scholarly journals Capabilities of an Automatic Lidar Ceilometer to Retrieve Aerosol Characteristics within the Planetary Boundary Layer

2021 ◽  
Vol 13 (18) ◽  
pp. 3626
Author(s):  
Dingdong Li ◽  
Yonghua Wu ◽  
Barry Gross ◽  
Fred Moshary
Keyword(s):  
Boundary Layer ◽  
New York ◽  
Planetary Boundary Layer ◽  
Relative Error ◽  
Satellite Observation ◽  
Calibration Error ◽  
Backscatter Coefficient ◽  
Ratio Error ◽  
Lidar Ratio ◽  
Aerosol Backscatter

Continuous observation and quantitative retrieval of aerosol backscatter coefficients are important in the study of air quality and climate in metropolitan areas such as New York City. Ceilometers are ideal for this application, but aerosol backscatter coefficient retrievals from ceilometers are challenging and require proper calibration. In this study, we calibrate the ceilometer (Lufft CHM15k, 1064 nm) system constant with the molecular backscatter coefficient and evaluate the calibrated profiles with other independent methods, including the water-phase cloud method and comparison with the NASA Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) attenuated backscatter coefficient profile. Multiple-day calibration results show a stable system constant with a relative uncertainty of about 7%. We also evaluate the overlap correction for the CHM15k ceilometer (provided by Lufft) with a Vaisala CL-31 ceilometer, and the results show good consistency between two ceilometers’ range-corrected signal (RCS) profiles above 200 m. Next, we implement a forward iterative method to retrieve aerosol backscatter coefficients from continuous ceilometer measurements. In the retrieval, the lidar ratio is constrained by the co-located NASA AERONET radiometer aerosol optical depth (AOD) retrieval and agrees with the AERONET lidar-ratio products, derived from aerosol microphysical parameters. The aerosol backscatter coefficient retrievals are validated with co-located elastic-Raman lidar retrievals and indicate a good correlation (R2≥0.95) in the planetary boundary layer (PBL). Furthermore, a case study shows that the ceilometer retrieved aerosol extinction coefficient profiles can be used to estimate the AOD of the PBL and the aloft plumes. Finally, simulations of the uncertainty of aerosol backscatter coefficient retrieval show that a calibration error of 10% results in 10–20% of relative error in the aerosol backscatter coefficient retrievals, while relative error caused by a lidar-ratio error of 10% is less than 4% in the PBL.

scholarly journals What is the benefit of ceilometers for aerosol remote sensing? An answer from EARLINET

2014 ◽  
Vol 7 (7) ◽  
pp. 1979-1997 ◽  
Author(s):  
M. Wiegner ◽  
F. Madonna ◽  
I. Binietoglou ◽  
R. Forkel ◽  
J. Gasteiger ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Case Studies ◽  
Special Focus ◽  
Backscatter Coefficient ◽  
Water Vapor Absorption ◽  
Long Term Stability ◽  
Vapor Absorption ◽  
Lidar Ratio ◽  
Favorable Conditions

Abstract. With the establishment of ceilometer networks by national weather services, a discussion commenced to which extent these simple backscatter lidars can be used for aerosol research. Though primarily designed for the detection of clouds it was shown that at least observations of the vertical structure of the boundary layer might be possible. However, an assessment of the potential of ceilometers for the quantitative retrieval of aerosol properties is still missing. In this paper we discuss different retrieval methods to derive the aerosol backscatter coefficient βp, with special focus on the calibration of the ceilometers. Different options based on forward and backward integration methods are compared with respect to their accuracy and applicability. It is shown that advanced lidar systems such as those being operated in the framework of the European Aerosol Research Lidar Network (EARLINET) are excellent tools for the calibration, and thus βp retrievals based on forward integration can readily be implemented and used for real-time applications. Furthermore, we discuss uncertainties introduced by incomplete overlap, the unknown lidar ratio, and water vapor absorption. The latter is relevant for the very large number of ceilometers operating in the spectral range around λ = 905–910 nm. The accuracy of the retrieved βp mainly depends on the accuracy of the calibration and the long-term stability of the ceilometer. Under favorable conditions, a relative error of βp on the order of 10% seems feasible. In the case of water vapor absorption, corrections assuming a realistic water vapor distribution and laser spectrum are indispensable; otherwise errors on the order of 20% could occur. From case studies it is shown that ceilometers can be used for the reliable detection of elevated aerosol layers below 5 km, and can contribute to the validation of chemistry transport models, e.g., the height of the boundary layer. However, the exploitation of ceilometer measurements is still in its infancy, so more studies are urgently needed to consolidate the present state of knowledge, which is based on a limited number of case studies.

scholarly journals Inter-comparison of lidar and ceilometer retrievals for aerosol and Planetary Boundary Layer profiling over Athens, Greece

2011 ◽  
Vol 4 (1) ◽  
pp. 73-99 ◽  
Author(s):  
G. Tsaknakis ◽  
A. Papayannis ◽  
P. Kokkalis ◽  
V. Amiridis ◽  
H. D. Kambezidis ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Layer Structure ◽  
Saharan Dust ◽  
Radiosonde Data ◽  
Backscatter Coefficient ◽  
Lidar System ◽  
Height Range ◽  
Tropospheric Aerosol ◽  
Filter Radiometer

Abstract. This study presents an inter-comparison of two active remote sensors (lidar and ceilometer) in determining the structure of the Planetary Boundary Layer (PBL) and in retrieving tropospheric aerosol vertical profiles over Athens, Greece. This inter-comparison was performed under various strongly different aerosol concentrations (urban air pollution, biomass burning and Saharan dust event), implementing two different lidar systems (one portable Raymetrics S.A. lidar system running at 355 nm and one multi-wavelength Raman lidar system running at 355 nm, 532 nm and 1064 nm) and one CL31 Vaisala S.A. ceilometer (running at 910 nm). To convert the ceilometer data to data having the same wavelengths as those from the lidar, the backscatter-related Ångström exponent was estimated using ultraviolet multi-filter radiometer (UV-MFR) data. The inter-comparison was based on two parameters: the mixing layer structure and height determined by the presence of the suspended aerosols and the aerosol backscatter coefficient. Additionally, radiosonde data were used to derive the PBL height. In general a good agreement is found between the ceilometer and the lidar techniques in both inter-compared parameters in the height range from 500 m to 5000 m, while the limitations of each instrument are also examined.

scholarly journals What is the benefit of ceilometers for aerosol remote sensing? An answer from EARLINET

2014 ◽  
Vol 7 (3) ◽  
pp. 2491-2543 ◽  
Author(s):  
M. Wiegner ◽  
F. Madonna ◽  
I. Binietoglou ◽  
R. Forkel ◽  
J. Gasteiger ◽  
...  
Keyword(s):  
Weather Prediction ◽  
Special Focus ◽  
Data Sets ◽  
Backscatter Coefficient ◽  
Water Vapor Absorption ◽  
International Projects ◽  
Lidar Ratio ◽  
Aerosol Remote Sensing ◽  
Real Time Information ◽  
Aerosol Backscatter

Abstract. With the establishment of ceilometer networks by national weather services a discussion commenced to which extent these simple backscatter lidars can be used for aerosol research. Though primarily designed for the detection of clouds it was shown that at least observations of the vertical structure of the boundary layer might be possible. However, an assessment of the potential of ceilometers for the quantitative retrieval of aerosol properties is still missing. In this paper we discuss different retrieval methods to derive the aerosol backscatter coefficient βp with special focus on the calibration of the ceilometers. Different options based on forward and backward integration methods are compared with respect to their accuracy and applicability. It is shown, that advanced lidar systems as being operated in the framework of EARLINET are excellent tools for the calibration, so that aerosol retrievals based on forward integration can readily be implemented. Furthermore, we discuss uncertainties introduced by incomplete overlap, the unknown lidar ratio, and water vapor absorption. The latter is relevant for the very large number of ceilometers operating in the spectral range around λ = 905 nm. Nevertheless, the retrieval of βp with an relative error in the order of 10% seems feasible, so ceilometer networks can provide useful information to fill the spatial gaps between sophisticated lidar systems. As a consequence several international projects are underway to harmonize data sets from different ceilometer and lidar networks for the sake of providing near real time information for weather prediction and air quality issues.

scholarly journals Variation of Ozone and PBL from the Lidar Observations and WRF-Chem Model in NYC Area During the 2018 Summer LISTOS Campaign

2020 ◽  
Vol 237 ◽  
pp. 08027
Author(s):  
Kaihui Zhao ◽  
Yonghua Wu ◽  
Jianping Huang ◽  
Rongsheng Jiang ◽  
Guillaume Gronoff ◽  
...  
Keyword(s):  
Boundary Layer ◽  
New York ◽  
Planetary Boundary Layer ◽  
Coastal Area ◽  
Model Performance ◽  
Early Morning ◽  
Planetary Boundary Layer Height ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Lidar Observations

High ozone (O3) episodes frequently occur in New York metropolitan and the downwind coastal area in summer. In this study, lidar/ceilometer are combined with WRF/Chem model to investigate an O3 event on Aug. 27~30 2018. We examine the spatial-temporal variabilities of O3 and planetary-boundary-layer height (PBLH) and assess the model performance on simulating surface O3 during this episode. By comparing with the lidar observations, the WRF/Chem is able to capture high O3 distribution in the PBL at noon and indicates consistent diurnal evolution for the ground O3. Nevertheless, in the early morning and night, the model overestimates the ground O3 and underestimates the PBLH.

scholarly journals Observations of Aerosol Spatial Distribution and Emissions in New York City Using a Scanning Micro Pulse Lidar

2020 ◽  
Vol 237 ◽  
pp. 03020
Author(s):  
Adrian Diaz Fortich ◽  
Victor Dominguez ◽  
Yonghua Wu ◽  
Barry Gross ◽  
Fred Moshary
Keyword(s):  
New York ◽  
New York City ◽  
Spatial Distribution ◽  
York City ◽  
Urban Areas ◽  
Backscatter Coefficient ◽  
Aerosol Dynamics ◽  
Particulate Pollution ◽  
Micro Pulse Lidar ◽  
Aerosol Backscatter

In order to better understand the behavior of particulate pollution and atmospheric dynamics in New York City, it is of great importance to analyze the spatial distribution of aerosols. A scanning lidar system allows for horizontal range-resolved observations of aerosol backscatter with high space and time resolution. A challenge to analyzing the lidar returns is to disentangle extinction over the range of the observations to retrieve the backscatter coefficient with distance. This work presents horizontal measurements taken with a scanning eye-safe Micro Pulse Lidar in New York City. The measurements are analyzed using the Slope Method to get an estimate of the range-resolved aerosol backscatter coefficient. The results are presented as backscatter coefficient maps that display the aerosol spatial distribution within the field of view of the scanning pattern deployed. These observations clearly resolve aerosol dynamics and emission sources within the urban areas.

scholarly journals Canadian Biomass Burning Aerosol Properties Modification during a Long-Ranged Event on August 2018

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5442
Author(s):  
Christina-Anna Papanikolaou ◽  
Elina Giannakaki ◽  
Alexandros Papayannis ◽  
Maria Mylonaki ◽  
Ourania Soupiona
Keyword(s):  
Biomass Burning ◽  
Remote Sensing Data ◽  
Satellite Observation ◽  
Depolarization Ratio ◽  
Marine Aerosols ◽  
Backscatter Coefficient ◽  
Biomass Burning Aerosol ◽  
The Mean ◽  
Spatio Temporal ◽  
Aerosol Backscatter

The aim of this paper is to study the spatio-temporal evolution of a long-lasting Canadian biomass burning event that affected Europe in August 2018. The event produced biomass burning aerosol layers which were observed during their transport from Canada to Europe from the 16 to the 26 August 2018 using active remote sensing data from the space-borne system Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The total number of aerosol layers detected was 745 of which 42% were identified as pure biomass burning. The remaining 58% were attributed to smoke mixed with: polluted dust (34%), clean continental (10%), polluted continental (5%), desert dust (6%) or marine aerosols (3%). In this study, smoke layers, pure and mixed ones, were observed by the CALIPSO satellite from 0.8 and up to 9.6 km height above mean sea level (amsl.). The mean altitude of these layers was found between 2.1 and 5.2 km amsl. The Ångström exponent, relevant to the aerosol backscatter coefficient (532/1064 nm), ranged between 0.9 and 1.5, indicating aerosols of different sizes. The mean linear particle depolarization ratio at 532 nm for pure biomass burning aerosols was found equal to 0.05 ± 0.04, indicating near spherical aerosols. We also observed that, in case of no aerosol mixing, the sphericity of pure smoke aerosols does not change during the air mass transportation (0.05–0.06). On the contrary, when the smoke is mixed with dessert dust the mean linear particle depolarization ratio may reach values up to 0.20 ± 0.04, especially close to the African continent (Region 4).

scholarly journals Retrieval of aerosol backscatter, extinction, and lidar ratio from Raman lidar with optimal estimation

2014 ◽  
Vol 7 (3) ◽  
pp. 757-776 ◽  
Author(s):  
A. C. Povey ◽  
R. G. Grainger ◽  
D. M. Peters ◽  
J. L. Agnew
Keyword(s):  
Boundary Layer ◽  
Prior Knowledge ◽  
Optimal Estimation ◽  
Real Data ◽  
Raman Lidar ◽  
Ash Layer ◽  
Lidar Ratio ◽  
Aerosol Backscatter ◽  
Lidar Observations

Abstract. Optimal estimation retrieval is a form of nonlinear regression which determines the most probable circumstances that produced a given observation, weighted against any prior knowledge of the system. This paper applies the technique to the estimation of aerosol backscatter and extinction (or lidar ratio) from two-channel Raman lidar observations. It produces results from simulated and real data consistent with existing Raman lidar analyses and additionally returns a more rigorous estimate of its uncertainties while automatically selecting an appropriate resolution without the imposition of artificial constraints. Backscatter is retrieved at the instrument's native resolution with an uncertainty between 2 and 20%. Extinction is less well constrained, retrieved at a resolution of 0.1–1 km depending on the quality of the data. The uncertainty in extinction is > 15%, in part due to the consideration of short 1 min integrations, but is comparable to fair estimates of the error when using the standard Raman lidar technique. The retrieval is then applied to several hours of observation on 19 April 2010 of ash from the Eyjafjallajökull eruption. A depolarising ash layer is found with a lidar ratio of 20–30 sr, much lower values than observed by previous studies. This potentially indicates a growth of the particles after 12–24 h within the planetary boundary layer. A lower concentration of ash within a residual layer exhibited a backscatter of 10 Mm−1 sr−1 and lidar ratio of 40 sr.

scholarly journals Seasonal variability of aerosol optical properties observed by means of a Raman lidar at an EARLINET site over Northeastern Spain

2011 ◽  
Vol 11 (1) ◽  
pp. 175-190 ◽  
Author(s):  
M. Sicard ◽  
F. Rocadenbosch ◽  
M. N. M. Reba ◽  
A. Comerón ◽  
S. Tomás ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Optical Properties ◽  
Planetary Boundary Layer ◽  
Optical Thickness ◽  
Seasonal Variability ◽  
Aerosol Optical Thickness ◽  
Saharan Dust ◽  
Raman Lidar ◽  
Aerosol Optical Properties ◽  
Lidar Ratio

Abstract. The annual and seasonal variability of aerosol optical properties observed by means of a Raman lidar over Northeastern Spain has been assessed. The lidar representativeness has first been checked against sun-photometer measurements in terms of aerosol optical thickness. Then the annual cycle and the seasonal variability of the planetary boundary layer aerosol optical thickness and its fraction compared to the columnar optical thickness, the lidar ratio, the backscatter-related Ångström exponent and the planetary boundary layer height are analyzed and discussed. Winter and summer mean profiles of extinction, backscatter and lidar ratio retrieved with the Raman algorithm are presented. The analysis shows the impact of most of the natural events (Saharan dust intrusions, wildfires, etc.) and meteorological situations (summer anticyclonic situation, the formation of the Iberian thermal low, winter long-range transport from North Europe and/or North America, re-circulation flows, etc.) occurring in the Barcelona area. A detailed study of a special event including a combined intrusion of Saharan dust and biomass-burning particles proves the suitability of combining the retrieval of aerosol optical properties from Raman and pure elastic lidar measurements to discriminate spatially different types of aerosols and to follow their spatial and temporal evolution.

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