Observing the Forest Canopy with a New Ultra-Violet Compact Airborne Lidar

We have developed a new airborne UV lidar for the forest canopy and deployed it in the Landes forest (France). It is the first one that: (i) operates at 355 nm for emitting energetic pulses of 16 mJ at 20 Hz while fulfilling eye-safety regulations and (ii) is flown onboard an ultra-light airplane for enhanced flight flexibility. Laser footprints at ground level were 2.4 m wide for a flying altitude of 300 m. Three test areas of ∼500 × 500 m2 with Maritime pines of different ages were investigated. We used a threshold method adapted for this lidar to accurately extract from its waveforms detailed forest canopy vertical structure: canopy top, tree crown base and undergrowth heights. Good detection sensitivity enabled the observation of ground returns underneath the trees. Statistical and one-to-one comparisons with ground measurements by field foresters indicated a mean absolute accuracy of ∼1 m. Sensitivity tests on detection threshold showed the importance of signal to noise ratio and footprint size for a proper detection of the canopy vertical structure. This UV-lidar is intended for future innovative applications of simultaneous observation of forest canopy, laser-induced vegetation fluorescence and atmospheric aerosols

Dust aerosol profiling by ground-based and airborne lidar in the framework of FENNEC

The FENNEC program aims to improve our knowledge of both the role of the Saharan Heat Low (SHL) on the West African monsoon and the interactions between the African continent and the Mediterranean basin through the Saharan dust transport. The Saharan desert is the major source of mineral dust in the world and may significantly impact the air quality over the Western Europe by increasing the particular matter content. Two lidar systems were operated by the French component of the FENNEC project: an airborne lidar which was flown aboard the French Falcon 20 research aircraft and a ground-based lidar which was located in the southeastern part of Spain, close to Marbella. A major dust plume originating from multiple emission sources (Mauritania, Morocco, and Algeria) and ultimately transported over southern Spain at the end of June 2011 was observed by the two systems

Iaoos Observations of Aerosols and Clouds in the High Arctic by Autonomous Drifting Lidar Platforms

International audienceNew drifting platforms have been deployed within the French project IAOOS (Ice-Atmosphere-Ocean Observing System) in the Arctic since 2014. Radiation and meteorological parameters are measured at the surface and profiles of aerosol and cloud properties are obtained with autonomous backscatter lidar systems. These platforms are indeed equipped for ocean-ice-atmosphere studies over the Arctic to better understand processes and interactions controlling sea-ice changes [1]. As stations in the Arctic are sparse, they can also be used as reference measurements for satellite observations. They are deployed in the Arctic almost every year and allow to perform regular measurements of the vertical structure and optical properties of the atmosphere in complement to satellite observations. Other data on snow, ice and ocean are simultaneously measured. Comparisons were made with CALIPSO/CALIOP observations. Measurements on the atmosphere are presented and results are discussed

IAOOS observations of aerosols and clouds in the high Arctic bu autonomous drifting lidar platforms

International audienc

La canopée forestière vue par un lidar aéroporté de nouvelle génération

National audienceA newly developed UV lidar aboard an ultralight airplane provides detailed vegetation characterization

Dust aerosol optical properties using ground-based and airborne lidar in the framework of FENNEC

International audienceThe FENNEC program aims to improve our knowledge of both the role of the Saharan Heat Low (SHL) on the West African monsoon and the interactions between the African continent and the Mediterranean basin through the Saharan dust transport. The Saharan desert is the major source of mineral dust in the world and may significantly impact the air quality over the Western Europe by increasing the particular matter content. Two lidar systems were operated by the French component of the FENNEC project: an airborne lidar which was flown aboard the French Falcon 20 research aircraft and a ground-based lidar which was located in the southeastern part of Spain, close to Marbella. The presence of dust in the Saharan atmospheric boundary layer has been easily highlighted using the lidars and confirmed by ground-based sunphotometer and observations from both MODIS and SEVIRI spaceborne instruments. The simultaneous use of the sunphotometer-derived Angstrom exponent and the lidar-derived backscatter to extinction ratio is appeared to be a good approach to separate the optical contribution of dust from local aerosols for the coastal site. Over Spain, the dust layer was mainly located above the planetary boundary layer with several kilometers thick. Over the tropical Atlantic Ocean and the Mauritania the airborne lidar shows a high planetary boundary layer (~5 km above the mean sea level) associated to strong aerosol optical thickness (> 0.8 at 532 nm). The airborne lidar data have been inverted using both MODIS and SEVIRI-derived aerosol optical thickness. The differences between dust optical properties close to and remote from the sources will be discussed

La canopée forestière vue par un lidar ultra-violet aéroporté de nouvelle génération

Un effort conjoint de l'Institut Pierre Simon Laplace (LMD, LSCE et LATMOS), du Cemagref et du Commissariat à l'Energie Atomique (CEA), a conduit à mettre en oeuvre le nouveau prototype Lidar Atmosphérique UltraViolet Aéroporté (LAUV(A)) afin d'étudier la répartition verticale de la canopée forestière dans la région des Landes, aux abords du bassin d'Arcachon et de Mimizan. Ce lidar compact et polyvalent embarqué sur ULM permet d'effectuer des mesures avec une maniabilité inégalée, de disposer d'une grande capacité d'adaptation des paramètres instrumentaux (divergence, champ de vue, énergie émise, résolutions verticale et horizontale, angle de visée) et d'effectuer des plans de vol complexes. L'utilisation d'une longueur d'onde dans l'ultra-violet, à 355 nm, permet l'émission d'impulsions énergétiques (16 mJ à 20 Hz) tout en conservant la sécurité oculaire. Les principaux résultats de cette première expérience sont orientés vers une caractérisation statistique des structures verticales (hauteur et distribution verticale de la canopée et sous-bois) des parcelles arborées. Trois parcelles d'environ 500 x 500 m2, composées principalement de pins maritimes de plusieurs âges, ont été échantillonnées suivant différentes configurations expérimentales. Les résultats obtenus constituent des travaux amont nécessaires à la préparation de futures missions lidar spatiales dédiées à l'étude des canopées forestières à l'échelle globale. / A French effort of the Institut Pierre Simon Laplace (LMD, LSCE and LATMOS), the Cemagref and the Commissariat à l'Energie Atomique (CEA) has led to the deployment of a new airborne lidar prototype (LAUV(A), Lidar Atmosphérioque UltraViolet Aéroporté) to study the vertical distribution of the forest canopy in the Landes region in the southwest of France, around the Arcachon basin and Mimizan. This compact and polyvalent lidar onboard an ULA is capable of measuring the forest canopy with an unequalled malleability, both in terms of adaptability of instrumental parameters (divergence, field of view, sensitivity, pointing angle) and flight plan (measuring range and field exploration). The use of an ultra-violet wavelength at 355 nm enables eye-safe emission of energetic laser pulses (16 mJ at 20 Hz). During this experience, the vegetation vertical structure (canopy height and vertical distribution, bushes and sub-wood) of tree parcels was statistically characterized. Three parcels of approximately 500 x 500 m2 composed principally by maritime pines of several ages were sampled following different experimental configurations. These new results contribute, as a first step, to the preparation of future lidar spaceborne missions dedicated to the forest canopy studies at the global scale

355-nm high spectral resolution airborne lidar LNG: system description and first results

International audienceA high spectral resolution (HSR) measurement capability in the ultraviolet has been added to the 3-wavelength-2-polarization-backscatter lidar LNG (lidar aerosols nouvelle génération) and tested during several flights. The system includes a Mach–Zehnder interferometer (MZI) as a spectral discriminator and does not require any frequency locking between the emitter and the interferometer. Results obtained during test flights show that the backscatter and extinction coefficients at 355 nm can be measured with a relative precision of 10% for 60 m and 240 m vertical resolution, respectively, in aerosol layers of 10−6m−1 sr−1 backscatter coefficient with a 30-km horizontal resolution. The same relative precision is obtained in cirrus clouds of a 2×10−5m−1sr−1 backscatter coefficient for the same vertical resolution and a horizontal resolution reduced to 5 km. The capacity of the system to perform wind velocity measurements is also demonstrated with precisions in the range of 1 to 2  ms−1. Particle-to-total backscatter ratio and line-of-sight speed measurements have been performed on ground echoes; averaged data show biases less than 1% and 0.15  ms−1, respectively