海水物理性質(zhì)

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(節(jié)）=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 海水的物理性質(zhì)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分子結(jié)構(gòu)分子結(jié)構(gòu)(Molecular structure)：極性，分子締合力：極性，分子締合力 Hydrogen Bondspol

4、ar molecules give water a structure that is responsible for a number of unique and important properties 溶解力強(qiáng)：水分子有很強(qiáng)的極性 密度變化異常密度變化異常不遵從不遵從“熱脹冷縮熱脹冷縮”。最大密度時(shí)溫度是。最大密度時(shí)溫度是4攝氏度攝氏度 溫度4，有利于水分子的締合；凍結(jié)為冰時(shí)，全部締合成一個(gè)巨大的分子締合體（分子晶體）由于晶體結(jié)構(gòu)排列松散，故密度減小當(dāng)溫度從04度以前，主要過(guò)程是較大的締合分子逐漸分解成為較小的分子，所以體積收縮，密度增大4度時(shí)，熱運(yùn)動(dòng)加強(qiáng)，導(dǎo)致體積膨脹，密度所溫度增高而

5、減小密度變化異常是由水分子的締合造成的密度變化異常是由水分子的締合造成的沸點(diǎn)(boiling point)和融點(diǎn)(melting point)、比熱(specific heat)、蒸發(fā)潛熱(latent heat of vaporization)等熱性質(zhì)比氧的同族化合物高 熱性質(zhì)特殊熱性質(zhì)特殊2.2 溫度、鹽度和密度的概念及關(guān)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長(zhǎng)江水的擴(kuò)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種主要無(wú)機(jī)鹽，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.海水組成恒定性原理 1) 傳統(tǒng)的鹽度定義(1902)： 1kg海水中將(Br-,I-)以氯置換，碳酸鹽分解為氧化物,有機(jī)物全部氧化,所余固體物質(zhì)的總克數(shù)。(480度加熱48小時(shí)） 利用海水組成恒定性，測(cè)定出其中某一主要成分的含量，便可推算出海水鹽度。2) 氯度: 1kg海水中將(Br-,I-)以氯代替，所含氯的總克數(shù)。 轉(zhuǎn)換為鹽度的關(guān)系式為：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) 電導(dǎo)溫度電導(dǎo)溫度Salinity Based on Conductivity(1969) 實(shí)用鹽標(biāo)實(shí)用鹽標(biāo)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）：?jiǎn)挝惑w積物體的質(zhì)量VmUnit: kg/m3 specific volume(比容)：?jiǎn)挝毁|(zhì)量物體的體積 =1/ (m3 kg-1)2.2.3 Density st (sigma-t)(條件密度): 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)海水密度僅為鹽度和溫度的函數(shù)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. 熱容（heat capacity)、比熱容(specific heat) 熱容(heat Capacity)：海水溫度升高1K所吸收的熱量。（單位：J/K） 比熱容(specific heat capacity)：?jiǎn)挝毁|(zhì)量海水的熱容。單位：J/(K kg) 定壓比熱Cp:在一定壓力下測(cè)定的比熱容。 定容比熱Cv:在一定體積下測(cè)定的比熱容。2.3 海水的熱力學(xué)性質(zhì)Energetic property of sea water二者皆是溫(T)、鹽(S)、壓(P)的函數(shù)。Cp在海洋學(xué)中較常用，比Cv值略大。Cp值隨鹽度的增高而降低，隨溫度的變化比較復(fù)雜，低溫、低鹽時(shí)隨溫度升高而

18、減小，高溫、高鹽時(shí)隨溫度升高而增大。 Heat capacities of some common materials 2. 熱膨脹 熱膨脹系數(shù)：海水體積受熱膨脹或收縮其相對(duì)變化率。是T、S、P的函數(shù)。單位：-1 海水的熱膨脹系數(shù)比純水的大，且隨溫度、鹽度和壓力的增大而增大；在大氣壓力下，低溫、低鹽海水的熱膨脹系數(shù)為負(fù)值，說(shuō)明當(dāng)溫度升高時(shí)海水收縮。由正轉(zhuǎn)負(fù)對(duì)應(yīng)的密度最大。SptVV,)(13. 壓縮性(Compressibility)、絕熱變化，位溫(Potential Temperature)n 壓縮系數(shù)：?jiǎn)挝惑w積海水，壓力增加1Pa體積的負(fù)增量。（單位：Pa-1) 若海水微團(tuán)在被壓縮時(shí)，因

19、和周圍海水有熱量交換而得以維持其水溫不變，則稱為等溫壓縮。若海水微團(tuán)在被壓縮過(guò)程中，與外界沒(méi)有熱量交換，則稱為絕熱壓縮。海水的壓縮系數(shù)隨溫度、鹽度和壓力的增大而減小。tStp,)(1- 絕熱變化（Adiabatic Changes ）： 絕熱上升時(shí)，壓力減小，體積膨脹，對(duì)外做功，消耗內(nèi)能導(dǎo)致溫度降低；絕熱下沉?xí)r，壓力增加，體積減小，外力對(duì)海水微團(tuán)做功，增加其內(nèi)能使溫度增加。 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. 位溫(potential temperature， )： 某一深度海水絕熱上升到海面時(shí)溫度稱該深度海水的位溫，記為 。比現(xiàn)場(chǎng)溫度低=t- tt為現(xiàn)場(chǎng)溫度4. 蒸發(fā)潛熱(latent heat of vaporization)和飽和水氣壓 比蒸發(fā)潛熱： 使單位質(zhì)量海水化為同溫度的蒸汽所需的熱量，稱為海水的比蒸發(fā)潛熱，以L表示，單位是焦耳每千克或每克,記為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.) 飽和水氣壓： 是指水分子由水面逃出和同時(shí)回到水中的過(guò)程達(dá)到動(dòng)態(tài)平衡時(shí)，水面上水汽所具有的壓力。 5. 熱傳導(dǎo)(transmission of heat ) 相鄰海水溫度不同時(shí)，熱量由高溫處向低溫處轉(zhuǎn)移，這就是熱傳導(dǎo)。 分子熱傳導(dǎo):由分子的隨機(jī)運(yùn)動(dòng)引起的熱傳導(dǎo)，主要與海水的性質(zhì)有關(guān)。 渦動(dòng)熱傳導(dǎo)或湍流熱傳導(dǎo) :由海水塊體的隨機(jī)運(yùn)動(dòng)所引起，主要和海水的運(yùn)動(dòng)狀況有關(guān)。 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. 沸點(diǎn)升高、冰點(diǎn)降低 海水的沸點(diǎn)(boiling point)和冰點(diǎn)(freezing point)與鹽度有關(guān)，即隨著鹽度的增大，沸點(diǎn)升高而冰點(diǎn)下降。冰點(diǎn)溫度(freezing point)隨鹽度的增加而降低。 2.3海水的其他物理性質(zhì)(Another physical property of sea water) 1. 粘滯性(viscosity)： 當(dāng)相鄰兩層海水作相對(duì)運(yùn)動(dòng)時(shí)，由于水分子的不規(guī)則運(yùn)動(dòng)或者海水塊體的隨機(jī)運(yùn)動(dòng)(湍流)，在兩層海水之間便有動(dòng)量傳遞，從而產(chǎn)生切應(yīng)力。2.滲透壓(penetration pressure)： 在海水與淡水之間放置一個(gè)半滲透膜，水分子可以透過(guò)，但鹽分子不能透過(guò)。那么，淡水一側(cè)的水會(huì)慢慢地滲向海水一側(cè)，使海水一側(cè)的壓力增大，直至達(dá)到平衡狀態(tài)。此時(shí)膜兩邊的壓力差，稱為滲透壓。3. 表面張力(surface tension)： 液體的自由面上，由于分子之間的吸引力所形成