The new Horizon2020 “European Gravity Service for Improved Emergency Management” project A new service for gravity field products and to support emergency response to hydrological extreme events

Poster (2014, October 14)

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)

GOCE Precise Science Orbits for the entire mission and their use for Gravity Field Recovery

Scientific Conference (2014, August)

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)

Towards combined global monthly gravity field solutions

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 ▲]

An assessment of degree-2 Stokes coefficients from Earth rotation data

in Geophysical Journal International (2013), 195((1)), 249-259

Variations in the degree-2 Stokes coefficients C20, C21 and S21 can be used to understand long and short-term climate forcing. Here, we derive changes in these coefficients for the period 2003 ... [more ▼]

Variations in the degree-2 Stokes coefficients C20, C21 and S21 can be used to understand long and short-term climate forcing. Here, we derive changes in these coefficients for the period 2003 January–2012 April using Earth rotation data. Earth rotation data contain contributions from motion terms (the effects of winds and currents) and contributions from the effects of mass redistribution. We remove the effects of tides, atmospheric winds and oceanic currents from our data. We compare two different models of atmospheric and oceanic angular momentum for removing the effects of winds and currents: (1) using products from the National Centers for Environmental Prediction and (2) using data from the European Centre for Medium-range Weather Forecasts (ECMWF). We assess the quality of these motion models by comparing the two resulting sets of degree-2 Stokes coefficients to independent degree-2 estimates from satellite laser ranging (SLR), GRACE and a geophysical loading model. We find a good agreement between the coefficients from Earth rotation and the coefficients from other sources. In general, the agreement is better for the coefficients we obtain by removing winds and currents effects using the ECMWF model. In this case, we find higher correlations with the independent models and smaller scatters in differences. This fact holds in particular for C20 and C21, whereas we cannot observe a significant difference for S21. At the annual and semiannual periods, our Earth rotation derived coefficients agree well with the estimates from the other sources, particularly for C21 and S21. The slight discrepancies we obtain for C20 can probably be explained by errors in the atmospheric models and are most likely the result of an over-/underestimation of the annual and semiannual contributions of atmospheric winds to the length-of-day excitation. [less ▲]

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

Scientific Conference (2013, October)

On the capability of non-dedicated GPS-tracked satellite constellations for estimating mass variations: case study SWARM

Scientific Conference (2013, September)