KSS31M型海洋重力仪在动、静态条件下观测到的读数变化及分析

The fixed points gravity data measurment used by KSS31M and data analysis

2002年中国科学院海洋研究所从德国引进了KSS31M型海洋重力仪.为对该重力仪的工作性能有详细的了解,分别在德国重力仪生产厂实验室、中国科学院海洋研究所重力仪实验室进行了静态的定点观测,将重力仪安装在考察船上在黄埔江渔政码头等地进行了动态条件下的定点观测.动、静态的定点观测发现了多种规律性的重力仪读数变化,分析认为这些规律性的读数变化分别是重力仪的随机振荡、月潮的重力效应、海潮的重力效应和重力仪的线性漂移.它们各自有着不同的变化规律,并在海洋重力观测时总是同时存在.重力仪的随机振荡是重力仪自身固有的,其振荡幅度随外界条件的变化而变化,一般为0.04mGal～0.5mGal,周期为2～5min不等.在德国的重力仪厂家实验室和中国科学院海洋研究所重力实验室中观测到了月潮引起的重力变化,其变化幅度为0.2mGal.月潮引起的重力变化和海潮引起的重力变化同步,但相位相反.本文指出,仪器的月漂往往很难精确判定,本文用多种方法计算得到的仪器月漂在1.2mGal到2.3mGal之间.

To evaluate the performance of the newly developed KSS31M marine gravity meter, fixed points gravity data measurement was conducted in gravity lab of the German Gravity Meter Company and gravity lab of IOCAS and also on the research vessel at harbor of Huangpu River. Several kinds of gravity changes were recorded during the measurement, they are namely instrument random oscillation, moon tide gravity change and sea tide gravity change and drift. Each of the kinds of the gravity change has its own regulation but exits at the same time during the marine gravity measurement. The instrument random oscillation is an intrinsic property of the KSS31M marine gravity meter and does not indicate the real gravity change of the measured point, its amplitude can be 0.04mGal in the lab and 0.5mGal on the research vessel, with a period as short as 2～5 minutes. The moon tide gravity change was clearly detected during the lab measurement. As comparing to the sea tide gravity change, the moon tide gravity change has the same period but opposite phase with sea tide gravity change. The amplitude of the moon tide gravity change is about 0.2mGal. The paper points out that it is not easy to give an accurate drift data of the marine gravity meter. Several methods were used to determine the drift of the KSS31M and the result shows from 1.2mGal to 2.3mGal per month.