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20 pages, 8571 KiB

Open AccessArticle

Spatial and Temporal Characteristics of NDVI in the Weihe River Basin and Its Correlation with Terrestrial Water Storage

by Zhenzhen Wei and Xiaoyun Wan

Remote Sens. 2022, 14(21), 5532; https://doi.org/10.3390/rs14215532 - 02 Nov 2022

Cited by 6 | Viewed by 1617

Abstract

The Weihe River Basin (WRB) of China is located in an arid and water-scarce semi-arid region with a fragile ecological environment, and it is meaningful to study the spatial and temporal changes in vegetation and terrestrial water storage changes in a small-scale inland [...] Read more.

The Weihe River Basin (WRB) of China is located in an arid and water-scarce semi-arid region with a fragile ecological environment, and it is meaningful to study the spatial and temporal changes in vegetation and terrestrial water storage changes in a small-scale inland basin. This study uses normalized difference vegetation index (NDVI) data and Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) time-variable gravity field models to derive changes in vegetation cover and water storage in the WRB from 2002 to 2020. Firstly, taking NDVI as the breakthrough point, the temporal and spatial characteristics of vegetation were analyzed by trend analysis method and F-test. Then, GRACE and GRACE-FO were used to derive water storage variations. Finally, the correlation between NDVI and water storage variations is discussed using the Pearson correlation analysis. The results show that the overall trend of NDVI is increasing, and the increasing trend is more evident before 2014, and after that, there is a significant fluctuation. The spatial distribution shows a large spatial variability, but the growing area still accounts for the majority, and the change varies by vegetation type, among which the cultivated vegetation is more influential. The overall change in terrestrial water storage showed a decreasing trend of −0.09 cm/yr, and also reflected a solid intra-annual regular cycle, i.e., reaching a trough from October to November and a peak from May to June each year. The correlation is 0.6 on the time scale, and there was a 3-month lag between NDVI and TWS. On the spatial scale, the percentage of areas with a negative correlation was about 95.4%, probably due to increased water consumption and evapotranspiration. The study’s results can help to understand the relationship between vegetation and water storage in the WRB and provide scientific support for local environmental management. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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18 pages, 4557 KiB

Open AccessArticle

Understanding Water Level Changes in the Great Lakes by an ICA-Based Merging of Multi-Mission Altimetry Measurements

by Wei Chen, C. K. Shum, Ehsan Forootan, Wei Feng, Min Zhong, Yuanyuan Jia, Wenhao Li, Junyi Guo, Changqing Wang, Quanguo Li and Lei Liang

Remote Sens. 2022, 14(20), 5194; https://doi.org/10.3390/rs14205194 - 17 Oct 2022

Cited by 2 | Viewed by 1946

Abstract

Accurately monitoring spatio-temporal changes in lake water levels is important for studying the impacts of climate change on freshwater resources, and for predicting natural hazards. In this study, we applied multi-mission radar satellite altimetry data from the Laurentian Great Lakes, North America to [...] Read more.

Accurately monitoring spatio-temporal changes in lake water levels is important for studying the impacts of climate change on freshwater resources, and for predicting natural hazards. In this study, we applied multi-mission radar satellite altimetry data from the Laurentian Great Lakes, North America to optimally reconstruct multi-decadal lake-wide spatio-temporal changes of water level. We used the results to study physical processes such as teleconnections of El Niño and southern oscillation (ENSO) episodes over approximately the past three-and-a-half decades (1985–2018). First, we assessed three reconstruction methods, namely the standard empirical orthogonal function (EOF), complex EOF (CEOF), and complex independent component analysis (CICA), to model the lake-wide changes of water level. The performance of these techniques was evaluated using in-situ gauge data, after correcting the Glacial Isostatic Adjustment (GIA) process using a contemporary GIA forward model. While altimeter-measured water level was much less affected by GIA, the averaged gauge-measured water level was found to have increased up to 14 cm over the three decades. Our results indicate that the CICA-reconstructed 35-year lake level was more accurate than the other two techniques. The correlation coefficients between the CICA reconstruction and the in situ water-level data were 0.96, 0.99, 0.97, 0.97, and 0.95, for Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario, respectively; ~7% higher than the original altimetry data. The root mean squares of errors (RMSE) were 6.07 cm, 4.89 cm, 9.27 cm, 7.71 cm, and 9.88 cm, respectively, for each of the lakes, and ~44% less than differencing with the original altimetry data. Furthermore, the CICA results indicated that the water-level changes in the Great Lakes were significantly correlated with ENSO, with correlation coefficients of 0.5–0.8. The lake levels were ~25 cm higher (~30 cm lower) than normal during EI Niño (La Niña) events. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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18 pages, 3958 KiB

Open AccessArticle

Evaluation of NeQuick2 Model over Mid-Latitudes of Northern Hemisphere

by Lingxuan Wang, Erhu Wei, Si Xiong, Tengxu Zhang and Ziyu Shen

Remote Sens. 2022, 14(16), 4124; https://doi.org/10.3390/rs14164124 - 22 Aug 2022

Cited by 3 | Viewed by 1772

Abstract

NeQuick2 is a three-dimensional ionospheric electron density empirical model that uses numerical integration to calculate the total electron content along any line-of-sight (LOS). As one of the most commonly used three-dimensional ionospheric models, it is necessary to objectively evaluate the accuracy and stability [...] Read more.

NeQuick2 is a three-dimensional ionospheric electron density empirical model that uses numerical integration to calculate the total electron content along any line-of-sight (LOS). As one of the most commonly used three-dimensional ionospheric models, it is necessary to objectively evaluate the accuracy and stability of NeQuick2 over a long period, especially over the mid-latitudes of the northern hemisphere where most of the ground-based GNSS stations are distributed. Therefore, different methods are used in this study to evaluate the accuracy of the NeQuick2 model from 2008 to 2021, including comparison with the International Global Navigation Satellite System Global Ionosphere Maps (IGSG), Jason2 Vertical Electron content (VTEC), and self-consistent evaluation. The comparison with IGSG shows that the standard deviation (STD) value is about 2.59 TECU. The accuracy of the IGSG and NeQuick2 model over ocean regions shows that the bias of IGSG is more significant than that of the NeQuick2 model. The mean STD value is 2.09 TECU for IGSG, and the corresponding value is 3.18 TECU for the NeQuick2 model, which is about 50% worse than IGSG. The dSTEC assessment results indicate that the variation in bias for IGSG is more stable than that of the NeQuick2 model. The mean STD value is 0.86 and 1.52 TECU for IGSG and NeQuick2 model, respectively. The conclusion could be made that NeQuick2 model represents the average ionosphere electron content and its accuracy fluctuates with solar conditions. Compared with the IGSG, the NeQuick2 model always underestimates TEC value, especially in low solar activity periods and compared with Jason2, the TEC values obtained by NeQuick2 model are overestimated, but the degree of overestimation is smaller than that of IGSG. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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26 pages, 6926 KiB

Open AccessArticle

Natural- and Human-Induced Influences on Terrestrial Water Storage Change in Sichuan, Southwest China from 2003 to 2020

by Lilu Cui, Chengkang Zhu, Yunlong Wu, Chaolong Yao, Xiaolong Wang, Jiachun An and Pengzhi Wei

Remote Sens. 2022, 14(6), 1369; https://doi.org/10.3390/rs14061369 - 11 Mar 2022

Cited by 10 | Viewed by 2360

Abstract

A quantitative understanding of changes in water resources is crucial for local governments to enable timely decision-making to maintain water security. Here, we quantified natural-and human-induced influences on the terrestrial water storage change (TWSC) in Sichuan, Southwest China, with intensive water consumption and [...] Read more.

A quantitative understanding of changes in water resources is crucial for local governments to enable timely decision-making to maintain water security. Here, we quantified natural-and human-induced influences on the terrestrial water storage change (TWSC) in Sichuan, Southwest China, with intensive water consumption and climate variability, based on the data from the Gravity Recovery and Climate Experiment (GRACE) and its Follow-on (GRACE-FO) during 2003–2020. We combined the TWSC estimates derived from six GRACE/GRACE-FO solutions based on the uncertainties of each solution estimated from the generalized three-cornered hat method. Metrics of correlation coefficient and contribution rate (CR) were used to evaluate the influence of precipitation, evapotranspiration, runoff, reservoir storage, and total water consumption on TWSC in the entire region and its five economic regions. The results showed that a significant improvement in the fused TWSC was found compared to those derived from a single model. The increase in regional water storage with a rate of 3.83 ± 0.54 mm/a was more influenced by natural factors (CR was 53.17%) compared to human influence (CR was 46.83%). Among the factors, the contribution of reservoir storage was the largest (CR was 42.32%) due to the rapid increase in hydropower stations, followed by precipitation (CR was 35.16%), evapotranspiration (CR was 15.86%), total water consumption (CR was 4.51%), and runoff (CR was 2.15%). Among the five economic regions, natural influence on Chengdu Plain was the highest (CR was 48.21%), while human influence in Northwest Sichuan was the largest (CR was 61.37%). The highest CR of reservoir storage to TWSC was in Northwest Sichuan (61.11%), while the highest CRs of precipitation (35.16%) and evapotranspiration (15.86%) were both in PanXi region. The results suggest that TWSC in Sichuan is affected by natural factors and intense human activities, in particular, the effect of reservoir storage on TWSC is very significant. Our study results can provide beneficial help for the management and assessment of regional water resources. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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19 pages, 26379 KiB

Open AccessArticle

Prospects for Reconstructing Daily Runoff from Individual Upstream Remotely-Sensed Climatic Variables

by Hok Sum Fok, Yutong Chen and Linghao Zhou

Remote Sens. 2022, 14(4), 999; https://doi.org/10.3390/rs14040999 - 18 Feb 2022

Viewed by 1314

Abstract

Basin water supply, planning, and its allocation requires runoff measurements near an estuary mouth. However, insufficient financial budget results in no further runoff measurements at critical in situ stations. This has recently promoted the runoff reconstruction via regression between the runoff and nearby [...] Read more.

Basin water supply, planning, and its allocation requires runoff measurements near an estuary mouth. However, insufficient financial budget results in no further runoff measurements at critical in situ stations. This has recently promoted the runoff reconstruction via regression between the runoff and nearby remotely-sensed variables on a monthly scale. Nonetheless, reconstructing daily runoff from individual basin-upstream remotely-sensed climatic variables is yet to be explored. This study investigates standardized data regression approach to reconstruct daily runoff from the individual remotely-sensed climatic variables at the Mekong Basin’s upstream. Compared to simple linear regression, the daily runoff reconstructed and forecasted from the presented approach were improved by at most 5% and 10%, respectively. Reconstructed runoffs using neural network models yielded ~0.5% further improvement. The improvement was largely a function of the reduced discrepancy during dry and wet seasons. The best forecasted runoff obtained from the basin-upstream standardized precipitation index, yielded the lowest normalized root-mean-square error of 0.093. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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19 pages, 7840 KiB

Open AccessArticle

Estimation of Evapotranspiration in the Yellow River Basin from 2002 to 2020 Based on GRACE and GRACE Follow-On Observations

by Wei Qu, Zehui Jin, Qin Zhang, Yuan Gao, Pufang Zhang and Peinan Chen

Remote Sens. 2022, 14(3), 730; https://doi.org/10.3390/rs14030730 - 04 Feb 2022

Cited by 10 | Viewed by 2378

Abstract

Evapotranspiration (ET) plays an important role in the hydrological cycle of river basins. Studying ET in the Yellow River Basin (YRB) is greatly significant for the scientific management of water resources. Here, we made full use of the advantages of the Gravity Recovery [...] Read more.

Evapotranspiration (ET) plays an important role in the hydrological cycle of river basins. Studying ET in the Yellow River Basin (YRB) is greatly significant for the scientific management of water resources. Here, we made full use of the advantages of the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) gravity satellites for monitoring large-scale hydrological changes to calculate the terrestrial water storage anomaly (TWSA) and terrestrial water flux in the YRB from May 2002 to June 2020. Furthermore, combined with terrestrial water flux, precipitation, and runoff data, ET in the YRB was calculated based on the water budget equation and then compared with other traditional ET products. The mutation of annual mean ET was identified by the Mann–Kendall trend test method, and the seasonal and interannual variations of ET were explored. ET was closely related to precipitation. Annual mean ET exhibited a sudden change in 2011, with an insignificant downward trend from 2003 to 2010, followed by an increasing trend from 2011 to 2019, particularly after 2016. Compared with the traditional ET monitoring methods and products, the ET estimated by GRACE/GRACE-FO observations provides a new way to effectively obtain continuous and reliable ET data in a wide range of river basins. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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25 pages, 62574 KiB

Open AccessArticle

The Influence of Climate Change on Forest Fires in Yunnan Province, Southwest China Detected by GRACE Satellites

by Lilu Cui, Chuanjiang Luo, Chaolong Yao, Zhengbo Zou, Guiju Wu, Qiong Li and Xiaolong Wang

Remote Sens. 2022, 14(3), 712; https://doi.org/10.3390/rs14030712 - 02 Feb 2022

Cited by 21 | Viewed by 3465

Abstract

Yunnan province in China has rich forest resources but high forest fire frequency. Therefore, a better understanding of the relationship between climate change and forest fires in this region is important for forest fire prevention. This study used the Gravity Recovery and Climate [...] Read more.

Yunnan province in China has rich forest resources but high forest fire frequency. Therefore, a better understanding of the relationship between climate change and forest fires in this region is important for forest fire prevention. This study used the Gravity Recovery and Climate Experiment (GRACE) terrestrial water storage change (TWSC) data to analyze the influence of climate change on forest fires in the region during 2003–2016. To improve the accuracy and reliability of GRACE TWSC data, we used the generalized three-cornered hat (GTCH) and the least square method to fuse TWSC data from six GRACE solutions. The spatiotemporal variation of forest fires during 2003–2016 was investigated using burned area data. Then, the relationship between burned area and hydrological and climatic factors was analyzed. The results indicate that more than 90% of burned areas are located in northwestern and southern Yunnan (NW and S). On the seasonal scale, forest fires are mainly concentrated in January–April (dry season) and the burned area is negatively correlated with precipitation (correlation coefficient r = −0.83 (NW) and −0.51 (S)), relative humidity (r = −0.79 (NW) and −0.92 (S)), GRACE TWSC (r = −0.57 (NW) and −0.73 (S)) and evapotranspiration (r = −0.90 (NW) and −0.35 (S)). However, the burned area has no significant correlations with the above four factors on the interannual scale. The composite analysis suggests that the extreme climate affects precipitation, evapotranspiration and TWSC in this region, thereby changing water storage of the air in this region, leading to the formation of an environment prone to forest fires. Such conditions have led to an increase in the burned area in the above region. We also found that the difference between TWSC in high- and low-fire years is much greater than the precipitation in the same period. The above results show that GRACE satellites can detect the influence of climate change on forest fires in Yunnan province. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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18 pages, 6308 KiB

Open AccessArticle

High-Precision Potential Evapotranspiration Model Using GNSS Observation

by Qingzhi Zhao, Tingting Sun, Tengxu Zhang, Lin He, Zhiyi Zhang, Ziyu Shen and Si Xiong

Remote Sens. 2021, 13(23), 4848; https://doi.org/10.3390/rs13234848 - 29 Nov 2021

Cited by 7 | Viewed by 1635

Abstract

Potential evapotranspiration (PET) can reflect the characteristics of drought change in different time scales and is the key parameter for calculating the standardized precipitation evapotranspiration index (SPEI). The Thornthwaite (TH) and Penman–Monteith (PM) models are generally used to calculate PET, but the precision [...] Read more.

Potential evapotranspiration (PET) can reflect the characteristics of drought change in different time scales and is the key parameter for calculating the standardized precipitation evapotranspiration index (SPEI). The Thornthwaite (TH) and Penman–Monteith (PM) models are generally used to calculate PET, but the precision of PET derived from the TH model is poor, and a large number of meteorological parameters are required to evaluate the PM model. To obtain high-precision PET with fewer meteorological parameters, a high-precision PET (HPET) model is proposed to calculate PET by introducing precipitable water vapor (PWV) from Global Navigation Satellite System (GNSS) observation. The PET difference (DPET) between TH- and PM-derived PET was calculated first. Then, the relationship between the DPET and GNSS-derived PWV/temperature was analysed, and a piecewise linear regression model was calculated to fit the DPET. Finally, the HPET model was established by adding the fitted DPET to the initial PET derived from the TH model. The Loess Plateau (LP) was selected as the experiment area, and the statistical results show the satisfactory performance of the proposed HPET model. The averaged root mean square (RMS) of the HPET model over the whole LP area is 8.00 mm, whereas the values for the TH and revised TH (RTH) models are 34.25 and 12.55 mm, respectively, when the PM-derived PET is regarded as the reference. Compared with the TH and RTH models, the average improvement rates of the HPET model over the whole LP area are 77.5 and 40.5%, respectively. In addition, the HPET-derived SPEI is better than that of the TH and RTH models at different month scales, with average improvement rates of 49.8 and 23.1%, respectively, over the whole LP area. Such results show the superiority of the proposed HPET model to the existing PET models. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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20 pages, 16525 KiB

Open AccessArticle

Variations in Stratospheric Gravity Waves Derived from Temperature Observations of Multi-GNSS Radio Occultation Missions

by Jia Luo, Jialiang Hou and Xiaohua Xu

Remote Sens. 2021, 13(23), 4835; https://doi.org/10.3390/rs13234835 - 28 Nov 2021

Cited by 4 | Viewed by 1749

Abstract

The spatial–temporal distribution of the global gravity wave (GW) potential energy (Ep) at the lower stratosphere of 20–35 km is studied using the dry temperature profiles from multi- Global Navigation Satellite System (GNSS) radio occultation (RO) missions, including CHAMP, COSMIC, GRACE, and METOP-A/B/C, [...] Read more.

The spatial–temporal distribution of the global gravity wave (GW) potential energy (Ep) at the lower stratosphere of 20–35 km is studied using the dry temperature profiles from multi- Global Navigation Satellite System (GNSS) radio occultation (RO) missions, including CHAMP, COSMIC, GRACE, and METOP-A/B/C, during the 14 years from 2007 to 2020, based on which the linear trends of the GW Ep and the responses of GW Ep to solar activity, quasi biennial oscillation (QBO), and El Niño-Southern Oscillation (ENSO) are analyzed using the multivariate linear regression (MLR) method. It is found that the signs and the magnitudes of the trends of GW Ep during each month vary at different altitude ranges and over different latitudes. At 25–35 km of the middle and high latitudes, GW Ep values generally show significant negative trends in almost all months, and the values of the negative trends become smaller in the regions closer to the poles. The distribution of the deseasonalized trends in the monthly zonal-mean GW Ep demonstrates that the GW activities are generally declining from 2007 to 2020 over the globe. The responses of GW Ep to solar activity are found to be mostly positive at 20–35 km over the globe, and the comparison between the distribution pattern of the deseasonalized trends in the GW activities and that of the responses of GWs to solar activity indicates that the sharp decline in solar activity from 2015 to 2017 might contribute to the overall attenuation of gravity wave activity during the 14 years. Significant negative responses of GW Ep to QBO are found at 30–35 km over 30° S–25° N, and the negative responses extend to the mid and high latitudes in the southern hemisphere at 20–30 km. The responses of GW Ep to QBO change to be significantly positive at 20–30 km over 15° S–15° N, which demonstrates that the zonal wind field should be the main factor affecting the GW activities at 20–30 km over the tropics. The responses of GW Ep at 20–35 km to ENSO are found to be positive over 15° S–15° N, while at 30–35 km over 15° N–30° N and at 20–35 km near 50° N, significant negative responses of GW Ep to ENSO exist. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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19 pages, 7734 KiB

Open AccessArticle

GIS-Based Groundwater Potential Assessment in Varied Topographic Areas of Mianyang City, Southwestern China, Using AHP

by Qing Zhang, Shuangxi Zhang, Yu Zhang, Mengkui Li, Yu Wei, Meng Chen, Zeyi Zhang and Zhouqing Dai

Remote Sens. 2021, 13(22), 4684; https://doi.org/10.3390/rs13224684 - 19 Nov 2021

Cited by 7 | Viewed by 3061

Abstract

Mianyang City is located in the varied topographic areas of Sichuan Province in southwestern China and is characterized by a complex geological background. This area is prone to disasters and its varied topography is inconvenient for emergency water storage and supply. Groundwater is [...] Read more.

Mianyang City is located in the varied topographic areas of Sichuan Province in southwestern China and is characterized by a complex geological background. This area is prone to disasters and its varied topography is inconvenient for emergency water storage and supply. Groundwater is essential for alleviating the demand for water and post-disaster emergency water supply in this area. This study applied AHP to integrate remote sensing, geological and hydrological data into GIS for the assessment of groundwater potential, providing a plan for the rational exploitation of groundwater and post-disaster emergency water supply in the area. Nine factors, including the spring calibration related to groundwater, were integrated by AHP after multicollinear checks. As a result, the geology-controlled groundwater potential map was classified into five levels with equal intervals. All the results were validated using borehole data, indicating the following: the areas with yield rates of

< 1 t / d \cdot m

, 1–20

t / d \cdot m

, and 20–400

t / d \cdot m

accounted for 2.66%, 36.1%, and 39.62%, respectively, whereas the areas with yield rates of 400–4000

t / d \cdot m

and

> 4000 t / d \cdot m

accounted for only 20.88% and 0.75% of the overall area. The flexibility of this quick and efficient method enables its application in other regions with a similar geological background. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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18 pages, 6076 KiB

Open AccessArticle

An Investigation of Extreme Weather Impact on Precipitable Water Vapor and Vegetation Growth—A Case Study in Zhejiang China

by Si Xiong, Fei Guo, Qingzhi Zhao, Liangke Huang, Lin He and Tengxu Zhang

Remote Sens. 2021, 13(18), 3576; https://doi.org/10.3390/rs13183576 - 08 Sep 2021

Cited by 3 | Viewed by 1936

Abstract

Zhejiang province in China experienced an extreme climate phenomenon in August 2014 with temperature rises, sunshine duration decreases, and precipitation increases, particularly, the successive heavy rainfall events occurring from 16 to 20 August 2014 that contributed to this climate anomaly. This study investigates [...] Read more.

Zhejiang province in China experienced an extreme climate phenomenon in August 2014 with temperature rises, sunshine duration decreases, and precipitation increases, particularly, the successive heavy rainfall events occurring from 16 to 20 August 2014 that contributed to this climate anomaly. This study investigates the spatial-temporal variation characteristics of precipitable water vapor (PWV) and the normalized difference vegetation index (NDVI) associated with this phenomenon. Multiple sources of PWV values derived from the Global Positioning System (GPS), Radiosonde (RS) and European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim data are used with different spatiotemporal resolutions. The monthly averaged PWV in August 2014 exceeded the 95% percentiles of climatological value (53 mm) while the monthly averaged temperature was less than the 5% percentiles of climatological value (26.6 °C). Before the extreme precipitation, the PWV increased from the yearly averaged value of about 35 mm to more than 60 mm and gradually returned to the August climatological average of 50 mm after the precipitation ended. A large-scale atmospheric water vapor was partially conveyed by the warm wet air current of anticyclones which originated over the South China Sea (25° N, 130° E) and the Western Pacific Ocean. The monthly NDVI variation over the past 34 years (1982–2015) was investigated in this paper and the significant impact of extreme climate on vegetation growth in August 2014 was found. The extreme negative temperature anomaly and positive PWV anomaly are the major climate-driven factors affecting vegetation growth in the north and south of Zhejiang province with correlation coefficients of 0.83 and 0.72, respectively, while the extreme precipitation does not show any apparent impact on NDVI. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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23 pages, 8478 KiB

Open AccessArticle

Interactive Contribution of Indian Summer Monsoon and Western North Pacific Monsoon to Water Level and Terrestrial Water Storage in the Mekong Basin

by Taoran Shi, Hok Sum Fok and Zhongtian Ma

Remote Sens. 2021, 13(17), 3399; https://doi.org/10.3390/rs13173399 - 27 Aug 2021

Cited by 4 | Viewed by 1658 | Correction

Abstract

Water level (WL) and terrestrial water storage (TWS) are two important indicators for early alerts of hydrological extremes. Their variation is governed by precipitation under monsoon variability, in particular in the Mekong river basin, where it is affected by the interaction between the [...] Read more.

Water level (WL) and terrestrial water storage (TWS) are two important indicators for early alerts of hydrological extremes. Their variation is governed by precipitation under monsoon variability, in particular in the Mekong river basin, where it is affected by the interaction between the Indian summer monsoon (ISM) and western North Pacific monsoon (WNPM). This study aimed to quantify the contributions of two monsoons to the water levels of four hydrological stations (i.e., My Thuan, Can Tho, Chau Doc and Tan Chau) on the Mekong Delta and the terrestrial water storage of the entire Mekong River basin through relative importance analysis. Three methods—multivariate linear regression; Lindeman, Merenda and Gold (LMG); and the proportional marginal variance decomposition (PMVD) methods—were selected to quantitatively obtain the relative influence of two monsoons on water level and TWS. The results showed that, from 2010 to 2014, the proportions of the ISM impacts on the water level obtained with the three methods ranged from 55.48 to 81.35%, 50.69 to 57.55% and 55.41 to 93.64% via multivariate linear regression, LMG and PMVD, respectively. Further analysis showed that different choices of time spans could lead to different results, indicated that the corresponding proportion would be influenced by other factors, such as El Niño–Southern Oscillation (ENSO). The removal of ENSO further enlarged the relative importance of the ISM, and the mean values of the four stations were increased by 8.78%, 2.04% and 14.92%, respectively, via multivariate linear regression, LMG and PMVD. Meanwhile, based on the analysis of terrestrial water storage, it was found that the impact of the ISM on the whole Mekong River basin was dominant: the proportions of the impact of the ISM on terrestrial water storage increased to 68.79%, 54.60% and 79.43%, which rose by 11.24%, 2.96% and 19.77%, respectively, via linear regression, LMG and PMVD. The increases almost equaled the quantified proportion for the ENSO component. Overall, the novel technique of quantifying the contributions of monsoons to WL and TWS can be applied to the influence of other atmospheric factors or events on hydrological variables in different regions. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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14 pages, 7151 KiB

Open AccessTechnical Note

Quantitative Assessment of Shallow Groundwater Sustainability in North China Plain

by Hao Zhou, Min Dai, Min Wei and Zhicai Luo

Remote Sens. 2023, 15(2), 474; https://doi.org/10.3390/rs15020474 - 13 Jan 2023

Cited by 3 | Viewed by 1430

Abstract

The depletion of shallow groundwater has seriously affected the sustainable development of water resources in the North China Plain (NCP). Based on 556 well monitoring observations over a period of 13 years, we quantitatively evaluated the shallow groundwater sustainability in the NCP via [...] Read more.

The depletion of shallow groundwater has seriously affected the sustainable development of water resources in the North China Plain (NCP). Based on 556 well monitoring observations over a period of 13 years, we quantitatively evaluated the shallow groundwater sustainability in the NCP via various indices (e.g., the reliability, resilience, vulnerability, and sustainability indices), and further discussed the contribution of different drivers (including climatic and non-climatic factors). The main conclusions are summarized as follows: (1) the yearly trend of shallow groundwater shows a serious long-term deficit in the Piedmont Plain but is not significant in the East-Central Plain. (2) As for the sustainability of shallow groundwater in the NCP, the reliability is below the medium level (reliability < 0.5) in most areas and the ability of shallow aquifers to restore groundwater is very weak (resilience < 0.2), while the lack of groundwater storage in most shallow aquifers is not serious (vulnerability < 0.4). The final sustainability index (<0.1) shows the poor sustainability of most shallow aquifers in the NCP. (3) The non-climatic factor is the dominant driver of shallow groundwater depletion in the NCP when compared to the climatic factor. This result is helpful to formulate the water management policies for sustainable shallow groundwater storage in the NCP. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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2 pages, 502 KiB

Open AccessCorrection

Correction: Shi et al. Interactive Contribution of Indian Summer Monsoon and Western North Pacific Monsoon to Water Level and Terrestrial Water Storage in the Mekong Basin. Remote Sens. 2021, 13, 3399

by Taoran Shi, Hok Sum Fok and Zhongtian Ma

Remote Sens. 2023, 15(1), 49; https://doi.org/10.3390/rs15010049 - 22 Dec 2022

Viewed by 708

Abstract

In the original article [...] Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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16 pages, 12977 KiB

Open AccessTechnical Note

Characteristics of the Greenland Ice Sheet Mass Variations Revealed by GRACE/GRACE Follow-On Gravimetry

by Peisi Shang, Xiaoli Su and Zhicai Luo

Remote Sens. 2022, 14(18), 4442; https://doi.org/10.3390/rs14184442 - 06 Sep 2022

Cited by 1 | Viewed by 1375

Abstract

As a major contributor to global mean sea-level rise, the Greenland ice sheet (GrIS) and the patterns of its mass change have attracted wide attention. Based on Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow-On (GRACE-FO) gravimetry data, we computed monthly non-cumulative mass change [...] Read more.

As a major contributor to global mean sea-level rise, the Greenland ice sheet (GrIS) and the patterns of its mass change have attracted wide attention. Based on Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow-On (GRACE-FO) gravimetry data, we computed monthly non-cumulative mass change time series of the GrIS, which agree with those from the mass budget method confirming the reliability of GRACE-FO-derived mass change. Over the GrIS, mass was mainly gained in winter, followed by spring. It primarily lost mass in summer, with the percentage of summer mass loss versus the corresponding annual mass loss ranging from 61% to 96%. We report that spring mass loss has become more frequent since 2015, and autumn mass gain occurred more frequently after 2014. By separating mass gain from mass loss at the annual timescale, we find that both the mass gain and mass loss showed a slightly increasing trend during 2003–2020, which might be a response to the ongoing Arctic warming. Summer mass variations highly correlated with the summer North Atlantic Oscillation index are dominated by temperature-associated precipitation and meltwater runoff. This study suggests that long-term observations would be necessary to better understand patterns of the GrIS mass variations in future. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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16 pages, 3203 KiB

Open AccessTechnical Note

Impact of Large-Scale Ocean–Atmosphere Interactions on Interannual Water Storage Changes in the Tropics and Subtropics

by Shengnan Ni, Zhicai Luo, Jianli Chen and Jin Li

Remote Sens. 2021, 13(17), 3529; https://doi.org/10.3390/rs13173529 - 05 Sep 2021

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Abstract

Satellite observations from the Gravity Recovery and Climate Experiment (GRACE) provide unique measurements of global terrestrial water storage (TWS) changes at different spatial and temporal scales. Large-scale ocean–atmosphere interactions might have significant impacts on the global hydrological cycle, resulting in considerable influences on [...] Read more.

Satellite observations from the Gravity Recovery and Climate Experiment (GRACE) provide unique measurements of global terrestrial water storage (TWS) changes at different spatial and temporal scales. Large-scale ocean–atmosphere interactions might have significant impacts on the global hydrological cycle, resulting in considerable influences on TWS changes. Quantifying the contributions of large-scale ocean–atmosphere interactions to TWS changes would be beneficial to improving our understanding of water storage responses to climate variability. In the study, we investigate the impact of three major global ocean–atmosphere interactions—El Niño and Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Atlantic Meridional Mode (AMM) on interannual TWS changes in the tropics and subtropics, using GRACE measurements and climate indices. Based on the least square principle, these climate indices, and the corresponding Hilbert transformations along with a linear trend, annual and semi-annual terms are fitted to the TWS time series on global 1° × 1° grids. By the fitted results, we analyze the connections between interannual TWS changes and ENSO, IOD, and AMM indices, and estimate the quantitative contributions of these climate phenomena to TWS changes. The results indicate that interannual TWS changes in the tropics and subtropics are related to ENSO, IOD, and AMM climate phenomena. The contribution of each climate phenomenon to TWS changes might vary in different regions, but in most parts of the tropics and subtropics, the ENSO contribution to TWS changes is found to be more dominant than those from IOD and AMM. Full article

(This article belongs to the Special Issue Carbon, Water and Climate Monitoring Using Space Geodesy Observations)

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