4 research outputs found
Use of GNSS Tropospheric Products for Climate Monitoring (Working Group 3)
International audienceThere has been growing interest in recent years in the use of homogeneously reprocessed ground-based GNSS, VLBI, and DORIS measurements for climate applications. Existing datasets are reviewed and the sensitivity of tropospheric estimates to the processing details is discussed. The uncertainty in the derived IWV estimates and linear trends is around 1 kg mâ2 RMS and ± 0.3 kg mâ2 per decade, respectively. Standardized methods for ZTD outlier detection and IWV conversion are proposed. The homogeneity of final time series is limited however by changes in the stations equipment and environment. Various homogenization algorithms have been evaluated based on a synthetic benchmark dataset. The uncertainty of trends estimated from the homogenized times series is estimated to ±0.5 kg mâ2 per decade. Reprocessed GNSS IWV data are analysed along with satellites data, reanalyses and global and regional climate model simulations. A selection of global and regional reprocessed GNSS datasets and ERA-interim reanalysis are made available through the GOP-TropDB tropospheric database and online service. A new tropo SINEX format, providing new features and simplifications, was developed and it is going to be adopted by all the IAG services
Improved Constraints on Models of Glacial Isostatic Adjustment: A Review of the Contribution of Ground-based Geodetic Observations
The provision of accurate models of Glacial Isostatic Adjustment (GIA) is
presently a priority need in climate studies, largely due to the potential of the Gravity
Recovery and Climate Experiment (GRACE) data to be used to determine accurate and
continent-wide assessments of ice mass change and hydrology. However, modelled GIA isuncertain due to insufficient constraints on our knowledge of past glacial changes and to
large simplifications in the underlying Earth models. Consequently, we show differences
between models that exceed several mm/year in terms of surface displacement for the two
major ice sheets: Greenland and Antarctica. Geodetic measurements of surface displacement
offer the potential for new constraints to be made on GIA models, especially when
they are used to improve structural features of the Earthâs interior as to allow for a more
realistic reconstruction of the glaciation history. We present the distribution of presently
available campaign and continuous geodetic measurements in Greenland and Antarctica
and summarise surface velocities published to date, showing substantial disagreement
between techniques and GIA models alike. We review the current state-of-the-art in
ground-based geodesy (GPS, VLBI, DORIS, SLR) in determining accurate and precise
surface velocities. In particular, we focus on known areas of need in GPS observation level
models and the terrestrial reference frame in order to advance geodetic observation precision/
accuracy toward 0.1 mm/year and therefore further constrain models of GIA and
subsequent present-day ice mass change estimates