廈門大學(xué)海洋科學(xué)導(dǎo)論課件水文部分

1、Review,The shape and size of the earthPear-shaped; average radius(6371km);rotation rate (7.3×10-5s-1); L(1°) ?111.13km; L(1′) ?1.852km; 1 nautical mile(海里)=1.852km; 1kts(節(jié)）=1nautical mile/hour=0.51m/sDistribu

2、tion of Ocean and LandLand and water are not uniformly distributed on the surface of the earth,Ocean and SeaFour Principle OceanHydrological features of ocean, sea, fjord(bay), strait(channel),§2 海水的物理性質(zhì)Physic

3、al Properties of Sea Water,,,,2.1 Water,Most common substance on the earth’s surfaceOcean water makes up 98% of water inventory96.5% is water, 3.5% is salt and dissolved mineralsAccumulated on the surface from mass de

4、gassing of earth’s interior… still happening, but much lessOnly substance that exists naturally in all three states in the normal temperature range of earthSolid, Liquid, and Gas,分子結(jié)構(gòu)(Molecular structure)：極性，分子締合力,Hydr

5、ogen Bonds–polar molecules give water a structure that is responsible for a number of unique and important properties,溶解力強：水分子有很強的極性,密度變化異常,不遵從“熱脹冷縮”。最大密度時溫度是4攝氏度,,溫度<4，有利于水分子的締合；凍結(jié)為冰時，全部締合成一個巨大的分子締合體（分子晶體）．由于晶體結(jié)構(gòu)排列松散

6、，故密度減?。?dāng)溫度從0?4度以前，主要過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，熱運動加強，導(dǎo)致體積膨脹，密度所溫度增高而減小,密度變化異常是由水分子的締合造成的．,沸點(boiling point)和融點(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,2.2 溫度、鹽度和密

7、度的概念及關(guān)系Temperature, Salinity and Density,Lehodey,P. et al., 2000. El Nino Southern Oscillation and tuna in the western Pacific. Science,Temperature distribution in California coastal area,,,,長江水的擴展,2.2.1 Temperature,Mea

8、surementAbsolute Temperature TUnit: Kelvin (K)t [℃] = T [K]-273.15The practical temperature scale (1887, 1927, 1948, 1968, and 1990)ITS-90: the International Temperature Scale of 1990 ITS-68: the International Temp

9、erature Scale of 1968At 0℃　they are the same, and above ℃ its-90 is slightly cooler.t90－t68 = -0.002 at 10 ℃; -0.005 at 20 ℃, -0.007 at 30 ℃ and -0.010 at 40 ℃.t90=0.99976 t68; t68=1.00024 t90,2.2.2 Salnity,11種主要無機鹽，

10、占99.99%；,99% of all the salt ions in the sea are sodium (Na+), chlorine (Cl-), sulfate (SO4-2), Magnesium (Mg+2), calcium (Ca+2) and potassium (K+).,Definition of Salinity,Principle of constant proportion states that the

11、 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, to determine the total amoun

12、t 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,有機物全部氧化,所余固體物質(zhì)的總克數(shù)。(480度加熱48小時）    利用"海水組成恒定性"，測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:  &#

13、160; 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‰,S

14、alinity Based on Chlorinity,where chlorinity Cl is defined as “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Salinity Based on Conductivi

15、ty(1969),實用鹽標Practical Salinity Scale of 1978,The standard KCl solution contains a mass of 32.435 6 grams of KCl in a mass of 1.000 000 kg of solution.,Salinity is presented as numbers (dimensionless) but may find differ

16、ent terms: psu (practical salinity units)gram/kilogramgram/liter o/oo,At exactly one atmosphere and 15oC, S = 35.0,Measuring Salinity,EvaporateEasy to do, but residue is complex TitrationTraditional method prior

17、to mid-’60’sDetermine chlorinity and use empirical formulaS = 1.80655 ClConductivityUses a “resistance bridge”Current - CTD’s,密度（Density）：單位體積物體的質(zhì)量,Unit: kg/m3specific volume(比容)：單位質(zhì)量物體的體積 α =1/ρ (m3 · kg-1

18、),ρ(S,t,p)∝S,t-1,p,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 its in situ temperature and salinityst = (r - 1000) kg/m3,

19、在海面（p=0)海水密度僅為鹽度和溫度的函數(shù),密度超量：                                

20、0;kg/m3,The 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 important in the de

21、ep sea where salinity and temperature remain nearly constant.,The effect of Temperature,The effect of Salinity,S< 24.7, the density will increase with decreasing temperature until it reaches a maximum value and will t

22、hen decrease until the water freezes - just as pure water behaves.,S>24.7, the density will continue to increase with decreasing temperature until the water freezes,T↓，D↑,T↓, D↓,Table 4.4When S is constant and greate

23、r than 24.7, the density decreases as T increasesWhen T is constant, the density increases with increasing S,The density of seawater is greater than the density of freshwater because seawater contains dissolved salts.

24、The density of pure water at 3.98°C, or approximately 4°C, 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 water.,,1. 熱容（heat ca

25、pacity)、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))：單位質(zhì)量海水的熱容。單位：J/(K kg)定壓比熱Cp:在一定壓力下測定的比熱容。定容比熱Cv:在一定體積下測定的比熱容。,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

26、)、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、低鹽時隨溫度升高而減小，高溫、高鹽時隨溫度升高而增大。,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

27、增大而增大；在大氣壓力下，低溫、低鹽海水的熱膨脹系數(shù)為負值，說明當(dāng)溫度升高時海水收縮。由正轉(zhuǎn)負對應(yīng)的密度最大。,3. 壓縮性(Compressibility)、絕熱變化，位溫(Potential Temperature) 壓縮系數(shù)：單位體積海水，壓力增加1Pa體積的負增量。（單位：Pa-1)    若海水微團在被壓縮時，因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。若海水微團在

28、被壓縮過程中，與外界沒有熱量交換，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。,絕熱變化（Adiabatic Changes ）：    絕熱上升時，壓力減小，體積膨脹，對外做功，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，外力對海水微團做功，增加其內(nèi)能使溫度增加。NOTE: The rate of fall of temperature for dry air (due

29、to adiabatic changes) is 9.8 C/km. The rate of change of temperature with depth in the oceans (due to adiabatic changes) is less than 0.2 C/km.位溫(potential temperature， Θ)：    某一深度海水絕熱上升到海面時溫度稱該深度海水的位溫，

30、記為Θ 。比現(xiàn)場溫度低,Θ=t- Δt,t為現(xiàn)場溫度,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 change between the liquid and vapor stat

31、es is the latent heat of vaporization.)飽和水氣壓：     是指水分子由水面逃出和同時回到水中的過程達到動態(tài)平衡時，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，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):由分子的隨機運

32、動引起的熱傳導(dǎo)，主要與海水的性質(zhì)有關(guān)。 渦動熱傳導(dǎo)或湍流熱傳導(dǎo) :由海水塊體的隨機運動所引起，主要和海水的運動狀況有關(guān)。,Water masses (and water reservoirs) transmit heat energy by molecular conduction, density driven currents or convection, and by direct radiation. Wate

33、r 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 and rises as a result of a de

34、crease 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 grea

35、ter depth by mixing, or turbulence, in the water and by conduction.Surface cooling can increase the density of the surface layer and make it sink.,6. 沸點升高、冰點降低     海水的沸點(boiling point)和冰點(freezing point)

36、與鹽度有關(guān)，即隨著鹽度的增大，沸點升高而冰點下降。冰點溫度(freezing point)隨鹽度ｓ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運動時，由于水分子的不規(guī)則運動或者海水塊體的隨機運動(湍流)，在兩層海水之間便有動量傳遞，從而產(chǎn)生切應(yīng)力。2.滲透壓(p

37、enetration pressure)：   在海水與淡水之間放置一個半滲透膜，水分子可以透過，但鹽分子不能透過。那么，淡水一側(cè)的水會慢慢地滲向海水一側(cè)，使海水一側(cè)的壓力增大，直至達到平衡狀態(tài)。此時膜兩邊的壓力差，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的合力使自由表面趨向最小。,,,,,,,,,,