Forest height estimation in a tropical forest context from PolInSAR measurements: Illustration from the TropiSAR campaign in French Guyana

The BIOMASS mission was retained in January 2009 as one of the three candidates for the next Earth Explorer Core mission to go to phase A. BIOMASS main objective is to provide information on the carbon sinks and sources in the forests globally, which will be of essential value for climate modelling and policy adaptation, e.g. REDD. Up to now, biomass retrieval algorithms have been developed and validated for the range of biomass up to 300 t/ha. The methods are based on combining SAR intensity and SAR Polarimetric interferometry (PolInSAR) which provide respectively estimates of biomass and canopy height. The remaining questions concern the overall performance of the retrieval algorithms in tropical forests characterized by high biomass density (> 300 t/ha) and complex structure. The TropiSAR experiment in French Guyana was proposed to provide feedbacks on the performances of a P-band SAR to measure biomass and canopy height of a tropical forest with higher biomass density. Characterising tropical forests is essential as it represents a large component of the terrestrial carbon pool and the carbon sources. Specifically, TropiSAR was designed to provide measurements of temporal coherence at P-band over tropical forests for time intervals compatible with space-borne missions (typically 20-30 days), to assess performances of methods transforming P-Band SAR intensity and interferometric measurements into forest biomass and forest height. The SAR system is the ONERA airborne system SETHI that flew in French Guyana in August 2009. This paper presents the first results from this analysis. The temporal coherence at P-band over tropical forests is observed to remain high even after 22 days, a time interval period compatible with typical SAR orbit cycle. The vegetation height map estimated from Polarimetric interferometry is shown to be in good agreement with Lidar measured heights and the in-situ measurements in the study area. The PolInSAR derived height captures the main structural features of the studied forests

Sensitivity of CryoSat-2 Arctic sea-ice freeboard and thickness on radar-waveform interpretation

In the context of quantifying Arctic ice-volume decrease at global scale, the CryoSat-2 satellite was launched in 2010 and is equipped with the Ku band synthetic aperture radar altimeter SIRAL (Synthetic Aperture Interferometric Radar Altimeter), which we use to derive sea-ice freeboard defined as the height of the ice surface above the sea level. Accurate CryoSat-2 range measurements over open water and the ice surface of the order of centimetres are necessary to achieve the required accuracy of the freeboard-to-thickness conversion. Besides uncertainties of the actual sea-surface height and limited knowledge of ice and snow properties, the composition of radar backscatter and therefore the interpretation of radar echoes is crucial. This has consequences in the selection of retracker algorithms which are used to track the main scattering horizon and assign a range estimate to each CryoSat-2 measurement. In this study we apply a retracker algorithm with thresholds of 40, 50 and 80% of the first maximum of radar echo power, spanning the range of values used in the current literature. By using the selected retrackers and additionally results from airborne validation measurements, we evaluate the uncertainties of sea-ice freeboard and higher-level products that arise from the choice of the retracker threshold only, independent of the uncertainties related to snow and ice properties. Our study shows that the choice of retracker thresholds does have a significant impact on magnitudes of estimates of sea-ice freeboard and thickness, but that the spatial distributions of these parameters are less affected. Specifically we find mean radar freeboard values of 0.121 m (0.265 m) for the 40% threshold, 0.086 m (0.203 m) for the 50% threshold and 0.024 m (0.092 m) for the 80% threshold, considering first-year ice (multiyear ice) in March 2013. We show that the main source of freeboard and thickness uncertainty results from the choice of the retracker and the unknown penetration of the radar pulse into the snow layer in conjunction with surface roughness effects. These uncertainties can cause a freeboard bias of roughly 0.06–0.12 m. Furthermore we obtain a significant rise of 0.02–0.15 m of freeboard from March 2013 to November 2013 in the area for multiyear sea ice north of Greenland and Canada. Since this is unlikely, it gives rise to the assumption that applying different retracker thresholds depending on seasonal properties of the snow load is necessary in the future

Emerging RNA-seq applications in food science

Groundbreaking research in food science is shifting from classical methods to novel analytical approaches in which high-throughput techniques have a key role. Among these techniques, RNA-Seq in combination with bioinformatics is applied to investigate topics in food science that were not approachable few years ago. Relevant applications of transcriptomics in modern food science include transcriptome characterization and analysis of gene-expression levels in food crops, foodborne pathogens, and fermenting microorganisms. The aim of the present chapter is to provide an overview of the recent progress in RNA-Seq techniques discussing their advantages and drawbacks. Besides, relevant applications of these technologies will be highlighted in the context of food science to illustrate their impressive potential. Besides, some ideas of the foreseen technological advances and potential applications of these fast-evolving techniques are also provided. © 2014 Elsevier B.V.This work was supported by AGL2011-29857-C03-01 project (Ministerio de Economía y Competitividad, Spain), and CSD2007-00063 FUN-C-FOOD (Programa CONSOLIDER, Ministerio de Educación y Ciencia, Spain). A.V. thanks the Ministerio de Economía y Competitividad for his FPI pre-doctoral fellowship.Peer Reviewe

ESA’s Campaign Activities in Support of Earth Observation Projects: A focus on validation

&amp;lt;p&amp;gt;In the framework of its Earth Observation Programmes the European Space Agency (ESA) carries out ground based and airborne campaigns to support geophysical algorithm developments, calibration/validation activities, simulation of future space-borne earth observation missions, as well as application developments related to remote sensing of the atmosphere, land, oceans, solid earth and cryosphere.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;ESA has conducted over 150 airborne and ground based measurement campaigns in the last 37 years, of which more than 80 were carried out since 2005. During this period a large number of campaigns have supported the validation of ESA&amp;amp;#8217;s satellite missions including for example SMOS and CryoSat. Ongoing activities are focusing on e.g. Sentinel-5Precursor and the preparation of upcoming Earth Explorer missions such as BIOMASS, FLEX, and FORUM. These validation campaigns aim to provide fundamental information about the confidence of data products and their required uncertainties One challenge in this context is a comprehensive understanding and characterization of measurement uncertainty of the validation dataset and the spatial and temporal support or representativity of these.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;span&amp;gt;We will provide an overview of applied strategies to tackle these aspects for existing satellite missions and outline concepts for future missions, and how these integrate into broader earth observation science strategies. In addition, we will highlight recent activities and outline planned activities for the coming years.&amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;</jats:p

P-band SAR study of tropical forest in French Guiana

In August 2009, the TropiSAR campaign was conducted in French Guiana with the ONERA airborne system SETHI in order to support the Phase A of the Earth Explorer candidate mission, BIOMASS. Several SAR data acquisitions at P-band are now available for analysis over tropical forest. This paper presents one of the four acquisition sites, Paracou and two related studies performed over this dataset. The first interrogation focuses on the radiometric stability at P-band of the forest backscatter. This stability is an essential point if the backscatter is expected to be used for forest biomass estimation. Moreover, the compatibility of the current BIOMASS mission design, relying on repeat pass interferometry for forest height retrieval, to tropical forest and the related temporal decorrelation is then explored. (Résumé d'auteur

CryoSat-2 Sea-Ice Freeboard and Thickness

The understanding and predictability of the observed decline of Arctic sea ice depends on the knowledge of its mass balance in a warming environment. While sea ice extent is monitored by passive microwave sensors for decades, only recently its volume is measured by basin-scale sea ice thickness observations of satellite altimetry missions. The current sea ice thickness sensor is SIRAL, a synthetic aperture radar altimeter on-board ESAs CryoSat-2. Altimetry missions measure freeboard, the height of the ice surface above the local water level, which can be converted into sea ice thickness. The conversion is very sensitive to errors in the freeboard retrieval and uncertainties in input parameters for the freeboard-tothickness conversion. Snow on Arctic sea ice plays a crucial role, since its regional variable physical parameters control the penetration of the Ku-Band radar waves and snow depth is required for the sea ice thickness retrieval algorithm, but not measured Arctic-wide. We present Arctic sea ice freeboard and thickness maps from CryoSat-2. The results are compared to available airborne validation datasets, which have been collected in an international validation program (CryoVEx). Sea ice thickness datasets obtained by airborne electromagnetic inductions sounding are available in Arctic spring of 2011 and 2012 and late summer of 2012 to quantify the uncertainties of the CryoSat-2 Arctic sea ice thickness data product of the Alfred Wegener Institute. Compared to the Arctic, only few validation datasets exist for CryoSat-2 sea ice data in the southern Ocean. We present the layout and first results of CryoSat-2 validation campaigns in the Weddell and Bellingshausen Seas between June and October 2013. The complicated snow properties of Antarctic sea ice may increase the uncertainty of CryoSat-2 sea ice thickness data, however sea ice volume estimates in the southern hemisphere are needed as well to understand the contrasting increase of Antarctic sea ice area

TropiSAR, a SAR data acquisition campaign in French Guiana

The TropiSAR campaign has been conducted in August 2009 in French Guiana with the ONERA airborne system SETHI. The main objective of this campaign was to collect data to support the Phase A of the Earth Explorer candidate mission, Biomass. Several specific questions need to be addressed to answer the recommendations of the ESAC group and the data collection strategy has been constructed accordingly. The first part of the paper lists these specific questions. We then describe the selected test sites, followed by a summary on the radar instrument and the radar configuration (geometry and waveform). The data acquisition plan is provided and the first results conclude this paper. (Résumé d'auteur