Search

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.

Modeling the dispersion of volcanic particles released during explosive eruptions is crucially dependent on the knowledge of the source term of the eruption and the source strength as a function of altitude and time. Forecasting volcanic ash transport is vital for aviation but rather inaccurate for quantitative predictions of the fate of volcanic particle emissions. Here we demonstrate an inverse modeling framework that couples the output of a Lagrangian dispersion model with remote sensing observations to estimate the emission rates of volcanic particles released from the Etna eruption. We use an inversion algorithm (Tichy et al., 2020) where the distance between the model and observations is optimized under the assumption that the source term is either sparse or smooth. The Bayesian formalism allows the algorithm to estimate these characteristics together with the source term itself and thus normalize the inversion problem. This methodology uses source receptor relationships as an input from the FLEXPART (flexible particle dispersion) model constrained by ground-based Lidar measurements and satellite observations of SO2 and ash emissions. The case study analyzed here refers to the Etna eruption on 12 March 2021, with the volcanic plume being well captured by the lidar measurements of the PANGEA observatory located at Antikythera island in southwest Greece. A dense aerosol layer, suspending in the height range between 7.5 and 12.5 km (19:30 - 21:30 UTC), has been captured by the PollyXT lidar. For the inversion simulations, we also use data acquired by the Spin-stabilised Enhanced Visible and Infrared Imager (SEVIRI) instrument, mounted on the Meteosat Second Generation (MSG) geostationary satellite. The aforementioned observations serve as a priori source information to estimate the volcanic ash and SO2 source strength, depending on altitude and time, coupled with the output of the FLEXPART model. Our results are efficient for real-time application and could supply ash forecasting models with an accurate estimation of the mass rate of very fine ash during explosive eruptions. Improved forecasts of the dispersed volcanic plumes following the suggested inverse modeling framework would then allow for more effective emergency preparedness for aviation to ensure safety during volcanic eruptions. This research was also supported by the following projects: ERC grant D-TECT (agreement no. 725698); EU H2020 E-shape project (Grant Agreement n. 820852); PANCEA project (MIS 502151) under the Action NSRF 2014-2020, co-financed by Greece and the European Union. The research was supported by data and services obtained from the PANhellenic Geophysical Observatory of Antikythera (PANGEA) of the National Observatory of Athens (NOA), Greece. O. Tichy was supported by the Czech Science Foundation, grant no. GA20-27939S. Tichy, O.; Ulrych, L.; Smidl, V.; Evangeliou, N.; Stohl, A. On the tuning of atmospheric inverse methods: comparisons with the European Tracer Experiment (ETEX) and Chernobyl datasets using the atmospheric transport model FLEXPART, Geosci. Model Dev. (2020), 13, 5917-5934.

The Eastern Mediterranean Basin is an intricate transition region between Eurasia and the Middle East along with Alpine-Himalayan orogenic belt. It is almost amidst the dusty belt and a unique hot spot of climate change in the grand picture. As it involves desert source areas, dust-carrying winds to remote downstream locations enable the entire basin to expose particulate matter throughout the year. As well as global oscillation systems, increasing surface temperatures promote uplifted and remotely transported dust particles. In order to clarify this phenomenon, the main aim is to determine the aerosol and, particularly, dust climatology of the Eastern Mediterranean Basin via CALIPSO onboard Lidar CALIOP. This prominent instrument enables us to better understand aerosols, clouds, and their interactions associated with climatic processes. Using the 9-year CALIPSO-derived aerosol-dust dataset, horizontal and vertical distributions, transport heights and case incidences were analyzed. Multi-year climatology results indicated that the dust extinction coefficient, dust mass in the total aerosol bulk, and uplifted heights increased as the location shifted from west to east. Moreover, for dust transport, spring months are more dominant in the western part, while summer and autumn are in the central and eastern parts. Mountain range systems in the Alpine-Himalayan Orogenic belt obstruct the lofted and buoyant particles from reaching higher latitudes in the north. Besides, dust particles prone to accumulate on the southern slopes of the high ridges pose air quality degradation of the distant cities from the dust source areas. In addition to remote cities having ~0.2 peak AOD values, source regions exceed 1.0 aerosol and 0.8 dust optical depth values. The whole basin's ambient air has an average of 40% dust mass in the total aerosol load. From the eastern shores of the Mediterranean Sea, desert areas and particulate matter are more prone to intrude into inner lands with a continental connection. So, south-eastern Anatolia in Turkey reflects the desert levels with approximately a dust load of 70%.

Aeolus, ESA’s space mission, provides vertical profiles of the HLOS wind component in the troposphere and the lower stratosphere. In addition, ALADIN thanks to its HSLR configuration retrieves and provides profiles of extinction/backscatter coefficients of aerosols and clouds (known as spin-off or L2A products), at the ultraviolet region of the spectrum (355nm). However, ALADIN’s design enables the detection only of the returned co-polar component of the transmitted light. This inherent limitation hampers the ability of ALADIN to provide realistic optical products (i.e., underestimated backscatter coefficient profiles) when non-spherical particles (e.g., dust, volcanic ash, cirrus ice crystals) are probed, a deficiency for the case of Earth Observation of highly depolarizing targets with negative impacts on applications of Data Assimilation (DA) and Numerical Weather Prediction (NWP). The ESA L2A+ (Enhancing Aeolus L2A for depolarizing targets and impact on aerosol research and NWP) project kicked off in November 2022, with an overarching objective to develop a refined Aeolus L2A aerosol product (L2A+) and test its application for enhancing aerosol research. The generation of the refined L2A+ Aeolus aerosol optical product will be based, among others, on an integrated approach of novel algorithms (i.e., AEL-FM/AEL-PRO), model outputs (i.e., CAMS), advanced EO-based products (i.e., MSG, MODIS-MIDAS), existing climatologies (ESA-LIVAS), and AOD retrievals from Aeolus itself. The product will be thoroughly compared with L2A and validated against quality-assured measurements from the ESA-ASKOS/JATAC experiment in Cape Verde. With respect to the overarching objectives on aerosol research, L2A+ aims to (1) examine the impact of L2A and L2A+ on aerosol assimilation and dust transport models, (2) assess the impact of Aeolus on NWP, (3) highlight the benefit of the Aeolus joint aerosol and wind assimilation for simulating dust deposition fields, (4) assess the climatological value of L2A+ for aerosol databases such as the ESA-LIVAS long-term climate dataset, and (5) assess the impact of the novel L2A+ product on aerosol assimilation, towards improved dust transport modelling and for further enhancing NWP. The ESA-L2A+ project focuses on the broader the Western Sahara and the Tropical Atlantic Ocean, while due to the extensive wealth of available observational data collected in the framework of the European Space Agency (ESA) ASKOS Tropical Campaign in Cape Verde, which are needed for a complete and descriptive assessment analysis of the project outputs and the evaluation of the enhanced L2A+ product, the developments and experiments will be performed for September 2021. Preliminary results from the project will be presented. The L2A+ team acknowledges support by ESA in the framework of the "Enhancing Aeolus L2A for depolarizing targets and impact on aerosol research and NWP project (4000139424/22/I-NS).

The aerosol-induced perturbations of the Earth-Atmosphere system radiation budget are determined by the load and the nature of the suspended particles. Therefore, it is crucial to identify accurately various aerosol types characterized by different optical properties, which regulate aerosol-radiation interactions. The discrimination among aerosol species can be sufficiently achieved from ground-based observations in contrast to those derived by satellite sensors subjected to several limitations. In the case of CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) and the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) aerosol product, such deficiencies are attributed either to the erroneous classification of the detected aerosol layers or to the incorrect modelling of aerosol microphysics for particular aerosol subtypes.In the present study, we are developing and demonstrating a simplified aerosol classification scheme capable of identifying dust, marine, clean continental, smoke and urban/smoke particles. For its development, we are relying on quality-assured CALIOP-CALIPSO vertically resolved retrievals (Level 2, Version 4.20) of the backscatter coefficient and the linear particle depolarization extracted from the LIVAS (LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies) database. In addition, simulated relative humidity (RH) profiles from MERRA-2 (Modern-Era Retrospective analysis for Research and Applications version 2) as well as the land cover type from the IGBP (International Geosphere–Biosphere Programme) dataset are jointly processed. Moreover, we are applying a discrimination technique suitable for decoupling the individual components of dust-marine and dust-smoke-urban categories, assuming external aerosol mixtures. Finally, for each defined aerosol type we are setting a representative lidar ratio (LR), derived via an extensive literature review of studies utilizing ground-based measurements, required for the derivation of the extinction coefficient at 532nm. Our algorithm is implemented within the NAMEE (North Africa – Middle East – Europe) domain, hosting a variety of aerosol species of natural and anthropogenic origin, and it is applied over a 14-year period (2007-2020).At the first step of the analysis we are evaluating the columnar aerosol optical depth (AOD), derived from our new classification algorithm, against the corresponding measurements from the ground-based AERONET stations situated within NAMEE as well as versus quality-assured spaceborne (MODIS-Aqua) retrievals. In order to justify the added-value of our approach, we are comparing the assessment results against those obtained from the corresponding evaluation of the raw CALIOP-CALIPSO retrievals using the default and upgraded LRs. After final adjustments in our classification scheme, the aerosol type dependent backscatter and extinction coefficient profiles are gridded at 1° x 1° spatial resolution and on a monthly basis for presenting a 4D climatology within the NAMEE domain. Finally, for each aerosol category we are defining the optical properties required as inputs in a radiative transfer model for estimating the aerosol-induced direct radiative effects within the Earth-Atmosphere system. Acknowledgements: Authors acknowledge support by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “2nd Call for H.F.R.I. Research Projects to support Post-Doctoral Researchers” (Project Acronym: ATLANTAS, Project number: 544).

Land–atmosphere interactions govern the process of dust emission and transport. An accurate depiction of these physical processes within numerical weather prediction models allows for better estimating the spatial and temporal distribution of the dust burden and the characterisation of source and recipient areas. In the presented study, the ECMWF-IFS (European Centre for Medium-Range Weather Forecast – Integrated Forecasting System) outputs, produced with and without the assimilation of Aeolus quality-assured Rayleigh–clear and Mie–cloudy horizontal line-of-sight wind profiles, are used as initial or boundary conditions in the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to simulate 2-month periods in the spring and autumn of 2020, focusing on a case study in October. The experiments have been performed over the broader eastern Mediterranean and Middle East (EMME) region, which is frequently subjected to dust transport, as it encompasses some of the most active erodible dust sources. Aerosol- and dust-related model outputs (extinction coefficient, optical depth and concentrations) are qualitatively and quantitatively evaluated against ground- and satellite-based observations. Ground-based columnar and vertically resolved aerosol optical properties are acquired through AERONET sun photometers and PollyXT lidar, while near-surface concentrations are taken from EMEP. Satellite-derived vertical dust and columnar aerosol optical properties are acquired through LIVAS (LIdar climatology of Vertical Aerosol Structure) and MIDAS (ModIs Dust AeroSol), respectively. Overall, in cases of either high or low aerosol loadings, the model predictive skill is improved when WRF-Chem simulations are initialised with the meteorological fields of Aeolus wind profiles assimilated by the IFS. The improvement varies in space and time, with the most significant impact observed during the autumn months in the study region. Comparison with observation datasets saw a remarkable improvement in columnar aerosol optical depths, vertically resolved dust mass concentrations and near-surface particulate concentrations in the assimilated run against the control run. Reductions in model biases, either positive or negative, and an increase in the correlation between simulated and observed values was achieved for October 2020.

A geopark can be composed of many individual geosites of various geographical scales, thus, categorization according to cartographic scale is crucial for their 3D mapping. The UNESCO Global Geopark of the island of Lesvos in the north-east Aegean, Greece, is a distinctive example of this type of geopark as it contains many unique geosites that vary in geographical scale. The geographical scale is interconnected with the cartographic scale in which the geosite is visualized. The desired cartographic scale is an essential user requirement within an unmanned aerial vehicle's (UAVs) 3D mapping project as the basis for the data acquisition strategy. This research investigates the scale issues in 3D mapping of geosites. Furthermore, it contributes to the incorporation of the geographic and cartographical scales in association with UAV flight parameters such as Ground Sample Distance (GSD), altitude, gimbal pitch, orientation, and front and side overlapping. A total of 132 geosites located in Lesvos Geopark are being studied to determine the flight parameters of three different UAVs and their camera characteristics. The methodology followed to collect very high-resolution images suitable for 3D mapping consists of five main stages: i) determining the geographical scale of each geosite, ii) defining the cartographic scale of all geosites, iii) calculation of the GSD based on cartographic scale, iv) calculation of UAV flight altitude and flight characteristics, and v) classification of geosites based on the flight characteristics for their 3D mapping. Five geographic (G1: < 0.1 ha, G2: 0.1–1 ha, G3: 1–10 ha, G4: 10–100 ha, G5: >100 ha) and five cartographic (C1: > 1:50, C2: 1:50–1:100, C3: 1:100–1:250, C4: 1:250–1:500, C5: < 1:500) categories were defined based on the geosites' size and extent. The combination of the two scales determines the most efficient flight characteristics and optimally acquires very high-resolution images required for the 3D mapping of the selected geosites. Finally, the categorization and characteristics of flights for data collection for high-resolution 3D mapping are collected and presented in a web application. The web application is addressed to the management board of Lesvos Geopark and supports the decision-making processes on mapping geosites using UAVs.

Dust particles larger than 20 µm in diameter (0.2 μm < D < 100 µm) have been regularly observed to remain airborne during long-range transport. In this work we extend the parameterization of mineral dust cycle in the GOCART-AFWA dust scheme of WRFV4.2.1, to include also such coarse and giant particles. The initial particle size distribution in our parameterization is based on observations over desert dust sources and the Stokes’ drag coefficient has also been updated to account for dust particles of all sizes (Re < 105). The new code is applied to simulate dust transport over Cape Verde during the August 2015 AER -D campaign. Model results are evaluated using both airborne dust measurements and the CALIPSO-LIVAS pure dust product. The results show that the modeled lifetimes of the coarser particles are shorter than those observed. Various processes are proposed to explain such inaccuracies, such as the electric field inside dust plumes and non-spherical aerodynamics. Additional sensitivity runs are performed by artificially reducing the settling velocities of the particles to compensate for such underrepresented processes in the model. Our simulations show that particles with diameters of 5–17 μm and 40–100 μm are better represented assuming 80 % reduction in settling velocity (UR80) while particles at the range 17–40 μm are better represented in the UR60 scenario. The overall statistical analysis shows that the UR80 experiment presents the closest agreement with the airborne in situ measurements both in Cape Verde and over the sources. The UR80 experiment improves also the vertical distribution of dust in the model, as compared to the CALIPSO-LIVAS pure dust product. Further research is requested in order to understand the physical processes behind the reduction of settling velocity.

Mineral dust is the most abundant aerosol in the atmosphere and in particular regions exists in high concentrations. Ingestion of dust by aircraft engines can result in erosion, corrosion or a build-up of deposits damaging internal components. A move towards more efficient engines over recent years restricts capacity to tolerate detrimental impacts in engines. Air traffic in arid areas such as the Middle East has also increased dust exposure. However, it is not currently known how much dust is ingested by aircraft during take-off and landing. In order to quantify this, the vertical profile of dust is required. Here we present a climatology of vertical profiles of dust from the ECMWF Copernicus Atmospheric Monitoring System (CAMS) reanalysis at 10 major global airports, as well as their seasonal and diurnal variability, between 2003-2020. We evaluate the CAMS dust profiles against spaceborne lidar retrievals of dust from the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument aboard the CALIPSO satellite using both the standard NASA Level 3 product and the LIdar climatology of Vertical Aerosol Structure (LIVAS) product. Finally, using expected aircraft ascent and descent rates and associated mass flow into an engine, dust dose is calculated for take-off, climb, descent, hold, approach, land and taxi phases, as well as for the entire ascent/descent at different airports, using both CAMS and CALIOP datasets. We show that vertical distribution of dust varies significantly between airports and across seasons, which has a large impact on the total engine dust ingestion. Diurnal dust variations at some airports such as Dubai are extremely large, with night time surface concentrations reduced by over 20%. Vertical profiles from CAMS show considerable differences to the standard CALIOP L3 retrievals, though agreement with LIVAS profiles is much better. Aircraft engine dose is found to be highest for Delhi (where does exceed 7g for a single descent in summer), Niamey and Dubai. During ascent, ingestion is largest during take-off, such that airports with large concentrations of lower altitude dust incur higher doses. During descent, dose is strongly dependent of the altitude of holding pattern relative to the altitude of maximum dust concentration, such that Delhi and Dubai incur the largest dust dose. Therefore, it is recommended that measures to reduce dust ingestion are airport-specific, and could include practices such as night time take-off and adjustment of holding pattern altitude.