HQi thao khoa hpc - Hop tac Qudc tg digu tra, nghign ctiu tai nguygn vi mfli tni6ng bign VARIABILITY OF THE WATER CIRCULATION IN THE EAST VIETNAM SEA UNDER INFLUENCE ATMOSTPHERIC PROCESSES IN WINTER Galina A Vlasova' Bui Hong Long \ Nguyen Ba Xuan \ Le Dinh Mau^ /- V.I.Il'ichev Pacific Oceanological Institute, Far Eastern Branch, Russian Academy of Sciences, 43 Baltiyaskya Street, Vladivostok, 690041, Russia, E-mail: gavlasova@mail ru; - Institute of Oceanography, Cau Da 01, Vinh Nguyen, Nha Trang, Vietnam, E-mail: haiduong@vnn.vn; ba_xuan04@yahoo.com; ledinh_mau@yahoo.com Introduction East Vietnam Sea is one of the largest marginal seas of the World Ocean; it makes part of the Pacific Ocean basin Its waters wash the coasts of twelve densely populated states of the South East Asia, including the Peoples' Republic of China, Malaysia, Thailand, Cambodia, Philippines, Vietnam, which economic activity is closely related to the natural resources development in the water area of the sea Practical relevance of research in the East Vietnam Sea has considerably increased last decades in relation to the active development of biological, mineral, and energy resources of the sea East Vietnam Sea is crossed by important sea routes connecting the Pacific Ocean and Indian Ocean The water area of the East Vietnam Sea yields the great bulk of the seafood harvested by the nearby countries Particularly, resources of a shelf zone of the East Vietnam Sea are rapidlly exploited For about twenty years it has been conducted industrial oil recovery on a southern shelf, in the central and northern shelves it is being carried out intensive geophysical survey of oil and gas Besides, hydrometeorological conditions in the considered water area are extremely complicated and influence the climate of not only nearby countries, but also all counfries of the Asian-Pacific Region In this view, necessity of studying hydrometeorological conditions of the East Vietnam Sea becomes actual and topical for scientists of tae entire world The purpose of the given paper is study of variability of the water circulation in the East Vietnam Sea under influence regional atmospheric processes in winter Method The given quasi-stationary baroclinic model based on solving complete nonlinear equations of the ocean hydrotherraodynamics and turbulent diffusion of the conservatives admixtures, is related to a class of modem multi-layer models [3] It Galina A Vlasova 251 Workshop •iniemMion.l Coopeiarinn on bivestieation and Researeh of Manne Nattiral Resource and Envimm;^ presupposes a principle of self-similarity of the second order (a similarity of tl, vertical distt^ibution) and considers a real spatial disfribution of the water density interaction with the atmosphere, p-effect, and water exchange tarough the straiij' bottom topography, and the coast outiine A peculiar feahrre of the given model is that it is used some class of functions allowing to separate the variables by spatial coordinates and to pass to tae dependence on tae function of self- similarity TQ determine these functions it is solved tae problem of calculating the spatial temporal disfribution of the sea system parameters In oceanography, we know the functions possessing the natural self-similarity, i.e the similarity of the vetticjl distribution First of all, it is temperature and density of the water The density can be described by the model determined by the data of in situ observations carried out in the ocean at some characteristic station In this case, while using the models of temperature and density, the problem of determining the main physical is reduced to solving a plain system of equations The given problem is solved by a method of minimal errors of Academician Marchuk [1], which is applied for each equation in the general iteration process As a result of solving this problem, at each step of iteration, by the explicit rations obtained as a result of integrating the initial equations by the vertical coordinate We calculate the components of the current velocity, the sea level, temperature distribution, a depth of the homogeneous layer, and the sea water density Salinity disfribution is calculated from the state equation To estimate its adequacy, the given model has been used in various areas of the World Ocean In a majority of cases, it is describing the physical processes knom from observations That has given us an opportunity to pass to a wider analysis of hydrodynamic characteristics Initial Data To solve the given problem it is used a hydrodynamic model calculating the integral functions of the flow on the surface The input information for the calculation of the waters circulation is: - Average monthly fields of the atmospheric pressure for the period of 20002008, corresponding to the earlier distinguished types of the atmospheric processes - The GDEM archive (Generalized Digital Environmental Model) - a global massive of the monthly averaged climatic data on temperature and salinity in the nods of a regular grid °x °; - The bank of the research cruise data "Ocean-2" of Pacific Oceanological Institute FEBRAS for the period of 1970-1990 The depta values were taken from tae massive ETOPO-5 To conduci calculations it was used a regular grid with the space of 1° in latitude and I'in 252 Galina A VlasovJ Hfli thao khoa hoc - Hop tac QuAc tg digu tta nghign cihi tai nguygn vi moi hilfmg bign longitude To form the given grid all input information was processed with the help of the interpolation method in the mode of Surfer (Kriging) Classirication of the types of the atmospheric processes Classification of types of the atmospheric processes over tae East Vietnam Sea is made by Polyakova [2] on the base of the frajectories of cyclones The "Strong wind" type of the atmospheric circulation (Fig la,b) is characterized in the presence of tae expressed anticyclone over east China In Fig la,b The "Strong wind" type of the atmospheric northern part of the sea circulation are observed considerable baric gradients In northern, and sometimes and in central parts of the sea strong winds of a northeast direction wita the speed of 15 m/s and more is prevailed The "Weak gradient field" type of the atmospheric circulation (Fig 2a,b) is characterized by Weaksradlent ^^y^CJ/" presence small baric gradient over all the East Vietnam Sea (one two isobars) Weak >^vOu_-.'"i\ and moderate wind mainly to m/s of unstable directions is observed The crest of anticyclone settles ii t^ /r• ^m ^ =t:^ Fig 2a,b The "Weak gradient field" type of the atmospheric circulation do-wn above the central or east China Analysis By results of calculations, the maps of the integral water circulation were built for the following types of atmospheric circulation: , [^ condition of the "Strong wind" type of the atmospheric processes in winter period (Fig 3) a" '^'^ ^^^* Vietnam Sea is captm^ed by cyclonic movement of waters except for Karimata sfrait and to the south of Hainan Island where Galina A Vlasova 253 Woricshop ••International Coopeiation on Investigation and Research of Marine Naniral Resource and Fnuirn- anticyclonic structures dominate In gulf of Thailand against the oen, anticyclonic circulation of waters the large cyclonic whirlwind is formed Alon northwest part of Kalimantan Island in southeast part o f the sea Powerliii cyclonic circulation is formed to Sv • In condition of the "Weai gradient field" type o f the ataiospheric processes in winter (Fig 4) f^ hydrodynamic pictare of region is identical to a picfru^e of curtents at the previous type except taat in a northwest part of gulf of Tonkin cyclonic movement of waters is observed and along o f island Kalimantan the powerful cyclonic movement is observed C o n c l u s i o n Fig The surface water circulation in East Vietnam Sea in December (Sv) under influence the "Strong wind" type of the atmospheric processes'circulation circulation For the first time on water areas of East Vietaam Sea functions of a stream have been designed for surfaces on base quasi-stationary baroclinic model By results of numerical modeling maps of currents on a surface have been constiiicted, and the analysis of variability o f the water circulation under influence of various types of atmospheric processes is carried out On water area o f East Vietaam Sea the c o m m o n laws and regional features are revealed in the winter At all circulation: types * Prevailing observed; Fig The surface water circulation in South China Sea in December (Sv) under influence the "Weakgradiemfield" type of the atmospheric processes of cyclonic atinospheric activity is * Anticyclonic activity in Karimata strait is observed always; * In anticyclonic activity around Hainan Island is observed At the regional types of the atmospheric circulation: Galina A Vlasova Hfli thao khoa hoc - Hprp tac Quflc tg uong digu tra, nghign cuu tai nguygn vi mfli tniimg bign * At the type of atmospheric circulation "Strong wind": the hydrodynamic picture of region is expressed more brightiy in its northern part; * In condition of the "Weak gradient field" type of the atmospheric processes along of island Kalimantan the powerful cyclonic circulation is observed REFERENCES Marchuk G.I Numerical decision of the tasks of the atmospheric and ocean dynamic on the basis of a splitting method Hydrometeopub, Leningrad, 974, 303 p Polyakova A.M Classification of atmospheric processes over the South China Sea // Meteorol and Hydrol., J^«5, 2011, P 17-24; Vlasova G.A., Vasiliev A'.S., Shevchenko G.V Spatial and temporal variability of the water structure and dynamics of the Sea of Okhotsk, Nauka, Moscow, 2008,359 p Galina A Vlasova 255 ... us an opportunity to pass to a wider analysis of hydrodynamic characteristics Initial Data To solve the given problem it is used a hydrodynamic model calculating the integral functions of the flow... of types of the atmospheric processes over tae East Vietnam Sea is made by Polyakova [2] on the base of the frajectories of cyclones The "Strong wind" type of the atmospheric circulation (Fig la,b)... la,b The "Strong wind" type of the atmospheric northern part of the sea circulation are observed considerable baric gradients In northern, and sometimes and in central parts of the sea strong winds