Service des Avions Français Instrumentés pour la Recherche en Environnement

Abstract. The science guiding the EUREC4A campaign and its measurements is presented. EUREC4A comprised roughly 5 weeks of measurements in the downstream winter trades of the North Atlantic – eastward and southeastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, EUREC4A marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or the life cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso- (200 km) and larger (500 km) scales, roughly 400 h of flight time by four heavily instrumented research aircraft; four global-class research vessels; an advanced ground-based cloud observatory; scores of autonomous observing platforms operating in the upper ocean (nearly 10 000 profiles), lower atmosphere (continuous profiling), and along the air–sea interface; a network of water stable isotopologue measurements; targeted tasking of satellite remote sensing; and modeling with a new generation of weather and climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that EUREC4A explored – from North Brazil Current rings to turbulence-induced clustering of cloud droplets and its influence on warm-rain formation – are presented along with an overview of EUREC4A's outreach activities, environmental impact, and guidelines for scientific practice. Track data for all platforms are standardized and accessible at https://doi.org/10.25326/165 (Stevens, 2021), and a film documenting the campaign is provided as a video supplement.

Author: Brands, M. et al.; Genre: Journal Article; Issued: 2011; Title: Characterization of a Newly Developed Aircraft-Based Laser Ablation Aerosol Mass Spectrometer (ALABAMA) and First Field Deployment in Urban Pollution Plumes over Paris During MEGAPOLI 2009

The CarboEurope Regional Experiment Strategy (CERES) experiment took place in May and June 2005 in France and offers a comprehensive database on atmospheric CO 2 and boundary layer processes at the regional scale. One “golden” day of CERES is interpreted with the mesoscale atmospheric model Meso‐NH coupled on‐line with the Interactions between Soil, Biosphere and Atmosphere, CO 2 ‐reactive (ISBA‐A‐gs) surface scheme, allowing a full interaction of CO 2 between the surface and the atmosphere. The rapid diurnal cycle of carbon coupled with water and energy fluxes is parameterized including, e.g., plant assimilation, respiration, anthropogenic emissions, and sea fluxes. During the analyzed day, frequent vertical profiles and aircraft transects revealed high spatial and temporal variabilities of CO 2 concentrations within the boundary layer at the regional scale: a 10‐ppm gradient of CO 2 ‐mixing ratio is observed during the day by the aircraft measurements. The Meso‐NH model proved able to simulate very well the CO 2 concentration variability as well as the spatial and temporal evolution of the surface fluxes and the boundary layer in the domain. The model is used to explain the CO 2 variability as a result of two complementary processes: (1) the regional heterogeneity of CO 2 surface fluxes related to the land cover (e.g., winter crops versus a pine forest) and (2) the variability of mesoscale circulation across the boundary layer: development of the sea breeze in the western part of the domain and dominating wind flow in the eastern part of the domain.

Abstract. The science guiding the EUREC4A campaign and its measurements are presented. EUREC4A comprised roughly five weeks of measurements in the downstream winter trades of the North Atlantic – eastward and south-eastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, EUREC4A marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or, or the life-cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso (200 km) and larger (500 km) scales, roughly four hundred hours of flight time by four heavily instrumented research aircraft, four global-ocean class research vessels, an advanced ground-based cloud observatory, a flotilla of autonomous or tethered measurement devices operating in the upper ocean (nearly 10000 profiles), lower atmosphere (continuous profiling), and along the air-sea interface, a network of water stable isotopologue measurements, complemented by special programmes of satellite remote sensing and modeling with a new generation of weather/climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that EUREC4A explored – from Brazil Ring Current Eddies to turbulence induced clustering of cloud droplets and its influence on warm-rain formation – are presented along with an overview EUREC4A's outreach activities, environmental impact, and guidelines for scientific practice.

The objective of this article is to present the development and the validation in flight of an airborne probe that can measure in clouds the size of droplets whose diameters are in the range [20 μm; 200 μm].

Abstract. During the EUREC4A field experiment that took place over the tropical Atlantic Ocean east of Barbados, the French ATR 42 environment research aircraft of SAFIRE aimed to characterize the shallow cloud properties near cloud base and the turbulent structure of the subcloud layer. For this purpose, the aircraft payload included radar and lidar remote sensing, microphysical probes, a laser spectrometer, and meteorological sensors. In particular, the aircraft was equipped with a five-hole radome nose as well as several temperature and moisture sensors allowing for measurements of wind, temperature and humidity at 25 Hz. This paper presents the high-frequency measurements made with these sensors and their translation in terms of turbulent fluctuations, turbulent moments and characteristic length scales of turbulence. A particular focus is on the calibration and the quality control of the air moisture measurements, which remain a challenge at fine scales. Level-2 and Level-3 data are distributed as an ensemble of NetCDF files available to the public at AERIS (https://doi.org/10.25326/128, Lothon and Brilouet, 2020).

Abstract. Atmospheric mineral dust aerosol constitutes a threat to aircraft engines from deterioration of internal components. Here we fulfil an overdue need to quantify engine dust ingestion at airports worldwide. The vertical distribution of dust is of key importance since ascent/descent rates and engine power both vary with altitude and affect dust ingestion. We use representative jet engine power profile information combined with vertically and seasonally varying dust concentrations to calculate the “dust dose” ingested by an engine over a single ascent or descent. Using the Copernicus Atmosphere Monitoring Service (CAMS) model reanalysis, we calculate climatological and seasonal dust dose at 10 airports for 2003–2019. Dust doses are mostly largest in Northern Hemisphere summer for descent, with the largest at Delhi in June–August (JJA; 6.6 g) followed by Niamey in March–May (MAM; 4.7 g) and Dubai in JJA (4.3 g). Holding patterns at altitudes coincident with peak dust concentrations can lead to substantial quantities of dust ingestion, resulting in a larger dose than the take-off, climb, and taxi phases. We compare dust dose calculated from CAMS to spaceborne lidar observations from two dust datasets derived from the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP). In general, seasonal and spatial patterns are similar between CAMS and CALIOP, though large variations in dose magnitude are found, with CAMS producing lower doses by a factor of 1.9 to 2.8, particularly when peak dust concentration is very close to the surface. We show that mitigating action to reduce engine dust damage could be achieved, firstly by moving arrivals and departures to after sunset and secondly by altering the altitude of the holding pattern away from that of the local dust peak altitude, reducing dust dose by up to 44 % and 41 % respectively. We suggest that a likely low bias of dust concentration in the CAMS reanalysis should be considered by aviation stakeholders when estimating dust-induced engine wear.

Abstract. Atmospheric mineral dust aerosol constitutes a threat to aircraft engines from deterioration of internal components. Here we fulfil an outstanding need to quantify engine dust ingestion at worldwide airports. The vertical distribution of dust is of key importance since ascent/descent rates and engine power both vary with altitude and affect dust ingestion. We use representative jet engine power profile information combined with vertically and seasonally varying dust concentrations to calculate the ‘dust dose’ ingested by an engine over a single ascent or descent. Using the Copernicus Atmosphere Monitoring Service (CAMS) model reanalysis, we calculate climatological and seasonal dust dose at 10 airports for 2003–2019. Dust doses are mostly largest in summer for descent, with the largest at Delhi (6.6 g). Beijing’s largest dose occurs in spring (2.9 g). Holding patterns at altitudes coincident with peak dust concentrations can lead to substantial quantities of dust ingestion, resulting in a larger dose than the take-off, climb and taxi phases. We compare dust dose calculated from CAMS to spaceborne lidar observations from two dust datasets derived from the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP). In general, seasonal and spatial patterns are similar between CAMS and CALIOP though large variations in dose magnitude are found, with CAMS producing lower doses by a mean factor of 2.4±0.5, particularly when peak dust concentration is very close to the surface. We show that mitigating action to reduce engine dust damage could be achieved, firstly by moving arrivals and departures to after sunset and secondly by altering the altitude of the holding pattern away from that of the local dust peak altitude, reducing dust dose by up to 44 % or 41 % respectively.

Supercooled large droplet (SLD) icing conditions threaten aviation safety. Two flight campaigns in SLD conditions were performed in February-March 2023 in the Great Lakes region and in April 2023 over France as part of the EU-project SENS4ICE. This provides the opportunity to contrast and compare the observations of SLDs between these two locations and months. We present the altitudes, temperatures, number concentrations, liquid water contents as well as the cumulative mass distributions of the SLD conditions. During the North American flight campaign, SLD conditions were observed mostly in thick stratus clouds and droplet size distributions were bimodal with an average median volume diameter (MVD) of 23 µm. Due to warmer ground temperatures in April, icing conditions during the European campaign occurred at higher altitudes, hence predominantly mid-level clouds were sampled. The average MVD of SLD conditions was 45 µm. Our study suggests that the maritime origin of the air masses, their likely low levels of pollution and the associated low number of cloud condensation nuclei facilitated the formation of these SLD conditions with relatively large MVDs. The presented dataset can serve for model comparisons, process-oriented studies of icing conditions, and the validation of airborne sensors developed in the SENS4ICE project.

<strong class="journal-contentHeaderColor">Abstract.</strong> Atmospheric mineral dust aerosol constitutes a threat to aircraft engines from deterioration of internal components. Here we fulfil an outstanding need to quantify engine dust ingestion at worldwide airports. The vertical distribution of dust is of key importance since ascent/descent rates and engine power both vary with altitude and affect dust ingestion. We use representative jet engine power profile information combined with vertically and seasonally varying dust concentrations to calculate the &lsquo;dust dose&rsquo; ingested by an engine over a single ascent or descent. Using the Copernicus Atmosphere Monitoring Service (CAMS) model reanalysis, we calculate climatological and seasonal dust dose at 10 airports for 2003&ndash;2019. Dust doses are mostly largest in summer for descent, with the largest at Delhi (6.6 g). Beijing&rsquo;s largest dose occurs in spring (2.9 g). Holding patterns at altitudes coincident with peak dust concentrations can lead to substantial quantities of dust ingestion, resulting in a larger dose than the take-off, climb and taxi phases. We compare dust dose calculated from CAMS to spaceborne lidar observations from two dust datasets derived from the Cloud&ndash;Aerosol Lidar with Orthogonal Polarization (CALIOP). In general, seasonal and spatial patterns are similar between CAMS and CALIOP though large variations in dose magnitude are found, with CAMS producing lower doses by a mean factor of 2.4&plusmn;0.5, particularly when peak dust concentration is very close to the surface. We show that mitigating action to reduce engine dust damage could be achieved, firstly by moving arrivals and departures to after sunset and secondly by altering the altitude of the holding pattern away from that of the local dust peak altitude, reducing dust dose by up to 44 % or 41 % respectively.

Metropolitan areas are known to be anthropogenic &amp;#8220;hot spots&amp;#8221; of Greenhouse Gas (GHG) fluxes. To track the effectiveness of climate mitigation policies and emission reduction objectives, large metropolitan areas like Munich and Paris regions are currently being instrumented with dense atmospheric GHG networks, further assimilated in inversion systems with high-resolution inventories, also complementing the data collected by remote sensing instruments on the ground and in space. To study medium-sized cities, where a large fraction of the global population lives, spaceborne measurements often fail to quantify fossil fuel emissions since the atmospheric signatures are below the detection threshold of current instruments. For the past two years (2022 and 2023), two large-scale campaigns of the MAGIC initiative led by CNRS and CNES (https://magic.aeris-data.fr) have been taking place in Reims, France, a city with a population of 300,000 inhabitants (207 hab./km2) located to the East of Paris (approx. 100 km away). During these two intensive measurement campaigns, a wide range of ground-based instruments have been deployed around the city to measure CO2 concentrations, in addition to instrumented balloons and aircraft. The goal of these campaigns was to evaluate CO2 emissions from the area and to assess the detection capabilities of current satellite instruments.In our study, we simulated the atmospheric CO2 mixing ratios using the Weather Research Forecast model coupled to a chemistry transport model (WRF-Chem) at 4 horizontal resolutions (9 km, 3 km, 1 km, and 333 m). Typically, mesoscale models are used for resolutions coarser than 1 km while microscale Large-Eddy Simulation models (LES) are used for resolutions finer than 100m. In between, i.e. the grey-zone, turbulent motions are not resolved explicitly but high resolutions might offer a better representation of fine plume structures. Here, we present the results of a multi-scale multi-instrument comparison between the model and the observations to characterize the model performances and the ability of the model to reproduce the observed variations in concentrations. We found that the detectability of the various CO2 plumes remains challenging. First, the strength of the anthropogenic signals from the city remains low compared to gradients from nearby sources, whether industrial or metropolitan, hence making the city plume hard to study. We also showed that improvements in the modelling of CO2 plumes were not significant between the 1 and 0.3 km horizontal resolution scales, thus suggesting that LES models might be better suited for such studies.

International audience

International audience

Atmospheric mineral dust aerosol constitutes a threat to aircraft engines from deterioration of internal components. Here we fulfil an outstanding need to quantify engine dust ingestion at worldwide airports.&amp;#160; The vertical distribution of dust is of key importance since ascent/descent rates and engine power both vary with altitude and affect dust ingestion. We use representative jet engine power profile information combined with vertically and seasonally varying dust concentrations to calculate the &amp;#8216;dust dose&amp;#8217; ingested by an engine over a single ascent or descent. Using the Copernicus Atmosphere Monitoring Service (CAMS) model reanalysis, we calculate climatological and seasonal dust dose at 10 airports for 2003-2019. Dust doses are mostly largest in summer for descent, with the largest at Delhi (6.6 g). Beijing&amp;#8217;s largest dose occurs in spring (2.9 g). Holding patterns at altitudes coincident with peak dust concentrations can lead to substantial quantities of dust ingestion, resulting in a larger dose than the take-off, climb and taxi phases. We compare dust dose calculated from CAMS to spaceborne lidar observations from two dust datasets derived from the Cloud&amp;#8211;Aerosol Lidar with Orthogonal Polarization (CALIOP). In general, seasonal and spatial patterns are similar between CAMS and CALIOP though large variations in dose magnitude are found, with CAMS producing lower doses by a mean factor of 2.4&amp;#177;0.5, particularly when peak dust concentration is very close to the surface. We show that mitigating action to reduce engine dust damage could be achieved, firstly by moving arrivals and departures to after sunset and secondly by altering the altitude of the holding pattern away from that of the local dust peak altitude, reducing dust dose by up to 44% or 41% respectively.

The latest range of CMIP6 model dust simulations shows a greater diversity than previous generations of models in terms of dust emission, deposition, burden and dust optical depth (DOD) (Zhao et al., 2022). Validation of dust models is crucial for understanding the impact of dust on climate and climate change, as well as for quantifying socio-economic and health impacts of dust.While models (and reanalyses) mostly provide output in terms of mass, satellite observations used for model validation are optical measurements. Thus we require good knowledge of the dust mass extinction coefficient (MEC) to successfully validate our dust models. However, the MEC is intricately linked to the dust size distribution, fraction of coarse particles and composition, all of which may vary regionally, in the vertical and in time.This presentation will provide a perspective on some recent efforts exploring the challenges in model validation relating to dust size, composition, optical depth and dust mass loading in climate models (Zhao et al., 2024; Ratcliffe et al., 2024), reanalyses (Ryder et al., 2024), space-borne lidar, space-borne optical depth and in-situ measurements, demonstrating the critical importance and uncertainty of the dust MEC.ReferencesRatcliffe, N.G., Ryder, C.L., Bellouin, N., Woodward, S., Jones, A., Johnson, B., Wieland, L.-M., Dollner, M., Gasteiger, J., Weinzierl, B. Long range transport of coarse mineral dust: an evaluation of the Met Office Unified Model against aircraft observations, Atmos. Chem. Phys., 24, 12161&amp;#8211;12181, https://doi.org/10.5194/acp-24-12161-2024, 2024.Ryder, C.L., B&amp;#233;zier, C., Dacre, H., Clarkson, R., Amiridis, V., Marinou, E., Proestakis, E., Kipling, Z., Benedetti, A., Parrington, M., R&amp;#233;my, S., Vaughan, M., Aircraft Engine Dust Ingestion at Global Airports, https://doi.org/10.5194/nhess-24-2263-2024, 24, 7, Natural Hazards and Earth System Science, 2024.Zhao, A., Ryder, C.L., Wilcox, L., How well do the CMIP6 models simulate dust aerosols?, Atmos. Chem. Phys., 22, 2095&amp;#8211;2119, https://doi.org/10.5194/acp-22-2095-2022, 2022.Zhao, A., Wilcox, L., Ryder, C.L., The key role of atmospheric absorption in the Asian Summer Monsoon response to dust emissions in CMIP6 models, Atmos. Chem. Phys., https://doi.org/10.5194/acp-24-13385-2024, 2024.