1,013 research outputs found
Generic interferometric synthetic aperture radar atmospheric correction model and its application to co- and post-seismic motions
PhD ThesisThe tremendous development of Interferometric Synthetic Aperture Radar (InSAR) missions in
recent years facilitates the study of smaller amplitude ground deformation over greater spatial
scales using longer time series. However, this poses more challenges for correcting atmospheric
effects due to the spatial-temporal variability of atmospheric delays. Previous attempts have
used observations from Global Positioning System (GPS) and Numerical Weather Models
(NWMs) to separate the atmospheric delays, but they are limited by (i) the availability (and
distribution) of GPS stations; (ii) the time difference between NWM and radar observations;
and (iii) the difficulties in quantifying their performance.
To overcome the abovementioned limitations, we have developed the Iterative Tropospheric
Decomposition (ITD) model to reduce the coupling effects of the troposphere turbulence and
stratification and hence achieve similar performances over flat and mountainous terrains. Highresolution European Centre for Medium-Range Weather Forecasts (ECMWF) and GPS-derived
tropospheric delays were properly integrated by investigating the GPS network geometry and
topography variations. These led to a generic atmospheric correction model with a range of
notable features: (i) global coverage, (ii) all-weather, all-time usability, (iii) available with a
maximum of two-day latency, and (iv) indicators available to assess the model’s performance
and feasibility.
The generic atmospheric correction model enables the investigation of the small magnitude coseismic deformation of the 2017 Mw-6.4 Nyingchi earthquake from InSAR observations in
spite of substantial atmospheric contamination. It can also minimize the temporal correlations
of InSAR atmospheric delays so that reliable velocity maps over large spatial extents can be
achieved. Its application to the post-seismic motion following the 2016 Kaikoura earthquake
shows a success to recover the time-dependent afterslip distribution, which in turn evidences
the deep inactive subduction slip mechanism. This procedure can be used to map surface
deformation in other scenarios including volcanic eruptions, tectonic rifting, cracking, and city
subsidence.This work was supported by a Chinese Scholarship Council studentship. Part of this work was
also supported by the UK NERC through the Centre for the Observation and Modelling of
Earthquakes, Volcanoes and Tectonics (COMET)
MODIS: Moderate-resolution imaging spectrometer. Earth observing system, volume 2B
The Moderate-Resolution Imaging Spectrometer (MODIS), as presently conceived, is a system of two imaging spectroradiometer components designed for the widest possible applicability to research tasks that require long-term (5 to 10 years), low-resolution (52 channels between 0.4 and 12.0 micrometers) data sets. The system described is preliminary and subject to scientific and technological review and modification, and it is anticipated that both will occur prior to selection of a final system configuration; however, the basic concept outlined is likely to remain unchanged
Verification and Validation of NASA-Supported Enhancements to the Near Real Time Harmful Algal Blooms Observing System (HABSOS)
This report discusses verification and validation (V&V) assessment of Moderate Resolution Imaging Spectroradiometer (MODIS) ocean data products contributed by the Naval Research Laboratory (NRL) and Applied Coherent Technologies (ACT) Corporation to National Oceanic Atmospheric Administration s (NOAA) Near Real Time (NRT) Harmful Algal Blooms Observing System (HABSOS). HABSOS is a maturing decision support tool (DST) used by NOAA and its partners involved with coastal and public health management
Community Review of Southern Ocean Satellite Data Needs
This review represents the Southern Ocean community’s satellite data needs for the coming decade. Developed through widespread engagement, and incorporating perspectives from a range of stakeholders (both research and operational), it is designed as an important community-driven strategy paper that provides the rationale and information required for future planning and investment. The Southern Ocean is vast but globally connected, and the communities that require satellite-derived data in the region are diverse. This review includes many observable variables, including sea-ice properties, sea-surface temperature, sea-surface height, atmospheric parameters, marine biology (both micro and
macro) and related activities, terrestrial cryospheric connections, sea-surface salinity, and a discussion of coincident and in situ data collection. Recommendations include commitment to data continuity, increase in particular capabilities (sensor types, spatial, temporal), improvements in dissemination of data/products/uncertainties, and innovation in calibration/validation capabilities. Full recommendations are detailed by variable as well as summarized. This review provides a starting point for scientists to understand more about Southern Ocean processes and their global roles, for funders to understand the desires of the community, for commercial operators to safely conduct their activities in the Southern Ocean, and for space agencies to gain greater impact from Southern Ocean-related acquisitions and missions.The authors acknowledge the Climate at the Cryosphere program and the Southern Ocean
Observing System for initiating this community effort, WCRP, SCAR, and SCOR for endorsing the effort, and CliC, SOOS, and SCAR for supporting authors’ travel for collaboration on the review. Jamie Shutler’s time on this review was funded by the European Space Agency project OceanFlux Greenhouse Gases Evolution (Contract number 4000112091/14/I-LG)
Detecting trend and seasonal changes in bathymetry derived from HICO imagery: A case study of Shark Bay, Western Australia
The Hyperspectral Imager for the Coastal Ocean (HICO) aboard the International Space Station has offered for the first time a dedicated space-borne hyperspectral sensor specifically designed for remote sensing of the coastal environment. However, several processing steps are required to convert calibrated top-of-atmosphere radiances to the desired geophysical parameter(s). These steps add various amounts of uncertainty that can cumulatively render the geophysical parameter imprecise and potentially unusable if the objective is to analyze trends and/or seasonal variability. This research presented here has focused on: (1) atmospheric correction of HICO imagery; (2) retrieval of bathymetry using an improved implementation of a shallow water inversion algorithm; (3) propagation of uncertainty due to environmental noise through the bathymetry retrieval process; (4) issues relating to consistent geo-location of HICO imagery necessary for time series analysis, and; (5) tide height corrections of the retrieved bathymetric dataset. The underlying question of whether a temporal change in depth is detectable above uncertainty is also addressed. To this end, nine HICO images spanning November 2011 to August 2012, over the Shark Bay World Heritage Area, Western Australia, were examined. The results presented indicate that precision of the bathymetric retrievals is dependent on the shallow water inversion algorithm used. Within this study, an average of 70% of pixels for the entire HICO-derived bathymetry dataset achieved a relative uncertainty of less than ± 20%. A per-pixel t-test analysis between derived bathymetry images at successive timestamps revealed observable changes in depth to as low as 0.4 m. However, the present geolocation accuracy of HICO is relatively poor and needs further improvements before extensive time series analysis can be performed
Directory of Atmospheric, Hydrographic and Biological datasets for the Canary Current Large Marine Ecosystem
Environmental and biological data-sets were recovered from oceanographic surveys and other
observation sources (e.g. tide gauges) since the 40s. This rescue and mining exercise was
carried out in cooperation with the countries bordering the CCLME and other nations
undertaking research in the region (i.e. Morocco, Mauritania, Senegal, Gambia, Guinea, Guinea
Bissau, Cape Verde, Spain, Norway, Germany and France). A total of 425 data-sets, 27 databases
and 21 time-series sites have been identified in the area. A substantial part of them were
rescued from archives supported in paper copy. Finally, a directory of meta-data referring 99
data-sets and data-bases has been published. This catalogue and the recovered data offer an
exceptional opportunity for the researchers in the CCLME to study the dynamics and trends of a
multiplicity of variables, and will enable them to create their own time-series, baselines and
climatologies under a spatial and temporal perspective. It will produce new and valuable
information on changes produced during the last 35 years in this region, going from climatic
changes to shifts in species diversity and populations due to natural and human induced
factors. This directory is the first result of the project “Enhancing oceanography capacities on
Western Africa Countries” funded by the Spanish Agency for International Development
Cooperation (AECID) and coordinated by the IOC-UNESCO and the IEO. The project aims to
reinforce transboundary cooperation in the CCLME and to facilitate access and data flow to
existing scientific information and its utilization by the scientists, politicians, industry and civil
society.http://unesdoc.unesco.org/images/0023/002314/231430E.pd
- …