scholarly journals The Rapid and Steady Mass Loss of the Patagonian Icefields throughout the GRACE Era: 2002–2017

2019 ◽  
Vol 11 (8) ◽  
pp. 909 ◽  
Author(s):  
Andreas Richter ◽  
Andreas Groh ◽  
Martin Horwath ◽  
Erik Ivins ◽  
Eric Marderwald ◽  
...  
Keyword(s):  
Time Series ◽  
Mass Loss ◽  
A Priori ◽  
Global Navigation Satellite Systems ◽  
Mass Change ◽  
Satellite Systems ◽  
Isostatic Adjustment ◽  
Global Navigation Satellite ◽  
Gravity Recovery ◽  
The Antarctic

We use the complete gravity recovery and climate experiment (GRACE) Level-2 monthly time series to derive the ice mass changes of the Patagonian Icefields (Southern Andes). The glacial isostatic adjustment is accounted for by a regional model that is constrained by global navigation satellite systems (GNSS) uplift observations. Further corrections are applied concerning the effect of mass variations in the ocean, in the continental water storage, and of the Antarctic ice sheet. The 161 monthly GRACE gravity field solutions are inverted in the spatial domain through the adjustment of scaling factors applied to a-priori ice mass change patterns based on published remote sensing results for the Southern and Northern Patagonian Icefields, respectively. We infer an ice mass change rate of −24.4 ± 4.7 Gt/a for the Patagonian Icefields between April 2002 and June 2017, which corresponds to a contribution to the eustatic sea level rise of 0.067 ± 0.013 mm/a. Our time series of monthly ice mass changes reveals no indication for an acceleration in ice mass loss. We find indications that the Northern Patagonian Icefield contributes more to the integral ice loss than previously assumed.

scholarly journals Analysis of October 23 (Mw 7.2) and November 9 (Mw 5.6), 2011 Van Earthquakes Using Long-Term GNSS Time Series

2017 ◽  
Vol 21 (3) ◽  
pp. 147-156 ◽  
Author(s):  
Ibrahim Tiryakioglu ◽  
Hakan Yavasoglu ◽  
Mehmet Ali Ugur Ugur ◽  
Caglar Ozkaymak ◽  
Mustafa Yilmaz ◽  
...  
Keyword(s):  
Time Series ◽  
Hanging Wall ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Before And After ◽  
Wall Deformation ◽  
Van Earthquakes ◽  
Global Navigation Satellite ◽  
Seismic Deformation ◽  
Gnss Data

The eastern Anatolia provides one of the best examples of an area of rapid deformation and intense contraction that is the consequence of an active continental collision between the Arabian and Eurasian plates leading to large and devastating earthquakes. The latest evidence of the active tectonism in the region is revealed by two remarkable seismic events; Van-Tabanli (Mw 7.2, October 23, 2011) and Van-Edremit (Mw 5.6, November 9, 2011) earthquakes. The study of the earthquake cycle and observation of geodetic and seismic deformation in this region is very important to hazard assessments. In this study, the inter-seismic, co-seismic, and post-seismic movements caused by the above-mentioned earthquakes were investigated using the time series of 2300 days of Global Navigation Satellite Systems (GNSS) observations of the local stations selected from the network of the Continuously Operating Reference Stations, Turkey (CORS-TR). For the inter-seismic period, approximately 1100 daily data were obtained from 21 CORS-TR stations (prior to the earthquakes between October 1, 2008 and October 23, 2011) and evaluated using the GAMIT/GLOBK software. The behaviour of these stations was investigated by processing 1 Hz data from the GNSS stations during the earthquakes on the GAMIT/TRACK software. In addition to October 23 and November 9, the GNSS data on one day before and after the earthquakes was assessed to determine co-seismic deformations. During the October 23 earthquake, hanging-wall deformation of about 60 mm was detected in the SW direction at the MURA station. However, at the VAAN station, deformation of 200 mm (value predicted by time series) was observed in the footwall block in the NW direction. There were not any significant changes at the stations during the November 9 earthquake. For the post-seismic period, the GNSS data from 2012 to 2015 was evaluated. According to the observations, post-seismic deformation continued at the stations close to the epicenter of the earthquake.

scholarly journals Improved GNSS-R bi-static altimetry and independent digital elevation models of Greenland and Antarctica from TechDemoSat-1

2020 ◽  
Vol 14 (6) ◽  
pp. 1909-1917 ◽  
Author(s):  
Jessica Cartwright ◽  
Christopher J. Banks ◽  
Meric Srokosz
Keyword(s):  
Digital Elevation Models ◽  
Global Navigation Satellite Systems ◽  
Glacial Ice ◽  
Satellite Systems ◽  
Digital Elevation ◽  
Future Potential ◽  
The Uk ◽  
Global Navigation Satellite ◽  
The Antarctic ◽  
Mean Square Errors

Abstract. Improved digital elevation models (DEMs) of the Antarctic and Greenland ice sheets are presented, which have been derived from Global Navigation Satellite Systems-Reflectometry (GNSS-R). This builds on a previous study (Cartwright et al., 2018) using GNSS-R to derive an Antarctic DEM but uses improved processing and an additional 13 months of measurements, totalling 46 months of data from the UK TechDemoSat-1 satellite. A median bias of under 10 m and root-mean-square errors (RMSEs) of under 53 m for the Antarctic and 166 m for Greenland are obtained, as compared to existing DEMs. The results represent, compared to the earlier study, a halving of the median bias to 9 m, an improvement in coverage of 18 %, and a 4 times higher spatial resolution (now gridded at 25 km). In addition, these are the first published satellite altimetry measurements of the region surrounding the South Pole. Comparisons south of 88∘ S yield RMSEs of less than 33 m when compared to NASA's Operation IceBridge measurements. Differences between DEMs are explored, the limitations of the technique are noted, and the future potential of GNSS-R for glacial ice studies is discussed.

Application of Computer Modelling in Adaptive Compensation of Interferences on Global Navigation Satellite Systems

2019 ◽  
pp. 339-380 ◽  
Author(s):  
Valerian Shvets ◽  
Svitlana Ilnytska ◽  
Oleksandr Kutsenko
Keyword(s):  
A Priori ◽  
Inverse Correlation ◽  
Global Navigation Satellite Systems ◽  
Navigation Satellite ◽  
A Priori Information ◽  
Satellite Systems ◽  
Useful Signal ◽  
Global Navigation ◽  
Priori Information ◽  
Global Navigation Satellite

Modern society is characterized by the increased use of global navigation satellite systems (GNSS), which is inseparably linked with the interference immunity ensurance. The most effective way to protect against interferences is an introduction into the receiver structure of adaptive interference compensators. However, the most of proposed methods have been designed for radiolocation and communication and use a priori information about the transmitted signal. Since as structure of GNSS signal differs from the radar and communication systems, GNSS does not know the time-frequency structure of the useful signal in advance, which excludes the possibility of using a number of widely known methods. In this chapter, the authors propose a method, which does not use a priori information about a useful signal, and a new direct method for calculating the inverse correlation matrix of interference in adaptive antennas of interferences compensators.

scholarly journals Decadal variations in atmospheric water vapor time series estimated using ground-based GNSS

2016 ◽  
Author(s):  
Fadwa Alshawaf ◽  
Galina Dick ◽  
Stefan Heise ◽  
Tzvetan Simeonov ◽  
Sibylle Vey ◽  
...  
Keyword(s):  
Time Series ◽  
Water Vapor ◽  
Linear Trend ◽  
Precipitable Water ◽  
The Other ◽  
Global Navigation Satellite Systems ◽  
Positive Trend ◽  
Satellite Systems ◽  
Decadal Variations ◽  
Global Navigation Satellite

Abstract. Ground-based GNSS (Global Navigation Satellite Systems) have efficiently been used since the 1990s as a meteorological observing system. Recently scientists used GNSS time series of precipitable water vapor (PWV) for climate research. In this work, we use time series from GNSS, European Center for Medium-Range Weather Forecasts Reanalysis (ERA-Interim) data, and meteorological measurements to evaluate climate evolution in Central Europe. The assessment of climate change requires monitoring of different atmospheric variables such as temperature, PWV, precipitation, and snow cover. PWV time series were obtained by three methods: 1) estimated from ground-based GNSS observations using the method of precise point positioning, 2) inferred from ERA-Interim data, and 3) determined based on daily surface measurements of temperature and relative humidity. The other variables are available from surface meteorological stations or received from ERA-Interim. The PWV trend component estimated from GNSS data strongly correlates with that estimated from the other data sets. The linear trend is estimated by straight line fitting over 30 years of seasonally-adjusted PWV time series obtained using meteorological measurements. The results show a positive trend in the PWV time series at more than 60 GNSS sites with an increase of 0.3–0.6 mm/decade. In this paper, we compare the results of three stations. The temporal increment of the PWV correlates with the temporal increase in the temperature levels.

scholarly journals Using satellite laser ranging to measure ice mass change in Greenland and Antarctica

2018 ◽  
Vol 12 (1) ◽  
pp. 71-79 ◽  
Author(s):  
Jennifer A. Bonin ◽  
Don P. Chambers ◽  
Minkang Cheng
Keyword(s):  
Time Series ◽  
Mass Loss ◽  
Time Frame ◽  
Satellite Laser Ranging ◽  
Mass Change ◽  
Laser Ranging ◽  
Data Types ◽  
Gravity Recovery ◽  
Loss Estimate

Abstract. A least squares inversion of satellite laser ranging (SLR) data over Greenland and Antarctica could extend gravimetry-based estimates of mass loss back to the early 1990s and fill any future gap between the current Gravity Recovery and Climate Experiment (GRACE) and the future GRACE Follow-On mission. The results of a simulation suggest that, while separating the mass change between Greenland and Antarctica is not possible at the limited spatial resolution of the SLR data, estimating the total combined mass change of the two areas is feasible. When the method is applied to real SLR and GRACE gravity series, we find significantly different estimates of inverted mass loss. There are large, unpredictable, interannual differences between the two inverted data types, making us conclude that the current 5×5 spherical harmonic SLR series cannot be used to stand in for GRACE. However, a comparison with the longer IMBIE time series suggests that on a 20-year time frame, the inverted SLR series' interannual excursions may average out, and the long-term mass loss estimate may be reasonable.

Sea Ice Classification and Altimetry using Grazing Angle Reflected GNSS Signals Measured by Spire’s Nanosatellite Constellation

2021 ◽  
Author(s):  
Jessica Cartwright ◽  
Vu Nguyen ◽  
Philip Jales ◽  
Oleguer Nogues-Correig ◽  
Takayuki Yuasa ◽  
...  
Keyword(s):  
Sea Ice ◽  
Weather Prediction ◽  
Grazing Angle ◽  
Surface Characteristics ◽  
Global Navigation Satellite Systems ◽  
Ice Age ◽  
The Arctic ◽  
Satellite Systems ◽  
Global Navigation Satellite ◽  
The Antarctic

<p>Global Navigation Satellite Systems-Reflectometry (GNSS-R) offers novel observations over the cryosphere with the use of reflected navigation signals (eg. GPS or Galileo) as signals of opportunity. This technique has the potential for higher resolution measurements over sea ice than routinely acquired by passive microwave systems with a footprint of around 5 km2 and is much lower in power consumption, mass and therefore cost. Here we present sea ice classification and altimetry as observed at grazing angles by Spire’s Radio Occultation (RO) Satellite constellation, repurposed for GNSS-R.</p><p>The Spire RO constellation of 37 operational satellites (and growing) is relied upon to support critical numerical weather prediction and has been collecting GNSS signals as they refract through the atmosphere. The reprogramming of these satellites to receive signals reflected at grazing angle allows these signals to instead inform on Earth surface characteristics. From smooth surfaces, these signals are phase coherent at L-Band frequencies (~19 - 24 cm wavelength) and allow the detection of the roughness of the sea ice in addition to the height of the surface to several centimetres of precision. Three months of these operational sea ice detection and classification products are presented from Spring of 2020; with ice extent in agreement with external passive and active sources to around 98% in the Antarctic and 94% in the Arctic, and ice age classification (First Year/Multi-Year) agreeing in the Arctic to around 70%. First results are shown for the potential to detect other ice characteristics such as the Antarctic Marginal Ice Zone extent and floe size / type.</p>

scholarly journals Homogenized Time Series of the Atmospheric Water Vapor Content Obtained from the GNSS Reprocessed Data

2016 ◽  
Vol 29 (7) ◽  
pp. 2443-2456 ◽  
Author(s):  
T. Ning ◽  
J. Wickert ◽  
Z. Deng ◽  
S. Heise ◽  
G. Dick ◽  
...  
Keyword(s):  
Time Series ◽  
Water Vapor ◽  
Global Scale ◽  
Global Navigation Satellite Systems ◽  
Radiosonde Data ◽  
Gps Data ◽  
Satellite Systems ◽  
Weather Forecasts ◽  
The Difference ◽  
Global Navigation Satellite

Abstract The potential temporal shifts in the integrated water vapor (IWV) time series obtained from reprocessed data acquired from global navigation satellite systems (GNSS) were comprehensively investigated. A statistical test, the penalized maximal t test modified to account for first-order autoregressive noise in time series (PMTred), was used to identify the possible mean shifts (changepoints) in the time series of the difference between the GPS IWV and the IWV obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) data. The approach allows for identification of the changepoints not only in the GPS IWV time series but also in ERA-Interim. The IWV difference time series formed for 101 GPS sites were tested, where 47 of them were found to contain in total 62 changepoints. The results indicate that 45 detected changepoints were due to the inconsistencies in the GPS IWV time series, and 16 were related to ERA-Interim, while one point was left unverified. After the correction of the mean shifts for the GPS data, an improved consistency in the IWV trends is evident between nearby sites, while a better agreement is seen between the trends from the GPS and ERA-Interim data on a global scale. In addition, the IWV trends estimated for 47 GPS sites were compared to the corresponding IWV trends obtained from nearby homogenized radiosonde data. The correlation coefficient of the trends increases significantly by 38% after using the homogenized GPS data.

scholarly journals Intersystem Bias in GPS, GLONASS, Galileo, BDS-3, and BDS-2 Integrated SPP: Characteristics and Performance Enhancement as a Priori Constraints

2021 ◽  
Vol 13 (22) ◽  
pp. 4650
Author(s):  
Lin Pan ◽  
Zhehao Zhang ◽  
Wenkun Yu ◽  
Wujiao Dai
Keyword(s):  
Performance Enhancement ◽  
Low Cost ◽  
Single Point ◽  
A Priori ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Term Stability ◽  
Long Term Stability ◽  
And Performance ◽  
Global Navigation Satellite

Global navigation satellite systems (GNSSs) have been booming in recent years, and the space segment of all four of the GNSSs, including BDS (BDS-3/BDS-2), Galileo, GPS, and GLONASS, has almost been fully deployed at present. The single point positioning (SPP) technology, which is widely used in satellite navigation and low-accuracy positioning, can benefit from the multi-GNSS integration, but the additional intersystem bias (ISB) parameters should be introduced to ensure the compatibility among different GNSSs. In this study, the ISB estimates derived from four-system integrated SPP are carefully characterized, and the performance enhancement attributed to a priori ISB constraints by prediction for position solutions under open sky and constrained visibility environments is rigorously evaluated. The results indicate that the ISB between BDS-3 and BDS-2 cannot be ignored. The daily ISBs show step changes when encountering the replacement of receiver types, while it is not the case for the receiver firmware versions. The daily ISBs are roughly consistent for the stations equipped with the same type of receivers. The short-term stability of epochwise ISBs for GLONASS, Galileo, BDS-2, and BDS-3 with respect to GPS can be 2.335, 1.262, 1.741, and 1.532 ns, respectively, whereas the corresponding long-term stability for daily ISBs can be 1.258, 1.288, 2.713, and 2.566 ns, respectively. The single-day prediction accuracy of daily ISBs for GLONASS, Galileo, BDS-2, and BDS-3 with respect to GPS can be 1.055, 0.640, 1.242, and 0.849 ns, respectively. The improvements on positioning accuracy after introducing a priori ISB constraints can be over 20% at an elevation mask of 40° and 50° with a time span of ISB prediction of a day. As to the availability, it is only 64.0% for traditional four-system SPP under a cutoff elevation of 50°, while the corresponding availability is increased to approximately 90.0% after considering a priori ISB constraints. For completeness, the characteristics of ISBs estimated with the low-cost u-blox M8T receiver and the Xiaomi Mi8 smartphone as well as the contribution of a priori ISB constraints to the multisystem SPP solutions with these devices are also investigated.

scholarly journals Using Satellite Laser Ranging to measure ice mass change in Greenland and Antarctica

2017 ◽  
Author(s):  
Jennifer A. Bonin ◽  
Don P. Chambers ◽  
Minkang Cheng
Keyword(s):  
Time Series ◽  
Mass Loss ◽  
Time Frame ◽  
Satellite Laser Ranging ◽  
Mass Change ◽  
Laser Ranging ◽  
Data Types ◽  
Gravity Recovery ◽  
Loss Estimate

Abstract. A least squares inversion of Satellite Laser Ranging (SLR) data over Greenland and Antarctica could extend gravimetry-based estimates of mass loss back to the early 1990s, and fill any future gap between the current Gravity Recovery and Climate Experiment (GRACE) and the future GRACE Follow-On mission. The results of a simulation suggest that, while separating the mass change between Greenland and Antarctica is not possible at the limited spatial resolution of the SLR data, estimating the total combined mass change of the two areas is feasible. When the method is applied to real SLR and GRACE gravity series, we find significantly different estimates of inverted mass loss. There are large, unpredictable, interannual differences between the two inverted data types, making us conclude that the current 5 × 5 spherical harmonic SLR series cannot be used to stand in for GRACE. However, a comparison with the longer IMBIE time-series suggests that on a 20-year time-frame, the inverted SLR series' interannual excursions may average out, and the long-term mass loss estimate be reasonable.

scholarly journals Improved GNSS-R bi-static altimetry and independent DEMs of Greenland and Antarctica from TechDemoSat-1

2020 ◽  
Author(s):  
Jessica Cartwright ◽  
Christopher J. Banks ◽  
Meric Srokosz
Keyword(s):  
Satellite Altimetry ◽  
Ice Sheets ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Digital Elevation ◽  
Future Potential ◽  
The Uk ◽  
Global Navigation Satellite ◽  
The Antarctic ◽  
Rms Errors

Abstract. Improved Digital Elevation Models (DEMs) of the Antarctic and Greenland Ice Sheets are presented, derived from Global Navigation Satellite Systems-Reflectometry (GNSS-R). This builds on a previous study (Cartwright et al., 2018) using GNSS-R to derive an Antarctic DEM but uses improved processing and an additional 13 months of measurements, totalling 46 months of data from the UK TechDemoSat-1 satellite. A median bias of under 10 m and root-mean-square (RMS) errors of under 53 m for the Antarctic and 166 m for Greenland are obtained, as compared to existing DEMs. The results represent, compared to the earlier study, a halving of the median bias to 9 m, an improvement in coverage of 18 %, and a four times higher spatial resolution (now gridded at 25 km). In addition, these are the first published satellite altimetry measurements of the region surrounding the South Pole. Comparisons south of 88° S yield RMS errors of less than 33 m when compared to NASA’s Operation IceBridge measurements. Differences between DEMs are explored and the future potential for ice sheet monitoring by this technique is noted.

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