A new question for the polar motion. What is the origin of phase delay in the gravity response?

极移的新问题。

• 批准号: 11640420
• 负责人: SATO Tadahiro
• 金额: $ 1.66万
• 依托单位: National Astronomical Observatory
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640420/
• 关键词: Gravity changes due to polar motion; superconducting gravimeter; GGP-Japan Network; sea surface height variation; satellite altimeter; general circulation model of the ocean; thermal steric variation; 極運動; 重力応答; 超伝導重量計; 年周動力変化; 海面変動; ステリック効果 /

In order to clarify the origin of the phase delay shown in the previous analysis for the polar motion using the superconducting gravimeter data (Sato et al., 1997), the annual gravity changes observed Superconducting Gravimeters (SGs) are examined in relation to Sea Surface Height (SSH) variations. Two SSH data sets from the POCM (Parallel Ocean Climate Model, Stammer et al., 1996) and the TOPEX/POSEIDON (T/P) altimeter were compared. In order to compute the gravity changes due to SSH variations, we firstly estimated the thermal steric coefficient using the Sea Surface Temperature (SST), and we obtained a value of 0.60E-2 m/degC averaged over the central parts of the Pacific and Atlantic oceans. The annual gravity change predicted by considering four effects of the solid tide, ocean tide, polar motion and SSH variations with the observations at the three sites (i.e. Esashi in Japan, Canberra in Australia and Syowa Station in Antarctica). The results of the comparison indicate that the predictions well agree with the observations. Thus, they agree each other within 20% in amplitude (i.e. within 0.2 micro Gaps, where 1 micro Gal=1.E-8 ms^<-2>) and 20 deg in phase at each observation site. We have also tested other values of the steric coefficient, i.e. 0.0E-2 m/degC and 1.0xE-2 m/degC, but we find that the fit to gravity observations made at the mid latitudes is clearly better at 0.60E-2 m/degC.It is noted that our gravity observations point to a value of steric coefficient similar to that independently determined from the relationship between the SSH and SST data. The results obtained here may suggest that the gravity observation can be used to monitor the mass changes in the oceans. This is important to study the coupling mechanism between the Earth's fluid parts and solid parts and to investigate the response of the Earth's system to the polar motion.

为了澄清先前使用超导重力计数据（Sato等人，1997）对极移的分析中显示的相位延迟的起源，检查了超导重力计（SG）观测到的年度重力变化与海面高度（SSH）变化的关系。对来自 POCM（平行海洋气候模型，Stammer 等，1996）和 TOPEX/POSEIDON (T/P) 高度计的两个 SSH 数据集进行了比较。为了计算由于 SSH 变化引起的重力变化，我们首先使用海面温度 (SST) 估算热空间系数，并获得太平洋和大西洋中部地区的平均热空间系数为 0.60E-2 m/degC。通过考虑固体潮、海潮、极移和SSH变化四种影响以及日本江差、澳大利亚堪培拉和南极洲昭和站观测的年重力变化预测。比较结果表明预测与观察结果非常吻合。因此，它们在每个观察点处的幅度在20％以内(即在0.2微间隙内，其中1微Gal＝1.E-8ms^-2>)和相位在20度内彼此一致。我们还测试了其他空间系数值，即0.0E-2 m/degC和1.0xE-2 m/degC，但我们发现0.60E-2 m/degC与中纬度重力观测的拟合明显更好。值得注意的是，我们的重力观测指向的空间系数值类似于根据SSH和SST数据之间的关系独立确定的空间系数值。这里获得的结果可能表明重力观测可用于监测海洋中的质量变化。这对于研究地球流体部分和固体部分之间的耦合机制以及研究地球系统对极移的响应具有重要意义。

项目成果

佐藤忠弘,竹本修三,今西祐一: "GGPとGGP-Japanネットワーク"月刊地球. 21・18. 474-477 (1999)

佐藤忠宏、竹本修三、今西雄一：《GGP 和 GGP-日本网络》月刊 21・18（1999 年）。

Sato,T., et al.: "On the observed gravity variation and the effect of sea surface height variations"Physics of the Earth and Planetary Interiors. 123・1. 45-63 (2001)

佐藤 T. 等：“观测​​到的重力变化和海面高度变化的影响”《地球与行星内部物理学》123・1（2001 年）。

佐藤忠弘: "地球潮汐と章動"月刊地球 総特集 超伝導等重力計ネットワーク. Vol. 242 No.8. 516-519 (1999)

Tadahiro Sato：“地球潮汐和章动”月刊地球专题超导等重力计网络第 242 卷第 516-519 期（1999 年）。