3D wind vectors measurement with remotely piloted aircraft system for aerosol-cloud interaction study

The European project BACCHUS (impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) focuses on aerosol-cloud interactions. Vertical wind velocities near cloud base, and cloud condensation nuclei (CCN) spectra, are the two most important input parameters for aerosol-cloud parcel models in determining cloud microphysical and optical properties. Therefore, the present study focuses on the instrumental development for vertical wind measurements to improve aerosol-cloud closure studies. Enhancements in Remotely Piloted Aircraft Systems (RPAS) have demonstrated their potential as tools in atmospheric research to study the boundary layer dynamics, aerosols and clouds. However, as a relatively new tool for atmospheric research, RPA require instrumental development and validation to address current observational needs. A 5-hole probe is implemented on a remotely piloted aircraft (RPA) platform, with an inertial navigation system (INS) to obtain atmospheric wind vectors. The 5- hole probe is first calibrated in a wind tunnel (at Météo-France, Toulouse, France), and an error analysis is conducted on the vertical wind measurement. Atmospheric wind vectors obtained from RPA flights are compared with wind vectors determined from sonic anemometers located at different levels on a 60 m meteorological mast (Centre de Recherches Atmosphériques, Lannemezan, France). Good agreements between vertical wind velocity probability density functions are obtained. The power spectral density of the three wind components follow the -5/3 line for the established regime of turbulence (Kolmogorov law). Turbulent kinetic energy (TKE) values calculated from the RPA are somewhat higher than TKE compared to the sonic anemometer; however, the results agree with those reported in other experiments that compare RPA platforms and sonic anemometers (Lampert et al. (2016), Båserud et al. (2016)). As the RPA equipped with a 5-hole probe (defined as the ``wind-RPA'') is developed for aerosol-cloud observations, updraft velocities near cloud base are compared with cloud radar data during a BACCHUS field campaign (Mace Head Research Station, Ireland). Three case studies illustrate the similarity of in-cloud updrafts measured between the wind-RPA and the cloud radar. A good agreement between vertical velocities of both instruments over a range of different meteorological conditions is found. Updraft velocity measurements from the wind-RPA are implemented in the aerosol-cloud parcel model to conduct a closure study for stratocumulus case with convection sampled during a BACCHUS field campaign in Cyprus. Aerosol size distributions and CCN were measured at a ground-site, which served as input to the aerosol-cloud parcel model along with the updraft velocities at cloud base measured by the RPA. In addition, the RPA conducted a vertical profile through the cloud layer and measured the shortwave transmission of solar irradiance during the ascent. The aerosol-cloud parcel model also shows that entrainment has a greater impact on cloud optical properties than variability in updraft velocity and aerosol particle concentration. Results of the case study for the Cyprus field experiment are consistent with results for similar closure studies conducted during the Mace Head field campaign (Sanchez et al., 2017), and reinforce the significance of including entrainment processes in cloud models to reduce uncertainties in aerosol-cloud interactions

Overview of the MOSAiC expedition: Snow and sea ice

Year-round observations of the physical snow and ice properties and processes that govern the ice pack evolution and its interaction with the atmosphere and the ocean were conducted during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition of the research vessel Polarstern in the Arctic Ocean from October 2019 to September 2020. This work was embedded into the interdisciplinary design of the 5 MOSAiC teams, studying the atmosphere, the sea ice, the ocean, the ecosystem, and biogeochemical processes. The overall aim of the snow and sea ice observations during MOSAiC was to characterize the physical properties of the snow and ice cover comprehensively in the central Arctic over an entire annual cycle. This objective was achieved by detailed observations of physical properties and of energy and mass balance of snow and ice. By studying snow and sea ice dynamics over nested spatial scales from centimeters to tens of kilometers, the variability across scales can be considered. On-ice observations of in situ and remote sensing properties of the different surface types over all seasons will help to improve numerical process and climate models and to establish and validate novel satellite remote sensing methods; the linkages to accompanying airborne measurements, satellite observations, and results of numerical models are discussed. We found large spatial variabilities of snow metamorphism and thermal regimes impacting sea ice growth. We conclude that the highly variable snow cover needs to be considered in more detail (in observations, remote sensing, and models) to better understand snow-related feedback processes. The ice pack revealed rapid transformations and motions along the drift in all seasons. The number of coupled ice&ndash;ocean interface processes observed in detail are expected to guide upcoming research with respect to the changing Arctic sea ice. &nbsp;</p

Overview of the MOSAiC expedition: Physical oceanography

Arctic Ocean properties and processes are highly relevant to the regional and global coupled climate system, yet still scarcely observed, especially in winter. Team OCEAN conducted a full year of physical oceanography observations as part of the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC), a drift with the Arctic sea ice from October 2019 to September 2020. An international team designed and implemented the program to characterize the Arctic Ocean system in unprecedented detail, from the seafloor to the air-sea ice-ocean interface, from sub-mesoscales to pan-Arctic. The oceanographic measurements were coordinated with the other teams to explore the ocean physics and linkages to the climate and ecosystem. This paper introduces the major components of the physical oceanography program and complements the other team overviews of the MOSAiC observational program. Team OCEAN&rsquo;s sampling strategy was designed around hydrographic ship-, ice- and autonomous platform-based measurements to improve the understanding of regional circulation and mixing processes. Measurements were carried out both routinely, with a regular schedule, and in response to storms or opening leads. Here we present along-drift time series of hydrographic properties, allowing insights into the seasonal and regional evolution of the water column from winter in the Laptev Sea to early summer in Fram Strait: freshening of the surface, deepening of the mixed layer, increase in temperature and salinity of the Atlantic Water. We also highlight the presence of Canada Basin deep water intrusions and a surface meltwater layer in leads. MOSAiC most likely was the most comprehensive program ever conducted over the ice-covered Arctic Ocean. While data analysis and interpretation are ongoing, the acquired datasets will support a wide range of physical oceanography and multi-disciplinary research. They will provide a significant foundation for assessing and advancing modeling capabilities in the Arctic Ocean. &nbsp;</p

Observing the Central Arctic Atmosphere and Surface with University of Colorado uncrewed aircraft systems

AbstractOver a five-month time window between March and July 2020, scientists deployed two small uncrewed aircraft systems (sUAS) to the central Arctic Ocean as part of legs three and four of the MOSAiC expedition. These sUAS were flown to measure the thermodynamic and kinematic state of the lower atmosphere, including collecting information on temperature, pressure, humidity and winds between the surface and 1 km, as well as to document ice properties, including albedo, melt pond fraction, and open water amounts. The atmospheric state flights were primarily conducted by the DataHawk2 sUAS, which was operated primarily in a profiling manner, while the surface property flights were conducted using the HELiX sUAS, which flew grid patterns, profiles, and hover flights. In total, over 120 flights were conducted and over 48 flight hours of data were collected, sampling conditions that included temperatures as low as −35 °C and as warm as 15 °C, spanning the summer melt season.</jats:p

Measurements from the University of Colorado RAAVEN Uncrewed Aircraft System during ATOMIC

Between 24&nbsp;January and 15&nbsp;February 2020, small uncrewed aircraft systems (sUASs) were deployed to Morgan Lewis (Barbados) as part of the Atlantic Tradewind Ocean&ndash;Atmosphere Mesoscale Interaction Campaign (ATOMIC), a sister project to the ElUcidating the RolE of Cloud-Circulation Coupling in ClimAte (EUREC4A) project. The observations from ATOMIC and EUREC4A were aimed at improving our understanding of trade-wind cumulus clouds and the environmental regimes supporting them and involved the deployment of a wide variety of observational assets, including aircraft, ships, surface-based systems, and profilers. The current paper describes ATOMIC observations obtained using the University of Colorado Boulder RAAVEN (Robust Autonomous Aerial Vehicle&nbsp;&ndash; Endurant Nimble) sUAS. This platform collected nearly 80&thinsp;h of data throughout the lowest kilometer of the atmosphere, sampling the near-shore environment upwind from Barbados. Data from these platforms are publicly available through the National Oceanic and Atmospheric Administration's National Center for Environmental Intelligence (NCEI) archive. The primary DOI for the quality-controlled dataset described in this paper is https://doi.org/10.25921/jhnd-8e58 (de Boer et al., 2021). &nbsp;</p

Overview of the MOSAiC expedition: Snow and sea ice

Year-round observations of the physical snow and ice properties and processes that govern the ice pack evolution and its interaction with the atmosphere and the ocean were conducted during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition of the research vessel Polarstern in the Arctic Ocean from October 2019 to September 2020. This work was embedded into the interdisciplinary design of the 5 MOSAiC teams, studying the atmosphere, the sea ice, the ocean, the ecosystem, and biogeochemical processes. The overall aim of the snow and sea ice observations during MOSAiC was to characterize the physical properties of the snow and ice cover comprehensively in the central Arctic over an entire annual cycle. This objective was achieved by detailed observations of physical properties and of energy and mass balance of snow and ice. By studying snow and sea ice dynamics over nested spatial scales from centimeters to tens of kilometers, the variability across scales can be considered. On-ice observations of in situ and remote sensing properties of the different surface types over all seasons will help to improve numerical process and climate models and to establish and validate novel satellite remote sensing methods; the linkages to accompanying airborne measurements, satellite observations, and results of numerical models are discussed. We found large spatial variabilities of snow metamorphism and thermal regimes impacting sea ice growth. We conclude that the highly variable snow cover needs to be considered in more detail (in observations, remote sensing, and models) to better understand snow-related feedback processes. The ice pack revealed rapid transformations and motions along the drift in all seasons. The number of coupled ice–ocean interface processes observed in detail are expected to guide upcoming research with respect to the changing Arctic sea ice

Overview of the MOSAiC expedition - Atmosphere

With the Arctic rapidly changing, the needs to observe, understand, and model the changes are essential. To support these needs, an annual cycle of observations of atmospheric properties, processes, and interactions were made while drifting with the sea ice across the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition from October 2019 to September 2020. An international team designed and implemented the comprehensive program to document and characterize all aspects of the Arctic atmospheric system in unprecedented detail, using a variety of approaches, and across multiple scales. These measurements were coordinated with other observational teams to explore cross-cutting and coupled interactions with the Arctic Ocean, sea ice, and ecosystem through a variety of physical and biogeochemical processes. This overview outlines the breadth and complexity of the atmospheric research program, which was organized into 4 subgroups: atmospheric state, clouds and precipitation, gases and aerosols, and energy budgets. Atmospheric variability over the annual cycle revealed important influences from a persistent large-scale winter circulation pattern, leading to some storms with pressure and winds that were outside the interquartile range of past conditions suggested by long-term reanalysis. Similarly, the MOSAiC location was warmer and wetter in summer than the reanalysis climatology, in part due to its close proximity to the sea ice edge. The comprehensiveness of the observational program for characterizing and analyzing atmospheric phenomena is demonstrated via a winter case study examining air mass transitions and a summer case study examining vertical atmospheric evolution. Overall, the MOSAiC atmospheric program successfully met its objectives and was the most comprehensive atmospheric measurement program to date conducted over the Arctic sea ice. The obtained data will support a broad range of coupled-system scientific research and provide an important foundation for advancing multiscale modeling capabilities in the Arctic

Mesure du vecteur tridimensionnel du vent à partir de drones pour l'étude des interactions aérosol-nuage

Le projet européen BACCHUS (impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) porte sur les interactions aérosol-nuage. Les vitesses du vent vertical à proximité de la base des nuages et les spectres des noyaux de condensation des nuages (CCN) sont deux paramètres d'entrée importants pour les modèles de parcelle aérosol-nuage dans la détermination des propriétés microphysiques et optiques des nuages. Par conséquent, la présente étude se concentre sur le développement et la mise en oeuvre de mesures de vent atmosphérique afin d’améliorer les études de fermeture aérosolnuage. Les systèmes d'aéronefs pilotés à distance (RPAS) ont démontré leur potentiel en tant qu'outils pour la recherche atmosphérique dans l’étude de la couche limite, des aérosols et des nuages. Cependant, en tant qu'outil récent en recherche atmosphérique, le RPAS nécessite un développement instrumental pour répondre aux besoins d'observation actuels. Une sonde à 5 voies est développée pour une plateforme d'aéronef piloté à distance (RPA), assistée par un système de navigation inertiel (INS) pour obtenir les trois vecteurs du vent atmosphérique. La sonde à 5 voies est d'abord calibrée dans une soufflerie (à Météo-France, Toulouse, France), et une analyse d'erreur est effectuée sur la mesure du vent vertical. Les vecteurs de vent obtenus à partir de vols de RPA sont comparés à des vecteurs de vent déterminés à partir d'anémomètres soniques situés à différents niveaux d’un mât météorologique de 60 m (Centre de Recherches Atmosphériques, Lannemezan, France). Une bonne concordance entre les fonctions de densité de probabilité de la vitesse verticale du vent est obtenue. La densité spectrale de puissance des trois composantes du vent suit la ligne -5/3 en régime de turbulence établie (loi de Kolmogorov). Les valeurs d’énergie cinétique turbulente (TKE), calculées à partir du RPA, sont légèrement supérieures à celles de l'anémomètre sonique. Cependant, les résultats concordent avec ceux rapportés dans d'autres expériences comparant les plateformes RPAs à des anémomètres soniques (Lampert et al. (2016), Båserud et al. (2016)). Comme le RPA équipé d'une sonde à 5 voies (définie comme le ``wind-RPA'') est développé pour les observations aérosol-nuage, les vitesses verticales (updraft) près de la base des nuages sont comparées avec les données d’un radar de nuage au cours d'une campagne de mesures BACCHUS (Mace Head Research Station, Irlande). Trois études de cas illustrent la similitude des vitesses verticales dans les nuages mesurées par le wind-RPA et le radar de nuage. Une bonne concordance entre les vitesses verticales des deux instruments à travers différentes conditions météorologiques est établie. Les mesures de vitesse verticale du wind-RPA sont implémentées dans le modèle de parcelle aérosol nuage pour mener une étude de fermeture (campagne de mesures BACCHUS à Chypre). Les distributions de taille des aérosols et les CCN mesurés par un site au sol servent de paramètres d’entrée au modèle avec les vitesses verticales mesurées par le RPA. Le modèle de parcelle aérosol-nuage montre que l'entraînement dans les nuages a un impact plus important sur les propriétés optiques des nuages que la variabilité de la vitesse verticale et que la concentration en aérosols. Les résultats du cas d’étude de Chypre sont cohérents avec les résultats des études de fermeture similaires de la campagne de mesures à Mace Head (Sanchez et al., 2017) et renforcent l'importance d'inclure les processus d'entraînement dans les modèles de nuages pour réduire les incertitudes liées aux interactions aérosol-nuage.The European project BACCHUS (impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) focuses on aerosol-cloud interactions. Vertical wind velocities near cloud base, and cloud condensation nuclei (CCN) spectra, are the two most important input parameters for aerosol-cloud parcel models in determining cloud microphysical and optical properties. Therefore, the present study focuses on the instrumental development for vertical wind measurements to improve aerosol-cloud closure studies. Enhancements in Remotely Piloted Aircraft Systems (RPAS) have demonstrated their potential as tools in atmospheric research to study the boundary layer dynamics, aerosols and clouds. However, as a relatively new tool for atmospheric research, RPA require instrumental development and validation to address current observational needs. A 5-hole probe is implemented on a remotely piloted aircraft (RPA) platform, with an inertial navigation system (INS) to obtain atmospheric wind vectors. The 5- hole probe is first calibrated in a wind tunnel (at Météo-France, Toulouse, France), and an error analysis is conducted on the vertical wind measurement. Atmospheric wind vectors obtained from RPA flights are compared with wind vectors determined from sonic anemometers located at different levels on a 60 m meteorological mast (Centre de Recherches Atmosphériques, Lannemezan, France). Good agreements between vertical wind velocity probability density functions are obtained. The power spectral density of the three wind components follow the -5/3 line for the established regime of turbulence (Kolmogorov law). Turbulent kinetic energy (TKE) values calculated from the RPA are somewhat higher than TKE compared to the sonic anemometer; however, the results agree with those reported in other experiments that compare RPA platforms and sonic anemometers (Lampert et al. (2016), Båserud et al. (2016)). As the RPA equipped with a 5-hole probe (defined as the ``wind-RPA'') is developed for aerosol-cloud observations, updraft velocities near cloud base are compared with cloud radar data during a BACCHUS field campaign (Mace Head Research Station, Ireland). Three case studies illustrate the similarity of in-cloud updrafts measured between the wind-RPA and the cloud radar. A good agreement between vertical velocities of both instruments over a range of different meteorological conditions is found. Updraft velocity measurements from the wind-RPA are implemented in the aerosol-cloud parcel model to conduct a closure study for stratocumulus case with convection sampled during a BACCHUS field campaign in Cyprus. Aerosol size distributions and CCN were measured at a ground-site, which served as input to the aerosol-cloud parcel model along with the updraft velocities at cloud base measured by the RPA. In addition, the RPA conducted a vertical profile through the cloud layer and measured the shortwave transmission of solar irradiance during the ascent. The aerosol-cloud parcel model also shows that entrainment has a greater impact on cloud optical properties than variability in updraft velocity and aerosol particle concentration. Results of the case study for the Cyprus field experiment are consistent with results for similar closure studies conducted during the Mace Head field campaign (Sanchez et al., 2017), and reinforce the significance of including entrainment processes in cloud models to reduce uncertainties in aerosol-cloud interactions

La mesure des échanges air-mer par drone à grand rayon d’action pour les études des cyclones tropicaux, Météo et Climat Info

Le Centre National de Recherches Météorologiques a mené en février/mars 2019 une campagne de mesures scientifiques avec un drone BOREAL depuis l’île de La Réunion, en collaboration avec l’Université de La Réunion et le Laboratoire de l’Atmosphère et des Cyclones. Les objectifs de ces opérations aériennes étaient à la fois techniques, éprouver le système BOREAL intégré dans une zone maritime et internationale, et scientifiques, échantillonner l'atmosphère au-dessus de l'Océan Indien dans les zones de formation des cyclones pour en améliorer les prévisions.International audienc

Vertical wind velocity measurements using a five-hole probe with remotely piloted aircraft to study aerosol–cloud interactions

International audienceThe importance of 3D winds (in particular updraft) in atmospheric science has motivated the adaptation of airborne wind instruments developed for manned aircraft, to the small size of Remotely Piloted Aircraft Systems (RPAS). Simultaneously, enhancements in RPAS technology have increased their contribution to many fields. In atmospheric research, lightweight RPAS (< 2.5 kg) are now able to accurately measure 3D wind vectors, even in a cloud, which provides new observing tools for understanding aerosol-cloud interactions. The European project BACCHUS (Impact of Biogenic versus Anthropogenic Emissions on Clouds and Climate: towards a Holistic Understanding) focuses on these specific interactions. Vertical wind velocity at cloud base is a key parameter for aerosol-cloud interactions. To measure the three components of wind, one RPAS is equipped with a 5-hole probe and an Inertial Measurement Unit (IMU), synchronized on an acquisition system. The 5-hole probe is calibrated and validated on a multi-axis platform in a wind tunnel, each probe and its associated pressure sensors have specific calibration coefficients. Once mounted on a RPAS, 3D winds and turbulent kinetic energy (TKE) derived from the 5-hole probe are validated with a sonic anemometer on a meteorological mast. During the BACCHUS field campaign at Mace Head (Ireland), a fleet of RPAS has been utilized to profile the atmosphere and complement ground-based and satellite observations. To study aerosol-cloud interactions, the RPAS with the 5-hole probe flew at level legs near cloud base to measure vertical wind speeds. The vertical velocity measurements from RPAS are validated with vertical velocities derived from the Mace Head Doppler cloud radar, and the results illustrate the relationships between the distributions of vertical velocity and the different cloud fields