﻿ 青藏高原大尺度地表流体的重力效应特征分析
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 大地测量与地球动力学  2020, Vol. 40 Issue (9): 947-951  DOI: 10.14075/j.jgg.2020.09.014

### 引用本文

ZHU Chuandong, LIU Jinzhao, CHEN Ming, et al. The Analysis on Characteristics of Gravity Effect of Large-Scale Surface Fluid in Qinghai-Tibetan Plateau[J]. Journal of Geodesy and Geodynamics, 2020, 40(9): 947-951.

### Foundation support

The Spark Program of Earthquake Technology of CEA, No. XH194204Y, XH20078Y; National Natural Science Foundation of China, No. 41704084, 41804010; National Key Research and Development Program of China, No. 2018YFC1503606; Natural Science Foundation of Tianjin Municipality, No. 17JCYBJC21600.

### 第一作者简介

ZHU Chuandong, assistant researcher, majors in satellite gravity data processing and its application, E-mail: zhuchuandong2006@sina.com.

### 文章历史

1. 中国地震局第一监测中心，天津市耐火路7号，300180

1 数据与数据处理方法 1.1 模式与再分析资料及数据处理

 $L({\theta _0}, {\lambda _0}, t) = \iint\limits_s {\rho (\theta , \lambda , t)h(\theta , \lambda , t)G(\psi )}{\rm{d}}s$ (1)

 $\begin{array}{l} G(\psi ) = {G^N}(\psi ) + {G^D}(\psi ) = \frac{g}{M}\sum\limits_{n = 0}^\infty {n{P_n}(\cos \psi ) + } \\ \;\;\;\;\;\;\;\;\;\;\frac{g}{M}\sum\limits_{n = 0}^\infty {\left[ { - (n + 1){k_n} + 2{h_n}} \right]{P_n}(\cos \psi )} \end{array}$ (2)

 ${g^N}({r_s}, {\theta _s}, {\lambda _s}) = G\frac{{[{d^2} + {{(R + {h_s})}^2} - {{(R + {h_p})}^2}]}}{{2{d^3}(R + {h_s})}}$ (3)

 $\begin{array}{l} {g^N}({r_s},{\theta _s},{\lambda _s}) = G\rho \Delta r\Delta \theta \Delta \lambda [{L_{000}} + \\ \;\frac{1}{{24}}({L_{200}}\Delta {r^2} + {L_{020}}\Delta {\theta ^2} + {L_{002}}\Delta {\lambda ^2})] \end{array}$ (4)

 $\rho = \frac{p}{{{R_L}T(1 + 0.608q)}}$ (5)

1.2 GRACE数据及数据处理

GRACE时变重力场模型是由CSR、GFZ和JPL三家机构提供的Level2 RL06版本GSM数据，包括2002-08~2017-06共160个月的观测数据。本文对每月的GRACE模型依次进行如下处理：替换C20[11]，扣除时间段内球谐系数的平均值，作组合滤波处理(250 km高斯滤波[12]和去相关滤波P5M11[13])。经过上述处理后，研究区域内各网格点上的重力异常时间序列可表示为：

 $\begin{array}{l} \Delta g(r, \theta , \lambda ) = \frac{{{\rm{GM}}}}{{{R^2}}}\sum\limits_{n = 0}^{{n_{\max }}} {(n - 1)} \sum\limits_{m = 0}^n {{{\overline P }_{nm}}(\cos \theta )} \cdot \\ \;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;[\Delta {C_{nm}}\cos (m\lambda ) + \Delta {S_{nm}}\sin (m\lambda )] \end{array}$ (6)

2 结果与分析 2.1 模式及再分析资料结果分析

 图 1 ECMWF Interim扣除季节项前后青藏高原重力峰对峰变化 Fig. 1 The gravity peak to peak change before and after deducting seasonal term from ECMWF Interim

 图 2 GLDAS Noah扣除季节项前后青藏高原重力峰对峰变化 Fig. 2 The gravity peak to peak change before and after deducting seasonal term from GLDAS Noah
2.2 GRACE结果分析

 图 3 GRACE扣除季节项前后青藏高原重力峰对峰变化 Fig. 3 The gravity peak to peak change before and after deducting seasonal term from GRACE

 图 4 GRACE-GLDAS Noah扣除季节项前后青藏高原重力峰对峰变化 Fig. 4 The gravity peak to peak change before and after deducting seasonal term from GRACE-GLDAS Noah

1) 观测误差。本文联合CSR、JPL和GFZ等3种卫星重力数据以及GLDAS Noah、Mosaic和CLM等3种陆面过程水文模式数据，采用经典的三角帽方法[15]评估了CSR GRACE和GLDAS Noah数据的观测误差(图 5(a)5(b))。结果表明，在青藏高原地区GLDAS Noah和CSR GRACE数据的观测误差分别介于0.3~6.3 μGal和0.7~1.8 μGal之间。

 图 5 青藏高原地区GLDAS Noah观测误差、GRACE观测误差及GRACE信号泄漏误差 Fig. 5 The observation error of GLDAS Noah, observation error of GRACE and leakage error of GRACE in Qinghai-Tibet plateau

2)GRACE构造运动影响。青藏高原在印度板块碰撞作用下会出现地壳隆升与底部增厚，地壳隆升和底部增厚速率分别取1.4 mm/a和3.9 cm/a[16]，地幔和地壳的平均密度分别取2.8 g/cm3和3.4 g/cm3，据此估算构造运动对GRACE观测结果的影响为1.2 μGal/a。

3)GRACE信号泄漏误差。本文对青藏高原以外的GRACE掩膜网格数据再次经过球谐系数展开和高斯滤波处理，以此估算由于球谐系数截断和滤波处理导致的区域外部信号泄漏误差(图 5(c))。结果表明，在青藏高原地区GRACE信号泄漏误差介于0.1~13.8 μGal，影响较大的区域主要分布于青藏高原南部邻近印度等北部平原地下水信号变化较为剧烈的地区。

3 结语

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The Analysis on Characteristics of Gravity Effect of Large-Scale Surface Fluid in Qinghai-Tibetan Plateau
ZHU Chuandong1     LIU Jinzhao1     CHEN Ming1     CHEN Zhaohui1     ZHANG Pin1     ZHANG Shuangxi1
1. The First Monitoring and Application Center, CEA, 7 Naihuo Road, Tianjin 300180, China
Abstract: Based on the three-dimensional atmospheric reanalysis model, the hydrological model and GRACE satellite gravity data from 2002 to 2017, we use Green's function and the satellite gravity inversion method to analyze the gravity effect characteristics of large-scale surface fluid in Qinghai-Tibet plateau. The atmospheric gravity peak-to-peak effect before and after deducting seasonal term is between 1.9-10.7 μGal and 1.1-4.6 μGal, respectively, which shows significant seasonal characteristics. The gravity peak-to-peak effects of soil water and snow before and after deducting seasonal term is between 0.9-9.9 μGal and 0.7-8.3 μGal, respectively, which shows significant seasonal and interannual characteristics. The peak to peak change of GRACE time variable gravity field is between 4.4-24.1 μGal and 3.4-18.3 μGal before and after deducting seasonal term. Considering measurement error, tectonic movement and leakage error, the significant seasonal and interannual change of GRACE gravity reflects the combined effects of various surface fluids.
Key words: Qinghai-Tibet plateau; Green's function; satellite gravity inversion; surface fluid; gravity effect