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- Front Matter: Volume 7479
- Clouds and Aerosols
- CALIPSO--Space-based Observation
- DIAL and Raman Measurements
- Wind Observations
- Poster Session
Front Matter: Volume 7479
Front Matter: Volume 7479
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This PDF file contains the front matter associated with SPIE
Proceedings Volume 7479, including the Title Page, Copyright
information, Table of Contents, and the Conference Committee listing.
Clouds and Aerosols
Aerosol optical properties from multiwavelength lidar measurements in Romania
Show abstract
Vertically resolved profiles of optical properties of aerosols were measured using a multi-wavelength lidar system-RALI,
set up at the scientific research center in Magurele, Bucharest area (44.35 N latitude, 26.03 E longitude) during 2008.
The use of multiple laser wavelengths has enabled us to observe significant variations in backscatter profiles depending
on the particle origins. An air mass backward trajectory analysis, using Hysplit-4, was carried out to track the aerosol
plumes.
Aerosols can serve as valuable tracers of air motion in the planetary boundary layer (PBL). The height of layers in the
lower troposphere from lidar signal was calculated using the gradient method- minima of the first derivative. The
Richardson number method was used to estimate PBL height from the radio-soundings. We have used pressure,
temperature and dew point profiles as well as the wind direction profiles from NOAA (National Oceanic and
Atmospheric Administration) data base. The results were consistent with the ones obtained from LIDAR.
Aerosol investigation with multiwavelength lidar
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Results of measurements of atmospheric aerosol performed with multiwavelength lidar are presented. An approach to
retrieve profiles of aerosol particle size distribution was elaborated. It consists in direct fit of predefined distribution
(usually combination of lognormal functions with a few free parameters) to the experimental signals. The approach was
used for retrieving marine aerosol distributions. Studies of behavior of the particles at the cumulus cloud base were
performed as well. There the assumptions based on Twomey's model of the adiabatic parcel were used to support the
retrieving technique which was adopted to analyze lidar profiles (at 355, 532 and 1064 nm wavelengths) registered in the
region of the base of small warm cumulus clouds. Size distribution profiles and changes of particle effective radius
within the range of 0.5 - 3 μm were discussed.
EZ lidar dust transit phenomena observations in Seoul, Korea
Show abstract
Duststorms and sandstorms regularly devastate Northeast Asia and cause considerable damage to transportation system
and public health; further, these events are conceived to be one of the very important indices for estimating the global
warming and desertification. Previously, yellow sand events were considered natural phenomena that originate in deserts
and arid areas. However, the greater scale and frequency of these events in recent years are considered to be the result of
human activities such as overgrazing and over-cultivation. Japan, Korea, Cina and Mongolia are directly concerned to
prevent and control these storms and have been able to some extent to provide forecasts and early warnings. In this
framework, to improve the accuracy of forecasting , a compact and rugged eye safe lidar, the EZ LIDATM, developed
together by Laboratoire des Sciences du Climat et l'Environnement (LSCE) (CEA-CNRS) and LEOSPHERE (France) to
study and investigate structural and optical properties of clouds and aerosols, thanks to the strong know-how of CEA and
CNRS in the field of air quality measurements and cloud observation and analysis, was deployed in Seoul, Korea in
order to detect and study yellow sand events, thanks to its depolarization channel and scan capabilities. The preliminary
results, showed in this paper, of this measurement campaign put in evidence that EZ Lidar, for its capabilities of
operating unattended day and night under each atmospheric condition, is mature to be deployed in a global network to
study long-range transport, crucial in the forecasting model.
Initial approach in biomass burning aerosol transport tracking with CALIPSO and MODIS satellites, sunphotometer, and a backscatter lidar system in Brazil
Show abstract
Nowadays there is an increasing concern about the direct and indirect influence of the aerosols in the Earth's
radiative budget. Aerosols from biomass burning activities have been identified as a significant radiative forcing
agent. A significant concentration quantity of aerosol particles observed in the atmosphere can be associated
with intense anthropogenic biomass burning activity. The CALIPSO satellite and ground-based Lidar systems
are indispensable to provide the vertical structure and optical properties of aerosol and clouds on global and
local scale, respectively. The Brazilian mid-western region is one of the biggest producers of biomass burning in
the whole continent. Aerosols from biomass burning can be transported to distances of hundreds or thousands
of kilometers. It has been developed a computational routine to map the CALIPSO overpasses over the whole
country in order to retrieve the total coverage taking special attention in the Brazilian AERONET sites. In this
context, the measured data from AERONET, CALIPSO and MODIS Satellite and the MSP-Lidar system from
Instituto de Pesquisas Energéticas e Nucleares (IPEN) can be used to map the aerosols biomass burning plumes
transported from the mid-western to the southeastern region. In total 5 sites were chosen spanning from 0 to
23 South latitude and 46 to 60 West in longitude in coverage during 2007 and we were able to identify such
transports during the months of August and September.
Improvement of optical depth relations to PM2.5 concentrations using lidar derived PBL heights
Show abstract
To provide reasonable forcasts of near surface PM2.5
levels, it necessary that satellite measurments provide a
reasonable estimator of PM2.5 which can be coupled to
a transport model. Unfortunately this requires that the
aerosol be homogeneously mixed and that the extent of
the PBL be sufficiently accurate. For example, the
IDEA product (Infusing satellite Data into
Environmental Applications) used by the EPA relies on
a static relationship connecting PM2.5 to MODIS
aerosol optical depth (AOD) which relies on a static
model of the PBL aerosol height. In this paper, we show
that the PBL height is far from static and by taking the
variable PBL into account, a better prediction of PM2.5
from the MODIS (AOD) measurements is obtained. In
addition, seasonal variations in the microphysical
properties are also demonstrated and accounting for the
additional variability further improves the PM25/AOD
slope predictor.
Application of principal component analysis to lidar data filtering and analysis
Show abstract
Principal Component Analysis (PCA) has proven to be a valuable tool for remote sensing data compression, pattern
recognition, and for filtering out measurement noise. In this paper, we present preliminary results on the application of
PCA technique to reduce random noise present in lidar observations. Typically, the SNR at a given range can be
improved either by increasing the integration time of the measurements or by applying spatial averaging. This procedure,
however, improves the SNR at the expense of the instrument's temporal and spatial resolution. The number of range bins
needed to characterize backscatter features is far less than the number of components needed to characterize the
distribution of these features in the atmosphere. The higher-order PCA components, which mainly serve to characterize
noise, can be eliminated along with the noise that they characterize. The results of PCA noise filtering of lidar
observations strongly depend on the variability of aerosol plumes. To avoid loss of information in the presence of highly
variable aerosol plumes, it is necessary to use a conservative number of principal components higher then optimum for
maximum noise reduction. Nevertheless, noise reduction factors of 2-8, depending on the lidar range and atmospheric
variability, can still be achieved.
Retrieving atmospheric properties with an optimal estimation inverse method of lidar measurements
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This work suggests the use of a method to retrieve atmospheric information such as the aerosol backscatter and
extinction coefficients from a elastic backscatter LIDAR observations. This approach inverts the lidar equation via
an optimal estimation method. In order to get satisfactory inversion results, some boundary and measurements
conditions can be estimated concomitantly instead of being assumed a priori. This method based on a Bayesian
inference together with a Gaussian statistic creates an algorithm where the most probable or optimal solution
corresponds to maximize probability density function as a condition to the estimate of the lidar data profile.
This application to lidar data analysis presents advantages such as: 1) the possibility of incorporating multiple
heterogeneous sources, such as an additional wavelength for instance or aerosol optical thickness information from
AERONET (NASA Aerosol Robotic Network) as additional information; 2) the analyzed data can vary over the
irradiated region or time. For example, the atmosphere during the daytime presents different characteristics from
the nighttime. The algorithm can process different kinds and amounts of information; 3) the error estimation can
be retrieved separately by each uncertainty source (errors), such as the model assumptions and a priori errors
statements. Yet, it allows clearer and more confident measurements.
CALIPSO--Space-based Observation
Analysis of the EARLINET correlative measurements for CALIPSO
Show abstract
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.
Coordinated lidar observations of Saharan dust over Europe in the frame of EARLINET-AS0S project during CALIPSO overpasses: a strong dust case study analysis with modeling support
Show abstract
Coordinated lidar observations of Saharan dust over Europe are performed in the frame of the EARLINET-ASOS
(2006-2011) project, which comprises 25 stations: 16 Raman lidar stations, including 8 multi-wavelength
(3+2 station) Raman lidar stations, are used to retrieve the aerosol microphysical properties. Since
the launch of CALIOP, the two-wavelength lidar on board the CALIPSO satellite (June 2006) our lidar
network has been performing correlative aerosol measurements during CALIPSO overpasses over the
individual stations. In our presentation, we report on the correlative measurements obtained during Saharan
dust intrusions in the period from June 2006 to June 2008. We found that the number of dust events is
generally greatest in late spring, summer and early autumn periods, mainly in southern and south-eastern
Europe. A measurement example is presented that was analyzed to show the potential of a ground based lidar
network to follow a dust event over a specific study area, in correlation with the CALIOP measurements. The
dust transport over the studied area was simulated by the DREAM forecast model. Cross-section analyses of
CALIOP over the study area were used to assess the model performance for describing and forecasting the
vertical and horizontal distribution of the dust field over the Mediterranean. Our preliminary results can be
used to reveal the importance of the synergy between the CALIOP measurement and the dust model, assisted
by ground-based lidars, for clarifying the overall transport of dust over the European continent.
Three+two Raman lidar system configuration for space-borne active remote sensing system validation over Athens, Greece, in the frame of the EARLINET-ASOS and ESA-CALIPSO projects
Show abstract
Routine lidar measurements of the aerosol vertical distribution have been performed over Athens, Greece using a multi-wavelength
(355-387-407-532-607-1064 nm) Raman lidar system, since 2006 in the frame of the EARLINET-ASOS
(2006-2011) project. Additionally, since June 2006, correlative measurements for CALIOP space-borne lidar are
performed. The aim of these measurements is to provide validation profiles for the CALIOP instrument in the lower and
middle troposphere (0.5-8 km) in terms of the aerosol backscatter coefficients at 532 nm and 1064 nm, the color ratio
(532/1064 nm) and the depolarization ratio at 532 nm, but mainly to provide information about the aerosol extinction
profiles and the corresponding lidar ratios at 532 nm. From the available correlative CALIOP level-2 and multi-wavelength
Raman lidar aerosol data over Athens, we selected to present cases that have been identified as Saharan dust
outbreaks and large biomass burning events, using air mass backward trajectories in order to characterize the source of
the aerosols. We found that the vertical profiles of the aerosol optical properties between CALIOP and NTUA lidars
were not always in a good agreement during the exact time of the satellite overpass, especially for daytime
measurements, when the distance between the two instruments was greater than 40 km. An improvement was noticed
when ground-based lidar measurements where performed previously or later than the CALIPSO overpass time. For the
nighttime intercomparison the agreement between the two instruments was better during the CALIPSO overpass time.
This was attributed mainly to the closer nighttime satellite track over the Athens lidar station.
DIAL and Raman Measurements
Performance modeling for A-SCOPE: a space-borne lidar measuring atmospheric CO2
Show abstract
A-SCOPE (Advanced Space Carbon and Climate Observation of Planet Earth) has been one of the six candidates for the
third cycle of the Earth Explorer Core missions, selected by the European Space Agency (ESA) for assessment studies.
Earth Explorer missions focus on the science and research aspects of ESA's Living Planet Programme. A-SCOPE
mission aims at observing atmospheric CO2 for a better understanding of the carbon cycle. Knowledge about the spatial
distribution of sources and sinks of CO2 with unprecedented accuracy will provide urgently needed information about the global carbon cycle. A-SCOPE mission encompasses a new approach to observe the Earth from space based on an IPDA
(Integrated Path Differential Absorption) Lidar. Based on the known principle of a differential measurement technique,
the IPDA lidar relies on the measurement of the laser echoes reflected by hard targets as the ground or the top of the
vegetation. Such a time-gated technique is a promising way to overcome the sources of systematic errors inherent to
passive missions. To be fully exploited, it however translates into stringent instrument requirements and requires a
dedicated performance assessment. In this paper, the A-SCOPE instrument concept is first presented, with the aim of
summarizing some important outcomes from the industrial assessment studies. After a discussion of the mission requirements and measurement principles, an overview is given about the instrument architecture. Then the instrument performance is reported, together with a detailed discussion about sources of systematic errors, which pose the strongest technical challenges.
Preliminary tropospheric ozone DIAL, water vapour, and aerosol lidar measurements during ARC-IONS
Show abstract
A new lidar instrument, dubbed AeRO (Aerosol Raman Ozone) Lidar, is being developed at Environment Canada's
Centre For Atmospheric Research Experiments (CARE). The new system will use three lasers to simultaneously
measure ozone, water vapour and aerosol profiles (including extinction) from near ground to the tropopause. The main
thrust will focus on understanding Air Quality within the airshed with the capability of looking at Stratospheric
Tropospheric Exchange (STE) processes to determine the magnitude and frequency of such events leading to elevated
levels of tropospheric ozone. In addition a wind profiler through a partnership with University of Western Ontario will
soon be deployed to CARE to provide complementary observations of the tropopause. The lidar participated in the
ARC-IONS field campaign during April and July of 2008. During the field campaign, daily ozonesondes were released
to further compliment the lidar measurements. Details of the system design and preliminary results from the lidar
measurements will be presented.
A novel 2 µm, frequency conversion based, laser transmitter for CO2 DIAL
Show abstract
We report on a novel 2 μm laser transmitter for CO2 DIAL, based on a nanosecond parametric master oscillator-power
amplifier architecture. The master oscillator is an entangled-cavity, doubly resonant, optical parametric oscillator, based
on a type-II periodically poled Lithium Niobate nonlinear crystal. This device provides single-longitudinal-mode
radiation, with a high frequency stability and high beam quality, with no need of an additional seeding source. The 2.05
μm signal emission is amplified by multi-stage parametric amplifiers to generate more than 10 mJ. After amplification,
both the spectral purity and beam quality are maintained: we demonstrate single-longitudinal-mode emission with a
frequency stability better than 3 MHz rms, within a nearly diffraction limited beam, with a M2 quality factor close to 1.5.
The unique performances of this parametric architecture make this device a relevant transmitter for CO2 differential-absorption
LIDAR. Such approach could be readily duplicated for the detection of other greenhouse gases.
Raman water vapour concentration measurements for reduction of false alarms in forest fire detection
Show abstract
Forest fires can be the cause of environmental catastrophe, with the natural outcomes of serious ecological and
economic damages, together with the possibility to endanger human safety. At the aim to reduce this catastrophe
several author have been shown that the Laser light scattering can be uses to reveals the particulate emitted in the
smoke. Infact experimental and theoretical investigations have shown that lidar is a powerful tool to detect the tenuous
smoke plumes produced by forest fires at an early stage. In early 90's Arbolino and Andreucci have shown the
theoretical possibility to detect the particulate emitted in atmosphere from smoke forest fire. Vilar at all have shown
experimentally the possibility to measure the density variation in atmosphere due to plume emitted in forest fire event.
Gaudio at all. have already shown that it is possible to evaluate water vapor emitted in smoke of vegetable fuel using a
CO2 dial system.
In this paper a theoretical model to evaluate the capabilities of a lidar system in fire surveillance of wooded areas will
be presented. In particular we intend propose a technique to minimizing the false alarm in the detection of forest fire by
lidar based on a measurement of second components emitted in a combustion process. Usually to detect a fire alarm a
rapid increase of aerosol amount is measured. If the backscattering signal report a peak, the presences of a forest fire
will be probable. Our idea to confirm this hypothesis is measure the second components emitted in a forest fire at the
aim to minimize the false alarm. The simulated measurements of the humidity amount within the smoke plume will be
carried out by means of Raman analysis. Fixing the burning rate of the vegetable-fuels, the maximum range of
detection will be evaluated.
Raman water vapor lidar calibration
Show abstract
We show here new results of a Raman LIDAR calibration methodology effort putting emphasis in the assessment
of the cross-section ratio between water vapor and nitrogen by the use of a calibrated NIST traceable tungsten
lamp. Therein we give a step by step procedure of how to employ such equipment by means of a mapping/scanning
procedure over the receiving optics of a water vapor Raman LIDAR. This methodology has been independently
used at Howard University Raman LIDAR and at IPEN Raman LIDAR what strongly supports its reproducibility
and points towards an independently calibration methodology to be carried on within an experiment routine.
Wind Observations
VisibleWind: wind profile measurements at low altitude
Show abstract
VisibleWindTM is developing an inexpensive rapid response system, for accurately characterizing wind shear and
small scale wind phenomena in the boundary layer and for prospecting suitable locations for wind power turbines.
The ValidWind system can also collect reliable "ground truth" for other remote wind sensors. The system employs
small (0.25 m dia.) lightweight balloons and a tracker consisting of an Impulse 200 XL laser rangefinder coupled to
a PC for automated data recording. Experiments on balloon trajectories demonstrate that the laser detection of range
(± 0.5 m), together with measured azimuth and altitude, is an inexpensive, convenient, and capable alternative to
other wind tracking methods. The maximum detection range has been increased to 2200 meters using micro-corner-cube
retroreflector tape on balloons. Low power LEDs enable nighttime tracking. To avoid large balloon gyrations
about the mean trajectory, we use balloons having low ascent rates and subcritical Reynolds numbers. Trajectory
points are typically recorded every 4 - 7 seconds. Atmospheric features observed under conditions of inversions or
"light and variable winds" include abrupt onsets of shear at altitudes of 100-250 m, velocity changes of order 1-3
m/s within layers of 10-20 m thickness, and veering of the wind direction by 180 degrees or more as altitude
increases from 300 to 500 m. We have previously reported comparisons of balloon-based wind profiles with the
output of a co-located sodar. Even with the Impulse rangefinder, our system still requires a "man in the loop" to
track the balloon. A future system enhancement will automate balloon tracking, so that laser returns are obtained
automatically at 1 Hz. While balloon measurements of large-scale, high altitude wind profiles are well known, this
novel measurement system provides high-resolution, real-time characterization of the fluctuating local wind fields at
the bottom of the boundary layer where wind power turbines and other remote wind sensors must operate.
Development of the one-sided nonlinear adaptive Doppler shift estimation techniques
Show abstract
The new development of a one-sided nonlinear adaptive shift estimation technique (NADSET) is introduced. The
background of the algorithm and a brief overview of NADSET are presented. The new technique is applied to the wind
parameter estimates from a 2-μm wavelength coherent Doppler lidar system called VALIDAR located in NASA Langley
Research Center in Virginia. The new technique enhances wind parameters such as Doppler shift and power estimates in
low Signal-To-Noise-Ratio (SNR) regimes using the estimates in high SNR regimes as the algorithm scans the range
bins from low to high altitude. The original NADSET utilizes the statistics in both the lower and the higher range bins to
refine the wind parameter estimates in between. The results of the two different approaches of NADSET are compared.
Development of a compact laser for ChemCam instrument and potential use for wind measurement on Mars
Show abstract
A new conduction cooled compact laser for Laser Induced Breakdown Spectroscopy (LIBS) on Mars is presented. The
laser provides pulses with energy higher than 30mJ at 1μm of wavelength with a good spatial quality (M2 between 1 and
3 according to the temperature). The performance of the laser is within the specifications on a large temperature range
(-20°C/+20°C). This laser will be mounted on the ChemCam Instrument of the NASA mission MSL 2009 (finally
reported to 2011). The goal of this instrument is to study the chemical composition of Martian rocks. A laser source
(subject of this presentation) emits a pulse. It creates a luminous plasma on the rock, which is then analyzed by three
spectrometers. The laser source was developed by the French company Thales Laser, under funding and with technical
support from CNES. The laser is compact and does not require any active cooling. More recently, the laser was studied
by the LATMOS (Laboratoire Atmosphères, Milieux, Observations Spatiales, former Service d'Aéronomie). The goal of
this study was to make spectral measurements on the laser to evaluate its capacity to be used as a luminous source for
Lidar applications, and in particular for a Doppler Lidar measuring the wind speed. As the laser is very well adapted to
the harsh Martian environments, one of the possible applications would be wind speed measurements on Mars. The first
results obtained by the LATMOS are good and do not show any impossibilities for this target application.
Validation of the new long range 1.5µm wind lidar WLS70 for atmospheric dynamics studies
Show abstract
To fully understand atmospheric dynamics, climate studies, energy transfer, and weather prediction the wind field is one
of the most important atmospheric state variables. Studies indicate that a global determination of the tropospheric wind
field to an accuracy of 0.5 m/s is critical for improved numerical weather forecasting. LEOSPHERE recently developed
a new generation long range compact, eye safe and transportable wind Lidar, named WLS70, capable to fully determine
locally the wind field in real time in the planetary boundary layer (PBL). First results of the measurement campaign put
in evidence both wind velocity vertical profiles and atmosphere structure derived from Lidar data.
Poster Session
Tunable injection-seeded Nd:GSAG laser at 943nm for water vapor detection
Show abstract
Long range water vapor DIAL-systems require efficient and rugged laser sources. The quasi-three-level transition
from R1 to Z5 in Nd:GSAG with 943nm wavelength is a promising candidate. An actively Q-switched Nd:GSAG
laser was established. Up to 31mJ output pulse energy and up to 26Hz repetition rate was achieved. Injection
seeding was used to obtain single frequency operation. The seed laser is a distributed feedback laser diode. Laser
frequency was stabilized by ramp-hold-fire method. By tuning the wavelength of the seed laser a 0.83nm tuning
range of the pulsed Nd:GSAG laser was obtained. Measured by Fabry-Perot interferometer the spectral line width
was approximately 50MHz.
Solid-state Raman frequency converters for CO2-DIAL systems at 1.6 µm
Show abstract
Measurement of the three-dimensional distribution of atmospheric trace gases, especially CO2, is an important factor to
improve the accuracy of climate models and to understand the global effects of the greenhouse effect. This can be
achieved by differential absorption Lidar (DIAL).
The absorption spectrum of CO2 features several suitable absorption lines for a ground-based or air-borne DIAL system
working at wavelengths between 1.57 μm and 1.61 μm. An appropriate laser transmitter must emit laser pulses with
pulse energies of more than 10 mJ and pulse duration in the nanosecond range. For high spectral purity the bandwidth is
required to be less than 60 MHz.
OPOs and Er-doped solid-state lasers emit around 1.6 μm, but we describe here alternatively Nd:YAG and Nd:glass laser
systems with Raman converters. The use of stimulated Raman scattering in crystalline and ceramic materials is a
possibility to shift the wavelength of existing lasers depending on the size of the Raman shift. After the investigation of a
large number of Raman-active materials some of them could be identified as promising candidates for the conversion of
typical Nd:YAG emission wavelengths, including LiNH2C6H4SO3•H2O, Ba(NO3)2, Li2SO4•H2O, Y(HCOO)3•2H2O, β-BBO and diamond. Our experiments with Ba(NO3)2 showed that the choice of the material should not be restricted to
those with an adequate first order Stokes Raman line position, but also second or third order Raman shift should be
considered.
Development of Raman frequency converters for high pulse energies concentrates on linear and folded resonator designs
and seeded Raman amplifiers using the Raman material as a direct amplifier. With Ba(NO3)2 pulse energy up to 116 mJ
and 42 % quantum efficiency at the third Stokes wavelength with 1599 nm has been demonstrated. High power operation
at 5 W with compensation of thermal lensing was achieved.
Aerosol plume observations by the ground-based lidar, sunphotometer, and satellite: cases analysis
Show abstract
Smoke and dust aerosol plumes are observed by the ground-based multi-wavelength elastic-Raman lidar, sunphotometer
and space-borne lidar CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization). Lidar-derived multi-wavelength
aerosol extinction profiles and column lidar ratios are constrained by the independently measured optical
depths. The aloft smoke plume layers from Idaho/Montana forest fires were measured at 2~8 km altitude by the ground
lidar on Aug. 14~15, 2007. High aerosol optical depths (AOD) are shown with the value of 0.6~0.8 at wavelength 500
nm and Angstrom exponent of 1.8. The CALIOP observations generally show consistent plume height distribution with
the ground lidar, but partly misclassify these smoke plumes as clouds. The forest fire sources and intra-continental
smoke transport are clearly illustrated by CALIOP and MODIS satellite imageries. For the moderate dust-like plumes on
April 18, 2008, they were observed at the altitude of 2~6 km. Aerosol optical depths vary from 0.2 to 0.4 at wavelength
500 nm with Angstrom exponent <1.0 in the plume-layer. Ground-lidar and CALIOP retrievals show the good
agreement in dust-like layer heights, extinction profiles and aerosol species classification.
Comparison of lidar calibration at 1064-nm channel using the water-phase and cirrus clouds
Show abstract
Lidar calibration at the 1064-nm channel is explored by using the low-level water-phase cloud and high cirrus cloud.
Based on a known constant of lidar ratio in the optically thick water cloud, the lidar calibration constant is estimated by
integrating lidar returns in the cloud. By using wavelength independence of cirrus cloud backscatter, the lidar constant is
analyzed with the two-wavelength signals ratio at 532-nm and 1064-nm after correcting aerosol transmittance from
sunphotometer measurement. Calibration constants by these two separate methods are compared on the same day and
show consistency with the relative difference of less than 30% in general. We further verify the calibration constant by
regressing lidar signals with calibrated ceilometer data in the low planetary boundary layer (PBL). Moreover, the
calibration result is tested by applying it to estimate aerosol backscatter at 1064-nm and Angstrom exponent. In the end,
normalized daily averages of lidar constants over two-month period are presented.