A5026325022- Geophysics and Gravity Measurements
- GNSS positioning and interference
- Oceanographic and Atmospheric Processes
- earthquake and tectonic studies
- Inertial Sensor and Navigation
- Statistical and numerical algorithms
- Time Series Analysis and Forecasting
- Geological and Geophysical Studies Worldwide
- Geomagnetism and Paleomagnetism Studies
- Ionosphere and magnetosphere dynamics
- Climate variability and models
- Advanced Frequency and Time Standards
- Geological and Geophysical Studies
- Archaeological and Historical Studies
- Soil Moisture and Remote Sensing
- Geophysical and Geoelectrical Methods
- Methane Hydrates and Related Phenomena
- Synthetic Aperture Radar (SAR) Applications and Techniques
- Seismic Waves and Analysis
- Geological and Tectonic Studies in Latin America
- Geological Modeling and Analysis
- Spacecraft Design and Technology
- Marine and environmental studies
- Ocean Waves and Remote Sensing
- Target Tracking and Data Fusion in Sensor Networks
University of Beira Interior
2014-2023
Universidade do Porto
2007-2022
University of Lisbon
2015-2020
Centro Interdisciplinar de Investigação Marinha e Ambiental
2011
Japan External Trade Organization
2009
Astronomical Observatory
2005
British Oceanographic Data Centre
2000-2003
Laboratoire des Sciences de l’Information et de la Communication
2001
The accuracy of Global Positioning System (GPS) time series is degraded by the presence offsets. To assess effectiveness methods that detect and remove these offsets, we designed managed Detection Offsets in GPS Experiment. We simulated mimicked realistic data consisting a velocity component, white flicker noises (1/f spectrum noises) composed an additive model. set was made available to analysis community without revealing several groups conducted blind tests with range detection...
It is well known that sea level variations exhibit temporal correlation. This sometimes ignored in the estimation process of rise or taken into account using a first-order autoregressive model. We have verified this stochastic model accurate for yearly tide gauge and reconstruction time-series but it underestimates real rate uncertainty satellite altimetry monthly data by factor 1.3–1.5 even 2. Similar results were found acceleration. An original finding 13–17 per cent data, we random walk...
O1 and M2 observations from well-calibrated spring gravimeters superconducting the Global Geodynamics Project (GGP) are used to test models of Earth's body tide 10 ocean models. It is shown that some give anomalous results in various parts world. For example, Schwiderski model gives discrepancies several areas FES series have problems western Pacific (China, Japan Australia). The majority high-quality tidal gravity measurements Europe close agreement with Dehant, Defraigne Wahr (DDW) elastic...
The coordinate time series determined with the Global Positioning System (GPS) contain annual and semi-annual periods that are routinely modeled by two periodic signals constant amplitude phase-lag. However, phase-lag of seasonal vary slightly over time. Various methods have been proposed to model these variations such as Wavelet Decomposition (WD), writing signal a Chebyshev polynomial is function (CP), Singular Spectrum Analysis (SSA), using Kalman Filter (KF). Using synthetic series, we...
Abstract GPS‐observed vertical ocean tide loading displacements show in Cornwall, southwest England, and Brittany, northwest France, discrepancies of 2–3 mm with predicted values based on the isotropic Preliminary Reference Earth Model for main tidal harmonic M 2 , yet central Europe agreement is better than 0.5 mm. By comparison models validation gauge observations, we demonstrate that uncertainties former are too small to cause this disagreement. Furthermore, find different local crust...
SUMMARY We process continuous GPS data distributed over the Iberian Peninsula, complemented by a few stations in France and North Africa, to constrain displacement field surrounding area. A surface velocity is derived from time-series of daily solutions for each station, whose observations span 3.5 yr or longer. We find that most Iberia forms stable block fixed relative Eurasia which residuals have weighted rms value 0.85 mm yr−1 are all below computed accuracy station. Stations...
By receiving Global Navigation Satellite System (GNSS) signals that are reflected off the sea surface, together with directly received GNSS (using standard geodetic‐type receivers), it is possible to monitor level using regular single difference geodetic processing. We show results from our analysis of three months data GNSS‐based tide gauge at Onsala Space Observatory (OSO) on west coast Sweden. The GNSS‐derived time series local compared independent two stilling well gauges Ringhals and...
Abstract Recent studies have identified climatic drivers of the east‐west see‐saw Pacific Ocean satellite altimetry era sea level trends and a number sea‐level trend acceleration assessments attempt to account for this. We investigate effect climate variability, together with temporally‐correlated noise, on linear error estimates determine new time‐of‐emergence (ToE) across Indian Oceans. Sea‐level often advocate use auto‐regressive (AR) noise models adequately assess formal uncertainties,...
Abstract GPS has been extensively used to estimate tidal ground displacements, but the accuracy of this not systematically verified. Using more than 20 sites distributed across western Europe, we show that postprocessed kinematic precise point positioning with appropriately tuned process noise constraints is capable recovering synthetic displacements inserted into real data, a typical 0.2 mm depending on time series noise. The method does result in erroneous propagation signals from one...
Abstract We integrate Global Positioning System displacements, Gravity Recovery and Climate Experiment gravity data, reservoir water volumes, snowpack to estimate change in subsurface California. find 29% of precipitation infiltrates mountain soil fractured bedrock each autumn winter is lost the spring summer by evapotranspiration lateral flow either within watersheds or into California's Central Valley. The Valley groundwater at 2.2 ± 0.7 km 3 /yr from 2006 2021, with 68% loss occurring...
The noise in position time series of 568 GPS (Global Position System) stations across North America with an observation span ten years has been investigated using solutions from two processing centers, namely, the Pacific Northwest Geodetic Array (PANGA) and New Mexico Tech (NMT). It is well known that frequency domain, exhibits a power-law behavior spectral index around −1. By fitting various models to observations selecting most likely one, we demonstrate some regions flattens zero at long...
Abstract. Anelasticity may decrease the shear modulus of asthenosphere by 8 %–10 % at semidiurnal tidal periods compared with reference 1 s period seismological Earth models. We show that such anelastic effects are likely to be significant for ocean tide loading displacement M2 around East China Sea. By comparison gauge observations, we establish from nine selected models (DTU10, EOT11a, FES2014b, GOT4.10c, HAMTIDE11a, NAO99b, NAO99Jb, OSU12, and TPXO9-Atlas), regional model NAO99Jb is most...
The expected acceleration in sea level rise (SLR) throughout this century poses significant threats to coastal cities and low-lying regions. Since the early 1990s, high-precision multi-mission satellite altimetry (SA) has enabled routine measurement of levels, providing a continuous 30-year record from which mean (global regional) its variability can be computed. latest reprocessed product CMEMS span period 1993 2020, have acquisition accurate data within range 0–20 km. In order fully...
Various methods have been used to model the time-varying curves within global positioning system (GPS) position time series. However, very few consider level of noise a priori before seasonal are estimated. This study is first Wiener filter (WF), already in geodesy denoise gravity records, signals GPS To part signal, first-order autoregressive process employed. The WF then adapted data only those variabilities which significant. Synthetic and real demonstrate that this variation leaves...
We reassess the absolute and relative sea level changes at 38 tide gauge stations in earthquake-affected Western North Pacific for 1993–2015 period, focusing on vertical land motion (VLM) which is crucial narrowing gap between these estimates. In this area, simply discarding all sites, one overestimates average regional rise by more than 0.5 mm/year. Disregarding VLM would lead to misestimating local trends 0.2 7.6 If accounted for, but modeled as linear during entire time span, leads errors...