Displays

The National Center for Atmospheric Research and Montana State University have developed a 5-unit ground-based test network of MicroPulse Differential Absorption Lidar (MPD) instruments to continuously measure high-vertical-resolution water vapor profiles in the lower atmosphere. These diode-laser-based instruments are accurate, low-cost, operate unattended, do not require external calibration, and eye-safe – all key features to enable larger 'national-scale' networks needed to characterize atmospheric moisture variability, which influences important processes related to weather and climate.  Enhancements to the water vapor MPD architecture have been recently developed that enable quantitative aerosol measurements and atmospheric temperature profiling by simultaneously measuring O2 absorption and aerosol backscatter ratio. This combination of measurements allows for the first DIAL measurements of atmospheric temperature with useful accuracy. The MPD has been demonstrated to provide continuous, range-resolved measurements of atmospheric thermodynamic variables, water vapor and temperature, and quantitative measurements of aerosol scattering from a high spectral resolution (HSRL) channel.  Thus, a network of these instruments shows promise to provide atmospheric profiling capabilities needed by both the climate and weather forecasting research communities.

How to cite: Spuler, S., Stillwell, R., Hayman, M., Weckwerth, T., and Repasky, K.: MicroPulse DIAL (MPD) ground-based network for Thermodynamic Profiling in the Lower Troposphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10310, https://doi.org/10.5194/egusphere-egu2020-10310, 2020.

Here we present the new Atmospheric Raman Temperature and Humidity Sounder (ARTHUS), an exceptional tool for observations in the atmospheric boundary layer during daytime and nighttime with a very short latency. ARTHUS measurements resolve the strength of the inversion layer at the planetary boundary layer top, elevated lids in the free troposphere during daytime and nighttime, and turbulent fluctuations in water vapor and temperature, simultaneously, also during daytime.

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 clouds formation and precipitation. Also, it is expected that the assimilation of high-quality, lower tropospheric WV and T profiles will result in a considerable improvement of the skill of weather forecast models particularly with respect to extreme events.

Very stable and reliable performance was demonstrably achieved during more than 2500 hours of operations time experiencing a huge variety of weather conditions. 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. ARTHUS fulfills the stringent WMO breakthrough requirements on nowcasting and very short-range forecasting.

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.

How to cite: Lange Vega, D., Behrendt, A., and Wulfmeyer, V.: Compact Operational Tropospheric Water Vapor and Temperature Raman Lidar with Turbulence Resolution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12164, https://doi.org/10.5194/egusphere-egu2020-12164, 2020.

In June 2019, the Lacustrine-Water vApor Isotope inVentory Experiment (L-WAIVE) has been performed in the southern part of the Annecy lake (45°47' N, 6°12' E). The field campaign motivation is to bring a better comprehension on the evaporation processes above Alpine lakes influencing, along with orography, the complex atmospheric structuration. In particular, this two-week field campaign has involved the meteorological Raman lidar WALI (Weather and Aerosol LIdar). An ultra-light aircraft carrying a meteorological probe and a particle sizer performed several vertical profiles above the ground-based Raman lidar with a vertical resolution between 50 and 100 m for flights operated from the ground level (~0.5 km above the mean sea level (AMSL)) and ~4 km AMSL.

This setup is an opportunity to experimentally assess the instrumental errors on both the temperature and the water vapour mixing ratio profiles derived from the ground-based lidar. The methodology used to calculate the error budget will be presented. It will take into account the different types of statistical noises associated with the lidar measurement. In particular, the importance of the spectral filtration in the accuracy of the results will be discussed. The uncertainties associated with the lidar calibration procedure will be quantified. Following this detailed study, the first results of relative humidity will be presented, taking into account the associated error bars.

How to cite: Baron, A., Chazette, P., and Totems, J.: Relative humidity fields in the Annecy Alpine valley observed by Ro-Vibrational Raman lidar in the framework of L-WAIVE, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17672, https://doi.org/10.5194/egusphere-egu2020-17672, 2020.

Tropospheric aerosols  are a fundamental component of the Earth’s radiation budget. In order to properly estimate their direct and indirect effect, accurate measurements of aerosol size and microphysical properties are required.A limited number of techniques are presently available and capable to provide these measurements.

Multi-wavelength Raman lidars Raman lidars have strong potential. However,theireffectiveness and reliability of need to be assessed and verified against independent measurements.

This abstract reports measurements that were carried out by the Raman lidar system BASIL in the frame of the Hydrological Cycle in the Mediterranean Experiment – Special Observation Period 1 (HyMeX-SOP1).The considered dataset represents a good opportunity to verify the quality of retrievals in terms of size and microphysical properties obtained from multi-wavelength Raman lidars.

A specific case study was selected revealing the presence of variable aerosol properties at different altitudes. Specifically, Raman lidar measurements on 02 October 2012 show the presence of two distinct aerosol layers, a lower one extending up to ~3 km and an upper one extending from 3.5 km to 4.7 km. Aerosol and size microphysical properties are determined from multi-wavelength measurements of particle backscattering and extinction profiles based on the application of  a retrieval scheme which employs Tikhonov’s inversion with regularization. Inversion results suggest a size distribution with the presence, in both the lower and upper aerosol layer, of two particle modes (a fine mode, with a radius of ~0.2 mm, and a coarse mode, with radii in the range 2-4 mm), volume concentration values of 2-4 mm³cm^-3and effective radii in the  range 0.2-0.6 mm.

This effort benefited from the dedicated flights of the French research aircraft ATR42, equipped with a variety of in situ sensors for measuring aerosol/cloud size and microphysical properties. Aerosol size and microphysical properties retrieved from multi-wavelength Raman lidar measurements were compared with simultaneous and co-located in-situ measurements.

How to cite: De Rosa, B., Di Girolamo, P., and Summa, D.: Determination of aerosol size and microphiysical proprierties based on multi-wavelength raman lidar measurements in the framework of HyMeX-SOP1, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17218, https://doi.org/10.5194/egusphere-egu2020-17218, 2020.

In this study we illustrate the development of a rain and snow masking algorithm applied to the National  Aeronautics and Space Administration (NASA) Micro-Pulse lidar network (MPLNET) observations. The algorithm, once operationally implemented, will deliver in Near Real Time (latency <1.5 hr) the rain and snow masking variables. The products will be publicly available on MPLNET website as part of the new Version 3 release. The methodology, based on image processing techniques, can detect only light to moderate rainfall and snowfall events (defined by intensity and duration) becasue of laser attenuation.  The main underlying technique consists in applying the morphological filters on the volume depolarization ratio composite image to identify  squared shapes under the cloud bases that corresponding to the precipitation. Results from the algorithm, besides filling a gap in precipitation and virga detection by radars, are of particular interest for the scientific community because will help to fully characterize the aerosol cycle, from emission to deposition, as precipitation is a crucial meteorological phenomena accelerating the atmospheric aerosol removal through the wet scavenging effect. As an example, in this study we prove, for the first time to our knowledge, how rain detection from ground-based lidar observations are effective in showing a strong negative correlation between the Aerosol Optical Depth (AOD) and precipitation.

How to cite: Lolli, S., Vivone, G., Welton, E. J., Lewis, J. R., Sicard, M., Comeron, A., and Pappalardo, G.: NASA new V3 Micro-Pulse Lidar Network Rain and Snow masking algorithm application: Aerosol wet deposition., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20573, https://doi.org/10.5194/egusphere-egu2020-20573, 2020.

Frequency Modulation (FM) is a well-known technology but was never used in Continuous Wave (CW) Wind Lidars. The reason is because range and velocity can only be resolved for single hard targets like vehicles but not for dispersed targets like atmospheric aerosol. Here we present a FMCW system that uses the established focusing method for ranging and in addition a frequency modulated transmit signal. The origin of the scattered radiation is localized by focusing in a limited measuring volume. Because of this – by applying FM – the unavoidable range-velocity ambiguity of CW Wind Lidars can be resolved similarly as for hard targets. This is particularly important in conditions with fog or low hanging clouds (coastal or mountainous areas) or distant moving obstacles behind the measuring volume, or generally spoken in cases with strong gradients of the backscatter cross section. While out-of-focus contributions is a well-known concern of CW Lidar, we will show examples from FMCW field measurements first time revealing quantitatively the range uncertainty based on focus distance. Not surprisingly this uncertainty increases with height range, where the focus becomes less well-defined. Furthermore, the FMCW Wind Lidar allows also to correct uncertainties of mechanical focus distance setting. This is also mainly important at larger ranges where the focus distance becomes very sensitive to mechanical tolerances. Moreover, auxiliary measurements of wind direction, that are needed by CW systems for removing the sign-ambiguity of velocity, are obsolete, and there is no lower threshold of measurable windspeed. As a consequence wind measurements are feasible in street canyons, forest clearings and any other environment with strong vertical gradients.

How to cite: Peters, G. and Markmann, P.: Removal of range uncertainty of CW Wind Lidar by frequency modulation., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2915, https://doi.org/10.5194/egusphere-egu2020-2915, 2020.

In the Arctic areas the influence of climate change is being felt at a higher degree than elsewhere. Enabling a better understanding of the environment in region is of high importance. Clouds play a significant role in the energy budget and the hydrological cycle of the Earth’s atmosphere system. In order to provide insights into Arctic cloud processes for Arctic cloud-climate studies, the field campaign PaCE (Pallas Cloud Experiment) was organized during autumn and winter 2019; the campaign was focusing on aerosol and cloud vertical profiling using in-situ and remote sensing techniques.

During the campaign, a ground-based multi-wavelength Raman polarization lidar Polly^XT performed continuous measurements from September to December 2019, at the Kenttärova station (N 67°59’14”, E 24°14’35”, 347 m above sea level) at Pallas, in the northern Finland. This is a background station surrounded by the forest, where the atmosphere is quite clean. Cloud vertical structures and optical properties have been determined from lidar analysis. During day-time, the Klett method is applied to retrieve the vertical profiles of cloud extinction and backscatter coefficient at three wavelengths (355 nm, 532 nm and 1064 nm). During night-time, the standard Raman method is used to provide additional lidar ratio profiles at 355 nm and 532 nm. The actual linear depolarization ratio at two wavelengths (355 nm and 532 nm) are also retrieved. With water vapor channel at 407 nm, the relative humidity profile are also available for received signal with good signal-to-noise ratio. The combined use of near and far field telescopes provides reliable vertical profiles of optical properties from 0.25 km to 10 km above ground level. The temperature and thickness dependencies on optical properties have also been studied in detail. Geometrical properties of cloud are retrieved using both lidar and ceilometer, statistic values of cloud height, and thickness are shown.

How to cite: Shang, X., Komppula, M., Giannakaki, E., Bohlmann, S., Filioglou, M., and Brus, D.: Optical and geometrical properties of Arctic clouds over northern Finland during PaCE campaign in 2019, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17951, https://doi.org/10.5194/egusphere-egu2020-17951, 2020.

Long-term data on clouds and aerosols are of critical importance to accurately model climate change. In particular, CALIPSO-like LIDAR missions give access to data on clouds height, distribution, optical depths… as well as information on aerosol types and concentration.

In this context, BLISS (Backscattering Lidar Signal Simulator) has been developed by CNES and Thales Services to simulate the return signal received by a backscattering space-borne LIDAR and the associated data processing (level 0 to level 2), in order to perform mission dimensioning studies as well as sensitivity studies on instrument or geophysical parameters. Given a specific input scene, it provides the vertical profiles of clouds and aerosol actually in the atmosphere as seen by the LIDAR and can also provide a profile of the first few meters inside the oceans – if any – thus representing the backscattering of light by particles as plankton.  It has already especially been used on MESCAL phase 0 and its outputs have been compared with other existing LIDAR codes (like the one developed by NASA LARC).

BLISS user interface, its different modules and an associated end-to-end simulation will be presented.

How to cite: Schmisser, R., Chinaud, J., and Galaup, P.: BLISS: a backscattering space-borne LIDAR simulator, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2207, https://doi.org/10.5194/egusphere-egu2020-2207, 2020.

Dust lidar ratios are retrieved by a synergetic use of CALIOP and MODIS products for 5 years from 2007 to 2011. The CALIOP level 1 total attenuated backscatter data is used for the retrieval and the CALIOP level 2 aerosol profile product is used to determine dust layers. Quality assured (QA > 1 for dark target ocean, QA = 3 for deep blue land) aerosol optical depth (AOD) data from the MODIS level 2 aerosol product is used as constraint. MODIS AOD retrievals and CALIOP attenuated backscatter profiles closer than 10 km from the center of MODIS pixel are defined as collocated measurements. Clouds are screened out for both CALIOP and MODIS. The retrieval is performed for the whole column of the atmosphere from 30 km to the surface adopting a constant lidar ratio of 30 sr for aerosols of clear air above the detected layers. The retrieved dust lidar ratios show a log-normal distribution with mean (median) values of 39.5 ± 16.8 (38.1) sr and 46.6 ± 36.3 (39.2) sr for ocean and land, respectively. The mean values are comparable to the value of 44 sr currently used in the CALIOP level 2 aerosol algorithm but the median values are relatively lower. There is a distinct regional variation in the retrieved dust lidar ratios. Dust lidar ratio is larger for the Saharan Desert (49.5 ± 36.8 sr) than the Arabian Desert (42.5 ± 26.2 sr), which is consistent with many previous studies. Dust aerosols transported to the Mediterranean Sea (44.4 ± 15.9 sr), Mid Atlantic (40.3 ± 12.4 sr) and Arabian Sea (37.5 ± 12.1 sr) show lower values compared with their source regions. An aging process of the long-range transported dust to remote ocean may be responsible for low lidar ratios. Dust lidar ratio over ocean in East Asia is 41.8 ± 27.6 sr is comparable with previous studies. Over Taklamakan and Gobi Deserts region the retrieved dust lidar ratios (35.5 ± 31.1 sr) show low values but still comparable with previous studies. Dust lidar ratios for Australia (35.4 ± 34.4 sr) are also relatively low compared with other regions. Although the mean AOD difference between CALIOP and MODIS is small (close to zero), the distribution of the AOD difference shows that the CALIOP AOD is biased low. However, when including clear air AOD for CALIOP, AODs from the two sensors become more comparable. A conclusion that can be drawn from this is that retrieving only for the detected layers in the CALIOP algorithm is one of the major reasons for lower AODs for CALIOP than MODIS. Lidar ratios retrieved in this study are strongly affected by MODIS AOD, because it is used as a constraint for the retrieval.

How to cite: Kim, S.-W., Kim, M.-H., and Omar, A.: Dust lidar ratios retrieved from the space-borne CALIOP measurements using the MODIS AOD as a constraint, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2279, https://doi.org/10.5194/egusphere-egu2020-2279, 2020.

The spatial distribution of aerosol particles is relevant for studies on the radiation budget, for the verification of chemistry transport models, or for air quality studies just to name a few. As the distribution is highly variable the requirements to measurements are very demanding. As a consequence it is often assumed that the aerosol distribution is "relatively homogeneous", i.e., measurements at one site are representative for a larger area.

By exploiting 2 years of measurements from 12 ceilometers located in the area of Munich and Berlin, Germany, we have investigated the spatial differences between locations separated between 3~km and 50~km. For this purpose we have used the mixing layer height (MLH), a quantity often used when the vertical aerosol distribution should be described by a single parameter. The MLH was determined by the COBOLT-algorithm (Geiß et al., 2017). It was found that the MLHs at different locations inside the two cities are highly correlated and agree within a few tens of meters. However, the maximum extension of the mixing layer from April to September was found to be significantly larger in Berlin compared to Munich.

Geiß, A., Wiegner, M., Bonn, B., Schäfer, K., Forkel, R., von Schneidemesser, E., Münkel, C., Chan, K. L., and Nothard, R. (2017): Mixing layer height as an indicator for urban air quality?  Atmos. Meas. Tech., 10, 2969-2988, https://doi.org/10.5194/amt-10-2969-2017, 2017.

How to cite: Wiegner, M., Geiß, A., Mattis, I., Meier, F., and Ruhtz, T.: Mesoscale variability of the aerosol distribution as determined from ceilometer measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4652, https://doi.org/10.5194/egusphere-egu2020-4652, 2020.

The L-Waive campaign took place over the Annecy lake in France in June 2019. In an effort to better understand the atmospheric structure and the water cycle over lakes, it involved an airborne Rayleigh-Mie lidar, ground-based Raman & wind lidars, as well as airborne measurements of water vapor and its isotopes, and aerosol particle size distribution.

This represented a unique opportunity to study the vertical structuring of the troposphere, which is poorly documented in mountainous regions and particularly in the Alpine valleys. Regular radio-soundings are generally not representative of the low atmospheric layers encountered above the valleys, which are influenced by relief winds. Lidar observations in Alpine valleys have been made in the past using Rayleigh-Mie instrumentation, but during L-WAIVE the ground-based Raman lidar WALI also measured the meteorological parameters of water vapour and temperature. The airborne lidar ALIAS carried by an ultra-lght aircraft complemented aerosol measurements, in a coupled top-down inversion approach, highlighting the influence of mountains on different vertical and horizontal scales.

This setup was operational when an exceptional dust transport event overpassed south-eastern France on June 14^th, 2019. The origin of this event was shown by HYSPLIT back-trajectories and thermal anomalies computed from SEVIRI as laying in the Grand Erg Occidental, Algeria. An aerosol optical thickness up to 0.8 at 355 nm was measured by the lidar on this occasion, and the instrumental lidar synergy allows to completely characterize the dust plumes in terms of particle extinction, depolarization, relative humidity, and airmass velocities and potential temperature. The dust-perturbated atmosphere will be compared to the background situation where only pollution aerosols are present. The effect of the mountain aerology on the transport will thus be discussed.

How to cite: Totems, J., Chazette, P., Baron, A., and Dieudonné, E.: Top-down lidar characterization of exceptional dust transport event above the Annecy lake during L-WAIVE in June 2019, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7637, https://doi.org/10.5194/egusphere-egu2020-7637, 2020.

The South China Sea is the third largest inland sea in the world, with unique geographical and climatic conditions, and great economic importance. Observation of aerosols over this region is needed to understand their role in cloud, radiation, and ocean primary production. While the optical properties of marine aerosols over the South China Sea have been studied using solar photometers, there are no lidar studies for this region that the authors know of in publicly accessible scientific literature.

To test the viability of shipborne lidar for aerosol measurement over the South China Sea, a shipborne micro-pulse lidar (Mini-MPL) was used to measure aerosol extinction coefficient in the northern region of the South China Sea over a period of one month from 9th August to 7th September, 2016, along the cruise path of a research vessel. The measurements were inverted to obtain vertical profiles of aerosol extinction coefficient, depolarization ratio, and atmospheric boundary layer height using Mie Theory and the Fernald method. Aerosols were found to be concentrated low in the atmosphere, with more than 73% of total extinction below 2 km and almost no aerosol above 3.5 km. Maximum extinction values in coastal areas were generally about double of values in offshore areas. The aerosol concentration was lower in the northwest side of the South China Sea compared to the northeast side, a pattern that may due to advection by the prevailing summer southwesterly winds. Vertical profiles and back-trajectory calculations indicated vertical and horizontal layering of aerosols from different terrestrial sources. The mean depolarization ratio of the aerosols along the cruise was 0.042. Atmospheric boundary layer height along the cruise was average 653.2 m, with a diurnal cycle reaching its mean maximum of 1041.2 m at 12:00, and its mean minimum of 450.0 m at 20:00.

How to cite: Li, Y.: Micro-pulse Lidar Measurements in South China Sea Expedition , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12642, https://doi.org/10.5194/egusphere-egu2020-12642, 2020.

Depolarization ratio is highly valuable in lidar-based aerosol classification and can be used to quantify the contributions of different aerosol types to elevated layers [1]. Typically, aerosol particle depolarization ratio is determined at relatively short wavelengths of 355 nm and/or 532 nm, though some multi-wavelength case studies including 1064 nm have shown strong spectral dependency [2,3]. Here, we demonstrate that Halo Photonics Stream Line Doppler lidars can be used to retrieve aerosol particle depolarization ratio at 1.5 µm wavelength.

We utilize measurements in April-May 2017 at Limassol, Cyprus to compare the Halo 1.5 µm aerosol particle depolarization ratio with Polly XT aerosol particle depolarization ratio. Recently developed post-processing [4] enables retrieving weak signals (as low as -32 dB) with the Halo Doppler lidar. At Limassol, we were able to determine particle depolarization ratio for several cases of mineral dust up to 3 km above ground. Generally, particle depolarization ratio for mineral dust at 1.5 µm appears higher than at shorter wavelengths of 355 nm and 532 nm retrieved by Polly XT. Overall, our results indicate that Halo Doppler lidars can add another wavelength at 1.5 µm to studies on the spectral dependency of aerosol depolarization ratio, at least in the lowest 2-3 km above ground.

[1] Mamouri, R.-E. and Ansmann, A.: Potential of polarization/Raman lidar to separate fine dust, coarse dust, maritime, and anthropogenic aerosol profiles, Atmos. Meas. Tech., 10, 3403-3427, https://doi.org/10.5194/amt-10-3403-2017, 2017.

[2] Burton, S. P., Hair, J. W., Kahnert, M., Ferrare, R. A., Hostetler, C. A., Cook, A. L., Harper, D. B., Berkoff, T. A., Seaman, S. T., Collins, J. E., Fenn, M. A. and Rogers, R. R.: Observations of the spectral dependence of linear particle depolarization ratio of aerosols using NASA Langley airborne High Spectral Resolution Lidar, Atmos. Chem. Phys., 15, 13453–13473, doi:10.5194/acp-15-13453-2015, 2015.

[3] Haarig, M., Ansmann, A., Baars, H., Jimenez, C., Veselovskii, I., Engelmann, R. and Althausen, D.: Depolarization and lidar ratios at 355, 532, and 1064 nm and microphysical properties of aged tropospheric and stratospheric Canadian wildfire smoke, Atmos. Chem. Phys., 18, 11847–11861, doi:10.5194/acp-18-11847-2018, 2018.

[4] Vakkari, V., Manninen, A. J., O’Connor, E. J., Schween, J. H., van Zyl, P. G. and Marinou, E.: A novel post-processing algorithm for Halo Doppler lidars, Atmos. Meas. Tech., 12(2), 839–852, doi:10.5194/amt-12-839-2019, 2019.

How to cite: Vakkari, V., O'Connor, E., Baars, H., and Bühl, J.: Comparing Halo Doppler lidar depolarization ratio with PollyXT, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19164, https://doi.org/10.5194/egusphere-egu2020-19164, 2020.

Ceilometers are effective instruments to study atmospheric profiles. They are primarily designed to study cloud base height however are widely used to study aerosol optical properties profiles, aerosol backscatter or extinction coefficients or just atmospheric layering. In this work we utilized statistics of aerosol layers in free troposphere to explain differences between measured and modelled UV radiation at Raciborz station in southern Poland.

Raciborz is a town in southern Poland, close to the Czech Republic border. This area is affected by local urban and industrial pollutions from urban area of Silesia in South Western Poland and North Eastern Czech Republic. Remote locations of aerosols may also play important role in UV radiation modification. The observatory in Raciborz is equipped with CHM-15k Nimbus ceilometer, triple Sun-Sky-Lunar CIMEL ceilometer, and Kipp & Zonen UVS-E-T biometer.

Series of erythema dose rates were compared to that modelled by Tropospheric Ultraviolet-Visible (TUV) radiation transfer model. We used satellite (OMI) ozone, aerosol columnar properties (optical thickness at 340 nm, Angstrom exponent for 340-440nm range as well as single scattering albedo and asymmetry parameter at 440 nm) measured by CIMEL photometer as model input values. The model/observations differences are within +/- 5% range for 90% of measured doses during cloud free conditions. The median of model/observations ratio differences is 0.994. To explain revealed ratio variability a statistical, regression model was developed. A random forest approach applied to normalized erythema doses explained about 52% of model/observations ratio differences by aerosol characteristics in free troposphere.

Aerosol characteristics provided as statistical model input are: mean altitude of aerosol’s layer base and top, geometrical thickness of all layers and sum of aerosol layer backscatter intensity (in arbitral units) normalized by layer geometrical thickness. Aerosol layers are found throughout the year with the highest frequency in August (about 80%  days with at least one layer) and the lowest in November (about 10% days). For days with layers, the mean number of  the layers per day is less variable usually 2-3 layers in one day. The mean depth of the layer  is  larger in summer (1.3 km) than in winter (0.8 km) but the life time of the layer is similar of about 7-8 hours in both periods.

Acknowledgements

This work was supported by Polish National Science Center under grant no. 2017/25/B/ST10/01650.

How to cite: Pietruczuk, A., Krzyscin, J., Szkop, A., and Fernandes, A.: Aerosol layering in free troposphere, its impact on modification of the UV irradiation over industrial site in southern Poland , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4905, https://doi.org/10.5194/egusphere-egu2020-4905, 2020.

Remote monitoring of industrial emissions into the atmosphere, the hazardous gases near landfills and incinerators, monitoring the presence of gas leaks in manufactures today play a huge role for human being. And this role will increase in the near future, because of aggravated ecological problems, business interests etc.

We present an instrument concept for lidar monitoring of industrial atmospheric pollution, based on the commonly used technique for tunable diode laser spectroscopy (TDLS), termed wavelength modulation spectroscopy (WMS). This instrument is being developed to determine the presence of technogenic pollution of atmospheric air in concentrations that pose a danger to nature, as well as human life and health. At the first stage, methane was chosen as the object of interest.

For remote measurement of atmospheric impurities, we propose to use a near-infrared diode laser (DL) operating in continuous mode with sinusoidal modulation of the injection current with a frequency of ~100 kHz. In the absence of molecules absorbing laser radiation, the photodetector detects radiation only at the modulation frequency f. In the presence of absorbing molecules, a signal appears at higher harmonics (2f, 3f). If the laser radiation is tuned to the center of the absorption line and modulated in the vicinity of this value, then the received signal at the first harmonic 1f is proportional to the total intensity of the detected radiation, and the 2f signal is proportional to the intensity absorbed by the molecules of the measured gas. Thus, the amplitude ratio of 2f signal and 1f signal characterizes the absorption of the measured gas and allows calculating of this gas concentration. Furthermore in remote measurements of laser radiation scattered from the surface, the total intensity of the detected radiation can vary by an order of magnitude, therefore, normalization of the 2f signal to the 1f signal is necessary.

The correct operation of this technique require that the radiation frequency of the DL should be stabilized at the center of the absorbing line with high accuracy: ~1% of the absorption line width, which at atmospheric pressure is ~10^-3 cm^-1. Such high stability of the laser radiation frequency is achievable using the 3f signal, which passes through zero in the center of the line.

During the implementation of the project a compact and lightweight instrument, that can be installed on the unmanned aerial vehicles (UAVs) to control the emission of harmful gases at industrial sites, landfills, will be created. Currently, such instrument using other operation algorithms have a mass of 10-20 kg and are usually installed on manned helicopters. The installation of such instrument on the UAV will greatly simplify and reduce the cost of industrial pollution monitoring. First tests of our instrument are planned on the second half of 2020.

Acknowledgments

This work has been supported by the Russian Foundation for Basic Research [Grant No.18-29-24204].

How to cite: Meshcherinov, V., Spiridonov, M., Kazakov, V., Gazizov, I., and Rodin, A.: The instrument for lidar infrared remote measurement of industrial pollution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5949, https://doi.org/10.5194/egusphere-egu2020-5949, 2020.

Predicting air pollution events in the low atmosphere over megacities requires a thorough understanding of the tropospheric dynamics and chemical processes, involving, notably, continuous and accurate determination of the boundary layer height (BLH). Through intensive observations experimented over Beijing (China) and an exhaustive evaluation of existing algorithms applied to the BLH determination, persistent critical limitations are noticed, in particular during polluted episodes. Basically, under weak thermal convection with high aerosol loading, none of the retrieval algorithms is able to fully capture the diurnal cycle of the BLH due to insufficient vertical mixing of pollutants in the boundary layer associated with the impact of gravity waves on the tropospheric structure. Consequently, a new approach based on gravity wave theory (the cubic root gradient method: CRGM) is developed to overcome such weakness and accurately reproduce the fluctuations of the BLH under various atmospheric pollution conditions. Comprehensive evaluation of CRGM highlights its high performance in determining BLH from lidar. In comparison with the existing retrieval algorithms, CRGM potentially reduces related computational uncertainties and errors from BLH determination (strong increase of correlation coefficient from 0.44 to 0.91 and significant decreases of the root mean square error from 643 to 142 m). Such a newly developed technique is undoubtedly expected to contribute to improving the accuracy of air quality modeling and forecasting systems.

How to cite: Yang, T., wang, Z., zhang, W., Gbaguidi, A., and Sugimoto, N.: Boundary layer height determination from lidar for improving air pollution episode modeling: development of new algorithm and evaluation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20917, https://doi.org/10.5194/egusphere-egu2020-20917, 2020.

One weakness of today's weather and climate models is the inaccurate representation and parameterization of the boundary layer processes and land-atmosphere (L-A) feedback. In order to investigate these processes, scanning lidar systems allow the observation not only of wind with Doppler lidar but also of humidity and temperature. It is expected that advances in the understanding of LA feedback and boundary-layer exchange will significantly contribute to better simulations of clouds and precipitation on all temporal and spatial scales.

In this contribution, we present recent thermodynamic measurements in the surface layer, atmospheric boundary layer and free troposphere with very high resolution achieved during several field campaigns like the Land-Atmosphere Feedback Experiment (LAFE) in 2017, ScaleX in 2019, EUREC4A in 2020, and at the Land-Atmosphere Feedback Observatory (LAFO) in 2020.

University of Hohenheim (UHOH) operates besides two scanning Doppler lidars (HALO Photonics StreamlineXR), three lidars for thermodynamic profiling which have been developed within the last 15 years by the Institute of Physics and Meteorology itself. These are two scanning lidar systems which are semi-automated and a fully-automated vertical pointing lidar system.

The water vapor differential absorption lidar (DIAL) of UHOH is a mobile system with a laser power of up to 10 W at 818 nm with a pulse repetition rate of 300 Hz. The receiver consists of an 80-cm telescope. The raw resolution of the atmospheric backscatter signals is 15 m and single shot. The resolution of the data product, the water vapor number density or absolute humidity, is typically 1 to 10 s and 40 to 200 m.

The UHOH Rotational Raman Lidar measures temperature and water vapor mixing ratio. Also this system is mobile. So far, we used as transmitter a flash-lamp-pumped Nd:YAG laser with 12 W at 355 nm at 50 Hz. This laser is currently being exchanged against a similar laser with 20 W at the same pulse repetition frequency. The light backscattered from the atmosphere is received with a 40 cm telescope. Four channels detect the elastic backscatter signal, two rotational Raman signals, and the water vapor Raman signal. The signal intensities are detected in analog and photon counting mode with raw resolutions of 7.5 m and 10 s. Typical resolutions of the data products are 100 m and 10 s.

A compact and automated further development of this system, ARTHUS for Atmospheric Raman Temperature and Humidity Sounder, uses already this powerful diode-pumped laser transmitter (20 W at 355 nm, 200 Hz).

Measurement examples of all instruments will be presented and an outlook to future developments will be discussed.

How to cite: Behrendt, A., Lange, D., Späth, F., Muppa, S. K., Metzendorf, S., Senff, C., and Wulfmeyer, V.: Lidar measurements characterizing the thermodynamic and dynamic structure of the boundary layer up to the turbulence scale, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7191, https://doi.org/10.5194/egusphere-egu2020-7191, 2020.

This paper reports results from an inter-comparison effort involving different sensors/techniques used to measure the Planetary Boundary Layer (PBL) height. The effort took place in the framework of the first Special Observing Period of the Hydrological cycle in the Mediterranean Experiment. The PBL is directly influenced by the Earth's surface, responding to combined action of mechanical and thermal forcing factors. The evolution of the PBL structure and height has important meteorological role. Accurate measurements of the PBL height are important to validate forecast models or support their development through the improvement of the physical representations embedded in, for example, their boundary layer turbulence and shallow convection parameterizations. Elastic backscatter signals and rotational Raman signals collected by lidar systems can be used to characterize the PBL height and its internal structure.  In the present research effort, this technique is compared with measurements from a co-located wind profiler and  a  potential temperature computed from radio-sounding system. Comparisons involving the different sensors will be discussed at the conference.

How to cite: Summa, D., Di Girolamo, P., De Rosa, B., and Madonna, F.: Intercomparison of PBL height estimations in the framework of HyMeX-SOP1, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13708, https://doi.org/10.5194/egusphere-egu2020-13708, 2020.

As part of the Cevennes-Vivarais site, the University of Basilicata Raman lidar system BASIL was deployed in Candillargues 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 the paper 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., and De Rosa, B.: Combined use of Raman lidar and DIAL measurements and MESO-NH model simulations for the characterization of complex water vapour field structures and their genesis: a case study from HyMeX-SOP 1, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16666, https://doi.org/10.5194/egusphere-egu2020-16666, 2020.

Water vapor is the most important greenhouse gas and dominates weather patterns, the atmospheric energy budget and radiative balance. For analysing
dynamic processes of planetary boundary layer we developed the ATMONSYS lidar for measuring water vapor, aerosols and temperature. In summer 2019 the application of the ATMONSYS lidar was part of the CHEESEHEAD campaign in Northern Wisconsin (USA). Former investigations showed the very high spatio-temporal short term variability of tropospheric water vapor in a three dimensional study [1]. From a technical point of view this also depicted the general requirement of short integration times while recording water-vapor profiles with lidar. For this purpose,  the differential absorption lidar (DIAL) working in the near-infrared (NIR) spectral region is a suitable technique. For measuring the light absorption by single spectral lines in the 817nm band of water vapor, the laser emission is predominated for the use of Ti:Sapphire as laser medium. We present a new concept of transversely pumping a Ti:Sapphire crystal to generate high power NIR laser emission directly from a laser resonator without amplification stage. This setup allows for a high output power at repetitions rates up to 100Hz or even more due to the enhanced cooling situation for the laser rod. It is, because of its compactness, also suitable for mobile applications. We also show a concept, how this resonator can be locked to two seeding DIAL wavelengths at the same time.

[1] Vogelmann, H., Sussmann, R., Trickl, T., and Reichert, A.: Spatiotemporal variability of water vapor investigated using lidar and FTIR vertical soundings above the Zugspitze, Atmos. Chem. Phys., 15, 3135-3148, 2015.

How to cite: Vogelmann, H., Speidel, J., and Perfahl, M.: Laser concept of the mobile ATMONSYS-lidar and its application during CHEESEHEAD, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16517, https://doi.org/10.5194/egusphere-egu2020-16517, 2020.

The Mediterranean Basin is well recognized by IPCC as a hot spot for climate change. Severe consequences are expected for the future in the Eastern Mediterranean, the Middle East and North Africa (EMMENA) region.

The increased urbanization, high pollution, dust storms and decreasing precipitation in the region dramatically affect climate change. Current prediction models for weather, climate, and environment are based on sophisticated modeling in close connection with state-of-the-art observations.

A modern observational super-site in Cyprus is of fundamental importance to understanding the atmospheric system in the EMMENA region. The presence of such a super site will be able to effectively monitor atmospheric conditions and provide relevant data for atmospheric prediction modeling.

This contribution reports on the recent progress regarding the buildup of a permanent, state-of-the-art atmospheric remote sensing station in Limassol, Cyprus. Through the EU H2020 Teaming project EXCELSIOR, the ERATOSTHENES Centre of Excellence (ECoE) will be established as a Centre of Excellence for Earth Surveillance and Space-Based Monitoring of the Environment.

The ECoE modern in-situ observational super site will be established in Cyprus for long-term profiling of the atmosphere, including wind, humidity, aerosol and cloud properties and precipitation fields. The ECoE will be fully in line with ESFRI networks, such as ACTRIS, as it will utilize state-of-the-art infrastructure and techniques to provide cutting-edge data regarding atmospheric processes.

As a demonstration initiative, an 18-month field campaign (Cy-CARE (Cyprus Cloud Aerosol and pRecipitation Experiment)) has been designed by the Leibniz Institute for Tropospheric Research (TROPOS) and was implemented by the ERATOSTHENES group at Cyprus University of Technology (CUT) between October 2016 and March 2018, with the main focus on lidar/radar-based studies of aerosol-cloud-precipitation relationships. Case studies of the Cy-CARE campaign will be presented to demonstrate the importance of the ground based atmospheric remote sensing observations in the region.

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 ACTRIS-2 project (H2020-INFRAIA-2014-2015, GA no. 654109) and the Research and Innovation Foundation of Cyprus for the financial support through the SIROCCO (EXCELLENCE/1216/0217) and AQ-SERVE (INTERGRATED/0916/0016) projects.

How to cite: Nisantzi, A., Mamouri, R.-E., Michaelides, S., Ansmann, A., Bühl, J., Seifert, P., Engelman, R., Wandinger, U., and G. Hadjimitsis, D.: The ERATOSTHENES Remote Sensing Supersite: Understanding the atmospheric system in the EMMENA region, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20839, https://doi.org/10.5194/egusphere-egu2020-20839, 2020.

Over the past ten years, important theoretical and practical results have been obtained in the field of interaction of high-power ultra-short laser pulses with solid transparent media. These results are significant for nonlinear optics and laser physics and are of practical interest for the development of femtosecond laser technology in sensing the environment, in the management of electrical discharge, in microphotonics.

However, many of the physical aspects of the supercontinuum generation and distribution of high-power femtosecond and attosecond laser pulses in an optically transparent gas media are not clear and require a detailed theoretical study.

Main objectives of the present study are the numerical simulation of high-intensity femtosecond pulses in the air, given the stimulated Raman scattering (SRS) and the stimulated Raman self-mode (SRSM) on pure nitrogen and oxygen molecules as well as on their mixtures.

Computer programs have been developed for solving nonlinear equations associated with the SRS and SRSM on the basis of a semi-classical energetic and wave theory with the help of numerical methods.

All calculations were made in the Visual Studio C ++ and Java programming environment.

The SRS mode for the distance of up to 5m for the main components of the air - nitrogen (78%) and oxygen (21%), in addition to the dynamics of the change of the pulse energy for different initial values have been calculated.

The propagation of SRMS laser pulses (λ=400, 800 nm; τ= 14, 20 fs) with positive chirp was numerically investigated for pulse energies 2π, π, π/100 and βz = 0.5, 1.0, 1.5.

The results obtained show that the dynamics of pulse propagation in SRMS mode is nonlinear in the pulse shape and spectrum.

It was estimated that the calculation results in energetic and wave models for βz≤1.5 are similar.

How to cite: Cidorkina, K., Svetashev, A., Bruchkouski, I., Barodka, S., and Turishev, L.: Numerical Simulation of Ultra-short Laser Pulses Propagation in Gas Media, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21842, https://doi.org/10.5194/egusphere-egu2020-21842, 2020.