Showing papers by "Helmut Rott published in 2010"

Cold Regions Hydrology High-Resolution Observatory for Snow and Cold Land Processes

Abstract: Snow is a critical component of the global water cycle and climate system, and a major source of water supply in many parts of the world. There is a lack of spatially distributed information on the accumulation of snow on land surfaces, glaciers, lake ice, and sea ice. Satellite missions for systematic and global snow observations will be essential to improve the representation of the cryosphere in climate models and to advance the knowledge and prediction of the water cycle variability and changes that depend on snow and ice resources. This paper describes the scientific drivers and technical approach of the proposed Cold Regions Hydrology High-Resolution Observatory (CoReH2O) satellite mission for snow and cold land processes. The sensor is a synthetic aperture radar operating at 17.2 and 9.6 GHz, VV and VH polarizations. The dual-frequency and dual-polarization design enables the decomposition of the scattering signal for retrieving snow mass and other physical properties of snow and ice.

Investigating the feasibility of the globsnow snow water equivalent data for climate research purposes

Abstract: This paper presents the efforts for creating two global scale snow dataset covering 15 and 30 years of satellite-based observations, one describing the extent of snow cover (SE) the other describing the snow water equivalent (SWE) characteristics. The main emphasis of the paper is describing the validation work carried out for the SWE product that will cover the non-mountainous regions of Northern Hemisphere on a daily basis starting from 1979. The work has been carried out within the ESA Globsnow project.

Reduced glacier sliding caused by persistent drainage from a subglacial lake

Abstract: . We present velocity observations of a glacier outlet in Vatnajokull, Iceland, deduced from interferometric SAR (InSAR) data obtained during the ERS1/2 tandem mission in 1995–2000. More than a 50% decrease in glacier velocity was observed subsequent to a large jokulhlaup from the subglacial lake Grimsvotn in 1996. The glacier had not reached its former flow rate in 2000. The jokulhlaup damaged the lake's ice-dam causing persistent drainage from the lake. InSAR based studies of water accumulation within Grimsvotn suggest that a leakage of >3 m3 s−1 prevailed throughout our study period. We suggest that the lake leakage kept open a tunnel at low water pressure underneath the whole length of the glacier. The tunnel flow drained water from its surroundings, hence lowering the water pressure of a distributed drainage system, underneath the upper and centre parts of the glacier, which prior to the jokulhlaup sustained significant basal sliding. This is in accordance with theoretical prediction that tunnel flow in a steady state may cause slow-down in glacier velocity by reducing the subglacial water pressure. The width of the affected areas was ~5 km on the upper part of the glacier and ~8 km on the centre part of the glacier. This indicates that the water pressure reduction propagates laterally from the tunnel over a distance of a few km.

Signal: SAR for ice, glacier and global dynamics

Abstract: SIGNAL is an innovative earth exploration mission proposal with the main objective to estimate accurately and repeatedly topography and topographic changes associated with mass change or other dynamic effects on glaciers, ice caps and polar ice sheets. Elevation measurements are complemented with glacier velocity measurements, providing valuable additional information for a better understanding of the hydrology of glacierized basins and of the Arctic and Antarctic water cycle. SIGNAL is capable of monitoring all critical regions with a high spatial resolution and an adequate revisit time. This paper gives an overview about the actual mission design status and provides a brief description of the topography (DEM - digital elevation map) self-calibration strategy and the estimated global interferometric performance.

SIGNAL: Mission Concept and Performance Assessment

Abstract: SIGNAL (SAR for Ice, Glacier and oceaN globAL dynamics) is a proposal for an innovative Earth observation mission, under study at German Space Agency. The mission objectives include the determination of ice topography and its temporal changes, the monitoring of fast-flowing glaciers, and the characterisation of ocean currents, by using Ka-band synthetic aperture radar (SAR). Two approaches to the mission, including a single satellite with multiple antennas and two free flyers, are presented and critically discussed. A preliminary performance analysis for the key mission measurements has been performed and will be presented.

Observing seasonal snow changes in the boreal forest area using active and passive microwave measurements

Abstract: We present initial results from an experimental campaign aiming to acquire a comprehensive, full-snow season dataset of simultaneous backscatter and brightness temperature measurements of snow covered ground. The campaign is a part of Phase A activities in support of the proposed CoReH2O mission, aiming both to contribute to investigations on interpreting snow properties from active microwave observations, and to explore the possibilities for synergistic use of active measurements with existing passive microwave instruments. The campaign period covers the winter season of 2009-2010. Microwave observations are complemented by detailed in situ data of snow cover properties.

Evaluation of vegetation effect on the retrieval of snow parameters from backscattering measurements: A contribution to CoReH2O mission

Abstract: In preparation of the satellite mission CoReH2O, one of the three missions selected for scientific and technical feasibility studies within the Earth Explorer Programme of the European Space Agency, experimental and theoretical studies started in order to investigate backscatter properties of snow covered terrain and improve the methods for retrieval of snow physical properties from SAR data. The aim of this paper is to investigate the impact of vegetation in the retrieval of snow parameters from backscattering measurements. First a radiative transfer model, able to simulating scattering from a vegetated snow-covered terrain was developed and implemented. Lastly, a sensitivity analysis on snow and vegetation parameters was conducted for coniferous forest. Results confirm that with increasing biomass the sensitivity to SWE strongly decreases. Moreover when biomass is in the 0–150 m3/ha range a procedure to correct the vegetation effect in the SWE retrieval algorithm is suggested

Tandem-L: A Satellite Mission for Monitoring Dynamic Processes on the Earth’s Surface

Abstract: Tandem-L is a proposal for a highly innovative satellite mission for the global observation of dynamic processes on the earth’s surface with hitherto unknown quality and resolution. Thanks to the novel imaging techniques and the vast recording capacity, Tandem-L will provide urgently needed information for solving pressing scientific questions in the areas of the biosphere, geosphere, cryosphere, and hydrosphere. Tandem-L will make a vital contribution towards a better understanding of the earth system and its dynamics. Important mission goals are the global measurement of forest biomass for a better understanding of the carbon cycle, the systematic recording of deformations of the earth’s surface with millimetre accuracy for earthquake research and risk analysis, the quantification of glacier movements and melting processes in the polar regions, the large scale observation of ocean currents and the high resolution measurement of variations in soil moisture close to the surface. Hence, in a time of intense scientific discussion about the extent and effects of climate change, Tandem-L can provide important, currently missing information for improved scientific forecasting and related socio-political recommendations. The Tandem-L mission concept is based on the use of two radar satellites operating in L-band (23.6 cm wavelength). The utilisation of the special synthetic aperture radar technique (SAR) enables high resolution imaging of the earth’s surface independent of weather and time of day; it therefore offers the ideal basis for the continuous observation of dynamic processes on the earth’s surface. Moreover, the long wavelength compared to X-band (3.1 cm) fulfils the requirements for a tomographic measurement of the three-dimensional structure of vegetation and ice regions, as well as for large scale surveying of deformations with millimetre accuracy. The goal of Tandem-L is to image the land mass interferometrically once a week. Above and beyond the primary mission goals, the data set generated by Tandem-L has immense potential for developing new scientific and commercial applications. Beside the scientific component, Tandem-L is distinguished by the high degree of innovation with respect to the methodology and technology. Examples are the polarimetric SAR interferometry for measuring forest height, multi-pass coherence tomography for determining the vertical structure of vegetation and ice, the utilisation of the latest digital beam forming techniques for increasing the swath width and imaging resolution, as well as the close formation flying of two cooperative radar satellites with variable adjustable spacing. Tandem-L will firmly cement Germany’s international leadership in the area of space-borne radar and even extend it. Thanks to the unique data products, the mission will be a milestone in remote sensing, and the revolutionary techniques and technologies used on Tandem-L will form the basis for future generations of satellite SAR systems. The Tandem-L mission will unlock the door to a future global remote sensing system for the continuous observation of the earth’s surface, as currently exists for weather prediction where a network of geostationary satellites is used. It is planned to realise the Tandem-L mission together with NASA/JPL. This allows a cost effective implementation, whereby each partner contributes its predevelopments and experience. The cooperation with the USA means a unique remote sensing system will be created, exceeding the performance of existing systems by at least an order of magnitude. The mission concept was developed in detail in a two-year pre-phase A study together with NASA/JPL. According to current planning, the Tandem-L satellites could be launched in 2017. Tandem-L offers a unique opportunity to closely mesh the multifarious activities of the Helmholtz Association (HGF), spanning the different research areas, in a joint interdisciplinary project. The expertise of the relevant HGF research centres with their specific modelling techniques is imperative for producing highly aggregated information products. Moreover, the complementary expertise of the HGF research centres and the American scientific team in data utilisation and modelling means that a fruitful cooperation with a large synergistic effect can be expected. Tandem-L is therefore predestined to set a historic milestone in earth system research and make an important contribution to a better understanding and better preservation of the earth and its environment.

The evolution in the glacier mass balance of Hofsjökull ice cap, central Iceland, in 1986-2008, revealed by multi-source remote sensing data

Abstract: (1) The Nordic Volcanological center, Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland (eyjolfm@raunvis.hi.is), (2) Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland (hb@raunvis.hi.is), (3) Institute of Meteorology and Geophysics, University of Innsbruck, Innsbruck, Austria (Helmut.Rott@uibk.ac.at), (4) Universite de Toulouse, CNRS, LEGOS, Toulouse, France (etienne.berthier@legos.obs-mip.fr), (5) Icelandic Meteorological Office, Reykjavik, Iceland (tj@vedur.is)

EO Small Satellite Missions and Formation Flying

Abstract: The aim of the ESA study on concepts for demonstration of advanced techniques and technologies on an EO small mission is to assess ideas for EO missions compatible with implementation on a small satellite such as PROBA, and which may benefit from Formation Flying. “Small Mission” here implies small satellite platforms in the 150–200 kg spacecraft mass range. The output of the study is a definition of various small satellite missions and their required developments, including costs. The study has been led by Astrium Ltd, with support from Astrium SAS, Astrium GmbH, ENVEO, GMV and Verhaert Space. Following initial selection in the first part of the study, 3 candidates have been analysed in more detail as discussed below.

Cold Regions Hydrology High-ResolutionObservatoryfor SnowandColdLandProcesses Moreaccuratemeasurementsofsnowandicecoverageonlandandseaareexpectedto provide better information for predicting the Earth's future climate changes.

Abstract: Snow is a critical component of the global water cycle and climate system, and am ajor source of water supply in many parts of the world. There is a lack of spatially distributed information on the accumulation of snow on land surfaces, glaciers, lake ice, and sea ice. Satellite missions for systematic and global snow observations will be essential to improve the representation of the cryosphere in climate models and to advance the knowledge and prediction of the water cycle variability and changes that depend on snow and ice resources. This paper describes the scientific drivers and technical approach of the proposed Cold Regions Hydrology High- Resolution Observatory (CoReH2O) satellite mission for snow and cold land processes. The sensor is a synthetic aperture radar operating at 17.2 and 9.6 GHz, VV and VH polarizations. The dual-frequency and dual-polarization design enables the decomposition of the scattering signal for retrieving snow mass and other physical properties of snow and ice.