GLACIER VOLUME CHANGE ESTIMATION USING TIME SERIES OF IMPROVED ASTER DEMS

2016 ◽

Vol XLI-B8 ◽

pp. 489-494

Author(s):

Luc Girod ◽

Christopher Nuth ◽

Andreas Kääb

Keyword(s):

Climate Change ◽

Time Series ◽

Volume Change ◽

Thermal Emission ◽

Aster Data ◽

Rational Polynomial ◽

The Cross ◽

Cross Track ◽

Along Track

Volume change data is critical to the understanding of glacier response to climate change. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system embarked on the Terra (EOS AM-1) satellite has been a unique source of systematic stereoscopic images covering the whole globe at 15m resolution and at a consistent quality for over 15 years. While satellite stereo sensors with significantly improved radiometric and spatial resolution are available to date, the potential of ASTER data lies in its long consistent time series that is unrivaled, though not fully exploited for change analysis due to lack of data accuracy and precision. Here, we developed an improved method for ASTER DEM generation and implemented it in the open source photogrammetric library and software suite MicMac. The method relies on the computation of a rational polynomial coefficients (RPC) model and the detection and correction of cross-track sensor jitter in order to compute DEMs. ASTER data are strongly affected by attitude jitter, mainly of approximately 4 km and 30 km wavelength, and improving the generation of ASTER DEMs requires removal of this effect. Our sensor modeling does not require ground control points and allows thus potentially for the automatic processing of large data volumes. <br><br> As a proof of concept, we chose a set of glaciers with reference DEMs available to assess the quality of our measurements. We use time series of ASTER scenes from which we extracted DEMs with a ground sampling distance of 15m. Our method directly measures and accounts for the cross-track component of jitter so that the resulting DEMs are not contaminated by this process. Since the along-track component of jitter has the same direction as the stereo parallaxes, the two cannot be separated and the elevations extracted are thus contaminated by along-track jitter. Initial tests reveal no clear relation between the cross-track and along-track components so that the latter seems not to be easily modeled analytically from the first one. We thus remove the remaining along-track jitter effects in the DEMs statistically through temporal DEM stacks to finally compute the glacier volume changes over time. Our method yields cleaner and spatially more complete elevation data, which also proved to be more in accordance to reference DEMs, compared to NASA’s AST14DMO DEM standard products. <br><br> The quality of the demonstrated measurements promises to further unlock the underused potential of ASTER DEMs for glacier volume change time series on a global scale. The data produced by our method will help to better understand the response of glaciers to climate change and their influence on runoff and sea level.

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IMPROVEMENT OF DEM GENERATION FROM ASTER IMAGES USING SATELLITE JITTER ESTIMATION AND OPEN SOURCE IMPLEMENTATION

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprsarchives-xl-1-w5-249-2015 ◽

2015 ◽

Vol XL-1-W5 ◽

pp. 249-253 ◽

Cited By ~ 2

Author(s):

L. Girod ◽

C. Nuth ◽

A. Kääb

Keyword(s):

Open Source ◽

Thermal Emission ◽

Ground Truth ◽

Three Dimensions ◽

Glacier Mass Balance ◽

Mountain Glacier ◽

Ground Control Points ◽

Rational Polynomial ◽

Cross Track

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system embarked on the Terra (EOS AM-1) satellite has been a source of stereoscopic images covering the whole globe at a 15m resolution at a consistent quality for over 15 years. The potential of this data in terms of geomorphological analysis and change detection in three dimensions is unrivaled and needs to be exploited. However, the quality of the DEMs and ortho-images currently delivered by NASA (ASTER DMO products) is often of insufficient quality for a number of applications such as mountain glacier mass balance. For this study, the use of Ground Control Points (GCPs) or of other ground truth was rejected due to the global “big data” type of processing that we hope to perform on the ASTER archive. We have therefore developed a tool to compute Rational Polynomial Coefficient (RPC) models from the ASTER metadata and a method improving the quality of the matching by identifying and correcting jitter induced cross-track parallax errors. Our method outputs more accurate DEMs with less unmatched areas and reduced overall noise. The algorithms were implemented in the open source photogrammetric library and software suite MicMac.

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High frequency variations in Earth rotation

Symposium - International Astronomical Union ◽

10.1017/s0074180900119461 ◽

1988 ◽

Vol 128 ◽

pp. 181-186 ◽

Cited By ~ 1

Author(s):

W. E. Carter ◽

D. S. Robertson ◽

F. W. Fallon

Keyword(s):

Time Series ◽

Earth Orientation ◽

Continuous Coverage ◽

Standard Product ◽

Orientation Time ◽

Monitoring Service ◽

Cross Track ◽

Along Track ◽

Frequency Variations ◽

Nearly Continuous

The combined POLARIS-IRIS Earth orientation time series now span nearly a full cycle of the Chandler-annual beat period, beginning in late 1980. Since April 1985 there is also a nearly continuous coverage of UT1 at daily intervals. We have fit a simple model, consisting of circular 14-month and annual components and a linear drift to the polar motion series, then computed the “along-track” and “cross-track” residuals. Both sets of residuals display structure with amplitudes of tens of milliseconds of arc on time scales of months, but Fourier analysis reveals no significant peaks at shorter periods, including the 40-60 day period found in the UT1 time series.During September, 1986, we introduced a new “quick-look” UT1 time series. The values are typically available within 7 days. The accuracy, which depends strongly on the accuracy of the X and Y pole coordinates used in the computations, ranged from 0.3 to 0.7 milliseconds during the first two weeks, but improved to about 0.1 milliseconds during the latter two weeks of the month. We plan to continue the quick-look UT1 series as a standard product of the IRIS Earth orientation monitoring service.

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Verification of Multimodel Ensemble Forecasts of North Atlantic Tropical Cyclones

Weather and Forecasting ◽

10.1175/waf-d-17-0058.1 ◽

2017 ◽

Vol 32 (6) ◽

pp. 2083-2101 ◽

Cited By ~ 8

Author(s):

Nicholas M. Leonardo ◽

Brian A. Colle

Keyword(s):

North Atlantic ◽

Ensemble Prediction ◽

Laboratory Model ◽

Lead Times ◽

Forecast System ◽

Deterministic Models ◽

Ensemble Forecasts ◽

The Cross ◽

Cross Track ◽

Along Track

Abstract North Atlantic tropical cyclone (TC) forecasts from four ensemble prediction systems (EPSs) are verified using the National Hurricane Center’s (NHC) best tracks for the 2008–15 seasons. The 1–5-day forecasts are evaluated for the 21-member National Centers for Environmental Prediction (NCEP) Global Ensemble Forecast System (GEFS), the 23-member UKMO ensemble (UKMET), and the 51-member European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble, as well as a combination of these ensembles [Multimodel Global (MMG)]. Several deterministic models are also evaluated, such as the Global Forecast System (GFSdet), Hurricane Weather Research and Forecasting Model (HWRF), the deterministic ECMWF model (ECdet), and the Geophysical Fluid Dynamical Laboratory model (GFDL).The ECdet track errors are the smallest on average at all lead times, but are not significantly different from the GEFS and ECMWF ensemble means. All models have a slow bias (90–240 km) in the along-track direction by 120 h, while there is little bias in the cross-track direction. Much of this slow bias is attributed to TCs undergoing extratropical transition (ET). All EPSs are underdispersed in the along-track direction, while the ECMWF is slightly overdispersed in the cross-track direction. The MMG and ECMWF track forecasts have more probabilistic skill than the ECdet and comparable skill to the NHC climatology-based cone forecast. TC intensity errors for the HWRF and GFDL are lower than the coarser models within the first 24 h, but are comparable to the ECdet at longer lead times. The ECMWF and MMG have comparable or better probabilistic intensity forecasts than the ECdet, while the GEFS’s weak bias limits its skill.

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ICESat measurement of Greenland ice sheet surface slope and roughness

Annals of Glaciology ◽

10.3189/172756405781812691 ◽

2005 ◽

Vol 42 ◽

pp. 83-89 ◽

Cited By ~ 33

Author(s):

Donghui Yi ◽

H. Jay Zwally ◽

Xiaoli Sun

Keyword(s):

Three Dimensional ◽

Greenland Ice Sheet ◽

Surface Slope ◽

Radar Altimeter ◽

Digital Elevation ◽

The Cross ◽

Elevation Model ◽

Track Surface ◽

Cross Track ◽

Along Track

AbstractThe Ice, Cloud and land Elevation Satellite (ICESat) in its 8 day repeat orbit mode provided data not only on the along-track surface slope, but also on the cross-track surface slope from adjacent repeat ground tracks. During the first 36 days of operation, four to five such repeat orbits occurred within 1 km in the cross-track direction. This provided an opportunity to use ICESat data to measure surface slope in the cross-track direction at 1 km scale. An algorithm was developed to calculate the cross-track surface slope. Combining the slopes in the cross-track and along-track directions gives a three-dimensional surface slope at 1 km scale. The along-track surface slope and surface roughness at 10km scale are also calculated. A comparison between ICESat surface elevation and a European Remote-sensing Satellite (ERS-1) 5 km digital elevation model shows a difference of 1–2 m in central Greenland where the surface slope is small, and >20m at the edge of Greenland where the surface slope is large. The large elevation difference at the edge is most likely due to the slope-induced error in radar altimeter measurement. Accurate surface slope data from ICESat will help to correct the slope-induced error of radar altimeter missions such as Geosat, ERS-1 and ERS-2.

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Assessment of streamflows in the Hornád river basin and analysis of trends

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/1209/1/012022 ◽

2021 ◽

Vol 1209 (1) ◽

pp. 012022

Author(s):

P Nagy

Keyword(s):

Climate Change ◽

Water Management ◽

Time Series ◽

River Basin ◽

Extreme Rainfall ◽

Dry Season ◽

Trend Test ◽

Surface And Groundwater ◽

Daily Flows

Abstract Climate change is a global phenomenon. The more frequent occurrence of dry periods, which last longer but also extreme rainfall, needs to be reduced for better water management. During the dry season, the quantity and quality of surface and groundwater decreases. Water is important for agriculture, agriculture and ecosystems. This study was focused on the occurrence of trends in daily flows in the Hornád basin at selected hydrological stations for the period 1960-2011. The Mann-Kendall trend test is used to evaluate trends in hydrometeorological time series.

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