Is There a Paleolimnological Explanation for ‘Walking on Water’ in the Sea of Galilee?

Lake Kinneret (the Sea of Galilee) is a small freshwater lake (148 km² and a mean depth of 20 m) situated in northern Israel. Throughout recent history there have been no known records of a total ice formation on its top. Furthermore, given that convection requires an initial cooling of the entire lake down to 4 °C, it is difficult to imagine how such a low-latitude lake, presently subject to two-digit temperatures during the winter, could ever freeze. Lake Kinneret is, however, unique in the sense that there are dense (warm and salty) springs along its western shore. The dynamics of the regions adjacent to these springs are investigated using a one-dimensional nonlinear analytical ice model, a paleoceanographic record of the sea surface temperature of the Mediterranean Sea, and a statistical model. We show that, because the water directly above the plume created by the salty springs does not convect when it is cooled down to 4 °C, freezing of the region directly above the salty springs was possible during periods when the climate in the region was somewhat cooler than it is today. We refer to this localized freezing situation as ‘springs ice’. The analytical ice-model involves a slowly varying approach where the ice is part of a thin fresh and cold layer floating on top of the salty and warm spring water below. During the ice formation process, the ice is cooled by the atmosphere above and warmed by the spring water below. The plumes created by the springs have a length scale of 30 m, and it is argued that, during the Younger Dryas when the air temperature in the region was probably 7 °C or more cooler than today, ‘springs ice’ (thick enough to support human weight) was formed once every 27 years or less. During the cold events 1500 and 2500 years ago (when the atmospheric temperature was 3 °C or more lower than today) springs ice occurred about once in 160 years or less. Since the duration of these cold events is of the same order as the springs ice recurrence time, there is a substantial chance that at least one springs ice occurred during these cooler periods. With today's climate, the likelihood of a springs ice is virtually zero (i.e., once in more than 10,000 years). One set of those springs associated with the freezing is situated in Tabgha, an area where many archeological features associated with Jesus Christ have been found. On this basis, it is proposed that the unusual local freezing process might have provided an origin to the story that Christ walked on water. Since the springs ice is relatively small, a person standing or walking on it may appear to an observer situated some distance away to be ‘walking on water’. This is particularly true if it rained after the ice was formed (because rain smoothes out the ice’s surface). Whether this happened or not is an issue for religion scholars, archeologists, anthropologists, and believers to decide on. As natural scientists, we merely point out that unique freezing processes probably happened in that region several times during the last 12,000 years.     

越江隧道泵房冻结施工三维数值模拟

上海市复兴东路越黄浦江隧道工程,在南线和北线隧道内各设置一个泵房,其中泵房开挖土体,采用冻结法施工,为了保土体证开挖过程冻结壁的安全性,采用三维有限差分法FLAC3D,对整个施工过程进行了数值模拟,针对不同开挖方式,分析了开挖过程中冻土壁的力学变化,并对保证冻结安全的施工措施进行了分析,提出了指导施工的合理化建议。     

地下水储藏仓冻融过程的计算分析

Thawing and freezing processes are developed subsequently with filling of constructed- in-permafrost underground reservoirs with water. The paper proposes an approximate method to assess these processes with instant filling of reservoirs with water. This method is based on experimentally found mechanism of water cooling in underground reservoirs. Calculation results are given showing effects on the reservoir radius during thaw/freeze cycles, on water and soil temperature as well as on water storage duration.     

广西两次典型低温雨雪天气过程的成因对比分析

利用常规观测资料、ERA-Interim、NCEP/NCAR再分析资料,对比分析了2016年1月21—26日和2018年12月28日至2019年1月2日影响广西柳州的2次低温雨雪冰冻天气的成因。结果表明:2次过程期间中高纬均为两槽一脊形势,阻塞高压较常年同期偏强28dagpm;2018年过程期间近地层强冷平流的持续输送和高层冷空气的补充是柳州2018年气温低于2016年的重要原因,中低层持续的水汽输送及水汽辐合,长时间逆温层维持以及较强的逆温强度使得降雪持续时间及范围强于2016年;2016年过程期间中层强盛的西北气流使冷空气南下迅速,700hPa急流区以及850hPa风速辐合区的偏南导致明显的降雪主要出现在广西南部,柳州只出现少量降雪,温度回升较快。     

The application of finite elements to heat conduction problems involving latent heat

SummaryThe Application of Finite Elements to Heat Conduction Problems Involving Latent Heat A finite element method is developed for the solution of heat conduction problems which involve latent heat. The method is superior to other wellknown approaches to these problems in that it allows a wider range of material properties and boundary conditions to be dealt with, such as are encountered in complex engineering operations like ground freezing. The method is applied to simple triangular finite elements in this paper, although it could be extended to other types of element including three-dimensional ones. Several example problems are discussed and illustrated, and comparisons are made with other approaches where these can also be used.     

敦煌莫高窟古代生土建筑物风蚀机理与防护对策的研究*

利用低温冻融实验和风洞模拟实验研究古代生土建筑的风蚀机理,结果表明:挟沙风风蚀速率明显大于净风的风蚀速率,其风蚀率是净风的130倍,冻融是风蚀速率增大的一个重要因素,偏西风的降水和风蚀是造成莫高窟古代生土建筑风蚀毁坏的方要原因.实验表明,采取5%LS和10%PS防护材料是防止风蚀的一条重要途径.     

土质对人工冻土冻结温度影响的试验研究

不同土质的冻结温度是人工冻结法冻结壁设计重要依据。为研究土质对人工冻土冻结温度的影响,选取不同地区人工冻结法施工典型土层开展冻结温度试验,提供了不同地区典型土层的冻结温度范围,并结合水泥土、含盐土冻结温度试验进行对比分析。结果表明：同一地区不同土层的冻结温度随其土颗粒粒径的增大而增大;随水泥掺入比及龄期的增加,水泥土的冻结温度降低;随含盐量的增加,NaCl含盐土冻结温度线性降低,含盐量对氯盐土比对硫酸盐土的冻结温度影响更显著。研究成果对不同土性的冻结壁设计具有指导意义。     

大兴安岭湿地多年冻土区活动层水热特征分析

大兴安岭北部是我国唯一的中高纬度多年冻土区,其水热特征分析对陆气能量交换、生态系统和气候变化等研究有重要意义。基于2011—2020年期间对大兴安岭森林生态站附近的湿地多年冻土开展的气温和0~2 m地温和土壤含水量数据,对大兴安岭湿地多年冻土活动层的水热特征进行了分析。结果表明：湿地多年冻土活动层内地温的变幅随深度减小,且具有滞后性。融化期地表温度高于深层地温,冻结期相反。2012年、2013年、2019年和2020年的平均融化速率分别为0.49、0.61、0.47和0.56 cm·d^-1,向上平均冻结速率分别为1.34、2.12、2.58和1.65 cm·d^-1。向下平均冻结速率分别为1.69、1.02、3.32和1.00 cm·d^-1,最大融化深度分别为78.73、85.65、66.22和74.94 cm。2012年5月—2013年5月期间,土壤未冻水含量随地温变化的拟合关系较好,相关系数大于0.90,且深层拟合效果优于表层。融化期土壤水分变化幅度大,与地温的相关性差,随深度增加相关性减弱。湿地充足的水分为多年冻土的双向冻结提供了条件。研究成果可为大兴安岭湿地多年冻土区的冻融循环、水热耦合机理和模拟研究提供数据基础和理论依据。     

2016年广东一次罕见寒潮雨雪冰冻天气过程分析

利用常规气象观测资料、NCEP/NCAR再分析资料,分析了2016年1月下旬广东罕见大范围雨雪冰冻天气过程的大尺度环流和冷空气活动特征、动力和水汽条件,采用湿球温度讨论了降水相态和大气温度垂直结构特征。结果表明：此次寒潮过程环流形势为横槽转竖型,横槽下摆引导强冷空气向南迅猛爆发,以及伴随着异常强的冷高压、锋区、冷温度中心和冷温度平流的冷空气主力南侵,是本次寒潮过程粤北和广东中南部温度陡降的主要原因;700 hPa冷暖空气的辐合,以及700 hPa西南气流从孟加拉湾输送水汽经中南半岛北部到北部湾至华南地区加强并辐合,是造成雨雪冰冻天气产生的重要动力和水汽条件;在有利的大尺度环流、动力和水汽条件配合下,降水相态的变化与暖层强度及湿球温度密切相关,暖层的明显减弱及暖层下方湿球温度低于0 ℃冷冻层的强度增强,导致降水相态由雨向雪、雨夹雪、霰等固态降水转变;在发生固态降水的平均时段内,粤北地区中低层湿球温度均低于0 ℃,无明显融化作用,产生纯雪或雨夹雪的可能性大;而位置偏南的珠江三角洲地区仍存在浅薄的暖层,因此主要出现雨夹雪或霰。当寒潮入侵涉及华南降水相态预报时,需要注重实况探空和模式预报探空的大气温湿垂直结构的分析,更应重视湿球温度的研究和应用。     

广西持续性低温雨雪冰冻过程特征和气候成因分析

应用广西境内国家气象站逐日降水量、气温资料,定义了区域持续性低温雨雪冰冻过程。利用NCEP/NCAR逐日再分析等资料,使用合成分析等方法,研究了广西持续性低温雨雪冰冻过程的特征和气候成因。结果表明:(1)广西持续性低温雨雪冰冻过程在1980s之前平均出现次数为4次·10a^-1,过程平均日数为40d·10a^-1,而在1990s之后平均出现次数为2次·10a^-1,过程平均日数为23.7d·10a^-1。(2)持续性低温雨雪冰冻过程期间,亚洲大陆中低纬度地区冬季气温整体偏冷,500hPa位势高度距平场在亚洲50oN以北地区为正距平,以南为负距平,有大型稳定的长波斜脊横槽活动,华南上空由低层向高层有暖平流。