scholarly journals Validation of aerosol backscatter profiles from Raman lidar and ceilometer using balloon-borne measurements

2021 ◽  
Vol 21 (3) ◽  
pp. 2267-2285
Author(s):  
Simone Brunamonti ◽  
Giovanni Martucci ◽  
Gonzague Romanens ◽  
Yann Poltera ◽  
Frank G. Wienhold ◽  
...  
Keyword(s):  
Remote Sensing ◽  
In Situ Measurements ◽  
Aerosol Size Distribution ◽  
Spatial And Temporal Variability ◽  
Raman Lidar ◽  
Backscatter Coefficient ◽  
Custom Made ◽  
Aerosol Backscatter ◽  
Good Agreement

Abstract. Remote-sensing measurements by light detection and ranging (lidar) instruments are fundamental for the monitoring of altitude-resolved aerosol optical properties. Here we validate vertical profiles of aerosol backscatter coefficient (βaer) measured by two independent lidar systems using co-located balloon-borne measurements performed by Compact Optical Backscatter Aerosol Detector (COBALD) sondes. COBALD provides high-precision in situ measurements of βaer at two wavelengths (455 and 940 nm). The two analyzed lidar systems are the research Raman Lidar for Meteorological Observations (RALMO) and the commercial CHM15K ceilometer (Lufft, Germany). We consider in total 17 RALMO and 31 CHM15K profiles, co-located with simultaneous COBALD soundings performed throughout the years 2014–2019 at the MeteoSwiss observatory of Payerne (Switzerland). The RALMO (355 nm) and CHM15K (1064 nm) measurements are converted to 455 and 940 nm, respectively, using the Ångström exponent profiles retrieved from COBALD data. To account for the different receiver field-of-view (FOV) angles between the two lidars (0.01–0.02∘) and COBALD (6∘), we derive a custom-made correction using Mie-theory scattering simulations. Our analysis shows that both lidar instruments achieve on average a good agreement with COBALD measurements in the boundary layer and free troposphere, up to 6 km altitude. For medium-high-aerosol-content measurements at altitudes below 3 km, the mean ± standard deviation difference in βaer calculated from all considered soundings is −2 % ± 37 % (−0.018 ± 0.237 Mm−1 sr−1 at 455 nm) for RALMO−COBALD and +5 % ± 43 % (+0.009 ± 0.185 Mm−1 sr−1 at 940 mm) for CHM15K−COBALD. Above 3 km altitude, absolute deviations generally decrease, while relative deviations increase due to the prevalence of air masses with low aerosol content. Uncertainties related to the FOV correction and spatial- and temporal-variability effects (associated with the balloon's drift with altitude and different integration times) contribute to the large standard deviations observed at low altitudes. The lack of information on the aerosol size distribution and the high atmospheric variability prevent an accurate quantification of these effects. Nevertheless, the excellent agreement observed in individual profiles, including fine and complex structures in the βaer vertical distribution, shows that under optimal conditions, the discrepancies with the in situ measurements are typically comparable to the estimated statistical uncertainties in the remote-sensing measurements. Therefore, we conclude that βaer profiles measured by the RALMO and CHM15K lidar systems are in good agreement with in situ measurements by COBALD sondes up to 6 km altitude.

scholarly journals Validation of aerosol backscatter profiles from Raman lidar and ceilometer using balloon-borne measurements

2020 ◽  
Author(s):  
Simone Brunamonti ◽  
Giovanni Martucci ◽  
Gonzague Romanens ◽  
Yann Poltera ◽  
Frank G. Wienhold ◽  
...  
Keyword(s):  
In Situ Measurements ◽  
Spatial And Temporal Variability ◽  
Free Troposphere ◽  
Raman Lidar ◽  
Backscatter Coefficient ◽  
Custom Made ◽  
Standard Deviations ◽  
Aerosol Backscatter ◽  
Good Agreement

Abstract. Remote sensing measurements by light detection and ranging (lidar) instruments are fundamental for the monitoring of altitude-resolved aerosol optical properties. Here, we validate vertical profiles of aerosol backscatter coefficient (βaer) measured by two independent lidar systems using co-located balloon-borne measurements performed by Compact Optical Backscatter Aerosol Detector (COBALD) sondes. COBALD provides high-precision in-situ measurements of βaer at two wavelengths (455 and 940 nm). The two analyzed lidar systems are the research Raman Lidar for Meteorological Observations (RALMO) and the commercial CHM15K ceilometer (Lufft, Germany). We consider in total 17 RALMO and 31 CHM15K profiles, co-located with simultaneous COBALD soundings performed throughout the years 2014–2019 at the MeteoSwiss observatory of Payerne (Switzerland). The RALMO (355 nm) and CHM15K (1064 nm) measurements are converted to respectively 455 nm and 940 nm using the Angstrom exponent profiles retrieved from COBALD data. To account for the different receiver field of view (FOV) angles between the two lidars (0.01–0.02°) and COBALD (6°), we derive a custom-made correction using Mie-theory scattering simulations. Our analysis shows that both RALMO and CHM15K achieve a good agreement with COBALD measurements in the boundary layer and free troposphere, up to 6 km altitude, and including fine structures in the aerosol’s vertical distribution. For altitudes below 2 km, the mean ± standard deviation difference in βaer is + 6 % ± 40 % (+ 0.005 ± 0.319 Mm−1 sr−1) for RALMO – COBALD at 455 nm, and + 13 % ± 51 % (+ 0.038 ± 0.207 Mm−1 sr−1) for CHM15K – COBALD at 940 nm. The large standard deviations can be at least partly attributed to atmospheric variability effects, associated with the balloon’s horizontal drift with altitude (away from the lidar beam) and the different integration times of the two techniques. Combined with the high spatial and temporal variability of atmospheric aerosols, these effects often lead to a slight altitude displacement between aerosol backscatter features that are seen by both techniques. For altitudes between 2–6 km, the absolute standard deviations of both RALMO and CHM15K decrease (below 0.13 and 0.16 Mm−1sr−1, respectively), while their corresponding relative deviations increase (often exceeding 100 % COBALD of the signal). This is due to the low aerosol content (i.e. low absolute backscattered signal) in the free troposphere, and the vertically decreasing signal-to-noise ratio of the lidar measurements (especially CHM15K). Overall, we conclude that the βaer profiles measured by the RALMO and CHM15K lidar systems are in good agreement with in-situ measurements by COBALD sondes up to 6 km altitude.

scholarly journals Spatial variation of aerosol optical properties around the high-alpine site Jungfraujoch (3580 m a.s.l.)

2012 ◽  
Vol 12 (15) ◽  
pp. 7231-7249 ◽  
Author(s):  
P. Zieger ◽  
E. Kienast-Sjögren ◽  
M. Starace ◽  
J. von Bismarck ◽  
N. Bukowiecki ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Optical Properties ◽  
Light Scattering ◽  
In Situ Measurements ◽  
Swiss Alps ◽  
Aerosol Size Distribution ◽  
Horizontal Distance ◽  
Aerosol Optical Properties ◽  
Orographic Clouds

Abstract. This paper presents results of the extensive field campaign CLACE 2010 (Cloud and Aerosol Characterization Experiment) performed in summer 2010 at the Jungfraujoch (JFJ) and the Kleine Scheidegg (KLS) in the Swiss Alps. The main goal of this campaign was to investigate the vertical variability of aerosol optical properties around the JFJ and to show the consistency of the different employed measurement techniques considering explicitly the effects of relative humidity (RH) on the aerosol light scattering. Various aerosol optical and microphysical parameters were recorded using in-situ and remote sensing techniques. In-situ measurements of aerosol size distribution, light scattering, light absorption and scattering enhancement due to water uptake were performed at the JFJ at 3580 m a.s.l.. A unique set-up allowed remote sensing measurements of aerosol columnar and vertical properties from the KLS located about 1500 m below and within the line of sight to the JFJ (horizontal distance of approx. 4.5 km). In addition, two satellite retrievals from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) and the Moderate Resolution Imaging Spectroradiometer (MODIS) as well as back trajectory analyses were added to the comparison to account for a wider geographical context. All in-situ and remote sensing measurements were in clear correspondence. The ambient extinction coefficient measured in situ at the JFJ agreed well with the KLS-based LIDAR (Light Detection and Ranging) retrieval at the altitude-level of the JFJ under plausible assumptions on the LIDAR ratio. However, we can show that the quality of this comparison is affected by orographic effects due to the exposed location of the JFJ on a saddle between two mountains and next to a large glacier. The local RH around the JFJ was often higher than in the optical path of the LIDAR measurement, especially when the wind originated from the south via the glacier, leading to orographic clouds which remained lower than the LIDAR beam. Furthermore, the dominance of long-range transported Saharan dust was observed in all measurements for several days, however only for a shorter time period in the in-situ measurements due to the vertical structure of the dust plume. The optical properties of the aerosol column retrieved from SEVIRI and MODIS showed the same magnitude and a similar temporal evolution as the measurements at the KLS and the JFJ. Remaining differences are attributed to the complex terrain and simplifications in the aerosol retrieval scheme in general.

scholarly journals Spatial variation of aerosol optical properties around the high-alpine site Jungfraujoch (3580 m a.s.l.)

2012 ◽  
Vol 12 (5) ◽  
pp. 11105-11150
Author(s):  
P. Zieger ◽  
E. Kienast-Sjögren ◽  
M. Starace ◽  
J. von Bismarck ◽  
N. Bukowiecki ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Optical Properties ◽  
Light Scattering ◽  
In Situ Measurements ◽  
Swiss Alps ◽  
Aerosol Size Distribution ◽  
Horizontal Distance ◽  
Aerosol Optical Properties ◽  
Orographic Clouds

Abstract. This paper presents results of the extensive field campaign CLACE 2010 (Cloud and Aerosol Characterization Experiment) performed in summer 2010 at the Jungfraujoch (JFJ) and the Kleine Scheidegg (KLS) in the Swiss Alps. The main goal of this campaign was to investigate the vertical variability of aerosol optical properties around the JFJ and to show the consistency of the different employed measurement techniques considering explicitly the effects of relative humidity (RH) on the aerosol light scattering. Various aerosol optical and microphysical parameters were recorded using in-situ and remote sensing techniques. In-situ measurements of aerosol size distribution, light scattering, light absorption and scattering enhancement due to water uptake were performed at the JFJ at 3580 m (a.s.l.). A unique set-up allowed remote sensing measurements of aerosol columnar and vertical properties from the KLS located about 1500 m below and within the line of sight to the JFJ (horizontal distance of approx. 4.5 km). In addition, two satellite retrievals from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) and the Moderate Resolution Imaging Spectroradiometer (MODIS) as well as back trajectory analyses were added to the comparison to account for a wider geographical context. All in-situ and remote sensing measurements were in clear correspondence. The ambient extinction coefficient measured in-situ at the JFJ agreed well with the KLS-based LIDAR (Light Detection and Ranging) retrieval at the altitude-level of the JFJ under plausible assumptions on the LIDAR ratio. However, we can show that the quality of this comparison is affected by orographic effects due to the exposed location of the JFJ on a saddle between two mountains and next to a large glacier. The local RH around the JFJ was often higher than in the optical path of the LIDAR measurement, especially when the wind originated from the south via the glacier, leading to orographic clouds which remained lower than the LIDAR beam. Furthermore, the dominance of long-range transported Saharan dust was observed in all measurements for several days, however only for a shorter time period in the in-situ measurements due to the vertical structure of the dust plume. The optical properties of the aerosol column retrieved from SEVIRI and MODIS showed the same magnitude and a similar temporal evolution as the measurements at the KLS and the JFJ. Remaining differences are attributed to the complex terrain and simplifications in the aerosol retrieval scheme in general.

scholarly journals Automated ground-based remote sensing measurements of greenhouse gases at the Białystok site in comparison with collocated in-situ measurements and model data

2011 ◽  
Vol 11 (12) ◽  
pp. 32245-32282 ◽  
Author(s):  
J. Messerschmidt ◽  
H. Chen ◽  
N. M. Deutscher ◽  
C. Gerbig ◽  
P. Grupe ◽  
...  
Keyword(s):  
Remote Sensing ◽  
In Situ Measurements ◽  
Automation System ◽  
Fourier Transform Spectrometer ◽  
Model Data ◽  
Solar Absorption ◽  
Monthly Variations ◽  
Absorption Measurements ◽  
Good Agreement

Abstract. The fully automated observatory for total greenhouse gas (GHG) column measurements introduced here complements the in-situ facilities at the Białystok site in Poland. With the automated Fourier Transform Spectrometer (FTS), solar absorption measurements have been recorded nearly continuously since March 2009. In this article the automation system, including the hardware components and the automation software will be described in its basics. Furthermore the first comparison of the FTS dataset with the collocated in-situ measurements and the first comparison of the Jena CO2 inversion model are presented. This model identifies monthly variations in the total CO2 column and the seasonal amplitude is in good agreement with the FTS measurements.

Particulate matter variability in Kathmandu based on in-situ measurements, remote sensing, and reanalysis data

2021 ◽  
pp. 105623
Author(s):  
Stefan Becker ◽  
Ramesh Prasad Sapkota ◽  
Binod Pokharel ◽  
Loknath Adhikari ◽  
Rudra Prasad Pokhrel ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Particulate Matter ◽  
Reanalysis Data ◽  
In Situ Measurements

scholarly journals Aerosol measurements at the Gual Pahari EUCAARI station: preliminary results from in-situ measurements

2010 ◽  
Vol 10 (15) ◽  
pp. 7241-7252 ◽  
Author(s):  
A.-P. Hyvärinen ◽  
H. Lihavainen ◽  
M. Komppula ◽  
T. S. Panwar ◽  
V. P. Sharma ◽  
...  
Keyword(s):  
Rainy Season ◽  
In Situ Measurements ◽  
Aerosol Size Distribution ◽  
Finnish Meteorological Institute ◽  
Convective Mixing ◽  
Average Fraction ◽  
Mode Size ◽  
First Time ◽  
Pm10 Mass

Abstract. The Finnish Meteorological Institute (FMI), together with The Energy and Resources Institute of India (TERI), contributed to the European Integrated project on Aerosol Cloud Climate and Air Quality Interactions, EUCAARI, by conducting aerosol measurements in Gual Pahari, India, from December 2007 to January 2010. This paper describes the station setup in detail for the first time and provides results from the aerosol in-situ measurements, which include PM and BCe masses, aerosol size distribution from 4 nm to 10 μm, and the scattering and absorption coefficients. The seasonal variation of the aerosol characteristics was very distinct in Gual Pahari. The highest concentrations were observed during the winter and the lowest during the rainy season. The average PM10 concentration (at STP conditions) was 216 μgm−3 and the average PM2.5 concentration was 126 μgm−3. A high percentage (4–9%) of the PM10 mass consisted of BCe which indicates anthropogenic influence. The percentage of BCe was higher during the winter; and according to the diurnal pattern of the BCe fraction, the peak occurred during active traffic hours. Another important source of aerosol particles in the area was new particle formation. The nucleated particles grew rapidly reaching the Aitken and accumulation mode size, thus contributing considerably to the aerosol load. The rainy season decreased the average fraction of particle mass in the PM2.5 size range, i.e. of secondary origin. The other mechanism decreasing the surface concentrations was based on convective mixing and boundary layer evolution. This diluted the aerosol when sun radiation and the temperature was high, i.e. especially during the pre-monsoon day time. The lighter and smaller particles were more effectively diluted.

scholarly journals Aerosol optical and microphysical retrievals from a hybrid multiwavelength lidar data set – DISCOVER-AQ 2011

2014 ◽  
Vol 7 (9) ◽  
pp. 3095-3112 ◽  
Author(s):  
P. Sawamura ◽  
D. Müller ◽  
R. M. Hoff ◽  
C. A. Hostetler ◽  
R. A. Ferrare ◽  
...  
Keyword(s):  
Remote Sensing ◽  
In Situ Measurements ◽  
Index Of Refraction ◽  
High Spectral Resolution ◽  
Lidar Data ◽  
Data Set ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Multiwavelength Lidar

Abstract. Retrievals of aerosol microphysical properties (effective radius, volume and surface-area concentrations) and aerosol optical properties (complex index of refraction and single-scattering albedo) were obtained from a hybrid multiwavelength lidar data set for the first time. In July 2011, in the Baltimore–Washington DC region, synergistic profiling of optical and microphysical properties of aerosols with both airborne (in situ and remote sensing) and ground-based remote sensing systems was performed during the first deployment of DISCOVER-AQ. The hybrid multiwavelength lidar data set combines ground-based elastic backscatter lidar measurements at 355 nm with airborne High-Spectral-Resolution Lidar (HSRL) measurements at 532 nm and elastic backscatter lidar measurements at 1064 nm that were obtained less than 5 km apart from each other. This was the first study in which optical and microphysical retrievals from lidar were obtained during the day and directly compared to AERONET and in situ measurements for 11 cases. Good agreement was observed between lidar and AERONET retrievals. Larger discrepancies were observed between lidar retrievals and in situ measurements obtained by the aircraft and aerosol hygroscopic effects are believed to be the main factor in such discrepancies.

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