Quality Evaluation of the Weekly Vertical Loading Effects Induced from Continental Water Storage Models

in Willis, Pascal (Ed.) Proceedings of the 2013 IAG Scientific Assembly, Potsdam, Germany, 1-6 September, 2013 (2015)

To remove continental water storage (CWS) signals from the GPS data, CWS mass models are needed to obtain predicted surface displacements. We compared weekly GPS height time series with five CWS models ... [more ▼]

To remove continental water storage (CWS) signals from the GPS data, CWS mass models are needed to obtain predicted surface displacements. We compared weekly GPS height time series with five CWS models: (1) the monthly and (2) three-hourly Global Land Data Assimilation System (GLDAS); (3) the monthly and (4) one-hourly Modern- Era Retrospective Analysis for Research and Applications (MERRA); (5) the six-hourly National Centers for Environmental Prediction-Department of Energy (NCEP-DOE) global reanalysis products (NCEP-R-2). We find that of the 344 selected global IGS stations, more than 77% of stations have their weighted root mean square (WRMS) reduced in the weekly GPS height by using both the GLDAS and MERRA CWS products to model the surface displacement, and the best improvement concentrate mainly in North America and Eurasia.We find that the one-hourly MERRA-Land dataset is the most appropriate product for modeling weekly vertical surface displacement caused by CWS variations. The threehourly GLDAS data ranks the second, while the GLDAS and MERRA monthly products rank the third. The higher spatial resolution MERRA product improves the performance of the CWS model in reducing the scatter of the GPS height by about 2–6% compared with the GLDAS. Under the same spatial resolution, the higher temporal resolution could also improve the performance by almost the same magnitude. We also confirm that removing the ATML and NTOL effects from the weekly GPS height would remarkably improve the performance of CWS model in correcting the GPS height by at least 10%, especially for coastal and island stations. Since the GLDAS product has a much greater latency than the MERRA product, MERRA would be a better choice to model surface displacements from CWS. Finally, we find that the NCEP-R-2 data is not sufficiently precise to be used for this application. Further work is still required to determine the reason. [less ▲]

A methodology to choose the orbit for a double-pair-scenario future gravity satellite mission: Experiences from the SC4MGV project

Scientific Conference (2014, September 30)

How well can the combination of hlSST and SLR replace GRACE? A discussion from the point of view of applications

Scientific Conference (2014, September 30)

Towards combined global monthly gravity field solutions

Scientific Conference (2014, April)

Pushing the limits of gravity field recovery from high-low satellite-to-satellite tracking –a combination of 10 years of data of the satellite pseudo-constellation CHAMP, GRACE and GOCE

Scientific Conference (2014, April)

On the capability to derive mass estimates from high-low satellite-to-satellite tracking data

Poster (2013, December)

Recently it has been shown that it is possible to derive time-variable gravity signals from high-low satellite-to-satellite tracking (hl-SST) missions (Weigelt et al. 2013, JGR:Solid Earth, doi:10.1002 ... [more ▼]

Recently it has been shown that it is possible to derive time-variable gravity signals from high-low satellite-to-satellite tracking (hl-SST) missions (Weigelt et al. 2013, JGR:Solid Earth, doi:10.1002/jgrb.50283). Based on the GPS information only, we will present results derived from the dedicated gravity field missions CHAMP, GRACE and GOCE which allow us to determine mass estimates for various applications. Hydrologically induced mass changes on land cause the strongest mass variations in the gravity field and can be easily identified in the hl-SST data, especially in areas with strong signals such as the Amazon basin. Ice melt in Greenland can be derived from the data and mass estimates compare well to corresponding GRACE estimates. Also, loading time series based on these gravity field solutions agree well with GPS observations for various stations around the globe. We also discuss the limitations of the data, e.g. in detecting signals related to glacial isostatic adjustment or earthquake-induced gravity field changes. Overall, we will demonstrate that the quality of the GPS data is sufficient nowadays and with a proper processing strategy it is possible to derive reasonable mass estimates. As such, this type of observations may allow to bridge a possible gap between GRACE and its successor GRACE Follow-On scheduled for launch in 2017. [less ▲]

The Decade of the Geopotential - techniques to observe the gravity field from space

Scientific Conference (2013, October)

Towards combined global monthly gravity field solutions

Scientific Conference (2013, October)

Boundary elements for modelling gravitational signals observed by inter-satellite ranging

Poster (2013, September)

Time-variable gravity signal in Greenland revealed by high-low satellite-to-satellite tracking

in Journal of Geophysical Research. Solid Earth (2013), 118

In the event of a termination of the GRACE mission before the launch of GRACE Follow-On (due for launch in 2017) high-low satellite-to-satellite tracking (hl-SST) will be the only dedicated observing ... [more ▼]

In the event of a termination of the GRACE mission before the launch of GRACE Follow-On (due for launch in 2017) high-low satellite-to-satellite tracking (hl-SST) will be the only dedicated observing system with global coverage available to measure the time variable gravity field (TVG) on a monthly or even shorter time scale. Until recently, hl-SST TVG observations were of poor quality and hardly improved the performance of Satellite Laser Ranging observations. To date, they have been of only very limited usefulness to geophysical or environmental investigations. In this paper, we apply a thorough reprocessing strategy and a dedicated Kalman filter to CHAMP data to demonstrate that it is possible to derive the very long wavelength TVG features down to spatial scales of approximately 2000 km at the annual frequency and for multi-year trends. The results are validated against GRACE data and surface height changes from long-term GPS ground stations in Greenland. We find that the quality of the CHAMP solutions is sufficient to derive long-term trends and annual amplitudes of mass change over Greenland. We conclude that hl-SST is a viable source of information for TVG and can serve to some extent to bridge a possible gap between the end-of-life of GRACE and the availability of Grace Follow-On. [less ▲]