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1.
海冰上积雪的分布是影响海冰与大气能量交换以及气候变化的重要因素。当前的CMIP6气候模式（如CESM2和NESM3）采用定常的积雪密度,而专注于模拟雪厚度和密度变化的模式（如SnowModel-LG）则采用经验的变化雪密度公式。对比CryoSat-2卫星观测的积雪厚度发现,从积雪厚度的空间分布与平均值难以判断出变化雪密度对北冰洋积雪厚度模拟产生何种影响,对于变化雪密度模拟积雪厚度的改进及机制有待进一步研究。本文采用随气温、风速等因子变化的雪密度经验公式模型,并利用SNOTEL单站的长时间序列观测资料,对不同影响因子设计如下敏感性实验:A. 考虑所有气象因子的变化雪密度模型;B. 常数雪密度模型;C. 在A中不考虑风对密实化的影响;D. 在A中不考虑气温对密实化的影响。实验A、B、C和D诊断计算的2018年11月1日至2019年5月10日积雪厚度的均方根误差分别为4.2 cm、4.8 cm、25.9 cm和4.2 cm。结果表明,变化雪密度方案A模拟的积雪密度、厚度在平均值上与常数雪密度的结果接近,但其模拟的积雪厚度均方根误差最小,并且能够模拟出积雪厚度在几天到十几天时间尺度上的高频变化,同时减小了这种高频变化对应时段雪厚模拟结果的相对误差,二者具有一定的相关性。此外,还发现气温变化对积雪密实化的影响远小于风。 相似文献
2.
积雪密度演变对北极积雪深度模拟的影响 总被引：1，自引：1，他引：0
积雪具有复杂的时空分布,在高纬度地区的气?冰?海耦合系统中扮演了重要的角色。准确的积雪质量平衡计算可以帮助我们更好地理解海冰演变过程以及极区冰雪与大气之间的相互作用。雪密度是影响积雪质量平衡众多因素中的重要因子。现有的一维高分辨率冰雪热力学模型（如HIGHTSI）中,使用常数块体雪密度均值将降雪雪水当量转化为积雪深度。本文参考拉格朗日冰上积雪模型（SnowModel-LG）模式对积雪分层压实的处理,简化为新、旧两个雪层,并在质量守恒条件下同时考虑新、旧雪层深度对压实增密的响应,将该物理过程加入HIGHTSI模式中。利用ERA-Interim再分析数据作为大气强迫,针对北极15个冰质量平衡浮标沿其漂移轨迹模拟了降雪积累期海冰表面雪密度变化对积雪深度变化的影响,在原HIGHTSI设置下分别采用定常块体雪密度均值330 kg/m3（T1试验）、接近实际的常数新雪密度200 kg/m3（T2试验）以及改进后框架下新、旧雪层随时间压实增密的雪密度（T3试验）计算积雪深度,并将模拟结果与浮标观测进行对比。结果表明,本文改进的算法对雪密度变化的处理更为合理,且能较好地再现积雪深度的变化;考虑新、旧雪层深度对压实增密的响应能较好地避免以较低的降雪密度持续过度积累,以浮标观测为标准,分层积雪密度压实计算得到的平均绝对误差相对T2减小了5 cm。 相似文献
3.
Tuomo M. Saloranta 《地球，A辑:动力气象学与海洋学》2000,52(1):93-108
A numerical 1‐dimensional fine grid sea ice thermodynamic model is constructed accounting specially for: (1) slush formation via flooding and percolation of rain‐ and snow meltwater, (2) the consequent snow ice formation via slush freezing, and (3) the effects of snow compaction on heat diffusion in snow cover. The model simulations from ice winter period 1979–90 are viewed against corresponding observations at the Kemi fast ice station (65 °39.8' N, 24° 31.4' E). The 11‐year averaged model results show good overall consistency with corresponding total ice thickness observations. The model slightly overestimates the snow ice thickness and underestimates the snow thickness in February and March, which is mainly addressed to the model assumption of isostatic balance (i.e., slush formation via flooding), which was probably not fully satisfied at the coastal Kemi fast ice station. Supposing that this assumption is nevertheless generally valid away from the very coastal fast ice zone, an estimate for sea ice sensitivity to changes in winter precipitation rate is produced. Increased precipitation leads to an increase only in snow ice thickness with little change in total ice thickness, while a reduction in precipitation of more than {213}50% causes a significant increase in total ice thickness. The difference in modeled total ice thickness for the case of artificially neglecting snow ice physics is about 25%, which indicates the importance of including snow ice physics in a sea ice model dealing with the seasonal sea ice zone. 相似文献
4.
K. G. Rubinshtein S. S. Gromov R. Yu. Ignatov 《Izvestiya Atmospheric and Oceanic Physics》2007,43(3):294-307
A short review of snow cover parametrizations used in different atmospheric general circulation models is given. The results of comparison of 20-year mean integral characteristics of snow cover for North America and Eurasia obtained in three Russian models in the AMIP-2 experiments with observations and reanalysis data are analyzed. Results of the models of the Hydrometeorological Centre of Russia, the Institute of Numerical Mathematics of the Russian Academy of Sciences, and the Voeikov Main Geophysical Observatory are used. It is shown that all models better reproduce snow cover characteristics of Eurasia than those of North America, and snow area is reproduced with smaller errors than snow mass. It is also shown that the fall and winter snow cover formation is simulated more closely to the reference data than the spring snowmelt. It is also shown that 20-year mean snow cover changes in watersheds of the Siberian Ob, Yenisei, and Lena rivers are well reproduced in all models. In the fall and winter period of snow cover formation, the model results are close to one another. During a spring rapid snowmelt, the model of the Hydrometeorological Centre is closer to the reference data. 相似文献
5.
Jiechen Zhao Tao Yang Qi Shu Hui Shen Zhongxiang Tian Guanghua Hao Biao Zhao 《海洋学报(英文版)》2021,40(7):129-141
A high resolution one-dimensional thermodynamic snow and ice(HIGHTSI) model was used to model the annual cycle of landfast ice mass and heat balance near Zhongshan Station, East Antarctica. The model was forced and initialized by meteorological and sea ice in situ observations from April 2015 to April 2016. HIGHTSI produced a reasonable snow and ice evolution in the validation experiments, with a negligible mean ice thickness bias of(0.003±0.06) m compared to in situ observations. To further examine the impact of different snow conditions on annual evolution of first-year ice(FYI), four sensitivity experiments with different precipitation schemes(0, half, normal, and double) were performed. The results showed that compared to the snow-free case,the insulation effect of snow cover decreased bottom freezing in the winter, leading to 15%–26% reduction of maximum ice thickness. Thick snow cover caused negative freeboard and flooding, and then snow ice formation,which contributed 12%–49% to the maximum ice thickness. In early summer, snow cover delayed the onset of ice melting for about one month, while the melting of snow cover led to the formation of superimposed ice,accounting for 5%–10% of the ice thickness. Internal ice melting was a significant contributor in summer whether snow cover existed or not, accounting for 35%–56% of the total summer ice loss. The multi-year ice(MYI)simulations suggested that when snow-covered ice persisted from FYI to the 10 th MYI, winter congelation ice percentage decreased from 80% to 44%(snow ice and superimposed ice increased), while the contribution of internal ice melting in the summer decreased from 45% to 5%(bottom ice melting dominated). 相似文献
7.
基于中国北极考察布放浮标观测和数值模拟的海冰和积雪厚度变化分析 总被引：1，自引：0，他引：1
Sea ice and the snow pack on top of it were investigated using Chinese National Arctic Research Expedition(CHINARE) buoy data.Two polar hydrometeorological drifters,known as Zeno? ice stations,were deployed during CHINARE 2003.A new type of high-resolution Snow and Ice Mass Balance Arrays,known as SIMBA buoys,were deployed during CHINARE 2014.Data from those buoys were applied to investigate the thickness of sea ice and snow in the CHINARE domain.A simple approach was applied to estimate the average snow thickness on the basis of Zeno~ temperature data.Snow and ice thicknesses were also derived from vertical temperature profile data based on the SIMBA buoys.A one-dimensional snow and ice thermodynamic model(HIGHTSI) was applied to calculate the snow and ice thickness along the buoy drift trajectories.The model forcing was based on forecasts and analyses of the European Centre for Medium-Range Weather Forecasts(ECMWF).The Zeno~ buoys drifted in a confined area during 2003–2004.The snow thickness modelled applying HIGHTSI was consistent with results based on Zeno~ buoy data.The SIMBA buoys drifted from 81.1°N,157.4°W to 73.5°N,134.9°W in 15 months during2014–2015.The total ice thickness increased from an initial August 2014 value of 1.97 m to a maximum value of2.45 m before the onset of snow melt in May 2015;the last observation was approximately 1 m in late November2015.The ice thickness based on HIGHTSI agreed with SIMBA measurements,in particular when the seasonal variation of oceanic heat flux was taken into account,but the modelled snow thickness differed from the observed one.Sea ice thickness derived from SIMBA data was reasonably good in cold conditions,but challenges remain in both snow and ice thickness in summer. 相似文献
8.
9.
The motion of a submarine in liquid under an ice plate covered with flooded snow is considered. The ice is modelled as an elastic plate and the snow cover is modelled as a viscous layer on the top of the plate. The submarine is modelled as a slender solid of revolution with scale 1:300. The experimental and theoretical study of the influence of the viscous snow layer on deflections of the floating ice plate is conducted. The viscous layer reduces the amplitudes of flexural-gravity waves. The greatest influence of the viscous layer on the plate deflections is achieved for velocities of the submarine, where the waves of maximum amplitude are generated. Theoretical results are in good qualitative and quantitative agreement with the model experiments. 相似文献
10.
The complex dielectric constant of snow at microwave frequencies 总被引：1，自引：0，他引：1
Tiuri M. Sihvola A. Nyfors E. Hallikaiken M. 《Oceanic Engineering, IEEE Journal of》1984,9(5):377-382
The complex dielectric constant of snow has been measured at microwave frequencies. New and old snow at different stages of metamorphosis have been studied. The results indicate that the complex dielectric constant is practically independent of the structure of snow. For dry snow, the dielectric constant is determined by the density. For wet snow, the imaginary part and the increase of the real part due to liquid water have the same volumetric wetness dependence. The frequency dependence of the complex dielectric constant of wet snow is the same as that of water. A nomograph for determining the density and wetness of wet snow from its dielectric constant is given. A snow sensor for field measurement of the dielectric constant has been developed. It can be used for determining the density and the wetness of snow by a single measurement. 相似文献
11.
A model is presented that simulates the formation of marine aggregates from particles of different origin inside a model of pelagic biological processes. Experiments are carried out with parameterizations appropriate for different types of aggregates, using different kinds of physical forcing, and compared to observations of dissolved inorganic nitrogen (DIN), particulate organic nitrogen (PON), marine snow concentration, and sedimentation.The occurrence of large, macroscopically visible aggregates (marine snow) can best be simulated with parameterizations that have been derived from in situ observations of marine snow, but not with a parameterization sufficient for dense particles. The parameterization strongly determines the amount and timing of deep export, as well as the post-bloom development of the food web in the upper layers.Detritus in aggregates plays a role mainly during times when zooplankton are abundant, as e.g. in the western Arabian Sea during Southwest Monsoon. Then the large aggregates as fast sinking vehicles may remove detritus quickly from shallow and mid-water depth, preventing the accumulation of nutrients that are produced via detritus decomposition. In this region, detritus contributes strongly to deep sedimentation. The nitrogen budget at this location with regard to the observations cannot be closed: depending on model type, either the model simulates too high sedimentation, or too high DIN. Possible causes for this mismatch include undercollection by sediment traps, inaccurate representation of physical processes in the model and the neglect of biological processes, such as production of dissolved organic matter or denitrification. 相似文献
12.
The effect of a snow cover on sea ice upon radar backscatter at microwave frequencies (X - andKu -baud) can be important. The effect of scattering from the snow cover on thesigmadeg of first-year ice is shown to be severe (5 cm of dry snow can raisesigmadeg by 8 dB at 9 GHz), while that onsigmadeg of multiyear ice is shown to be smaller. The low thermal conductivity of snow compared to that of sea ice effectively raises the temperature of the upper surface of the ice, resulting in higher dielectric constants for the ice, thereby modifying the backscatter both from the ice surface and from the scattering volume. The temperature effect of a 10-cm snow cover on 3-m-thick multiyear ice is to lower thesigmadeg by only about 0.3 dB for air temperature of-20deg C. The effect on 1-m-thick first-year ice is even less. Hence, the volume-scattering effect of snow is more important than the temperature effect. The presence of a wet snow cover can block the volume-scattering contribution of the multiyear ice. The effect of wet snow cover on first-year ice should be smaller than that Of dry, snow, becausesigmadeg of wet snow is lower than that of dry snow. 相似文献
13.
Bredow J. Gogineni S.P. Gow A.J. Blanchard P.F. Moore R.K. 《Oceanic Engineering, IEEE Journal of》1989,14(3):259-264
Fine-resolution X -band backscatter measurements were made at the US Army Cold Region Research and Engineering Laboratory in Jan. 1987. Backscatter data were collected from unmodified smooth ice and snow-covered ice and from ice from which the snow had been removed (slightly roughened ice). The results indicate that vertically polarized returns were consistently higher than horizontally polarized echoes from both the slightly roughened and snow-covered saline ice. A 6.5-cm-thick dry snow layer altered the σo of the original smooth-surfaced saline ice only slightly, but introduced a noticeable volume scattering component. It is shown that although substantial agreement exists between the bare first-year ice measurements and commonly used surface-scatter model predictions, a complete model of first-year ice must include a volume-scatter contribution 相似文献
14.
Comparison of seasonal and interannual variability of snow cover in Russian watersheds according to observations and reanalyses 总被引：1，自引：0，他引：1
V. M. Khan K. G. Rubinshtein A. B. Shmakin 《Izvestiya Atmospheric and Oceanic Physics》2007,43(1):59-69
Seasonal and interannual variability of the water equivalent of snow over the period 1966–1996 is analyzed with the use of the ERA/ECMWF reanalysis data, two versions of the NCEP reanalysis, and ground-based instrumental observations. Regions have been determined where snow characteristics from various sources are most consistent. In general, the snow water equivalent data from the ERA reanalysis are closer to the snow survey data than the NCEP reanalysis data. The best consistency of the water equivalent of snow in the reanalyses with measured data is observed in the period when the snow cover begins to form, in November and December, and the largest discrepancies are found for the snowmelt period, April and May. The interannual variability of the water equivalent in Asian Russia in the 1990s is better reproduced by the NCEP/DOE-II reanalysis. The snow cover data from satellite observations are compared with ground-based instrumental observations. It is shown that large discrepancies between the snow surveys and satellite observations may be observed at the snow-cover boundary during periods of snow formation and snowmelt. 相似文献
15.
远离河流和大陆的北冰洋冰区,大气沉降是210Po、210Bi、210Pb和7Be核素等最重要的来源。降雪一旦形成即被标记具有特定的210Po/210Pb活度比值,并降落到海冰表面,进入封闭状态。在封闭体系的冰雪中,随着时间推移,210Po从相对于210Pb强烈亏损的状态逐渐达到210Po-210Pb平衡状态。因此可以通过分析北冰洋表层冰雪中210Po-210Pb活度不平衡特征,量化冰区表层冰雪的表观年龄。本文搜集整理了北极地区气溶胶的210Po/210Pb活度比值,结合2018年中国第9次北极科学考察航次和2015年美国GEOTRACES 北冰洋航次中若干冰站表层冰雪的210Po/210Pb活度比特征,估算了北冰洋表层冰雪的表观年龄。结果表明,2018年中国冰站采集的表层冰雪年龄变化范围为106～272 d,远大于2015年美国冰站采集的表层冰雪的年龄;而两国冰站表层冰雪的年龄都呈现一定的纬度效应,即随着采样站位越靠近北极点,总体上表层冰雪的年龄呈现越来越大的特点,表明北极冰区表层冰雪越靠近北极点,表层冰雪被保留的时间会越长。210Po-210Pb 活度不平衡定年法可以作为一种评估北冰洋冰雪年龄的方法并与遥感技术协同使用。 相似文献
16.
Red and green snow caused by snow algal blooms is common on glaciers and snowfields worldwide. Reddish and greenish snow samples containing algae were collected at the vicinity of penguin rockeries on King George Island (62°13′S, 58°47′W, near the King Sejong Station), Antarctica in February 2017 to investigate their physiology. Eight pigments and six fatty acids were detected from the samples. No difference in pigment and fatty acid (FA) composition was found between reddish and greenish snow samples. In contrast, spectral profiling and mycosporine-like amino acids (MAAs) were different between reddish and greenish snow. Particularly in greenish snow, a high absorbance between 450–600 nm was observed. The average MAA concentration was 316.0 μg g-1 in greenish snow, which was higher than that of reddish snow (278.2 μg g-1). The MAA to Particulate organic carbon (POC) ratio (mg (g C)-1) for reddish snow (6.2 mg (g C)-1) was higher than that of greenish snow (2.6 mg (g C)-1). These results suggest that reddish and greenish snow are considered to be the same species based on pigment and FA composition. Compared with photoprotective pigments, MAAs offer snow algae a more effective photoprotection strategy to promote tolerance of natural levels of ultraviolet radiation (UVR). 相似文献
17.
利用常规观测、积雪深度逐时加密观测资料和欧洲中期天气预报中心（European Centre for Medium-Range Weather Forecasts,ECMWF）第五代大气再分析（ECMWF Reanalysis v5,ERA5）资料,对2023年12月13—15日山东一次极端暴雪天气过程积雪特征及其成因进行分析,得到以下结论：（1）此次过程是一次江淮气旋暴雪天气过程,具有持续时间长、降水相态复杂、基础温度低、降温幅度大和积雪深度厚等特征。（2）最大小时新增积雪深度可达8 cm;过程平均雪水比为0.7 cm·mm-1,呈“西大东小” 的分布特征。（3）有积雪的站近地面温度从开始降雪到地面产生积雪,气温和雪面温度均呈下降趋势,0 cm地温在降雪前期降温明显,积雪形成后地温不再明显变化。无积雪的站在整个降雪时段内近地面温度可分为4种情况。（4）雪水比随气温变化最明显;积雪形成之后地温对雪水比大小影响不大;当雪水比小于0.75 cm·mm-1时,雪水比随雪面温度降低而增大,当雪水比大于0.76 cm·mm-1后,雪面温度不再有明显变化。 相似文献
18.
海洋微塑料是全球共同面对的环境问题和挑战,然而目前海洋微塑料从源到汇的输运和沉积过程及影响机制尚不明确。已有研究发现微塑料颗粒的垂向沉降过程受到海洋雪等水体悬浮物质的影响,但是目前相关研究只局限于定性的观察分析。在实验室中模拟含有海洋雪的近岸水体环境,使细颗粒微塑料(PS微球、PVC颗粒)与海洋雪产生碰撞、聚集,观测微塑料或微塑料-海洋雪聚集体的沉降过程。研究结果表明,水体中含有海洋雪时,一方面海洋雪会促进微塑料颗粒自身的聚集,形成更大的聚集体;另一方面由于海洋雪包裹微塑料形成松散的聚集体,导致平均沉速减小。50 μm以下的微塑料其沉降过程受海洋雪的影响较大,平均沉速减小35%以上;微塑料密度越大,受海洋雪的影响越小,平均沉速减小10%以下。沉降速率的减缓,意味着微塑料在水柱中的停留时间增加,处于不同深度的水生生物可能有更多时间和概率与微塑料接触,增加了鱼类等水生生物摄入微塑料的风险。 相似文献
19.
Possibilities and problems for the extraction of backscattering coefficients from airborne and spaceborne Synthetic Aperture Radar (SAR) data are discussed. Corrections for system errors and for imaging geometry are described. Examples are given for airborne SAR data acquired in theX - andC -bands over a test site in the Austrian Alps and for Seasat SAR data of glacierized areas in Iceland. From these data, backscattering coefficients have been derived on a relative scale for wet snow, glacier ice, and several ice-free surfaces. Data of in situ measurements on surface roughness and on dielectric parameters are presented for interpretation purposes and as the basis for backscatter modeling. The SAR-derived results are compared with theoretical backscattering calculations which were based on the Kirchhoff model for surface scattering and on the Born approximation for snow volume scattering. 相似文献
20.
Abstract. In the water-column of the Gulf of Trieste (Northern Adriatic Sea) flocculent, amorphous aggregates known as marine snow reach maximum density and dimensions up to 20cm in diameter during summer months. Sampling of these fragile macro-aggregates was carried out by SCUBA-divers.
A large detrital component was found to be embedded in an organic matrix together with a large array of intact phytoplankton species. Heterotrophic bacterial density ranged from 2–65 × 108 cells-g-1 (marine snow dry wt) and is therefore of the same order of magnitude as in the surface layer of the sediments of the Gulf. In terms of biomass, bacteria reached only 30–95% of heterotrophic microflagellates.
A mean abundance of marine snow of 5g (marine snow dry wt) m-3 was obtained for the water-column above the pyenolinc. At this boundary layer, however, a mean abundance of about 10g (marine snow dry wt) m-3 led to the formation of a distinct, 10-50cm thick layer. Based on these data and sedimentation rates of marine snow to the pyenoclinc (38 g [marine snow dry wt] m-2 d-1 ) the potential ecological significance of these macro-aggregates for the pelagic system of the Gulf of Trieste is discussed. 相似文献
A large detrital component was found to be embedded in an organic matrix together with a large array of intact phytoplankton species. Heterotrophic bacterial density ranged from 2–65 × 10
A mean abundance of marine snow of 5g (marine snow dry wt) m