廈門(mén)大學(xué)海洋科學(xué)導(dǎo)論課件水文部分lect15-1205

1、風(fēng)浪成長(zhǎng)與風(fēng)時(shí)風(fēng)區(qū)的關(guān)系 H隨t而，到ts,H= L ts L,Hs 海區(qū)某一點(diǎn)達(dá)到定常，則其靠風(fēng)區(qū)上沿的點(diǎn)都已達(dá)定常，而其它的點(diǎn)則有繼續(xù)成長(zhǎng)的趨勢(shì) 過(guò)渡區(qū)的波高不隨地點(diǎn)變化 過(guò)渡區(qū)與定常區(qū)的分界線(xiàn)隨時(shí)間向風(fēng)向的下方移動(dòng) 定常狀態(tài)的波浪只受制于風(fēng)區(qū)，而過(guò)渡狀態(tài)的風(fēng)浪只受制于風(fēng)時(shí) 無(wú)論風(fēng)區(qū)長(zhǎng)度多大，風(fēng)時(shí)多長(zhǎng)，風(fēng)浪不可能無(wú)限地成長(zhǎng),Review,2. 涌浪的傳播 H ；，T； H；傳播距離很長(zhǎng)；小振幅波波動(dòng)公式適用,The shallower the water, the greater the interaction between the wave and the bottom alters

2、the wave properties, eventually causing the wave to collapse.,近岸浪,Mustang Island regular wave trains,周期保持不變: T=T0,Deep water wave,Shallow-water wave,1) 波速和波長(zhǎng)的變化,當(dāng)波浪傳至淺水和近岸時(shí)，其周期最為保守。 水深變淺時(shí)，其波速、波長(zhǎng)都逐漸變小,Wave refraction,2),(折射）,Refraction is the bending of a wave into an area where it travels more slowl

3、y.,EF-isobath(等深線(xiàn))，h1h2,c1c2.,After dt，AA ，AA=c1dt ；BB，BB=c2dt,So: The crest of the wave closer to shore travels slower and refracts the wave,波峰線(xiàn)有逐漸與等深線(xiàn)平行的趨勢(shì)，波向線(xiàn)與等深線(xiàn)垂直 海底凸出的海岬處，波向線(xiàn)輻聚，海浪較大；凹進(jìn)的海岸，波向線(xiàn)輻散，海浪較小,Wave refraction and longshore drift,3. Wave Height,L1 e1 C1*,L2 e2 C2*,在兩波向線(xiàn)間取兩個(gè)斷面，e1、e2為其單位水面內(nèi)

4、的平均波動(dòng)能量；L1、L2為兩斷面處所取兩波向線(xiàn)間的垂直距離；C1*、C2*為兩斷面處波浪能量的傳播速度。由于能量保持恒定，因此,(1) 折射因子,反映折射作用使波向線(xiàn)間的距離發(fā)生的變化,水深變淺或水下高地或岸線(xiàn)突出波向線(xiàn)輻聚L21 波高增加H2H1,水深變深或水下凹地或岸線(xiàn)凹處波向線(xiàn)輻散L2L1 折射因子1 波高減小H2H1,(2) 能量傳播速度隨水深的變化, 可見(jiàn)波浪傳到近岸，波高的變化完全取決于能量的變化。一般來(lái)說(shuō)，D的作用比折射因子大，但在海岬與海灣處，由于波向轉(zhuǎn)折，其影響對(duì)H的變化往往起著明顯的作用。,在D的影響下，波浪從深水淺水，波高開(kāi)始略有降低然后隨著水深的減小而增大,4. Wa

5、ve breakers(波浪破碎）,Wave steepness (stability) is a ratio of wave height divided by wave length (= H/L).,When H/L is larger than or equals 1/7 (H/L 1/7), the wave becomes unstable. There are three types of breakers:, Spilling breakers溢出型 , Plunging breakers 崩捲型 , and Surging breakers崩塌型 .,溢出型,Spilling

6、 breaker(溢出型,溢波) Upper part of crest oversteepens , spills down the front face of advancing wave, continually breaking and gradually loosing energy across the surf zone Occur on gradually sloping sea floor Tend to wide surf zone Most common breaker type,Plunging breaker(崩卷型碎波,卷波) Entire wave front s

7、teepens, curls and collapses releasing much energy instantaneously Tends to occur where sea floor steep Narrow surf zone,Plunging waves,崩捲型,Surfers at La Jolla CA,崩塌型碎波,Surging breaker(崩塌型碎波,崩波 ) Flat, low waves do not become oversteepend, or break Move up and down the beach reflect much energy seaw

8、ard Often occur on steepest beaches,Surging waves,Rip current,5. Wave reflection波浪反射,Wave bounces back after encountering an object Can interfere with incoming waves and cause standing waves Minimum energy loss occurs when a wave is reflected at a right angle Less ideal reflections may produce stand

9、ing waveswhich have no net movement Reflection occurs at an angle equal to the angle of approach,近岸水域入射波與反射波疊加形成的棋盤(pán)狀波形(86年6月攝自桃圓觀(guān)音海邊)。,反射波浪前進(jìn)遭遇固體邊界時(shí)，為滿(mǎn)足水流只能平行於邊界面運(yùn)動(dòng)之限制，於是會(huì)產(chǎn)生向相反方向傳播的波浪，這就是反射現(xiàn)象。,6. Wave diffraction波浪繞射,Wave Diffraction-bending of waves around objects Bending occurs on a smaller scale

10、than refraction Any point on a wave front can be a source which can propagate in any direction,Wave diffraction,6 Tide,The tides rise and fall in response to forces generated by the Sun and the Moon and the rotation of the Earth-Moon system about their common center of mass. The actual pattern of th

11、e tides varies from place to place around the world.,物體在天體引潮力的作用下所產(chǎn)生的周期性運(yùn)動(dòng)。,高潮高,低潮高,潮差,高潮,高潮,低潮,落潮時(shí),漲潮時(shí),高 度,時(shí)間,落,潮,潮,漲,潮汐要素示意圖,基本要素 Tidal element,Flood(漲潮)、High tide(高潮)、平潮、高潮時(shí)、高潮高(high water)、ebb(落潮)、low tide(低潮)、停潮、低潮時(shí)、低潮高(low water)、 rise time(漲潮時(shí))、fall time(落潮時(shí))、tide range(潮差),高潮時(shí),低潮時(shí),Tide patte

12、rns,Diurnal tides(日潮) One high tide and one low tide each day Semi diurnal tides(半日潮) Two high tides and two low tides each day Semi diurnal mixed tides(混合潮) the water levels of the two high tides and of the two low tides are unequal,Three common tide patterns,混合潮： 不正規(guī)半日潮：一個(gè)朔望月內(nèi)大多數(shù)日子是半日潮，少數(shù)日子是全日潮 不正

13、規(guī)日潮：一個(gè)朔望月內(nèi)大多數(shù)日子是日潮，少數(shù)日子是半日潮,World distribution of tide patterns,(1) 正規(guī)半日潮：如我國(guó)沿岸鴨綠江口-龍鐵山、龍口-威海、山東南部-江蘇-杭州灣、寧波以南-廈門(mén)等 (2) 不正規(guī)半日潮：如我國(guó)沿岸遼寧長(zhǎng)興島-營(yíng)口-葫蘆島、澎湖列島、臺(tái)灣附近及釣魚(yú)島附近、鎮(zhèn)海角 (3) 正規(guī)日潮：我國(guó)北方的秦皇島老黃河口、南方的?？?、三亞、北部灣是世界上最典型的全日潮海區(qū)之一 (4) 不正規(guī)日潮：如河北省灤河口以北，瓊州海峽東口等處、東山,潮汐不等現(xiàn)象,潮汐日不等：一天之中兩個(gè)潮的潮差不等，漲潮時(shí)和落潮時(shí)也不等 高高潮（higher high w

14、ater)低高潮(lower high water) 高低潮(Higher low tide)低低潮(lower low tide) 大潮和小潮,Tides can be classified based upon their monthly record. The tidal range varies slightly each day in a systematic pattern. Spring tide(大潮): phase when tidal range is maximal. Neap tide（小潮）: phase when tidal range is minimal.Tid

15、es,Astronomic knowledge related to the tide,1. Celestial sphere(天球)：地球?yàn)橹行?，任意長(zhǎng)為半徑，內(nèi)表面分布著各種各樣天體的球面.,2.天軸：地軸無(wú)限延長(zhǎng)的直線(xiàn) Celestial Pole(天極)：天軸與天球的交點(diǎn)。 the north and south poles extended into spaceNorth Celestial Pole (NCP，北天極) and the South Celestial（NCP,南天極) 3. Zenith(天頂)： The point on the celestial sphere

16、directly overhead. Nadir(天底)： The point on the celestial sphere directly underneath. 過(guò)觀(guān)測(cè)點(diǎn)的鉛垂直線(xiàn)無(wú)限延長(zhǎng)后，與天球交于兩點(diǎn)，頭上一點(diǎn)稱(chēng)為天頂，正對(duì)朝下的一點(diǎn)稱(chēng)為天底,北天極,南天極,春分點(diǎn),2327,509,夏至點(diǎn),冬至點(diǎn),秋分點(diǎn),降交點(diǎn),升交點(diǎn),天 軸,時(shí)角Z,赤緯,天頂距,天子午圈,時(shí)圈,天赤道,天體,日時(shí)圈,日赤緯,天頂,天底,天體方位圈,北天極,南天極,春分點(diǎn),2327,509,夏至點(diǎn),冬至點(diǎn),秋分點(diǎn),降交點(diǎn),升交點(diǎn),天 軸,時(shí)角Z,赤緯,天頂距,天子午圈,時(shí)圈,天赤道,天體,日時(shí)圈,日赤緯,天

17、頂,4. 三個(gè)圈 天子午圈(Celestial Meridian )：地心為中心，過(guò)天極和天頂?shù)拇髨A圈。天頂和天子午圈具有地方性。 時(shí)圈(Hour Circle,or Circle of declination )：地心為圓心，過(guò)天極和天體的大圓圈 天體方位圈：過(guò)天頂、天底和天體的大圓圈 中天(transit)：天體通過(guò)天子午圈叫中天?？拷祉敃r(shí)叫上中天，靠近天底時(shí)稱(chēng)下中天,6. 三個(gè)道 天赤道(the Celestial Equator)：赤道無(wú)限擴(kuò)大，與天球相交的大圓叫天赤道 黃道(the Ecliptic)：太陽(yáng)周年視運(yùn)動(dòng)的軌道。運(yùn)動(dòng)方向與地球公轉(zhuǎn)方向一致：自西向東 白道：月球繞地球公轉(zhuǎn)

18、的結(jié)果使得月球在天體上有一個(gè)視運(yùn)動(dòng)軌道，稱(chēng)為白道, SUN,Earth,a,b,c,d,e,A,B,C,D,E,地球繞太陽(yáng)公轉(zhuǎn)一周，如白圈所示（abcde），但地球上的人看來(lái)，似乎是太陽(yáng)繞地球旋轉(zhuǎn)。那么，太陽(yáng)在天球上的投影每年也繞著地球做一周的視運(yùn)動(dòng)（ABCDE），此視運(yùn)動(dòng)即為黃道,太陽(yáng)、地球、月亮的關(guān)系,三個(gè)交角 黃赤交角：黃道面與天赤道面交角為2327 白黃交角：白道面與黃道面交角為509 白赤交角：白道面與天赤道面交角 升交點(diǎn)位于春分點(diǎn)時(shí)，極大值： 2327+ 509=2836 升交點(diǎn)位于秋分點(diǎn)時(shí)，極小值： 2327- 509=1818,黃道面,赤道面,6633,黃,白,黃,白,黃,白,黃,白,黃道、白道以及赤道面相交情形,8. 六個(gè)點(diǎn) (1)升交點(diǎn)(ascending node,) ：月球從黃道之南向黃道之北運(yùn)動(dòng)與黃道相交的點(diǎn) (2) 降交點(diǎn)(descending node,) ：月球從黃道之北向黃道之南運(yùn)動(dòng)與黃道相交的點(diǎn) (3) 春分點(diǎn)(th