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Climate drift is a common and serious problem in most state-of-the-art coupled atmosphere-ocean-sea ice models. We consider the nature of climate drift in such a model, and in particular address the question of whether or not climate drift is inherent to the model, or whether the drift can be averted by a suitable choice of initial conditions or coupling procedure. The synchronous approach to coupling was adopted in which the ocean, atmosphere and sea ice models were spun-up independently to equilibrium using climatological forcing fields. The models were then coupled and integrated forward in time. Several experiments were performed which were designed to assess the impact of different coupling methodologies and changes in the initial conditions of the component models on the climate drift of the system. The results of our experiments indicate that climate drift is a problem inherent to the coupled model in that systematic errors in the components lead to incompatibilities in the surface fluxes required by the component models to maintain realistic climatologies. We conclude that climate drift can be averted only if the parameterizations of certain important physical processes are improved which should have the effect of reducing or eliminating these incompatibilities. 相似文献
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Variations of sea ice temperature from CHINARE 2003 and its application on sea ice model evaluation 下载免费PDF全文
Variation of vertical profiles of sea ice temperature and adjacent atmosphere and ocean temperatures were measured by ice drifting buoys deployed in the northeast Chukchi Sea as part of the 2003 Chinese Arctic Research Expedition.The buoy observations (September 2003 to February 2005) show that the cooling of the ice began in late September,propagated down through the ice,reaching the bottom of the ice in December,and continued throughout the winter.In winter 2003/04,some obvious warmings were observed in the upper portion of the ice in response to major warmings in the overlying atmosphere associated with the periodicity of storms in the northeast Chukchi Sea.It is found that the melt season at the buoy site in 2004 was about 15% longer than normal.The buoy observed vertical ice temperature profiles were used as a diagnostic for sea ice model evaluation.The results show that the simulated ice temperature profiles have large discrepancies as compared with the observations. 相似文献
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基于ERA-Interim再分析资料,借助大气模式CAM4,分析了北半球冬季不同月份的平均大气对巴伦支海不同振幅及不同季节海冰扰动的敏感性,并考察了中高纬度典型大气模态的分布变化情况.结果表明,冬季巴伦支海海冰的减少,会导致湍流热通量异常向上、局地异常变暖及水汽含量的异常升高,且相关异常的强度和范围随着海冰减少幅度的减... 相似文献
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Sensitivity of sea ice to wind-stress and radiative forcing since 1500: a model study of the Little Ice Age and beyond 总被引:3,自引:2,他引:1
Three different reconstructed wind-stress fields which take into account variations of the North Atlantic Oscillation, one
general circulation model wind-stress field, and three radiative forcings (volcanic activity, insolation changes and greenhouse
gas changes) are used with the UVic Earth System Climate Model to simulate the surface air temperature, the sea-ice cover,
and the Atlantic meridional overturning circulation (AMOC) since 1500, a period which includes the Little Ice Age (LIA). The
simulated Northern Hemisphere surface air temperature, used for model validation, agrees well with several temperature reconstructions.
The simulated sea-ice cover in each hemisphere responds quite differently to the forcings. In the Northern Hemisphere, the
simulated sea-ice area and volume during the LIA are larger than the present-day area and volume. The wind-driven changes
in sea-ice area are about twice as large as those due to thermodynamic (i.e., radiative) forcing. For the sea-ice volume,
changes due to wind forcing and thermodynamics are of similar magnitude. Before 1850, the simulations suggest that volcanic
activity was mainly responsible for the thermodynamically produced area and volume changes, while after 1900 the slow greenhouse
gas increase was the main driver of the sea-ice changes. Changes in insolation have a small effect on the sea ice throughout
the integration period. The export of the thicker sea ice during the LIA has no significant effect on the maximum strength
of the AMOC. A more important process in altering the maximum strength of the AMOC and the sea-ice thickness is the wind-driven
northward ocean heat transport. In the Southern Hemisphere, there are no visible long-term trends in the simulated sea-ice
area or volume since 1500. The wind-driven changes are roughly four times larger than those due to radiative forcing. Prior
to 1800, all the radiative forcings could have contributed to the thermodynamically driven changes in area and volume. In
the 1800s the volcanic forcing was dominant, and during the first part of the 1900s both the insolation changes and the greenhouse
gas forcing are responsible for thermodynamically produced changes. Finally, in the latter part of the 1900s the greenhouse
gas forcing is the dominant factor in determining the sea-ice changes in the Southern Hemisphere.
相似文献
Jan SedláčekEmail: |
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2005年渤海海冰冰厚热力增长特征实验的个例研究 总被引:2,自引:0,他引:2
认识渤海海冰冰厚热力增长特征,是开发利用海冰资源的理论基础.本文通过2005年1月12日-27日在辽东湾鲅鱼圈和渤海湾黄骅海冰现场实验个例研究得出:鲅鱼圈的累积冰厚平均日增量1.33 em/d,平均冰厚日变化为3 cm;黄骅的累计冰厚平均日增量为0.54 cm/d,平均冰厚变化22.3 cm;冰厚从0 cm增长到10 cm所需的时间为鲅鱼圈5 d左右,黄骅10 d左右;冰厚日变化与日平均气温和日平均冰温与之间相关性显著,但冰厚对气温和冰温降低的反应有一定的滞后性;当环境温度持续下降时,累积冰厚与累积气温之间有显著的正相关,当环境温度上升时,累积冰厚与累积气温之间相关性逆转. 相似文献
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区域海气耦合模式对中国夏季降水的模拟 总被引:8,自引:0,他引:8
以区域气候模式RegCM3和普林斯顿海洋模式POM为基础,建立了一个区域海气耦合模式,对1963—2002年中国夏季气候进行模拟,重点分析该耦合模式对中国夏季降水的模拟性能以及降水模拟改进的可能原因。结果表明:耦合模式对中国夏季雨带分布的模拟明显优于控制试验(单独的大气模式),对长江流域以及华南降水的模拟性能改进尤为明显,同时耦合模式能够更为真实地刻画中国东部地区汛期雨带的移动。对降水的年际变化分析发现,耦合模式模拟的1963—2002年中国夏季降水年际变率与观测吻合,模拟的夏季长江流域降水与观测降水相关系数达到0.48,模拟的华南夏季降水与观测的相关系数达到0.61,而控制试验结果与观测降水的相关系数均较小。对中国东部长江流域夏季降水与近海海温的相关分析表明,用给定海温驱动的大气模式,并不能正确模拟出中国东部夏季降水与海温的关系,而耦合模式能够较好地模拟出长江流域与孟加拉湾、南海以及黑潮区海温的关系,与GISST(全球海冰和海表温度)和观测降水相关关系一致。对水汽输送通量的分析发现,控制试验模拟的水汽输送路径与NCEP/NCAR再分析资料相比差别较大,耦合模式模拟的来自海洋上的水汽输送强度和路径与NCEP/NCAR再分析资料一致,提高了耦合模式对水汽输送的模拟能力,从而改善了模式对华南以及长江流域降水的模拟。 相似文献
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On the Association between Spring Arctic Sea Ice Concentration and Chinese Summer Rainfall: A Further Study 总被引:9,自引:0,他引:9
In our previous study,a statistical linkage between the spring Arctic sea ice concentration(SIC)and the succeeding Chinese summer rainfall during the period 1968–2005 was identified.This linkage is demonstrated by the leading singular value decomposition(SVD)that accounts for 19%of the co-variance.Both spring SIC and Chinese summer rainfall exhibit a coherent interannual variability and two apparent interdecadal variations that occurred in the late 1970s and the early 1990s.The combined impacts of both spri... 相似文献
10.
Sensitivity experiments are conducted to test the influence of poorly known model parameters on the simulation of the Greenland
ice sheet by means of a three dimensional numerical model including the mechanical and thermal processes within the ice. Two
types of experiments are performed: steady-state climatic conditions and simulations over the last climatic cycle with a climatic
forcing derived from the GRIP record. The experiments show that the maximum altitude of the ice sheet depends on the ice flow
parameters (deformation and sliding law coefficients, geothermal flux) and that it is low when the ice flow is fast. On the
other hand, the maximum altitude is not sensitive to the ablation strength and consequently during the climatic cycle it is
driven by changes in accumulation rate. The ice sheet extension shows the opposite sensitivity: it is barely affected by ice
flow velocity and the ice covered area is smaller for large ablation coefficients. For colder climates, when there is no ablation,
the ice sheet extension depends on the sea level. An interesting result is that the variations with time of the altitude at
the ice divide (Summit) do not depend on the parameters we tested. The present modelled ice sheets resulting from the climatic
cycle experiments are compared with the present measured ice sheet in order to find the set of parameters that gives the best
fit between modelled and measured geometry. It seems that, compared to the parameter set most commonly used, higher ablation
rate coefficents must be used.
Received: 19 September 1995 / Accepted: 30 May 1996 相似文献
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The Barents Sea is the most productive sea in the Arctic. The main causes of phytoplankton spring blooms are studied for a decadal time period of 2003–2013 at the region of (70 °N-80 °N, 30 °E-40 °E) in Barents Sea. Due to the rapidly ice melt in the southern region (70 °N-75 °N), almost no ice left after year 2005, sea surface temperature (SST) and wind speed (WIND) are two main dominant factors influencing phytoplankton blooming in the southern region. Ice melt is another important factor of phytoplankton blooming in the northern region (75 °N–80 °N). SST and CHL had positive correlations during blooming season but negative correlations during summer time. The lower SST in spring could result in earlier blooming in the region. Higher SST and higher WIND could result in later blooming. Positive NAO after April 2013 caused higher SST in 2013. Increasing WIND would cause CHL reduced accordingly. Blooming period is from late April to late May in the southern region, and 1–2 weeks later in the northern region. During blooming season, SST was less than 4 °C and WIND was less than 10 m/s. The higher winds (over 15 m/s) in early spring would brought more nutrients from bottom to surface and cause higher blooming (near 10 mg/m3 in year 2010) after WIND is reduced to 5−8 m/s. Higher WIND (around 10 m/s) could generate longer blooming period (more than a week) during late May in the southern region. Decrease of WIND and increase of melting ice, with slightly increase of SST and decrease of mixed layer depth (MLD), are all the factors of phytoplankton blooming in late spring and early summer. 相似文献
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The effect of snow on Antarctic sea ice simulations in a coupled atmosphere-sea ice model 总被引:1,自引:0,他引:1
The effect of a snow cover on sea ice accretion and ablation is estimated based on the ‘zero-layer’ version sea ice model
of Semtner, and is examined using a coupled atmosphere-sea ice model including feedbacks and ice dynamics effects. When snow
is disregarded in the coupled model the averaged Antarctic sea ice becomes thicker. When only half of the snowfall predicted
by the atmospheric model is allowed to land on the ice surface sea ice gets thicker in most of the Weddell and Ross Seas but
thinner in East Antarctic in winter, with the average slightly thicker. When twice as much snowfall as predicted by the atmospheric
model is assumed to land on the ice surface sea ice also gets much thicker due to the large increase of snow-ice formation.
These results indicate the importance of the correct simulation of the snow cover over sea ice and snow-ice formation in the
Antarctic. Our results also illustrate the complex feedback effects of the snow cover in global climate models. In this study
we have also tested the use of a mean value of 0.16 Wm-1 K-1 instead of 0.31 for the thermal conductivity of snow in the coupled model, based on the most recent observations in the eastern
Antarctic and Bellingshausen and Amundsen Seas, and have found that the sea ice distribution changes greatly, with the ice
becoming much thinner by about 0.2 m in the Antarctic and about 0.4 m in the Arctic on average. This implies that the magnitude
of the thermal conductivity of snow is of considerable importance for the simulation of the sea ice distribution. An appropriate
value of the thermal conductivity of snow is as crucial as the depth of the snow layer and the snowfall rate in a sea ice
model. The coupled climate models require accurate values of the effective thermal conductivity of snow from observations
for validating the simulated sea ice distribution under the present climate conditions.
Received: 20 November 1997/Accepted: 27 July 1998 相似文献
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为深入了解我国不同背景地区大气冰核浓度特征,本文通过在我国不同地区进行大气冰核及气溶胶的采样观测。研究发现:观测期间,黄山光明顶的冰核浓度数值均值为2.208 L-1;南京地区的冰核浓度数值均值为7.16 L-1;泰山山顶的冰核浓度数值均值为3.455 L-1;泰山山底的冰核浓度数值均值为4.818 L-1;新疆地区无沙尘天气冰核浓度数值均值为11.27 L-1;新疆有沙尘天气冰核浓度数值均值为51.812 5 L-1。研究给出了不同背景地区的大气冰核浓度的温度谱和湿度谱的分布。同时,研究发现,冰核数浓度与粒径大于0.5μm的气溶胶粒子数浓度的相关性较高,也就是气溶胶粒子中大颗粒所占比例越高,冰核数浓度越高。此外,还建立了基于活化温度、过饱和度以及大于0.5μm气溶胶粒子数浓度的冰核参数化方案,它们可以分别适用于沙漠地表,相对清洁的背景区域和人为污染较多的城市背景。 相似文献
14.
基于第六次耦合模式比较计划(CMIP6),使用新一代全球模式BCC-CSM2-MR的历史试验和未来共享社会经济路径(SSPs)数据,依据Hadley中心的海表面温度和海冰密集度数据及NCEP/NCAR I再分析资料,评估了BCC-CSM2-MR模式对北极海冰及北极气候的模拟能力,并对未来变化进行了预估.结果表明:BCC... 相似文献
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Mechanisms of Atlantic Meridional Overturning Circulation (AMOC) Variability in a Coupled Ocean–Atmosphere GCM简 总被引:1,自引:0,他引:1
The mechanisms involved in the variability of Atlantic Meridional Overturning Circulation (AMOC) are studied using a 2000-yr control simulation of the coupled Fast Ocean-Atmosphere Model (FOAM).This study identifies a coupled mode between SST and surface heat flux in the North Atlantic at the decadal timescale,as well as a forcing mode of surface heat flux at the interannual timescale.The coupled mode is regulated by AMOC through meridional heat transport.The increase in surface heating in the North Atlantic weakens the AMOC approximately 10 yr later,and the weakened AMOC in turn decreases SST and sea surface salinity.The decreased SST results in an increase in surface heating in the North Atlantic,thus forming a positive feedback loop.Meanwhile,the weakened AMOC weakens northward heat transport and therefore lowers subsurface temperature approximately 19 yr later,which prevents the AMOC from weakening.In the forcing mode,the surface heat flux leads AMOC by approximately 4 yr. 相似文献
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A simple climate model has been developed to investigate the existence of the small ice cap instability in the Southern Hemisphere.
The model consists of four coupled components: an atmospheric energy balance model, a thermodynamic snow-sea ice model, an
oceanic mixed layer model and a terrestrial ice model. Results from a series of experiments involving different degrees of
coupling in the model show that the instability appears only in those cases when an explicit representation of the Antarctic
ice sheet is not included in the model. In order to determine which physical processes in the ice sheet model lead to a stabilization
of the system we have conducted several sensitivity experiments in each of which a given ice sheet process has been removed
from the control formulation of the model. Results from these experiments suggest that the feedback between the elevation
of the ice sheet and the snow accumulation-ice ablation balance is responsible for the disappearance of the small ice cap
instability in our simulation. In the model, the mass balance of the ice sheet depends on the air temperature at sea level
corrected for altitude and it is, therefore, a function of surface elevation. This altitude-mass balance feedback effectively
decouples the location of the ice edge from any specific sea level isotherm, thus decreasing the model sensitivity to the
albedo-temperature feedback, which is responsible for the appearance of the instability. It is also shown that the elevation-radiative
cooling feedback tends to stabilize the ice sheet, although its effect does not seem to be strong enough to remove the instability.
Another interesting result is that for those simulations which include the terrestrial ice model with elevation-dependent
surface mass balance, hysteresis is exhibited, where for a given level of external forcing, two stable solutions with different,
non-zero ice-sheet volume and area and different air and ocean temperature fields occur. However, no unstable transition between
the two solutions is ever observed. Our results suggest that the small ice cap instability mechanism could be unsuitable for
explaining the inception of glaciation in Antarctica.
Received: 14 April 1997 / Accepted: 22 October 1997 相似文献
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利用改进的Bigg型混合云室于2011年5-11月在辽宁省气象局抚顺大气成分站对近地层大气冰核浓度进行了测量。根据测量结果,分析冰核浓度日际变化和季节变化特征,讨论了风、气压、气温和湿度以及天气状况等气象要素对大气冰核浓度的影响。结果表明:观测期间,抚顺市大气冰核浓度平均为30个·L-1(-20 ℃时);冰核浓度随活化温度的降低呈指数式增加;气象因子对冰核浓度有一定的影响,不同季节影响的程度不同。 相似文献
19.
Possible impacts of Barents Sea ice on the Eurasian atmospheric circulation and the rainfall of East China in the beginning of summer 总被引:1,自引:1,他引:1
Possible influences of the Barents Sea ice anomalies on the Eurasian atmospheric circulation and the East China precipitation distribution in the late spring and early summer (May-June) are investigated by analyzing the observational data and the output of an atmospheric general circulation model (AGCM).The study indicates that the sea ice condition of the Barents Sea from May to July may be interrelated with the atmospheric circulation of June. When there is more than average sea ice in the Barents Sea, the local geopotential height of the 500-hPa level will decrease, and the same height in the Lake Baikal and Okhotsk regions will increase and decrease respectively to form a wave-chain structure over North Eurasia.This kind of anomalous height pattern is beneficial to more precipitation in the south part of East China and less in the north. 相似文献
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全球变暖的背景下,北极航线的常规通航甚至商业运营有望实现,而海雾会严重影响航道上船只的航行安全。海冰的存在使海气之间相互作用变得更为复杂,是研究北极海雾不可忽略的因素。船载观测发现,与中纬度常见平流冷却雾形成时气温下降速度往往超过海水降温速度不同,北极海雾发生时海冰的存在还会使海水降温速度超过空气降温速度。然而目前海冰分布是否会影响模式模拟海雾的准确性还不得而知,因此本文利用Polar WRF(Polar Weather Research and Forecasting)模式模拟了中国第七次北极考察中观测到的一次海雾过程,并进行海冰密集度敏感性试验。通过与船载观测和欧洲中期天气预报中心再分析数据比对发现,在低浮冰区内(海冰密集度小于50%)考虑海冰分布时可以更加准确地刻画潜热通量与水汽通量,模拟出与观测事实相符的表层空气降温与增湿过程以及相对湿度的变化,因此能够更好地刻画海雾的三维结构及其生消演变。 相似文献