# Estimation of Terrestrial Water Storage Variations in Sichuan-Yunnan Region from GPS Observations Using Independent Component Analysis

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## Abstract

**:**

## 1. Introduction

## 2. Data and Methods

#### 2.1. Continuous GPS Observation and Inversion Method

#### 2.2. Inversion Method Based on ICA

_{ICk}is the product of ICk and the corresponding spatial response. A smaller ratio value implies a more significant contribution for the corresponding IC [28], and the ICs are reordered in ascending order [40]. The top six ICs are shown in Figure 4a and the ratio values of the GPS

_{ICs}are shown in Figure 4b. We found IC1 contributes most for the GPS coordinate time series.

_{IC1}, as shown in Figure 5. The averaged hydrological loading displacement is consistent with GPS

_{IC1}in terms of its amplitude and phase, and the correlation coefficient is 0.78. The term GPS

_{IC1}is therefore thought to represent hydrological deformation, and GPS

_{IC1}is then used in the subsequent inversion step.

#### 2.3. GRACE Measurements and GLDAS Hydrological Models

## 3. Inversion Results and Discussion

#### 3.1. Estimated TWS Variations in the Sichuan-Yunnan Region Using Different Methods

#### 3.2. Northwestern Sichuan-Yunnan Region

#### 3.3. Discussion

## 4. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 1.**Study area map. The red triangles are the GPS sites use in the inversion calculation in the Sichuan-Yunnan region. The background colors show the surface topography.

**Figure 2.**The templates of Laplacian operator: (

**a**) is the template for the internal grids; (

**b**,

**c**) are for the boundary grids.

**Figure 3.**Trade-off curve between roughness and misfit. Both the roughness and misfit have been normalized.

**Figure 4.**(

**a**) The top six ICs extracted from vertical GPS coordinate time series; (

**b**) the ratio value of each displacement GPS

_{ICs}.

**Figure 5.**The comparison between modeled daily land water storage loading (LWS) displacement (http://massloading.net/, accessed on 16 November 2021) and GPS

_{IC1}. For LWS, we use the GEOS-FPIT model developed by the Global Modeling and Assimilation Office at NASA Goddard Space Flight Center.

**Figure 7.**Monthly variations (2011) of the TWS in Sichuan-Yunnan estimated by GPS after removing the ATML and NTOL.

**Figure 10.**TWS variations results obtained using different methods. (

**a**) Monthly variations of the TWS grid value in Sichuan-Yunnan from different methods; (

**b**) peak-to-peak values (September minus March) of TWS for different methods.

**Figure 11.**TWS variations in northwestern Sichuan-Yunnan and the entire region from 2011 to 2016. The averaged grid data of monthly TWS variations in northwestern Sichuan-Yunnan (* mark) and in the entire region.

**Figure 12.**Averaged (

**a**) NTOL and (

**b**) ATML series and the RMS values of these two loading displacements for each GPS sites.

**Table 1.**Comparisons between the estimated TWS variations in northwestern Sichuan-Yunnan and the entire region for the different methods.

Methods | Annual Amplitude | ||
---|---|---|---|

${\mathit{A}}_{1}/\mathbf{mm}$ | ${\mathit{A}}_{2}/\mathbf{mm}$ | $\mathit{r}$ | |

GPS(ICA) | 91.0 | 118.9 | 30.7% |

GPS | 115.4 | 173.6 | 50.4% |

GRACE | 92.2 | 64.5 | −30.0% |

GLDAS | 53.8 | 52.2 | 3.0% |

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**MDPI and ACS Style**

Liu, B.; Yu, W.; Dai, W.; Xing, X.; Kuang, C.
Estimation of Terrestrial Water Storage Variations in Sichuan-Yunnan Region from GPS Observations Using Independent Component Analysis. *Remote Sens.* **2022**, *14*, 282.
https://doi.org/10.3390/rs14020282

**AMA Style**

Liu B, Yu W, Dai W, Xing X, Kuang C.
Estimation of Terrestrial Water Storage Variations in Sichuan-Yunnan Region from GPS Observations Using Independent Component Analysis. *Remote Sensing*. 2022; 14(2):282.
https://doi.org/10.3390/rs14020282

**Chicago/Turabian Style**

Liu, Bin, Wenkun Yu, Wujiao Dai, Xuemin Xing, and Cuilin Kuang.
2022. "Estimation of Terrestrial Water Storage Variations in Sichuan-Yunnan Region from GPS Observations Using Independent Component Analysis" *Remote Sensing* 14, no. 2: 282.
https://doi.org/10.3390/rs14020282