浅海海洋盐度、温度和深度调查的精确度与海水密度计算的关系

一、本文目的海水密度系海水的盐度、温度和压力的连续函数,而在海水的压力每增加1分巴值深度几增加1米的极近似情况下,海水密度即系海水的盐度、温度和深度的连续函数。在必须精确获知海水密度值的要求下,海水的密度是藉它与盐度、温度和压力三者的函数关系计算而得的。为了要使计算所得的海水密度值有一定的精确度,所以海洋盐度、温度和深度调查的精确度就必须有一定的要求。由於中国海皆系浅海,所以本文仅就浅海海洋盐度、温度和深度调查的精确度与海水密度计算的关系加以论述。

ON THE ACCURACY IN THE DETERMINATION OF THE SALINITY,TEMPERATURE AND DEPTH OF SEA WATER IN RELATION TO THE CALCULATION OF ITS DENSITY IN SHALLOW SEA HYDROGRAPHICAL SURVEY

Since the density of sea water P_s,Θ,ρ is a continuous function of its salinity S （‰）, temperature Θ（℃） and pressure p（db.）, we may, after suitable substitution, differentiate the following formula to obtain the accuracy δa as follows: where In order to obtain the accuracy of the specific volume of sea water to the required order of magnitude 1×10^-5, or that of the calculation of density to the order of magnitude 1×10^-3%+, we.may, on substituting （3）, （4） and （5） in （2）, obtain the accuracy of salinity δs, of temperature δΘ and of depth δp when the temperature and depth, the salinity and depth, and the salinity and temperature are to be considered as constants respectively. For the purpose of China Sea hydrographical survey, we choose for the range of salinity, 23.50‰ to 34.33‰, for that of temperature, 5.00℃ to 33.00℃, and for that of depth, 0 to 100 decibars. The results may be summarized as follows: 1. Irrespective of the temperature value, the accuracy required for salinity determination must be less than or equal to±0.013‰, that is, less than or equal to±0.01‰. 2. As the salinity is to be considered as constant, the accuracy required for temperature determination increases with the raise of temperature; in other words, the accuracy required for temperature determination in shallow sea hydrographic survey is increased in the upper layer and decreased in the lower layerfor the former, ±0.03℃ and for the latter, ±0.10℃. 3. When the salinity is different but the temperature is the same, the accuracy of temperature determination required, particularly in the case of lower temperature, increases with the increase of salinity. Thus, the accuracy of temperature determination required is increased in places of lower salinity than in places of higher salinity; this fact is particularly important for shallow sea hydrographical survey. 4. For all the salinity and temperature values, the accuracy required for depth determination is the same, namely 2.2m.