EI NIO PHENOMENON AND EXTENDED ASSOCIATE PATTERN ANALYSIS

To study the causes of El Nino Phenomenon the Extended Associate PatternAnalysis (EAPA) is set up with monthly sea surface wind stress and precipitation besides Sea LevelPressure (SLP) and Sea Surface Temperature (SST) in or over the Pacific and related seas since 1979in present paper. The results show that El Nino Phenomenon means a SST redistribution, coveringalmost the whole Pacific that needs a huge amount of energy provided by air-sea interaction in themost Pacific regions; It is the wester burst and wind convergence, coming from meddle latitudesdirectly, instead of Kelvin waves that produce the strong SST warm signal in Nino regions; Twonegative SLP anomalies in middle of the North and South Pacific, most likely produced by the averageair pressure decreasing effect of explosive cyclones through precipitation, and the positive SLPanomaly o-ver the Asia-Australia land bridge, coming mainly from the south hemisphere with a littleinfluence from the Asian continent, are the three major causes for El Nino onset, they work togetherto produce anomalous wind convergence in Nino regions and wester burst in middle of the North andSouth Pacific that result in a warm tongue and cold pincers gearing together; Basically, during itsearly stage the ocean is forced by the atmosphere, while during its late stage the atmosphere isforced by the ocean.

FISSION LAWS OF INITIALLY INTERFACE SOLITARY WAVES IN TWO-LAYER OCEAN

A 2-D KdV equation of two-layer stratified o-cean with 2-D topography isrecapitulated in the present paper. Based on a reduced version of this 2-D KdV equation, the fissionlaws of the initially internal solitary waves are studied by means of numerical calculation. Fromthe numerical results , it is shown that the initially interface solitary waves can fission on thecontinental slope like the initially surface solitary waves and the fission process is a significantgenerating mechanism of internal interface soliton packet on the continental shelf.

UNIFICATION AND APPLICATIONS OF MODERN OCEANIC/ATMOSPHERIC DATA ASSIMILATION ALGORITHMS

The key mathematics and applications of various modern atmospheric/oceanicdata assimilation methods including Optimal Interpolation (OI), 4-dimensional variational approach(4D-Var) and filters were systematically reviewed and classified. Based on the data assimilationphilosophy, i. e. , using model dynamics to extract the observational information, the commoncharacter of the problem, such as the probabilistic nature of the evolution of theatmospheric/oceanic system, noisy and irregularly spaced observations, and the advantages anddisadvantages of these data assimilation algorithms, were discussed. In the filtering framework, allmodern data assimilation algorithms were unified: OI/3D-Var is a stationary filter, 4D-Var is alinear (Kalman) filter and an ensemble of Kalman filters is able to construct a nonlinear filter.The nonlinear filter such as the Ensemble Kalman Filter (EN-KF), Ensemble Adjustment Kalman Filter(EAKF) and Ensemble Transformation Kalman Filter (ETKF) can, to some extent, account for thenon-Gaussian information of the prior distribution from the model. The flow-dependent covarianceestimated by an ensemble filter may be introduced to OI and 4D-Var to improve these traditionalalgorithms. In practice, the performance of algorithms may depend on the specific numerical modeland the choice of algorithm may depend on the specific problem. However, the unification ofalgorithms allows us to establish a unified test system to evaluate these algorithms, which providesmore insights into data assimilation philosophies and helps improve data assimilation techniques.

A STUDY ON VARIABILITY OF SEA SURFACE TEMPERATURE IN TROPICAL PACIFIC, INDIAN OCEAN AND RELATED AIR CIRCULATION

Canonical Correlation Analysis (CCA) was a-dopted in the present paper tostudy the of Sea Surface Temperature (SST) in the tropical Pacific, Indian Ocean and related aircirculation. The results show that on the seasonal time scale, El Nino events can be divided intotwo types: the east one and the middle one. For the middle type the SST variations appear contrarilyin the tropical Pacific and Indian O-cean, and the anomalous SST decreases in the east butincreases in the northwest and south-middle of the tropical Indian O-cean, specially in the east ofMadagascar Island. And vice versa. On annual time scale, when the Asian continent high gets strongerand the deepened Aleutian low shifts southeastward, both of them trigger an onset of the El Ninoevents. Contrarily, the La Nina events take place. On decadal time scale, there are two basic modesof air-sea system over the tropical Pacific and Indian Ocean. Firstly, when the Asian continent highgets stronger and deepened Aleutian low shifts southeastward, the anomalous SST increases in themiddle and east of the proical Pacific, extending to the subtropical regions, and so in most of thetropical Indian Ocean, specially in the northeast of Madagascar Island and nearby. And vice versa.Secondly, when the Asian continent high gets stronger in the north and the Aleutian low decreasesfixedly or even disappears, the anomalous SST decreases slightly in middle of the tropical Pacificand the temperate northern Pacific but increases weakly in other regions, the anomalous SSTincreases in the south but decreases in the north of the tropical Indian O-cean, and the SSTincreases more obviously in southeast of Madagascar Island. And vice versa. The linear trends ofglob- al warming seems to play a certain role for the El Nino onsets.

A UNIVERSAL IN TAILING WAVETRAIN GENERATION

A universal in tailing wave-train generation of forced soliton generationover topography is found theoretically as the flows are at the resonant points and it is examinedwith the numerical calculation of the corresponding fKdV e-quatioa From the comparisons, it is shownthat theoretical and numerical results on the invariance is in good agreement and the theory givenin this paper does not include the modulus truncation, any free constant and unknown function.

STUDY OF NON-BOUSSINESQ EFFCET ON SEA SURFACE HEIGHT

A set of equations was derived for a non-Boussinesq ocean model in thispaper. A new time-splitting scheme was introduced which incorporates the 4th-order Runge-Kuttaexplicit scheme of low-frequency mode and an implicit scheme of high-frequency mode. With thismodel, potential temperature, salinity fields and sea surface height were calculated simultaneouslysuch that the numerical error of extrapolation of density field from the current time level to thenext one could be reduced while using the equation of mass conservation to determine sea surfaceheight. The non-Bouss-inesq effect on the density field and sea surface height was estimated bynumerical experiments in the final part of this paper.