GI4.2

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<-50^oC). 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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.

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.