28 results on '"Geiß, Alexander"'
Search Results
2. First Results from the German Cal/Val Activities for Aeolus
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Baars Holger, Geiß Alexander, Wandinger Ulla, Herzog Alina, Engelmann Ronny, Bühl Johannes, Radenz Martin, Seifert Patric, Ansmann Albert, Martin Anne, Leinweber Ronny, Lehmann Volker, Weissmann Martin, Cress Alexander, Filioglou Maria, Komppula Mika, and Reitebuch Oliver
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Physics ,QC1-999 - Abstract
On 22nd August 2018, the European Space Agency (ESA) launched the first direct detection Doppler wind lidar into space. Operating at 355 nm and acquiring signals with a dual channel receiver, it allows wind observations in clear air and particle-laden regions of the atmosphere. Furthermore, particle optical properties can be obtained using the High Spectral Resolution Technique Lidar (HSRL) technique. Measuring with 87 km horizontal and 0.25-2 km vertical resolution between ground and up to 30 km in the stratosphere, the global coverage of Aeolus observations shall fill gaps in the global observing system and thus help improving numerical weather prediction. Within this contribution, first results from the German initiative for experimental Aeolus validation are presented and discussed. Ground-based wind and aerosol measurements from tropospheric radar wind profilers, Doppler wind lidars, radiosondes, aerosol lidars and cloud radars are utilized for that purpose.
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- 2020
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3. Initial Assessment of the Performance of the First Wind Lidar in Space on Aeolus
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Reitebuch Oliver, Lemmerz Christian, Lux Oliver, Marksteiner Uwe, Rahm Stephan, Weiler Fabian, Witschas Benjamin, Meringer Markus, Schmidt Karsten, Huber Dorit, Nikolaus Ines, Geiss Alexander, Vaughan Michael, Dabas Alain, Flament Thomas, Stieglitz Hugo, Isaksen Lars, Rennie Michael, de Kloe Jos, Marseille Gert-Jan, Stoffelen Ad, Wernham Denny, Kanitz Thomas, Straume Anne-Grete, Fehr Thorsten, von Bismarck Jonas, Floberghagen Rune, and Parrinello Tommaso
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Physics ,QC1-999 - Abstract
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 numerical weather prediction (NWP) by measuring one component of the horizontal wind vector. The performance of the ALADIN instrument was assessed by a team from ESA, DLR, industry, and NWP centers during the first months of operation. The current knowledge about the main contributors to the random and systematic errors from the instrument will be discussed. First validation results from an airborne campaign with two wind lidars on-board the DLR Falcon aircraft will be shown.
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- 2020
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4. Simulating structural plasticity of the brain more scalable than expected
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Czappa, Fabian, Geiß, Alexander, and Wolf, Felix
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- 2023
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5. Validation of the Aeolus L2B wind product by means of airborne wind lidar measurements performed in the North Atlantic region and in the tropics
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Witschas, Benjamin, Geiß, Alexander, Lux, Oliver, Lemmerz, Christian, Marksteiner, Uwe, Schäfler, Andreas, Rahm, Stephan, Reitebuch, Oliver, and Weiler, Fabian
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validation ,Wind-lidar ,Aeolus - Published
- 2022
6. Validation of the Aeolus L2B wind product with airborne wind lidar measurements in the polar North Atlantic region and in the tropics.
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Witschas, Benjamin, Lemmerz, Christian, Geiß, Alexander, Lux, Oliver, Marksteiner, Uwe, Rahm, Stephan, Reitebuch, Oliver, Schäfler, Andreas, and Weiler, Fabian
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WIND measurement ,JET streams ,WIND speed ,DATA quality ,LIDAR - Abstract
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 product (processor baseline 11 and 12). The first two campaigns, WindVal III (November–December 2018) and AVATAR-E (Aeolus Validation Through Airborne Lidars in Europe, May and June 2019), were conducted in Europe and provided first insights into the data quality at the beginning of the mission phase. The two later campaigns, AVATAR-I (Aeolus Validation Through Airborne Lidars in Iceland) and AVATAR-T (Aeolus Validation Through Airborne Lidars in the Tropics), were performed in regions of particular interest for the Aeolus validation: AVATAR-I was conducted from Keflavik, Iceland, between 9 September and 1 October 2019 to sample the high wind speeds in the vicinity of the polar jet stream; AVATAR-T was carried out from Sal, Cape Verde, between 6 and 28 September 2021 to measure winds in the Saharan dust-laden African easterly jet. Altogether, 10 Aeolus underflights were performed during AVATAR-I and 11 underflights during AVATAR-T, covering about 8000 and 11 000 km along the Aeolus measurement track, respectively. Based on these collocated measurements, statistical comparisons of Aeolus data with the reference lidar (2 µ m DWL) as well as with in situ measurements by the Falcon were performed to determine the systematic and random errors of Rayleigh-clear and Mie-cloudy winds that are contained in the Aeolus L2B product. It is demonstrated that the systematic error almost fulfills the mission requirement of being below 0.7 m s -1 for both Rayleigh-clear and Mie-cloudy winds. The random error is shown to vary between 5.5 and 7.1 m s -1 for Rayleigh-clear winds and is thus larger than specified (2.5 m s -1), whereas it is close to the specifications for Mie-cloudy winds (2.7to2.9 m s -1). In addition, the dependency of the systematic and random errors on the actual wind speed, the geolocation, the scattering ratio, and the time difference between 2 µ m DWL observation and satellite overflight is investigated and discussed. Thus, this work contributes to the characterization of the Aeolus data quality in different meteorological situations and allows one to investigate wind retrieval algorithm improvements for reprocessed Aeolus data sets. [ABSTRACT FROM AUTHOR]
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- 2022
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7. Quality control and error assessment of the Aeolus L2B wind results from the Joint Aeolus Tropical Atlantic Campaign.
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Lux, Oliver, Witschas, Benjamin, Geiß, Alexander, Lemmerz, Christian, Weiler, Fabian, Marksteiner, Uwe, Rahm, Stephan, Schäfler, Andreas, and Reitebuch, Oliver
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QUALITY control ,HETERODYNE detection ,DOPPLER lidar ,RAYLEIGH model ,MODEL airplanes ,DATA quality - Abstract
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 applied in the analyses mostly rely on the estimated error (EE), reported in the L2B data, using different and often subjectively chosen thresholds for rejecting data outliers, thus hampering the comparability of different validation studies. This work gives insight into the calculation of the EE for the two receiver channels and reveals its limitations as a measure of the actual wind error due to its spatial and temporal variability. It is demonstrated that a precise error assessment of the Aeolus winds necessitates a careful statistical analysis, including a rigorous screening for gross errors to be compliant with the error definitions formulated in the Aeolus mission requirements. To this end, the modified Z score and normal quantile plots are shown to be useful statistical tools for effectively eliminating gross errors and for evaluating the normality of the wind error distribution in dependence on the applied QC scheme, respectively. The influence of different QC approaches and thresholds on key statistical parameters is discussed in the context of the Joint Aeolus Tropical Atlantic Campaign (JATAC), which was conducted in Cabo Verde in September 2021. Aeolus winds are compared against model background data from the European Centre for Medium-Range Weather Forecasts (ECMWF) before the assimilation of Aeolus winds and against wind data measured with the 2 µm heterodyne detection Doppler wind lidar (DWL) aboard the Falcon aircraft. The two studies make evident that the error distribution of the Mie-cloudy winds is strongly skewed with a preponderance of positively biased wind results distorting the statistics if not filtered out properly. Effective outlier removal is accomplished by applying a two-step QC based on the EE and the modified Z score, thereby ensuring an error distribution with a high degree of normality while retaining a large portion of wind results from the original dataset. After the utilization of the described QC approach, the systematic errors in the L2B Rayleigh-clear and Mie-cloudy winds are determined to be below 0.3 m s -1 with respect to both the ECMWF model background and the 2 µm DWL. Differences in the random errors relative to the two reference datasets (Mie vs. model is 5.3 m s -1 , Mie vs. DWL is 4.1 m s -1 , Rayleigh vs. model is 7.8 m s -1 , and Rayleigh vs. DWL is 8.2 m s -1) are elaborated in the text. [ABSTRACT FROM AUTHOR]
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- 2022
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8. Retrieval of atmospheric backscatter and extinction profiles with the aladin airborne demonstrator (A2D)
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Geiss Alexander, Marksteiner Uwe, Lux Oliver, Lemmerz Christian, Reitebuch Oliver, Kanitz Thomas, and Straume-Lindner Anne Grete
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Physics ,QC1-999 - Abstract
By the end of 2017, the European Space Agency (ESA) will launch the Atmospheric laser Doppler instrument (ALADIN), a direct detection Doppler wind lidar operating at 355 nm. An important tool for the validation and optimization of ALADIN’s hardware and data processors for wind retrievals with real atmospheric signals is the ALADIN airborne demonstrator A2D. In order to be able to validate and test aerosol retrieval algorithms from ALADIN, an algorithm for the retrieval of atmospheric backscatter and extinction profiles from A2D is necessary. The A2D is utilizing a direct detection scheme by using a dual Fabry-Pérot interferometer to measure molecular Rayleigh signals and a Fizeau interferometer to measure aerosol Mie returns. Signals are captured by accumulation charge coupled devices (ACCD). These specifications make different steps in the signal preprocessing necessary. In this paper, the required steps to retrieve aerosol optical products, i. e. particle backscatter coefficient βp, particle extinction coefficient αp and lidar ratio Sp from A2D raw signals are described.
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- 2018
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9. Airborne Wind Lidar Observations for the Validation of ESA's Wind Mission Aeolus
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Lux, Oliver, Lemmerz, Christian, Weiler, Fabian, Marksteiner, Uwe, Witschas, Benjamin, Rahm, Stephan, Geiß, Alexander, Schäfler, Andreas, and Reitebuch, Oliver
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Lidar ,satellite validation ,ALADIN Airborne Demonstrator ,Aeolus - Published
- 2021
10. Data quality of Aeolus wind measurements
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Krisch, Isabell, Reitebuch, Oliver, von Bismarck, Jonas, Dabas, Alain, Fischer, Peggy, Huber, Dorit, de Kloe, Jos, Rennie, Michael, Lemmerz, Christian, Lux, Oliver, Marksteiner, Uwe, Masoumzadeh, Nafiseh, Weiler, Fabian, Witschas, Benjamin, Bracci, Fabio, Meringer, Markus, Schmidt, Karsten, Geiss, Alexander, Nikolaus, Ines, Vaughan, Michael, Fabre, Frederic, Flament, Thomas, Trapon, Dimitri, Lacour, Adrien, Abdalla, Saleh, Isaksen, Lars, Donovan, Dave, Marseille, Gert-Jan, Stoffelen, Ad, Zandelhoff, Gerd-Jan, Wang, Ping, Perron, Gaetan, Jupin-Ganglois, Sebastian, Veneziani, Marcella, Pijnacker-Hordijk, Bas, Bucci, Simone, Gostinicchi, Giacomo, Kanitz, Thomas, Straume, Anne-Grete, Ehlers, Frithjof, Wernham, Denny, Bley, Sebastian, Aprile, Stefano, De Laurentis, Marta, Parinello, Tommaso, Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), DLR Institut für Physik der Atmosphäre (IPA), Deutsches Zentrum für Luft- und Raumfahrt [Oberpfaffenhofen-Wessling] (DLR), Agence Spatiale Européenne (ESA), European Space Agency (ESA), Royal Netherlands Meteorological Institute (KNMI), European Centre for Medium-Range Weather Forecasts (ECMWF), and ESA/AEOLUS
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Earth Explorer mission ,[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,Doppler wind lidar ,13. Climate action ,[SDE.IE]Environmental Sciences/Environmental Engineering ,sattelite ,wind ,7. Clean energy ,Aeolus ,lidar - Abstract
The European Space Agency (ESA)’s Earth Explorer Aeolus was launched in August 2018 carrying the world’s first spaceborne wind lidar, the Atmospheric Laser Doppler Instrument (ALADIN). ALADIN uses a high spectral resolution Doppler wind lidar operating at 355nm to determine profiles of line-of-sight wind components in near-real-time (NRT). ALADIN samples the atmosphere from 30km altitude down to the Earth’s surface or to the level where the lidar signal is attenuated by optically thick clouds.The global wind profiles provided by ALADIN help to improve weather forecasting and the understanding of atmospheric dynamics as they fill observational gaps in vertically resolved wind profiles mainly in the tropics, southern hemisphere, and over the northern hemisphere oceans. Since 2020, multiple national and international weather centres (e.g. ECMWF, DWD, Météo France, MetOffice) assimilate Aeolus observations in their operational forecasting. Additionally, the scientific exploitation of the Aeolus dataset has started.A main prerequisite for beneficial impact and scientific exploitation is data of sufficient quality. Such high data quality has been achieved through close collaboration of all involved parties within the Aeolus Data Innovation and Science Cluster (DISC), which was established after launch to study and improve the data quality of Aeolus products. The tasks of the Aeolus DISC include the instrument and platform monitoring, calibration, characterization, retrieval algorithm refinement, processor evolution, quality monitoring, product validation, and impact assessment for NWP.The achievements of the Aeolus DISC for the NRT data quality and the one currently available reprocessed dataset will be presented. The data quality of the Aeolus wind measurements will be described and an outlook on planned improvements of the dataset and processors will be provided.
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- 2021
11. The Joint Aeolus Tropical Atlantic Campaign - First Results for Aeolus Calibration/Validation and Science in the Tropics
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Skofronick-Jackson, Gail, Fehr, Thorsten, Althausen, Dietrich, Amiridis, Vassilis, Baars, Holger, von Bismarck, Jonas, Borne, Maurus, Casal, Tânia, Cazenave, Quitterie, Chen, Shuyi, Engelmann, Ronny, Flamant, Cyrille, Gaetani, Marco, Geiß, Alexander, Gómez Maqueo Anaya, Sofia, Knipperz, Peter, Kollias, Pavlos, Koopman, Rob, Krisna, Trismono, Lemmerz, Christian, Lux, Oliver, Marinou, Eleni, Marksteiner, Uwe, Močnik, Griša, Nemuc, Anca, Parrinello, Tommaso, Paschou, Peristera, Piña, Aaron, Pirloaga, Razvan, Rahm, Stephan, Reitebuch, Oliver, Schäfler, Andreas, Siomos, Nikos, Skupin, Annett, Straume, Anne, Tran, Viet, Vaziri, Pouya, Wandinger, Ulla, Wehr, Tobias, Weiler, Fabian, Wernham, Denny, Witschas, Benjamin, Zenk, Cordula, Cardon, Catherine, NASA Science Mission Directorate (SMD), NASA, European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Leibniz Institute for Tropospheric Research (TROPOS), Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing [Penteli] (IAASARS), National Observatory of Athens (NOA), European Space Research Institute (ESRIN), Karlsruhe Institute of Technology (KIT), TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Department of Atmospheric Sciences [Seattle], University of Washington [Seattle], Istituto Universitario di Studi Superiori (IUSS), DLR Institut für Physik der Atmosphäre (IPA), Deutsches Zentrum für Luft- und Raumfahrt [Oberpfaffenhofen-Wessling] (DLR), University of Nova Gorica, National Institute of Research and Development for Optoelectronics (INOE), Agence Spatiale Européenne (ESA), and Helmholtz Centre for Ocean Research [Kiel] (GEOMAR)
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[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] ,[PHYS.PHYS.PHYS-AO-PH] Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] - Abstract
International audience; ESA’s Aeolus satellite observations are expected to have the biggest impact for the improvement of numerical weather prediction in the Tropics. An especially important case relating to the evolution, dynamics, and predictability of tropical weather systems is the outflow of Saharan dust, its interaction with cloud microphysics and impact on the development of tropical storms over the Atlantic Ocean. The Atlantic Ocean off the coast of West Africa and the eastern Caribbean uniquely allows the study of the Saharan Aerosol layer, African Easterly Waves and Jet, Tropical Easterly Jet, as well as the deep convection in the Intertropical Convergence Zone and their relation to the formation of convective systems, and the long-range transport of dust and its impact on air quality. The Joint Aeolus Tropical Atlantic Campaign (JATAC) deployed on Cabo Verde and the US Virgin Islands is addressing the validation and preparation of the ESA missions Aeolus, EarthCARE and WIVERN, as well as supporting the related science objectives raised above. The JATAC campaign started in July 2021 with the deployment of ground-based instruments at the Ocean Science Center Mindelo (OSCM, Cabo Verde), including the EVE lidar, the PollyXT lidar, a W-band Doppler cloud radar and a sunphotometer. By mid-August, the CPEX-AW campaign started their operations from the US Virgin Islands with NASA’s DC-8 flying laboratory in the Western Tropical Atlantic and Caribbean with the Doppler Aerosol Wind Lidar (DAWN), Airborne Precipitation and Cloud Radar (APR-3), the Water Vapor DIAL and HSRL (HALO), a microwave sounder (HAMSR) and dropsondes. In September, a European aircraft fleet was deployed to Sal (Cabo Verde) with the DLR Falcon-20 carrying the Aeolus Airborne Demonstrator (A2D) and the 2-µm Doppler wind lidar, and the Safire Falcon-20 carrying the high-spectral-resolution Doppler lidar (LNG), the RASTA Doppler cloud radar, in-situ cloud and aerosol instruments among others. The Aerovizija Advantic WT-10 light aircraft with filter-photometers and nephelometers for in-situ aerosol characterisation was operating in close coordination with the ground-based observations from Mindelo. More than 35 flights of the four aircraft were performed. 17 Aeolus orbits were underflown, four of which completed by simultaneous observations of three aircraft, with a perfect collocation of Aeolus and the ground-based observation for two cases. Several flights by the NASA DC-8 and the Safire Falcon-20 have been dedicated to cloud microphysics and dust events. The EVE lidar has been operating on a regular basis, while the PollyXT and several other ground-based instruments were continuously operating during the campaign period. For further characterisation of the atmosphere, radiosondes were launched up to twice daily from Sal airport. Additionally, there were radiosonde launches from western Puerto Rico and northern St Croix, US Virgin Islands. The JATAC was supported by dedicated numerical weather and dust simulations supporting the forecasting efforts needed for successful planning of the flights and addressing open science questions. While the airborne activities were completed end September, the ground-based observations are continuing into 2022. The paper will present an overview and initial results of JATAC. In memory of our colleague and friend Gail.
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- 2021
12. Retrieval improvements for the ALADIN Airborne Demonstrator in support of the Aeolus wind product validation.
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Lux, Oliver, Lemmerz, Christian, Weiler, Fabian, Marksteiner, Uwe, Witschas, Benjamin, Rahm, Stephan, Geiß, Alexander, Schäfler, Andreas, and Reitebuch, Oliver
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DOPPLER lidar ,BACKSCATTERING ,ARTIFICIAL satellite launching ,WIND speed ,QUALITY control ,TELECOMMUNICATION satellites - Abstract
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 Doppler wind lidar (DWL) in space. However, the validation capabilities of the A2D are compromised by deficiencies of the dual-channel receiver which, like its spaceborne counterpart, consists of a Rayleigh and a complementary Mie spectrometer for sensing the wind speed from both molecular and particulate backscatter signals, respectively. Whereas the accuracy and precision of the Rayleigh channel is limited by the spectrometer's high alignment sensitivity, especially in the near field of the instrument, large systematic Mie wind errors are caused by aberrations of the interferometer in combination with the temporal overlap of adjacent range gates during signal readout. The two error sources are mitigated by modifications of the A2D wind retrieval algorithm. A novel quality control scheme was implemented, which ensures that only backscatter return signals within a small angular range are further processed. Moreover, Mie wind results with large bias of opposing sign in adjacent range bins are vertically averaged. The resulting improvement of the A2D performance was evaluated in the context of two Aeolus airborne validation campaigns that were conducted between May and September 2019. Comparison of the A2D wind data against a high-accuracy, coherent DWL that was deployed in parallel on board the same aircraft shows that the retrieval refinements considerably decrease the random errors of the A2D line-of-sight (LOS) Rayleigh and Mie winds from about 2.0 to about 1.5 m s -1 , demonstrating the capability of such a direct detection DWL. Furthermore, the measurement range of the Rayleigh channel could be largely extended by up to 2 km in the instrument's near field close to the aircraft. The Rayleigh and Mie systematic errors are below 0.5 m s -1 (LOS), hence allowing for an accurate assessment of the Aeolus wind errors during the September campaign. The latter revealed different biases of the Level 2B (L2B) Rayleigh-clear and Mie-cloudy horizontal LOS (HLOS) winds for ascending and descending orbits, as well as random errors of about 3 m s -1 (HLOS) for the Mie and close to 6 m s -1 (HLOS) for the Rayleigh winds, respectively. In addition to the Aeolus error evaluation, the present study discusses the applicability of the developed A2D algorithm modifications to the Aeolus processor, thereby offering prospects for improving the Aeolus wind data quality. [ABSTRACT FROM AUTHOR]
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- 2022
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13. Aeolus Validation With the 2-µm Coherent and the ALADIN Airborne Demonstrator Doppler Wind Lidars On-board the DLR Falcon
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Lemmerz, Christian, Lux, Oliver, Witschas, Benjamin, Rahm, Stephan, Geiss, Alexander, Marksteiner, Uwe, Schäfler, Andreas, Weiler, Fabian, Reitebuch, Oliver, and Fehr, Thorsten
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Lidar ,Doppler Wind Lidar ,Airborne Validation ,ALADIN ,2-µm DWL ,ALADIN Airborne Demonstrator ,Aeolus ,A2D - Published
- 2020
14. Retrieval improvements for the ALADIN Airborne Demonstrator in support of the Aeolus wind product validation.
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Lux, Oliver, Lemmerz, Christian, Weiler, Fabian, Marksteiner, Uwe, Witschas, Benjamin, Rahm, Stephan, Geiß, Alexander, Schäfler, Andreas, and Reitebuch, Oliver
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DOPPLER lidar ,WIND speed ,ARTIFICIAL satellite launching ,ALGORITHMS ,QUALITY control ,TELECOMMUNICATION satellites ,LASER based sensors - Abstract
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-ever Doppler wind lidar (DWL) in space. However, the validation capabilities of the A2D are compromised by deficiencies of the dual-channel receiver which, like its spaceborne counterpart, consists of a Rayleigh and a complementary Mie spectrometer for sensing the wind speed from both molecular and particulate backscatter signals, respectively. Whereas the accuracy and precision of the Rayleigh channel is limited by the spectrometer's high alignment sensitivity, especially in the near field of the instrument, large systematic Mie wind errors are caused by aberrations of the interferometer in combination with the temporal overlap of adjacent range gates during signal readout. The two error sources are mitigated by modifications of the A2D wind retrieval algorithm. A novel quality control scheme was implemented which ensures that only backscatter return signals within a small angular range are further processed. Moreover, Mie wind results with large bias of opposing sign in adjacent range bins are vertically averaged. The resulting improvement of the A2D performance was evaluated in the context of two Aeolus airborne validation campaigns that were conducted between May and September 2019. Comparison of the A2D wind data against a high-accuracy, coherent Doppler wind lidar that was deployed in parallel on-board the same aircraft shows that the retrieval refinements considerably decrease the random errors of the A2D line-of-sight (LOS) Rayleigh and Mie winds from about 2.0 m∙s
-1 to about 1.5 m∙s-1 , demonstrating the capability of such a direct detection DWL. Moreover, the measurement range of the Rayleigh channel could be largely extended by up to 2 km in the instrument's near field close to the aircraft. The Rayleigh and Mie systematic errors are below 0.5 m∙s-1 (LOS), hence allowing for an accurate assessment of the Aeolus wind errors during the September campaign. The latter revealed different biases of the L2B Rayleigh-clear and Mie-cloudy horizontal LOS (HLOS) for ascending and descending orbits as well as random errors of about 3 m∙s-1 (HLOS) for the Mie and close to 6 m∙s-1 (HLOS) for the Rayleigh winds, respectively. In addition to the Aeolus error evaluation, the present study discusses the applicability of the developed A2D algorithm modifications to the Aeolus processor, thereby offering prospects for improving the Aeolus wind data quality. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
15. Airborne Doppler wind LIDAR technology demonstration for Aeolus: from pre-launch campaigns to mission performance validation.
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Lemmerz, Christian, Lux, Oliver, Witschas, Benjamin, Rahm, Stephan, Marksteiner, Uwe, Geiß, Alexander, Weiler, Fabian, and Reitebuch, Oliver
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- 2024
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16. Validation of Aeolus winds using radiosonde observations and numerical weather prediction model equivalents.
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Martin, Anne, Weissmann, Martin, Reitebuch, Oliver, Rennie, Michael, Geiß, Alexander, and Cress, Alexander
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NUMERICAL weather forecasting ,RADIOSONDES ,PREDICTION models ,DOPPLER lidar - Abstract
In August 2018, the first Doppler wind lidar, developed by the European Space Agency (ESA), was launched on board the Aeolus satellite into space. Providing atmospheric wind profiles on a global basis, the Earth Explorer mission is expected to demonstrate improvements in the quality of numerical weather prediction (NWP). For the use of Aeolus observations in NWP data assimilation, a detailed characterization of the quality and the minimization of systematic errors is crucial. This study performs a statistical validation of Aeolus observations, using collocated radiosonde measurements and NWP forecast equivalents from two different global models, the ICOsahedral Nonhydrostatic model (ICON) of Deutscher Wetterdienst (DWD) and the European Centre for Medium-Range Weather Forecast (ECMWF) Integrated Forecast System (IFS) model, as reference data. For the time period from the satellite's launch to the end of December 2019, comparisons for the Northern Hemisphere (23.5–65 ∘ N) show strong variations of the Aeolus wind bias and differences between the ascending and descending orbit phase. The mean absolute bias for the selected validation area is found to be in the range of 1.8–2.3 ms-1 (Rayleigh) and 1.3–1.9 ms-1 (Mie), showing good agreement between the three independent reference data sets. Due to the greater representativeness errors associated with the comparisons using radiosonde observations, the random differences are larger for the validation with radiosondes compared to the model equivalent statistics. To achieve an estimate for the Aeolus instrumental error, the representativeness errors for the comparisons are determined, as well as the estimation of the model and radiosonde observational error. The resulting Aeolus error estimates are in the range of 4.1–4.4 ms-1 (Rayleigh) and 1.9–3.0 ms-1 (Mie). Investigations of the Rayleigh wind bias on a global scale show that in addition to the satellite flight direction and seasonal differences, the systematic differences vary with latitude. A latitude-based bias correction approach is able to reduce the bias, but a residual bias of 0.4–0.6 ms-1 with a temporal trend remains. Taking additional longitudinal differences into account, the bias can be reduced further by almost 50 %. Longitudinal variations are suggested to be linked to land–sea distribution and tropical convection that influences the thermal emission of the earth. Since 20 April 2020 a telescope temperature-based bias correction scheme has been applied operationally in the L2B processor, developed by the Aeolus Data Innovation and Science Cluster (DISC). [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
17. Initial Assessment of the Performance of the First Wind Lidar in Space on Aeolus.
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Liu, D., Wang, Y., Wu, Y., Gross, B., Moshary, F., Reitebuch, Oliver, Lemmerz, Christian, Lux, Oliver, Marksteiner, Uwe, Rahm, Stephan, Weiler, Fabian, Witschas, Benjamin, Meringer, Markus, Schmidt, Karsten, Huber, Dorit, Nikolaus, Ines, Geiss, Alexander, Vaughan, Michael, Dabas, Alain, and Flament, Thomas
- Subjects
LIDAR ,THEORY of knowledge ,NUMERICAL weather forecasting ,DASSAULT Falcon (Jet transport) ,AIRCRAFT industry ,MEASUREMENT errors - Abstract
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 numerical weather prediction (NWP) by measuring one component of the horizontal wind vector. The performance of the ALADIN instrument was assessed by a team from ESA, DLR, industry, and NWP centers during the first months of operation. The current knowledge about the main contributors to the random and systematic errors from the instrument will be discussed. First validation results from an airborne campaign with two wind lidars on-board the DLR Falcon aircraft will be shown. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
18. First Results from the German Cal/Val Activities for Aeolus.
- Author
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Liu, D., Wang, Y., Wu, Y., Gross, B., Moshary, F., Baars, Holger, Geiß, Alexander, Wandinger, Ulla, Herzog, Alina, Engelmann, Ronny, Bühl, Johannes, Radenz, Martin, Seifert, Patric, Ansmann, Albert, Martin, Anne, Leinweber, Ronny, Lehmann, Volker, Weissmann, Martin, Cress, Alexander, and Filioglou, Maria
- Subjects
AEROSOLS ,LIDAR ,DOPPLER effect ,OPTICAL properties - Abstract
On 22nd August 2018, the European Space Agency (ESA) launched the first direct detection Doppler wind lidar into space. Operating at 355 nm and acquiring signals with a dual channel receiver, it allows wind observations in clear air and particle-laden regions of the atmosphere. Furthermore, particle optical properties can be obtained using the High Spectral Resolution Technique Lidar (HSRL) technique. Measuring with 87 km horizontal and 0.25-2 km vertical resolution between ground and up to 30 km in the stratosphere, the global coverage of Aeolus observations shall fill gaps in the global observing system and thus help improving numerical weather prediction. Within this contribution, first results from the German initiative for experimental Aeolus validation are presented and discussed. Ground-based wind and aerosol measurements from tropospheric radar wind profilers, Doppler wind lidars, radiosondes, aerosol lidars and cloud radars are utilized for that purpose. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
19. Validation of Aeolus winds using radiosonde observations and NWP model equivalents.
- Author
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Martin, Anne, Weissmann, Martin, Reitebuch, Oliver, Rennie, Michael, Geiß, Alexander, and Cress, Alexander
- Subjects
NUMERICAL weather forecasting ,RADIOSONDES ,DOPPLER lidar - Abstract
In August 2018, the first Doppler Wind Lidar, developed by the European Space Agency (ESA), was launched on board the Aeolus satellite into space. Providing atmospheric wind profiles on a global basis, the Earth Explorer mission is expected to demonstrate improvements in the quality of numerical weather prediction (NWP). For the use of Aeolus observations in NWP data assimilation, a detailed characterization of the quality and the minimization of systematic errors is crucial. This study performs a statistical validation of Aeolus observations, using collocated radiosonde measurements and NWP forecast equivalents from two different global models, the ICOsahedral Nonhydrostatic model (ICON) of Deutscher Wetterdienst (DWD) and the European Centre for Medium-Range Weather Forecast (ECMWF) Integrated Forecast System (IFS) model, as reference data. For the time period from the satellite's launch to the end of December 2019, comparisons for the northern hemisphere (23.5-65° N) show strong variations of the Aeolus winds bias and differences between the ascending and descending orbit phase. The mean absolute bias for the selected validation area is found to be in the range of 1.8-2.3 m s
-1 (Rayleigh) and 1.3-1.9 m s-1 (Mie), showing good agreement between the independent reference data sets. Due to lower representativeness, the random differences are larger for the validation using radiosonde observations compared to the model equivalent statistics. To achieve an estimate for the Aeolus instrumental error, the representativeness errors for the comparisons are determined, besides the estimation of the model and radiosonde observational error. The resulting Aeolus errors estimates are in the range of 4.1-4.4 m s-1 (Rayleigh) and 1.9-3.0 m s-1 (Mie). Investigations of the Rayleigh wind bias on a global scale show that in addition to the satellite flight direction and seasonal differences, the systematic differences depend on latitude. A latitude based bias correction approach is able to reduce the bias, but a residual bias of 0.4-0.6 m s-1 with a temporal trend remains. Taking additional longitudinal differences into account, the bias can be reduced further by almost 50 %. Longitudinal variations are suggested to be linked to land-sea distribution and tropical convection that influences the thermal emission of the earth. Since 20 April 2020 a bias correction scheme has been applied operationally in the L2B processor, developed by the Aeolus Data Innovation and Science Cluster (DISC). [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
20. On the spatial variability of the regional aerosol distribution as determined from ceilometers.
- Author
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Wiegner, Matthias, Geiß, Alexander, Mattis, Ina, Meier, Fred, and Ruhtz, Thomas
- Abstract
Measurements of the vertical distribution of aerosol particles are typically only available at selected sites leaving the question of their representativeness for urban and regional scales unanswered. As a contribution to solve this problem we have investigated ceilometer signals from two testbeds in Munich and Berlin, Germany. For each testbed measurements of 24 months from 6 ceilometers were available. This constitutes a unique data set, in particular as the same type of instruments are deployed and the same data evaluation schemes applied. Two parameters are discussed: the mixing layer height (MLH) as an indicator for the vertical distribution and the integrated backscatter as a proxy for the amount of aerosols in the mixing layer. The MLH was determined by the COBOLT algorithm, the integrated backscatter from the Klett (backward and forward) inversion scheme. It was found that the mean difference of the MLH at two sites within a testbed typically only varies by less than 50 m, slightly increasing with the distance of the corresponding sites. Almost 60 % of all intercomparisons agree within ±100 m. MLHs are typically correlated with R > 0.9 in particular for the Berlin-testbed. With respect to the integrated backscatter the correlation is in the range of 0.7 < R < 0.9. This is expected from the diversity of local aerosol sources within a given testbed. We conclude from our data that the MLH determined from a single ceilometer is applicable for a whole metropolitan area. However, the integrated backscatter of particles within the mixing layer exhibits a variability of 15-25 % suggesting that one ceilometer is not representative, especially if atmospheric processes shall be investigated. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
21. First validation of Aeolus wind observations by airborne Doppler wind lidar measurements.
- Author
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Witschas, Benjamin, Lemmerz, Christian, Geiß, Alexander, Lux, Oliver, Marksteiner, Uwe, Rahm, Stephan, Reitebuch, Oliver, and Weiler, Fabian
- Subjects
DOPPLER lidar ,WIND measurement ,LIDAR - 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 Center (Deutsches Zentrum für Luft- und Raumfahrt e.V., DLR) recently performed two airborne campaigns over central Europe deploying two different Doppler wind lidars (DWLs) on board the DLR Falcon aircraft. The first campaign – WindVal III – was conducted from 5 November 2018 until 5 December 2018 and thus still within the commissioning phase of the Aeolus mission. The second campaign – AVATARE (Aeolus Validation Through Airborne Lidars in Europe) – was performed from 6 May 2019 until 6 June 2019. Both campaigns were flown out of the DLR site in Oberpfaffenhofen, Germany, during the evening hours for probing the ascending orbits. All together, 10 satellite underflights with 19 flight legs covering more than 7500 km of Aeolus swaths were performed and used to validate the early-stage wind data product of Aeolus by means of collocated airborne wind lidar observations for the first time. For both campaign data sets, the statistical comparison of Aeolus horizontal line-of-sight (HLOS) observations and the corresponding wind observations of the reference lidar (2 µm DWL) on board the Falcon aircraft shows enhanced systematic and random errors compared with the bias and precision requirements defined for Aeolus. In particular, the systematic errors are determined to be 2.1 m s -1 (Rayleigh) and 2.3 m s -1 (Mie) for WindVal III and -4.6 m s -1 (Rayleigh) and -0.2 m s -1 (Mie) for AVATARE. The corresponding random errors are determined to be 3.9 m s -1 (Rayleigh) and 2.0 m s -1 (Mie) for WindVal III and 4.3 m s -1 (Rayleigh) and 2.0 m s -1 (Mie) for AVATARE. The Aeolus observations used here were acquired in an altitude range up to 10 km and have mainly a vertical resolution of 1 km (Rayleigh) and 0.5 to 1.0 km (Mie) and a horizontal resolution of 90 km (Rayleigh) and down to 10 km (Mie). Potential reasons for those errors are analyzed and discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
22. Intercomparison of wind observations from the European Space Agency's Aeolus satellite mission and the ALADIN Airborne Demonstrator.
- Author
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Lux, Oliver, Lemmerz, Christian, Weiler, Fabian, Marksteiner, Uwe, Witschas, Benjamin, Rahm, Stephan, Geiß, Alexander, and Reitebuch, Oliver
- Subjects
WIND measurement ,DOPPLER lidar ,ARTIFICIAL satellites ,WIND speed ,STANDARD deviations - Abstract
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 wind lidar on-board Aeolus, the A2D is composed of a frequency-stabilized ultra-violet (UV) laser, a Cassegrain telescope and a dual-channel receiver to measure line-of-sight (LOS) wind speeds by analysing both Mie and Rayleigh backscatter signals. In the framework of the first airborne validation campaign after the launch and still during the commissioning phase of the mission, four coordinated flights along the satellite swath were conducted in late autumn of 2018, yielding wind data in the troposphere with high coverage of the Rayleigh channel. Owing to the different measurement grids and LOS viewing directions of the satellite and the airborne instrument, intercomparison with the Aeolus wind product requires adequate averaging as well as conversion of the measured A2D LOS wind speeds to the satellite LOS (LOS*). The statistical comparison of the two instruments shows a positive bias (of 2.6 m s -1) of the Aeolus Rayleigh winds (measured along its LOS*) with respect to the A2D Rayleigh winds as well as a standard deviation of 3.6 m s -1. Considering the accuracy and precision of the A2D wind data, which were determined from comparison with a highly accurate coherent wind lidar as well as with the European Centre for Medium-Range Weather Forecasts (ECMWF) model winds, the systematic and random errors of the Aeolus LOS* Rayleigh winds are 1.7 and 2.5 m s -1 respectively. The paper also discusses the influence of different threshold parameters implemented in the comparison algorithm as well as an optimization of the A2D vertical sampling to be used in forthcoming validation campaigns. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
23. Intercomparison of wind observations from ESA's satellite mission Aeolus and the ALADIN Airborne Demonstrator.
- Author
-
Lux, Oliver, Lemmerz, Christian, Weiler, Fabian, Marksteiner, Uwe, Witschas, Benjamin, Rahm, Stephan, Geiss, Alexander, and Reitebuch, Oliver
- Subjects
WIND measurement ,DOPPLER lidar ,WIND instruments ,WIND speed ,ARTIFICIAL satellites ,PROCESS optimization - Abstract
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 is composed of a frequency-stabilised ultra-violet laser, a Cassegrain telescope and a dual-channel receiver to measure line-of-sight (LOS) wind speeds by analysing both Mie and Rayleigh backscatter signals. In the frame of the first airborne validation campaign after the launch still during the commissioning phase of the mission, four coordinated flights along the satellite swath were conducted in late autumn of 2018, yielding wind data in the troposphere with high coverage of the Rayleigh channel. Owing to the different measurement grids and viewing directions of the satellite and airborne instrument, intercomparison with the Aeolus wind product requires adequate averaging as well as conversion of the measured A2D LOS wind speeds to the satellite LOS. The statistical comparison of the two instruments with model wind data from the ECMWF shows biases of the A2D and Aeolus LOS wind speeds of
-1 0.9 m s-1 and +1.6 m s-1 , respectively, while the random errors are around 2.5 m s-1 . The paper also discusses the influence of different threshold parameters implemented in the comparison algorithm as well as optimization of the A2D vertical sampling to be used in forthcoming validation campaigns. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
24. Automated calibration of ceilometer data and its applicability for quantitative aerosol monitoring
- Author
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Geiß, Alexander
- Subjects
FOS: Physical sciences - Abstract
Aerosols are important constituents of the Earth’s atmosphere. Their impact on global climate, but also on air quality and hence human health is huge. A region were pollutants can disperse is the Mixing Layer (ML), the lowermost part of the Earth’s atmosphere. It’s thickness is directly influenced from the Earth’s surface. The physics of the ML is of great interest for the meteorological community as effects on the dynamics, thermodynamics and air quality of the atmosphere are crucial. Recently, networks of automated single-wavelength backscatter lidars (“ceilometers”) have been implemented, primarily by weather services. As a consequence, the potential of ceilometers to quantitatively determine the spatio-temporal distribution of atmospheric aerosols must be investigated. With regard to ceilometer networks, automatic mixing layer height retrievals for air quality studies and a fully automated calibration of ceilometers to derive aerosol optical properties is required. The absolute calibration approach, which is based on the determination of the lidar constant C_L was fully automated and is applicable in a three-step procedure to several ceilometer types. As a result, the particle backscatter coefficient β_p can be determined at virtually any weather condition during day and night, independent of the main ceilometer issue—the limited signal-to-noise ratio. Applied to 5 years of measurement of a Jenoptik CHM15kx, a lidar constant could be determined on 391 days out of 1900 available days. With knowing C_L, β_p-profiles within an accuracy of typically 17% can be derived. To allow investigations of the ML, the automatic ML-height retrieval algorithm COBOLT (Continuous Boundary Layer Tracing) was developed. In contrast to ML-cycles with large jumps or even temporal gaps, determined by already available and frequently used algorithms, COBOLT uses a time-height tracking procedure. On basis of a best-of-all-approach utilizing state-of-the-art layer detection techniques, a traceable parameter is defined and allows to detect complete diurnal ML-cycles without steps by including a multi-member approach. Validation and crosschecks with ML-heights from radiosonde data and two other ML-height retrieval algorithms demonstrated the reliability of COBOLT. A wide range of applications is possible with a calibrated ceilometer and a reliable ML-height retrieval algorithm. Following examples are shown: a β_p-profile statistic and ML-height statistic above Munich; ML-height comparisons between rural and an urban site, as well as a validation of a chemistry transport model and an investigation of ML-height influences on air quality., Aerosolpartikel sind ein wichtiger Bestandteil der Erdatmosphäre. Sie haben Einfluss auf das globale Klima, aber auch auf die Luftqualität und somit letztlich auch auf die menschliche Gesundheit. Schadstoffe breiten sich insbesondere in der Mischungsschicht (ML) aus, dem untersten Teil der Erdatmosphäre. Die ML-Höhe wird direkt von der Erdoberfläche aus beeinflusst. Die Physik der ML ist von großem Interesse für die Meteorologie, da dynamische und thermodynamische Prozesse sowie die Zusammensetzung der Atmosphäre eine große Rolle spielen. In letzter Zeit haben vor allem Wetterdienste Netzwerke mit automatisierten Rückstreulidargeräten mit einer Wellenlänge (Ceilometer) aufgebaut. Folglich muss untersucht werden, welches Potential Ceilometer bei der quantitativen Bestimmung der räumlichen sowie zeitlichen Aerosolverteilung in der Atmosphäre haben. Im Hinblick auf Ceilometernetzwerke ist die Entwicklung einer automatischen Bestimmung der ML-Höhe für Untersuchungen der Luftqualität und eine automatisierte Kalibrierung der Ceilometer nötig. Erst mit einer automatisierten Kalibrierung kann man optische Eigenschaften anhand von Ceilometernetzwerken ableiten. Es ist gelungen die hier entwickelte absolute Kalibrierung, welche auf der Bestimmung der Lidarkonstante C_L basiert, vollständig zu automatisieren. Sie kann in einem dreistufigen Verfahren auf verschiedenste Ceilometer angewendet werden. Dadurch kann man den Partikelrückstreukoeffizienten β_p unabhängig vom Signal-Rausch-Verhältnis, dem größten Problem der Ceilometer, bei fast allen Wetterbedingungen sowohl bei Tag als auch bei Nacht bestimmen. Mit der Anwendung auf eine fünfjährige Messreihe von einem Jenoptik CHM15kx lässt sich eine Lidarkonstante an 391 von 1900 verfügbaren Tagen ermitteln. Unter Nutzung von C_L können β_p-Profile mit einer Genauigkeit von 17% abgeleitet werden. Um Untersuchungen der ML vorzunehmen, wird der automatische Algorithmus COBOLT (Continuous Boundary Layer Tracing) zur Bestimmung der ML-Höhe entwickelt. Im Gegensatz zu ML-Tagesgängen von häufig benutzten Algorithmen, die große Sprünge oder gar Lücken in der von ihnen bestimmten ML-Höhe aufweisen, basiert COBOLT auf einer Zeit-Höhen-Verfolgung. Auf Grundlage eines “best-of-all”-Ansatzes und unter der Verwendung aktueller Methoden zur Schichtbestimmung wird ein Parameter definiert. Dieser Parameter erlaubt unter Verwendung eines “multi-member”-Ansatzes ein Verfolgen der ML-Höhe zur Auswertung von vollständigen ML-Tagesgängen ohne Zwischenschritte. Der Vergleich und die Validierung von ML-Höhen aus Daten von Radiosonden und zwei anderen Algorithmen zur ML-Höhenbestimmung zeigen die Zuverlässigkeit von COBOLT. Die Kalibrierung von Ceilometern und der Algorithmus zur Mischungsschichthöhenbestimmung eröffnen eine Vielzahl von Anwendungsmöglichkeiten. Zu den gezeigten Beispielen gehört eine Statistik des β_p-Profils und eine Statistik der ML-Höhen über München. Dabei werden sowohl die ML-Höhen von ländlichen Gebieten mit urbanen Zentren verglichen, als auch eine Validierung von Chemietransportmodellen und eine Untersuchung des Einflusses der ML-Höhen auf die Luftqualität vorgenommen.
- Published
- 2016
- Full Text
- View/download PDF
25. Evaluation of ECMWF-IFS (version 41R1) operational model forecasts of aerosol transport by using ceilometer network measurements.
- Author
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Chan, Ka Lok, Wiegner, Matthias, Flentje, Harald, Mattis, Ina, Wagner, Frank, Gasteiger, Josef, and Geiß, Alexander
- Subjects
CEILOMETER ,STANDARD deviations ,METEOROLOGICAL services ,WEATHER forecasting ,DATA analysis - Abstract
In this paper, we present a comparison of model simulations of aerosol profiles with measurements of the ceilometer network operated by the German Weather Service (DWD) over 1 year from September 2015 to August 2016. The aerosol forecasts are produced by the Copernicus Atmosphere Monitoring Service (CAMS) using the aerosol module developed within the Global and regional Earth-system Monitoring using Satellite and in-situ data (GEMS) and Monitoring Atmospheric Composition and Climate (MACC) projects and coupled into the European Centre for Medium-Range Weather Forecasts Integrated Forecasting System (ECMWF-IFS). As the model output provides mass mixing ratios of different types of aerosol, whereas the ceilometers do not, it is necessary to determine a common physical quantity for the comparison. We have chosen the attenuated backscatter β* for this purpose. The β* profiles are calculated from the mass mixing ratios of the model output assuming the inherent aerosol microphysical properties. Comparison of the attenuated backscatter averaged between an altitude of 0.2 km (typical overlap range of ceilometers) and 1 km in general shows similar annual average values. However, the standard deviation of the difference between model and observation is larger than the average in 8 out of 12 sites. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
26. Evaluation of operational model forecasts of aerosol transport using ceilometer network measurements.
- Author
-
Ka Lok Chan, Wiegner, Mattias, Flentje, Harald, Mattis, Ina, Wagner, Frank, Gasteiger, Josef, and Geiß, Alexander
- Subjects
ATMOSPHERIC aerosol measurement ,WEATHER forecasting ,CEILOMETER - Abstract
In this paper, we present a comparison of European Centre for Medium-Range Weather Forecast Integrated Forecast System (ECMWF-IFS) model simulation of aerosol backscatter profiles with measurements of the ceilometer network operated by the German weather service (DWD) over 1 year from September 2015 to August 2016. As the model output provides mass mixing ratios of different types of aerosol whereas the ceilometers don't, it is necessary to determine a common physical quantity for the comparison. We have chosen the attenuated backscatter β* for this purpose. The β*-profiles are calculated from the mass mixing ratios of the model output assuming the inherent aerosol microphysical properties. Comparison of the attenuated backscatter, averaged between an altitude from 0.2 km (typical overlap range of ceilometers) and 1 km, showed slightly larger values from the model. To investigate possible reasons for the differences, we have examined the role of the hygroscopic growth of particles and the particle shape. Our results show that using a more recent particle growth model would result in a ~ 22 % reduction of particle backscatter for sea salt aerosols, corresponding to a 10 %-reduction of the total backscatter signal on average. Accounting for non-spherical dust particles in the model would reduce attenuated backscatter of dust particles by ~ 30 %. As the concentration of dust aerosol is in general very low in Germany, a significant effect on the total backscatter signal is restricted to dust episodes. In summary, consideration of both effects tend to improve the agreement between model and observations, but without leading to a perfect consistency. In addition a case study was conducted to investigate the agreement of the spatiotemporal distribution of particles. It was found that for a dust episode in April 2016 the arrival time of the dust layer and its vertical extent very well agree between model and ceilometer measurements for several stations. However, due to the large set of parameters characterizing the aerosol distribution and the complexity of the ceilometer retrieval an automated and quantitative comparison scheme for β*-profiles is still missing. Consequently, the representativeness of the case study remains open. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
27. Mixing layer height as an indicator for urban air quality?
- Author
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Geiß, Alexander, Wiegner, Matthias, Bonn, Boris, Schäfer, Klaus, Forkel, Renate, von Schneidemesser, Erika, Münkel, Christoph, Ka Lok Chan, and Nothard, Rainer
- Subjects
- *
ENVIRONMENTAL indicators , *AIR quality , *ATMOSPHERIC turbulence , *ATMOSPHERIC boundary layer , *CEILOMETER - Published
- 2017
- Full Text
- View/download PDF
28. Aerosol remote sensing by means of ceilometer measurements: treatment of water vapor absorption.
- Author
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Wiegner, Matthias, Mattis, Ina, Pattantyús-Ábrahám, Margit, Gasteiger, Josef, Geiß, Alexander, and Görsdorf, Ulrich
- Published
- 2019
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