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1.
Long-term observations for monitoring of the cryosphere 总被引：1，自引：0，他引：1
John E. Walsh 《Climatic change》1995,31(2-4):369-394
Variations of the cryosphere over decadal-to-century timescales are assessed by a survey of data on sea ice, snow cover, glaciers and ice sheets, permafrost and lake ice. The recent variations are generally consistent across the different cryospheric variables, especially when placed into the context of variations of temperature and precipitation. The recent warming over northern land areas has been accompanied by a decrease of snow cover, particularly during spring; the retreat of mountain glaciers is, in an aggregate sense, compatible with the observed warming; permafrost extent and lake ice duration show similar variations in areas for which data are available. Corresponding trends are not apparent, however, in data for some regions such as eastern Canada, nor in hemispheric sea ice data, especially for winter. The data also suggest an increase of snowfall over high latitudes, including the Antarctic ice sheet.Estimates of both the climatic and the statistical significance of the recent variations are hampered by data inhomogeneities, the shortness of the records of many variables and the absence of central archives for data on several variables. The potential of monitoring by satellite remote sensing has been realized with several variables (extent of sea ice, snow cover). Other cryospheric variables (snow depth, ice sheet elevation, lake ice, mountain glaciers) may be amenable to routine monitoring by satellites pending advances in instrumentation, modifications of satellite orbit, and further developments in signal detection algorithms. The survey of recent variations leads to recommendations concerning the use of historical data,in situ measurements, and remote sensing applications in the monitoring of the cryosphere. 相似文献
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国家气候中心气候系统模式BCC_CSM2.0最新耦合了美国Los Alamos国家实验室发展的海冰模式CICE5.0,为试验模式中与反照率相关参数的敏感性及其对模拟结果的影响,提高模式对北极海冰的模拟能力,选取海冰模式中3个主要参数进行了敏感性试验。利用以BCC_CSM2.0耦合框架为基础建立的海冰-海洋耦合模式,选取CORE资料为大气强迫场开展试验,试验的3个参数分别为冰/雪表面反射率、雪粒半径和雪粒半径参考温度。结果表明,参数取值的不同对北极海冰的模拟有显著的影响,优化后的取值组合极大提高了模式的模拟能力,主要表现在:（1）改善了对北极冬季海冰厚度的模拟,海冰厚度增大,与观测资料更为吻合;（2）显著提高了对北极夏季海冰密集度的模拟能力,从而模拟的北极海冰范围年际循环与观测更为一致。参数取值的优化改进了模式对海冰反照率的模拟,进而影响了冰面短波辐射的吸收和海冰表层的融化,最终提高了模式对海冰密集度和厚度的模拟效果。 相似文献
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Abstract Two sets of Synthetic Aperture Radar (SAR) images were collected, as part of the Labrador Ice Margin Experiment (LIMEX), over the Newfoundland Shelf on consecutive days in April 1990. Ice movement is detected from the displacement of ice floes between the two images sets and compared with ice drift data from six satellite‐tracked beacons and in situ CTD data. The ice velocity data derived from the SAR images and the beacons are used to generate a map of ice velocity vectors. A streamfunction map of ocean currents is produced by removing the direct wind‐driven component in the ice movement data, and by using an objective analysis method. The resulting flow pattern contains the offshore branch of the Labrador Current with a speed of 30 to 50 cm s?1. The current closely follows the shelf break topography from north to south through the study area (47–50.5°N) as a continuous flow. In comparison, if the wind effect was not removed from the ice velocity data, the calculated Labrador Current north of 50°N would stray from the shelf break. The position of the current axis and the current speed derived from the ice movement data are in good agreement with the geostrophic current computed from the CTD data. 相似文献
6.
Thomas T. Wilheit Jr. 《Boundary-Layer Meteorology》1978,13(1-4):277-293
The thermal microwave radiation from the ocean surface as seen from space is a function of the surface temperature and wind speed and is modified by liquid water and water vapor in the intervening atmosphere. Further, if the ocean surface is frozen, the emissivity is drastically increased and the effect of the intervening atmosphere is generally negligible. The emissivity of first-year ice is somewhat larger than that of multi-year ice.The data from the Electrically Scanning Microwave Radiometers (ESMR's) on the Nimbus-5 and —6 satellites operating at wavelengths of 1.55 cm and 8 mm, respectively, can be interpreted in terms of rain rate, ice coverage and first-year versus multi-year ice determination. The rain-rate data are being used to establish a climatology of rainfall over the oceans. The ice data are being used by the United States Navy in support of international scientific efforts in the Antactic region. Both ice and rain data sets have been generated for the Global Atmospheric Research Project Data Systems Test.It is possible, by making multifrequency measurements, to separate the surface and atmospheric effects and to make useful measurements of sea surface temperature, surface wind speed, and atmospheric parameters along with improved measurements of rain and ice. 相似文献
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为了发展一套全球多源海冰密集度逐日融合资料,以欧洲气象卫星应用组织（EUMETSAT）海洋海冰应用中心（OSI SAF）海冰密集度数据、中国国家卫星气象中心（NSMC）的MWRI和VIRR全球海冰密集度数据、美国国家冰雪数据中心（NSIDC）的NISE海冰密集度数据、美国国家冰中心（NIC）的IMS北半球海冰数据为观测数据源,以ERA-Interim模式数据为背景场,采用以下方案开展融合试验。首先,对各数据源资料进行质量控制;其次,以OSI SAF海冰密集度数据为基准,采用概率密度函数（PDF）匹配方法订正其他卫星资料的系统误差;然后,根据订正后的误差生成超级观测场;最后,利用STMAS方法将超级观测场和作为背景场的ERA-Interim海冰密集度数据进行融合,生成全球逐日0.25°分辨率海冰密集度融合试验数据。通过与国际广泛使用的OISST、OSTIA海冰密集度数据对比,评估融合试验产品的质量。结果表明:融合方案中的PDF方法通过调整非基准资料的概率密度分布,实现非基准资料和基准资料概率密度分布一致,从而使3种海冰密集度卫星资料系统误差均显著减小;STMAS方法能够将超级观测场和背景场进行有效融合,生成融合试验产品;风云卫星数据的使用提高了融合数据生产的自主可控能力;同时,融合方案考虑了卫星数据源的时效性、获取的稳定性等因素。融合产品与OISST和OSTIA海冰密集度数据的空间分布在南、北极均高度吻合,相关系数均超过0.985,与OISST和OSTIA的偏差分别为?1.170%和0.276%,融合试验产品整体偏差介于两种资料之间,反映了试验产品系统误差较小的良好特性。可见,融合方案能够满足实时业务需要,融合试验产品具有较高的质量。 相似文献
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Computer recording of thermal drilling rate of ice hummocks and stamukhas gives the objective information on their internal
structure and basic morphometric characteristics. Methods of determination of the consolidation layer of ice hummocks and
stamukhas and the thermal drilling data processing technique are considered in the paper. The reliability of determination
of consolidated layer boundaries on the basis of the thermal drilling rate should be corroborated by the temperature measurements.
To estimate the time spent for the ice hummock temperature measurement using the polyethylene tubes which are put into the
boreholes and filled with the antifreeze, the experimental study of the borehole freezing rate was carried out depending on
the temperature and salinity of ice. The results of experiments corroborating the existence of convection in the antifreeze
are given. The used methods of ice hummock temperature measurement are discussed. The method of investigation of ice formations
combining the thermal drilling technique and ice temperature measurement on the borehole wall enables to obtain the accurate
data on the position of the lower boundary of consolidated layer, although it results in a smaller number of the boreholes. 相似文献
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采用NCEP/NCAR逐月再分析资料、广西北部43个气象台站的温度、湿度、风、降水、导线覆冰等观测资料以及广西输电线路覆冰资料,建立雨凇覆冰厚度计算模型,并得出气象台站的历史覆冰厚度序列。采用数理统计和合成分析等方法研究典型覆冰年份的时空特征、环流背景及气象要素变化特征,结果发现:广西输电线路覆冰主要出现在冬季的桂北,并有逐年减轻的趋势,MannKendall突变检验表明,存在1个明显的突变点,出现在1985年;广西典型覆冰年份,500 hPa欧亚大陆中高纬地区呈明显的"两槽一脊"型,广西高空处于南支槽前,地面受冷高压脊控制;赤道中东太平洋,从夏季到秋季,海温由偏高转为偏低,到冬季SSTA维持为负距平,说明广西输电线路覆冰与LA NINA事件有较密切的关系。当日最低气温在0.2℃以下,风速5 m·s-1,并伴有雨凇和弱降水,低温寡照天气时容易出现覆冰。 相似文献
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W. F. Budd 《Climatic change》1982,4(4):341-351
Summary and Conclusions The Last Great Ice Sheets provides a valuable compilation for current estimates of the extent and timing of the maximum ice
extent of the last ice age period around the globe. The areas of uncertainty are indicated and emphasis is given to points
of controversy where further research is needed to resolve the most important problems still remaining. The work thereby presents
plausible upper and lower limit estimates for the maximum extent of the ice corresponding to about 18 ka BP. These limits
can be used for the boundary conditions required for atmospheric climate modelling studies. For this type of application the
differences in the upper and lower limits are not serious and consequently the possible errors in the reconstruction estimates
are not so important.
The greatest uncertainties in the ice cover reconstructions occur for the northerly limits of the grounded ice which tend
to be in off-shore regions where reliable data is sparse. This signals the requirement for a much greater research effort
to collect off-shore sediment sequences and other data to help clarify the ice cover fluctuation record. The possibility of
an extensive arctic ice shelf system and marine ice sheet cover interconnecting with the various grounded ice sheets is put
forward as a working hypothesis along with arguments in favour of the upper limit estimates for the maximum ice extent. The
extent of the ice age ice shelves is an important question which should be examined by dynamic ice sheet modelling with explicit
ice shelf formulation. The extensive growth of the ice sheets to seaward margins leads naturally to ice shelf formation. The
major questions are: how extensive were the ice shelves, and to what extent did coalescence occur?
The further hypothesis that the ice shelves may have had a major role in the growth and decay of the ice sheets is more difficult
to support since the results of the dynamic modelling indicate that the ice shelves form readily as a result of extensive
growth of the ice sheets but it is difficult to start extensive ice growth near sea level.
The information presented for the timing of the advance towards the maximum ice cover and the subsequent pattern of retreat
provides further valuable material to test the dynamic ice sheet and climate models including the reactions to the Earth's
orbital radiation changes. These results for the rates of change of the ice cover taken together with the modelling results
of Budd and Smith indicate that neither the ice sheets nor the bedrock depression had time to reach equilibrium states.
The non-equilibrium nature of the ice sheets with only short periods between relatively rapid advance and retreat phases is
an important factor that needs to be taken into account in assessing the reconstructions of the ice sheets. This emphasises
the need for further work with dynamic ice sheet models and coupled global atmosphere ocean models to determine more clearly
the sequence of changes during the growth and decay of the large ice sheets. ‘The Last Great Ice Sheets’ provides a timely
data base and compilation to support these studies. 相似文献
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Tsoi-Ching Yip 《Atmospheric Research》1995,36(3-4)
The Chaine and Skeates icing model is a semi-empirical model. It is based on the formulations proposed by McKay and Thompson (1969). Horizontal ice accretion thickness is assumed to be the observed precipitation amount adjusted by the appropriate ice density. Clear ice density is assumed to be 900 kg/m3. Vertical ice accretion thickness is proportional to precipitation rate and wind speed. Ice accretion occurs only at temperatures near or below freezing. All impinging water is assumed to turn into ice. The freezing fraction is assumed to be one. Horizontal and vertical ice thicknesses are changed into equivalent radial thickness (Chaine and Castonguay, 1974). All parameters used in this model can be derived from routinely observed meteorological data. Icing amounts estimated by this model are very sensitive to wind speed and precipitation rate. Model simulated 30-year return period equivalent radial ice amounts for 20 Quebec locations are compared with collocated Passive Ice Meter data and the results are found to be reasonable. The variation of ice amount with height can be estimated by a log function proportional to 10 m icing amounts, except in British Columbia. Also the 30-year return period equivalent radial ice estimates due to freezing precipitations for 303 locations in Canada are calculated and an Ice Map is plotted. In the future, more work needs to be done to estimate ice amounts due to other forms of icing such as in-cloud rime icing and wet snow. These quantities should be added to the current amounts to make the ice map complete. Anecdotal ice information should be collected to validate the map. 相似文献
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Mikhail Ya Verbitsky 《Climate Dynamics》1992,7(2):105-110
A set of simple scaling formulas related to ice sheet evolution is derived from the dynamic and thermodynamic equations for ice and is used to consider two common situations: (a) when we wish to estimate potential ice sheet characteristics given the prescribed net snow accumulation over an area; and (b) when we wish to reconstruct net snow accumulation and vertical temperature difference within the ice sheet given empirical data only concerning ice sheet area and volume. The scaling formulas are applied to the present day Antarctic and Greenland ice sheets, as well as to some ancient ice sheets, and are used to estimate the potential global sea level change due to greenhouse warming. 相似文献
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ANTARCTIC SEA ICE AND THE POLAR VORTEX INDEX:TEMPORAL AND SPATIAL CHARACTERISTICS AND THEIR RELATIONSHIP* 
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下载免费PDF全文 The cluster analysis method has been used to divide the Antarctic sea ice variation field into 5 sectors.Then,for each of these sectors,the corresponding indexes of vortex area and vortex intensity on the 500 hPa level have been calculated.These data were used to analyse the temporal and spatial characteristics of both Antarctic sea ice and the vortex index variations and their relationship.Our results show that substantial differences are presented in the climatic pattern and interannual variations of the sea ice data and vortex index in different sectors.The maximum sea ice extent variations appear in sector 1 and sector 4.Oscillation periods of 2-2.5 and 5-7 years exist in the variations of sea ice extent and vortex index in most sectors.A positive trend is only found in sector 1 sea ice extent while the other sectors shown egative trends.The average extent of the Antarctic sea ice as a whole has retreated at a rate of 1.6 latitudes per 100 years.The vortex areas for all sectors have decreased.Nevertheless,the vortex intensities in 3 sectors have increased.The relationship between sea ice and vortex characters in each sector is obvious,but a little complex.Sectors 1 and 5,which are located in the Southeast Pacific and South Atlantic,are the most sensitive areas in terms of sea ice/atmosphere interaction. 相似文献
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This paper analyzes the influence of flaw polynyas of the seas of the Siberian shelf on the formation of ice conditions in summer based on the ten-day data on the areas of flaw polynyas for 1978–2002 obtained by satellite image processing. The results of forecasts of summer ice conditions in the seas of the Siberian shelf are presented. The correspondence between the forecasts and observed data is 94.7% on average. The interrelation of atmospheric and ice processes is shown for the case when winter atmospheric processes determine ice conditions for the following summer and fall. 相似文献
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R.G. Barry 《大气与海洋》2013,51(4):771-807
Abstract The current status and history of observing systems for snow cover, sea and freshwater ice, glaciers, ice caps, ground ice and permafrost in Canada are reviewed as part of a contribution to the WMO's Global Climate Observing System program. The data requirements that have been identified by previous discussion groups for different research, change detection and monitoring purposes are summarized. Problem areas in data collection and processing, as well as gaps in the observing/data systems, are illustrated and the status of cryospheric data archives relating to Canada, and data distribution, are discussed. The present status is considered to be unsatisfactory in a number of respects for the different cryospheric variables important for global change research. 相似文献
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Ice concentration data from passive microwave sensors are not reliable during the summer melt season. In this study passive microwave ice concentration estimates are improved upon through the assimilation of ice surface temperature data from the Moderate-Resolution Imaging Spectroradiometer (MODIS). Ice concentration from the analysis is converted to ice extent and compared with data from the Interactive Multisensor Snow and Ice Mapping System (IMS). Ice concentration analysis from data assimilation is in better agreement with the IMS data than the original passive microwave data, with the largest improvements occurring during sea-ice melt. 相似文献
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Abstract A coupled ice‐ocean dynamical model is applied to the simulation of sea‐ice motion and distribution off Newfoundland during the Labrador Ice Margin Experiment (LIMEX), March 1987. In the model, the ice is coupled to a barotropic ocean through an Ekman layer that deepens with increasing wind speed. A 6‐hourly gridded wind dataset was used as input to drive the ice and the ocean. The results show that ice velocities with ice‐ocean coupling are appreciably higher than those without coupling because of the generation of wind‐driven coastal currents. This suggests that coupled ice‐ocean dynamics should always be considered in short‐term sea‐ice models. The model gives reasonable agreement with the observed ice edge except in the southern boundary where ice‐melt has a strong influence on the ice‐edge position. Ocean currents, sea level and ice velocities computed from the model are in qualitative agreement with limited current‐meter, tide‐gauge, and ice drifter trajectory data. 相似文献
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Abstract Snow‐plus‐ice thickness and surface‐ice roughness data collected by a helicopter‐towed sensor package was used to identify surface‐ice properties in March 1992 AVHRR and SAR images for the land‐fast and mobile pack ice off the northern coast of Newfoundland. The sensor package consisted of an electromagnetic induction sensor and laser profilometer. Observed snow depths and ice thicknesses verified that snow‐plus‐ice thickness over undeformed ice can be obtained to an accuracy of ±10 cm. Snow‐plus‐ice thickness and surface roughness data for flight sections covering several hundred kilometres indicated the change in pack ice properties seen in images from thin, smooth coastal ice and open water conditions to thick, rough consolidated offshore pack ice. Ice charts covering the same area showed similar variations in ice conditions based on AVHRR and fixed‐wing reconnaissance data. In the ERS‐1 SAR image, low backscattering coefficients were associated with large, smooth coastal floes interspersed with areas of high backscatter indicating the presence of waves in open water areas. Backscattering coefficients were higher in the rubble areas near the inshore edge of the pack ice than in the interior of the pack ice itself. Distinguishing ice types on the basis of tone alone in SAR imagery was found to be problematic; however in combination with other remotely sensed data such as AVHRR data, SAR data will become more useful in distinguishing ice types. 相似文献
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南北极海冰的时空变化特征 总被引：5，自引：0，他引：5
本文分析了南北极海冰多年平均覆盖资料，给出南北极海冰的年内变化特征，极地海冰最多最少月份的空间分布。计算了２月及９月海冰年际变化方差分布，并对２月及９月南北极海冰７个分区域覆盖面积作了ＥＯＦ分解，为进行南北极海冰影响全球气候的数值试验提供了海冰变化的空间配置 相似文献