Refractive index determination for the nonstationary inhomogeneous ground-level layer of the atmosphere in precision lidar measurements

1982 ◽  
Vol 25 (4) ◽  
pp. 292-295
Author(s):  
A. M. Andrusenko ◽  
V. P. Danil'chenko ◽  
V. S. Kupko ◽  
E. Kh. Petrenko ◽  
A. V. Prokopov ◽  
...  
Keyword(s):  
Refractive Index ◽  
Ground Level ◽  
Lidar Measurements

scholarly journals Enhancement of stratospheric aerosols after solar proton event

1996 ◽  
Vol 14 (11) ◽  
pp. 1119-1123 ◽  
Author(s):  
O. I. Shumilov ◽  
E. A. Kasatkina ◽  
K. Henriksen ◽  
E. V. Vashenyuk
Keyword(s):  
Considerable Increase ◽  
Ground Level ◽  
Solar Proton ◽  
Stratospheric Aerosol ◽  
Nucleation Mechanism ◽  
Solar Proton Event ◽  
Proton Event ◽  
Aerosol Layer ◽  
Event Type ◽  
Lidar Measurements

Abstract. The lidar measurements at Verhnetulomski observatory (68.6°N, 31.8°E) at Kola peninsula detected a considerable increase of stratospheric aerosol concentration after the solar proton event of GLE (ground level event) type on the 16/02/84. This increase was located at precisely the same altitude range where the energetic solar protons lost their energy in the atmosphere. The aerosol layer formed precipitated quickly (1–2 km per day) during 18, 19, and 20 February 1984, and the increase of R(H) (backscattering ratio) at 17 km altitude reached 40% on 20/02/84. We present the model calculation of CN (condensation nuclei) altitude distribution on the basis of an ion-nucleation mechanism, taking into account the experimental energy distribution of incident solar protons. The meteorological situation during the event was also investigated.

scholarly journals Retrieval of aerosol microphysical properties from atmospheric lidar sounding: an investigation using synthetic measurements and data from the ACEPOL campaign

2021 ◽  
Vol 14 (6) ◽  
pp. 4755-4771
Author(s):  
William G. K. McLean ◽  
Guangliang Fu ◽  
Sharon P. Burton ◽  
Otto P. Hasekamp
Keyword(s):  
Refractive Index ◽  
Effective Radius ◽  
High Spectral Resolution ◽  
Imaginary Component ◽  
The Real ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Fine Mode ◽  
Truth Value ◽  
Real Refractive Index

Abstract. This study presents an investigation of aerosol microphysical retrievals from high spectral resolution lidar (HSRL) measurements. Firstly, retrievals are presented for synthetically generated lidar measurements, followed by an application of the retrieval algorithm to real lidar measurements. Here, we perform the investigation for an aerosol state vector that is typically used in multi-angle polarimeter (MAP) retrievals, so that the results can be interpreted in relation to a potential combination of lidar and MAP measurements. These state vectors correspond to a bimodal size distribution, where column number, effective radius, and effective variance of both modes are treated as fit parameters, alongside the complex refractive index and particle shape. The focus is primarily on a lidar configuration based on that of the High Spectral Resolution Lidar-2 (HSRL-2), which participated in the ACEPOL (Aerosol Characterization from Polarimeter and Lidar) campaign, a combined project between NASA and SRON (Netherlands Institute for Space Research). The measurement campaign took place between October and November 2017, over the western region of the USA. Six different instruments were mounted on the aeroplane: four MAPs and two lidar instruments, HSRL-2 and the Cloud Physics Lidar (CPL). Most of the flights were carried out over land, passing over scenes with a low aerosol load. One of the flights passed over a prescribed forest fire in Arizona on 9 November, with a relatively higher aerosol optical depth (AOD), and it is the data from this flight that are focussed on in this study. A retrieval of the aerosol microphysical properties of the smoke plume mixture was attempted with the data from HSRL-2 and compared with a retrieval from the MAPs carried out in previous work pertaining to the ACEPOL data. The synthetic HSRL-2 retrievals resulted for the fine mode in a mean absolute error (MAE) of 0.038 (0.025) µm for the effective radius (with a mean truth value of 0.195 µm), 0.052 (0.037) for the real refractive index, 0.010 (7.20×10-3) for the imaginary part of the refractive index, 0.109 (0.071) for the spherical fraction, and 0.054 (0.039) for the AOD at 532 nm, where the retrievals inside brackets indicate the MAE for noise-free retrievals. For the coarse mode, we find the MAE is 0.459 (0.254) µm for the effective radius (with a mean truth value of 1.970 µm), 0.085 (0.075) for the real refractive index, 2.06×10-4 (1.90×10-4) for the imaginary component, 0.120 (0.090) for the spherical fraction, and 0.051 (0.039) for the AOD. A study of the sensitivity of retrievals to the choice of prior and first guess showed that, on average, the retrieval errors increase when the prior deviates too much from the truth value. These experiments revealed that the measurements primarily contain information on the size and shape of the aerosol, along with the column number. Some information on the real component of the refractive index is also present, with the measurements providing little on absorption or on the effective variance of the aerosol distribution, as both of these were shown to depend heavily on the choice of prior. Retrievals using the HSRL-2 smoke-plume data yielded, for the fine mode, an effective radius of 0.107 µm, a real refractive index of 1.561, an imaginary component of refractive index of 0.010, a spherical fraction of 0.719, and an AOD at 532 nm of 0.505. Additionally, the single-scattering albedo (SSA) from the HSRL-2 retrievals was 0.940. Overall, these results are in good agreement with those from the Spectropolarimeter for Planetary Exploration (SPEX) and Research Scanning Polarimeter (RSP) retrievals.

scholarly journals Retrieval of the tropospheric aerosol microphysical characteristics from the data of multifrequency lidar sensing

2018 ◽  
Vol 176 ◽  
pp. 05055 ◽  
Author(s):  
S. Samoilova ◽  
M. Sviridenkov ◽  
I. Penner ◽  
G. Kokhanenko ◽  
Yu. Balin
Keyword(s):  
Refractive Index ◽  
Distribution Function ◽  
Complex Refractive Index ◽  
Size Distribution Function ◽  
Coarse Fraction ◽  
Optical Parameters ◽  
Raman Lidar ◽  
Tropospheric Aerosol ◽  
Lidar Measurements ◽  
The Vertical Distribution

Regular lidar measurements of the vertical distribution of aerosol optical parameters are carried out in Tomsk (56°N, 85°E) since April, 2011. We present the results of retrieval of microphysical characteristics from the data of measurements by means of Raman lidar in 2013. Section 2 is devoted to the theoretical aspects of retrieving the particle size distribution function U(r) (SDF) assuming a known complex refractive index m (CRI). It is shown that the coarse fraction cannot be retrieved unambiguously. When estimating U(r) and m together (section 3), the retrieved refractive index is non-linearly related to the optical coefficients and the distribution function, which leads to appearance of different, including false values of m. The corresponding U(r) differs only slightly, so the inaccuracy in m does not essentially affect the retrieval of the distribution function.

scholarly journals Retrieval of height-temporal distributions of particle parameters from multiwavelength lidar measurements using linear estimation technique and comparison results with AERONET

2013 ◽  
Vol 6 (2) ◽  
pp. 3059-3088 ◽  
Author(s):  
I. Veselovskii ◽  
D. N. Whiteman ◽  
M. Korenskiy ◽  
A. Kolgotin ◽  
O. Dubovik ◽  
...  
Keyword(s):  
Refractive Index ◽  
Effective Radius ◽  
Linear Estimation ◽  
Estimation Technique ◽  
Number Density ◽  
Volume Number ◽  
Lidar Measurements ◽  
Particle Parameters ◽  
Spatio Temporal ◽  
Multiwavelength Lidar

Abstract. The results of application of the linear estimation technique to multiwavelength Raman lidar measurements performed during the summer of 2011 in Greenbelt, MD, USA are presented. We demonstrate that multiwavelength lidars are capable not only of providing vertical profiles of particle properties but also of revealing the spatio-temporal evolution of aerosol features. The night-time 3β + 1α lidar measurements on 21 and 22 July were inverted to spatio-temporal distributions of particle microphysical parameters, such as volume, number density, effective radius and the complex refractive index. The particle volume and number density show strong variation during the night while the effective radius remains approximately constant. The real part of the refractive index demonstrates a slight decreasing tendency in a region of enhanced extinction coefficient. The linear estimation retrievals are stable and provide 2 min resolution time series of particle parameters at different heights. AERONET observations are compared with multiwavelength lidar retrievals showing good agreement.

scholarly journals Comparison of lidar-derived PM<sub>10</sub> with regional modeling and ground-based observations in the frame of MEGAPOLI experiment

2011 ◽  
Vol 11 (20) ◽  
pp. 10705-10726 ◽  
Author(s):  
P. Royer ◽  
P. Chazette ◽  
K. Sartelet ◽  
Q. J. Zhang ◽  
M. Beekmann ◽  
...  
Keyword(s):  
Mixed Boundary ◽  
Ground Level ◽  
In Situ Measurements ◽  
Percentage Error ◽  
Atmospheric Conditions ◽  
Transport Models ◽  
Near Surface ◽  
Lidar Measurements ◽  
Surface Measurements

Abstract. An innovative approach using mobile lidar measurements was implemented to test the performances of chemistry-transport models in simulating mass concentrations (PM10) predicted by chemistry-transport models. A ground-based mobile lidar (GBML) was deployed around Paris onboard a van during the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) summer experiment in July 2009. The measurements performed with this Rayleigh-Mie lidar are converted into PM10 profiles using optical-to-mass relationships previously established from in situ measurements performed around Paris for urban and peri-urban aerosols. The method is described here and applied to the 10 measurements days (MD). MD of 1, 15, 16 and 26 July 2009, corresponding to different levels of pollution and atmospheric conditions, are analyzed here in more details. Lidar-derived PM10 are compared with results of simulations from POLYPHEMUS and CHIMERE chemistry-transport models (CTM) and with ground-based observations from the AIRPARIF network. GBML-derived and AIRPARIF in situ measurements have been found to be in good agreement with a mean Root Mean Square Error RMSE (and a Mean Absolute Percentage Error MAPE) of 7.2 μg m−3 (26.0%) and 8.8 μg m−3 (25.2%) with relationships assuming peri-urban and urban-type particles, respectively. The comparisons between CTMs and lidar at ~200 m height have shown that CTMs tend to underestimate wet PM10 concentrations as revealed by the mean wet PM10 observed during the 10 MD of 22.4, 20.0 and 17.5 μg m−3 for lidar with peri-urban relationship, and POLYPHEMUS and CHIMERE models, respectively. This leads to a RMSE (and a MAPE) of 6.4 μg m−3 (29.6%) and 6.4 μg m−3 (27.6%) when considering POLYPHEMUS and CHIMERE CTMs, respectively. Wet integrated PM10 computed (between the ground and 1 km above the ground level) from lidar, POLYPHEMUS and CHIMERE results have been compared and have shown similar results with a RMSE (and MAPE) of 6.3 mg m−2 (30.1%) and 5.2 mg m−2 (22.3%) with POLYPHEMUS and CHIMERE when comparing with lidar-derived PM10 with periurban relationship. The values are of the same order of magnitude than other comparisons realized in previous studies. The discrepancies observed between models and measured PM10 can be explained by difficulties to accurately model the background conditions, the positions and strengths of the plume, the vertical turbulent diffusion (as well as the limited vertical model resolutions) and chemical processes as the formation of secondary aerosols. The major advantage of using vertically resolved lidar observations in addition to surface concentrations is to overcome the problem of limited spatial representativity of surface measurements. Even for the case of a well-mixed boundary layer, vertical mixing is not complete, especially in the surface layer and near source regions. Also a bad estimation of the mixing layer height would introduce errors in simulated surface concentrations, which can be detected using lidar measurements. In addition, horizontal spatial representativity is larger for altitude integrated measurements than for surface measurements, because horizontal inhomogeneities occurring near surface sources are dampened.

scholarly journals Performance Validation of a Multi-Channel LiDAR Sensor: Assessing the Effects of Target Height and Sensor Velocity on Measurement Error

2019 ◽  
Vol 62 (1) ◽  
pp. 231-244
Author(s):  
Saket S. Dasika ◽  
Michael P. Sama ◽  
L. Felipe Pampolini ◽  
Christopher B. Good
Keyword(s):  
Standard Deviation ◽  
Measurement Error ◽  
Ground Level ◽  
Average Error ◽  
Linear Motion ◽  
Target Height ◽  
Height Measurement ◽  
Above Ground Level ◽  
Motion System ◽  
Lidar Measurements

Abstract. The objective of this study was to determine the effects of sensor velocity and target height above ground level on height measurement error when using a multi-channel LiDAR sensor. A linear motion system was developed to precisely control the dynamics of the LiDAR sensor in an effort to remove uncertainty in the LiDAR position and velocity while under motion. The linear motion system allowed the LiDAR to translate forward and backward in one direction parallel to the ground. A user control interface was developed to operate the system under different velocity profiles and to log LiDAR data synchronous to the motion of the system. The performance of the linear motion system was validated with a tracking total station, and the results showed that the position and velocity control errors were negligible as compared to the LiDAR accuracy. The LiDAR was then validated using 25 test targets at varying heights above ground level (0.1, 0.3, 0.5, 0.6, and 0.8 m) with five different velocity profiles (0.1, 0.5, 1.0, 1.5, and 2.2 m s-1) and six replications to determine the effects of sensor velocity and target height on measurement error. The targets were painted white on one side and black on the other to determine the effect of relative intensity on LiDAR height measurement error. Generalized linear mixed models were fitted with the measurement error and the standard deviation of the measurement error as the responses. Sensor velocity, target height, and their interaction were considered as fixed effects to determine if there were significant differences in average error and standard deviation of error for different sensor velocities and target heights. The results indicated that the velocity of the LiDAR was a significant factor affecting the average error and standard deviation of error in height measurements. However, higher velocities tended to result in only slightly larger average errors. A three-fold increase in the standard deviation was observed when increasing the velocity from 0.1 to 2.2 m s-1. Height of the target was either a weakly significant or insignificant factor in average error and a weakly significant factor affecting the standard deviation of the LiDAR measurements, representing mixed results. The average error and standard deviation were less than 10 and 30 mm, respectively, for all replications. Relative intensities of the LiDAR measurements were 88.2% and 5.4% for white and black targets, respectively, and the different target colors exhibited a 4.7 mm shift in average estimated height error. These uncertainties may not be substantial for agricultural applications, where other sources of error, such as moving crop canopies or error in resolving the position of the sensor, are more likely to dominate overall measurement error. Keywords: LiDAR, Measurement error, Precision agriculture, Remote sensing, Validation.

scholarly journals Optical, microphysical, mass and geometrical properties of aged volcanic particles observed over Athens, Greece, during the Eyjafjallajökull eruption in April 2010 through synergy of Raman lidar and sunphotometer measurements

2013 ◽  
Vol 13 (18) ◽  
pp. 9303-9320 ◽  
Author(s):  
P. Kokkalis ◽  
A. Papayannis ◽  
V. Amiridis ◽  
R. E. Mamouri ◽  
I. Veselovskii ◽  
...  
Keyword(s):  
Refractive Index ◽  
Vertical Distribution ◽  
Mass Concentration ◽  
Effective Radius ◽  
Raman Lidar ◽  
Optical Extinction ◽  
Geometrical Properties ◽  
Lidar Measurements ◽  
Aerosol Types ◽  
532 Nm

Abstract. Vertical profiles of the optical (extinction and backscatter coefficients, lidar ratio and Ångström exponent), microphysical (mean effective radius, mean refractive index, mean number concentration) and geometrical properties as well as the mass concentration of volcanic particles from the Eyjafjallajökull eruption were retrieved at selected heights over Athens, Greece, using multi-wavelength Raman lidar measurements performed during the period 21–24 April 2010. Aerosol Robotic Network (AERONET) particulate columnar measurements along with inversion schemes were initialized together with lidar observations to deliver the aforementioned products. The well-known FLEXPART (FLEXible PARTicle dispersion model) model used for volcanic dispersion simulations is initiated as well in order to estimate the horizontal and vertical distribution of volcanic particles. Compared with the lidar measurements within the planetary boundary layer over Athens, FLEXPART proved to be a useful tool for determining the state of mixing of ash with other, locally emitted aerosol types. The major findings presented in our work concern the identification of volcanic particles layers in the form of filaments after 7-day transport from the volcanic source (approximately 4000 km away from our site) from the surface and up to 10 km according to the lidar measurements. Mean hourly averaged lidar signals indicated that the layer thickness of volcanic particles ranged between 1.5 and 2.2 km. The corresponding aerosol optical depth was found to vary from 0.01 to 0.18 at 355 nm and from 0.02 up to 0.17 at 532 nm. Furthermore, the corresponding lidar ratios (S) ranged between 60 and 80 sr at 355 nm and 44 and 88 sr at 532 nm. The mean effective radius of the volcanic particles estimated by applying inversion scheme to the lidar data found to vary within the range 0.13–0.38 μm and the refractive index ranged from 1.39+0.009i to 1.48+0.006i. This high variability is most probably attributed to the mixing of aged volcanic particles with other aerosol types of local origin. Finally, the LIRIC (LIdar/Radiometer Inversion Code) lidar/sunphotometric combined inversion algorithm has been applied in order to retrieve particle concentrations. These have been compared with FLEXPART simulations of the vertical distribution of ash showing good agreement concerning not only the geometrical properties of the volcanic particles layers but also the particles mass concentration.

scholarly journals Lidar-derived PM<sub>10</sub> and comparison with regional modeling in the frame of the MEGAPOLI Paris summer campaign

2011 ◽  
Vol 11 (4) ◽  
pp. 11861-11909 ◽  
Author(s):  
P. Royer ◽  
P. Chazette ◽  
K. S artelet ◽  
Q. J. Zhang ◽  
M. Beekmann ◽  
...  
Keyword(s):  
Ground Level ◽  
In Situ Measurements ◽  
Percentage Error ◽  
Atmospheric Conditions ◽  
Vertical Diffusion ◽  
Transport Models ◽  
Chemical Modeling ◽  
Lidar Measurements ◽  
Order Of Magnitude

Abstract. An original approach using mobile lidar measurements was implemented to validate mass concentrations (PM10) predicted by chemistry-transport models. A ground-based mobile lidar (GBML) was deployed around Paris onboard a van during the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) summer experiment in July 2009. The measurements performed with this Rayleigh-Mie lidar are converted into PM10 profiles using optical-to-mass relationships previously established from in situ measurements performed around Paris for urban and peri-urban aerosols. The method is described here and applied to the 10 measurements days (MD). MD of 1, 15, 16 and 26 July 2009 correspond to contrasted levels of pollution and atmospheric conditions. They are analyzed here in more details. Lidar-derived PM10 are compared with results of simulations from POLYPHEMUS and CHIMERE chemistry-transport models (CTM) and with ground-based observations from AIRPARIF network. GBML-derived and AIRPARIF in situ measurements have been found to be in good agreement with a mean Root Mean Square Error RMSE (and a Mean Absolute Percentage Error MAPE) of 5.9 μg m−3 (21.0%) with peri-urban and 8.7 μg m−3 (25.4%) with urban relationships, respectively. The comparisons between CTMs and lidar have shown that CTMs tend to underestimate wet PM10 concentrations as revealed by the mean wet PM10 observed during the 10 MD of 22.7, 20.0 and 17.5 μg m−3 for lidar with peri-urban relationship, POLYPHEMUS and CHIMERE models, respectively. This leads to a RMSE (and a MAPE) of 7.2 μg m−3 (33.4%) and 7.4 μg m−3 (32.0%) when considering POLYPHEMUS and CHIMERE CTMs, respectively. Wet integrated PM10 computed (between the ground and 1 km above the ground level) from lidar, POLYPHEMUS and CHIMERE results have been compared and have shown similar results with a RMSE (and MAPE) of 6.7 μg m−2 (30.7%) and 7.1 μg m−2 (28.4%) with POLYPHEMUS and CHIMERE when comparing with lidar-periu-urban parametrization. The values are of the same order of magnitude than other comparisons realized in previous studies. The discrepancies observed between models and measured PM10 can be explained by difficulties to accurately model the background conditions, the positions and strengths of the plume, the vertical diffusion (as well as the limited vertical model resolutions) and the chemical modeling such as the formation of secondary aerosols.

Sign in / Sign up

Export Citation Format

Share Document