This PDF file contains the front matter associated with SPIE Proceedings Volume 8894, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

A range-resolving continuous wave Doppler Lidar is presented based on principles of optical low-coherence re- flectometry (OLCR) and using a source with a bandwidth in the MHz range. As opposed to OLCR the range scanning is not done by changing the length of the reference path in the interferometric setup. Rather, a CW source with synthetic phase noise is used enabling numerical range scanning after each single measurement. The latter feature also is in sharp contrast to conventional CW Lidar. Our concept can be applied to wind sensing as well as to remote vibrometry and differential absorption Lidar.

Wind sensing Lidar is considered a promising technology for high quality wind measurements required for various applications such as hub height wind resource assessment, power curve measurements and advanced, real time, forward looking turbine control. Until recently, the only available Lidar technology was based on coherent Doppler shift detection, whose market acceptance has been slow primarily due to its exuberant price. Direct detection Lidar technology provides an alternative to remote sensing of wind by incorporating high precision measurement, a robust design and an affordable price tag.

The accurate vertical CO₂ profiles in the troposphere are highly desirable in the inverse techniques to improve quantification and understanding of the global budget of CO₂ and also global climate changes. Moreover, wind information is an important parameter for transport simulations and inverse estimation of surface CO₂ flux. A differential absorption lidar (DIAL) is an attractive method for obtaining vertical CO₂ profiles and we have developed an 1.6μm DIAL system to perform simultaneous measurements of CO₂ concentration, atmospheric temperature profile and wind profile. The absorption cross sections of gas and air density depends on atmospheric temperature and pressure. Then precise temperature and pressure profiles are necessary for accurate CO₂ mixing ratio measurement by DIAL. Laser beams of three wavelengths around a CO₂ absorption line are transmitted alternately to the atmosphere for simultaneous measurements of CO₂ concentration and temperature. The receiving optics include the near-infrared photomultiplier tube and a fiber Bragg grating (FBG) filter to detect a Doppler shift.

Accurate knowledge of gas composition in volcanic plumes has high scientific and societal value. On the one hand, it gives information on the geophysical processes taking place inside volcanos; on the other hand, it provides alert on possible eruptions. For this reasons, it has been suggested to monitor volcanic plumes by lidar. In particular, one of the aims of the FP7 ERC project BRIDGE is the measurement of CO₂ concentration in volcanic gases by differential absorption lidar. This is a very challenging task due to the harsh environment, the narrowness and weakness of the CO₂ absorption lines and the difficulty to procure a suitable laser source. This paper, after a review on remote sensing of volcanic plumes, reports on the current progress of the lidar system.

Volcanic CO₂ emissions are an important element of the carbon cycle, but they are very poorly constrained. This is due to the great challenge posed by the quantification of a potentially small volcanic CO₂ signal against a strong background atmospheric signal. There is therefore great interest in developing and applying novel, sensitive techniques which may be able to remotely quantify trace volcanic CO₂ amounts. Differential Absorption LIDAR (DIAL) is one such technique which may allow remote monitoring of volcanic CO₂ emissions. CO₂ is typically the second most abundant volcanic gas, the first being H₂O, which can condense upon emission, producing dense aerosol clouds. These aerosols will strongly affect absorption and backscattering of the probing DIAL light. We employ Mie's equations to calculate their scattering and extinction properties. We consider two extreme droplet number densities. We find that both backscattering and extinction coefficient increase by more than 4 orders of magnitude with respect to the case without any liquid water in the volcanic plume. The fraction of light scattered back to the DIAL instrument in a single scattering event increases by a factor of 100 relative to the clear atmosphere. For the LIDAR signal this implies a relative increase in backscattered light by up to 4 and 5 orders of magnitude for the low density and high density cloud scenario, respectively. The results suggest that a condensed water cloud within the plume region may act as a strong reflector, and greatly enhances the signal strength and hence sensitivity of a DIAL system compared with backscattering in the clear atmosphere.

Eye safe laser operation of resonantly pumped Er:YAG laser systems is demonstrated in cw and Q-switched operation. Using narrow bandwidth diode laser modules we realized a single pump configuration providing an optical efficiency of about 30% which leads to an output power of 2.5 in cw mode and 6.6 mJ in Q-switched operation with a pulse width of 60 ns at pulse repetition frequencies of up to 125 Hz. By implementing an intra-cavity etalon we were able tune the laser wavelength while achieving a spectral width of 0.35 pm and a long-term frequency fluctuation of about 40 MHz. In dualside pumping configuration we obtained dual-wavelength pumping with 1532 nm and 1455 nm diode lasers which leads to 1.1 W output power. Compared to single wavelength pumping, the efficiency of the laser system was doubled. The feasibility of methane detection was demonstrated In cw and pulsed mode.

Vegetation LIDAR, which measures an accurate canopy height, has been studied by JAXA. Canopy height is a very important parameter to estimate forest biomass, and global measurement of accurate canopy height leads to better understanding of the global carbon cycle. The vegetation LiDAR is designed based on the assumption that it is to be mounted on the Exposed Facility (EF) of the Japanese Experiment Module (JEM, also known as “Kibo”) on the International Space Station (ISS). The vegetation LIDAR uses an array detector (2x2) for dividing the ground footprint, making it possible to detect the slope of the ground for improving the accuracy of canopy height measurement. However, dividing the footprint may cause a reduction in reflected lights and signal-to-noise ratio (SNR); hence, the vegetation LiDAR system needs high sensitivity and low-noise array detector module. We made a prototype of the array detector module and it satisfied the tentative target SNR which we set. This presentation will introduce the mission objectives, the LiDAR system including experimental prototypes of array detector module, and some results of the study.

High-accuracy three-dimensional (3D) information of global area is useful in various fields, such as global observations of canopy height, elevation and ice sheet. Especially, there are pressing needs to advance understanding of how changes in the 3D structure of terrestrial vegetation are affecting the global carbon dynamics and their implications for climate change. Thus new space based observations are needed to measure global maps of the 3D structure of vegetation. Japan Aerospace Exploration Agency has started a conceptual study of the spaceborne vegetation LiDAR called MOLI (Multi- Footprint Observation LiDAR and Imager) which will enable us to obtain high-accuracy 3D information of vegetation areas from the globe. To investigate waveforms and analysis procedure, the waveform-simulator for MOLI was developed. Comparing with previous studies about the canopy height estimation from GLAS waveforms, waveform analysis procedure in which waveforms were fitted with a sum of Gaussian functions was studied. The maximum canopy height error was divided into two components; the basic error (E_B) which was not depending on terrain index (TI), which was the vertical difference between the highest and lowest elevation within a footprint, and the error depending on TI (E_TI). The total error (E_Total) could be RMS of the two. We propose E_Total in which E_B is 1 m and E_TI is 1/3*TI as a target observation accuracy of MOLI. According to this error estimation, the observation accuracy of MOLI is 1m at a plane area (TI ≈ 0) and 3 m at slope area up to about 20 degree.

Recently surveying large areas in an automatic way, for early detection of harmful chemical agents, has become a strategic objective of defence and public health organisations. The Lidar-Dial techniques are widely recognized as a cost-effective alternative to monitor large portions of the atmosphere but, up to now, they have been mainly deployed as ground based stations. The design reported in this paper concerns the development of a Lidar-Dial system compact enough to be carried by a small airplane and capable of detecting sudden releases in air of harmful and/or polluting substances. The proposed approach consists of continuous monitoring of the area under surveillance with a Lidar type measurement. Once a significant increase in the density of backscattering substances is revealed, it is intended to switch to the Dial technique to identify the released chemicals and to determine its concentration. In this paper, the design of the proposed system is described and the simulations carried out to determine its performances are reported. For the Lidar measurements, commercially available Nd- YAG laser sources have already been tested and their performances, in combination with avalanche photodiodes, have been experimentally verified to meet the required specifications. With regard to the DIAL measurements, new compact CO₂ laser sources are being investigated. The most promising candidate presents an energy per pulse of about 50 mJ typical, sufficient for a range of at least 500m. The laser also provides the so called "agile tuning" option that allows to quickly tune the wavelength. To guarantee continuous, automatic surveying of large areas, innovative solutions are required for the data acquisition, self monitoring of the system and data analysis. The results of the design, the simulations and some preliminary tests illustrate the potential of the chosen, integrated approach.

We present experimental results obtained in the frame of the QOMA project involving the design and development of a diode-pumped solid state (DPSS) Nd:YAG laser, operating at passively and actively Q-switched pulsed mode. Continuous wave (cw) and passively Q-switched operations are demonstrated obtaining 7.5 W and 2 mJ at 100 Hz, respectively with excellent beam quality using a multi-segmented (0.1%, 0.23%, 0.6% at Nd) Nd:YAG crystal. Comparisons with a uniform Nd:YAG rod reveals improvements of up to 64% in normalized optical conversion efficiency and 67% in output power for retaining the same beam quality. Active Q-switching operation was also obtained with the same multi-segmented crystal, demonstrating pulse energy of 1.20 mJ at 5 kHz repetition rate, preserving an almost Gaussian beam profile.

In this paper, we report on a novel method for measurements of atmospheric temperature profiles during daytime from 2 km up to 15.3 km with a vertical resolution between 0.3 km to 2.2 km by lidar (light detection and ranging) using Rayleigh-Brillouin scattering. The spectra of Rayleigh-Brillouin scattered light are measured by scanning a laser (λ = 355 nm) over a 12 GHz range and using a single Fabry-Perot interferometer as frequency discriminator. Temperature is derived by analyzing the measured Rayleigh-Brillouin spectra with an analytical line shape model and assuming standard-atmospherical pressure conditions. Two exemplary temperature profiles resulting from measurements over 14 min and 27 min are shown. A comparison to radiosonde temperature measurements show reasonable agreement. The temperature difference reaches up to 5 K within the boundary layer and is smaller than 2.5 K above. The statistical error is calculated with a maximum likelihood estimator and varies between 0.15 K and 1.5 K.

Polly^NET is a growing global network of automatized multiwavelength polarization Raman lidars of type Polly (Althausen et al., 2009). The goal of this network is to conduct advanced remote measurements of aerosol profiles and clouds by the same type of instrument. Since 2006 this network assists the controlling and adjustment activities of Polly systems. A central facility receives the data from the Polly measurements. The observational data are displayed in terms of quicklooks at http://polly:tropos.de in near real time. In this way, the network serves as a central information platform for inquisitive scientists. Polly^NET comprises permanent stations at Leipzig (Germany), Kuopio (Finland), Evora (Portugal), Baengnyeong Island (South Korea), Stockholm (Sweden), and Warsaw (Poland). Non-permanent stations have been used during several field experiments under both urban and very remote conditions - like the Amazon rainforest. These non-permanent stations were lasting from several weeks up to one year and have been located in Brazil, India, China, South Africa, Chile, and also aboard the German research vessels Polarstern and Meteor across the Atlantic. Within Polly^NET the interaction and knowledge exchange is encouraged between the Polly operators. This includes maintenance support in system calibration procedures and distribution of latest hardware and software improvements. This presentation introduces the Polly^NET. Main features of the Polly systems will be presented as well as recent instrumental developments. Some measurement highlights achieved within Polly^NET are depicted.

Atmospheric aerosols play a key role on climate balance (direct, semi-direct and indirect effects), on human health (increase of breathing problems and lung cancer for pollution aerosols) and human activities (damage to aircraft engines by volcanic ashes, reduction of visibility by dust or pollution aerosols). In order to monitor and characterize this threat it is necessary to localize, characterize and possibly quantify the presence of aerosols in the atmosphere from the lowest layers (~100 m) up to the tropopause (18 km). We use here an approach based on measurements of the new Raman and dual-polarization LiDAR R-Man510. We present in this paper how it is possible to detect atmospheric layers, to retrieve their optical properties and to classify these layers with this sensor.

The vertical stratification and optical characteristics of aloft aerosol plumes are critical to evaluate their influences on climate radiation and air quality. In this study, we demonstrate the synergistic measurements of aloft aerosol plumes by a ground-based NOAA-CREST lidar network (CLN) along the US East Coast, the AERONET-sun/sky radiometer network at lidar sites, and satellite observations. During the plume intrusion period on March 6, 2012, the CLN and AERONET measurements were consistent in illustrating the onset of dust aerosol plumes. We observed two-layers of aerosol located at 1.0 ~ 8.0 km altitude. The column-average volume size distributions show increasing concentration of both fine- and coarse-modes aerosols, but are dominated by the coarse-mode. Direct lidar inversions illustrate that the aerosol plume layers contributed up to 70% of the total AOD. NOAA-HYSPLIT back-trajectories and CALIPSO observations indicate the trans-Pacific transport of Asian-dust at 3 - 8 km altitude to the US East Coast. Meanwhile, the NOAA-HMS fire and smoke products illustrate the transport and possible mixture of dust with fine-mode smoke particles from the middle and southwestern US. The small Angstrom exponents of MODIS/Aqua in the US East Coast imply the dominance of coarse-mode particles. Accordingly, the upper layer of coarse mode aerosols is most likely transported from the East Asia, while the lower layer at 1-3 km altitude probably consists of continental dust particles from the western US mixed with fine-mode smoke particles. In addition, the transport and vertical structure of aerosol are investigated with the NAAPS global aerosol transport model.

Lidar is a valuable tool for atmospheric monitoring, allowing range-resolved profile measurements of a variety of quantities including aerosols, wind, pollutants and greenhouse gases. We report here the development of a versatile fielddeployable instrument for monitoring the lower troposphere. This region includes the effects of surface–atmosphere interactions and is an area where the resolution of satellite data is generally poor. Our instrument has been designed with the goal of making range-resolved measurements of greenhouse gases such as carbon dioxide, as well as probing the structure of the boundary layer. The key component is a tunable laser source based on an optical parametric oscillator covering the wavelength range 1.5–3.1 μm. This relatively eye-safe spectral region includes absorption lines of carbon dioxide and other greenhouse gases enabling the application of the differential absorption lidar (DIAL) technique, whilst also being suitable for aerosol lidar. We also report the use of an avalanche photodiode detector with high sensitivity and low noise. Field tests of the instrument were performed, recording continuous lidar signals over extended periods. The data were digitized at up to 8 signals per second. Scattering from aerosols and molecules was detected to a maximum range of 2 km, whilst scattering from cloud was recorded at up to 6 km. The data are plotted as time-versus-range images to show the dynamic state of the atmosphere evolving over time. These results demonstrate that the lidar achieves key requirements for both aerosol scatter and DIAL: tunability of the transmitter wavelength, sensitivity to molecular and aerosol scattering and robustness for field use.

Simultaneous multi-wave probing by using the differential absorption method could help to unveil fast chemical processes (for example - photo-stimulated) in atmosphere. The scheme of multi-wave finely tuned laser source, suitable for simultaneous probing a few atmosphere constituents and/or chemicals with the above mentioned method, is suggested and tested.

In this study, a mapping of the soot extinction coefficient in an oil refinery flare using a three-wavelength elastic backscatter lidar system is presented. A log-normal aerosol size distribution was assumed for the flare, and a homogenous refractive index was assumed along the nearly horizontal beam path through the atmosphere, excluding the flare volume. The optical depth was estimated for each wavelength and from this the Angstr¨om exponent was calculated. The results were comparable with the literature, demonstrating that it is possible to distinguish small from large particles by this technique in low wind conditions.

A DIAL instrument on a moving platform is seen as a valuable remote sensing component in a sensor network for area monitoring, targeting sites involved in unauthorised explosive manufacturing. Such instrument will perform the area mapping of the vapour concentration of key substances, known to be used as precursors in explosive fabrication, such as acetone and nitromethane. The IR spectra of acetone and nitromethane vapours have been defined from available spectroscopy databases and from laboratory measurements as showing optimal spectral band for the DIAL operation in the spectral range of 3.0 μm - 3.5 μm. The DIAL operation has been numerically simulated, with inputs based on the HITRAN database, the U.S. Standard Atmosphere and aerosol simulation software package OPAC. A combination of OPO and OPA has been chosen as a transmitter, where the idler wavelength is used for probing, with wavelength tuning in sequence. A scanner mounted on top of the coaxially aligned laser and receiver, is capable of covering almost 360 degrees horizontally and ±30 degrees vertically. The detection is performed by a photovoltaic photodiode with 4-stage cooling, with a signal digitalisation having 14 bit amplitude resolution and 125 Ms/s sampling rate. Here we present the development and the first test of the DIAL instrument.

The main objective of this work is to obtain methods that automatically allow qualitative detections of Atmospheric Boundary Layer heights from LIDAR data. Case studies will be used to describe the more relevant days of a campaign carried out in July of 2012 in Vitória, Espírito Santo, Brazil. The data analysis compares three mathematical algorithms that automatically provide the ABL height: Gradient Method (GM), using the derivative of the Range Corrected Signal (RCS) logarithm, WCT (Wavelet Covariance Transform), and Bulk Richardson's Number, which was used to validate the methods mentioned above. The comparison between the methods has shown that as the presence of clouds and the aerosol sublayer increased, the more sensitive was the refinement needed to choose the “right” parameters, whereas even Richardson’s method had ambiguities in finding a good estimate of the ABL top.

This article presents the results of a study related to variations in aerosol optical depth, total ozone content, water vapor content and angstrom coefficients from three experimental campaigns carried out in June 2010, June 2011and June 2012 at three sites in the city of Sofia (Institute of Electronics, Astronomical Observatory in the Borisova Gradina Park and National Institute of Geophysics, Geodesy and Geography (NIGGG)). A ceilometer CHM15k, two sun photometers Microtops II and an automatic meteorological station were used during the experiments.

The height of the mixing layer varied from 1500m to 2500 (3000)m during the measurements. The height of the residual layer ranged from 800m to 2000m. The stable boundary layer extended to 200-400m over the campaigns.

The aerosol optical depth (AOD) at wavelength λ = 500nm ranged from 0.38 to 0.66 in the first campaign and from 0.24 to 0.55 in the second one and from 0.11 to 0.23 in the third one. Corresponding ranges for the water vapor content (WVC) were 1.26cm to 2.6cm. Different types of aerosol optical depth and water vapor content behavior were observed. Additional resource of information about the origin of the aerosol layers detected by the ceilometer CHM15k offered the HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) model. The calculations of backward air mass trajectories give a plot of the road that the air mass traversed for a chosen time period before to arrive to the location of Sofia city.

The total ozone content (TOC) varied from 240 DU to 370 DU during the campaigns. The ground - based observation from ozonemeter Microtops II with satellite observation of Ozone Monitor Instruments (OMI) over Sofia (Bulgaria) are compared. Our results have implications for the further study of regional climate variability.

By now, the global impacts of atmospheric dust have been well-established. Nevertheless, relevant properties such as size distribution, depolarization ratio, and even single-scattering albedo have been shown to vary substantially between dust producing regions and are also strongly dependant on the conditions under which the dust is emitted. Even greater variations have been documented during the process of long-range transport. With continued improvement of detection technologies, research focus is increasingly turning to refinement of our knowledge of these properties of dust in order to better account for the presence of dust in models and data analysis. The purpose of this study is to use a combination of lidar data and models to directly observe the changing properties of dust layers as they are transported from their origin in the Taklamakan Desert of western China. With the co-operation of the Xinjiang Institute of Ecology and Geography, a portable micropulse lidar system was installed at Aksu National Field on the northern edge of the Tarim Basin in late April 2013, during the Spring dust storm season. Over six days, data were collected on the optical properties of dust emissions passing over this location. The measurements of this lidar have shown the dust over Aksu on these days to have a significantly higher depolarization ratio than has been previously reported for the region. Model results show this dust was then transported across the region at least as far as Korea and Japan. Models from the Naval Aerosol Analysis and Prediction System (NAAPS) show that during transport the dust layers became intermixed with sulfate emissions from industrial sources in China as well as smoke from wildfires burning in south-east Asia and Siberia. The multi-wavelength raman-elastic lidar located in Gwangju South Korea was used to observe the vertical structure of the layers as well as optical properties such as colour ratio, depolarization ratio and extinction coeffcient after regional-scale transportation and mixing with other aerosols. By comparing the observations of the Gwangju lidar with those taken near the source at Aksu, we investigate the extent of the change in optical properties of the dust layers over time. There is some evidence that the layers were also transported in some form to North America but these observations are preliminary and will require further investigation.

For the first time fresh biomass burning aerosol from wild fires in the north of Portugal was studied in detail by analysing profiles of optical and microphysical particle properties obtained from multiwavelength Raman lidar measurements. During the driest February since 1931, in 2012, an unusual high number of forest fires occurred in the north of the country. Despite the strong fires and back-trajectories directly crossing the burning areas, the optical and microphysical properties indicate a mixture of the biomass burning smoke with dust from the dried out soil of the Iberian peninsula or with other aerosol types. The layer means of the particle effective radius, the real part of the complex refractive index (CRI), and the imaginary part of the CRI ranged, respectively, from 0.20 μm to 0.30 μm, from 1.52 to 1.64, and from 0.009 to 0.017. The large single scattering albedo between 0.92 and 0.96, 0.92 and 0.96, and 0.88 and 0.94 at 355, 532 and 1064 nm, respectively, indicate weak absorption.