模糊数学方法在南海北部海区水团分析中的应用

APPLICATION OF METHOD OF FUZZY SETS TO THE ANALYSIS OF WATER MASSES IN THE NORTHERN SOUTH CHINA SEA

本文将模糊数学的多种方法,用于南海北部海区的水团分析。在用模糊聚类方法划分水团时,提出了基于欧氏距离的相似关系,同时提出了基于F—检验而决定水团个数的方法。以模糊聚类划出的水团为基础,再用软划分方法,对水团边界和测样归属进行合理调整。根据上述结果及区域海洋学的分析,在该海区划出了8个水团:沿岸冲淡水团F、近岸混合水团M、暖表层水团WS、表层水团S、表—次层混合水团SU、次层水团U、次-中层混合水团UI和中层水团I。将各类水团在θ—S图解上的点集,归结为变形椭圆凸点集、半无界凸点集和单侧凹点集3种类型。分别提出了建立相应隶属函数的方法,并给出了拟合结果。计算了各季节各水团的熵,讨论了高熵和低熵水团的特征及形成原因。计算了各季节不同水团之间的格贴近度,借以讨论水团变性的特点和它们之间的相互关系。可将8个水团归纳为3种类型:径流冲淡型(F),浅海变性型(M、WS、S和SU),深海大洋型(U、UI和I),

Some methods of fuzzy sets are applied to the analysis of water masses in the north area of the South China Sea. In distinguishing water masses with fuzzy clustering method, the authors propose a fuzzy similar relation based on Euclidean distance, and suggest a method for determining the number of water masses by the F- test, and further adjust rationally the boundaries of water masses and the membership relation of samples by the elastic classification method. Eight water masses are distinguished in the area, i.e., Nearshore Diluted Water F, Nearshore Mixed Water M, Warm Surface Water WS , Surface Water S, Surface-Subsurface Mixed Water SU, Subsurface Water U, Subsurface-Intermediate Mixed Water UI and Intermediate Water I. These point-sets of various water masses on the θ-S diagram may be summed up in three types, that is, the deformed elliptical convex point-set, the half-boundless convex point-set and the point-set with single-side concave. For them, we have proposed methods of making their membership function respectively and have given the fitting results. The entropy of each water mass in four seasons is computed. The characteristics and the causes of formation of water masses with high entropy and low entropy are discussed. The lattice approach degrees between water masses in four seasons are calculated, and the modifying character of masses and the relationship among them are discussed by lattice approach degrees. The eight water masses may be summed up into three types: the type of runoff-diluted water(F), the type of shallow -modified water (M,WS, S and SU) and the type of oceanic-deep water (U, UI and I ).