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To derive shallow water bathymetry for coastal areas, a common approach is to deploy a scanning airborne bathymetric light detection and ranging (LiDAR) system or a shipborne echosounder for ground surveys. However, recent advancements in satellite remote sensing, including the Ice, Cloud and land Elevation Satellite-2 (ICESat-2) offer new tools for generating satellite derived bathymetry (SDB). The key payload onboard ICESat-2 is the Advanced Topographic Laser Altimeter System (ATLAS), a micro-pulse, photon-counting LiDAR system, simultaneously emitting six separate 532 nm beams at 10 kHz pulse rate. However, despite its high resolution, the major limitation for bathymetry is that ICESat-2 only provides along-track height profiles, leaving observation gaps between the parallel ground tracks. Merging ICESat-2 observations with optical multispectral imagery, as demonstrated herein, provides an effective solution for deriving a full scene of water depth in light of the spectral attenuation behavior. This study aims to combine ICESat-2 and Sentinel-2 optical data to derive shallow water bathymetry (depth <20 m) at six islands and reefs in the South China Sea. ICESat-2 ATL03 point clouds of georeferenced photons are first filtered to determine the seafloor elevation along the ground track. Results indicate a root-mean-square error (RMSE) of 0.26–0.61 m as compared with independent observations from an airborne LiDAR campaign. Next, three semi-empirical functions, namely the Modified Linear/Polynomial/Exponential Ratio Models with its kernel formed by the log ratio between Sentinel-2′s green and blue bands, are used to fit the spectral data with ICESat-2 height profiles. After water depth mapping using the trained model, independent ICESat-2 point clouds are used to validate the Sentinel-2 derived bathymetry. The RMSE values of the three models using the weighted average of multiple images for these six islands are within 0.50–0.90 m in 0–15 m deep. We also demonstrate that a synthesis of satellite laser altimetry and optical remote sensing can produce SDB results that potentially meet the requirement of category C in Zones of Confidence (ZOC) of the Electronic Navigational Chart (ENC) in 0–8 m deep. It is foreseen that ICESat-2 will be a helpful tool for mapping coastal and shallow waters around the world especially where bathymetric data are unavailable.
Hsiao-Jou Hsu; Chih-Yuan Huang; Michael Jasinski; Yao Li; Huilin Gao; Tsutomu Yamanokuchi; Cheng-Gi Wang; Tse-Ming Chang; Hsuan Ren; Chung-Yen Kuo; Kuo-Hsin Tseng. A semi-empirical scheme for bathymetric mapping in shallow water by ICESat-2 and Sentinel-2: A case study in the South China Sea. ISPRS Journal of Photogrammetry and Remote Sensing 2021, 178, 1 -19.
AMA StyleHsiao-Jou Hsu, Chih-Yuan Huang, Michael Jasinski, Yao Li, Huilin Gao, Tsutomu Yamanokuchi, Cheng-Gi Wang, Tse-Ming Chang, Hsuan Ren, Chung-Yen Kuo, Kuo-Hsin Tseng. A semi-empirical scheme for bathymetric mapping in shallow water by ICESat-2 and Sentinel-2: A case study in the South China Sea. ISPRS Journal of Photogrammetry and Remote Sensing. 2021; 178 ():1-19.
Chicago/Turabian StyleHsiao-Jou Hsu; Chih-Yuan Huang; Michael Jasinski; Yao Li; Huilin Gao; Tsutomu Yamanokuchi; Cheng-Gi Wang; Tse-Ming Chang; Hsuan Ren; Chung-Yen Kuo; Kuo-Hsin Tseng. 2021. "A semi-empirical scheme for bathymetric mapping in shallow water by ICESat-2 and Sentinel-2: A case study in the South China Sea." ISPRS Journal of Photogrammetry and Remote Sensing 178, no. : 1-19.
The Pacific island countries are particularly vulnerable to the effects of global warming including more frequent and intense natural disasters. Seawater inundation, one of the most serious disasters, could damage human property and life. Regional sea level rise, highest astronomic tide, vertical land motions, and extreme sea level could result in episodic, recurrent, or permanent coastal inundation. Therefore, assessing potential flooding areas is a critical task for coastal management plans. In this study, a simulation of the static flooding situation in the southwest coast of Taiwan (Tainan city) at the end of this century was conducted by using a combination of the Taiwan Digital Elevation Model (DEM), regional sea level changes reconstructed by tide gauge and altimetry data, vertical land deformation derived from leveling and GPS data, and ocean tide models. In addition, the extreme sea level situation, which typically results from high water on a spring tide and a storm surge, was also evaluated by the joint probability method using tide gauge records. To analyze the possible static flood risk and avoid overestimation of inundation areas, a region-based image segmentation method was employed in the estimated future topographic data to generate the flood risk map. In addition, an extreme sea level situation, which typically results from high water on a spring tide and a storm surge, was also evaluated by the joint probability method using tide gauge records. Results showed that the range of inundation depth around the Tainan area is 0–8 m with a mean value of 4 m. In addition, most of the inundation areas are agricultural land use (60% of total inundation area of Tainan), and two important international wetlands, 88.5% of Zengwun Estuary Wetlands and 99.5% of Sihcao Wetlands (the important Black-faced Spoonbills Refuge) will disappear under the combined situation. The risk assessment of flooding areas is potentially useful for coastal ocean and land management to develop appropriate adaptation policies for preventing disasters resulting from global climate change.
Moslem Imani; Chung-Yen Kuo; Pin-Chieh Chen; Kuo-Hsin Tseng; Huan-Chin Kao; Chi-Ming Lee; Wen-Hau Lan. Risk Assessment of Coastal Flooding under Different Inundation Situations in Southwest of Taiwan (Tainan City). Water 2021, 13, 880 .
AMA StyleMoslem Imani, Chung-Yen Kuo, Pin-Chieh Chen, Kuo-Hsin Tseng, Huan-Chin Kao, Chi-Ming Lee, Wen-Hau Lan. Risk Assessment of Coastal Flooding under Different Inundation Situations in Southwest of Taiwan (Tainan City). Water. 2021; 13 (6):880.
Chicago/Turabian StyleMoslem Imani; Chung-Yen Kuo; Pin-Chieh Chen; Kuo-Hsin Tseng; Huan-Chin Kao; Chi-Ming Lee; Wen-Hau Lan. 2021. "Risk Assessment of Coastal Flooding under Different Inundation Situations in Southwest of Taiwan (Tainan City)." Water 13, no. 6: 880.
Multi-mission satellite altimetry (e.g., ERS, Envisat, TOPEX/Poseidon, Jason) data have enabled a synoptic-scale view of ocean variations in past decades. Since 2016, the Sentinel-3 mission has provided better spatial and temporal sampling compared to its predecessors. The Sentinel-3 Ku/C Radar Altimeter (SRAL) is one of the synthetic aperture radar altimeters (SAR Altimeter) which is more precise for coastal and lake observations. The article studies the performance of the Sentinel-3 Level-2 sea level altimetry products in the coastal areas of the Baltic Sea and on two lakes of Estonia. The Sentinel-3 data were compared with (i) collocated Global Navigation Satellite System (GNSS) ship measurements, (ii) the Estonian geoid model (EST-GEOID2017) together with sea-level anomaly corrections from the tide gauges, and (iii) collocated buoy measurements. The comparisons were carried out along seven Sentinel-3A/B tracks across the Baltic Sea and Estonian lakes in 2019. In addition, the Copernicus Marine Environment Monitoring Service (CMEMS) Level-3 sea-level products and the Nucleus for European Modelling of the Ocean (NEMO) reanalysis outcomes were compared with measurements from Estonia’s 21 tide gauges and the buoy deployed offshore. Our results showed that the uncertainty of the Sentinel-3 Level-2 altimetry product was below decimetre level for the seacoast and the selected lakes of Estonia. Results from CMEMS Level-3 altimetry products showed a correlation of 0.83 (RMSE 0.18 m) and 0.91 (RMSE 0.27 m) when compared against the tide gauge measurements and the NEMO model, respectively. The overall performance of the altimetry products was very good, except in the immediate vicinity of the coastline and for the lakes, where the accuracy was nearly three times lower than for the open sea, but still acceptably good.
Aive Liibusk; Tarmo Kall; Sander Rikka; Rivo Uiboupin; Ülo Suursaar; Kuo-Hsin Tseng. Validation of Copernicus Sea Level Altimetry Products in the Baltic Sea and Estonian Lakes. Remote Sensing 2020, 12, 4062 .
AMA StyleAive Liibusk, Tarmo Kall, Sander Rikka, Rivo Uiboupin, Ülo Suursaar, Kuo-Hsin Tseng. Validation of Copernicus Sea Level Altimetry Products in the Baltic Sea and Estonian Lakes. Remote Sensing. 2020; 12 (24):4062.
Chicago/Turabian StyleAive Liibusk; Tarmo Kall; Sander Rikka; Rivo Uiboupin; Ülo Suursaar; Kuo-Hsin Tseng. 2020. "Validation of Copernicus Sea Level Altimetry Products in the Baltic Sea and Estonian Lakes." Remote Sensing 12, no. 24: 4062.
Multimission satellite altimetry (e.g. ERS, Envisat, TOPEX/Poseidon, Jason) data have enabled a synoptic view of ocean variations in the past decades, including sea-level rise and mesoscale circulations. Since 2016, the Sentinel-3 mission has provided better spatial and temporal sampling compared with its predecessors. The Sentinel-3 Ku/C Radar Altimeter (SRAL) is one of the synthetic aperture radar altimeters (SAR Altimeter) which is more precise in coastal and lake observations. In this study, we validate Sentinel-3 Level-2 products in Baltic Sea coastal areas and two lakes in Estonia. Moreover, the Copernicus Marine Environment Monitoring Service (CMEMS) Level-3 sea-level anomaly data and the Nucleus for European Modelling of the Ocean (NEMO) reanalysis model outcomes are compared with measurements from a tide gauge network. A dense in situ water level network deployed along the coast for geodetic observation was utilised to provide ground truths for validating altimetry results. Three validation methods were used for Level-2 data: (i) collocated Sentinel-3 and GNSS ship measurements; (ii) a national geoid model (EST-GEOID2017) with sea-level anomaly correction; (iii) collocated Sentinel-3 and buoy measurements. The validations were carried out in seven Sentinel-3A/B overpasses in 2019. Our results show that the uncertainty of the Sentinel-3 Level-2 altimetry product is below decimetre level on the Estonian coast and the targeted lakes. Results from CMEMS Level-3 showed a correlation of 0.8 (RMSE 0.19 m) and 0.91 (RMSE 0.27 m) when compared against tide gauge measurements and NEMO model, respectively.
Aive Liibusk; Tarmo Kall; Sander Rikka; Rivo Uiboupin; Ülo Suursaar; Kuo-Hsin Tseng. Validation of Sentinel-3 SAR Level-2 and Level-3 Products in the Baltic Sea and Estonian lakes. 2020, 1 .
AMA StyleAive Liibusk, Tarmo Kall, Sander Rikka, Rivo Uiboupin, Ülo Suursaar, Kuo-Hsin Tseng. Validation of Sentinel-3 SAR Level-2 and Level-3 Products in the Baltic Sea and Estonian lakes. . 2020; ():1.
Chicago/Turabian StyleAive Liibusk; Tarmo Kall; Sander Rikka; Rivo Uiboupin; Ülo Suursaar; Kuo-Hsin Tseng. 2020. "Validation of Sentinel-3 SAR Level-2 and Level-3 Products in the Baltic Sea and Estonian lakes." , no. : 1.
The 2019 International Symposium on Remote Sensing (ISRS-2019) took place in Taipei, Taiwan from 17 to 19 April 2019. ISRS is one of the distinguished conferences on the photogrammetry, remote sensing and spatial information sciences, especially in East Asia. More than 220 papers were presented in 37 technical sessions organized at the conference. This Special Issue publishes a limited number of featured peer-reviewed papers extended from their original contributions at ISRS-2019. The selected papers highlight a variety of topics pertaining to innovative concepts, algorithms and applications with geospatial sensors, systems, and data, in conjunction with emerging technologies such as artificial intelligence, machine leaning and advanced spatial analysis algorithms. The topics of the selected papers include the following: the on-orbit radiometric calibration of satellite optical sensors, environmental characteristics assessment with remote sensing, machine learning-based photogrammetry and image analysis, and the integration of remote sensing and spatial analysis. The selected contributions also demonstrate and discuss various sophisticated applications in utilizing remote sensing, geospatial data, and technologies to address different environmental and societal issues. Readers should find the Special Issue enlightening and insightful for understanding state-of-the-art remote sensing and spatial information science research, development and applications.
Fuan Tsai; Chao-Hung Lin; Walter W. Chen; Jen-Jer Jaw; Kuo-Hsin Tseng. Editorial for the Special Issue on Selected Papers from the “2019 International Symposium on Remote Sensing”. Remote Sensing 2020, 12, 1 .
AMA StyleFuan Tsai, Chao-Hung Lin, Walter W. Chen, Jen-Jer Jaw, Kuo-Hsin Tseng. Editorial for the Special Issue on Selected Papers from the “2019 International Symposium on Remote Sensing”. Remote Sensing. 2020; 12 (12):1.
Chicago/Turabian StyleFuan Tsai; Chao-Hung Lin; Walter W. Chen; Jen-Jer Jaw; Kuo-Hsin Tseng. 2020. "Editorial for the Special Issue on Selected Papers from the “2019 International Symposium on Remote Sensing”." Remote Sensing 12, no. 12: 1.
Sentinel-1 satellite launched by the European Space Agency (ESA) offers an opportunity to apply the differential interferometric synthetic aperture radar (DInSAR) in 12-day revisit, a potential solution to effectively measure surface deformation. However, for areas affected by the Equatorial Ionization Anomaly (EIA) in a global ionosphere pattern, the total electron content (TEC) irregularity between snapshots may induce extra fringes and further mislead the unwrapping and displacement results. To test the necessity of ionospheric correction, we utilize global and regional ionospheric vertical TEC maps, namely the Global Ionosphere Map (GIM) released by the International GNSS Service and the Taiwan Regional Ionospheric Map (TRIM) provided by a local GNSS network, to compensate ionospheric phases in the interferograms. Our experiments investigate 47 ascending image pairs in 2016 and 2017. Among them, two pairs of images whose differenced TEC (ΔTEC) stronger than 16.73 TEC unit in azimuthal gradient contain the clearest extra fringes. The results show that TRIM outperforms in reducing extra fringes caused by the ionospheric effect, with a root-mean-square error (RMSE) of the estimated satellite line-of-sight displacement reduced from 105.03 mm to 9.94 mm as compared against ground truth data. We conclude that TRIM TEC map is able to remove long-wavelength background of ionosphere-induced displacement when a differenced TEC gradient larger than an empirical threshold of 15 TECU.
Wan-Ting Liao; Kuo-Hsin Tseng; I-Te Lee; Aive Liibusk; Jui-Chi Lee; Jann-Yenq Liu; Chung-Pai Chang; Yu-Ching Lin. Sentinel-1 interferometry with ionospheric correction from global and local TEC maps for land displacement detection in Taiwan. Advances in Space Research 2019, 65, 1447 -1465.
AMA StyleWan-Ting Liao, Kuo-Hsin Tseng, I-Te Lee, Aive Liibusk, Jui-Chi Lee, Jann-Yenq Liu, Chung-Pai Chang, Yu-Ching Lin. Sentinel-1 interferometry with ionospheric correction from global and local TEC maps for land displacement detection in Taiwan. Advances in Space Research. 2019; 65 (5):1447-1465.
Chicago/Turabian StyleWan-Ting Liao; Kuo-Hsin Tseng; I-Te Lee; Aive Liibusk; Jui-Chi Lee; Jann-Yenq Liu; Chung-Pai Chang; Yu-Ching Lin. 2019. "Sentinel-1 interferometry with ionospheric correction from global and local TEC maps for land displacement detection in Taiwan." Advances in Space Research 65, no. 5: 1447-1465.
The Indus River, which flows through China, India, and Pakistan, is mainly fed by melting snow and glaciers that are spread across the Hindukush–Karakoram–Himalaya Mountains. The downstream population of the Indus Plain heavily relies on this water resource for drinking, irrigation, and hydropower generation. Therefore, its river runoff variability must be properly monitored. Gilgit Basin, the northwestern part of the Upper Indus Basin, is selected for studying cryosphere dynamics and its implications on river runoff. In this study, 8-day snow products (MOD10A2) of moderate resolution imaging spectroradiometer, from 2001 to 2015 are selected to access the snow-covered area (SCA) in the catchment. A non-parametric Mann–Kendall test and Sen’s slope are calculated to assess whether a significant trend exists in the SCA time series data. Then, data from ground observatories for 1995–2013 are analyzed to demonstrate annual and seasonal signals in air temperature and precipitation. Results indicate that the annual and seasonal mean of SCA show a non-significant decreasing trend, but the autumn season shows a statistically significant decreasing SCA with a slope of −198.36 km2/year. The annual mean temperature and precipitation show an increasing trend with highest values of slope 0.05 °C/year and 14.98 mm/year, respectively. Furthermore, Pearson correlation coefficients are calculated for the hydro-meteorological data to demonstrate any possible relationship. The SCA is affirmed to have a highly negative correlation with mean temperature and runoff. Meanwhile, SCA has a very weak relation with precipitation data. The Pearson correlation coefficient between SCA and runoff is −0.82, which confirms that the Gilgit River runoff largely depends on the melting of snow cover rather than direct precipitation. The study indicates that the SCA slightly decreased for the study period, which depicts a possible impact of global warming on this mountainous region.
Dostdar Hussain; Chung-Yen Kuo; Abdul Hameed; Kuo-Hsin Tseng; Bulbul Jan; Nasir Abbas; Huan-Chin Kao; Wen-Hau Lan; Moslem Imani. Spaceborne Satellite for Snow Cover and Hydrological Characteristic of the Gilgit River Basin, Hindukush–Karakoram Mountains, Pakistan. Sensors 2019, 19, 531 .
AMA StyleDostdar Hussain, Chung-Yen Kuo, Abdul Hameed, Kuo-Hsin Tseng, Bulbul Jan, Nasir Abbas, Huan-Chin Kao, Wen-Hau Lan, Moslem Imani. Spaceborne Satellite for Snow Cover and Hydrological Characteristic of the Gilgit River Basin, Hindukush–Karakoram Mountains, Pakistan. Sensors. 2019; 19 (3):531.
Chicago/Turabian StyleDostdar Hussain; Chung-Yen Kuo; Abdul Hameed; Kuo-Hsin Tseng; Bulbul Jan; Nasir Abbas; Huan-Chin Kao; Wen-Hau Lan; Moslem Imani. 2019. "Spaceborne Satellite for Snow Cover and Hydrological Characteristic of the Gilgit River Basin, Hindukush–Karakoram Mountains, Pakistan." Sensors 19, no. 3: 531.
It is widely believed that altimetry-derived sea surface heights (SSHs) in coastal zones are seriously degraded due to land contamination in altimeter waveforms from non-marine surfaces or due to inhomogeneous sea state conditions. Spurious peaks superimposed in radar waveforms adversely impact waveform retracking and hence require tailored algorithms to mitigate this problem. Here, we present an improved method to decontaminate coastal waveforms based on the waveform modification concept. SSHs within 10 km offshore are calculated from Jason-2 data by a 20% threshold retracker using decontaminated waveforms (DW-TR) and compared with those using original waveforms and modified waveforms in four study regions. We then compare our results with retracked SSHs in the sensor geophysical data record (SGDR) and with the state-of-the-art PISTACH (Prototype Innovant de Système de Traitement pour les Applications Côtières et l’Hydrologie) and ALES (Adaptive Leading Edge Subwaveform) products. Our result indicates that the DW-TR is the most robust retracker in the 0–10 km coastal band and provides consistent accuracy up to 1 km away from the coastline. In the four test regions, the DW-TR retracker outperforms other retrackers, with the smallest averaged standard deviations at 15 cm and 20 cm, as compared against the EGM08 (Earth Gravitational Model 2008) geoid model and tide gauge data, respectively. For the SGDR products, only the ICE retracker provides competitive SSHs for coastal applications. Subwaveform retrackers such as ICE3, RED3 and ALES perform well beyond 8 km offshore, but seriously degrade in the 0–8 km strip along the coast.
Zhengkai Huang; Haihong Wang; Zhicai Luo; C. K. Shum; Kuo-Hsin Tseng; Bo Zhong. Improving Jason-2 Sea Surface Heights within 10 km Offshore by Retracking Decontaminated Waveforms. Remote Sensing 2017, 9, 1077 .
AMA StyleZhengkai Huang, Haihong Wang, Zhicai Luo, C. K. Shum, Kuo-Hsin Tseng, Bo Zhong. Improving Jason-2 Sea Surface Heights within 10 km Offshore by Retracking Decontaminated Waveforms. Remote Sensing. 2017; 9 (10):1077.
Chicago/Turabian StyleZhengkai Huang; Haihong Wang; Zhicai Luo; C. K. Shum; Kuo-Hsin Tseng; Bo Zhong. 2017. "Improving Jason-2 Sea Surface Heights within 10 km Offshore by Retracking Decontaminated Waveforms." Remote Sensing 9, no. 10: 1077.
The Taiwanese government has established a complete tide gauge network along the coastline for accurate sea-level monitoring. In this study, we analyze several factors impacting the determination of absolute or geocentric sea-level trends—including ocean tides, inverted barometer effect, datum shift, and vertical land motion—using tide gauge records near Taiwan, from 1993–2015. The results show that datum shifts and vertical land motion have a significant impact on sea-level trends with a respective average contribution of 7.3 and 8.0 mm/yr, whereas ocean tides and inverted barometer effects have a relatively minor impact, representing 9% and 14% of the observed trend, respectively. These results indicate that datum shifts and vertical land motion effects have to be removed in the tide gauge records for accurate sea-level estimates. Meanwhile, the estimated land motions show that the southwestern plain has larger subsidence rates, for example, the Boziliao, Dongshi, and Wengang tide gauge stations exhibit a rate of 24–31 mm/yr as a result of groundwater pumping. We find that the absolute sea-level trends around Taiwan derived from tide gauges or satellite altimetry agree well with each other, and are estimated to be 2.2 mm/yr for 1993–2015, which is significantly slower than the global average sea-level rise trend of 3.2 mm/yr from satellite altimeters. Finally, a recent hiatus in sea-level rise in this region exhibits good agreement with the interannual and decadal variabilities associated with the El Niño-Southern Oscillation and Pacific Decadal Oscillation.
Wen-Hau Lan; Chung-Yen Kuo; Huan-Chin Kao; Li-Ching Lin; C. K. Shum; Kuo-Hsin Tseng; Jung-Chieh Chang. Impact of Geophysical and Datum Corrections on Absolute Sea-Level Trends from Tide Gauges around Taiwan, 1993–2015. Water 2017, 9, 480 .
AMA StyleWen-Hau Lan, Chung-Yen Kuo, Huan-Chin Kao, Li-Ching Lin, C. K. Shum, Kuo-Hsin Tseng, Jung-Chieh Chang. Impact of Geophysical and Datum Corrections on Absolute Sea-Level Trends from Tide Gauges around Taiwan, 1993–2015. Water. 2017; 9 (7):480.
Chicago/Turabian StyleWen-Hau Lan; Chung-Yen Kuo; Huan-Chin Kao; Li-Ching Lin; C. K. Shum; Kuo-Hsin Tseng; Jung-Chieh Chang. 2017. "Impact of Geophysical and Datum Corrections on Absolute Sea-Level Trends from Tide Gauges around Taiwan, 1993–2015." Water 9, no. 7: 480.
Spherical harmonics (SH) and mascon solutions are the two most common types of solutions for Gravity Recovery and Climate Experiment (GRACE) mass flux observations. However, SH signals are degraded by measurement and leakage errors. Mascon solutions (the Jet Propulsion Laboratory (JPL) release, herein) exhibit weakened signals at submascon resolutions. Both solutions require a scale factor examined by the CLM4.0 model to obtain the actual water storage signal. The Slepian localization method can avoid the SH leakage errors when applied to the basin scale. In this study, we estimate SH errors and scale factors for African hydrological regimes. Then, terrestrial water storage (TWS) in Africa is determined based on Slepian localization and compared with JPL-mascon and SH solutions. The three TWS estimates show good agreement for the TWS of large-sized and humid regimes but present discrepancies for the TWS of medium and small-sized regimes. Slepian localization is an effective method for deriving the TWS of arid zones. The TWS behavior in African regimes and its spatiotemporal variations are then examined. The negative TWS trends in the lower Nile and Sahara at −1.08 and −6.92 Gt/year, respectively, are higher than those previously reported.
Ashraf Rateb; Chung-Yen Kuo; Moslem Imani; Kuo-Hsin Tseng; Wen-Hau Lan; Kuo-En Ching; Tzu-Pang Tseng. Terrestrial Water Storage in African Hydrological Regimes Derived from GRACE Mission Data: Intercomparison of Spherical Harmonics, Mass Concentration, and Scalar Slepian Methods. Sensors 2017, 17, 566 .
AMA StyleAshraf Rateb, Chung-Yen Kuo, Moslem Imani, Kuo-Hsin Tseng, Wen-Hau Lan, Kuo-En Ching, Tzu-Pang Tseng. Terrestrial Water Storage in African Hydrological Regimes Derived from GRACE Mission Data: Intercomparison of Spherical Harmonics, Mass Concentration, and Scalar Slepian Methods. Sensors. 2017; 17 (3):566.
Chicago/Turabian StyleAshraf Rateb; Chung-Yen Kuo; Moslem Imani; Kuo-Hsin Tseng; Wen-Hau Lan; Kuo-En Ching; Tzu-Pang Tseng. 2017. "Terrestrial Water Storage in African Hydrological Regimes Derived from GRACE Mission Data: Intercomparison of Spherical Harmonics, Mass Concentration, and Scalar Slepian Methods." Sensors 17, no. 3: 566.
In Novaya Zemlya (NVZ), melting marine-terminating glaciers have been identified to be the most significant contributor to the ice loss. However, the influence of influx on mass loss has not been discussed in previous studies. In this study, we present multiple geodetic observations of four glaciers along the Barents Sea coast to determine the influence of glacier outflow on net mass change by considering the mass gain from snowfall. We obtained the average ice loss rate of –1.04 ± 0.25 Gt year–1 during the period of 2003–2014 from the gravity recovery and climate experiment (GRACE) data. We discovered an interannual increase of 4.30 ± 0.97 Gt year–1 in 2007–2010 which had not been presented. In addition, we also observed two other interannual variations in the form of negative mass trends from GRACE during the periods of 2004–2007 and 2010–2014. A speckle-matching technique was applied on pairs of synthetic aperture radar data to fill the gap of velocity estimations for the period of 2007–2010 which were not reported in previous studies. The mass increase in 2007–2010 can be explained by the increase in influx while the change in outflow was negligible. In addition, we extended similar analysis to the periods of 2002–2007 and 2010–2014, and identified the contribution of outflow and influx to the mass change in NVZ. In particular, the mass losses in the periods of 2004–2007 and 2010–2013 in NVZ were related to the significant increase of outflow while positive influx anomalies were observed.
Zhiyue Sun; Hyongki Lee; Yushin Ahn; Abureli Aierken; Kuo-Hsin Tseng; Modurodoluwa A. Okeowo; C. K. Shum. Recent Glacier Dynamics in the Northern Novaya Zemlya Observed by Multiple Geodetic Techniques. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 2017, 10, 1290 -1302.
AMA StyleZhiyue Sun, Hyongki Lee, Yushin Ahn, Abureli Aierken, Kuo-Hsin Tseng, Modurodoluwa A. Okeowo, C. K. Shum. Recent Glacier Dynamics in the Northern Novaya Zemlya Observed by Multiple Geodetic Techniques. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 2017; 10 (4):1290-1302.
Chicago/Turabian StyleZhiyue Sun; Hyongki Lee; Yushin Ahn; Abureli Aierken; Kuo-Hsin Tseng; Modurodoluwa A. Okeowo; C. K. Shum. 2017. "Recent Glacier Dynamics in the Northern Novaya Zemlya Observed by Multiple Geodetic Techniques." IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 10, no. 4: 1290-1302.
The Qinghai-Tibetan plateau (QTP), also known as the Third Pole and the World Water Tower, is the largest and highest plateau with distinct and competing surface and subsurface processes. It is covered by a large layer of discontinuous and sporadic alpine permafrost which has degraded 10% during the past few decades. The average active layer thickness (ALT) increase rate is approximately 7.5 cm·yr−1 from 1995 to 2007, based on soil temperature measurements from 10 borehole sites along Qinghai-Tibetan Highway, and approximately 6.3 cm·yr−1, 2006–2010, using soil temperature profiles for 27 monitoring sites along Qinghai-Tibetan railway. In this study, we estimated the ALT and its AL thickening rate in the northern QTP near the railway using ALOS PALSAR L-band small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) data observed land subsidence and the corresponding ALT modeling. The InSAR estimated ALT and AL thickening rate were validated with ground-based observations from the borehole site WD4 within our study region, indicating excellent agreement. We concluded that we have generated high spatial resolution (30 m) and spatially-varying ALT and AL thickening rates, 2007–2009, over approximately an area of 150 km2 of permafrost-covered region in the northern QTP.
Yuanyuan Jia; Jin-Woo Kim; C. K. Shum; Zhong Lu; Xiaoli Ding; Lei Zhang; Kamil Erkan; Chung-Yen Kuo; Kun Shang; Kuo-Hsin Tseng; Yuchan Yi. Characterization of Active Layer Thickening Rate over the Northern Qinghai-Tibetan Plateau Permafrost Region Using ALOS Interferometric Synthetic Aperture Radar Data, 2007–2009. Remote Sensing 2017, 9, 84 .
AMA StyleYuanyuan Jia, Jin-Woo Kim, C. K. Shum, Zhong Lu, Xiaoli Ding, Lei Zhang, Kamil Erkan, Chung-Yen Kuo, Kun Shang, Kuo-Hsin Tseng, Yuchan Yi. Characterization of Active Layer Thickening Rate over the Northern Qinghai-Tibetan Plateau Permafrost Region Using ALOS Interferometric Synthetic Aperture Radar Data, 2007–2009. Remote Sensing. 2017; 9 (1):84.
Chicago/Turabian StyleYuanyuan Jia; Jin-Woo Kim; C. K. Shum; Zhong Lu; Xiaoli Ding; Lei Zhang; Kamil Erkan; Chung-Yen Kuo; Kun Shang; Kuo-Hsin Tseng; Yuchan Yi. 2017. "Characterization of Active Layer Thickening Rate over the Northern Qinghai-Tibetan Plateau Permafrost Region Using ALOS Interferometric Synthetic Aperture Radar Data, 2007–2009." Remote Sensing 9, no. 1: 84.
Satellite observations can either be assimilated as radiances or as retrieved physical parameters to reduce error in the initial conditions used by the Numerical Weather Prediction (NWP) model. Assimilation of radiances requires a radiative transfer model to convert atmospheric state in model space to that in radiance space, thus requiring a lot of computational resources especially for hyperspectral instruments with thousands of channels. On the other hand, assimilating the retrieved physical parameters is computationally more efficient as they are already in thermodynamic states, which can be compared with NWP model outputs through the objective analysis scheme. A microwave (MW) sounder and an infrared (IR) sounder have their respective observational limitation due to the characteristics of adopted spectra. The MW sounder observes at much larger field-of-view (FOV) compared to an IR sounder. On the other hand, MW has the capability to reveal the atmospheric sounding when the clouds are presented, but IR observations are highly sensitive to clouds, The advanced IR sounder is able to reduce uncertainties in the retrieved atmospheric temperature and moisture profiles due to its higher spectral-resolution than the MW sounder which has much broader spectra bands. This study tries to quantify the optimal use of soundings retrieved from the microwave sounder AMSU and infrared sounder AIRS onboard the AQUA satellite in the regional Weather and Research Forecasting (WRF) model through three-dimensional variational (3D-var) data assimilation scheme. Four experiments are conducted by assimilating soundings from: (1) clear AIRS single field-of-view (SFOV); (2) retrieved from using clear AMSU and AIRS observations at AMSU field-of-view (SUP); (3) all SFOV soundings within AMSU FOVs must be clear; and (4) SUP soundings which must have all clear SFOV soundings within the AMSU FOV. A baseline experiment assimilating only conventional data is generated for comparison. Various atmospheric state variables at different pressure levels are used to assess the impact from assimilating these different data by comparing them with European Centre for Medium Range Weather Forecast (ECMWF) reanalysis data. Results indicate assimilation of SUP soundings improve the mid and upper troposphere, whereas assimilation of SFOV soundings has positive impact on the lower troposphere. Two additional assimilation experiments are carried out to determine the combination of SUP and SFOV soundings that will provide the best performance throughout the troposphere. The results indicate that optimal combination is to assimilate clear-sky matched IR retrievals with non-matched MW soundings.
Chian-Yi Liu; Szu-Chen Kuo; Agnes H. N. Lim; Shen-Cha Hsu; Kuo-Hsin Tseng; Nan Ching Yeh; Yu-Chi Yang. Optimal Use of Space-Borne Advanced Infrared and Microwave Soundings for Regional Numerical Weather Prediction. Remote Sensing 2016, 8, 816 .
AMA StyleChian-Yi Liu, Szu-Chen Kuo, Agnes H. N. Lim, Shen-Cha Hsu, Kuo-Hsin Tseng, Nan Ching Yeh, Yu-Chi Yang. Optimal Use of Space-Borne Advanced Infrared and Microwave Soundings for Regional Numerical Weather Prediction. Remote Sensing. 2016; 8 (10):816.
Chicago/Turabian StyleChian-Yi Liu; Szu-Chen Kuo; Agnes H. N. Lim; Shen-Cha Hsu; Kuo-Hsin Tseng; Nan Ching Yeh; Yu-Chi Yang. 2016. "Optimal Use of Space-Borne Advanced Infrared and Microwave Soundings for Regional Numerical Weather Prediction." Remote Sensing 8, no. 10: 816.
Glaciers over the Tibetan Plateau have experienced accelerated depletion in the last few decades due primarily to the global warming. The freshwater drained into brackish lakes is also observed by optical remote sensing and altimetry satellites. However, the actual water storage change is difficult to be quantified since the altimetry or remote sensing only provide data in limited dimensions. The altimetry data give an elevation change of surface while the remote sensing images provide an extent variation in horizontal plane. Hence a data set used to describe the volume change is needed to measure the exact mass transition in a time span. In this study, we utilize GRACE gravimetry mission to quantify the total column mass change in the central Tibetan Plateau, especially focused on the lakes near Tanggula Mountains. By removing these factors, the freshwater storage change of glacier system at study area can be potentially isolated.
K.-H. Tseng; K. T. Liu; C. K. Shum; Y. Jia; K. Shang; C. Dai. QUANTIFICATION OF GLACIER DEPLETION IN THE CENTRAL TIBETAN PLATEAU BY USING INTEGRATED SATELLITE REMOTE SENSING AND GRAVIMETRY. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences 2016, XLI-B8, 399 -402.
AMA StyleK.-H. Tseng, K. T. Liu, C. K. Shum, Y. Jia, K. Shang, C. Dai. QUANTIFICATION OF GLACIER DEPLETION IN THE CENTRAL TIBETAN PLATEAU BY USING INTEGRATED SATELLITE REMOTE SENSING AND GRAVIMETRY. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2016; XLI-B8 ():399-402.
Chicago/Turabian StyleK.-H. Tseng; K. T. Liu; C. K. Shum; Y. Jia; K. Shang; C. Dai. 2016. "QUANTIFICATION OF GLACIER DEPLETION IN THE CENTRAL TIBETAN PLATEAU BY USING INTEGRATED SATELLITE REMOTE SENSING AND GRAVIMETRY." The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B8, no. : 399-402.
The Tibetan Plateau (TP) has been observed by satellite optical remote sensing, altimetry, and gravimetry for a variety of geophysical parameters, including water storage change. However, each of these sensors has its respective limitation in the parameters observed, accuracy and spatial-temporal resolution. Here, we utilized an integrated approach to combine remote sensing imagery, digital elevation model, and satellite radar and laser altimetry data, to quantify freshwater storage change in a twin lake system named Chibuzhang Co and Dorsoidong Co in the central TP, and compared that with independent observations including mass changes from the Gravity Recovery and Climate Experiment (GRACE) data. Our results show that this twin lake, located within the Tanggula glacier system, remained almost steady during 1973–2000. However, Dorsoidong Co has experienced a significant lake level rise since 2000, especially during 2000–2005, that resulted in the plausible connection between the two lakes. The contemporary increasing lake level signal at a rate of 0.89 ± 0.05 cm·yr−1, in a 2° by 2° grid equivalent water height since 2002, is higher than the GRACE observed trend at 0.41 ± 0.17 cm·yr−1 during the same time span. Finally, a down-turning trend or inter-annual variability shown in the GRACE signal is observed after 2012, while the lake level is still rising at a consistent rate.
Kuo-Hsin Tseng; Chung-Pai Chang; C. K. Shum; Chung-Yen Kuo; Kuan-Ting Liu; Kun Shang; Yuanyuan Jia; Jian Sun. Quantifying Freshwater Mass Balance in the Central Tibetan Plateau by Integrating Satellite Remote Sensing, Altimetry, and Gravimetry. Remote Sensing 2016, 8, 441 .
AMA StyleKuo-Hsin Tseng, Chung-Pai Chang, C. K. Shum, Chung-Yen Kuo, Kuan-Ting Liu, Kun Shang, Yuanyuan Jia, Jian Sun. Quantifying Freshwater Mass Balance in the Central Tibetan Plateau by Integrating Satellite Remote Sensing, Altimetry, and Gravimetry. Remote Sensing. 2016; 8 (6):441.
Chicago/Turabian StyleKuo-Hsin Tseng; Chung-Pai Chang; C. K. Shum; Chung-Yen Kuo; Kuan-Ting Liu; Kun Shang; Yuanyuan Jia; Jian Sun. 2016. "Quantifying Freshwater Mass Balance in the Central Tibetan Plateau by Integrating Satellite Remote Sensing, Altimetry, and Gravimetry." Remote Sensing 8, no. 6: 441.
Water level (WL) and water volume (WV) of surface-water bodies are among the most crucial variables used in water-resources assessment and management. They fluctuate as a result of climatic forcing, and they are considered as indicators of climatic impacts on water resources. Quantifying riverine WL and WV, however, usually requires the availability of timely and continuous in situ data, which could be a challenge for rivers in remote regions, including the Mekong River basin. As one of the most developed rivers in the world, with more than 20 dams built or under construction, Mekong River is in need of a monitoring system that could facilitate basin-scale management of water resources facing future climate change. This study used spaceborne sensors to investigate two dams in the upper Mekong River, Xiaowan and Jinghong Dams within China, to examine river flow dynamics after these dams became operational. We integrated multi-mission satellite radar altimetry (RA, Envisat and Jason-2) and Landsat-5/-7/-8 Thematic Mapper (TM)/Enhanced Thematic Mapper plus (ETM+)/Operational Land Imager (OLI) optical remote sensing (RS) imageries to construct composite WL time series with enhanced spatial resolutions and substantially extended WL data records. An empirical relationship between WL variation and water extent was first established for each dam, and then the combined long-term WL time series from Landsat images are reconstructed for the dams. The R2 between altimetry WL and Landsat water area measurements is >0.95. Next, the Tropical Rainfall Measuring Mission (TRMM) data were used to diagnose and determine water variation caused by the precipitation anomaly within the basin. Finally, the impact of hydrologic dynamics caused by the impoundment of the dams is assessed. The discrepancy between satellite-derived WL and available in situ gauge data, in term of root-mean-square error (RMSE) is at 2–5 m level. The estimated WV variations derived from combined RA/RS imageries and digital elevation model (DEM) are consistent with results from in situ data with a difference at about 3%. We concluded that the river level downstream is affected by a combined operation of these two dams after 2009, which has decreased WL by 0.20 m·year−1 in wet seasons and increased WL by 0.35 m·year−1 in dry seasons.
Kuan-Ting Liu; Kuo-Hsin Tseng; C. K. Shum; Chian-Yi Liu; Chung-Yen Kuo; Ganming Liu; Yuanyuan Jia; Kun Shang. Assessment of the Impact of Reservoirs in the Upper Mekong River Using Satellite Radar Altimetry and Remote Sensing Imageries. Remote Sensing 2016, 8, 367 .
AMA StyleKuan-Ting Liu, Kuo-Hsin Tseng, C. K. Shum, Chian-Yi Liu, Chung-Yen Kuo, Ganming Liu, Yuanyuan Jia, Kun Shang. Assessment of the Impact of Reservoirs in the Upper Mekong River Using Satellite Radar Altimetry and Remote Sensing Imageries. Remote Sensing. 2016; 8 (5):367.
Chicago/Turabian StyleKuan-Ting Liu; Kuo-Hsin Tseng; C. K. Shum; Chian-Yi Liu; Chung-Yen Kuo; Ganming Liu; Yuanyuan Jia; Kun Shang. 2016. "Assessment of the Impact of Reservoirs in the Upper Mekong River Using Satellite Radar Altimetry and Remote Sensing Imageries." Remote Sensing 8, no. 5: 367.
The Thematic Mapper onboard Landsat 4, 5, and Enhanced Thematic Mapper Plus ( $text{TM/ETM}+$ ) onboard Landsat 7 have frequency bands (green and SWIR) to effectively measure water body extents and their changes via the Modified Normalized Difference Water Index (MNDWI). Here, we developed a technique, called the thematic imagery-altimetry system (TIAS), to infer the vertical water changes from MNDWI horizontal water extent changes by integrating long-term $text{TM/ETM}+$ imageries with available digital elevation models (DEMs). The result is a technique to quantify water level changes of natural or artificial water bodies over two decades. Several DEMs were used to compute intersects with $text{TM/ETM}+$ water extent time series to evaluate the robustness of the technique. These DEMs include: the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Map version 2 (ASTER-GDEM2, at 1 arcsec resolution), the Shuttle Radar Topography Mission version 2 (SRTM C-band at 1 arcsec), and the Global Multiresolution Terrain Elevation Data (GMTED2010 at 7.5 arcsec). We demonstrated our technique near Hoover Dam (HD) in Lake Mead to quantify its respective decadal water level changes. The dammed water had experienced extraordinary level variation in the past 20 years due to natural decline from intake or artificial impoundments. The discrepancy of the HD water level changes from an analysis of 32-year (1984–2015) time series, including $584$ Landsat scenes, using the GMTED2010 DEM, has a RMSE reached $0.85 pm 0.63; text{m}$ (91% of data) as compared with in situ stage record.
Kuo-Hsin Tseng; C. K. Shum; Jin-Woo Kim; Xianwei Wang; Kefeng Zhu; Xiao Cheng. Integrating Landsat Imageries and Digital Elevation Models to Infer Water Level Change in Hoover Dam. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 2016, 9, 1696 -1709.
AMA StyleKuo-Hsin Tseng, C. K. Shum, Jin-Woo Kim, Xianwei Wang, Kefeng Zhu, Xiao Cheng. Integrating Landsat Imageries and Digital Elevation Models to Infer Water Level Change in Hoover Dam. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 2016; 9 (4):1696-1709.
Chicago/Turabian StyleKuo-Hsin Tseng; C. K. Shum; Jin-Woo Kim; Xianwei Wang; Kefeng Zhu; Xiao Cheng. 2016. "Integrating Landsat Imageries and Digital Elevation Models to Infer Water Level Change in Hoover Dam." IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 9, no. 4: 1696-1709.