海冰热力模式的辐射参数化方案在渤海和波罗的海应用的比较

研究了海冰热力模式中的各种辐射参数化方案,对比了模式计算的太阳短波辐射、大气长波辐射以及海冰热力变化,并利用渤海和波罗的海观测资料进行比较和误差分析.冬季大部分时间太阳短波辐射对海冰热力过程的作用有限.简单计算方案一般满足海冰模式要求.误差主要受云和冰雪表面与大气之间的多重反射影响.长波辐射对表面热平衡和海冰质量变化起重要作用.长波辐射参数化方案的计算结果受环境因素影响.云量参数化有待进一步改进.海冰模式计算结果的精度与长波辐射计算精度有一致性.     

南极普里兹湾海冰数值模拟试验

海冰在全球气候的变化过程中,具有举足轻重的作用。在气候模拟中,海冰预报的准确性直接影响到对气候的中、长期预测。海冰的成长和消融受诸多物理过程控制,其中海冰的热力过程是最重要因素之一。     

Benthic Denitrification in the Gulf of Bothnia

Denitrification was measured over an 8-month period in the Bothnian Bay and the Bothnian Sea, the two northernmost basins of the Baltic Sea. The recorded rates varied between 0 and 0·94 mmol N m⁻²day⁻¹. In the Bothnian Sea, a seasonal pattern could be discerned with high rates in spring, no rate in summer and a moderate rate in winter. In the Bothnian Bay, no such seasonality was observed. It is suggested that denitrification in the Gulf of Bothnia is regulated by sediment nitrification. Calculation of annual mean rates of denitrification gave that the amount of nitrogen consumed by denitrification corresponded to 1·45×10⁴tons N year⁻¹for the Bothnian Bay and 3·45×10⁴tons N year⁻¹for the Bothnian Sea. A comparison with total N input (river runoff, point sources and atmospheric deposition) to the two basins showed that the proportion of N removed through denitrification amounted to 23% for the Bothnian Bay and 31% for the Bothnian Sea.     

渤海海冰特征厚度分析

通过海冰生消机理和数值试验,讨论了渤海海冰特征厚度的存在条件;对不同厚度的海冰表面温度、冰面热量收支、冰面下热传导和太阳辐射透射量进行了对比分析,分析了渤海海冰向特征冰厚的动态演化过程;在不同气温、风速、相对湿度和海洋热通量等气象和水文条件下,对渤海特征冰厚进行了计算;讨论了海冰生消的动态平衡过程,分析了1997/1998年冬季辽东湾JZ20-2海域实测冰厚与特征冰厚的相互关系。对渤海特征冰厚分析将有助于渤海海冰数值模拟工作的开展和对不同重现期设计冰厚的推算。     

海冰动力过程的改进离散元模型及在渤海的应用

海冰的断裂、重叠和堆积等离散分布特性广泛地存在于极区和副极区的不同海域,并对海冰的生消、运移过程有着重要影响。针对海冰在不同尺度下的离散分布特点,发展海冰动力过程的离散元方法有助于完善海冰数值模式,提高海冰数值模拟的计算精度。为此,本文针对海冰生消运移过程中的非连续分布和形变特性,发展了适用于海冰动力过程的改进离散元模型(MDEM)。不同于传统离散元方法,该模型将海冰离散为具有一定厚度、尺寸和密集度的圆盘单元。海冰单元设为诸多浮冰块的集合体,其在运移和相互接触碰撞过程中,依照质量守恒发生单元尺寸、密集度和厚度的相应变化。基于海冰离散性和流变性的特点,该模型采用黏弹性接触本构模型计算单元间的作用力,并依据Mohr-Coulomb准则计算海冰法向作用下的塑性变形及切向摩擦力。为验证该模型的可靠性,本文对海冰在规则水域内的运移和堆积过程进行了分析,离散元计算结果与解析值相一致;此外,对旋转风场下海冰漂移规律的模拟进一步验证了本文方法的精确性。在此基础上,对渤海辽东湾的海冰动力过程进行了48h数值分析,计算结果与卫星遥感资料和油气作业区的海冰现场监测数据吻合良好。在下一步工作中将考虑海冰离散元模拟中的热力因素影响,发展具有冻结、断裂效应的海冰离散元模型,更精确地模拟海冰动力-热力耦合作用下的生消和运移过程。     

Properties of sea ice and overlying snow in the Southern Sea of Okhotsk

The general properties of sea ice and overlying snow in the southern Sea of Okhotsk were examined during early February of 2003 to 2005 with the P/V “Soya”. Thin section analysis of crystal structure revealed that frazil ice (48% of total core length) was more prevalent than columnar ice (39%) and that stratigraphic layering was prominent with a mean layer thickness of 12 cm, indicating that dynamic processes are essential to ice growth. The mean thickness of ice blocks and visual observations suggest that ridging dominates the deformation process above thicknesses of 30 to 40 cm. As for snow, it was found that faceted crystals and depth hoar are dominant (78%), as which is also common in the Antarctic sea ice, and is indicative of the strong vertical temperature gradients within the snow. Stable isotope measurements (δ¹⁸O) indicate that snow ice occupies 9% of total core length and that the mass fraction of meteoric ice accounts for 1 to 2% of total ice volume, which is lower than the Antarctic sea ice. Associated with this, the effective fractionation coefficient during the freezing of seawater was also derived. Snow ice was characterized by lower density, higher salinity, and nearly twice the gas content of ice of seawater origin. In addition, it is shown that the surface brine volume fraction and freeboard are well correlated with ice thickness, indicating some promise for remote sensing approaches to the estimation of ice thickness.     

Improvement of short-term sea ice forecast in the southern Okhotsk Sea

In this study, a numerical model of 7-day forecast of sea ice produced by the Japan Meteorological Agency was improved by the following approaches. First, a new ice dynamic model was introduced: the distributed mass/discrete floe model. The model takes account of discrete characteristics of ice floes and well simulates the ice edge location at low computational cost. Secondly, the grid size was reduced to 5 × 5 km for the future high resolution forecasts. Next, the sea surface current data was examined because it significantly influences sea ice movement. We applied two new datasets of HINO and Okhotsk Ocean General Circulation Model (Okhotsk OGCM), which are estimated by numerical simulations, for the 7-day forecast of sea ice. Ice southward speed in January and the whorl formations in February and March were well reproduced with Okhotsk OGCM datasets. Finally, the ocean heat flux at the ice-ocean interface was refined. As a result, we achieved an ice edge error reduction from 30.8 km to 23.5 km.     

44 Years Hindcast of the sea level and circulation in the Baltic Sea

The subject of the investigation was the multiyear hindcast of the sea level elevations and currents over the Baltic Sea. The approach follows to the HIPOCAS project conception and contained the 3D hydrodynamic model using boundary conditions from the atmosphere and catchment for 44-year period referring to the second half of the 20th century.     

渤海及黄海北部冰情长期变化趋势分析

统计分析上世纪50年代—2010年渤海及黄海北部海冰资料,对其年代际变化特征进行分析。上世纪50年代—90年代冰情总体呈缓解的趋势,2000年以来冰情略有加重。研究发现太阳活动与渤海及黄海北部冰情变化关系密切,太阳活动可能是渤海及黄海北部冰情长期变化重要影响因素。如果太阳黑子的周期长度比上一个周期长,那么周期内冰情较上一个周期严重。反之亦然。     

基于高光谱遥感的渤海海冰厚度半经验模型

Sea ice thickness is one of the most important input parameters for the prevention and mitigation of sea ice disasters and the prediction of local sea environments and climates. Estimating the sea ice thickness is currently the most important issue in the study of sea ice remote sensing. With the Bohai Sea as the study area, a semiempirical model of the sea ice thickness(SEMSIT) that can be used to estimate the thickness of first-year ice based on existing water depth estimation models and hyperspectral remote sensing data according to an optical radiative transfer process in sea ice is proposed. In the model, the absorption and scattering properties of sea ice in different bands(spectral dimension information) are utilized. An integrated attenuation coefficient at the pixel level is estimated using the height of the reflectance peak at 1 088 nm. In addition, the surface reflectance of sea ice at the pixel level is estimated using the 1 550–1 750 nm band reflectance. The model is used to estimate the sea ice thickness with Hyperion images. The first validation results suggest that the proposed model and parameterization scheme can effectively reduce the estimation error associated with the sea ice thickness that is caused by temporal and spatial heterogeneities in the integrated attenuation coefficient and sea ice surface. A practical semi-empirical model and parameterization scheme that may be feasible for the sea ice thickness estimation using hyperspectral remote sensing data are potentially provided.     

南极海冰变化及其气候效应研究述评

南极海冰是全球气候系统的重要组成部分。不同于北极海冰的快速减少,近40年来,南极海冰范围在2014年前是缓慢增加、后是突变减少。单一的大尺度大气环流因素无法解释南极海冰的长期变化趋势,海洋−大气相互作用对海冰的耦合影响还未得到充分研究。受南极海冰厚度遥感观测和数值模拟能力所限,现有数据仍无法准确量化全球变化背景下南极海冰的厚度和体积变化;目前南极海冰变化的气候效应还未充分明确。当前国内外对南极海冰研究的不足迫切要求发展长期可靠的南极海冰厚度数据,以突破南极海冰体积变化研究的难题,同时应综合考虑多气候模态和海气系统耦合的作用,研究南极海冰变化的机制及其气候效应。     

RNA:DNA ratios of Baltic Sea herring larvae and copepods in embayment and open sea habitats

Elucidation of important nursery habitats for young fish can aid in the management and assessment of fish stocks. Herring (Clupea harengus) in the Baltic Sea primarily spawn in coastal areas, but larvae are also present in off-shore, open sea areas. To investigate if sheltered coastal habitats provide a better growth environment for larval herring, we compared short-term growth (as indexed by whole body RNA:DNA ratios) of larval herring from three habitat types of the northwest Baltic proper (sheltered inner bay, exposed outer bay, and open sea). In addition, we compared individual RNA content of adult female Eurytemora affinis (a common Baltic copepod) among these different habitats. High RNA levels in these copepods indicate high production of nauplii, which are important food for larval herring. Both RNA:DNA ratios of larval herring and RNA content of E. affinis were significantly greater in embayment habitats, suggesting that the sheltered coastal areas are high quality nursery habitats for young Baltic herring.     

Numerical simulation for dynamical processes of sea ice

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渤海海冰现场监测的数字图像技术及其应用

在渤海冰区油气开发中,海冰给平台结构、油气运输和施工作业带来很大影响.油气作业区海冰参数精确、连续、实时的现场监测对分析油气开发的可靠性、检验海冰数值模式、校正海冰卫星遥感数据具有重要意义.针对渤海油气作业区的海冰运动和分布特性,通过数字图像技术对海冰的厚度、运动速度和密集度三个参数的提取进行了算法开发和软件研制.在2...     

基于MODIS热红外数据的渤海海冰厚度反演

Level ice thickness distribution pattern in the Bohai Sea in the winter of 2009–2010 was investigated in this paper using MODIS night-time thermal infrared imagery.The cloud cover in the imagery was masked out manually.Level ice thickness was calculated using MODIS ice surface temperature and an ice surface heat balance equation.Weather forcing data was from the European Centre for Medium-Range Weather Forecasts(ECMWF) analyses.The retrieved ice thickness agreed reasonable well with in situ observations from two off-shore oil platforms.The overall bias and the root mean square error of the MODIS ice thickness are –1.4 cm and 3.9 cm,respectively.The MODIS results under cold conditions(air temperature –10°C) also agree with the estimated ice growth from Lebedev and Zubov models.The MODIS ice thickness is sensitive to the changes of the sea ice and air temperature,in particular when the sea ice is relatively thin.It is less sensitive to the wind speed.Our method is feasible for the Bohai Sea operational ice thickness analyses during cold freezing seasons.     

渤海海冰现场监测的数字图像技术及其应用

在渤海冰区油气开发中,海冰给平台结构、油气运输和施工作业带来很大影响。油气作业区海冰参数精确、连续、实时的现场监测对分析油气开发的可靠性、检验海冰数值模式、校正海冰卫星遥感数据具有重要意义。针对渤海油气作业区的海冰运动和分布特性,通过数字图像技术对海冰的厚度、运动速度和密集度三个参数的提取进行了算法开发和软件研制。在2009-2010年采用该海冰数字图像监测软件对渤海辽东湾JZ20-2油气作业区的海冰参数进行了全冰期的连续监测,获得了翔实可靠的海冰厚度、密集度和冰速等海冰监测资料。现场监测应用表明,该海冰数字图像监测软件具有操作性强、精确度高、可靠性好的优点。该监测技术进一步完善后可广泛应用于渤海油气作业区的海冰现场监测,成为海冰业务化现场监测的重要组成部分。     

On the estuarine transport reversal in deep layers of the Gulf of Finland

The Gulf of Finland is a 400-km long and 48–135-km wide tributary estuary of the Baltic Sea featuring the longitudinal two-layer estuarine flow modified by transverse circulation. Longitudinal volume transport in the deep layer is investigated by decomposing it into an averaged, slowly changing estuarine component (due to large-scale density gradients, river discharge and mean wind stress) and wind-driven fluctuating component. The derived expression relates the total deep-layer transport to the projection of wind stress fluctuation to a site-specific direction. The relationship is tested and calibrated by the results from numerical experiments carried out with the three-dimensional baroclinic circulation model. For the entrance to the Gulf of Finland, winds from northeast support standard estuarine circulation and winds from southwest work against the density-driven and riverine flow. The deep estuarine transport may be reversed if the southwesterly wind component exceeds the mean value by 4–5.5 m s⁻¹. According to the data from hydrographic observations in the western Gulf of Finland, an event of advective halocline disappearance was documented in August 1998. Comparison of the deep-water transport estimates calculated from the wind data in 1998 with the observed salinity variations showed that the events of rapid decay of estuarine stratification were coherent with the estimated reversals of deep-layer volume transport, i.e. events of salt wedge export from the gulf.     

A note on the economics of Swedish Baltic Sea fisheries

The cod stocks in the Baltic Sea are important not only for fisheries but for the entire ecosystem utilized by numerous stakeholders around the coast. All such activities have economic values. In this note the economics of the Swedish Baltic Sea cod fishery is estimated in relation to the sector's interaction with other users of the Baltic Sea ecosystem. The results show a negative resource rent for the fishery, € −5 million without public expenses (subsidies and administrative costs), and € −13 million including public expenses. The interactions between the fisheries and tourism, seal population, carbon dioxide emissions, recreational fishing, and discards are discussed, and when monetary estimates are available these are related to the estimated resource rent.     

A spatial typology for the sea: A contribution from the Baltic

Marine spatial planning (MSP) has a need for spatial delimitation and for the identification of spatial classes. This paper reports on the findings of a pilot study that was undertaken to test the development of a data informed spatial typology for the Baltic Sea. The Baltic Sea is a comparatively shallow sea with nine adjoining countries and intense anthropogenic activities. The aim of the study was to assess the applicability and value of such a spatial typology for MSP. A spatial typology with seven different spatial classes was identified. The approach used here to identify a spatial typology could be used for seas worldwide.