模式集合平均结果给出了中部型厄尔尼诺事件的增温趋势。通过引入SST增暖变率分析方法,本研究对多模式模拟的热带太平洋SST在过去50 a中的增暖内在变化进行了进一步评估,结果表明目前各模式对热带太平洋SST增暖变率模拟偏弱,空间分布差异较大。  相似文献   

20.
Specific features of the extreme summer heat of 2010 in the European part of Russia are analyzed against the background of global and regional climate changes taking into account antropogenic influences and natural anomalies related, in particular, to the El Niño/La Niña phenomena. The tendencies of the characteristics of the activity of blocking anticyclones (blockings) responsible for the formation of drought regimes and the increase in the fire hazard at midlatitudes are estimated in connection with climate changes.  相似文献   

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