中国近海温跃层判定方法的研究

A study of thermocline calculations in the China Sea

根据东海以及南海东北部多组资料,探讨了拟阶梯函数法和垂向梯度法在浅海区(水深<200m)、陆架坡折海域(水深在200m左右)和深水开阔海区(水深>200m)的应用情况,分析了温跃层在陆架坡折海域的水平衔接问题。对比分析表明:在浅海区,两种方法结果比较一致,特别对某些垂直温度梯度较弱的曲线,拟阶梯函数法和实际水文廓线符合更好。陆架坡折海域,垂向梯度法对于温度梯度相对较弱的跃层刻画不好,而拟阶梯函数法可以对较弱温跃层进行判定,与实际垂直水文结构一致。深水开阔区域,垂向梯度法所得温跃层特征量与实际符合较好,而拟阶梯函数法获得的温跃层强度偏大。因此,对本研究海域来说,当水深≤200m时,采用拟阶梯函数法,当水深>200m时采用垂向梯度法,最小判定标准统一采用0.05℃/m,可以有效避免陆架坡折海域的水平不连续问题,与实际水文廓线符合较好。

Based on observations data in the northeastern East China Sea and South China Sea, the applications of the vertical gradient method and the quasi-step function approximation method in shallow waters （depth 〈200 m）, the shelf break waters （about 200 m） and open seas （depth〉200 m） were analyzed to solve the horizontal discontinuity of the thermocline calculations in the shelf break waters. The results show that. in shallow waters, the results of these two methods are consistent, particularly the results are more consistent with the actual hydrological profile for some vertical temperature gradient weaker curve using quasi-step function approximation method. In the shelf break waters, quasi-step function approximation method pictures the thermocline better because the vertical temperature gradient is weaker. In open seas, the thermocline calculated by the vertical gradient method is more approaching the actual hydrological profile; however the gradient is too larger using quasi-step function approximation method. Therefore, the quasi-step function approximation method is used in the waters where the depth ≤ 200 m, and the vertical gradient method is used in the waters where the depth 〉200 m with the uniform minimum criteria （0.05℃/m）, avoiding the horizontal discontinuity of the thermocline.