Atmospheric aerosols play very important roles in climate change and air particulate pollution. Lidars based on elastic scattering have been widely used to measure aerosol spatial distribution and to retrieve the profiles of aerosol optical properties by an assumption of the aerosol extinction-to-backscatter ratio. High Spectral Resolution Lidar (HSRL) is one of methods that can be used to measure aerosol optical properties without a-priori hypotheses. Compared to Raman lidar, HSRL has the advantage of day and night measurements and can be adapted to many kinds of carrying platforms.
Unlike ordinary elastic backscatter lidar, HSRL needs to separate the Mie signal scattered by atmospheric aerosol and the Rayleigh signal scattered by atmospheric molecules. Due to small spectral difference between Mie and Rayleigh signals, there are three difficulties: firstly, the laser source must have a narrow bandwidth, high energy and stable center wavelength; secondly, the receiver should have a very narrow spectral filter to separate aerosol scattering and molecular scattering; thirdly, the center wavelength of the receiver must be real-time locked to laser source.
In order to study the influence of system parameters on the measurement accuracy of a high spectral resolution lidar and to optimize their values, a simulation and analysis has been done and will be presented in this paper. In this paper, the system parameters including the linewidth of emission laser, the bandwidth of the Fabry–Pérot interferometric filter in the receiver and the spectral tracking accuracy between the receiver and laser are mainly analyzed. At the same time, several environmental factors have been considered, including atmospheric temperature and wind, pointing accuracy of platform, aerosol concentration range etc. A typical vertical distribution of atmospheric aerosol optical properties is considered and the received signals of high spectral channels are simulated. From the simulated signals, the aerosol optical properties are retrieved and the deviation relative to the input values is obtained. Under the conditions of given environmental factors, the relationship between system parameters of high spectral resolution lidar and relative error of retrieved aerosol optical properties is carried out.
EARLINET, the European Aerosol Research Lidar NETwork, established in 2000, is the first coordinated lidar network
for tropospheric aerosol study on the continental scale. The network activity is based on scheduled measurements, a rigorous quality assurance program addressing both instruments and evaluation algorithms, and a standardised data
exchange format. At present, the network includes 27 lidar stations distributed over Europe.
EARLINET performed almost continuous measurements since 15 April 2010 in order to follow the evolution of the
volcanic plume generated from the eruption of the Eyjafjallajökull volcano, providing the 4-dimensional distribution of
the volcanic ash plume over Europe. During the 15-30 April period, volcanic particles were detected over Central Europe
over a wide range of altitudes, from 10 km down to the local planetary boundary layer (PBL). Until 19 April, the
volcanic plume transport toward South Europe was nearly completely blocked by the Alps. After 19 April volcanic
particles were transported to the south and the southeast of Europe. Descending aerosol layers were typically observed
all over Europe and intrusion of particles into the PBL was observed at almost each lidar site that was affected by the
volcanic plume. A second event was observed over Portugal and Spain (6 May) and then over Italy on 9 May 2010. The
volcanic plume was then observed again over Southern Germany on 11 May 2010.
Lidar techniques represent the most suitable tool to obtain information on the aerosol vertical distribution and therefore
to close this kind of observational gap. Lidar networks are fundamental to study aerosol on large spatial scale and to
investigate transport and modification phenomena. These are the motivations why EARLINET, the European Aerosol
Research Lidar Network, was established in 2000. At present, EARLINET consists of 25 lidar stations: 7 single
backscatter lidar stations, 9 Raman lidar stations with the UV Raman channel for independent measurements of aerosol
extinction and backscatter, and 9 multiwavelength Raman lidar stations (elastic channel at 1064 nm, 532 nm, 355 nm,
Raman channels at 532 nm and 355 nm, plus depolarization channel at 532 nm) for the retrieval of aerosol microphysical
properties.
EARLINET data can significantly contribute to the quantification of aerosol concentrations, radiative properties, long-range
transport and budget, and prediction of future trends on European and global scale. It can also contribute to
improve model treatment on a wide range of scales and to a better exploitation of present and future satellite data.
EARLINET is playing an important role in the validation and in the full exploitation of the CALIPSO mission.
EARLINET started correlative measurements for CALIPSO since June 2006. A strategy for correlative measurements
has been defined on the base of the analysis of the high resolution ground track data provided by NASA. Results in terms
of comparisons between EARLINET and available CALIPSO products, both level 1 and level 2 data, are presented.
The present knowledge of the aerosol distribution is not sufficient to estimate the aerosol influence on global and
regional environmental conditions and climate. This observational gap can be closed by using advanced laser remote
sensing. EARLINET (European Aerosol Research Lidar Network) is the first aerosol lidar network, established in 2000,
with the main goal to provide a comprehensive, quantitative, and statistically significant database for the aerosol
distribution on a continental scale. EARLINET is a coordinated network of European stations (25 at present) using advanced lidar methods for the vertical profiling of aerosols. The network activity is based on simultaneous scheduled
measurements, a rigorous quality assurance program addressing both instruments and evaluation algorithms, and a
standardised data exchange format. Further observations are performed to monitor special events.
EARLINET-ASOS (Advanced Sustainable Observation System) is a five year EC Project started in 2006, based on the
EARLINET infrastructure. The main objectives are: to make EARLINET a world-leading instrument for the observation
of the 4-D aerosol distribution on continental scale; to foster aerosol-related process studies, validation of satellite
sensors, model development and validation, assimilation of aerosol data into operational models; and to build a
comprehensive climatology of the aerosol distribution.
The optical properties and the spatial distribution of the tropospheric aerosols over Naples under Saharan dust outbreaks
conditions have been studied by means of lidar measurements performed between May 2000 and August 2003 in the
frame of the EARLINET project. Climatological analysis of sand plume has been done by comparing normal and dust
affected conditions. Results in terms of backscattering and extinction coefficient as well as their integrated quantities
show that the aerosol load from the ground level up to 2 Km during Saharan dust transport events is almost the same of
normal conditions. This is probably due to the relevant widespread of local aerosol sources, such as vehicular traffic,
industrial activities, etc. Nevertheless, when sand outbreaks occur, the extinction to backscattering ratio, i.e. the lidar
ratio, clearly shows that the aerosol type in the lowest atmospheric layer changes. Moreover, Saharan dust transport
events strong increase both integrated backscatter and optical dept above 2 km.
The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite had been launched in April 2006. Its main goal is to probe the vertical structure and to measure the properties of thin clouds and aerosols plume of the Earth's atmosphere. In order to validate the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) products, correlative measurements between CALIPSO and EARLINET stations have been planned in the framework of the validation campaign. At Napoli EARLINET station correlative measurement have been performed starting from the beginning of June 2006. Results obtained both during daytime with elastic lidar and nighttime with Raman lidar operating at two wavelengths (355nm and 532nm) are shown. The results of the application of a new algorithm to retrieve aerosol basckscattering and extinction coefficient backscattering from space and ground based elastic lidar signals are presented. Case study of Saharan dust outbreaks and cirrus clouds captured during correlative measurement runs are discussed.
During August-October 2005, several lidar measurements have been performed at many Italian lidar stations during the
Launch (International Lindenberg campaign for Assessment of hUmidity aNd Cloud profiling systems and its impact on
High-resolution modelling) campaign according with the IOP (Intensive Operational Period) schedule.
IOP 4 episode (1-3 October 2005) has been selected and investigated with a special attention to the variability of water
vapour mixing ratio vertical distribution to better understand the associated circulation in the coastal waters of the Gulf
of Naples (Tyrrhenian Sea).
A simulation is performed using the mesoscale model MM5 (version 3) model from PSU/NCAR1,2 for this study. Water
vapour mixing ratio observations have been detected in the Naples site (40°50'N, 14°11'E, 118 m asl) by a water vapour
Raman lidar which is also able to measure the backscatter profile at 355 and 532 nm and the extinction profile at 355
nm.
Water vapour mixing ratio vertical profiles retrieved by lidar have been compared with the MM5 water vapour mixing
ratio vertical profiles. The agreement between the model and the lidar data is good; all the modelled and the lidar profiles
are able to capture the cold air intrusion, that is the sharp decrease of the water vapour mixing ratio at about 2000 m.
Also the water-layer between 3000 and 8000 m is well captured. Moreover, both the model and the observations are able
to capture the land/sea breeze phenomena.
The European Aerosol Research Lidar Network (EARLINET) was established in 2000 to derive a comprehensive, quantitative, and statistically significant data base for the aerosol distribution on the European scale.
At present, EARLINET consists of 25 stations: 16 Raman lidar stations, including 8 multi-wavelength Raman lidar stations which are used to retrieve aerosol microphysical properties.
EARLINET performs a rigorous quality assurance program for instruments and evaluation algorithms. All stations measure simultaneously on a predefined schedule at three dates per week to obtain unbiased data for climatological studies.
Since June 2006 the first backscatter lidar is operational aboard the CALIPSO satellite. EARLINET represents an excellent tool to validate CALIPSO lidar data on a continental scale. Aerosol extinction and lidar ratio measurements provided by the network will be particularly important for that validation.
The measurement strategy of EARLINET is as follows: Measurements are performed at all stations within 80 km from the overpasses and additionally at the lidar station which is closest to the actually overpassed site. If a multi-wavelength Raman lidar station is overpassed then also the next closest 3+2 station performs a measurement.
Altogether we performed more than 1000 correlative observations for CALIPSO between June 2006 and June 2007.
Direct intercomparisons between CALIPSO profiles and attenuated backscatter profiles obtained by EARLINET lidars look very promising.
Two measurement examples are used to discuss the potential of multi-wavelength Raman lidar observations for the validation and optimization of the CALIOP Scene Classification Algorithm.
Correlative observations with multi-wavelength Raman lidars provide also the data base for a harmonization of the CALIPSO aerosol data and the data collected in future ESA lidar-in-space missions.
EARLINET-ASOS (European Aerosol Research Lidar Network - Advanced Sustainable Observation System) is a 5-year EC Project started in 2006. Based on the EARLINET infrastructure, it will provide appropriate tools to improve the quality and availability of the continuous observations. The EARLINET multi-year continental scale data set is an excellent instrument to assess the impact of aerosols on the European and global environment and to support future satellite missions. The project is addressed in optimizing instruments and algorithms existing within EARLINET-ASOS, exchanging expertise, with the main goal to build a database with high quality aerosol data. In particular, the optimization of the algorithms for the retrieval of the aerosol optical and microphysical properties is a crucial activity. The main objective is to provide all partners with the possibility to use a common processing chain for the evaluation of their data, from raw signals to final products. Raw signals may come from different types of systems, and final products are profiles of optical properties, like backscatter and extinction, and, if the instrument properties permit, of microphysical properties. This will have a strong impact on the scientific community because data with homogeneous well characterized quality will be made available in nearly real time.
EARLINET, the European Aerosol Research Lidar Network, is the first aerosol lidar network, established in 2000, with the main goal to provide a comprehensive, quantitative, and statistically significant data base for the aerosol distribution on a continental scale. At present, 23 stations distributed over Europe are part of the network. The EARLINET-ASOS (Advanced Sustainable Observation System) EC Project, starting on the EARLINET infrastructure, will contribute to the improvement of continuing observations and methodological developments that are urgently needed to provide the multi-year continental scale data set necessary to assess the impact of aerosols on the European and global environment and to support future satellite missions. The main objective of EARLINET-ASOS 5-year project, started on 1 March 2006, is to improve the EARLINET infrastructure resulting in a better spatial and temporal coverage of the observations, continuous quality control for the complete observation system, and fast availability of standardized data products. This will be reached by defining and using common standards for instruments, operation procedures, observation schemes, data processing including advanced retrieval algorithms, and dissemination of data. The expected outcome is the most comprehensive data source for the 4-D spatio-temporal distribution of aerosols on a continental scale.
The international experiment EAQUATE (European AQUA Thermodynamic Experiment) was held in September 2004 in Italy and in the United Kingdom. The Italian phase, performed in the period 6-10 September 2004, was mainly devoted to assessment and validation of performances of new IR hyperspectral sensors and benefits from data and results of measurements of AQUA and in particular of AIRS. It is also connected with the preparatory actions of MetOp mission with particular attention to calibration and validation of IASI products (as water vapour and temperature profiles), characterization of semitransparent clouds and study of radiative balance, demonstrating the role of ground-based and airborne systems in validation operations.
The Italian phase of the campaign was carried out within a cooperation between NASA Langley Research Center, University of Wisconsin, the Istituto di Metodologie per l'Analisi Ambientale (CNR-IMAA), the Mediterranean Agency for Remote Sensing (MARS) and the Universities of Basilicata, Bologna and Napoli. It involved the participation of the Scaled Composites Proteus aircraft (with NAST thermal infrared interferometer and microwave radiometer, the Scanning HIS infrared interferometer, the FIRSC far-IR interferometer), an Earth Observing System-Direct Readout Station and several ground based instruments: four lidar systems, a microwave radiometer, two infrared spectrometers, and a ceilometer. Radiosonde launches for measurements of PTU and wind velocity and direction were also performed as ancillary observations. Four flights were successfully completed with two different AQUA overpasses. The aircraft flew over the Napoli, Potenza and Tito Scalo ground stations several times allowing the collection of coincident aircraft and in- situ observations.
Systematic Lidar measurements of tropospheric aerosols optical properties have been carried out in the urban area of Napoli (Southern Italy, 40°50’18”N, 14°10’59”E, 118 m above sea level), in the framework of EARLINET project. Lidar systematic measurements of aerosol backscattering and extinction profiles have been performed at laser wavelength of 351nm and were obtained from simultaneously measurements of elastic and N2 Raman signals. Following the EARLINET protocol, regular measurements have been performed three times a week in two days and they provide information on aerosol optical properties, with a final spatial resolution of 60m and a temporal resolution between 1 and 30 min. A statistical analysis in terms of integrated backscattering (BI), optical depth (OD), extinction to backscattering ratio (LR), and Dust Layer height (DL), obtained from measurements carried out in clear sky conditions over 30 months, has been realized. Further measurements have been performed during Saharan Dust transport events and some detailed observation of complete diurnal cycle has been carried out, in order to know the dynamic and the evolution of the Planetary Boundary Layer
We report on the investigation of XeF excimer laser ablation of YNi2B2C target by energy selective time-of-flight mass spectrometry (ES-TOFMS). ES-TOFMS allows laser plume investigation by providing a direct measurement of the ions kinetic energy and, through the TOF measurement, their simultaneous mass identification. In particular, the composition and the kinetic energy of the emitted ions has been accomplished by means of TOF technique coupled with a 1600 electrostatic energy analyzer. The analysis of the charged species composition and kinetic energy has been performed at different laser fluences and in high vacuum conditions.
In this paper we present an intercomparison between ground based lidar, radiosonde and satellite atmospheric water vapor measurements. Comparisons expressed in terms of water vapor profiles, obtained by Raman lidar and simultaneous ballonborne radiosonde, are reported and discussed. The deviation between the two profiles is smaller than 10 percent up to an altitude of 5 km. Furthermore, the intercomparison between lidar and radiosonde data and between lidar and satellite data is performed also in terms of water vapor columnar content. The agreement between lidar and radiosonde columnar content is better than 4 percent. Water vapor contour map are showed in order to demonstrate the high spatial and temporal variability of water vapor in the lower atmosphere. Difficulties in comparing lidar and satellite water vapor columnar contents associated to H2O spatial and temporal variability are discussed in the paper.
We report on prompt emission of fast electrons occurring during nanosecond excimer laser ablation of metallic targets in vacuum. Prompt electrons yield and most probable kinetic energy as a function of the laser pulse fluence have been obtained by charge collection and time of flight techniques. The experimental data show a strong dependence of the prompt electrons yield on laser fluence. In particular, the data follow a power law dependence with two distinct slopes, below and above approximately equals 5 Jcm-2. Also the ion yield shows a similar behavior. The observed roll-off in the electron and ion dependence on the laser fluence has been discussed in terms of laser fluence has been discussed in terms of laser plasma shielding effects.
A lidar system able to measure simultaneously different atmospheric parameters in the lower troposphere have been developed and used to monitor the air quality of an industrial area of Southern Italy. The system is based on a Nd:YAG laser pumping two dye lasers, and on two Newtonian telescopes, equipped with periscopes for 3D mapping. One telescope is devoted to DIAL and the other to the N2 and H2O Raman channels, and to the elastic channels at 1064 nm, 532 nm and 355 nm. Aerosol backscattering coefficients measurements have evidenced the presence of an aerosol layer. The laser has been characterized by measuring its temporal evolution and by correlating it with atmospheric transmissivity profiles measured at different zenithal angles. Preliminary results of atmospheric pollutants concentration measurements by UV DIAL technique are also reported.
A new multiparametric lidar system spanning from UV to mid IR is presently under testing. The system is based on two Optical Parametric Amplifier (OPA) lasers pumped by a Nd:YAG laser operating at a maximum pulse repetition rate of 100 Hz. OPA lasers represent a new design for coherent radiation sources continuously tunable in the UV-IR range. The large range of tunability of OPA lasers allows to perform Differential Absorption Lidar measurements in a spectral region where most of atmospheric pollutants display absorption lines. The system has been designed to deliver simultaneously in the atmosphere the Nd:YAG fundamental and its harmonics (II and III) as well as the four output beams of the two OPA lasers. The return signals, collected by means of two Newtonian telescopes, can be used to retrieve information on: atmospheric aerosols, water vapor and pollutants concentration, atmospheric temperature, density and transmissivity profiles. In this paper a detailed description of the system is reported. Moreover, some results obtained by a multiparametric system (based on a Nd:YAG pumped dye laser) are reported to show the capabilities of a multiwavelength lidar system.
A lidar system with the characteristic of simultaneously monitoring several atmospheric parameters such as atmospheric aerosols load, water vapor content, temperature and density, atmospheric transmissivity, and atmospheric pollutants concentration, has been realized. This system, based on two OPA lasers pumped by a Nd:YAG laser operating at maximum repetition rate of 100 Hz, is primary dedicated to tropospheric measurements. The system is continuously tunable over the spectral range 410 nm - 2500 nm, allowing DIAL measurements in a region where most of atmospheric pollutants display absorption lines. Preliminary measurements have been carried out. We report the simultaneous temporal evolution of the aerosol backscattering coefficient profiles at 355 nm and 829 nm in a rural area. A method to select optimal couples of wavelength for DIAL measurements in the near/mid IR spectral region has been developed. A sensitivity analysis has been carried out in order to find the minimum detectable concentration, that has been demonstrated of the order of few tenths up to few part per million in volume.
The present paper is devoted to the description of two distinct multiparametric lidar system presently under development. The first system is based on a Nd:YAG laser pumping a dye laser equipped with a dual wavelength device. The second lidar system is based on two optical parametric oscillator (OPO) lasers pumped by a Nd:YAG laser operating at a pulse repetition rate of 100 Hz. OPO lasers represent a new design for coherent radiation sources continuously tunable in the UV -- near IR range (up to 2 micrometer). This allows us to perform differential absorption lidar (DIAL) measurements in a spectral region where most of atmospheric pollutants display absorption lines. The selection of the wavelengths to be used for DIAL measurements is a non trivial task. In particular, a method to select the optimal (lambda) ON and (lambda) OFF has been developed and applied to several molecular gases. Both systems have been designed to carry out simultaneous measurements of atmospheric aerosols, water vapor profiles, temperature and density profiles, atmospheric transmissivity, and atmospheric pollutants concentration.
Simultaneous water vapor measurements from satellite and ground based systems, have been performed in Napoli and Potenza throughout the last two years. Night-time water vapor profiles were provided by two lidar systems based on the Raman technique. The lidar system in Napoli, Italy is based on Xe:F excimer laser ((lambda) equals 351 nm), the system in Potenza, Italy is based on a Nd:YAG laser operating both on the 2nd (532nm) and 3rd (355nm) harmonics. Precipitable water (PW) measurements were provided during daytime by a grating spectrometer observing solar spectral irradiance at differentially absorbing channels in the wing of (rho) (sigma) (tau) water vapor band. Night and daytime PW measurements were provided using TOVS and AVHRR packages flying on NOAA satellites. Split window technique on two differentially absorbing AVHRR channels in the 11 micrometers region has been used in order to provide PW amounts with a spatial resolution of approximately 2 Km. The standard ITPP processing for TOVS package has been used in order to obtain PW estimates at lower spatial resolution (about 40 Km). Night and daytime radiosonde measurements have been performed during the last part of the campaign. All the simultaneous independent measurements have been analyzed and the results compared.
The lidar in-space technology experiment (LITE) has been developed at the NASA Langley Research Center to fly on the Space Shuttle and demonstrate the utility of lidar systems in space. An extensive correlative measurements campaign to validate LITE measurements with coincident measurements made with reliable ground-based and balloon-borne sensors was carried out both in Napoli and Potenza in the period September 10-19, 1994. The lidar in Napoli is based on a Xe:F excimer laser (351 nm), while the lidar in Potenza is based on a Nd:YAG laser operating both on the 2nd (532 nm) and 3rd (355 nm) harmonic. During this intense campaign we performed both elastic and Raman measurements for molecular nitrogen. Solar irradiance spectra at ground level were measured by an Optical Spectra Analyzer in the spectral region 0.4-1.1 micrometers , obtaining both columnar water vapor and aerosol load. Aerosol backscattering data will be presented. Elastic and nitrogen Raman signals are used for measuring atmospheric transmissivity. Finally the density and temperature profiles obtained from the simultaneous measurement of the elastic and the N2 Raman signal will be presented. Simultaneous radiosonde measurements of temperature, pressure, and relative humidity will be used to compare lidar data.
KEYWORDS: Ions, Ionization, Xenon, Probability theory, Chemical species, Picosecond phenomena, Pulsed laser operation, Chemical lasers, Spectroscopy, Gas lasers
The intensity dependence of the multiphoton ionization spectra of Xenon atoms has been investigated with an improved accuracy and well controlled laser parameters. In particular, we have examined the ionization rates for Xe3+, Xe2+, X+ as functions of the laser intensity and gas pressure in the target chamber. The apparatus used for these measurements is characterized by a high energy resolution and a completely digital acquisition system. The ionization rates of the different ions have been used for testing the basic assumptions of the Geltman theory of multiple ionization based on the single electron ionization model.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.