GI4.2

EDI
Lidar remote sensing of the atmosphere

This session invites contributions on the latest developments and results in lidar remote sensing of the atmosphere, covering • new lidar techniques as well as applications of lidar data for model verification and assimilation, • ground-based, airborne, and space-borne lidar systems, • unique research systems as well as networks of instruments, • lidar observations of aerosols and clouds, thermodynamic parameters and wind, and trace-gases. Atmospheric lidar technologies have shown significant progress in recent years. While, some years ago, there were only a few research systems, mostly quite complex and difficult to operate on a longer-term basis because a team of experts was continuously required for their operation, advancements in laser transmitter and receiver technologies have resulted in much more rugged systems nowadays, many of which are already operated routinely in networks and some even being automated and commercially available. Consequently, also more and more data sets with very high resolution in range and time are becoming available for atmospheric science, which makes it attractive to consider lidar data not only for case studies but also for extended model comparison statistics and data assimilation. Here, ceilometers provide not only information on the cloud bottom height but also profiles of aerosol and cloud backscatter signals. Scanning Doppler lidars extend the data to horizontal and vertical wind profiles. Raman lidars and high-spectral resolution lidars provide more details than ceilometers and measure particle extinction and backscatter coefficients at multiple wavelengths. Other Raman lidars measure water vapor mixing ratio and temperature profiles. Differential absorption lidars give profiles of absolute humidity or other trace gases (like ozone, NOx, SO2, CO2, methane etc.). Depolarization lidars provide information on the shapes of aerosol and cloud particles. In addition to instruments on the ground, lidars are operated from airborne platforms in different altitudes. Even the first space-borne missions are now in orbit while more are currently in preparation. All these aspects of lidar remote sensing in the atmosphere will be part of this session.

Public information:
This session is on the latest developments and results in lidar remote sensing of the atmosphere, covering • new lidar techniques as well as applications of lidar data for model verification and assimilation, • ground-based, airborne, and space-borne lidar systems, • unique research systems as well as networks of instruments, • lidar observations of aerosols and clouds, thermodynamic parameters and wind, and trace-gases. Atmospheric lidar technologies have shown significant progress in recent years. While, some years ago, there were only a few research systems, mostly quite complex and difficult to operate on a longer-term basis because a team of experts was continuously required for their operation, advancements in laser transmitter and receiver technologies have resulted in much more rugged systems nowadays, many of which are already operated routinely in networks and some even being automated and commercially available. Consequently, also more and more data sets with very high resolution in range and time are becoming available for atmospheric science, which makes it attractive to consider lidar data not only for case studies but also for extended model comparison statistics and data assimilation. Here, ceilometers provide not only information on the cloud bottom height but also profiles of aerosol and cloud backscatter signals. Scanning Doppler lidars extend the data to horizontal and vertical wind profiles. Raman lidars and high-spectral resolution lidars provide more details than ceilometers and measure particle extinction and backscatter coefficients at multiple wavelengths. Other Raman lidars measure water vapor mixing ratio and temperature profiles. Differential absorption lidars give profiles of absolute humidity or other trace gases (like ozone, NOx, SO2, CO2, methane etc.). Depolarization lidars provide information on the shapes of aerosol and cloud particles. In addition to instruments on the ground, lidars are operated from airborne platforms in different altitudes. Even the first space-borne missions are now in orbit while more are currently in preparation. All these aspects of lidar remote sensing in the atmosphere will be part of this session.
Co-organized by AS5
Convener: Andreas Behrendt | Co-conveners: Paolo Di Girolamo, Andreas Fix, Michael Sicard, Julien Totems
vPICO presentations
| Tue, 27 Apr, 15:30–17:00 (CEST)
Public information:
This session is on the latest developments and results in lidar remote sensing of the atmosphere, covering • new lidar techniques as well as applications of lidar data for model verification and assimilation, • ground-based, airborne, and space-borne lidar systems, • unique research systems as well as networks of instruments, • lidar observations of aerosols and clouds, thermodynamic parameters and wind, and trace-gases. Atmospheric lidar technologies have shown significant progress in recent years. While, some years ago, there were only a few research systems, mostly quite complex and difficult to operate on a longer-term basis because a team of experts was continuously required for their operation, advancements in laser transmitter and receiver technologies have resulted in much more rugged systems nowadays, many of which are already operated routinely in networks and some even being automated and commercially available. Consequently, also more and more data sets with very high resolution in range and time are becoming available for atmospheric science, which makes it attractive to consider lidar data not only for case studies but also for extended model comparison statistics and data assimilation. Here, ceilometers provide not only information on the cloud bottom height but also profiles of aerosol and cloud backscatter signals. Scanning Doppler lidars extend the data to horizontal and vertical wind profiles. Raman lidars and high-spectral resolution lidars provide more details than ceilometers and measure particle extinction and backscatter coefficients at multiple wavelengths. Other Raman lidars measure water vapor mixing ratio and temperature profiles. Differential absorption lidars give profiles of absolute humidity or other trace gases (like ozone, NOx, SO2, CO2, methane etc.). Depolarization lidars provide information on the shapes of aerosol and cloud particles. In addition to instruments on the ground, lidars are operated from airborne platforms in different altitudes. Even the first space-borne missions are now in orbit while more are currently in preparation. All these aspects of lidar remote sensing in the atmosphere will be part of this session.

vPICO presentations: Tue, 27 Apr

Chairpersons: Andreas Behrendt, Paolo Di Girolamo, Julien Totems
15:30–15:35
Aerosols & Clouds
15:35–15:45
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EGU21-5533
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solicited
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Highlight
Qiang Li and Silke Groß

Cirrus clouds have a wide global coverage providing considerable radiative forcing on the Earth’s climate system. Due to their inadequate representation in the global models, cirrus clouds can lead to large uncertainties in the climate prediction. To date, experimental and theoretical efforts have been widely carried out to study the anthropogenic effects such as aviation that may change the formation and microphysic and optical properties of cirrus clouds. Unfortunately, however, solid observational studies are still rare for us to draw any robust conclusion on anthropogenic influence on cirrus. During the COVID-19 pandemic the civil air traffic over Europe was significantly reduced. This unique situation provides a good opportunity to study the effect of air traffic on cirrus. In this work, based on the analysis of the CALIPSO measurements we present the changes of cirrus cloud properties and occurrence over Europe in March and April 2020 compared with the reference results in the previous years under normal conditions. The comparison shows that the cirrus cloud occurrence was reduced by about 30% with smaller cloud thicknesses found in April 2020. The average thickness of cirrus clouds was reduced to 1.18 km in April 2020 compared to a value of 1.40 km under normal conditions. In addition, the cirrus clouds measured in April 2020 possess smaller mean values of the particle linear depolarization ratio (PLDR) than the previous years at a high significance level, especially at colder temperatures (T<-50oC). The same exercises are extended to the observations over China and the United States. Besides the regional discrimination of cirrus clouds, we reach the final summary that cirrus clouds show significant changes in both March and April over Europe, no changes in both months over China, and significant changes only in April over the United States.

How to cite: Li, Q. and Groß, S.: Study of cirrus cloud properties and occurrence over Europe during the COVID-19 based on the lidar measurements of CALIPSO, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5533, https://doi.org/10.5194/egusphere-egu21-5533, 2021.

15:45–15:47
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EGU21-11495
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ECS
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Highlight
Benedetto De Rosa, Lucia Mona, Aldo Amodeo, and Donato Summa

Smoke aerosols play an important role in the atmospheric chemistry in terms of direct and indirect radiative forcing. Despite this, their properties in free troposphere and stratosphere are still insufficiently studied. When the smoke reaches these altitudes can be transported over transcontinental distances. During the transport of particles important transforming processes, such as coagulation, condensation, and gas-to-particle conversion occur, thus affecting environment and climate. The optical properties of smoke plumes have been usually analyzed by ground-based radiometers and satellite. However, these techniques cannot characterize accurately the high variability of the vertical structure of smoke aerosol. Raman lidar systems  are characterized by high temporal and vertical resolutions and have demonstrated a strong capability to study long-range transport, optical properties and vertical structure of forest fire smoke. 

In the 2020 California’s fire season was exceptionally catastrophic. 23rd October, the immense Sonoma fire, in few days scorched 31000 hectares. The deep convection lifted the smoke from these fires to great heights. After reaching the free troposphere and stratosphere, the forest fire smoke was transported over great distances and reached the south of Italy, as evinced by the map of biomass burning aerosol optical depth at 550 nm, provided by the Copernicus Atmosphere Monitoring Service (CAMS).

This work reports measurements carried out in the frame of the project CAMS21b by the Raman lidar system MUSA deployed at CNR-IMAA Atmospheric Observatory (CIAO) in Potenza. CAMS21b aims to design, test and set up the provisioning to CAMS of ACTRIS/EARLINET products in real time and near real time. 

In the case study of 26 October 2020, from to 10:13 to 13:45 UTC, measurements of particle backscattering coefficient at 355, 532 nm and 1064 and of the particle extinction coefficient at 355 nm and 532nm, show the presence of two distinct aerosol layers. A lower one extending from 6 km to 8 km and an upper one extending from 10 km to 12 km. The back-trajectory analysis reveals that the air masses originated over California, overpassed the Atlantic sea before reaching the measurement site.

The values of the particle depolarization ratio are similar to those found in literature for smoke aerosols. In the first layer, values lower than 0.05 are indicative for small and spherical smoke particles. The moderately increased depolarization ratios in the second layer indicate the possible presence of partly coated smoke particles.

More results from this measurement effort will be reported and discussed at the Conference.

How to cite: De Rosa, B., Mona, L., Amodeo, A., and Summa, D.: Observations of California forest fire aerosol in Potenza (Italy) by the multi-wavelength Raman lidar MUSA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11495, https://doi.org/10.5194/egusphere-egu21-11495, 2021.

15:47–15:49
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EGU21-12672
Alain Miffre, Danaël Cholleton, and Patrick Rairoux

This abstract is dedicated to dual-wavelength polarization lidars (2β+2δ) and related particles backscattering Ångström exponents BAEp, as nowadays remotely evaluated by atmospheric multi-wavelength lidar instruments (Veselovskii et al., ACP, 2016). We here present two new lidar remote sensing developments applicable to every multi-wavelengths polarization lidars, as published in Miffre et al. (Rem. Sens. 2019, Opt. Lett. 2020).

As a first development, we investigate the size, shape and complex refractive index dependence of measured backscattering Ångström exponents (Miffre et al., Opt. Lett., 2020). If BAEp is generally considered as a particles size indicator, it actually depends on the particles size, shape (Mehri et al., Atm. Res., 2018) and complex refractive index as βp does. From a precise analysis of the polarization state of the backscattered radiation and of its wavelength dependence, in two components particle mixtures (p) = {s, ns} involving spherical (s) and nonspherical (ns)-particles, we could establish the relationship between BAEp, BAEs and BAEns. Then, by numerically simulating the two latter, we could discuss on the range of involved particle sizes and complex refractive indices.

The second development is related to the remote sensing observation of a new particle formation event with a dual-wavelength polarization lidar (Miffre et al. Rem. Sens. 2019). Where previous thoughts were that it is not feasible due to the small size of involved particles, we identified the requirements ensuring a (UV, VIS) polarization lidar to be sensitive to the subsequent particles growth following nucleation events promoted by nonspherical mineral dust particles. The presentation will explicit these optical requirements in terms of polarization and spectroscopy, as recently published in (Miffre et al., Rem. Sens., 2019).

The oral presentation will first present our dual-wavelength polarization lidar remote sensing instrument (2β+2δ), based on an unique laboratory Pi-polarimeter (Miffre et al., JQSRT, 2016). Special focus will be made on the (UV, VIS) calibration of the polarization lidar, as a decisive point for precise observations and interpretations. As an application case study, the oral presentation will then consider the lidar remote sensing observation of a nucleation event promoted by mineral dust. There, the involved particles sizes of freshly nucleated sulfuric acid particles and mineral dust will be retrieved by considering the above backscattering Ångström exponents analysis. As expected, the retrieved involved particles sizes reveal the underlying physical-chemistry of the nucleation process promoted by mineral dust (Dupart et al., PNAS, 2012). We believe this work may then interest a wide community of scientists.

Veselovskii, I., P. Goloub, D. N. Whiteman, A. Diallo, T. Ndiaye, A. Kolgotin, and O. Dubovik, ACP, 16(11), (2016).
Dupart, Y., A. Wiedensohler, H. Hermann, A. Miffre, P. Rairoux, B. D’Anna and C. George, PNAS, 109, 51, (2012).
Miffre, A., T. Mehri, M. Francis and P. Rairoux, JQSRT, 169, 79-90, (2016).
Mehri, T., P. Rairoux, T. Nousiainen, A. Miffre, Atm. Res. 203, 44-61 (2018).
Miffre A, D Cholleton, T. Mehri and P Rairoux, Rem. Sens., 11(15), 1761, (2019).
Miffre, A., D. Cholleton, P. Rairoux, Opt. Lett. 45, 5, 1084-1087, (2020).

How to cite: Miffre, A., Cholleton, D., and Rairoux, P.: Lidar remote sensing of atmospheric aerosols: investigation of involved particles sizes using Backscattering Ångström Exponents and application to the remote observation of new particle formation events , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12672, https://doi.org/10.5194/egusphere-egu21-12672, 2021.

15:49–15:51
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EGU21-16279
Rodanthi-Elisavet Mamouri, Argyro Nisantzi, Ronny Engelman, Johannes Bühl, Patric Seifert, Holger Baars, Zhenping Yin, Diofantos Hadjimitsis, and Albert Ansmann

A new generation PollyXT lidar system start on 27th of October 2020, continuous operation, at Limassol, Cyprus.

The lidar system will become a key component within the EXCELSIOR H2020 EU Teaming project coordinated by the Cyprus University of Technology. The mission of the EXCELSIOR project is to upgrade the Remote Sensing & Geo-Environment Lab, established within the Faculty of Engineering & Technology of the Cyprus University of Technology, into a sustainable, viable and autonomous Centre of Excellence, called the ERATOSTHENES Center of Excellence (ECoE).

The PollyXT-CYP will be hosted by the ERATOSTHENES CoE for its permanent operation aiming to link the Centre to ACTRIS and PollyNet. Its task will be to document the complex mixture of the different aerosol species and clouds over the Eastern Mediterranean.

The system is continuously running and since the first observations in Limassol, PollyXT-CYP demostrates the complex aerosol conditions over Cyprus. For eaxample, between the 27th of October to the 1st of November 2020, the lidar observed smoke plumes from the extreme wildfires on the west coast of the U.S. The smoke travelled over the Atlantic Ocean and triggered the heterogenous ice formation at the height of 10km. Saharan dust was also detected between 2-5km and liquid clouds were formed on the top of the dust layer.

In this study we will present selected cases of unique atmospheric structures from the first months of continuous operation over Cyprus as well as optical and geometrical properties of the aerosol layers.

The PollyXT-CYP will be a key research infrastructure of the Cyprus Atmospheric Remote Sensing Observatory (CARO). CARO will consist of two high-tech containers housing the PollyXT-CYP lidar and state-of-the art doppler lidar, cloud radar and radiometric equipment which will be used to measure the air quality, the dust transport, and the cloud properties over Cyprus. The CARO is planned to become National Facility of the Republic of Cyprus for Aerosol and Cloud Remote Sensing Observations.

Acknowledgements

The authors acknowledge the EXCELSIOR project that received funding from the European Union [H2020-WIDESPREAD-04-2017:Teaming Phase2] project under grant agreement no. 857510, and from the Republic of Cyprus. CUT team acknowledge the Research and Innovation Foundation of Cyprus for the financial support through the SIROCCO (EXCELLENCE/1216/0217) and AQ-SERVE (INTERGRATED/0916/0016) projects. The PollyXT-CYP was funded by the German Federal Ministry of Education and Research (BMBF) via the PoLiCyTa project.

How to cite: Mamouri, R.-E., Nisantzi, A., Engelman, R., Bühl, J., Seifert, P., Baars, H., Yin, Z., Hadjimitsis, D., and Ansmann, A.: The ERATOSTHENES CoE in the PollyNET:First observations of the PollyXT-CYP at Limassol, Cyprus, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16279, https://doi.org/10.5194/egusphere-egu21-16279, 2021.

15:51–15:53
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EGU21-15153
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ECS
José-Alex Zenteno-Hernández, Adolfo Comerón-Tejero, Alejandro Rodríguez-Gómez, Constantino Muñoz-Porcar, Daniel-Camilo Fortunato-dos-Santos-Oliveira, and Michaël Sicard

Pure-rotational Raman (PRR) scattering has proven to be an efficient technique for the determination of atmospheric aerosol optical properties for lidar applications. We present the implementation of a UV-PRR and the design of a VIS-PRR in the EARLINET/UPC multi-wavelength lidar system (Barcelona, Spain). State-of-the-art computations of N2 and O2 differential backscatter cross-sections weighted by the optical losses inside the optical separation unit of the system allow for the theoretical estimation of the expected signal-to-noise ratios (SNR) in both UV and VIS channels. By means of customized optical interference filters UV-PRR signals from atmospheric N2 and O2 were detected and compared to the classical vibro-rotational Raman signals. UV-PRR detected signals have shown to possess high SNR and relative uncertainty levels lower than a tolerable 15% for daytime and nighttime measurements. The theoretical analysis of the VIS-PRR channel augurs improvements similar to those observed with the UV-PRR channel.

How to cite: Zenteno-Hernández, J.-A., Comerón-Tejero, A., Rodríguez-Gómez, A., Muñoz-Porcar, C., Fortunato-dos-Santos-Oliveira, D.-C., and Sicard, M.: Dual pure-rotational Raman channel design and implementation in a multiwavelength lidar system for the monitoring of aerosol optical properties., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15153, https://doi.org/10.5194/egusphere-egu21-15153, 2021.

15:53–15:55
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EGU21-11379
Joelle Buxmann, Martin Osborne, Mike Protts, and Debbie O'Sullivan

The Met Office operates a ground based operational network of nine polarisation Raman lidars (aerosol profiling instruments) and sun photometers (column integrated information). An aerosol classification scheme using supervised machine learning has been developed. The concept of Mahalanobis (~normalized) distance to identify the aerosol type  from individual Aerosol Robotic Network (AERONET) measurements including Extinction Angstrom Exponent, Absorption Angstrom Exponent, Single Scattering Albedo and Index of refraction is used for a subset of AERONET stations around the globe of known main aerosol types (training set). The aerosol types  include maritime, urban industrial, biomass burning and dust. We build a predictive model from this training set using K nearest neighbour machine learning algorithms. The relation of particle polarisation ratio and lidar ratio from the Raman lidar is used as a sanity check.  We apply the model to 3- 4 years of AERONET and profiling data across the UK, with instruments evenly distributed across the country, from Camborne in Cornwall to Lerwick in the Shetland Islands. We are showing more detailed data of a dust event in May 2016, dust/biomass burning aerosol mix from October 2017 (hurricane Ophelia) and more recent aerosol transported from the Canadian wild fires in September 2020. AERONET Level 2.0  data is compared to level 1.5 in order to determine the implications for the aerosol classification. Level 1.5 data are cloud-screened, but not quality assured and may not have the final calibration applied. Level 2.0  data have pre- and post-field calibration applied, are cloud-screened, and quality-assured data. As level 2.0 data is usually only available after 1-2 years (after a new calibration has been performed), it is important to understand the  usefulness of more readily available level 1.5 (cloud screened) data.

The aim is to build a real time aerosol classification application that can be used in Nowcasting.

How to cite: Buxmann, J., Osborne, M., Protts, M., and O'Sullivan, D.: Aerosol classification using sun photometer and lidar data within a machine learning algorithm-a possible nowcasting application, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11379, https://doi.org/10.5194/egusphere-egu21-11379, 2021.

15:55–15:57
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EGU21-5123
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ECS
Shu Yang, Guðrún Nína Petersen, Sibylle von Löwis, and David C. Finger

Lidar systems have been used widely to measure wind profiles and atmospheric aerosols. The scanning Doppler lidars operated by the Icelandic Meteorological Office (IMO) can provide continuous measurements of the wind velocity and direction based on the Doppler effect from the emitted signals, as well as the backscatter coefficient and depolarization ratio for retrieving aerosol properties. In this project, we investigate the use of Doppler lidar in Iceland, especially for enhancing aviation safety. By analyzing the data three main tasks have been tackled: i) atmospheric turbulence measurements; ii) airborne aerosol detection; iii) real-time lidar signal classification with machine learning algorithms. An algorithm has been developed based on Kolmogorov theory to retrieve eddy dissipation ratio, as an indicator of turbulence intensity, from lidar wind measurements, and the method has been tested on two cases in 2017. With a combination of ceilometer, sun-photometer and other instruments, the Doppler lidar shows the ability to detect aerosols, including dust and volcanic ash in Iceland. With both supervised and unsupervised machine learning algorithms, two models have been developed to identify the noise signal and classify the lidar measurements, which could provide a real-time lidar signal classification for the end-users. The results indicate that the Doppler lidar may significantly improve aviation safety and complement meteorological measurements by detecting atmospheric turbulence or volcanic ash clouds in Iceland.

How to cite: Yang, S., Petersen, G. N., von Löwis, S., and Finger, D. C.: The use of ground-based Doppler lidar in Iceland: turbulence measurement, dust detection, and the application of machine learning, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5123, https://doi.org/10.5194/egusphere-egu21-5123, 2021.

Thermodynamics
15:57–15:59
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EGU21-9297
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Highlight
Paolo Di Girolamo, Marie-Noelle Bouin, Cyrille Flamant, Donato Summa, Benedetto De Rosa, and Noemi Franco

As part of the Cevennes-Vivarais site, the University of Basilicata Raman lidar system BASIL (Di Girolamo et al., 2009, 2012, 2916) was deployed in Candillargues (Cévennes-Vivarais Southern France Lat: 43°37′ N; Long: 04°04′ E; Elev: 1 m) and operated throughout the duration of HyMeX-SOP 1 (September-November 2012), providing high-resolution and accurate measurements, both in daytime and night-time, of atmospheric temperature, water vapour mixing ratio and particle backscattering and extinction coefficient at three wavelengths.

Measurements carried out by BASIL on 28 September 2012 reveal a water vapour field characterized by a quite complex vertical structure. Reported measurements were run in the time interval between two consecutive heavy precipitation events, from 15:30 UTC on 28 September to 03:30 UTC on 29 September 2012. Throughout most of this observation period, lidar measurements reveal the presence of four distinct humidity layers.

The present research effort aims at assessing the origin and transport path of the different humidity filaments observed by BASIL on this day. The analysis approach relies on the comparison between Raman lidar measurements and MESO-NH and NOAA-HYSPLIT model simulations. Back-trajectory analyses from MESO-NH reveal that air masses ending in Candillargues at different altitudes levels are coming and are originated from different geographical regions.

The four distinct humidity layers observed by BASIL are also identified in the water vapour mixing ratio profiles collected by the air-borne DIAL LEANDRE 2 on-board of the French research aircraft ATR42. The exact correspondence, in terms of back-trajectories computation and water budget, between the humidity layers observed by BASIL and those identified in LEANDRE2 measurements has been verified based on a dedicated simulation effort.

In this research work we also try to identify the presence of dry layers and cold pools and assess their role in the genesis of the mesoscale convective systems and the heavy precipitation events observed on 29 September 2012 based on the combined use of water vapour mixing ratio and temperature profile measurements from BASIL and water vapour mixing ratio profile measurements from LEANDRE 2, again supported by MESO-NH simulations.

How to cite: Di Girolamo, P., Bouin, M.-N., Flamant, C., Summa, D., De Rosa, B., and Franco, N.: Combined use of Raman Lidar and DIAL measurements and MESO-NH model simulations for the characterization of complex water vapour field structures, their genesis and their role in the activation of Mesoscale Convective Systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9297, https://doi.org/10.5194/egusphere-egu21-9297, 2021.

15:59–16:01
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EGU21-10701
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ECS
Donato Summa, Paolo Di Girolamo, Noemi Franco, Benedetto De Rosa, Fabio Madonna, and Fabrizio Marra

The exchange processes between the Earth and the atmosphere play a crucial role in the development of the Planetary Boundary Layer (PBL). Different remote sensing techniques can provide PBL measurement with different spatial and temporal resolutions. Vertical profiles of atmospheric thermodynamic variables, i.e.  temperature and humidity, or wind speed, clouds and aerosols can be used as proxy to retrieve PBL height from active and passive remote sensing instruments. The University of BASILicata ground-based Raman Lidar system (BASIL) was deployed in the North-Western Mediterranean basin in the Cévennes-Vivarais site (Candillargues, Southern France, Lat: 43°37' N, Long: 4° 4' E, Elev: 1 m) and operated between 5 September and 5 November 2012, collecting more than 600 hours of measurements, distributed over 51 days and 19 intensive observation periods (IOPs). BASIL is capable to provide high-resolution and accurate measurements of atmospheric temperature and water vapour, both in daytime and night-time, based on the application of the rotational and vibrational Raman lidar techniques in the UV. This measurement capability makes BASIL a key instrument for the characterization of the water vapour concentration. BASIL makes use of a Nd:YAG laser source capable of emitting pulses at 355, 532 and 1064 nm, with a single pulse energy at 355nm of 500 mJ [1] .In the presented research effort, water vapour concentration was  computed and used to determine the PBL height. [2]. A dynamic index  included in the European Centre for Medium-range Weather Forecasts (ECMWF) ERA5 atmospheric reanalysis (CAPE, Friction velocity, etc.) is also considered and compared with BASIL resutls. ERA5 provides hourly data on regular latitude-longitude grids at 0.25° x 0.25° resolution at 37 pressure levels [3]. ERA5 is publicly available through the Copernicus Climate Data Store (CDS, https://cds.climate.copernicus.eu).  In order to properly carry out the comparison, the nearest ERA5 grid point to the lidar site has been considered assuming the representativeness uncertainty due to the use of the nearest grid-point comparable with other methods (e.g. kriging, bilinear interpolation, etc.). More results from this  measurement  effort will  be reported and discussed at the Conference.

Reference

[1] Di Girolamo, Paolo, De Rosa, Benedetto, Flamant, Cyrille, Summa, Donato, Bousquet, Olivier, Chazette, Patrick, Totems, Julien, Cacciani, Marco. Water vapor mixing ratio and temperature inter-comparison results in the framework of the Hydrological Cycle in the Mediterranean Experiment—Special Observation Period 1. BULLETIN OF ATMOSPHERIC SCIENCE AND TECHNOLOGY, ISSN: 2662-1495, doi: 10.1007/s42865-020-00008-3

[2] D. Summa, P. Di Girolamo, D. Stelitano, and M. Cacciani. Characterization of the planetary boundary layer height and structure by Raman lidar: comparison of different approaches  Atmos. Meas. Tech., 6, 3515–3525, 2013 www.atmos-meas-tech.net/6/3515/2013/doi:10.5194/amt-6-3515-2013

[3] Hersbach et al. The ERA5 global reanalysis Hans  https://doi.org/10.1002/qj.3803[3]

How to cite: Summa, D., Di Girolamo, P., Franco, N., De Rosa, B., Madonna, F., and Marra, F.: Characterization of the time evolution of the PBL structure and dry-layers based on the us of Raman Lidar measurements collected during HYMEX-SOP1, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10701, https://doi.org/10.5194/egusphere-egu21-10701, 2021.

16:01–16:03
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EGU21-12925
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Highlight
Andreas Behrendt, Florian Spaeth, and Volker Wulfmeyer

We will present recent measurements made with the water vapor differential absorption lidar (DIAL) of University of Hohenheim (UHOH). This scanning system has been developed in recent years for the investigation of atmospheric turbulence and land-atmosphere feedback processes.

The lidar is housed in a mobile trailer and participated in recent years in a number of national and international field campaigns. We will present examples of vertical pointing and scanning measurements, especially close to the canopy. The water vapor gradients in the surface layer are related to the latent heat flux. Thus, with such low-elevation scans, the latent heat flux distribution over different surface characteristics can be monitored, which is important to verify and improve both numerical weather forecast models and climate models.

The transmitter of the UHOH DIAL consists of a diode-pumped Nd:YAG laser which pumps a Ti:sapphire laser. The output power of this laser is up to 10 W. Two injection seeders are used to switch pulse-to-pulse between the online and offline signals. These signals are then either directly sent into the atmosphere or coupled into a fiber and guided to a transmitting telescope which is attached to the scanner unit. The receiving telescope has a primary mirror with a dimeter of 80 cm. The backscatter signals are recorded shot to shot and are typically averaged over 0.1 to 1 s.

How to cite: Behrendt, A., Spaeth, F., and Wulfmeyer, V.: Scanning 10-W Water Vapor DIAL for the Investigation of Atmospheric Turbulence and Land-Atmosphere Feedback, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12925, https://doi.org/10.5194/egusphere-egu21-12925, 2021.

16:03–16:05
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EGU21-8792
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ECS
Jonas Hamperl, Myriam Raybaut, Jean-Baptiste Dherbecourt, Patrick Chazette, Julien Totems, and Cyrille Flamant

Improved understanding of the variability underlying the distribution of stable water isotopologues in the troposphere, using both observations and modelling, has proven to be invaluable to study processes related to the hydrological cycle on a local as well as global scale. To date though, existing observation means (CRDS from ground-based or airborne platforms, passive remote sensing from space) only provide a partial picture of the complexity of the process at play due to their limited spatial or temporal coverage. On the other hand, laser active remote sensing, and in particular differential absorption lidars (DIAL) can deliver reliable, continuous, highly resolved (150 m, 10 min) profiles of H216O and HD16O in the lower troposphere, thereby providing observational insights into small scale processes such as evapotranspiration above continental surfaces and mixing in the planetary boundary layer.

Such a lidar system is currently in development (WaVIL project funded by ANR) that will operate at 1.98 µm where water isotopologues exhibit close but distinct absorption features, sensitive photodetectors are commercially available, and where pulsed laser emission over 10 mJ can be achieved using for instance parametric conversion.

In order to assess the expected instrument performances and to evaluate the potential of a ground-based system for simultaneous measurement of H216O and HD16O, we performed an error budget based on an end-to-end simulator. Lidar backscatter signals were simulated for different instrument-specific and atmospheric parameters. On the instrument side, calculations were performed for a commercial InGaAs PIN photodiode and for a state of the art low-noise HgCdTe avalanche photodiode. The sensitivity to environmental factors was investigated exemplarily for mid-latitude, arctic, and tropical environments where both vertical water vapor and aerosol variability were accounted for. Vertical profiles of aerosol extinction and backscatter coefficients were derived from the AERONET database (https://aeronet.gsfc.nasa.gov/) and extrapolated to the 2 µm spectral region, taking statistical seasonality into account. Performance simulations have been also conducted using vertical profiles derived from a field campaign where water vapor isotopologue concentrations and aerosol extinction were measured. We will outline the majority biases for such a lidar system and how statistical errors can be mitigated in a view of a forthcoming airborne DIAL instrument.

How to cite: Hamperl, J., Raybaut, M., Dherbecourt, J.-B., Chazette, P., Totems, J., and Flamant, C.: Differential absorption lidar for water vapor isotopologues in the 1.98 µm spectral region: sensitivity analysis with respect to regional atmospheric variability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8792, https://doi.org/10.5194/egusphere-egu21-8792, 2021.

16:05–16:07
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EGU21-12283
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ECS
Diego Lange, Andreas Behrendt, and Volker Wulfmeyer

We present the Atmospheric Raman Temperature and Humidity Sounder (ARTHUS), a new tool for observations in the atmospheric boundary layer and lower free troposphere during daytime and nighttime with very high resolution up to the turbulence scale, high accuracy and precision, and very short latency and illustrate its performance with new measurements examples. ARTHUS measurements resolve the strength of the inversion layer at the planetary boundary layer top, elevated lids in the free troposphere, and turbulent fluctuations in water vapor and temperature, simultaneously (Lange et al., 2019). In addition to thermodynamic variables, ARTHUS provides also independent profiles of the particle backscatter coefficient and the particle extinction coefficient from the rotational Raman signals at 355 nm with much better resolution than a conventional vibrational Raman lidar.

The observation of atmospheric moisture and temperature profiles is essential for the understanding and prediction of earth system processes. These are fundamental components of the global and regional energy and water cycles, they determine the radiative transfer through the atmosphere, and are critical for the cloud formation and precipitation (Wulfmeyer, 2015). Also, as confirmed by case studies, the assimilation of high-quality, lower tropospheric WV and T profiles results in a considerable improvement of the skill of weather forecast models particularly with respect to extreme events.

Very stable and reliable performance was demonstrated during more than 3000 hours of operation experiencing a huge variety of weather conditions, including seaborne operation during the EUREC4A campaign (Bony et al., 2017, Stevens et al., 2020). ARTHUS provides temperature profiles with resolutions of 10-60 s and 7.5-100 m vertically in the lower free troposphere. During daytime, the statistical uncertainty of the WV mixing ratio is <2 % in the lower troposphere for resolutions of 5 minutes and 100 m. Temperature statistical uncertainty is <0.5 K even up to the middle troposphere. Consequently, ARTHUS fulfills the stringent WMO breakthrough requirements on nowcasting and very short-range forecasting (see www. wmo‐sat.info/oscar/observingrequirements).

This performance serves very well the next generation of very fast rapid-update-cycle data assimilation systems. Ground-based stations and networks can be set up or extended for climate monitoring, verification of weather, climate and earth system models, data assimilation for improving weather forecasts.

References:

Bony et al., 2017, https://doi.org/10.1007/s10712-017-9428-0

Lange et al., 2019, https://doi.org/10.1029/2019GL085774

Stevens et al. 2020, submitted to ESSD

Wulfmeyer et al., 2015, doi:10.1002/2014RG000476

How to cite: Lange, D., Behrendt, A., and Wulfmeyer, V.: Compact Operational Tropospheric Water Vapor and Temperature Raman Lidar  with Turbulence Resolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12283, https://doi.org/10.5194/egusphere-egu21-12283, 2021.

16:07–16:09
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EGU21-8242
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Highlight
Julien Totems, Patrick Chazette, and Alexandre Baron

Lidars using rotational Raman backscattering to monitor the temperature profile in the low troposphere offer enticing perspectives for applications in weather prediction, as well as studies of aerosol and water vapor interactions, when deriving simultaneously relative humidity and aerosol optical properties. We describe the technical choices made during the design and calibration of the new temperature Raman channels for the mobile Weather and Aerosol Lidar (WALI), going over the sources of bias and uncertainty stemming from the different optical elements of the instrument. The impacts of interference filters and non-common-path differences between Raman channels, and their mitigation, are particularly investigated; without countermeasures, we find the theoretical magnitude of the highlighted biases can be much larger than the targeted absolute accuracy of 1°C defined by the World Meteorological Organization (WMO). Effective measurement errors are quantified using numerical end-to-end simulations and numerous radiosoundings launched close to the lidar location. Our aim is to fully discuss design choices and sources of bias which have been little reported in the literature. An application of the WALI measurements during heat wave conditions in the summer of 2020 will also be presented, and compared to ERA5 weather model reanalyses.

How to cite: Totems, J., Chazette, P., and Baron, A.: Significant sources of bias in temperature measurements by rotational Raman lidar, and mitigation in the French mobile system WALI, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8242, https://doi.org/10.5194/egusphere-egu21-8242, 2021.

Lidar Data Assimilation
16:09–16:11
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EGU21-9467
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ECS
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Highlight
Rohith Thundathil, Thomas Schwitalla, Andreas Behrendt, Diego Lange, Florian Späth, Volker Wulfmeyer, Daniel Leuenberger, Alexander Haefele, Marco Arpagaus, and Martucci Giovanni

Ground based active remote-sensing instruments have proved its potential through its high quality observations of thermodynamic profiles. In this study, thermodynamic profiles obtained from the temperature Raman lidar (TRL) and the water-vapour differential absorption lidar (DIAL) of the University of Hohenheim (UHOH) are assimilated into the Weather Research and Forecasting model data assimilation (WRFDA) system through a new forward operator for absolute humidity and mixing ratio developed in-house.
Thermodynamic DA was performed either with the deterministic 3-dimensional variational (3DVAR) DA system or with the hybrid 3DVAR-Ensemble Transform Kalman Filter (ETKF) approach. We used data of the High Definition of Clouds and Precipitation for advancing Climate Prediction (HD(CP)2 project Observation Prototype Experiment (HOPE). The WRF model was configured for a central European domain at a convection permitting resolution of 2.5 km spatial grid increment and 100 levels in the vertical with fine resolution in the planetary boundary layer (PBL). The assimilation experiments were conducted in a rapid update cycle (RUC) mode with an hourly update frequency. The hybrid 3DVAR-ETKF DA system was incorporated with an adaptive inflation scheme using a set of 10 ensemble members each with the same configuration as the previous experiments for the 3DVAR.  We will present the results of three DA experiments. In the first experiment (CONV_DA), or the control run, only assimilation of the conventional observations was carried out with 3DVAR DA. The second experiment (QT_DA) was a 3DVAR DA assimilating WVMR and temperature together in addition to the conventional dataset. The third experiment (QT_HYB_DA) assimilated WVMR and temperature together in addition to the conventional dataset with Hybrid DA.
The WVMR RMSE with respect to the WVDIAL reduced by 41 % in 3DVAR and still reduced to 51 % in QT_HYB_DA compared to CONV_DA. Although temperature RMSE with respect to TRL increased by 5 % in QT_DA, RMSE significantly reduced to 47 % in QT_HYB_DA compared to CONV_DA. The correlation between the temperature and WVMR variables in the background error covariance matrix of the 3DVAR, which is static and not flow-dependent, limited the improvement in temperature. Flow-dependency in Hybrid DA improved the error correlations.
We also present results of a collaborative effort with the Raman lidar for meteorological observation (RALMO) from the MeteoSwiss and the Atmospheric Raman Temperature and Humidity Sounder (ARTHUS) using even finer model resolution. The initial results of the new study will also be presented here.

How to cite: Thundathil, R., Schwitalla, T., Behrendt, A., Lange, D., Späth, F., Wulfmeyer, V., Leuenberger, D., Haefele, A., Arpagaus, M., and Giovanni, M.: Investigation of the impact of thermodynamic profiles of ground based lidar systems on short-range forecast skill by means of ETKF-hybrid 3DVAR data assimilation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9467, https://doi.org/10.5194/egusphere-egu21-9467, 2021.

Lidar Technique
16:11–16:13
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EGU21-8944
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ECS
Marco Di Paolantonio, Gian Luigi Liberti, and Davide Dionisi

Lidar observations are fundamental to quantitatively study the vertical distribution of atmospheric aerosols. In particular, some applications (e.g. air quality monitoring) need the description of the particulate from the ground up to the top of the atmospheric boundary layer. To correctly interpret the received lidar signal in the lowermost range, where the overlap between the telescope field of view and the laser beam is incomplete, an optimized alignment and the knowledge of the overlap function are required.

The multi-wavelength multi-telescope RMR “9-eyes” system in Rome Tor Vergata [1] has the capability to move, through electronically controlled stepper motors, the orientation of the laser beams and the 3D position of the diaphragm of the receiving optical system around the focal point of the telescopes. Taking advantage of these instrumental characteristics, a set of semi-automated tools (the mapping procedure) was developed for the optimization of the telescope/beam alignment and the estimation of the overlap function.

In this study the results of the mapping applied to a single combination of telescope-laser beam are reported. To demonstrate the effectiveness of the procedure the results were verified by comparing the whole profile of the signal and the outcome of the telecover test [2] before and after the alignment. The overlap function was estimated and the height of full overlap compared against the one obtained from a geometric model.

The proposed method gives the possibility to characterize the signal profile as a function of the position of the receiving optical system in the 3D space around the focal point. This characterization improved the accuracy of the system alignment protocol. The mapping applied to the laser beam can be used to align systems with fixed receiving geometry and, as presented, to estimate the overlap function.

 

[1] F. Congeduti, F. Marenco, P. Baldetti, and E. Vincenti, ‘The multiple-mirror lidar “9-eyes”’, J. Opt. Pure Appl. Opt., vol. 1, no. 2, pp. 185–191, Jan. 1999, doi: 10.1088/1464-4258/1/2/012.

[2] V. Freudenthaler, H. Linné, A. Chaikovski, D. Rabus, and S. Groß, ‘EARLINET lidar quality assurance tools’, Atmospheric Meas. Tech. Discuss., pp. 1–35, Jan. 2018, doi: https://doi.org/10.5194/amt-2017-395.

How to cite: Di Paolantonio, M., Liberti, G. L., and Dionisi, D.: A semi-automated procedure for the alignment and the overlap function estimation of stepper motor controlled lidars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8944, https://doi.org/10.5194/egusphere-egu21-8944, 2021.

16:13–16:15
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EGU21-14151
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ECS
Katsiaryna Cidorkina, Natalia Dorozhko, Alexander Svetashev, and Leonid Turishev

The present study is devoted to the numerical simulation and analysis of the high-intensity femtosecond LIDAR pulses propagation in the air with a special emphasis on the stimulated Raman scattering (SRS) and the stimulated Raman self-mode (SRSM) processes in optically inhomogeneous gas media.

Numerical models have been developed on the basis of a semi-classical energetic and wave theory, including a set of wave and material equations which allow simulating the gas mixtures, regular or stochastic density inhomogeneity and aerosol particles impact on the femtosecond laser pulse shape and spectrum.

The propagation of laser pulses (λ = 400, 800 nm; τ = 1 ÷ 30 fs) with positive or negative chirp was numerically investigated in pure gases: H2, N2, O2 and their typical atmospherically mixtures.   

The media density or composition (aerosol) inhomogeneity was simulated depending on the ratio between the path length (D), the size of the inhomogeneity (l) and the mean wavelength of pulse spectrum (λ). For D >> l the inhomogeneity impact was considered as a stochastic, while in the case of D < l the inhomogeneity was simulated having a constant gradient along the pulse track.      

For vertical sounding tracks the real atmospheric air density profiles were used.

Aerosol density and size fluctuations were estimated as 5÷30% to the mean value.

In model testing regime the SRS and SRMS modes of the femtosecond laser pulse propagation for tracks of up to 100 m have been calculated for investigating the dynamics of the pulse shape, spectrum and energy change under different initial conditions.

The SRMS mode for 10, 14 and 20 fs laser pulses with energy areas of 3π, 2π, π, π/100 was numerically investigated in different gas and aerosol compositions for tracks of βz = 0.5 ÷ 20, where z is the space coordinate and β – the inverse value of Raman self-scattering defined by the media. 

The results obtained show that the dynamics of pulse propagation in SRMS mode is nonlinear in the pulse shape and spectrum. Moreover, the SRMS mode having a resonance character for 2π-pulses may be misaligned as well as modulated by the inhomogeneity of the medium.

How to cite: Cidorkina, K., Dorozhko, N., Svetashev, A., and Turishev, L.: Femtosecond Laser Pulses Propagation in the inhomogeneous Gas Media, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14151, https://doi.org/10.5194/egusphere-egu21-14151, 2021.

16:15–16:17
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EGU21-7500
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ECS
Iskander Gazizov, Sergei Zenevich, Oleg Benderov, and Alexander Rodin

We present a concept of near-infrared FMCW lidar for real-time low-resolution imaging velocimetry and range finding of moving objects. One of the problems this instrument to challenge is the detection of unmanned aerial vehicles in an urban environment. The use of a lidar-based system is either in the detection of the object itself or of the wingtip vortices generated by rotating blades. A significant drawback of typical wind lidar is the long measurement time associated with the need to scan the area of ​​interest, therefore we propose an 8x2 matrix of receivers to reduce the total scan time. The main feature of the instrument is the use of commercially available components, including DFB lasers and single-mode fiber for the optical circuit, which can significantly reduce the cost of the device, as well as development time. Data processing and laser control are handled by the FPGA. The characteristics of the multichannel lidar are estimated based on ongoing testing of the single-channel prototype.

Acknowledgements

This work has been supported by the Russian Foundation for Basic Research grants #19-29-06104

How to cite: Gazizov, I., Zenevich, S., Benderov, O., and Rodin, A.: Multichannel FMCW lidar for imaging velocimetry and range finding, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7500, https://doi.org/10.5194/egusphere-egu21-7500, 2021.

Satellite Lidar
16:17–16:19
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EGU21-10789
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ECS
Noemi Franco, Paolo Di Girolamo, Donato Summa, Benedetto De Rosa, Andreas Behrendt, and Adolfo Comerón

An end-to-end model has been developed in order to simulate the expected performance of a space-borne Raman Lidar, with a specific focus on the Atmospheric Thermodynamics LidAr in Space – ATLAS proposed as a “mission concept” to the ESA in the frame of the “Earth Explorer-11 Mission Ideas” Call. The numerical model includes a forward module, which simulates the lidar signals with their statistical uncertainty, and a retrieval module able to provide vertical profiles of atmospheric water vapour mixing ratio and temperature based on the analyses of the simulated signals. Specifically, the forward module simulates the interaction mechanisms of laser radiation with the atmospheric constituents and the behavior of all the devices present in the experimental system(telescope, optical reflecting and transmitting components, avalanche photodiodes, ACCDs). An analytical expression of the lidar equation for the water vapour and molecular nitrogen roto-vibrational Raman signals and the pure rotational Raman signals from molecular oxygen and nitrogen is used. The analytically computed signals are perturbed by simulating their shot-noise through Poisson statistics. Perturbed signals thus take into account the fluctuations in the number of photons reaching the detector over a certain time interval. The simulator also provides an estimation of the background due to the solar contribution. Daylight background includes three distinct terms: a cloud-free atmospheric contribution, a surface contribution and a cloud contribution[1]. Background is calculated as a function of the solar zenith angle. In order to better estimatethe background contribution, an integration on slant path is performed instead of a classical parallel-planes approximation. The proposed numerical model allows to better simulate solar background for high solar zenith angles, even higher than 90 degrees. Signals simulated through the forward model are then fed into the retrieval module. A background subtraction scheme is used to remove the solar contribution and a vertical averaging is performed to smooth the signals. Based on the application of the roto-vibrational Raman lidar technique, the vertical profile of atmospheric water vapour mixing ratio is obtained from the power ratio of the water vapour to a reference signal, such as molecular nitrogen roto-vibrational Raman signal or an alternative temperature-independent reference signal. A vertical profile of temperature is then obtained through the ratio of high-to-low quantum number rotational Raman signals by the application of the pure rotational Raman lidar technique. Both atmospheric water vapour mixing ratio and temperature measurements require the determination of calibration constants, which can be obtained from the comparison with simultaneous and co-located measurements from a different sensor [2]. The simulator finally provides statistical (RMS) and systematic (bias) uncertainties. Estimates are provided in terms of percentage and absolute (g/kg) uncertainty for water vapour mixing ratio measurements and in terms of absolute uncertainty (K) for temperature measurements.

 References

1 - P.Di Girolamo et al., "Spaceborne profiling of atmospheric temperature and particle extinction with pure rotational Raman lidar and of relative humidity in combination with differential absorption lidar: performance simulations"Appl.Opt. 45, 2474-2494(2006)

2 - P.Di Girolamo et al., "Space-borne profiling of atmospheric thermodynamic variables with Raman lidar: performance simulations,"Opt.Express 26, 8125-8161(2018)

How to cite: Franco, N., Di Girolamo, P., Summa, D., De Rosa, B., Behrendt, A., and Comerón, A.: End-to-end Simulator of a space-borne Raman Lidar for the thermodynamic profiling of the atmosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10789, https://doi.org/10.5194/egusphere-egu21-10789, 2021.

16:19–17:00