The dynamics of the polar vortex in the Northern Hemisphere play a crucial role in shaping the composition and distribution of stratospheric aerosols. This study investigates the temporal evolution of the Junge layer within the vortex, emphasizing its interaction with aerosol characteristics. Utilizing a novel frequency-scanning lidar system, high-resolution vertical profiles of stratospheric aerosols (15–30 km) were obtained in February 2023. The ground-based lidar measurements were also validated with satellite data. These observations captured a significant polar stratospheric cloud (PSC) event on February 11, 2023, at Kühlungsborn (54°, 11°) at an altitude of 22 km, providing insight into the relationship between aerosol distribution and vortex stability.

We present a brief overview of our current developments of compact multi-field-of-view lidars for studying the 3-dimensional structure of the atmosphere and its processes over a wide range of scales with a network of lidars. Each lidar unit is based on a narrowband laser and receiver to measure the spectra of the Doppler-shifted and ñ broadened backscatter. We demonstrate that matched narrowband components enable precise daylight aerosol measurements with high aerosol visibility and high Doppler wind sensitivity in the troposphere and stratosphere 24/7. We present recent results with a focus on aerosol measurements and our next steps to demonstrate a lidar array with extended measurement capabilities.

We present the first set of simultaneous horizontal and vertical wind measurements obtained from aerosol backscatter, covering altitudes between 3 and 25 km. These measurements were made possible by using the novel VAHCOLI lidar system of the Leibniz Institute of Atmospheric Physics in Germany. Designed as a multi-purpose system incorporating Doppler-Mie, Doppler-Rayleigh, and Doppler-resonance lidar techniques for studying the middle atmosphere, the system has been upgraded to probe wind dynamics across five fields of view. Comparisons with winds from ECMWF (European Centre for Medium-Range Weather Forecasts) and Aeolus satellite data show good agreement for horizontal wind components but reveal a significant underestimation of vertical winds by ECMWF. By leveraging measurements across multiple fields of view, we highlight the system's capability to detect small-scale wind asymmetries, underscoring its value for atmospheric research.

We present a method to derive stratospheric aerosols up to 30 km from Frequency Scanning Lidar (FSL) measurements. The lidar itself is designed as a universal instrument for the middle atmosphere and is capable of doing Doppler-Mie, Doppler-Rayleigh and Doppler-resonance measurements, for simultaneous retrievals of wind, temperature and aerosols. The system leverages a narrowband Alexandrite ring laser operating at the 770 nm potassium (K) line with a 3.3 MHz spectral width and high-resolution spectroscopy. By scanning a 100 MHz spectral window with sub-MHz sampling, the filter chain efficiently suppresses the Rayleigh background and spectrally resolves the Mie peak, enabling the separation of aerosol and molecular scattering. The FSL method's solar-blind Mie channel allows for measurements both day and night, while its compact design (approximately one cubic meter in volume) facilitates mobile deployment. With a vertical resolution of 200 m and a temporal resolution of 20 min, as achieved for the data presented here using the instrument configuration described in this study, the FSL method provides high-resolution observations of aerosol distributions in the stratosphere. The uncertainties of the FSL method for the backscatter coefficient are approximately 1.5×10-10 m−1 sr−1 at 20 km, both during day and night. We demonstrate the method's capabilities by presenting backscatter coefficient profiles measured during selected periods from 2022 to 2024. These profiles show good agreement with satellite-derived profiles from the Ozone Mapping and Profiler Suite Limb Profiler (OMPS-LP) and the Stratospheric Aerosol and Gas Experiment on the International Space Station (SAGE III/ISS) with a mean absolute deviation of ∼25 % at altitudes of 15–25 km. This demonstrates the potential of the FSL method for providing high-resolution, long-term observations of stratospheric aerosols.

When the polar vortex meanders and shifts towards the equator, air masses from the tropics and subtropics can be transported towards the pole in so-called tropical-subtropical streamers. These large-scale structures are areas of low potential vorticity and high pressure, containing dry air with high ozone mixing ratios. The presence of these streamers can also be seen in changes in stratospheric optical properties. Satellite instruments such as OMPS-LP measuring the limb scattering of these aerosols are capable of observing an increase in the aerosol extinction coefficient in the mid-stratosphere at the edge of the vortex. The high spatial sampling of the limb instrument ensures that the trajectory of the streamer can be accurately monitored. Following a displacement and deformation of the vortex, aerosol transport to high latitudes occurred in the Northern Hemisphere in spring 2017. The additional stratospheric aerosol mass of around 1000 t at an altitude of 24–38 km remained at middle and high latitudes for just under a month in that year. This aerosol mass increase resulted in an estimated 70 % rise in the total mass within this altitude range at high latitudes. Frozen-in anticyclones, in which low latitude air is trapped in the circulation at high latitudes after the end of the polar vortex, can also be observed in the aerosol extinction coefficient. The observation of a particularly long-lived anticyclone in 2005, which is visible in the extinction coefficient, is presented. This is the first study documenting streamer events and frozen-in anticyclones in stratospheric aerosols.

Precise knowledge of winds and temperatures in the middle atmosphere is critical for the localization and characterization of infrasound sources. We present the concept, design, and measurement capabilities of a compact, mobile Doppler lidar system developed at the Leibniz Institute of Atmospheric Physics (IAP). This system, is designed for Doppler-Mie, -Rayleigh, and -resonance measurements in the middle atmosphere.The daylight-capable instrument features a compact volume of about 1 m³ and is engineered for easy deployment as part of an array of lidar units. We highlight recent results, emphasizing collocated, high-resolution measurements of wind and temperature. By employing three to five individual fields of view, the system can measure both horizontal and vertical wind components. Between altitudes of 3 and 25 km, the instrument utilizes the narrowband properties of Mie backscatter, relying solely on aerosol backscatter to achieve precise three-dimensional wind measurements. In this altitude range, a novel method enables the measurement of vertical winds with an accuracy better than 0.5 m/s and a time resolution of just 60 seconds.Above 25 km, winds will be measured using Doppler-Rayleigh and -resonance techniques. Concurrent Rayleigh temperature measurements utilize advanced aerosol correction methods, taking advantage of the instrument's high sensitivity to aerosols.The feasibility of integrating this lidar system into a European lidar array is being investigated within the EULIAA (European Lidar Array for Atmospheric Climate Monitoring) project. The transfer of this technology to industry is currently being developed through the LidarCUBE project.

We present the development progress of our compact multi-field-of-view lidar units for investigating small- to large-scale processes in the atmosphere. Matched narrowband laser and receiver enable precise daylight aerosol measurements with high aerosol visibility and high Doppler wind sensitivity in the troposphere/stratosphere and above. We present recent results with focus on extended measurement capabilities of our transportable systems.Daylight capable Doppler lidars are complex systems particularly as lidar arrays require compact units with automated functionality. To study the 3-dimensional structure of small- to large-scale atmospheric processes we developed a universal Doppler lidar platform with multiple fields of view. All required technologies are included for studying Mie scattering (aerosols), Rayleigh scattering (air molecules), and resonance fluorescence (potassium atoms) from the troposphere (5 km) to the thermosphere (100 km). We developed unique frequency scanning laser and filter techniques that enable multiple observations (wind, temperature, aerosols, metal density). The combination of narrowband emitter and receiver allow a spectral high resolved characterization of the backscattered Doppler signals with a high wind sensitivity and aerosol visibility. Our current developments focus on enhancing lidar measurement capabilities of multiple parameters together with transferring the technology into industry (Project LidarCUBE) and demonstration of lidar array with enhanced daylight capability (EULIAA – European Lidar Array for Atmospheric Climate Monitoring). We will show recent results of our unique lidar technique with focus on aerosol measurements and more.

We present the first measurements of simultaneous horizontal and vertical winds using a new lidar system developed at the Leibniz Institute of Atmospheric Physics in Kühlungsborn, Germany (54.12° N, 11.77° E), for the concept of Vertical And Horizontal COverage by LIdars (VAHCOLI). We describe the technical details of a multi-field-of-view (MFOV) upgrade, which allows the measurement of wind dynamics in the transition region from microscale to mesoscale (103–104 m). The method was applied at the edge of a developing high-pressure region, covering altitudes between 3 and 25 km. Comparisons between the lidar measurements and data from the European Centre for Medium-Range Weather Forecasts (ECMWF) show excellent agreement for the meridional wind component along the north beam of the lidar, which is better than 0.30±0.33 m s−1, while along the south beam, a higher deviation with -0.93±0.73 m s−1 is observed. Measurements of vertical wind show a significant underestimation of this component by ECMWF. Comparison of Aeolus winds to the lidar winds projected to the Aeolus viewing direction shows good agreement, with results better than -0.12±3.31 m s−1. The capability of the MFOV lidar to explore small-scale asymmetries in the wind field is shown by a comparison of the north and south field of view, where we observe a wind asymmetry in the meridional winds, which is also present in ECMWF but underestimated by a factor of approximately 4.

Abstract. We present the first measurements of simultaneous horizontal and vertical winds using a new VAHCOLI lidar system developed at the Leibniz Institute for Atmospheric Physics in Kühlungsborn, Germany (54.12° N, 11.77° E). We describe the technical details of a multi-field-of-view (MFOV) upgrade, which allows to measure wind dynamics in the transition region from microscale to mesoscale (103−104 m). The method was applied at the edge of a developing high-pressure region. Comparisons between the lidar measurements and data from ECMWF show excellent agreement for the horizontal wind components, better than 0.30 ± 0.36 m s−1 along the north beam of the lidar and −0.93 ± 0.73 m s−1 along the south beam. Measurements of vertical wind show significant underestimation of this component by ECMWF. Comparison to ADM-Aeolus shows good agreement, better than −0.12 ± 3.31 m s−1. The capability of the MFOV lidar to explore small-scale asymmetries in the wind field is shown by comparison of the north and south field of view, where we observe a wind asymmetry in the meridional winds, which is also present in ECMWF but underestimated by a factor of approximately four.

We present the state of the VAHCOLI (Vertical and Horizontal COverage by Lidar) project for investigating small- to large-scale processes in the atmosphere. In the future, an array of compact lidars with multiple fields of view will allow for measurements of temperatures, winds and aerosols with high temporal and vertical resolution.Doppler lidars, in particular resonance Doppler lidars, with daylight capability are challenging systems because of the small field of view, spectral filtering and other additional subsystems required compared to observations at night. We developed a universal Doppler lidar platform (~1m3, ~500kg) with all required technologies for automatic operation. The system is capable of studying Mie scattering (aerosols), Rayleigh scattering (air molecules), and resonance fluorescence on free potassium atoms in the middle atmosphere from 5 km to 100 km. Unique spectral methods and narrowband optical components allow precise wind, temperature, and aerosol measurements by studying the Doppler shift and broadening of the scattered signals. The combination of cost-efficient design and fast assembling of such a system allows the construction of a Doppler lidar network with identical unitsWe will show the latest results and discuss the next scientific and technical steps for network operation and transferring the technology into industry.

The stratopause is by definition the transition between the stratosphere and mesosphere. During winter the circulation at mid-latitudes and high latitudes in the stratosphere is mainly driven by quasi-stationary planetary waves (PWs), while the circulation in the mesosphere is mainly driven by gravity waves (GWs). The question arises of whether PWs or GWs dominate the variability of the stratopause. The most famous and dramatic variability of the middle atmosphere is a sudden stratospheric warming (SSW) generated by PWs interacting with the polar vortex. A similar phenomenon but smaller in magnitude and more regional is stratopause temperature enhancements (STEs) initially observed by local measurements and generated by breaking PWs. Thus it seems that PWs dominate the variability of the stratopause. In this study we want to quantify to which extent quasi-stationary PWs contribute to the stratopause variability. To do that we combine local lidar observations at Kühlungsborn (54∘ N, 11∘ E) and Andenes (69∘ N, 16∘ E) with global MERRA-2 reanalysis data bringing the local variability of the stratopause into the global context. Therefore we compare the temperature time series at Kühlungsborn and Andenes at 2 hPa, the altitude where STEs maximize, with characteristics (amplitude and phase) of PWs with wave numbers 1, 2 and 3. We found that for Kühlungsborn and Andenes 98 % of the local day-to-day variability of the stratopause can be explained by the variability of PWs with wave number 1, 2 and 3. Thus, the winter stratopause day-to-day variability is highly dominated by the variability of PWs.

Daytime lidar operation in the middle atmosphere requires a narrow field of view (FOV) of the receiving telescope for effective background reduction and a high-transmission narrow-band detection. The laser beam position in the atmosphere relative to the optical axis of the receiving telescope is subject to high-frequency disturbances such as turbulence, vibration, and wind as well as comparable slow drift (thermal effects of the laser, stability of the building, etc.). We developed a beam stabilization system (BSS) that ensured a pulse-to-pulse stabilization of the laser beam with ~ 3 μrad remaining jitter, allowing ~ 60 μrad FOV. With BSS and single-pulse data acquisition system, the optimal alignment of the laser and telescope can be controlled, and information on the FOV and laser divergence in the far field can be derived. The capability of the BSS is to stabilize the laser against all internal and external disturbances below the repetition rate of the laser.

To investigate the vertical propagation of gravity waves from the lower to the upper atmosphere, combined measurements with an airglow imager and lidars were carried out at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) station (69.3°N, 16.0°E) in northern Norway. Airglow imaging reveals the two-dimensional structure of gravity waves in the mesopause region, while the ALOMAR Rayleigh/Mie/Raman (RMR) lidar and sodium lidar provide the vertical structures between the stratosphere and the lower thermosphere. On 26 November 2010, the imager identified a mesoscale gravity wave structure in the sodium airglow that had a horizontal wavelength of 277 km, a wave period of 59 min, and propagated northeastward at a phase speed of 78 m s−1. Simultaneous lidar measurements also showed upward wave signatures with a similar wave period in the temperature perturbations; the vertical wavelength of the upward wave seen in the temperature data is consistent with the dispersion relation for gravity waves. Based on the combined measurements with the imager and sodium lidar, the momentum flux of this gravity wave was estimated to be 1.0 m2 s−2 at the sodium airglow height. Ray-tracing analysis suggested that the observed gravity wave was generated by a distortion of the polar jet at the tropopause via a geostrophic adjustment process.

Ground-based lidar measurements and balloon soundings were employed to examine the dynamical link between anticyclonic Rossby wave breaking and cirrus clouds from 13 to 15 February 2006. For this event, an air mass with low Ertel's potential vorticity appeared over Central Europe. In the tropopause region, this air mass was accompanied with both an area of extreme cold temperatures placed northeastward, and an area of high specific humidity, located southwestward. ECMWF analyses reveal a strong adiabatic northeastward and upward transport of water vapour within the warm conveyor belt on the western side of the ridge over Mecklenburg, Northern Germany. The backscatter lidar at Kuhlungsborn (54.1 degrees N, 11.8 degrees E) clearly identified cirrus clouds at between 9 and 11.4 km height. In the tropopause region high-vertical resolution radiosoundings showed layers of subsaturated water vapour over ice but with a relative humidity over ice > 80%. Over Northern Germany radiosondes indicated anticyclonically rotating winds in agreement with backward trajectories of ECMWF analyses in the upper troposphere, which were accompanied by a relatively strong increase of the tropopause height on 14 February. Based on ECMWF data the strong link between the large-scale structure, updraft and ice water content was shown.

Lidars provide an important tool to measure temperature and minor constituents in the atmosphere up to ~110 km altitude with high accuracy and temporal resolution. The Leibniz-Institute of Atmospheric Physics operates various lidars for the whole range between troposphere and lower thermosphere. The lidars are installed at Kühlungsborn, Germany (54°N, 12°E), at the ALOMAR site, Norway (69°N, 16°E), or in a mobile 20-foot container. Summertime soundings in polar regions as well as coverage of tides and gravity waves require measurements during full daylight. With a standard lidar the daylight background is several magnitudes larger than the signal in the mesosphere. Narrowband spectral filtering by etalons as well as spatial filtering by small fields of view (~50 μrad) are realized instead. At this low FOV turbulence and jitter of the beam pointing affects the signal and have to be compensated. We describe the techniques applied at our lidars. Additionally we will discuss the influence of the etalon filter technique on calculated temperature profiles. The etalon transmission of the Doppler-broadened backscatter signal is temperature dependent and has to be taken into account to avoid systematic errors. Overall, narrow-band lidars provide temperature profiles in the whole range up to the lower thermosphere. We will present observations of temperatures profiles of the lower and middle atmosphere as well as noctilucent clouds (NLC). These quantities provide important insights into the dynamics of the middle atmosphere. Time-resolved and averaged profiles of observations at the different locations will be shown and the results from different latitudes compared.

During the airborne CONTRACE field experiment carried out in November 2001 a number of polluted layers of North American (NA) origin were observed in the free troposphere over Europe. For the first time, forecasts from a Lagrangian particle dispersion model were used to predict the NA pollution events and to direct a research aircraft very precisely into these polluted layers above Europe. Two of the NA pollution events are investigated here: one in detail (case 19 November) and a second more briefly (case 22 November). An exceptional result was that the first pollution plume could be traced with the model and trace gas measurements (airborne and surface) for a period of one week, from the source region over the eastern United States to its decay over the Alps. On 14–15 November a warm conveyor belt lifted the leading edge of the pollution plume over the eastern United States to the mid troposphere where it remained during the transport over the Atlantic. On 19 November the plume was intersected with the research aircraft over Scandinavia at an altitude between 2 and 4 km. Elevated CO (170), O 3 (53), NO y (1.1), acetone (5.0), and SO 2 (2.6) mixing ratios (nmol mol −1 ) were measured. A positive O 3 ‐CO correlation was observed in the plume. The observations indicate that the enhanced levels of ozone were already produced near the source region over the eastern United States and not during the transit. In the next days one branch of the plume then turned to the south and descended to ground level over the Alpine region. Elevated O 3 (54 nmol mol −1 ) and CO (168 nmol mol −1 ) were observed at the mountain site Zugspitze (southern Germany) during two days. At the Arosa Alpine site in Switzerland the highest daily ozone means of November 2001 were observed during this event.

Aerosol extinction vertical profiles measured with Raman lidar in the framework of EARLINET in 2000 are compared to profiles modeled by a general circulation model, LMDzT-INCA, at seven stations in Europe. Comparisons based on individual profiles show moderate correlation between model and data. Averaging aerosol extinction values on larger temporal or spatial scales improves the comparison. Furthermore, we show that the model succeeds to reproduce the mean annual aerosol distribution over Europe. Comparisons of the aerosol vertical distribution in two distinct regions of Europe are presented. For the northern stations, the observed yearly average aerosol extinction coefficient vertical profile and the modeled one show an average bias of 22%. For the southern stations the mean bias is slightly higher (29%). Both model and lidar show different extinction profiles in different parts of Europe, with higher values in upper heights in the South. According to modeled profiles of each aerosol component, this is caused by the presence of dust at altitudes between 2 and 6km. In addition vertical mixing in the South seems to be more effective for the other aerosol components.

(1) Istituto di Metodologie per l’Analisi Ambientale IMAA-CNR, Potenza, Italy, (2) Max-Planck-Institut fur Meteorologie, Hamburg, Germany, (3) Aristoteleio Panepistimio, Thessalonikis, Greece, (4) Leibniz-Institut fur Atmospharenphysik, Kuhlungsborn, Germany, (5) Universita degli Studi – L’Aquila, Italy, (6) Physics Department, University of Wales, Aberystwyth, United Kingdom, (7) Max-Planck-Institut fur Meteorologie, Hamburg, Germany; Current affiliation: Institute for Coastal Research, GKSS Research Center, Geesthacht, Germany, (8) Institut fur Tropospharenforschung, Leipzig, Germany, (9) Ethnikon Metsovion Polytechnion Athinon, Athens, Greece, (10) University of Lecce, Physics Department, Lecce, Italy, (11) Istituto Nazionale per la Fisica della Materia, Napoli, Italy, (pappalardo@imaa.cnr.it / Fax: +39 0971427271 / Phone.+39 0971427265)

In the framework of the European Aerosol Research Lidar Network to Establish an Aerosol Climatology (EARLINET), 19 aerosol lidar systems from 11 European countries were compared. Aerosol extinction or backscatter coefficient profiles were measured by at least two systems for each comparison. Aerosol extinction coefficients were derived from Raman lidar measurements in the UV (351 or 355 nm), and aerosol backscatter profiles were calculated from pure elastic backscatter measurements at 351 or 355, 532, or 1064 nm. The results were compared for height ranges with high and low aerosol content. Some systems were additionally compared with sunphotometers and starphotometers. Predefined maximum deviations were used for quality control of the results. Lidar systems with results outside those limits could not meet the quality assurance criterion. The algorithms for deriving aerosol backscatter profiles from elastic lidar measurements were tested separately, and the results are described in Part 2 of this series of papers [Appl. Opt. 43, 977-989 (2004)]. In the end, all systems were quality assured, although some had to be modified to improve their performance. Typical deviations between aerosol backscatter profiles were 10% in the planetary boundary layer and 0.1 x 10(-6) m(-1) sr(-1) in the free troposphere.

Since 2000, regular lidar observations of the vertical aerosol distribution over Europe have been performed within the framework of EARLINET, the European Aerosol Research Lidar Network. A statistical analysis concerning the vertical distribution of the volume light extinction coefficients of particles derived from Raman lidar measurements at 10 EARLINET stations is presented here. The profiles were measured on a fixed schedule with up to two measurements per week; they typically covered the height range from 500 m to 6000 m above ground level (agl). The analysis is made for the planetary boundary layer (PBL) as well as for several fixed layers above ground. The results show typical values of the aerosol extinction coefficient and the aerosol optical depth (AOD) in different parts of Europe, with highest values in southeastern Europe and lowest values in the northwestern part. Annual cycles and cumulative frequency distributions are also presented. We found that higher aerosol optical depths in southern Europe compared to the northern part are mainly attributed to larger amounts of aerosol in higher altitudes. At 9 of the 10 sites the frequency distribution of the aerosol optical depth in the planetary boundary layer follows a lognormal distribution at the 95% significance level.