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104. Satellite radar altimetry for monitoring small rivers and lakes in Indonesia

Author

Sulistioadi, Y.B., Tseng, K.H., Shum, C.K., Hidayat, Hidayat, Sumaryono, M., Suhardiman, A., Setiawan, F., Sunarso, S., Sulistioadi, Y.B., Tseng, K.H., Shum, C.K., Hidayat, Hidayat, Sumaryono, M., Suhardiman, A., Setiawan, F., and Sunarso, S.

Abstract

Remote sensing and satellite geodetic observations are capable of hydrologic monitoring of freshwater resources. Although satellite radar altimetry has been used in monitoring water level or discharge, its use is often limited to monitoring large rivers (>1 km) with longer interval periods (>1 week) because of its low temporal and spatial resolutions (i.e., satellite revisit period). Several studies have reported successful retrieval of water levels for small rivers as narrow as 40 m. However, processing current satellite altimetry signals for such small water bodies to retrieve water levels accurately remains challenging. Physically, the radar signal returned by water bodies smaller than the satellite footprint is most likely contaminated by non-water surfaces, which may degrade the measurement quality. In order to address this scientific challenge, we carefully selected the waveform shapes corresponding to the range measurement resulting from standard retrackers for the European Space Agency's (ESA's) Envisat (Environmental Satellite) radar altimetry. We applied this approach to small (40-200 m in width) and medium-sized (200-800 m in width) rivers and small lakes (extent 2) in the humid tropics of Southeast Asia, specifically in Indonesia. This is the first study that explored the ability of satellite altimetry to monitor small water bodies in Indonesia. The major challenges in this study include the size of the water bodies that are much smaller than the nominal extent of the Envisat satellite footprint (e.g., ~250 m compared to ~1.7 km, respectively) and slightly smaller than the along-track distance (i.e., ~370 m). We addressed this challenge by optimally using geospatial information and optical remote sensing data to define the water bodies accurately, thus minimizing the probability of non-water contamination in the altimetry measurement. Considering that satellite altimetry processing may vary with different geographical regions, meteorological conditions

Published
2015

108. Observations: oceanic climate and sea level

Author

Bindoff, N., Willebrand, J., Artale, V., Cazenave, A., Gregory, J., Gulev, S., Hanawa, K., Le Quéré, C., Levitus, S., Nojiri, Y., Shum, C.K., Talley, L., Unnikrishnan, A., Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences
Abstract

Contribution of Working Group I to the Fourth Assessment report of the Intergouvernmental Panel on Climate Change; The oceans are warming. Over the period 1961 to 2003, global ocean temperature has risen by 0.10°C from the surface to a depth of 700 m. Consistent with the Third Assessment Report (TAR), global ocean heat content (0–3,000 m) has increased during the same period, equivalent to absorbing energy at a rate of 0.21 ± 0.04 W m–2 globally averaged over the Earth’s surface. Two-thirds of this energy is absorbed between the surface and a depth of 700 m. Global ocean heat content observations show considerable interannual and inter-decadal variability superimposed on the longer-term trend. Relative to 1961 to 2003, the period 1993 to 2003 has high rates of warming but since 2003 there has been some cooling.Large-scale, coherent trends of salinity are observed for 1955 to 1998, and are characterised by a global freshening in subpolar latitudes and a salinification of shallower parts of the tropical and subtropical oceans. Freshening is pronounced in the Pacific while increasing salinities prevail over most of Atlantic and Indian Oceans. These trends are consistent with changes in precipitation and inferred larger water transport in the atmosphere from low latitudes to high latitudes and from the Atlantic to the Pacific. Observations do not allow for a reliable estimate of the global average change in salinity in the oceans.Key oceanic water masses are changing; however, there is no clear evidence for ocean circulation changes. Southern Ocean mode waters and Upper Circumpolar Deep Waters have warmed from the 1960s to about 2000. A similar but weaker pattern of warming in the Gulf Stream and Kuroshio mode waters in the North Atlantic and North Pacific has been observed. Long-term cooling is observed in the North Atlantic subpolar gyre and in the central North Pacific. Since 1995, the upper North Atlantic subpolar gyre has been warming and becoming more saline. It is very likely that up to the end of the 20th century, the Atlantic meridional overturning circulation has been changing significantly at interannual to decadal time scales. Over the last 50 years, no coherent evidence for a trend in the strength of the meridional overturning circulation has been found.Ocean biogeochemistry is changing. The total inorganic carbon content of the oceans has increased by 118 ± 19 GtC between the end of the pre-industrial period (about 1750) and 1994 and continues to increase. It is more likely than not that the fraction of emitted carbon dioxide that was taken up by the oceans has decreased, from 42 ± 7% during 1750 to 1994 to 37 ± 7% during 1980 to 2005. This would be consistent with the expected rate at which the oceans can absorb carbon, but the uncertainty in this estimate does not allow firm conclusions. The increase in total inorganic carbon caused a decrease in the depth at which calcium carbonate dissolves, and also caused a decrease in surface ocean pH by an average of 0.1 units since 1750. Direct observations of pH at available time series stations for the last 20 years also show trends of decreasing pH at a rate of 0.02 pH units per decade. There is evidence for decreased oxygen concentrations, likely driven by reduced rates of water renewal, in the thermocline (~100–1,000 m) in most ocean basins from the early 1970s to the late 1990s.Global mean sea level has been rising. From 1961 to 2003, the average rate of sea level rise was 1.8 ± 0.5 mm yr–1. For the 20th century, the average rate was 1.7 ± 0.5 mm yr–1, consistent with the TAR estimate of 1 to 2 mm yr– 1. There is high confidence that the rate of sea level rise has increased between the mid-19th and the mid-20th centuries. Sea level change is highly non-uniform spatially, and in some regions, rates are up to several times the global mean rise, while in other regions sea level is falling. There is evidence for an increase in the occurrence of extreme high water worldwide related to storm surges, and variations in extremes during this period are related to the rise in mean sea level and variations in regional climate.The rise in global mean sea level is accompanied by considerable decadal variability. For the period 1993 to 2003, the rate of sea level rise is estimated from observations with satellite altimetry as 3.1 ± 0.7 mm yr–1, significantly higher than the average rate. The tide gauge record indicates that similar large rates have occurred in previous 10-yearperiods since 1950. It is unknown whether the higher rate in 1993 to 2003 is due to decadal variability or an increase in the longer-term trend.There are uncertainties in the estimates of the contributions to sea level change but understanding has significantly improved for recent periods. For the period 1961 to 2003, the average contribution of thermal expansion to sea level rise was 0.4 ± 0.1 mm yr–1. As reported in the TAR, it is likely that the sum of all known contributions for this period is smaller than the observed sea level rise, and therefore it is not possible to satisfactorily account for the processes causing sea level rise. However, for the period 1993 to 2003, for which the observing system is much better, the contributions from thermal expansion (1.6 ± 0.5 mm yr–1) and loss of mass from glaciers, ice caps and the Greenland and Antarctic Ice Sheets together give 2.8 ± 0.7 mm yr–1. For the latter period, the climate contributions constitute the main factors in the sea level budget, which is closed to within known errors.The patterns of observed changes in global ocean heat content and salinity, sea level, thermal expansion, water mass evolution and biogeochemical parameters described in this chapter are broadly consistent with the observed ocean surface changes and the known characteristics of the large-scale ocean circulation.

Published
2007

109. Comparison of sea surface heights by JASON and ocean bottom gauges: the MOTEVAS project (SW Pacific)

Author

Calmant, S., Cheng, K., Jan, G., Shum, C.K., Yi, Y., Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)

Published
2004

110. Multi-satellite altimetry and GOCE geoid based surface and subsurface currents in the Mediterranean Sea

Author

Universitat Politècnica de Catalunya. Departament d'Enginyeria del Terreny, Cartogràfica i Geofísica, Universitat Politècnica de Catalunya. EGEO - Enginyeria Geomàtica, Martínez Benjamín, Juan José, Chang, Chi-Hung, Kuo, Chung-Yen, Shum, C.K., Yi, Yuchan, Universitat Politècnica de Catalunya. Departament d'Enginyeria del Terreny, Cartogràfica i Geofísica, Universitat Politècnica de Catalunya. EGEO - Enginyeria Geomàtica, Martínez Benjamín, Juan José, Chang, Chi-Hung, Kuo, Chung-Yen, Shum, C.K., and Yi, Yuchan

Abstract

Peer Reviewed, Postprint (published version)

Published
2014

111. GEROS-ISS: Innovative Ocean Remote Sensing using GNSS Reflectometry onboard the International Space Station

Author

Wickert, Jens, Andersen, Ole Baltazar, Beyerle, George, Chapron, Bernard, Cardellach, Estel, Gommenginger, Christine, Høeg, Per, Jäggi, Adrian, Jakowski, Norbert, Kern, Michael, Lee, Tony, Martin-Neira, Manuel, Pierdicca, Nazzareno, Shum, C.K., Zuffada, Cinzia, Wickert, Jens, Andersen, Ole Baltazar, Beyerle, George, Chapron, Bernard, Cardellach, Estel, Gommenginger, Christine, Høeg, Per, Jäggi, Adrian, Jakowski, Norbert, Kern, Michael, Lee, Tony, Martin-Neira, Manuel, Pierdicca, Nazzareno, Shum, C.K., and Zuffada, Cinzia

Published
2014

116. A Promising Radar Altimetry Satellite System for Operational Flood Forecasting in Flood-Prone Bangladesh

Author

Hossain, Faisal, primary, Maswood, Mehedi, additional, Siddique-E-Akbor, A.H., additional, Yigzaw, Wondmagegn, additional, Mazumdar, Liton Chandra, additional, Ahmed, Tanvir, additional, Hossain, Monowar, additional, Shah-Newaz, S.M., additional, Limaye, Ashutosh, additional, Lee, Hyongki, additional, Pradhan, Sudip, additional, Shrestha, Basanta, additional, Bajracahrya, Birendra, additional, Biancamaria, Sylvain, additional, Shum, C.K., additional, and Turk, F.J., additional

Published
2014
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117. New Views of Earth using ERS Satellite Altimetry

Author

Fletcher, K., Andersen, O.B., Knudsen, P., Berry, P., Smith, R., Rémy, F., Flament, T., Calmant, S., Cipollini, P, Laxton, S., Shephard, A., McAdoo, D., Scharroo, R., Smith, W., Sandwell, D., Schaeffer, P., Bamber, J., Shum, C.K., Yi, Y., Benveniste, J., Fletcher, K., Andersen, O.B., Knudsen, P., Berry, P., Smith, R., Rémy, F., Flament, T., Calmant, S., Cipollini, P, Laxton, S., Shephard, A., McAdoo, D., Scharroo, R., Smith, W., Sandwell, D., Schaeffer, P., Bamber, J., Shum, C.K., Yi, Y., and Benveniste, J.

Published
2013

118. GEROS-ISS: Innovative GNSS based Remote Sensing aboard the International Space Station for GGOS

Author

Wickert, Jens, Andersen, Ole Baltazar, Beyerle, George, Chapron, Bernard, Cardellach, Estel, D'Addio, S., Förste , C., Gommenginger, Christine, Gruber, T., Helm, A., Hess, M. P., Høeg, Per, Jäggi, Adrian, Jakowski, Norbert, Kern, M., Lee, T, Martin-Neira, Manuel, Montenbruck, O., Pierdicca, Nazzareno, Rius, Antonio, Rothacher, M., Shum, C.K., Zuffada, Cinzia, Wickert, Jens, Andersen, Ole Baltazar, Beyerle, George, Chapron, Bernard, Cardellach, Estel, D'Addio, S., Förste , C., Gommenginger, Christine, Gruber, T., Helm, A., Hess, M. P., Høeg, Per, Jäggi, Adrian, Jakowski, Norbert, Kern, M., Lee, T, Martin-Neira, Manuel, Montenbruck, O., Pierdicca, Nazzareno, Rius, Antonio, Rothacher, M., Shum, C.K., and Zuffada, Cinzia

Published
2013

119. The challenge for measuring sea level rise and regional and global trends

Author

Hall, J., Harrison, D.E., Stammer, D., Cazenave, A., Chambers, D.P., Cipollini, P., Fu, L.-L., Hurell, J.W., Merrifield, M., Nerem, R.S., Plag, H.P., Shum, C.K., Willis, J., Hall, J., Harrison, D.E., Stammer, D., Cazenave, A., Chambers, D.P., Cipollini, P., Fu, L.-L., Hurell, J.W., Merrifield, M., Nerem, R.S., Plag, H.P., Shum, C.K., and Willis, J.

Published
2010

120. Geodetic observations of the ocean surface topography, geoid, currents, and changes in ocean mass and volume

Author

Hall, J., Harrison, D.E., Stammer, D., Shum, C.K., Plag, Hans-Peter, Schroter, Jens, Zlotnickie, Victor, Bender, Peter, Braun, Alexander, Cazenave, Anny, Chamber, Don, Duan, Jianbin, Emery, William, Fotopoulos, Georgia, Gouretski, Viktor, Gross, Richard, Gruber, Thomas, Guo, Junyi, Han, Guoqi, Hughes, Chris, Ishii, Masayoshi, Jayne, Steven, Johannessen, Johnny, Knudsen, Per, Kuo, Chung-Yen, Leuliette, Eric, Levitus, Sydney, Maximenko, Nikolai, Miller, Laury, Morison, James, Rashid, Harunur, Ries, John, Rothache, Markus, Rummel, Reiner, Shibuya, Kazuo, Sideris, Michael, Song, Y. Tony, Stammer, Detlef, Thomas, Maik, Willis, Josh, Woodworth, Philip, Hall, J., Harrison, D.E., Stammer, D., Shum, C.K., Plag, Hans-Peter, Schroter, Jens, Zlotnickie, Victor, Bender, Peter, Braun, Alexander, Cazenave, Anny, Chamber, Don, Duan, Jianbin, Emery, William, Fotopoulos, Georgia, Gouretski, Viktor, Gross, Richard, Gruber, Thomas, Guo, Junyi, Han, Guoqi, Hughes, Chris, Ishii, Masayoshi, Jayne, Steven, Johannessen, Johnny, Knudsen, Per, Kuo, Chung-Yen, Leuliette, Eric, Levitus, Sydney, Maximenko, Nikolai, Miller, Laury, Morison, James, Rashid, Harunur, Ries, John, Rothache, Markus, Rummel, Reiner, Shibuya, Kazuo, Sideris, Michael, Song, Y. Tony, Stammer, Detlef, Thomas, Maik, Willis, Josh, and Woodworth, Philip

Published
2010

121. On the postprocessing removal of correlated errors in GRACE temporal gravity field solutions

Author

Duan, X.J. (author), Guo, J.Y. (author), Shum, C.K. (author), Van der Wal, W. (author), Duan, X.J. (author), Guo, J.Y. (author), Shum, C.K. (author), and Van der Wal, W. (author)

Abstract

We revisit the empirical moving window filtering method of Swenson and Wahr (Geophys Res Lett 33:L08402, 2006) and its variants, Chambers (Geophys Res Lett 33:L17603, 2006) and Chen et al. (Geophys Res Lett 34: L13302, 2007), for reducing the correlated errors in the Stokes coefficients (SCs) of the spherical harmonic expansion of the GRACE determined monthly geopotential solutions. Based on a comparison of the three published approaches mentioned, we propose a refined approach for choosing parameters of the decorrelation filter. Our approach is based on the error pattern of the SCs in the monthly GRACE geopotential solutions. We keep a portion of the lower degree-order SCs with the smallest errors unchanged, and high-pass filter the rest using a moving window technique, with window width decreasing as the error of the SCs increases. Both the unchanged portion of SCs and the window width conform with the error pattern, and are adjustable with a parameter. Compared to the three published approaches mentioned, our unchanged portion of SCs and window width depend on both degree and order in a more complex way. We have used the trend of mass change to test various parameters toward a preferred choice for a global compromise between the removal of the correlated errors and the minimization of signal distortion., Earth Observation and Space Systems, Aerospace Engineering

Published
2009

122. Geodetic observations of ocean surface topography, ocean currents, ocean mass, and ocean volume changes

Author

Shum, C.K, Plag, Hans-Peter, Schroter, Jens, Zlotnicki, Victor, Bender, Peter, Braun, Alexander, Cazenave, Anny, Chamber, Don, Duan, Jianbin, Emery, William, Fotopoulos, Georgia, Gouretski, Viktor, Gross, Richard, Gruber, Thomas, Guo, Junyi, Han, Guoqi, Hughes, Christopher(as contributor), Ishii, Masayoshi, Jayne, Steven, Johannesen, Johnny, Knudsen, Per, Kuo, Chung-Yen, Leuliette, Eric, Levitus, Sydney, Maximenko, Nikolai, Miller, Laury, Morison, James, Rashid, Harunur, Ries, John, Rothacher, Markus, Rummel, Reiner, Shibuya, Kazuo, Sideris, Michael, Song, Y.Tony, Stammer, Detlef, Thomas, Maik, Willis, Josh, Woodworth, Philip(as contributor), Shum, C.K, Plag, Hans-Peter, Schroter, Jens, Zlotnicki, Victor, Bender, Peter, Braun, Alexander, Cazenave, Anny, Chamber, Don, Duan, Jianbin, Emery, William, Fotopoulos, Georgia, Gouretski, Viktor, Gross, Richard, Gruber, Thomas, Guo, Junyi, Han, Guoqi, Hughes, Christopher(as contributor), Ishii, Masayoshi, Jayne, Steven, Johannesen, Johnny, Knudsen, Per, Kuo, Chung-Yen, Leuliette, Eric, Levitus, Sydney, Maximenko, Nikolai, Miller, Laury, Morison, James, Rashid, Harunur, Ries, John, Rothacher, Markus, Rummel, Reiner, Shibuya, Kazuo, Sideris, Michael, Song, Y.Tony, Stammer, Detlef, Thomas, Maik, Willis, Josh, and Woodworth, Philip(as contributor)

Published
2009

125. Observations: oceanic climate change and sea level

Author

Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M., Miller, H.L., Bindoff, N.L., Willebrand, J., Artale, V., Cazenave, A., Gregory, J.M., Gulev, S., Hanawa, K., Le Quere, Corinne, Levitus, S., Nojiri, Y., Shum, C.K., Talley, L.D., Unnikrishnan, A.S., Josey, S.A., Tamisiea, M., Tsimplis, M., Woodworth, P., Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M., Miller, H.L., Bindoff, N.L., Willebrand, J., Artale, V., Cazenave, A., Gregory, J.M., Gulev, S., Hanawa, K., Le Quere, Corinne, Levitus, S., Nojiri, Y., Shum, C.K., Talley, L.D., Unnikrishnan, A.S., Josey, S.A., Tamisiea, M., Tsimplis, M., and Woodworth, P.

Published
2007

127. Regional high-resolution spatiotemporal gravity modeling from GRACE data using spherical wavelets

Author

Schmidt, M. (author), Han, S.C. (author), Kusche, J. (author), Sanchez, L. (author), Shum, C.K. (author), Schmidt, M. (author), Han, S.C. (author), Kusche, J. (author), Sanchez, L. (author), and Shum, C.K. (author)

Abstract

We determine a regional spatiotemporal gravity field over northern South America including the Amazon region using GRACE inter-satellite range-rate measurements by application of a wavelet-based multiresolution technique. A major advantage of this method is that we are able to represent the Amazon hydrological signals in form of time series of detail signals with level-dependent temporal resolution: the coarser structures generally require only ten days, whereas the medium and finer details are computable from one month of data. To this end, we employ the basic property of multiresolution representations, which is to split a signal into detail signals, each related to a specific resolution level and computable from data covering a specific part of the spectrum. Our results, which for the first time fully exploit the spatial and temporal resolutions of GRACE data in modeling Amazon hydrological fluxes, are in good agreement with hydrological models and GPS-derived height variations., Earth Observation and Space Systems, Aerospace Engineering

Published
2006
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128. Sea Level Rise - Regional and Global Trends

Author

Cazenave, A., primary, Chambers, D.P., additional, Cipollini, P., additional, Fu, L.L., additional, Hurrell, J.W., additional, Merrifield, M., additional, Nerem, S., additional, Plag, H.P., additional, Shum, C.K., additional, and Willis, Josh, additional

Published
2010
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131. Study of Tidal Dynamics, Wetland Hydrology and Permafrost Degradation Using ALOS PALSAR Interferometry

Author

Shum, C.K., Baek, Sangho, Braun, Alexander, Bassler, Michael, Dietrich, Reinhard, Kim, Jimwoo, Lee, Hyongki, and Lu, Zhong

Subjects
wetland hydrology, ocean tides, interferometry, SAR, permafrost
Abstract

The knowledge of ocean tides underneath permanently or seasonally sea ice covered ocean and ice shelves over Antarctica, is poorly known at fine-spatial scales. Significant amount of West Antarctic ice sheet melt is through the mechanism of basal melting and due to turbulent tidal mixing. We originally proposed to use the ALOS L-band PALSAR to model ocean tides underneath Antarctic ice-shelves. However, due primariy to its long repeat-orbits of 46-days, we are largely unsuccessful to construct coherent interferograms over the Filchner Ronne Ice Shelf (FRIS) using ALOS PALSAR. As a result we conducted a study using ERS-1/-2 tandem mission data to demonstrate the estimation of O1 tides over the Sulzberger ice shelf, Ross Sea, West Antarctica. We used ALOS along with satellite radar altimetry as vertical reference to construct high-resolution (ca.40 m) water level changes in vegetated wetlands, including Louisiana, Helmand River, Amazon wetland, and the St. Clair Flats wetland in the Great Lakes. We also demonstrated the use of ALOS PALSAR to measure permafrost surface subsidence over the Tibetan Plateau, and thus inferring its Active Layer Thickness (ALT) change., 形態: カラー図版あり, 形態: DVD-ROM1枚, Physical characteristics: Original contains color illustrations, Note: One DVD-ROM, 資料番号: AA0065135008, レポート番号: JAXA-SP-11-007E

Published
2011

137. Continental Water Storage Changes from GRACE Line-of-Sight Range Acceleration Measurements.

Author

Sansò, Fernando, Xu, Peiliang, Liu, Jingnan, Dermanis, Athanasios, Chen, Y., Schaffrin, B., and Shum, C.K.

Abstract

Spaceborne gravimetry such as GRACE provides a unique opportunity to observe basin-scale surface and subsurface global water storage changes with unprecedented accuracy and temporal and spatial coverages. The contemporary methodology to process GRACE data for hydrologic studies is in terms of monthly spherical harmonic geopotential solutions with a spatial resolution longer than 600-800,km (half-wavelength), after proper smoothing. Alternative methods include the direct processing of satellite-to-satellite K-Band Range (KBR) rate data and to estimate the localized gravity field, and the so-called mascon methods. In this study we estimate monthly continental water thickness changes over the Amazon Basin for one year (2003) by calculating in-situ Line-Of-Sight (LOS) gravity differences inferred by the GRACE KBR range acceleration. A regional inversion method based on Bayesian statistics is used to estimate water thickness changes from the LOS gravity difference observations. Power Spectral Density (PSD) comparison with the spherical harmonic monthly solutions at both 600 and 800 km resolutions indicates that the LOS gravity solution has more power at degree 13 or higher, implying that it is a viable technique for potentially enhancing spatial resolutions of GRACE solutions at these frequencies. [ABSTRACT FROM AUTHOR]

Published
2008
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140. An optimized hydrological drought index integrating GNSS displacement and satellite gravimetry data.

Author

Yao, Chaolong, Shum, C.K., Luo, Zhicai, Li, Qiong, Lin, Xu, Xu, Chuang, Zhang, Yu, Chen, Jingqi, Huang, Qingwen, and Chen, Yongxin

Subjects
*DROUGHT management, *DROUGHTS, *GLOBAL Positioning System, *GRAVIMETRY, *GEODETIC techniques
Abstract

• A new integrated drought index is estimated by merging GNSS and satellite gravimetry data. • The constrained method was used to form the optimal integrated drought index. • The optimized index improved the ability of drought monitoring in Southwest China. Space geodetic techniques are rapidly emerging as powerful tools for drought monitoring, including the Global Navigation Satellite System (GNSS) positioning data, and the gravimetric data from Gravity Recovery And Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) satellite missions. However, while GNSS-based 3D displacements have high temporal resolution, they are impacted by diverse local effects especially for tectonically active regions. Satellite gravimetry derived terrestrial water storage changes (ΔTWS) are continuous in temporal sampling, however, at much coarser spatial resolutions, and there are systematic noise and a large 11-month data gap between GRACE and GRACE-FO observations. Here for the first time, we developed an Optimized GNSS/GRACE/GRACE-FO Hydrological Drought Index (OGHDI), by optimally combining two drought indices derived from GNSS vertical displacements (VDs) and GRACE/GRACE-FO ΔTWS, to better characterize decadal evolution of droughts over Southwest China, 2011–2020. The optimal relative weights of the two drought indices are determined through maximizing the correlations with the Composite Index (CI) commonly used in the study region. Then OGHDI is compared to the self-calibrating Palmer Drought Severity Index (scPDSI). The results show that VDs agree well with ΔTWS at most of the 30 analyzed GNSS sites, with a mean correlation of −0.44. Compared to the drought index developed using only GNSS data, the optimized technique improved the OGHDI-scPDSI correlations at 90% (27 sites) of the sites, with the highest correlation reaches 0.73. Further, more significant improvement is found at the regional scale than at individual sites, and the regional mean OGHDI-CI and OGHDI-scPDSI correlations increase from 0.37 to 0.57 and from 0.42 to 0.68, respectively. All drought indices show that Southwest China experienced two sustained and excessive drought periods from 2011 to mid-2013, and after 2019. We conclude that the novel integration of two distinct contemporary and complemenatry geodetic datasets, GNSS and GRACE/GRACE-FO, improved the ability of drought monitoring in Southwest China. [ABSTRACT FROM AUTHOR]

Published
2022
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142. A possible interrelation between Earth rotation and climatic variability at decadal time-scale

Author

Zotov, Leonid, Bizouard, C., and Shum, C.K.

Abstract

Using multichannel singular spectrum analysis (MSSA) we decomposed climatic time series into principal components, and compared them with Earth rotation parameters. The global warming trends were initially subtracted. Similar quasi 60 and 20 year periodic oscillations have been found in the global mean Earth temperature anomaly (HadCRUT4) and global mean sea level (GMSL). Similar cycles were also found in Earth rotation variation. Over the last 160 years multi-decadal change of Earth's rotation velocity is correlated with the 60-year temperature anomaly, and Chandler wobble envelope reproduces the form of the 60-year oscillation noticed in GMSL. The quasi 20-year oscillation observed in GMSL is correlated with the Chandler wobble excitation. So, we assume that Earth's rotation and climate indexes are connected. Despite of all the clues hinting this connection, no sound conclusion can be done as far as ocean circulation modelling is not able to correctly catch angular momentum of the oscillatory modes.

Published
2016
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144. List of Contributors

Author

Abayomi, E.A., AghaKouchak, A., Ahmed, M., Akanda, A.S., Aneja, V.P., Annesi Maesano, I., Archer, S.R., Ayivor, J.S., Azad Hossain, A.K.M., Baldocchi, D., Barnard, L.T., Barros, A.P., Barthelmie, R.J., Bates, P., Beamon, B.M., Becker, D., Becker, R., Beckingham, A., Belhouchette, H., Best, K.M., Bestelmeyer, B.T., Betman, E., Blenckner, T., Blöschl, G., Boisvenue, C., Bolton, S., Borga, M., Booker, F., Borma, L.S., Bornstein, B., Brooks, M.L., Brown, J., Buckley, R., Burian, S.J., Burkle, L., Butler, C.D., Cardoso, M.F., Cecchi, L., Chapin, F.S., III, Chen, J., Chhetri, N., Chouinard, K., Christie, D., Chuluun, T., Cinderich, A.B., Clausen, N.-E., Cloke, H., Compton, J.E., Comrie, A.C., Convertino, M., Côté, I.M., Cull, T., Darko, D., Darling, E.S., Davis, M.A., Ddumba, S.D., De Felice, M., Degu, A.M., Dennis, R., Diaz, J.H., Doubler, D., D’Amato, G., Eilerts, G., Elmore, R.W., Emery, N., Fang, C.M., Fekete, B.M., Fong, L.P., Funk, C., Gall, H.E., Galvin, K.A., Gao, X., Gebregiorgis, A.S., Ghebreegziabhe, A.T., Giebel, G., Gimblett, H.R., Goldstein, J.H., Gonzalez Cruz, J., Gordon, C., Groisman, P.Y., Hajat, S., Hanna, E., Hanna, L., Hashizume, M., Havstad, K.M., He, Y., He, Z., Hill, B., Hoffman, M.T., Holcombe, T., Hossain, F., Hoverman, J.T., Hsu, K., Husak, G., Islam, S., Jha, S., Johnson, P.T.J., Joshi, A.K., Jules-Plag, S., Jutla, A.S., Kafatos, M., Kalyanapu, A.J., Karlsson, E.M., Katsman, C., Kiker, G.A., Kim, S.-H., Kimmerer, W., Kittel, T.G.F., Kjellstrom, T., Klein Tank, A., Knight, R.W., Koranteng, S., Kovats, S., Kremen, C., Lal, R., Lammers, R.B., Lange, M.A., Larsen, S.G., Lawler, J.J., Lemke, B., Lemos, M.C., Lenderink, G., LePoire, D.J., Le Quesne, C., Linkov, I., Liu, Z., Logan, L.H., López-Hoffman, L., Lowe, C., Luckman, B.H., Mahbubur Rahman, S.M., Mahiny, A.S., Manful, D., Mase, A.S., Masiokas, M.H., Mauget, S., Mensah, A.M., Mihaltcheva, S., Milewski, A., Miller, C.A., Mishra, V., Mitra, C., Modak, P., Moges, S.A., Mohanty, U.C., Molina, Y., Molloy, S.L., Monger, H.C., Montaña, E., Montanari, A., Munoz-Carpena, R., Nardi, F., Niiranen, S., Nikolic, J., Nishat, B., Niu, J., Niyogi, D., Nobre, C.A., Nukpezah, D., Ofori, B.D., Ojima, D.S., Okin, G.S., Olden, J.D., Otieno, F.O., Owens, P., Pabi, O., Papalexopoulos, A., Pappenberger, F., Park, J., Parkes, B., Paull, S.H., Pearce, T., Penna, D., Perdinan, Perry-Hill, R., Peters, D.P.C., Picon, R., Pillich, J., Pinson, P., Plag, H.-P., Pollyea, A.M., Powers, W., Prokopy, L.S., Pryor, S.C., Rango, A., Rao, M., Rao, P.S.C., Rashid, H., Rawade, Y.A., Ray, D.K., Renaud, A.L., Rodell, M., Rosenberg, A.A., Rowland, J., Rudek, J., Running, S.W., Ruti, P.M., Sailor, D.J., Sala, O.E., Samaras, Z., Sarafoglou, N., Schmitz, O.J., Scholes, R.J., Scott, D., Seastedt, T.R., Sequera, P., Shah-Newaz, S.M., Shakeela, A., Shepherd, J.M., Shiklomanov, A.I., Shinde, S.S., Shum, C.K., Siddique-E-Akbor, A.H.M., Smart, K., Smit, B., Smith, M.D., Soper, E.J., Sorooshian, S., Souissi, I., Spencer, B., Sreckovic, G., Steiger, R., Stohlgren, T.J., Sturchio, N., Suding, K.N., Sultan, M., Sun, L., Swain, D.K., Taub, D.R., te Linde, A., Temani, N., Thompson, L., Todd, S.W., Troccolli, A., Tsikalakis, A.G., Tuinstra, M.R., Tweedie, C.E., Tweneboah-Lawson, E., Tylianakis, J.M., Vaddella, V., van den Hurk, B., Venugopal, V., Verdin, J., Viglione, A., Villalba, R., Vincent, K., Vivoni, E.R., Voss, J.G., Vouitsis, I., Vrontisi, Z.N., Wahr, J., Walsh, T., Wang, X., Weaver, M.J., Wetterhall, F., Winkler, J.A., Woldemichael, A.T., Wood, A.W., Yan, E., Yigzaw, W., Yirenya-Tawiah, D., Young, D.R., Zaman, A.M., Zavalloni, C., Zhang, W., and Zolina, O.G.

Published
2013
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147. Absolute Calibration of Jason Radar Altimeters from GPS Kinematic Campaigns Over Lake Issykkul.

Author

Crétaux, J.-F., Calmant, S., Romanovski, V., Perosanz, F., Tashbaeva, S., Bonnefond, P., Moreira, D., Shum, C.K., Nino, F., Bergé-Nguyen, M., Fleury, S., Gegout, P., Rio, R.Abarca Del, and Maisongrande, P.

Subjects
ALTITUDE measurements, ELECTRONIC pulse techniques, TELECOMMUNICATION satellites, ALTIMETERS, PHYSICAL measurements
Abstract

This study presents results of calibration/validation (C/V) of Jason-1 and Jason-2 satellite altimeters over Lake Issykkul located in Kyrgyzstan, which was chosen as a dedicated radar altimetry C/V site in 2004. The objectives here are to estimate absolute altimeter biases and to quantify the altimetry instrument error budgets for lakes studies, including errors associated with the atmosphere media delay corrections of the radar signal, and with the different retracking mode used over “nonocean” surface. The C/V is conducted using various equipments, for example, GPS local network, moving GPS along the satellites tracks over the Lake Issykkul, in situ level gauges and weather stations. The absolute bias obtained for Jason-1 and Jason-2 from field campaigns conducted in 2008, 2009 and 2010 are 96 ± 40 mm and 162 ± 42 mm, respectively. The bias calculated for Jason-1 is in close agreement with estimates done at other dedicated C/V sites in the ocean, but the Jason-2 bias still differs by 1–2 cm with ocean C/V estimates. The relative bias (Jason-2 minus Jason-1) deduced from measurements during the tandem mission is estimated at 81 ± 10 mm. The accuracy of Jason-1 and Jason-2 for the determination of the lake level variations as compared to the historical in situ gauges of the Lake Issykkul is 33 and 31 mm RMS, respectively. The bias between the two modes of retracking available on Jason-2 Geophysical Data Records (GDRs) has been estimated over the two first years of Jason-2 data over the Lake Issykkul. We found an average value of 234 ± 40 mm, which is in good agreement with results obtained in a previous study on the Envisat satellite (Crétaux et al. 2009). Lake level studies using Jason-2 or Envisat must therefore take this relative bias into account if both retracked altimetry heights are used. [ABSTRACT FROM PUBLISHER]

Published
2011
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148. Regional Validation of Jason-2 Dual-Frequency Ionosphere Delays.

Author

Tseng, Kuo-Hsin, Shum, C.K., Yi, Yuchan, Dai, Chunli, Lee, Hyongki, Bilitza, Dieter, Komjathy, Attila, Kuo, C.Y., Ping, Jinsong, and Schmidt, Michael

Subjects
*IONOSPHERE, *ELECTRONS, *GEOPHYSICS, *GEOSTATIONARY satellites, *MARINE sciences
Abstract

In this study, we validated the Jason-2 (J2) dual-frequency ionosphere delay measurements in terms of vertical total electron content (VTEC) in the Geophysical Data Record (GDR) with the coarse resolution JPL Global Ionospheric Maps (GIM), the regional ionospheric maps generated by the Crustal Motion Observation Network of China (CMONOC), and the Jason-1 (J1) interleaved tandem mission (with J2) ionosphere delay measurements. The estimates of the relative biases and their uncertainties (95% confidence, in TEC units) for various comparison cases with different data spans and regions are (1) J2-GIM: -3.07 ± 0.18 TECu (or 6.75 ± 0.40 mm in the range delay), (2) J2-CMONOC: -2.87 ± 0.38 TECu (6.31 ± 0.84 mm), (3) J1-GIM: -0.19 ± 0.18 TECu (0.42 ± 0.40 mm), and (4) J2-J1 via double-differencing, that is, (J2-GIM)-(J1-GIM): -2.88 ± 0.26 TECu (6.34 ± 0.57 mm). The scatter (RMS, about the mean differences) between J2 and GIM, CMONOC, or J1 is about 3∼8 TECu (6.6∼17.6 mm). We conclude that the results from global and regional analysis are consistent and that the J2 ionosphere delay is about 6∼10 mm (95% confidence) shorter than the delay computed by GIM, J1, or the regional model. [ABSTRACT FROM AUTHOR]

Published
2010
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149. Validation of Jason-2 Altimeter Data by Waveform Retracking over California Coastal Ocean.

Author

Lee, Hyongki, Shum, C.K., Emery, William, Calmant, Stephane, Deng, Xiaoli, Kuo, Chung-Yen, Roesler, Carolyn, and Yi, Yuchan

Subjects
*GEOSTATIONARY satellites, *OCEANOGRAPHY equipment, *ALTIMETERS, *OCEAN
Abstract

We validated Jason-2 satellite altimeter Sensor Geophysical Data Records (SGDR) by retracking 20-Hz radar waveforms over the California coastal ocean using cycles 7-34, corresponding to September 2008-June 2009. The performance of the ocean, ice, threshold, and modified threshold retrackers are examined using a reference geoid based on Earth Gravitational Model 2008 (EGM08). Over the shallow ocean (depth < 200 m), the modified threshold retracker, which is developed for noisy waveforms with preleading edge bump, outperforms the other retrackers. It is also shown that retracking can improve the precision of sea surface heights (SSHs) for areas beyond 2-5 km from the shore. Although the ocean retracker generally performs well over the deep ocean (depth > 200 m), the ocean-retracked SSHs from some of the cycles are found to be less precise when the waveforms do not conform to the Brown ocean model. We found that the retrackers developed for nonocean surfaces can improve the noisy ocean-retracked SSHs. Among the retrackers tested here, the ice retracker overall provides the most precise SSH estimates over the deep ocean in average using cycles 7-34 in the study region. [ABSTRACT FROM AUTHOR]

Published
2010
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150. Lake Surface Height Calibration of Jason-1 and Jason-2 Over the Great Lakes.

Author

Cheng, Kai-Chien, Kuo, Chung-Yen, Tseng, Hong-Zeng, Yi, Yuchan, and Shum, C.K.

Subjects
ALTIMETERS, RADAR, GEOPHYSICS, CALIBRATION
Abstract

This study presents results of Jason-1 (J1) and Jason-2 (J2) radar altimetry absolute calibration (cal/val) over the Marblehead lake water level gauge, with an aid of a GPS buoy, in Lake Erie, the Great Lakes, in North America. The altimeter bias is estimated using the height difference between the altimeter lake surface height and the in situ data in each altimeter 10-day repeat cycle. The altimeter bias estimates for J1 are 81 ± 2 and 70 ± 2 mm for Geophysical Data Record (GDR) Versions 'B' and 'C', respectively, and 148 ± 5 mm (GDR) and 147 ± 7 mm (IGDR) for J2, respectively. The bias estimates are slightly smaller compared with estimates at other dedicated calibration sites such as the Harvest Platform, the Corsica Site, and the Bass Strait site due in part to the effect of the sea state bias. The J2-to-J1 relative bias determined in the tandem mode over Lake Erie is 84 ± 28 mm, which agrees well with the results from the global analysis and the dedicated sites aforementioned. [ABSTRACT FROM AUTHOR]

Published
2010
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