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18 pages, 5070 KiB

Open AccessArticle

Estimation of the Mass Concentration of Volcanic Ash Using Ceilometers: Study of Fresh and Transported Plumes from La Palma Volcano

by Andres E. Bedoya-Velásquez, Manuela Hoyos-Restrepo, Africa Barreto, Rosa D. García, Pedro Miguel Romero-Campos, Omaira García, Ramón Ramos, Reijo Roininen, Carlos Toledano, Michaël Sicard and Romain Ceolato

Remote Sens. 2022, 14(22), 5680; https://doi.org/10.3390/rs14225680 - 10 Nov 2022

Cited by 11 | Viewed by 2747

Abstract

This study presents a synergistic approach to the study of the aerosol optical and microphysical properties measured in La Palma, Spain, during the 2021 eruption of the Cumbre Vieja volcano (from 19 September to 13 December 2021). This study aims to characterize the [...] Read more.

This study presents a synergistic approach to the study of the aerosol optical and microphysical properties measured in La Palma, Spain, during the 2021 eruption of the Cumbre Vieja volcano (from 19 September to 13 December 2021). This study aims to characterize the different phases of the volcanic eruption using the spatio-temporal evolution of the event together with the mass concentration quantification of four different atmospheric layers. The impact of the plume’s pathway that reached the South of France is analyzed. Here, passive and active remote sensors were used, namely CL51 and CL61 ceilometers and AERONET sunphotometers. The attenuated backscattering ranged from 0.8 to 9.1 × 10

^{- 6}

(msr)

^{- 1}

and the volume depolarization ratio measured nearby the volcano was up to 0.3. The ash plume remained within the first 4 km agl, with intense episodes that reached mean aerosol optical depth values of up to 0.4. Thirteen study cases were selected where coarse mode was dominant over fine mode. For the data selection, the fine and coarse lidar ratios found were 3.9 ± 0.8 and 21.0 ± 3.8 sr in the north and 6.9 ± 1.8 and 30.1 ± 10.3 sr in the south. The ash mass concentration reached moderate levels with maximum values of up to 313.7

μ

gm

^{- 3}

. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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15 pages, 1829 KiB

Open AccessArticle

On the Sensitivity of a Ground-Based Tropospheric Lidar to Aitken Mode Particles in the Upper Troposphere

by Matheus T. Silva, Juan Luis Guerrero-Rascado, Alexandre L. Correia, Diego A. Gouveia and Henrique M. J. Barbosa

Remote Sens. 2022, 14(19), 4913; https://doi.org/10.3390/rs14194913 - 1 Oct 2022

Viewed by 1791

Abstract

Airborne observations have shown high concentrations of ultrafine aerosols in the Amazon upper troposphere (UT), which are key for replenishing the planetary boundary layer (PBL) with cloud condensation nuclei that sustain the “green ocean” clouds. Given their climatic relevance, long-term observations are needed, [...] Read more.

Airborne observations have shown high concentrations of ultrafine aerosols in the Amazon upper troposphere (UT), which are key for replenishing the planetary boundary layer (PBL) with cloud condensation nuclei that sustain the “green ocean” clouds. Given their climatic relevance, long-term observations are needed, but aircraft measurements are only available in short-term campaigns. Alternatively, continuous observations of the aerosol vertical structure could be performed by a lidar (acronym for “light detection and ranging”) system in long-term campaigns. Here we assess whether a ground-based tropospheric lidar system could detect these ultrafine UT aerosols. To this aim, we simulated the lidar signal of a real instrument and then varied the instrument’s efficiency and the UT-particle concentration to determine under which conditions the detection is possible. Optical properties were computed with a Mie code based on the size distributions and numerical concentration profiles measured by the aircraft, and on the refractive indexes inverted from AERONET measurements. The aerosol optical depth (AOD) was retrieved by inverting the elastic lidar signal, and a statistical test was applied to evaluate the detection of the UT-aerosol layer. Our results indicate that, for the instrument we simulated, a 55-fold increase in the signal-to-noise ratio (SNR) is required for a 100% detection rate. This could be achieved by simultaneously time averaging over 30 min and spatially averaging to vertical bin lengths of 375 m, or by modifying the hardware. We repeated the analysis for under- and overestimated aerosol lidar ratio (L

_{a e r}

), and found that possible systematic errors did not affect the detection rate. Further studies are necessary to assess whether such long-time averages are feasible in the Amazon region (given the very high cloud cover), and to design a hardware upgrade. Although simulations and analyses here were based on a particular instrument and for the presence of new organic particles in the Amazonian upper troposphere, our methodology and results are general and applicable to other instruments and sites. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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15 pages, 3281 KiB

Open AccessArticle

Gravity Wave Parameters and Their Seasonal Variations Study near 120°E China Based on Na LIDAR Observations

by Xu Zou, Guotao Yang, Paulo Prado Batista, Jihong Wang, Vania F. Andrioli, Xuewu Cheng, Jing Jiao, Lifang Du, Tiemin Zhang, Hong Yang, Zelong Wang and Yuan Xia

Remote Sens. 2022, 14(19), 4798; https://doi.org/10.3390/rs14194798 - 26 Sep 2022

Viewed by 1684

Abstract

Based on the established LIDAR chain along the 120°E meridian in China, the gravity wave (GW) activity between 80 and 105 km and the seasonal behavior of temporal and spatial spectra at Beijing, Hefei and Hainan were studied with three years of continued [...] Read more.

Based on the established LIDAR chain along the 120°E meridian in China, the gravity wave (GW) activity between 80 and 105 km and the seasonal behavior of temporal and spatial spectra at Beijing, Hefei and Hainan were studied with three years of continued observations. The averaged GW-induced atmospheric density perturbations are near 6%, which in summer are obviously larger than in winter. The semiannual maxima occur near the solstice and the minimum emerges around the equinox at different latitudes. Besides, as a disparity, the density perturbation of GW is still active considerably in winter at low latitude at Hainan. The spectra of vertical wave number Fa(m) and observed frequency Fa(ω) show power law shapes, of which the average is near −3 and −1.7, respectively, and both spectra with special values all exhibit similar seasonal behavior as the atmospheric density perturbations shows. This behavior is explained by multiple effects possibly originating from Tibet plateau (TP) and the main GW source in China was roughly calculated by the LIDAR observation method for the first time located at the TP boundary. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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22 pages, 4500 KiB

Open AccessArticle

Uncertainty Assessment of Differential Absorption Lidar Measurements of Industrial Emissions Concentrations

by Fabrizio Innocenti, Tom Gardiner and Rod Robinson

Remote Sens. 2022, 14(17), 4291; https://doi.org/10.3390/rs14174291 - 31 Aug 2022

Cited by 4 | Viewed by 1774

Abstract

Differential absorption lidar (DIAL) has been shown to be a very effective technique for the location and quantification of emissions of pollutants and greenhouse gases at industrial facilities. Several field trials have demonstrated the DIAL system performances and contributed to the development of [...] Read more.

Differential absorption lidar (DIAL) has been shown to be a very effective technique for the location and quantification of emissions of pollutants and greenhouse gases at industrial facilities. Several field trials have demonstrated the DIAL system performances and contributed to the development of the DIAL methodology, which is the basis of the protocols described in the European Standard EN 17628. While numerous papers have focused on different aspects of DIAL uncertainties, a rigorous propagation of the uncertainties in the DIAL equation has not been found. In this study, all the uncertainty sources contributing to a DIAL concentration measurement are assessed and the impact they have on the calculation of the mass emission rate. We derive the equations for both a DIAL system path-concentration integral and concentration uncertainties. The results from a methane measurement are presented, showing that for a signal to noise ratio on the backscattered lidar signals of 500, the path-concentration integral standard uncertainty is 2.3 ppb km and the concentration standard uncertainty is 92 ppb over a sampling spacing of 45 m. An equation is also presented enabling calculation of the contribution of the concentration uncertainty to the mass emission rate uncertainty. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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13 pages, 1579 KiB

Open AccessCommunication

Laboratory Evaluation of the (355, 532) nm Particle Depolarization Ratio of Pure Pollen at 180.0° Lidar Backscattering Angle

by Danaël Cholleton, Patrick Rairoux and Alain Miffre

Remote Sens. 2022, 14(15), 3767; https://doi.org/10.3390/rs14153767 - 5 Aug 2022

Cited by 4 | Viewed by 1814

Abstract

While pollen is expected to impact public human health and the Earth’s climate more and more in the coming decades, lidar remote sensing of pollen has become an important developing research field. To differentiate among the pollen taxa, a polarization lidar is an [...] Read more.

While pollen is expected to impact public human health and the Earth’s climate more and more in the coming decades, lidar remote sensing of pollen has become an important developing research field. To differentiate among the pollen taxa, a polarization lidar is an interesting tool since pollen exhibit non-spherical complex shapes. A key attribute is thus the lidar particle depolarization ratio (PDR) of pollen, which is however difficult to quantify as pollen are large and complex-shaped particles, far beyond the reach of light scattering numerical simulations. In this paper, a laboratory π-polarimeter is used to accurately evaluate the PDR of pure pollen, for the first time at the lidar exact backscattering angle of 180.0°. We hence reveal the lidar PDR of pure ragweed, ash, birch, pine, cypress and spruce pollens at 355 and 532 nm lidar wavelengths, as presented at the ELC 2021 conference. A striking result is the spectral dependence of the lidar PDR, highlighting the importance of dual-wavelength (or more) polarization lidars to identify pollen taxa. These spectral and polarimetric fingerprints of pure pollen, as they are accurate, can be used by the lidar community to invert multi-wavelength lidar polarization measurements involving pollen. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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21 pages, 3896 KiB

Open AccessArticle

Retrieval of Aged Biomass-Burning Aerosol Properties by Using GRASP Code in Synergy with Polarized Micro-Pulse Lidar and Sun/Sky Photometer

by María-Ángeles López-Cayuela, Milagros E. Herrera, Carmen Córdoba-Jabonero, Daniel Pérez-Ramírez, Clara Violeta Carvajal-Pérez, Oleg Dubovik and Juan Luis Guerrero-Rascado

Remote Sens. 2022, 14(15), 3619; https://doi.org/10.3390/rs14153619 - 28 Jul 2022

Cited by 3 | Viewed by 2081

Abstract

The aim of this study was to analyze the potential of the GRASP code to retrieve optical and microphysical properties vertically-resolved using a synergy of polarized Micro-Pulse Lidar and Sun/sky photometer observations. The focus was on the long-range transport of Canadian aged-smoke plumes [...] Read more.

The aim of this study was to analyze the potential of the GRASP code to retrieve optical and microphysical properties vertically-resolved using a synergy of polarized Micro-Pulse Lidar and Sun/sky photometer observations. The focus was on the long-range transport of Canadian aged-smoke plumes observed at El Arenosillo/Huelva (Spain) from 7 to 8 September 2017. Both the columnar and height-resolved microphysical and optical properties were assessed in comparison with AERONET data and vertical lidar-retrieved profiles, respectively. In particular, the vertical properties were also derived using the POLIPHON approach, which serves as a comparison for GRASP retrievals. The retrieved columnar aerosol microphysical properties (volume concentration and effective radius) showed an excellent agreement, with negligible differences, and were within the uncertainties. Nevertheless, for the retrieved columnar optical properties, we could only perform an individual comparison, due to the strong AERONET limitations, and although the agreements were generally good, no conclusions were obtained, due to differences in the real refractive index and due to the large uncertainties obtained in the retrievals. For the vertical profiles, however, we present a large advance that permits obtaining aerosol backscatter and extinction coefficients, plus volume concentrations, without the need for internal assumptions (extinction-to-backscatter ratios and depolarization measurements), due to the very good agreement observed between GRASP and the lidar-derived methodologies. However, the separation of the properties into their fine and coarse modes was not feasible using the one-wavelength elastic lidar measurements with the GRASP retrieval configuration used in this work. Therefore, current studies are being addressed to assessing the introduction of lidar depolarization in the GRASP code as an encouraged added-value, for the improvement of the retrieval of vertical aerosol properties. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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26 pages, 4809 KiB

Open AccessArticle

Aeronautics Application of Direct-Detection Doppler Wind Lidar: An Adapted Design Based on a Fringe-Imaging Michelson Interferometer as Spectral Analyzer

by Patrick Vrancken and Jonas Herbst

Remote Sens. 2022, 14(14), 3356; https://doi.org/10.3390/rs14143356 - 12 Jul 2022

Cited by 10 | Viewed by 2915

Abstract

We report on the development of a novel direct-detection Doppler wind lidar (DD-DWL) within the strong requirements of an aeronautic feed-forward control application for gust load alleviation (GLA). This DD-DWL is based on fringe imaging of the Doppler-shifted backscatter of ultraviolet laser pulses [...] Read more.

We report on the development of a novel direct-detection Doppler wind lidar (DD-DWL) within the strong requirements of an aeronautic feed-forward control application for gust load alleviation (GLA). This DD-DWL is based on fringe imaging of the Doppler-shifted backscatter of ultraviolet laser pulses in a field-widened Michelson interferometer (FW-FIMI) using a fast linear photodetector. The double approach of detailed simulation and demonstrator development is validated by field measurements with reference wind sensing instrumentation. These experiments allow us to establish wind determination precision at a high repeat rate, short range resolution and close distance of approximately 0.5 m/s, which is in accordance with the dedicated simulations. These findings lead us to the conclusion that this FW-FIMI-based Doppler wind lidar is a pertinent development meeting the special requirements of this aeronautics application. Second, the developed simulators are well suited (given their validation) to be used in the overall and full analysis as well as the optimization of the lidar-based GLA control scheme. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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21 pages, 8539 KiB

Open AccessArticle

Wind and Turbulence Statistics in the Urban Boundary Layer over a Mountain–Valley System in Granada, Spain

by Pablo Ortiz-Amezcua, Alodía Martínez-Herrera, Antti J. Manninen, Pyry P. Pentikäinen, Ewan J. O’Connor, Juan Luis Guerrero-Rascado and Lucas Alados-Arboledas

Remote Sens. 2022, 14(10), 2321; https://doi.org/10.3390/rs14102321 - 11 May 2022

Cited by 9 | Viewed by 3027

Abstract

Urban boundary layer characterization is currently a challenging and relevant issue, because of its role in weather and air quality modelling and forecast. In many cities, the effect of complex topography at local scale makes this modelling even more complicated. This is the [...] Read more.

Urban boundary layer characterization is currently a challenging and relevant issue, because of its role in weather and air quality modelling and forecast. In many cities, the effect of complex topography at local scale makes this modelling even more complicated. This is the case of mid-latitude urban areas located in typical basin topographies, which usually present low winds and high turbulence within the atmospheric boundary layer (ABL). This study focuses on the analysis of the first ever measurements of wind with high temporal and vertical resolution throughout the ABL over a medium-sized city surrounded by mountains in southern Spain. These measurements have been gathered with a scanning Doppler lidar system and analyzed using the Halo lidar toolbox processing chain developed at the Finnish Meteorological Institute. We have used the horizontal wind product and the ABL turbulence classification product to carry out a statistical study using a two-year database. The data availability in terms of maximum analyzed altitudes for statistically significant results was limited to around 1000–1500 m above ground level (a.g.l.) due to the decreasing signal intensity with height that also depends on aerosol load. We have analyzed the differences and similarities in the diurnal evolution of the horizontal wind profiles for different seasons and their modelling with Weibull and von Mises probability distributions, finding a general trend of mean daytime wind from the NW with mean speeds around 3–4 m/s at low altitudes and 6–10 m/s at higher altitudes, and weaker mean nocturnal wind from the SE with similar height dependence. The highest speeds were observed during spring, and the lowest during winter. Finally, we studied the turbulent sources at the ABL with temporal (for each hour of the day) and height resolution. The results show a clear convective activity during daytime at altitudes increasing with time, and a significant wind-shear-driven turbulence during night-time. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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21 pages, 2965 KiB

Open AccessArticle

Comparison of Scanning LiDAR with Other Remote Sensing Measurements and Transport Model Predictions for a Saharan Dust Case

by Hengheng Zhang, Frank Wagner, Harald Saathoff, Heike Vogel, Gholamali Hoshyaripour, Vanessa Bachmann, Jochen Förstner and Thomas Leisner

Remote Sens. 2022, 14(7), 1693; https://doi.org/10.3390/rs14071693 - 31 Mar 2022

Cited by 4 | Viewed by 2536

Abstract

The evolution and the properties of a Saharan dust plume were studied near the city of Karlsruhe in southwest Germany (8.4298°E, 49.0953°N) from 7 to 9 April 2018, combining a scanning LiDAR (90°, 30°), a vertically pointing LiDAR (90°), a sun photometer, and [...] Read more.

The evolution and the properties of a Saharan dust plume were studied near the city of Karlsruhe in southwest Germany (8.4298°E, 49.0953°N) from 7 to 9 April 2018, combining a scanning LiDAR (90°, 30°), a vertically pointing LiDAR (90°), a sun photometer, and the transport model ICON-ART. Based on this Saharan dust case, we discuss the advantages of a scanning aerosol LiDAR and validate a method to determine LiDAR ratios independently. The LiDAR measurements at 355 nm showed that the dust particles had backscatter coefficients of 0.86 ± 0.14 Mm

^{- 1}

sr

^{- 1}

, extinction coefficients of 40 ± 0.8 Mm

^{- 1}

, a LiDAR ratio of 46 ± 5 sr, and a linear particle depolarisation ratio of 0.27 ± 0.023. These values are in good agreement with those obtained in previous studies of Saharan dust plumes in Western Europe. Compared to the remote sensing measurements, the transport model predicted the plume arrival time, its layer height, and its structure quite well. The comparison of dust plume backscatter values from the ICON-ART model and observations for two days showed a correlation with a slope of 0.9 ± 0.1 at 355 nm. This work will be useful for future studies to characterise aerosol particles employing scanning LiDARs. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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25 pages, 7918 KiB

Open AccessArticle

Lidar and Radar Signal Simulation: Stability Assessment of the Aerosol–Cloud Interaction Index

by Carlos Mario Fajardo-Zambrano, Juan Antonio Bravo-Aranda, María José Granados-Muñoz, Elena Montilla-Rosero, Juan Andrés Casquero-Vera, Fernando Rejano, Sonia Castillo and Lucas Alados-Arboledas

Remote Sens. 2022, 14(6), 1333; https://doi.org/10.3390/rs14061333 - 9 Mar 2022

Cited by 2 | Viewed by 2969

Abstract

Aerosol–cloud interactions (ACI) are in the spotlight of atmospheric science since the limited knowledge about these processes produces large uncertainties in climate predictions. These interactions can be quantified by the aerosol–cloud interaction index (ACI index), which establishes a relationship between aerosol and cloud [...] Read more.

Aerosol–cloud interactions (ACI) are in the spotlight of atmospheric science since the limited knowledge about these processes produces large uncertainties in climate predictions. These interactions can be quantified by the aerosol–cloud interaction index (ACI index), which establishes a relationship between aerosol and cloud microphysics. The experimental determination of the ACI index through a synergistic combination of lidar and cloud radar is still quite challenging due to the difficulties in disentangling the aerosol influence on cloud formation from other processes and in retrieving aerosol-particle and cloud microphysics from remote sensing measurements. For a better understanding of the ACI and to evaluate the optimal experimental conditions for the measurement of these processes, a Lidar and Radar Signal Simulator (LARSS) is presented. LARSS simulate vertically-resolved lidar and cloud-radar signals during the formation process of a convective cloud, from the aerosol hygroscopic enhancement to the condensation droplet growth. Through LARSS simulations, it is observed a dependence of the ACI index with height, associated with the increase in number (

A C I_{N d}

) and effective radius (

A C I_{r e f f}

) of the droplets with altitude. Furthermore,

A C I_{N d}

and

A C I_{r e f f}

for several aerosol types (such as ammonium sulfate, biomass burning, and dust) are estimated using LARSS, presenting different values as a function of the aerosol model. Minimum

A C I_{N d}

values are obtained when the activation of new droplets stops, while

A C I_{r e f f}

reaches its maximum values several meters above. These simulations are carried out considering standard atmospheric conditions, with a relative humidity of

30 %

at the surface, reaching the supersaturation of the air mass at 3500 m. To assess the stability of the ACI index, a sensitivity study using LARSS is performed. It is obtained that the dry modal aerosol radius presents a strong influence on the ACI index fluctuations of

18 %

cause an ACI variability of

30 %

while the updraft velocity within the cloud and the wet modal aerosol radius have a weaker impact. LARSS ACI index uncertainty is obtained through the Monte Carlo technique, obtaining

A C I_{r e f f}

uncertainty below

16 %

for the uncertainty of all LARSS input parameters of

10 %

. Finally, a new ACI index is introduced in this study, called the remote-sensing ACI index (

A C I_{R s}

), to simplify the quantification of the ACI processes with remote sensors. This new index presents a linear relationship with the

A C I_{r e f f}

, which depends on the Angstrom exponent. The use of

A C I_{R s}

to derive

A C I_{r e f f}

presents the advantage that it is possible to quantify the aerosol–cloud interaction without the need to perform microphysical inversion retrievals, thus reducing the uncertainty sources. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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24 pages, 10670 KiB

Open AccessArticle

Towards Early Detection of Tropospheric Aerosol Layers Using Monitoring with Ceilometer, Photometer, and Air Mass Trajectories

by Mariana Adam, Konstantinos Fragkos, Ioannis Binietoglou, Dongxiang Wang, Iwona S. Stachlewska, Livio Belegante and Victor Nicolae

Remote Sens. 2022, 14(5), 1217; https://doi.org/10.3390/rs14051217 - 2 Mar 2022

Cited by 5 | Viewed by 3376

Abstract

A near-real-time automatic detection system, based on the synergy of continuous measurements taken by a ceilometer and a photometer, has been implemented in order to detect lofted atmospheric aerosol layers and estimate the aerosol load. When heavy-loaded conditions are detected (defined by a [...] Read more.

A near-real-time automatic detection system, based on the synergy of continuous measurements taken by a ceilometer and a photometer, has been implemented in order to detect lofted atmospheric aerosol layers and estimate the aerosol load. When heavy-loaded conditions are detected (defined by a significant deviation of the optical properties from a 10-year climatology), obtained for aerosol layers above 2500 m, an automatic alert is sent to scientists of the Romanian Lidar Network (ROLINET) to further monitor the event. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) back-trajectory calculations are used to establish the possible pollution source. The aerosol transport events are considered to be major when various optical properties provided by the photometer are found outside the climatological values. The aerosol types over the three years for all the events identified revealed that the contribution to the pollution was 31%, 9%, and 60% from marine, dust, and continental types. Considering only the ‘outside climatology limits’ events, the respective contribution was 15%, 12%, and 73% for marine, dust, and continental types, respectively. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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17 pages, 16814 KiB

Open AccessArticle

Advection of Biomass Burning Aerosols towards the Southern Hemispheric Mid-Latitude Station of Punta Arenas as Observed with Multiwavelength Polarization Raman Lidar

by Athena Augusta Floutsi, Holger Baars, Martin Radenz, Moritz Haarig, Zhenping Yin, Patric Seifert, Cristofer Jimenez, Albert Ansmann, Ronny Engelmann, Boris Barja, Felix Zamorano and Ulla Wandinger

Remote Sens. 2021, 13(1), 138; https://doi.org/10.3390/rs13010138 - 4 Jan 2021

Cited by 14 | Viewed by 3634

Abstract

In this paper, we present long-term observations of the multiwavelength Raman lidar Polly

^{X T}

conducted in the framework of the DACAPO-PESO campaign. Regardless of the relatively clean atmosphere in the southern mid-latitude oceans region, we regularly observed events of long-range transported smoke, [...] Read more.

In this paper, we present long-term observations of the multiwavelength Raman lidar Polly

^{X T}

conducted in the framework of the DACAPO-PESO campaign. Regardless of the relatively clean atmosphere in the southern mid-latitude oceans region, we regularly observed events of long-range transported smoke, originating either from regional sources in South America or from Australia. Two case studies will be discussed, both identified as smoke events that occurred on 5 February 2019 and 11 March 2019. For the first case considered, the lofted smoke layer was located at an altitude between 1.0 and 4.2 km, and apart from the predominance of smoke particles, particle linear depolarization values indicated the presence of dust particles. Mean lidar ratio values at 355 and 532 nm were 49 ± 12 and 24 ± 18 sr respectively, while the mean particle linear depolarization was 7.6 ± 3.6% at 532 nm. The advection of smoke and dust particles above Punta Arenas affected significantly the available cloud condensation nuclei (CCN) and ice nucleating particles (INP) in the lower troposphere, and effectively triggered the ice crystal formation processes. Regarding the second case, the thin smoke layers were observed at altitudes 5.5–7.0, 9.0 and 11.0 km. The particle linear depolarization ratio at 532 nm increased rapidly with height, starting from 2% for the lowest two layers and increasing up to 9.5% for the highest layer, indicating the possible presence of non-spherical coated soot aggregates. INP activation was effectively facilitated. The long-term analysis of the one year of observations showed that tropospheric smoke advection over Punta Arenas occurred 16 times (lasting from 1 to 17 h), regularly distributed over the period and with high potential to influence cloud formation in the otherwise pristine environment of the region. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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24 pages, 2626 KiB

Open AccessArticle

Toward Non-Invasive Measurement of Atmospheric Temperature Using Vibro-Rotational Raman Spectra of Diatomic Gases

by Tyler Capek, Jacek Borysow, Claudio Mazzoleni and Massimo Moraldi

Remote Sens. 2020, 12(24), 4129; https://doi.org/10.3390/rs12244129 - 17 Dec 2020

Cited by 4 | Viewed by 3005

Abstract

We demonstrate precise determination of atmospheric temperature using vibro-rotational Raman (VRR) spectra of molecular nitrogen and oxygen in the range of 292–293 K. We used a continuous wave fiber laser operating at 10 W near 532 nm as an excitation source in conjunction [...] Read more.

We demonstrate precise determination of atmospheric temperature using vibro-rotational Raman (VRR) spectra of molecular nitrogen and oxygen in the range of 292–293 K. We used a continuous wave fiber laser operating at 10 W near 532 nm as an excitation source in conjunction with a multi-pass cell. First, we show that the approximation that nitrogen and oxygen molecules behave like rigid rotors leads to erroneous derivations of temperature values from VRR spectra. Then, we account for molecular non-rigidity and compare four different methods for the determination of air temperature. Each method requires no temperature calibration. The first method involves fitting the intensity of individual lines within the same branch to their respective transition energies. We also infer temperature by taking ratios of two isolated VRR lines; first from two lines of the same branch, and then one line from the S-branch and one from the O-branch. Finally, we take ratios of groups of lines. Comparing these methods, we found that a precision up to 0.1 K is possible. In the case of O

_{2}

, a comparison between the different methods show that the inferred temperature was self-consistent to within 1 K. The temperature inferred from N

_{2}

differed by as much as 3 K depending on which VRR branch was used. Here we discuss the advantages and disadvantages of each method. Our methods can be extended to the development of instrumentation capable of non-invasive monitoring of gas temperature with broad potential applications, for example, in laboratory, ground-based, or airborne remote sensing. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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17 pages, 3024 KiB

Open AccessArticle

Study of the Effect of Aerosol Vertical Profile on Microphysical Properties Using GRASP Code with Sun/Sky Photometer and Multiwavelength Lidar Measurements

by Francisco Molero, Manuel Pujadas and Begoña Artíñano

Remote Sens. 2020, 12(24), 4072; https://doi.org/10.3390/rs12244072 - 12 Dec 2020

Cited by 9 | Viewed by 2471

Abstract

In this paper, we study the effect of the vertical distribution of aerosols on the inversion process to obtain microphysical properties of aerosols. The GRASP code is used to retrieve the aerosol size distribution from two different schemes. Firstly, only sun/sky photometer measurements [...] Read more.

In this paper, we study the effect of the vertical distribution of aerosols on the inversion process to obtain microphysical properties of aerosols. The GRASP code is used to retrieve the aerosol size distribution from two different schemes. Firstly, only sun/sky photometer measurements of aerosol optical depth and sky radiances are used as input to the retrieval code, and then, both this information and the range-corrected signals from an advanced lidar system are provided to the code. Measurements taken at the Madrid EARLINET station, complemented with those from the nearby AERONET station, have been analyzed for the 2016–2019 time range. The effect found of the measured vertical profile on the inversion is a shift to smaller radius of the fine mode with average differences of 0.05 ± 0.02 µm, without noticeable effects for the coarse mode radius. This coarse mode is sometimes split into two modes, related to large AOD or elevated aerosol-rich layers. The first scheme´s retrieved size distributions are also compared with those provided by AERONET, observing the unusual persistence of a large mode centered at 5 µm. These changes in the size distributions affect slightly the radiative forcing calculated also by the GRASP code. A stronger forcing, dependent on the AOD, is observed in the second scheme. The shift in the fine mode and the effect on the radiative forcing indicate the importance of considering the vertical profile of aerosols on the retrieval of microphysical properties by remote sensing. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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Jump to: Research

14 pages, 2895 KiB

Open AccessTechnical Note

First Ever Observations of Mineral Dust in Wintertime over Warsaw, Poland

by Dominika M. Szczepanik, Pablo Ortiz-Amezcua, Birgit Heese, Giuseppe D’Amico and Iwona S. Stachlewska

Remote Sens. 2022, 14(15), 3788; https://doi.org/10.3390/rs14153788 - 6 Aug 2022

Cited by 7 | Viewed by 1910

Abstract

The long-range transport of desert dust over the area of the temperate climate zone is associated with the influx of hot air masses due to the location of the sources of this aerosol in the tropical climate zone. Between 24–26 February 2021, such [...] Read more.

The long-range transport of desert dust over the area of the temperate climate zone is associated with the influx of hot air masses due to the location of the sources of this aerosol in the tropical climate zone. Between 24–26 February 2021, such an aerosol outbreak took place and reached Central Europe. The mean temperature of +11.7 °C was recorded during the event. A comparison of this value to the 20-year (2000–2020) average February temperature for Warsaw (−0.2 °C) indicates the uniqueness of the meteorological conditions. It was the first wintertime inflow of Saharan dust over Warsaw, the presence of which was confirmed by lidar and sun-photometer measurements. The properties of the desert dust layers were obtained; the mean values of the particle depolarization for the fully developed mineral dust layer were 13 ± 3% and 22 ± 4% for 355 and 532 nm, respectively. The aerosol optical thickness was high with average values >0.36 for all wavelengths smaller than 500 nm. The three-modal, aerosol size distribution was dominated by coarse-mode particles, with a visible contribution of accumulation-mode particles. It suggests the possible presence of other aerosol types. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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12 pages, 5887 KiB

Open AccessTechnical Note

Aerosol Monitoring at High Mountains Remote Station: A Case Study on the Yunnan Plateau (China)

by Alessia Sannino, Salvatore Amoruso, Antonella Boselli, Xuan Wang and Yiming Zhao

Remote Sens. 2022, 14(15), 3773; https://doi.org/10.3390/rs14153773 - 5 Aug 2022

Cited by 2 | Viewed by 1739

Abstract

In January 2016, a measurement campaign was carried out by the China Meteorological Administration, the Beijing Research Institute of Telemetry, and the Physics Department of the University of Naples “Federico II” in the Yulong Naxi Autonomous County (China) at 3200 m above sea [...] Read more.

In January 2016, a measurement campaign was carried out by the China Meteorological Administration, the Beijing Research Institute of Telemetry, and the Physics Department of the University of Naples “Federico II” in the Yulong Naxi Autonomous County (China) at 3200 m above sea level to evaluate the air quality in the high mountains with the lidar technique. Here we report on an interesting event that occurred on 16 January between 12.00 and 00.00 UTC, when a striking aerosol stratification was observed on the site. Aerosol transport events are studied starting from lidar characterization of different aerosol masses. From lidar signals at 355 and 532 nm, integrated on 30 min, the aerosol characterization is done in terms of aerosol depolarization ratio with a spatial resolution of 60 m and color ratio; these parameters allow for highlighting a phenomenon of aerosol transport from the Tibetan plateau planetary boundary layer and from northern India. The initial layer is composed of a mixture of aerosols characterized by average values of the aerosol depolarization ratio and the color ratio of (30 ± 2)% and (0.9 ± 0.2), respectively, indicating a large non-spherical aerosol composition. Then, the deposition of this aerosol load ensues, and aerosols with such features are progressively observed at lower altitudes. Full article

(This article belongs to the Special Issue Selected Papers of the European Lidar Conference)

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