海水的物理性质

1、Review The shape and size of the earthPear-shaped; average radius(6371km);rotation rate (7.310-5s-1); L(1) 111.13km; L(1) 1.852km; 1 nautical mile(海里)=1.852km; 1kts(节）=1nautical mile/hour=0.51m/s Distribution of Ocean and LandLand and water are not uniformly distributed on the surface of the earth O

2、cean and Sea Four Principle Ocean Hydrological features of ocean, sea, fjord(bay), strait(channel)2 海水的物理性质Physical Properties of Sea Water2.1 Water Most common substance on the earths surface Ocean water makes up 98% of water inventory 96.5% is water, 3.5% is salt and dissolved minerals Accumulated

3、 on the surface from mass degassing of earths interior still happening, but much less Only substance that exists naturally in all three states in the normal temperature range of earth Solid, Liquid, and GasHydrogenHydrogenOxygen105 deg分子结构分子结构(Molecular structure)：极性，分子缔合力：极性，分子缔合力 Hydrogen Bondspol

4、ar molecules give water a structure that is responsible for a number of unique and important properties 溶解力强：水分子有很强的极性 密度变化异常密度变化异常不遵从不遵从“热胀冷缩热胀冷缩”。最大密度时温度是。最大密度时温度是4摄氏度摄氏度 温度4，有利于水分子的缔合；冻结为冰时，全部缔合成一个巨大的分子缔合体（分子晶体）由于晶体结构排列松散，故密度减小当温度从04度以前，主要过程是较大的缔合分子逐渐分解成为较小的分子，所以体积收缩，密度增大4度时，热运动加强，导致体积膨胀，密度所温度增高而

5、减小密度变化异常是由水分子的缔合造成的密度变化异常是由水分子的缔合造成的沸点(boiling point)和融点(melting point)、比热(specific heat)、蒸发潜热(latent heat of vaporization)等热性质比氧的同族化合物高 热性质特殊热性质特殊2.2 温度、盐度和密度的概念及关系Temperature, Salinity and DensityLehodey,P. et al., 2000. El Nino Southern Oscillation and tuna in the western Pacific. ScienceTemperat

6、ure distribution in California coastal area长江水的扩展2.2.1 Temperature Measurement Absolute Temperature T Unit: Kelvin (K) t = T K-273.15 The practical temperature scale (1887, 1927, 1948, 1968, and 1990) ITS-90: the International Temperature Scale of 1990 ITS-68: the International Temperature Scale of

7、1968 At 0they are the same, and above its-90 is slightly cooler. t90t68 = -0.002 at 10 ; -0.005 at 20 , -0.007 at 30 and -0.010 at 40 . t90=0.99976 t68; t68=1.00024 t902.2.2 Salnity11种主要无机盐，占99.99%； 99% of all the salt ions in the sea are sodium (Na+), chlorine (Cl-), sulfate (SO4-2), Magnesium (Mg+

8、2), calcium (Ca+2) and potassium (K+). Definition of Salinity Principle of constant proportion states that the absolute amount of salt in sea water varies, but the relative proportions of the ions is constant. Because of this principle, it is necessary to test for only one salt ion, usually chlorine

9、, to determine the total amount of salt present.海水组成恒定性原理 1) 传统的盐度定义(1902)： 1kg海水中将(Br-,I-)以氯置换，碳酸盐分解为氧化物,有机物全部氧化,所余固体物质的总克数。(480度加热48小时） 利用海水组成恒定性，测定出其中某一主要成分的含量，便可推算出海水盐度。2) 氯度: 1kg海水中将(Br-,I-)以氯代替，所含氯的总克数。 转换为盐度的关系式为：S=0.030+1.8050Cl Salinity Based on Chlorinitywhere chlorinity Cl is defined as “

10、the mass of silver required to precipitate completely the halogens in 0.328 523 4 kg of the sea-water sample.”(1969)(1902) 电导温度电导温度Salinity Based on Conductivity(1969) 实用盐标实用盐标Practical Salinity Scale of 1978The standard KCl solution contains a mass of 32.435 6 grams of KCl in a mass of 1.000 000 kg

11、 of solution.Salinity is presented as numbers (dimensionless) but may find different terms: lpsu (practical salinity units)lgram/kilogramlgram/literl o/ooMeasuring Salinity Evaporate Easy to do, but residue is complex Titration Traditional method prior to mid-60s Determine chlorinity and use empiric

12、al formulaS = 1.80655 Cl Conductivity Uses a “resistance bridge” Current - CTDs 密度（Density）：单位体积物体的质量VmUnit: kg/m3 specific volume(比容)：单位质量物体的体积 =1/ (m3 kg-1)2.2.3 Density st (sigma-t)(条件密度): Shorthand method of expressing the density of a sample of seawater at atmospheric pressure as determined by

13、its in situ temperature and salinitys st = ( - 1000 - 1000) kg/m3在海面（p=0)海水密度仅为盐度和温度的函数n密度超量： kg/m3The effect of Pressure Pressure has relatively little effect on density compared to salinity and temperature, however, the density will increase with increasing pressure (or depth) and becomes importan

14、t in the deep sea where salinity and temperature remain nearly constant. The effect of TemperatureThe effect of Salinity S24.7, the density will continue to increase with decreasing temperature until the water freezesT，DT, D Table 4.4 When S is constant and greater than 24.7, the density decreases a

15、s T increases When T is constant, the density increases with increasing STNo SaltSalt 20253035-1Ice 0.9171.016061.020101.0241300.999841.016071.0200810.999901.016051.0200520.999941.016031.0200130.999961.015981.0199540.999971.015931.0198850.999961.015861.01980100.999701.015321.01980150.999101.014501.0

16、1832 The density of seawater is greater than the density of freshwater because seawater contains dissolved salts. The density of pure water at 3.98C, or approximately 4C, is 1.0 g/cm3. The density of seawater of average salinity is about 1.0278 g/cm3. Because of this, fresh water will float on ocean

17、 water. 1. 热容（heat capacity)、比热容(specific heat) 热容(heat Capacity)：海水温度升高1K所吸收的热量。（单位：J/K） 比热容(specific heat capacity)：单位质量海水的热容。单位：J/(K kg) 定压比热Cp:在一定压力下测定的比热容。 定容比热Cv:在一定体积下测定的比热容。2.3 海水的热力学性质Energetic property of sea water二者皆是温(T)、盐(S)、压(P)的函数。Cp在海洋学中较常用，比Cv值略大。Cp值随盐度的增高而降低，随温度的变化比较复杂，低温、低盐时随温度升高而

18、减小，高温、高盐时随温度升高而增大。 Heat capacities of some common materials 2. 热膨胀 热膨胀系数：海水体积受热膨胀或收缩其相对变化率。是T、S、P的函数。单位：-1 海水的热膨胀系数比纯水的大，且随温度、盐度和压力的增大而增大；在大气压力下，低温、低盐海水的热膨胀系数为负值，说明当温度升高时海水收缩。由正转负对应的密度最大。SptVV,)(13. 压缩性(Compressibility)、绝热变化，位温(Potential Temperature)n 压缩系数：单位体积海水，压力增加1Pa体积的负增量。（单位：Pa-1) 若海水微团在被压缩时，因

19、和周围海水有热量交换而得以维持其水温不变，则称为等温压缩。若海水微团在被压缩过程中，与外界没有热量交换，则称为绝热压缩。海水的压缩系数随温度、盐度和压力的增大而减小。tStp,)(1- 绝热变化（Adiabatic Changes ）： 绝热上升时，压力减小，体积膨胀，对外做功，消耗内能导致温度降低；绝热下沉时，压力增加，体积减小，外力对海水微团做功，增加其内能使温度增加。 NOTE: The rate of fall of temperature for dry air (due to adiabatic changes) is 9.8 C/km. The rate of change of

20、 temperature with depth in the oceans (due to adiabatic changes) is less than 0.2 C/km. 位温(potential temperature， )： 某一深度海水绝热上升到海面时温度称该深度海水的位温，记为 。比现场温度低=t- tt为现场温度4. 蒸发潜热(latent heat of vaporization)和饱和水气压 比蒸发潜热： 使单位质量海水化为同温度的蒸汽所需的热量，称为海水的比蒸发潜热，以L表示，单位是焦耳每千克或每克,记为J/kg或J/g。(The heat needed for a cha

21、nge between the liquid and vapor states is the latent heat of vaporization.) 饱和水气压： 是指水分子由水面逃出和同时回到水中的过程达到动态平衡时，水面上水汽所具有的压力。 5. 热传导(transmission of heat ) 相邻海水温度不同时，热量由高温处向低温处转移，这就是热传导。 分子热传导:由分子的随机运动引起的热传导，主要与海水的性质有关。 涡动热传导或湍流热传导 :由海水块体的随机运动所引起，主要和海水的运动状况有关。 Water masses (and water reservoirs) tran

22、smit heat energy by molecular conduction, density driven currents or convection, and by direct radiation. Water is a poor conductor and heat is transferred inefficiently in water by conduction. Convection transfers heat in the oceans as water is cooled and sinks with increasing density or is warmed

23、and rises as a result of a decrease in its density due to the higher temperature. The oceans are heated from above by solar radiation. This energy is absorbed by the water at shallow depths. Heat energy in shallow water can be transferred to greater depth by mixing, or turbulence, in the water and b

24、y conduction. Surface cooling can increase the density of the surface layer and make it sink.6. 沸点升高、冰点降低 海水的沸点(boiling point)和冰点(freezing point)与盐度有关，即随着盐度的增大，沸点升高而冰点下降。冰点温度(freezing point)随盐度的增加而降低。 2.3海水的其他物理性质(Another physical property of sea water) 1. 粘滞性(viscosity)： 当相邻两层海水作相对运动时，由于水分子的不规则运动或者海水块体的随机运动(湍流)，在两层海水之间便有动量传递，从而产生切应力。2.渗透压(penetration pressure)： 在海水与淡水之间放置一个半渗透膜，水分子可以透过，但盐分子不能透过。那么，淡水一侧的水会慢慢地渗向海水一侧，使海水一侧的压力增大，直至达到平衡状态。此时膜两边的压力差，称为渗透压。3. 表面张力(surface tension)： 液体的自由面上，由于分子之间的吸引力所形成