Stephan Rahm

German Aerospace Center (DLR) | DLR · Institute of Atmospheric Physics

In the course of the GW-LCYCLE II campaign, conducted in Jan/Feb 2016 from Kiruna, Sweden, coherent Doppler wind lidar (2 µm DWL) measurements were performed from the DLR Falcon aircraft to investigate gravity waves induced by flow across the Scandinavian Alps. During a mountain wave event on 28 January 2016, a novel momentum flux (MF) scan pattern...

During the first 3 years of the European Space Agency's Aeolus mission, the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, DLR) performed four airborne campaigns deploying two different Doppler wind lidars (DWL) on board the DLR Falcon aircraft, aiming to validate the quality of the recent Aeolus Level 2B (L2B) wind data produc...

The Atmospheric LAser Doppler Instrument (ALADIN) on-board Aeolus was the first European lidar and the first direct-detection Doppler wind lidar (DWL) in space. To support the processor development and operational preparation of the ESA mission, for the first time an airborne technology demonstrator was implemented in parallel. The ALADIN Airborne...

Since the start of the European Space Agency's Aeolus mission in 2018, various studies were dedicated to the evaluation of its wind data quality and particularly to the determination of the systematic and random errors in the Rayleigh-clear and Mie-cloudy wind results provided in the Aeolus Level-2B (L2B) product. The quality control (QC) schemes a...

Since the start of the European Space Agency’s Aeolus mission in 2018, various studies were dedicated to the evaluation of its wind data quality, and particularly to the determination of the systematic and random errors of the Rayleigh-clear and Mie-cloudy wind results provided in the Aeolus Level-2B (L2B) product. The quality control (QC) schemes...

During the first three years of European Space Agency’s Aeolus mission, the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, DLR) performed four airborne campaigns deploying two different Doppler wind lidars (DWL) on-board the DLR Falcon aircraft, aiming to validate the quality of the recent Aeolus Level 2B (L2B) wind data produc...

In the course of the GW-LCYCLE II campaign, conducted in Jan/Feb 2016 from Kiruna, Sweden, coherent Doppler wind lidar (2-µm DWL) measurements were performed from the DLR Falcon aircraft to investigate small-scale gravity waves induced by flow across the Scandinavian Alps. During a mountain wave event on 28 January 2016, a novel momentum flux (MF)...

In the course of the GW-LCYCLE II campaign, conducted in Jan/Feb 2016 from Kiruna, Sweden, coherent Doppler wind lidar (2-µm DWL) measurements were performed from the DLR Falcon aircraft to investigate small-scale gravity waves induced by flow across the Scandinavian Alps. During a mountain wave event on 28 January 2016, a novel momentum flux (MF)...

The realization of the European Space Agency's Aeolus mission was supported by the long-standing development and field deployment of the Atmospheric LAser Doppler INstrument (ALADIN) Airborne Demonstrator (A2D) which, since the launch of the Aeolus satellite in 2018, has been serving as a key instrument for the validation of ALADIN, the first-ever...

In August 2018, the first-ever spaceborne wind lidar – Aeolus – was launched and has since then been providing global data of the horizontal wind field from the ground up to 30 km to improve numerical weather prediction. Aeolus is based on a single instrument called ALADIN (Atmospheric Laser Doppler Instrument), which comprises a single-frequency,...

The realization of the European Space Agency’s Aeolus mission was supported by the long-standing development and field deployment of the ALADIN Airborne Demonstrator (A2D) which, since the launch of the Aeolus satellite in 2018, has been serving as a key instrument for the validation of the Atmospheric LAser Doppler INstrument (ALADIN), the first-e...

Übersicht über die DLR-Flugkampagnen im Rahmen der Aeolus-Windvalidierung und deren Ergebnisse.

Soon after the launch of Aeolus on 22 August 2018, the first ever wind lidar in space developed by the European Space Agency (ESA) has been providing profiles of the component of the wind vector along the instrument's line of sight (LOS) on a global scale. In order to validate the quality of Aeolus wind observations, the German Aerospace Center (De...

Observations across the North Atlantic jet stream with high vertical resolution are used to explore the structure of the jet stream, including the sharpness of vertical wind shear changes across the tropopause and the wind speed. Data was obtained during the North Atlantic Waveguide and Downstream impact EXperiment (NAWDEX) by an airborne Doppler w...

Shortly after the successful launch of the European Space Agency's wind mission Aeolus, co-located airborne wind lidar observations were performed in central Europe; these observations employed a prototype of the satellite instrument – the ALADIN (Atmospheric LAser Doppler INstrument) Airborne Demonstrator (A2D). Like the direct-detection Doppler w...

Abstract. Soon after the launch of Aeolus on 22 August 2018, the first ever wind lidar in space developed by the European Space Agency (ESA) has been providing profiles of the component of the wind vector along the instrument's line-of-sight (LOS) on a global scale. In order to validate the quality of Aeolus wind observations, the German Aerospace...

Shortly after the successful launch of ESA’s wind mission Aeolus, carried out by the European Space Agency, collocated airborne wind lidar observations were performed in Central Europe, employing the prototype of the satellite instrument, the ALADIN Airborne Demonstrator (A2D). Like the direct-detection Doppler wind lidar on-board Aeolus, the A2D i...

Soon after its successful launch in August 2018, the spaceborne wind lidar ALADIN (Atmospheric LAser Doppler INstrument) on-board ESA’s Earth Explorer satellite Aeolus has demonstrated to provide atmospheric wind profiles on a global scale. Being the first ever Doppler Wind Lidar (DWL) instrument in space, ALADIN contributes to the improvement in n...

Since the successful launch of ESA’s Earth Explorer mission Aeolus in August 2018, atmospheric wind profiles from the ground to the lower stratosphere are being acquired on a global scale deploying the first-ever satellite-borne wind lidar system ALADIN (Atmospheric LAser Doppler INstrument). ALADIN provides one component of the wind vector along t...

Soon after its successful launch in August 2018, the spaceborne wind lidar ALADIN (Atmospheric LAser Doppler INstrument) on-board ESA's Earth Explorer satellite Aeolus has demonstrated to provide atmospheric wind profiles on a global scale. Being the first ever Doppler Wind Lidar (DWL) instrument in space, ALADIN contributes to the improvement in n...

The Aeolus satellite mission of the European Space Agency (ESA) has brought the first wind LiDAR to space to satisfy the long-existing need for global wind profile observations. Until the successful launch on 22 August 2018, pre-launch campaign activities supported the validation of the measurement principle, the instrument calibration, and the opt...

After its launch in autumn 2018, the spaceborne wind lidar ALADIN (Atmospheric LAser Doppler INstrument) on-board ESA's Earth Explorer satellite Aeolus will allow for global observation of atmospheric wind profiles. Being the first ever satellite-borne Doppler wind lidar instrument, ALADIN will significantly contribute to the improvement in numeric...

In preparation of ESA's upcoming Earth Explorer mission Aeolus which strives for the global observation of wind profiles from the ground to the lower stratosphere deploying the first-ever satellite-borne wind lidar system ALADIN, the ALADIN airborne demonstrator (A2D) has been developed at DLR (German Aerospace Center). Due to its representative de...

In preparation of the satellite mission Aeolus carried out by the European Space Agency, airborne wind lidar observations have been performed in the frame of the North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX), employing the prototype of the satellite instrument, the ALADIN Airborne Demonstrator (A2D). The direct-detection Dopple...

The North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft, each with a sophisticated set of remote sensing and in situ instruments, and coordinated with a sui...

In preparation of the satellite mission Aeolus carried out by the European Space Agency, airborne wind lidar observations have been performed in the frame of the North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX), employing the prototype of the satellite instrument, the ALADIN Airborne Demonstrator (A2D). The direct-detection Dopple...

The launch of the Aeolus mission by the European Space Agency (ESA) is planned for 2018. The satellite will carry the first wind lidar in space, ALADIN (Atmospheric Laser Doppler INstrument). Its prototype instrument, the ALADIN Airborne Demonstrator (A2D), was deployed during several airborne campaigns aiming at the validation of the measurement p...

Airborne coherent Doppler wind lidar measurements, acquired during the GW-LCYCLE I campaign performed from 2 to 14 December 2013 in Kiruna, Sweden, are used to investigate internal gravity waves (GWs) induced by flow across the Scandinavian Alps. Vertical wind speed is derived from lidar measurements with a mean bias of less than 0.05 ms−1 and a st...

Two mountain wave events, which occurred over northern Scandinavia in December 2013 are analysed by means of airborne observations and global and mesoscale numerical simulations with horizontal mesh sizes of 16, 7.2, 2.4 and 0.8 km. During both events westerly cross-mountain flow induced upward-propagating mountain waves with different wave charact...

Airborne campaigns employing wind lidars for atmospheric research started at DLR in 1999. They allow the observation of vertical profiles of the horizontal wind vector from ground up to the aircraft with spatial resolution of a few km horizontally and 100 m vertically. Targeted observations were performed in the North Atlantic region in 2003 for th...

Two mountain wave events, which occured over northern Scandinavia in December 2013 are analysed by means of airborne observations and global and mesoscale numerical simulations with horizontal mesh sizes of 16 km, 7.2 km, 2.4 km and 0.8 km. During both events westerly cross-mountain flow induced upward propagating waves in the troposphere and strat...

A novel method for coherent Doppler wind lidars (DWLs) calibration is shown in this work. Concurrent measurements of a ground based aerosol lidar operating at 532 nm and an airborne DWL at 2 μm are used in combination with sun photometer measurements for the retrieval of backscatter and extinction profiles. The presented method was successfully app...

During the SALTRACE field experiment, conducted during June/July 2013, the Saharan dust transport across the Atlantic was analyzed by a set of ground based, in-situ and airborne instruments, including a 2-μm coherent DWL (Doppler wind lidar) mounted onboard the DLR Falcon 20 research aircraft. An overview of the measurements of aerosol backscatter...

This study presents methods for the retrieval of calibrated backscatter and vertical wind speed from an airborne Doppler wind lidar (DWL). The backscatter retrieval relies on sun photometer measurements and the simultaneous retrievals of an airborne DWL at 2 μm and a ground-based aerosol lidar at 532 nm for the retrieval of the calibration constant...

This study presents the analysis of island induced gravity waves observed by an airborne Doppler wind lidar (DWL) during SALTRACE. First, the instrumental corrections required for the retrieval of high spatial resolution vertical wind measurements from an airborne DWL are presented and the measurement accuracy estimated by means of two different me...

This study presents the analysis of island induced gravity waves observed by an airborne Doppler wind lidar (DWL) during SALTRACE. First, the instrumental corrections required for the retrieval of high spatial resolution vertical wind measurements from an airborne DWL are presented and the measurement accuracy estimated by means of two different me...

The method of radial velocities (RV) is applied to estimate aircraft wake vortex parameters from measurements conducted with pulsed coherent Doppler lidar (PCDL). Operations of the Stream Line lidar and the 2-µm PCDL are simulated numerically to analyze the accuracy of the estimated wake vortex parameters with the RV method. The RV method is also u...

A novel method for calibration and quantitative aerosol optical property retrieval from Doppler wind lidars (DWLs) is presented in this work. Due to the strong wavelength dependence of the atmospheric molecular backscatter and the low sensitivity of the coherent DWLs to spectrally broad signals, calibration methods for aerosol lidars cannot be appl...

A novel method for calibration and quantitative aerosol optical properties retrieval from Doppler wind lidars (DWL) is presented in this work. Due to the strong wavelength dependence of the atmospheric molecular backscatter and the low sensitivity of the 5 coherent detection to spectrally broad signals, calibration methods for aerosol lidars cannot...

A technique is proposed for determination of the structure characteristic of refractive index of air from data of a coherent Doppler wind lidar. The proposed technique is tested in atmospheric experiments. Time profiles of the structure characteristic of refractive index in the atmospheric surface layer are obtained and compared with the time profi...

The Atmospheric Dynamics Mission ADM-Aeolus of ESA will be the first lidar mission to sense the global wind field from space. An airborne prototype instrument – the ALADIN Airborne Demonstrator A2D – was developed to assess the performance of the Doppler lidar ALADIN on ADM-Aeolus and to optimize the retrieval algorithms with atmospheric signals. T...

A technique is proposed for estimating the refractive index structure characteristic of air from data of a coherent Doppler wind lidar. The proposed technique is tested in atmospheric experiments. Time profiles of the structure characteristic in the atmospheric surface layer are obtained and compared with the time profiles of the dissipation rate o...

The fact that severe weather associated with polar lows and arctic fronts still comes unforeseen and puts human life at risk shows that an effort towards increased understanding of them is required. The observations of an arctic front by dropsondes and Doppler lidar carried onboard a research aircraft during the IPY-THORPEX field campaign offered a...

Water vapor, a minor constituent of the earth's atmosphere, plays a major role in the radiation budget and the water cycle with important implications for weather and climate. Due to the heterogeneous distribution of its sources, evaporation, and sinks, condensation and precipitation, and due to the complexity of atmospheric motion and mixing, its...

The global measurement of wind profiles is considered to be of highest priority regarding the needs for numerical weather prediction (NWP). Therefore, the European Space Agency ESA implemented the ADM-Aeolus satellite mission with a scheduled launch date in 2015. It will demonstrate the potential of the Doppler wind lidar technology for providing v...

The Atmospheric Dynamics Mission ADM-Aeolus of ESA will be the first lidar mission to sense the global wind field from space. The instrument is based on a direct-detection Doppler lidar operating at 354.9 nm with two spectrometers for aerosol/cloud and molecular backscatter. In order to assess the performance of the Doppler lidar ALADIN on ADM-Aeol...

The combination of a water vapour and a wind lidar on an aircraft is an interesting new tool that allows to measure latent heat flux profiles and the small- to mesoscale variability beneath the aircraft along the flight track. During the Convective and Orographically-induced Precipitation Study (COPS) in July 2007 over the Black Forest low-mountain...

A set of about 2500 Doppler wind lidar (DWL) profiles was measured by the DLR Falcon aircraft during the life cycle of Typhoon Sinlaku in the western North Pacific as part of the THORPEX Pacific Asian Regional Campaign (T-PARC) 2008. These DWL profiles were assimilated in the global models of the European Centre for Medium-Range Weather Forecasts (...

The Aeolus mission of the European Space Agency (ESA) will send the first wind lidar to space to fulfill the utmost need for global wind profile observations. Before the scheduled launch in late 2013, pre-launch campaigns have to be performed to validate the measurement principle and to optimize retrieval algorithms. Therefore, an airborne prototyp...

In the course of the eruption of the Icelandic volcano Eyjafjallajökull in April/Mai 2010 it became obvious that lidar observations are excellent tools? to characterize aerosol plumes. This includes monitoring of the dispersion of the layers in space and time, and the assessment of optical and microphysical parameters. Lidar derived data sets were...

Warm conveyor belts (WCBs) are key flow structures associated with extratropical cyclones. They transport moist air from the cyclone’s warm sector poleward and upward close to the tropopause level, leading to the formation of elongated cloud bands, intense latentheating and surface precipitation. In this study a comprehensive dataset of airborne li...

The combination of a water vapour and a wind lidar on an aircraft enables the study of a variety of atmospheric transport processes associated with reduced predictability over remote and data sparse areas such as oceans. The instrument combination was successfully deployed on board the DLR Falcon research aircraft in the field experiments COPS 2007...

Airborne lidar and in-situ measurements of aerosols and trace gases were performed in volcanic ash plumes over Europe between Southern Germany and Iceland with the Falcon aircraft during the eruption period of the Eyjafjalla volcano between 19 April and 18 May 2010. Flight planning and measurement analyses were supported by a refined Meteosat ash p...

Vertical profiles of the latent heat flux in a convective boundary layer (CBL) are obtained for the first time over complex terrain with airborne water vapour differential absorption lidar and Doppler wind lidar. During the Convective and Orographically-induced Precipitation Study (COPS) over the Black Forest mountains in south-western Germany both...

First collocated measurements were performed by the novel four-wavelength differential absorption lidar WALES and the scanning 2 μm Doppler wind lidar onboard the DLR research aircraft Falcon during the European THORPEX Regional Campaign in 2007. One mission which was characterized by exceptionally high data coverage (47% for the specific humidity...

In April/May 2010 large areas of the European airspace were impacted by volcanic ash layers originating from the Eyjafjalla volcano in Iceland. Between 19 April and 18 May 2010, the DLR-Falcon performed 17 research flights in aged (up to 120 h) volcanic ash plumes over Central and Western Europe, but also in a young (7 h) plume close to the volcano...

Airborne measurements of Lidar backscatter, aerosol concentrations (particle diameters of 4 nm to 50 μm), trace gas mixing ratios (SO₂, CO, O₃, H₂O), single particle properties, and meteorological parameters have been performed in volcanic ash plumes with the Falcon aircraft operated by Deutsches Zentrum für Luft- u...

Long-range Doppler wind light detection and ranging (lidar) measurements at a wind turbine were carried out for the first time. The turbine was of the type Areva M5000 and is located at a site near the coastline in Bremerhaven, in the northern part of Germany. This wind turbine is the prototype for the German offshore test site ‘‘alpha ventus’’ an...

Between April 19 and May 18, 2010, altogether 17 flights were performed by the DLR Falcon research aircraft to survey and sample the emissions of the Eyjafjalla volcano on Iceland. The measurements were performed on request of the Deutscher Wetterdienst (DWD, German Weather Service) and the Bundesministerium für Verkehr, Bau und Stadtentwicklung (B...

During the Convective and Orographically-induced Precipitation Study (COPS) in July 2007 over the Black Forest Mountains in south-western Germany, tropospheric profiles of water vapour and wind were measured with a differential absorption lidar (DIAL) and a heterodyne detection 2-μm Doppler wind lidar collocated on board the DLR Falcon research air...

This presentation describes the measurements performed by DLR with Lidar and insitu instruments on the DLR Falcon in volcanic ash in Apriland May 2010.

At the time of the EGU conference, the volcano ash plume originating from the Eyjafjallajökull volcano eruption in Iceland was probed during 9 flights with the DLR Falcon research aircraft in the region between Germany and Iceland at 1-11 km altitudes between April 19 and May 3, 2010. The Falcon was instrumented with a downward looking, scanning 2-...