本文關(guān)鍵詞： 河流淡水羽狀流 河口混合水羽狀流 口門外混合水羽狀流 三級(jí)鹽度鋒面 FVCOM　出處：《中山大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：在枯水期,珠江口存在一個(gè)自表到底的沿岸分布的羽狀流結(jié)構(gòu),該羽狀流與外海高鹽水在交界面處形成一個(gè)自表到底的羽狀流鋒面。河口區(qū)的羽狀流及鹽度鋒面不僅是河口區(qū)重要的生物高生產(chǎn)力區(qū),對(duì)河口的沉積過程及底部地形的發(fā)育也具有重要的作用。因此研究珠江口內(nèi)鹽度鋒面對(duì)海洋環(huán)境的保護(hù)與治理、生物活動(dòng)及生態(tài)過程的研究、河口區(qū)地形地貌的發(fā)育乃至人類的生活及生產(chǎn)都有重要的意義。目前對(duì)珠江口羽狀流及鹽度鋒面的細(xì)致特征和時(shí)空變化的研究并不多,因此有必要對(duì)其開展細(xì)致且充分的研究。本文建立了基于FVCOM的珠江河網(wǎng)、河口和陸架海耦合的三維水動(dòng)力模型。模型中將珠江三角洲河網(wǎng)區(qū)、河口區(qū)及外海區(qū)結(jié)合成一個(gè)整體區(qū)域,無論在水平向還是垂向上,模型網(wǎng)格都具有較高的分辨率。同時(shí)模型中還加入了具有高分辨率的WRF模型模擬的經(jīng)觀測(cè)值同化后空間和時(shí)間變化的風(fēng)場(chǎng)。這明顯改善了模型對(duì)羽狀流和鹽度鋒面的模擬結(jié)果。模型計(jì)算的潮汐、鹽度、流場(chǎng)及羽狀流結(jié)構(gòu)及其變化均與觀測(cè)資料驗(yàn)證良好,因此該模型能較好的模擬出珠江口枯水期的水文及水動(dòng)力特征。在論文中利用模型對(duì)珠江口的羽狀流沖淡水團(tuán)及鹽度鋒面特征作了較為細(xì)致和系統(tǒng)的分析。首先將珠江口整體沖淡水團(tuán)按照其鹽度性質(zhì)、主要驅(qū)動(dòng)力及能量輸入的不同,分為從西到到東、從口門內(nèi)到外的三級(jí)水團(tuán):河流淡水沖淡水團(tuán)、河口混合水沖淡水團(tuán)、口門外混合水沖淡水團(tuán)。然后計(jì)算了模型模擬的珠江口鹽度平面場(chǎng)的梯度,發(fā)現(xiàn)在三級(jí)沖淡水團(tuán)相互之間及其與外海水的交界面處存在三級(jí)鹽度鋒面結(jié)構(gòu)。并對(duì)三級(jí)沖淡水團(tuán)及鹽度鋒面結(jié)構(gòu)的時(shí)空變化特征進(jìn)行了分析,結(jié)果表明珠江口三級(jí)沖淡水團(tuán)及鹽度鋒面結(jié)構(gòu)隨著潮汐過程呈現(xiàn)周期性變化。珠江口羽狀流及其鹽度鋒面結(jié)構(gòu)主要由陸地上的徑流、潮汐和風(fēng)應(yīng)力驅(qū)動(dòng),這三種驅(qū)動(dòng)力因其時(shí)空變化而對(duì)其影響各不相同。為分析徑流、潮汐和風(fēng)應(yīng)力對(duì)珠江口沖淡水及鹽度鋒面產(chǎn)生的動(dòng)力機(jī)制,研究作了幾組不同風(fēng)場(chǎng)和潮汐條件下的數(shù)值實(shí)驗(yàn)。分析結(jié)果表明:1)珠江口第一級(jí)鹽度鋒面的形成機(jī)制較復(fù)雜,可能與徑流、潮汐、風(fēng)均相關(guān),但徑流對(duì)第一級(jí)鹽度鋒面形成產(chǎn)生的作用最大;2)風(fēng)應(yīng)力產(chǎn)生向岸的�？寺斶\(yùn)是第二級(jí)鹽度鋒面形成的主要原因。3)第三級(jí)鹽度鋒面是沖淡水與外海高鹽水的交界面,它的形成雖然與潮汐和風(fēng)無關(guān),但它對(duì)風(fēng)的響應(yīng)十分敏感,風(fēng)應(yīng)力愈強(qiáng),第三級(jí)鹽度鋒面愈強(qiáng),且向口門內(nèi)推移的距離也越遠(yuǎn)。4)潮汐混合減弱了風(fēng)對(duì)鹽度鋒面的作用,即潮汐的存在使第二、三級(jí)鹽度鋒面強(qiáng)度減弱。但潮汐作用是落潮時(shí)淇澳島下方的局地羽狀流及其鋒面結(jié)構(gòu)(屬第一級(jí)鹽度鋒面)形成的關(guān)鍵因素。
[Abstract]:In the dry season, the Pearl River Estuary has a plume flow structure which is distributed from the surface to the end of the coast. At the interface between the plume flow and the high brine in the open sea, a plume front is formed from the surface to the bottom. The plume flow and salinity front in the estuary area are not only the important biological high productivity areas in the estuary area. It also plays an important role in the sediment process of estuaries and the development of bottom topography. Therefore, the study on the protection and management of the salt front in the Pearl River estuary to the marine environment, the study of biological activities and ecological processes. The development of topography and geomorphology, as well as the life and production of human beings, are of great significance. At present, there are few studies on the detailed characteristics and temporal and spatial changes of the plume flow and salinity front in the Pearl River Estuary. Therefore, it is necessary to carry out a detailed and full study. In this paper, a three-dimensional hydrodynamic model based on FVCOM for the coupling of Zhujiang River network, estuary and shelf sea is established. In the model, the Pearl River Delta river network is taken into account. The estuary area and the offshore area combine into a whole area, either horizontally or vertically. The model meshes have higher resolution. At the same time, the wind field simulated by WRF model with high resolution has been added to the model. The spatial and temporal variations after assimilation of observed values have been greatly improved. This obviously improves the model's response to plume flow and salt. Simulation results of the degree front. Tide calculated by the model. The salinity, flow field and plume flow structure and their variations are all well verified by the observed data. Therefore, the model can well simulate the hydrological and hydrodynamic characteristics of the Pearl River Estuary during the dry season. Firstly, the model is used to make a detailed and systematic analysis of the characteristics of the plume water mass and salinity front in the Pearl River Estuary. The whole water mass of the Pearl River Estuary is diluted according to its salinity. The main driving forces and energy input are divided into three water masses from west to east, from the inside to outside of the mouth: stream fresh water dilute water mass, estuary mixed water flushing fresh water mass. The mixed water at the entrance of the mouth is used to flush the fresh water mass. Then the gradient of the salinities plane field of the Pearl River Estuary simulated by the model is calculated. It is found that there is a third-order salt front structure between the three grade dilute water masses and the interface between them and the outer sea water, and the temporal and spatial variation characteristics of the three grade diluted water masses and the salt front structures are analyzed. The results show that the third-order diluted water mass and salinity front structure of the Pearl River Estuary change periodically with the tidal process, and the plume flow and its salinity front structure are mainly driven by the runoff, tide and wind stress on the land. These three kinds of driving forces have different influence on them because of their space-time variation. In order to analyze the dynamic mechanism of runoff, tidal and wind stress on the water and salinity front of the Pearl River Estuary. Several numerical experiments under different wind and tidal conditions have been carried out. The results show that the formation mechanism of the first salinity front in the Pearl River Estuary is complex and may be related to runoff, tide and wind. However, runoff has the greatest effect on the formation of the first salinity front. 2) the main reason for the formation of the second-order salinity front is the migration of the wind stress to the shore. 3) the third-order salinity front is the interface between the dilute water and the high brine in the open sea, although its formation is independent of the tide and the wind. However, it is very sensitive to the wind response. The stronger the wind stress, the stronger the third-order salinity front, and the farther the distance from the mouth door. 4) the tidal mixing weakens the effect of the wind on the salinity front. That is, the existence of tide weakens the intensity of the second and tertiary salinity front, but the tidal action is the key factor for the formation of the local plume and its frontal structure (which belongs to the first salinity front) under the lower tide of Qi'ao Island.
【學(xué)位授予單位】：中山大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P731

【共引文獻(xiàn)】

相關(guān)期刊論文 前1條

1 齊慶輝;諸裕良;謝寧寧;;珠江河口航道整治工程對(duì)咸潮上溯的影響研究[J];水運(yùn)工程;2015年10期

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本文編號(hào)：1467019