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We studied a newly identified, multiple-kilometer-long rock slope failure in the Aiguilles Rouges massif (Chamonix valley, France). Owing to a high-resolution light detection and ranging (LiDAR) digital elevation model (DEM) and field work, we mapped morphostructures, including scarps, open fractures, and counterscarps. In some places, vertical offsets can reach tens of meters and crevasses can be meters wide. The evidence of gravitational activity (boulder displacements from analyses of archival satellite images) and the sharpness of the scarp outcrops together suggest very recent movements. These observations agree with ground displacement rates of a few millimeters per year estimated by interferometric synthetic aperture radar (InSAR) time series between 2014 and 2018. We sampled two vertical profiles along the top scarps to define the chronology of the slope failure using beryllium-10 (10Be) surface exposure dating. Glacially polished surfaces cut by these gravitational scarps were also sampled to determine glacial retreat timing as well as to constrain the pre-exposure 10Be inheritance. In total, 11 samples were studied. Our results highlight a significant time lag (approximately 15 ka) between the first evidence of nonglacial activity and the initiation of the slope failure that happened 1.3–2.5 ka ago, depending on the inheritance schemes. This suggests that the delayed opening of the crevasse is only one stage of a process that began when the valley was deepened and the glacial debuttressing is not the unique driving factor. This process of progressive failure of an excessively steep slope may continue, and the evolution of this slope failure may constitute a hazard for the upper part of the Chamonix valley. [ABSTRACT FROM AUTHOR]

Intertidal meanders developed on salt marshes are known to expand and produce inclined heterolithic stratification rich in fine‐grained sediments and to bear evidence for rhythmic deposition in the upper part of the inner meander bend (i.e. the upper part of the point bar). This occurs because the lower point‐bar deposits are washed by strong currents, which remove mud drapes and develop discontinuous record of tidal cycles. Although these criteria are widely accepted, facies models for tidal point bars still lack a three‐dimensional perspective and overlook the along‐bend variability of sediment distribution. The present study focuses on a hypertidal point bar belonging to the upper‐intertidal domain of the Mont‐Saint‐Michel Bay (France), and it analyses the sedimentology of a 3D time‐framed accretionary package formed between 28 March 2012 and 29 November 2012 by means of lidar topographic data, geomorphological field surveys and sedimentological core data. To define the 3D time‐framed accretionary package, data from thirteen lidar (light detection and ranging) topographic surveys were used to create the point‐bar synthetic stratigraphy. Data show that over the study period the point bar expanded alternating deposition along its seaward and landward sides, pointing out the occurrence of depositional patterns more complex than a simple progressive expansion of the bend. The thickest deposits were accumulated in the point‐bar‐apex zone, where the largest amount of mud was also stored. High sediment accretion in the bend‐apex zone is ascribed to the development of low‐energy conditions due to flow and bed configuration. High accretion rate of the point‐bar‐apex zone promoted also a better preservation of rhythmites, which are almost missing from deposits accumulated along the point‐bar sides. This study remarks that preservation of mud and tidal rhythmites within intertidal‐point‐bar deposits is controlled, not only by their elevation with respect to the tidal range, but also by their location along the point bar. [ABSTRACT FROM AUTHOR]

In this paper, we propose an operational solution for the yearly classification of crop parcels at national scale (namely France) for Land Parcel Identification System updating, under the Common Agricultural Policy (CAP) umbrella. Our pipeline is based on the ι 2 open-source framework and fed with both time series of Sentinel-1 radar and Sentinel-2 optical images, with complementary contributions. Three conceivable scenarios are investigated with two sets of nomenclatures (17 and 43 classes): early, on-line, and late classifications. Experiments performed on 2017 show very satisfactory results (82–97%), locally almost on-par with state-of-the-art deep-based methods. We can conclude our framework offers a strong basis for country-scale operational deployment for 2020+ CAP. [ABSTRACT FROM AUTHOR]

An Ultra-Violet Rayleigh-Mie lidar has been integrated aboard the French research aircraft Falcon20 in order to monitor the ash plume emitted by the Eyjafjallaj ökul volcano in April-May 2010. Three operational flights were carried out on 21 April, 12 and 16 May 2010 inside French, Spanish and British air spaces, respectively. The original purpose of the flights was to provide the French civil aviation authorities with objective information on the presence and location of the ash plume. The present paper presents the results of detailed analyses elaborated after the volcano crisis. They bear on the structure of the ash clouds and their optical properties such as the extinction coefficient and the lidar ratio. Lidar ratios were measured in the range of 43 to 50 sr, in good agreement with the ratios derived from ground- based lidar near Paris (France) in April 2010 (∼48 sr). The ash signature in terms of particulate depolarization was consistent during all flights (between 34±3% and 38±3%). Such a value seems to be a good identification parameter for volcanic ash. Using specific cross-sections between 0.19 and 1.1m² g-1, the minimum (maximal) mass concentrations in the ash plumes derived for the flights on 12 and 16 May were 140 (2300) and 250 (1500) µgm-3, respectively. It may be rather less than, or of the order of the critical level of damage (2mgm-3) for the aircraft engines, but well above the 200 µgm-3 warning level. [ABSTRACT FROM AUTHOR]

Abstract: Coastal dune management presents a unique problem to coastal scientists, not only because of the dynamic and complex nature of coastal dune systems but also because of the protection service against many coastal hazards such as storm surges in low and flat coastal countries, shoreline retreat, and aeolian erosion. In order to evaluate such a service, a new GIS modelling of a coastal dune protection service has been carried out on Noirmoutier Island. It is based upon geoinformation coming from LIDAR, Spot satellite and aerial photography data processing. This paper discusses the Geographic Information System (GIS) methodology used for data acquisition and analysis and presents a methodology developed (i) to characterise and map dune shapes using geoindicators in order to highlight aeolian deflation, marine coastal erosion and marine submersion over the long-term and (ii) to set up a transferable and synthetic methodology. This methodology is based upon spatial syntheses computed in regular 50 m*400 m boxes built up landward from the shoreline. Each variable is integrated within each box. This allows to quantify (i) spatial occurrence of each variable and (ii) spatial coincidence of many variables within each box. Each protection service is underlying by a set of variables. The state of the protection service is then discussed and quantified and can be used by stakeholders to manage dunes in a safe way for society stakes. [Copyright &y& Elsevier]

During the Eyjafjallajökull eruption (14 April to 24 May 2010), the volcanic aerosol cloud was observed across Europe by several airborne in situ and ground-based remote-sensing instruments. On 18 and 19 May, layers of depolarizing particles (i.e. non-spherical particles) were detected in the free troposphere above the Puy de Dôme station, (PdD, France) with a Rayleigh-Mie LIDAR emitting at a wavelength of 355 nm, with parallel and crossed polarization channels. These layers in the free troposphere (FT) were also well captured by simulations with the Lagrangian particle dispersion model FLEXPART, which furthermore showed that the ash was eventually entrained into the planetary boundary layer (PBL). Indeed, the ash cloud was then detected and characterized with a comprehensive set of in situ instruments at the Puy de Dôme station (PdD). In agreement with the FLEXPART simulation, up to 65 µgm-3 of particle mass and 2.2 ppb of SO2 were measured at PdD, corresponding to concentrations higher than the 95 percentile of 2 yr of measurements at PdD. Moreover, the number concentration of particles increased to 24 000 cm-3, mainly in the submicronic mode, but a supermicronic mode was also detected with a modal diameter of 2 µm. The resulting optical properties of the ash aerosol were characterized by a low scattering ° Angstr¨om exponent (0.98), showing the presence of supermicronic particles. For the first time to our knowledge, the combination of in situ optical and physical characterization of the volcanic ash allowed the calculation of the mass-to-extinction ratio (η) with no assumptions on the aerosol density. The mass-to-extinction ratio was found to be significantly different from the background boundary layer aerosol (max: 1.57 gm-2 as opposed to 0.33±0.03 gm-2). Using this ratio, ash mass concentration in the volcanic plume derived from LIDAR measurements was found to be 655±23 µgm-3 when the plume was located in the FT (3000m above the sea level -- a.s.l.). This ratio could also be used to retrieve an aerosol mass concentration of 579±60 µgm-3 on 19 April, when LIDAR observations detected the ash cloud at 3000ma.s.l. in correspondence with model simulations (FLEXPART). On 22 April, another ash plume entered the BL, and although it was more diluted than during the May episode, the French research aircraft ATR42 that passed over Clermont-Ferrand in the PBL confirmed the presence of particles with a supermicronic mode, again with a modal diameter at 2 µm. This data set combining airborne, ground-based and remote sensing observations with dispersion model simulations shows an overall very good coherence during the volcanic eruption period, which allows a good confidence in the characteristics of the ash particles that can be derived from this unique data set. [ABSTRACT FROM AUTHOR]

There are several approaches which can be adopted to present close-range photogrammetry in France: historical, economic, technical, or by field of application. The paper starts with a short account of the history of close-range photogrammetry. It then presents notable technical progress and its impact on users (the digital era, the laser scanners, and recently the fully automatic tools), and it finally shows the democratization of photogrammetry. The whole paper is mainly focused on cultural heritage applications. [ABSTRACT FROM AUTHOR]

This paper is a review of various research works in France on airborne LiDAR applied to the monitoring of natural environment. Firstly, it presents applications based on the use of very high-resolution digital surface models derived from LiDAR data. The use of such models is quickly expanding on all the fields related to the environment. This article also discusses more specific research on signal processing and accuracy. Part of this work summarizes papers that were published in the "Revue Française de Photogrammétrie et de Télédétection (RFPT)", the French Journal of Photogrammetry and Remote Sensing, following two national conferences organized in Montpellier (2006) and Le Mans (2009) in order to invite researchers using LiDAR in several fields of application to initiate technical and scientific exchanges. We also provide an update on ongoing research and instrument developments in France. [ABSTRACT FROM AUTHOR]

ABSTRACT Black marls form very extensive outcrops in the Alps and constitute some of the most eroded terrains, thus causing major problems of sedimentation in artificial storage systems (e.g. reservoirs) and river systems. In the experimental catchments near Draix (France), soil erosion rates have been measured in the past at the plot scale through a detailed monitoring of surface elevation changes and at the catchment scale through continuous monitoring of sediment yield in traps at basin outlets. More recently, erosion rates have been determined by means of dendrogeomorphic techniques in three monitored catchments of the Draix basin. A total of 48 exposed roots of Scots pine have been sampled and anatomical variations in annual growth rings resulting from denudation analysed. At the plot scale, average medium-term soil erosion rates derived from exposed roots vary between 1·8 and 13·8 mm yr−1 (average: 5·9 mm yr−1) and values are significantly correlated with slope angle. The dendrogeomorphic record of point-scale soil erosion rates matches very well with soil erosion rates measured in the Draix basins. Based on the point-scale measurements and dendrogeomorphic results obtained at the point scale, a linear regression model involving slope angle was derived and coupled to high-resolution slope maps obtained from a LiDAR-generated digital elevation model so as to generate high-resolution soil erosion maps. The resulting regression model is statistically significant and average soil erosion rates obtained from the areal erosion map (5·8, 5·2 and 6·2 mm yr−1 for the Roubine, Moulin and Laval catchments, respectively) prove to be well in concert with average annual erosion rates measured in traps at the outlet of these catchments since 1985 (6·3, 4·1 and 6·4 mm yr−1). This contribution demonstrates that dendrogeomorphic analyses of roots clearly have significant potential and that they are a powerful tool for the quantification and mapping of soil erosion rates in areas where measurements of past erosion is lacking. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The article discusses the German-French climate monitoring initiative of the German Aerospace Center (DLR) and Centre National d'Etudes Spatiales (CNES) which proposes a space-based methane remote lidar mission (MERLIN) to measure methane emissions. It also states that the development of the instrument intends to enhance the distinction between anthropogenic and natural methane sources. It further analyzes the performance of MERLIN based on the lidar system simulations.

Abstract: Over 10,000 closed depressions (CDs) are found in the silty plains of Northeastern France. These small wetlands support the growth of rare plant species. Although their origins, which could be anthropogenic or geologic due to salt/gypsum lens dissolution, have been debated for 150years, they have not yet been the focus of an integrated study. In 39 geological borings along a 15-km² strip, no salt/gypsum lenses and more than 260 CDs were recorded using LiDAR. All of the investigated CDs have a bathtub form with a flat bottom. Complete excavations clearly showed a cut contact between the sediment and the horizontal marl substratum at the bottom, and a cut at the edges of the upper marl layers. Radiocarbon dating of sediment bottoms showed that sedimentation began between the second Iron Age and the Roman period. The frequencies of pollen and Sporormiella-type depict an open landscape with grassland, pasture and cropland. These convergent findings challenge the hypothesis that CDs formed naturally and suggest that they area instead anthropogenic. Because no soil deposits were found around the CDs, digging may have been intended to marl the surrounding acidic silty soils. The high density and small size of CDs will allow the detailed reconstruction of landscape and biodiversity modifications in the region for the two last millennia. [ABSTRACT FROM AUTHOR]

Starting in 2005, the French Naval Hydrographic and Oceanographic Office (Service Hydrographique et Océanographique de la Marine [SHOM]) and the French National Geographic Institute (Institut Géographique National [IGN]) began conducting a series of coastal surveys using airborne light detection and ranging (LIDAR) bathymetry (ALB) and topographic LIDAR technologies. This paper describes SHOM's experience using ALB in very shallow coastal waters and under challenging hydrographic survey conditions. The performance of ALB in comparison to multibeam echosounder (MBES) and topographic LIDAR surveys is discussed. Further, a procedure is described for integrating ALB data sets from SHOM with topographic data sets from IGN. Recommendations on conducting future survey operations are provided in this paper based on the experience gained and lessons learned. Based on these experiences, SHOM and IGN have begun a national survey project on mapping the coastal areas (sea and land) of France. [ABSTRACT FROM AUTHOR]

Abstract: This study has exploited aerial photographs and LiDAR digital elevation model to quantify intertidal complex landforms volume. A first volume estimation of the main sabellariid polychaete reef complex of the Bay of Mont-Saint-Michel – France is presented. The Sabellaria alveolata is an engineering species that heavily modifies its environment. This gregarious tube-building annelid forms dense and solid reefs of bioclastic coarse sand which can reach several km2. Since 1970 a very strong decline of reefs has been observed. The authorities have curbed fishing activities without any noticeable changes in reef health status. The S. alveolata reef volume is estimated to be 132 048 m3 (96 301 m3 for Sainte-Anne reef and 35 747 m3 for Champeaux reef). Further LiDAR data surveys will be needed to be able to understand and quantify the accretion/erosion processes in play in the reef dynamic. Because of the internal variability of topographic complexity of the reef, characterized by crevices, cracks, and holes rather than whole blocks, further studies are needed to calculate more accurately the volume of the reef. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the data quality of elevation and accuracy of bathymetric LiDAR topographical data on the Gardon gravel bed river in France. It mentions the utilization of a specific geostatistical method that carries out upscaling and interpolation of reference data to examine the possible consequences and uncertainties. Results show a high depth bias with a 0-32 meter standard deviation random error, however, LiDar gives an accurate intepretation of riverbed form.

Abstract: This contribution integrates and analyzes data from high-resolution multibeam, seismic profiles, bathymetric LiDAR, and surficial sediment data for the geomorphological seascapes characterisation and process-description of the Basque inner and middle continental shelf (northern Spain). From the data obtained, the Basque shelf is characterised by a heterogeneous seafloor where, on a small spatial scale, different morphologies and sedimentary processes can be observed. Tectonic activity and sea-level changes, together with present processes of sediment supply and climatic conditions, have a critical influence on the present configuration of the continental shelf and the distribution of seafloor types. On the basis of all of the datasets, seafloor classification, bedform analysis, long-term sea-level change-induced seafloor features and anthropogenic features over the seafloor, are described. As a result, three distinct zones have been identified for the Basque shelf, related to the main geomorphological features and seascapes, as summarised below. (i) A western part, with a northwestern orientation, which coincides with the prevailing wave direction. This zone is characterised by a predominantly rocky substrate, except within the mouth of the Nervión estuary, where sandy sediments appear to infill a paleo-channel. (ii) A central part, which is oriented towards the northeast and receives less wave energy. Within this zone, a sedimentary seabed is predominant. Sorted bedforms are well developed and can be detected in water depths in excess of 90m. (iii) An eastern zone, which is characterised by sedimentary seafloor and shore terraces; here, a flat rocky seafloor is covered by a thin layer of sediments. Throughout the study area, the bathymetry and sedimentary features of the shoreface and inner shelf are controlled mainly by climatic conditions, coastal dynamics and the underlying geological framework. The integration of these data sets, together with their interpretation, is a valuable source of information for Integrated Coastal Zone Management (ICZM) and constitutes a useful tool for implementing various European Directives. [Copyright &y& Elsevier]

Abstract: Vertical profiles of particle mass concentration in the urban canopy above the city of Lyon have been obtained from Lidar measurements of atmospheric backscattering, over a period of three days. The concentrations measured at 50 m above the ground have been compared with the mass concentration of PM10 measured by a ground-based sampler located near the Lidar site. At certain times during the measurement campaign, the Lidar concentration measurements at 50 m agree reasonably well with the concentrations at ground level but at other times the differences between the two sets of measurements are so great that they cannot be explained by possible uncertainties in the data processing. Even when the Lidar and ground-based measurements coincide, there are significant differences between the two signals. To explain these differences we have computed the trajectories of the air parcels that pass over the Lidar, using a numerical model for the wind field that takes into account surface features such as relief and changes in roughness. This analysis showed that the differences can be explained by the meteorological conditions (wind speed and direction, vertical profiles of temperature) and the positions of the different sources of particulate matter relative to the measurement site. The combination of Lidar, ground-based sampler and air mass trajectory calculations is shown to be a powerful tool for discriminating between different sources of pollution, which could be useful in enforcing an urban air quality policy. [Copyright &y& Elsevier]

Abstract: The purpose of this paper is to study the relationship between columnar aerosol optical thickness and ground-level aerosol mass. A set of Sun photometer, elastic backscattering lidar and TEOM measurements were acquired during April 2007 in Lille, France. The PM2.5 in the mixed boundary layer is estimated using the lidar signal, aerosol optical thickness, or columnar integrated Sun photometer size distribution and compared to the ground-level station measurements. The lidar signal recorded in the lowest level (240m) is well correlated to the PM2.5 (R 2 =0.84). We also show that the correlation between AOT-derived and measured PM2.5 is significantly improved when considering the mixed boundary layer height derived from the lidar. The use of the Sun photometer aerosol fine fraction volume does not improve the correlation. [Copyright &y& Elsevier]

We investigate in this study the vertical PM10 distributions from mobile measurements carried out from locations along the Paris Peripherique (highly trafficked beltway around Paris), examine distinctions in terms of aerosol concentrations between the outlying regions of Paris and the inner city and eventually discuss the influence of aerosol sources, meteorology, and dynamics on the retrieved PM10 distributions. To achieve these purposes, we combine in situ surface measurements with active remote sensing observations obtained from a great number of research programs in Paris area since 1999. Two approaches, devoted to the conversion of vertical profiles of lidar-derived extinction coefficients into PM10, have been set up. A very good agreement is found between the theoretical and empirical methods with a discrepancy of 3%. Hence, specific extinction cross-sections at 355 nm are provided with a reasonable relative uncertainty lower than 12% for urban (4.5 m2 g-1) and periurban (5.9 m2 g-1) aersols, lower than 26% for rural (7.1 m2 g-1) aerosols, biomass burning (2.6 m2 g-1) and dust (1.1 m2 g-1) aerosols The high spatial and temporal resolutions of the mobile lidar (respectively 1.5 m and 1 min) enable to follow the spatiotemporal variability of various layers trapping aerosols in the troposphere. Appropriate specific extinction cross-sections are applied in each layer detected in the vertical heterogeneities from the lidar profiles. The standard deviation (rms) between lidar-derived PM10 at 200 m above ground and surface network stations measurements was ∼14μg m-3. This difference is particularly ascribed to a decorrelation of mass concentrations in the first meters of the boundary layer, as highlighted through multiangular lidar observations. Lidar signals can be used to follow mass concentrations with an uncertainty lower than 25% above urban areas and provide useful information on PM10 peak forecasting that affect air quality. [ABSTRACT FROM AUTHOR]

Abstract: According to coastal measurements, global mean sea-level has risen at a rate of 1.8mmyr−1 between 1950 and 2000, with large spatial variability at regional scales. Within the Bay of Biscay, trends computed from coastal tide gauges records have revealed that sea-level rise is accelerating over this period of time; this is in agreement with rates obtained from satellite imagery in the open ocean since 1993. The objectives of the present study are: (1) to assess the evidence of the relative sea-level rise on coastal morphology and habitats in the Gipuzkoan littoral zone (Basque coast, northern Spain) for the period 1954–2004, and (2) to evaluate the relative contribution of local anthropogenic versus sea-level rise impacts for explaining inter-supratidal habitat changes. A high-resolution airborne laser altimetry data (LIDAR) has been used to derive a Digital Terrain Model (DTM) of 15-cm vertical resolution. Coastal habitats were mapped for two periods, using historic airborne photography (1954) and high-resolution imagery (2004). Analysis of tide gauge records from Santander (northern Spain) has revealed that relative mean sea-level has been rising at a rate of 2.08±0.33mmyr−1 from 1943 to 2004; this is consistent with sea-level trends from other measurements within the area (St. Jean de Luz and Bilbao), obtained over shorter periods of time, and with previous results obtained in the Bay of Biscay. Based upon this sea-level trend and by means of a LIDAR-based DTM, the results have indicated that the predicted change along the Gipuzkoan coast due to sea-level rise was of 11.1ha within the 50-yr period. In contrast, comparison of historical and recent orthophotography has detected only 2.95ha of change, originated possibly from sea-level rise, and 98ha transformed by anthropogenic impacts. Hence, coastal changes due to sea-level rise might be overwhelmed by excessive human impacts, at the spatial and temporal scales of the analysis. This work highlights that local anthropogenic impact is the major threat to Basque coastal and estuarine habitats, compared with natural erosive processes and global climate change driving forces over recent times. [Copyright &y& Elsevier]

The characterization of high clouds as performed from selected spaceborne observations is assessed in this article by employing a number of worldwide ground-based lidar multiyear datasets as reference. Among the latter, the ground lidar observations conducted at Lannion, Bretagne (48.7°N, 3.5°W), and Palaiseau, near Paris [the Site Instrumental de Recherche par Télédétection Atmosphérique (SIRTA) observatory: 48.7°N, 2.2°E], both in France, are discussed in detail. High-cloud altitude statistics at these two sites were found to be similar. Optical thicknesses disagree, and possible reasons were analyzed. Despite the variety of instruments, observation strategies, and methods of analysis employed by different lidar groups, high-cloud optical thicknesses from the Geoscience Laser Altimeter System (GLAS) on board the Ice, Cloud and land Elevation Satellite (ICESat) were found to be consistent on the latitude band 40°–60°N. Respective high-cloud altitudes agree within 1 km with respect to those from ground lidars at Lannion and Palaiseau; such a finding remains to be verified under other synoptic regimes. Mean altitudes of high clouds from Lannion and Palaiseau ground lidars were compared with altitudes of thin cirrus from the Television and Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS) Path-B 8-yr climatology for a common range of optical thicknesses (0.1–1.4). Over both sites, the annual altitude distribution of thin high clouds from TOVS Path-B is asymmetric, with a peak around 8–9.5 km, whereas the distribution of high clouds retrieved from ground lidars seems symmetric with a peak around 9.5–11.5 km. Additional efforts in standardizing ground lidar observation and processing methods, and in merging high-cloud statistics from complementary measuring platforms, are recommended. [ABSTRACT FROM AUTHOR]

For the first time eye safe lidar measurements were performed at 355 nm simultaneously to in situ measurements in an underground station so as to test the potential interest of active remote sensing measurements to follow the spatiotemporal evolution of aerosol content inside such a confined microenvironment. The purpose of this paper is to describe different methods enabling the conversion of lidar-derived aerosol extinction coefficient into aerosol mass concentrations (PM2.5 and PM10). A theoretical method based on a well marked linear regression between mass concentrations simulated from the size distribution and extinction coefficients retrieved from Mie calculations provides averaged mass to optics'' relations over the campaign for traffic (6.47 × 105 μg m−2) or no traffic conditions (3.73 × 105 μg m−2). Two empirical methods enable to significantly reduce CPU time. The first one is based upon the knowledge of size distribution measurements and scattering coefficients from nephelometer and allows retrieving mass to optics'' relations for well determined periods or particular traffic conditions, like week-ends, with a good accuracy. The second method, that is more direct, is simply based on the ratio between TEOM concentrations and extinction coefficients obtained from nephelometer. This method is easy to set up but is not suitable for nocturnal measurements where PM stabilization time is short. Lidar signals thus converted into PM concentrations from those approaches with a fine accuracy (30%) provide a spatiotemporal distribution of concentrations in the station. This highlights aerosol accumulation in one side of the station, which can be explained by air displacement from the tunnel entrance. Those results allow expecting a more general use of lidar measurement to survey indoor air quality. [Copyright &y& Elsevier]

Abstract: Light Detection and Ranging (LiDAR) provides high resolution horizontal and vertical spatial point cloud data, and is increasingly being used in a number of applications and disciplines, which have concentrated on the exploit and manipulation of the data using mainly its three dimensional nature. LiDAR information potential is made even greater though, with its consideration of intensity. Elevation and intensity airborne LiDAR data are used in this study in order to classify forest and ground types quickly and efficiently without the need for manipulating multispectral image files, using a supervised object-orientated approach. LiDAR has the advantage of being able to create elevation surfaces that are in 3D, while also having information on LiDAR intensity values, thus it is a spatial and spectral segmentation tool. This classification method also uses point distribution frequency criteria to differentiate between land cover types. Classifications were performed using two methods, one that included the influence of the ground in heavily vegetated areas, and the other which eliminated the ground points before classification. The classification of three meanders of the Garonne and Allier rivers in France has demonstrated overall classification accuracies of 95% and 94% for the methods including and excluding the ground influence respectively. Five types of riparian forest were classified with accuracies between 66 and 98%. These forest types included planted and natural forest stands of different ages. Classifications of short vegetation and bare earth also produced high accuracies averaging above 90%. [Copyright &y& Elsevier]

Abstract: We propose a quantification of the downward transport of aerosols from the free troposphere (FT) to the planetary boundary layer (PBL). Aerosols are originally released at the surface as a consequence of anthropogenic activities, biomass burning, soil mobilization, etc. After being vertically transported into the FT, they are exposed to the long-range transport (LRT) and may subside to impact, in turn, surface air pollution in remote places. Using 5400h of routine Lidar observations conducted at the SIRTA observatory in the Paris area (France), we identified 154 free tropospheric aerosol layers continuously monitored during their downward transport into the local PBL. One of these events—associated to a Saharan dust outbreak—is thoroughly documented in a case study. And a climatological analysis of surface PM10 levels recorded at air quality monitoring stations allows the impact of FT to PBL transport of aerosols to be quantified. This source is found to be significant for 15 out of the 16 stations, with average PM10 concentrations 2.14μgm−3 (i.e. 12%) above climatological values after the injection of free tropospheric aerosols into the PBL. [Copyright &y& Elsevier]

This study compares cirrus-cloud properties and, in particular, particle effective radius retrieved by a Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)-like method with two similar methods using Moderate-Resolution Imaging Spectroradiometer (MODIS), MODIS Airborne Simulator (MAS), and Geostationary Operational Environmental Satellite imagery. The CALIPSO-like method uses lidar measurements coupled with the split-window technique that uses the infrared spectral information contained at the 8.65-, 11.15-, and 12.05-μm bands to infer the microphysical properties of cirrus clouds. The two other methods, using passive remote sensing at visible and infrared wavelengths, are the operational MODIS cloud products (using 20 spectral bands from visible to infrared, referred to by its archival product identifier MOD06 for MODIS Terra) and MODIS retrievals performed by the Clouds and the Earth’s Radiant Energy System (CERES) team at Langley Research Center (LaRC) in support of CERES algorithms (using 0.65-, 3.75-, 10.8-, and 12.05-μm bands); the two algorithms will be referred to as the MOD06 and LaRC methods, respectively. The three techniques are compared at two different latitudes. The midlatitude ice-clouds study uses 16 days of observations at the Palaiseau ground-based site in France [Site Instrumental de Recherche par Télédétection Atmosphérique (SIRTA)], including a ground-based 532-nm lidar and the MODIS overpasses on the Terra platform. The tropical ice-clouds study uses 14 different flight legs of observations collected in Florida during the intensive field experiment known as the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL-FACE), including the airborne cloud-physics lidar and the MAS. The comparison of the three methods gives consistent results for the particle effective radius and the optical thickness but discrepancies in cloud detection and altitudes. The study confirms the value of an active remote sensing method (CALIPSO like) for the study of subvisible ice clouds, in both the midlatitudes and Tropics. Nevertheless, this method is not reliable in optically very thick tropical ice clouds, because of their particular microphysical properties. [ABSTRACT FROM AUTHOR]

Systematic cirrus lidar measurements performed in the south of France during 2000 are analyzed statistically to search for cloud classes. The classes are based on cloud characteristics (cloud thickness, light backscattering efficiency, and its variance), cloud absolute geometric height, cloud height relative to the tropopause, and the temperature at the cloud level. The successive use of principal component analysis, cluster methods, and linear discriminant analysis allows the identification of four cirrus classes. Almost all the cirrus detections correspond to three classes with similar proportion of the total cirrus detected (around 30%). The absolute geometric height and the thickness are found to be the main discriminant variables. The first cirrus class corresponds to thin clouds above the local tropopause (absolute geometric height: 11.5 km), or at least around the tropopause, while another class corresponds also to thin clouds but at a lower altitude range in the troposphere (absolute geometric height: 8.6 km). The third class corresponds to thick clouds (thickness of 3.2 km) located below the tropopause, in an altitude range between the two first classes (absolute geometric height: 9.8 km). As expected, the high-altitude cirrus class is characterized with the lowest mean temperature. It is noted that the temperature is closely related to the altitude and so the role of temperature in the cirrus classes cannot be disentangled from the role of the altitude. [ABSTRACT FROM AUTHOR]

• Contributions and complementarities of the different frequencies for detecting 4 types of land use (and two states of bare soils. • The use of one mono-frequency images provides limited overall results. • A significant improvement in the classifications by fusing images delivered by optical and radar sensors, for most of the classes studied. • The complementary nature of the contributions made by L-band and optical waves. The monitoring of different crops (cultivated plots) and types of surface (bare soils, etc.) is a crucial economic and environmental issue for the management of resources and human activity. In this context, the objective of this study is to evaluate the contribution of multispectral satellite imagery (optical and radar) to land use and land cover classification. Object-oriented supervised classifications, based on a Random Forest algorithm, and majority zoning post-processing are used. This study emerges from the experiment on multi-sensor crop monitoring (MCM'10, Baup et al., 2012) conducted in 2010 on a mixed farming area in the southwest of France, near Toulouse. This experiment enabled the regular and quasi-synchronous collection of multi-sensor satellite data and in situ observations, which are used in this study. 211 plots with contrasting characteristics (different slopes, soil types, aspects, farming practices, shapes and surface areas) were monitored to represent the variability of the study area. They can be grouped into four classes of land cover: 39 grassland areas, 100 plots of wheat, 13 plots of barley, 20 plots of rapeseed, and 2 classes of bare soil: 23 plots of small roughness and 16 plots of medium roughness. Satellite radar images in the X-, C- and L-bands (HH polarization) were acquired between 14 and 18 April 2010. Optical images delivered by Formosat-2 and corresponding field data were acquired on 14 April 2010. The results show that combining images acquired in the L-band (Alos) and the optical range (Formosat-2) improves the classification performance (overall accuracy = 0.85, kappa = 0.81) compared to the use of radar or optical data alone. The results obtained for the various types of land cover show performance levels and confusions related to the phenological stage of the species studied, with the geometry of the cover, the roughness states of the surfaces, etc. Performance is also related to the wavelength and penetration depth of the signal providing the images. Thus, the results show that the quality of the classification often increases with increasing wavelength of the images used. [ABSTRACT FROM AUTHOR]