Showing papers by "Adolfo Comerón published in 2008"

One-wavelength two-component laser Doppler velocimeter system for surface displacement monitoring

Abstract: A two-component laser Doppler velocimeter (2D-LDV) prototype for surface-displacement measurement is presented. The system proposed is based on the Doppler differential technique with a backwardscattering configuration. A reference and two frequency-shifted probe beams are generated departing from a single laser beam by means of two beamsplitters and acousto-optic modulators. This configuration has the advantage of using a single-wavelength laser source and a single detector system, while permitting sign detection of the two vector components of the velocity in surface-displacement measurements. It also enables the implementation of a low-cost multitrigger data acquisition system, which is useful in low signal-to-noise ratio (SNR) situations, such as the velocity measurement of low-dispersion surfaces or in hydrodynamic applications. The prototype has been designed to measure velocities up to 3 m per second, both in industrial (solid target) and hydrodynamic applications, with an error well below 1% in the tests performed. The system works in real time with the use of an acquisition card and C++ based software on a PC.

The European Aerosol Research Lidar Network (EARLINET): An Overview

Abstract: The European Aerosol Research LIdar NETwork (EARLINET) is the first aerosol lidar network on a continental scale with the main goal to provide a comprehensive, quantitative, and statistically significant database for the aerosol distribution over Europe. Next, we present EARLINET along with the main network activities.

Planetary Boundary Layer Height and Wind Field Characterization by Means of a Lidar at the Teide Observatory in the Canary Islands

Abstract: A lidar field campaign was performed between 30th June and 4th July 2007 in the Teide Observatory in the Canarian island of Tenerife to characterize the atmosphere of this astrophysical observation site in terms of nocturnal boundary layer height and wind fields. The nocturnal boundary layer height was found lower than 810 m in all cases and the aerosol optical thickness lower than 0.005 and 0.03 at 1064 and 532 nm, respectively. Wind fields could hardly be retrieved because of faint signals and very weak wind velocities observed during the campaign.

Earlinet Approach to Optimisation of Individual Network Instruments with the Aim of Homogenisation of Aerosol Data Products and Increased Data Coverage

Abstract: The European Aerosol Research LIdar NETwork (EARLINET) is an aerosol lidar network on a continental scale. EARLINET is now a leading network in quality-controlled quantitative aerosol profiling performing a schedule of routine measurements and presently consists of 28 stations distributed over Europe. The construction of an un-biased spatio-temporal database of vertical profiles of aerosol optical properties on a regional scale for climate and air quality research is the main objective of EARLINET and is accomplished through application of Raman lidars. One of the tasks in the EC-funded project EARLINET-ASOS is to optimize individual instruments with the aim of homogenization of aerosol data products over the network and increased data coverage by automation. This task is approached by selection of optimal solutions existing in the pool of individual stations. This is done for components, subsystems as well as for system integration. In system integration emphasis lies on automation to reduce the amount of manpower needed, to improve temporal coverage, and to make performance independent from individual operators. The procedure to perform these tasks is outlined and the set of tools enabling the assessment of performance under development is described.

Comparison between the Kalman and the Non-Linear Least-Squares Estimators in Low Signal-to-Noise Ratio Lidar Inversion

Abstract: This works departs from previously published results of the authors and focus on joint estimation and time evolution of the atmospheric backscatter profile and a range-independent lidar ratio by means of 1) adaptive extended Kalman filtering (EKF) and 2) non-linear least-squares (NLSQ), under moderate-to-low signal-to-noise ratios (SNR<100 at the starting sounding range). A Rayleigh/Mie atmosphere and a calibrated lidar system are considered. Performance parameters studied are data sufficiency, tracking of the optical parameter time fluctuations, inversion errors, power estimation, and noise impact. The EKF inversion solution is, in turn, compared with Klett's method as a reference. Finally, it is shown that the EKF outweighs the NSLQ in noisy environments.

Overview of Wind Lidar Techniques and Current Related Developments at the Technical University of Catalonia

Abstract: The Lidar group in the Technical University of Catalonia is actively working in wind lidar techniques. An extensive review of such techniques is presented. A special emphasis is made on the direct Doppler technique and the direct motion technique with a lines-of-sight scanning pattern. Current developments are also mentioned.