【作者】 雷瑞波；

【导师】 李志军； 程斌；

【作者基本信息】 大连理工大学 ， 港口、海岸及近海工程， 2009， 博士

【摘要】 气候变暖及其伴随事件,特别是海平面上升,对我国海岸和近海工程会产生一系列影响,气候变化的准确预测是制定适应气候变化工程对策的依据。极区和亚极区海冰和淡水冰是全球气候系统重要组成部分之一,也因其对气候变化的敏感性一直都被当作物候学指标。目前制约海冰或淡水冰生消过程数值模式发展的不在于模式结构本身,除了数值算法的改进,更在于参数化方案的优化。本文以2005年11月至2006年12月中国第22次南极科学考察度夏和越冬期间普里兹湾中山站附近固定冰生消过程的热力学观测数据,以及2009年2月至4月环波罗的海地区芬兰和爱沙尼亚7个淡水湖泊湖冰不同生消阶段的光学观测数据为基础,对冰层生消过程及其关键参数进行了分析研究。作者全程负责上述两个观测项目的现场执行工作。第一章评价了全球气候变化及其对我国海岸和近海工程的可能影响;阐述了固定冰和湖冰的研究意义;综述了海冰和淡水冰生消过程、南极固定冰热力学观测、以及湖冰光学性质等议题的研究进展。第二章叙述了中山站附近固定冰生消过程的热力学观测以及环波罗的海地区湖冰不同生消阶段的光学观测所涉及的观测技术和现场实施情况。其中中山站附近固定冰热力学现场观测是迄今在普里兹湾海区实施的最为全面的固定冰热力学观测研究。实践中研制了一项基于磁致伸缩原理的冰/雪厚度测量技术,该技术现场测量精度为±2mm,是目前国际上报道精度最高的冰厚观测技术。第三章分析了固定冰生消过程,并对积雪热传导系数进行了计算和分析。夏季固定冰边缘线退缩过程与固定冰的消融过程相互促进。2006年固定冰生长期从2月持续到11月。依据高精度的冰厚观测数据首次对南极固定冰生长速率的日内变化进行了分析,结果表明极夜期间观测区域海冰生长率日内变化不明显,极夜前两个月和后两个月冰生长率日内变化明显,午后(12:00～15:00)生长率最低;冰内的热—盐耦合过程使得冰内盐度垂向分布在初冰期从“C-型”发展成“?-型”,该分布类型持续到冰发生消融,之后发展成“I-型”;风吹雪作用明显,使得积雪厚度较小,并以新雪为主,其热传导系数季节变化不明显。第四章基于剩余能量法利用冰生消和冰温廓线观测数据计算了中山站附近固定冰冰底海洋热通量,这是首次完全依据实测数据对东南极普里兹湾冰底海洋热通量的计算研究。冰底海洋热通量存在明显的季节变化,初冰期4月为11.8(±3.5)W/m~2,其后逐渐下降,最低值出现在9月,其值为1.9(±2.4)W/m~2,低水平的海洋热通量持续到11月中旬,之后迅速升高。海洋热通量的季节变化趋势与普里兹湾海冰密集度的季节变化趋势一致。除了海洋热通量趋于0W/m~2或冰生消趋于平衡的时期,引入海洋热通量能使斯蒂芬冰生长模式计算结果更好地逼近观测值。第五章讨论了对应光合作用有效辐射(Photosynthetically Active Radiation,PAR)的雪/冰光学特性与其层理结构的关系;评价了积雪层对冰层光通量乃至冰生消过程的影响;首次定量地比较了雪层、粒状冰层以及柱状冰层光学性质的差异;并对环波罗的海地区湖冰和中山站附近固定冰的生消过程进行了简单的对比分析。冰层PAR透射率主要受制于积雪层,当积雪层被清理后或随着春季到来逐渐融化后,冰层的PAR透射率显著增大。从冬季到春季,雪面反照率和雪层的消光系数都逐渐下降,但前者更为明显,春季雪面反照率约为冬季的1/4。冰层的消光系数只有积雪层的1/10～1/3,粒状冰层消光系数是柱状冰层消光系数的2～3倍,冰层的消光系数主要取决于粒状冰层的厚度比例。对于环波罗的海地区湖冰,积雪的隔热作用以及雪冰形成对冰层生消的影响不能忽视;积雪对中山附近固定冰的生长影响不大,没有雪冰形成。环波罗的海地区湖冰冰底来自水体的热通量季节变化平稳,短期变化不明显;中山站附近固定冰区冰底海洋热通量无论季节变化还是短期变化都十分强烈。本文给出的分析结果能为冰生消数值模式提供计算背景值和验证数据,并能为优化冰生消数值模式的参数化方案和完善天气气候模式中的冰模式提供支持。更多还原

【Abstract】 Global warming and its resulting events, special for sea level rising, would make some directly or indirectly impacts on costal and offshore engineers in China. Reasonable forecast of climatic change is crucial to put forward corresponding policy. Sea ice and fresh ice in polar or sub-polar regions are primary factors in global climate system; also serve as proxy climate records as their sensitivity to climatic change. The optimization of parameterization and the arithmetic are more important than the model strategy to develop the ice thermodynamic model. Based on the data derived from the field campaigns of landfast sea-ice thermodynamic observation off Zhongshan Station in Prydz Bay, East Antarctica from November 2005 to December 2006, and lake-ice optical observation in seven lakes located in the drainage basin of Baltic Sea (with 5 lakes in Finland and 2 lakes in Estonia) from February to April, 2009, the growth and decay processes of ice cover have been studied. Some key thermodynamic parameters have been quantified and analyzed. The author took all field works involved in this study.In the first chapter, global warming and its possible impacts on coastal and offshore engineers in China were evaluated. Significance of study on landfast sea ice and lake ice has been explored. Studies on the growth and decay processes of sea ice and fresh ice, field work of landfast sea-ice thermodynamic observation in Antarctica, and lake-ice optical properties have been reviewed.In the second chapter, the field campaigns and the involved monitoring techniques of landfast sea-ice thermodynamic observation off Zhongshan Station and lake-ice optical observation in the drainage basin of Baltic Sea have been presented. The former field campaign is characterized as the most comprehensive one for landfast sea-ice thermodynamic study in Prydz Bay to date. A new apparatus for monitoring sea-ice and snow thickness has been developed based on the magnetostrictive-delay-line principle. The apparatus has a precision of±2 mm, which is higher than that of the previous techniques for monitoring ice thickness.In third chapter, the growth and decay processes of landfast ice off Zhongshan Station have been studied. The thermal conductivity of snow cover has been quantified based on the air-snow-ice temperature profile. The recoiling of fast-ice marginal line toward the shore promoted the decay of landfast sea ice during summer, and vice versa. Ice-growth season lasted from February to November in 2006. The first step to study intraday variation in ice-growth rate for Antarctic landfast ice has been launched based on the field data of ice thickness with high resulotion. The results show that there was no obvious intraday variation in ice-growth rate during polar night, while an obvious minimal ice-growth rate can be detected at postmeridiem (12:00～15:00) during the two months preceding or after the polar night. The ice salinity profile was a "C-shape" profile, and then turned into a "?-shape" profile after brine drainage due to warm air and ice temperatures around March, this profile was kept to November, when melt-onset turned it into a "I-shape" profile. Strong winds and the consequent blowing snow played a pivotal role for snow redistribution at the experimental site, which resulted in a relatively thin snow cover on the ice. The thermal conductivity of the snow did not exhibit any seasonal dependence.In the fourth chapter, based on the so-called residual method, ice temperature profiles, combined with measurements of ice bottom ablation or accretion were used to estimate oceanic heat flux under landfast ice off Zhongshan Station, which is the first time to using this method to estimate oceanic heat flux under landfast ice in Prydz Bay completely based on the field data. The oceanic heat flux decreased from initial values of 11.8(±3.5)W/m~2 in April to an annual minimum in September with a value of 1.9(±2.4)W/m~2. It remained low through to late November, in mid December it increased sharply. The seasonal evolvement of the oceanic heat flux was similar with that of sea-ice concentration in Prydz Bay. Taking into account the oceanic heat, the calculated ice growth based on the Stefan’s Law improved except at times when the oceanic heat or the ice-growth rate approaching to zero.In the fifth chapter, the relationship between snow/ice optical properties related to the spectral region of photosynthetically active radiation (PAR) and their stratigraphical structure has been discussed based on lake-ice observation in the drainage basin of Baltic Sea, The optical properties of snow, granular ice and columnar ice have been compared quantitatively. The growth and decay processes of lake ice in the drainage basin of Baltic Sea have been compared in brief with those of landfast ice off Zhongshan Station. The PAR flux through ice cover was controlled by snow principally. When snow was removed or melted as the spring coming, the PAR flux would increase distinctly. The decline of snow albedo was more notable than that of snow extinction coefficient as spring coming. The snow albedo in spring was one fourth that in winter. Extinction coefficient of ice was about one tenth to on third that of snow, which was determined by the thickness ratio of granular ice basically as extinction coefficient of granular ice was twice to trebly that of columnar ice. The snow cover and the formation of snow ice complexed the ice growth and decay for the lake ice in the drainage basin of Baltic Sea, while as the snow was thin and no snow ice occurred over the landfast ice off Zhongshan Station, snow cover cannot make a significant impact on the ice growth and decay. The season vatiations in the heat from water under the lake ice in the drainage basin of Baltic Sea was stable and no short-term change can be detected. While, both the season vatiations and short-term changes in the oceanic heat under landfast ice off Zhongshan Station were vary distinct.The results derived from this study can provide background data and validation data for numerical simulation on the growth and decay processes of ice, support the optimization of the parameterization for ice thermodynamic modelling, and support the development of ice thermodynamic model coupled in the synoptic and climatic model.更多还原