Clear-air turbulence (CAT) is hazardous to aircraft and is projected to intensify in response to future climate change. However, our understanding of past CAT trends is currently limited, being derived largely from outdated reanalysis data. Here we analyse CAT trends globally during 1979–2020 in a modern reanalysis dataset using 21 diagnostics. We find clear evidence of large increases around the globe at aircraft cruising altitudes. For example, at an average point over the North Atlantic, the total annual duration of light-or-greater CAT increased by 17% from 466.5 hours in 1979 to 546.8 hours in 2020, with even larger relative changes for moderate-or greater CAT (increasing by 37% from 70.0 hours to 96.1 hours) and severe-or-greater CAT (increasing by 55% from 17.7 hours to 27.4 hours). Our study represents the best evidence yet that CAT has increased over the past four decades.

How to cite: Williams, P. D., Prosser, M. C., Marlton, G. J., and Harrison, R. G.: Evidence for Large Increases in Clear-Air Turbulence over the Past Four Decades, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3472, https://doi.org/10.5194/egusphere-egu23-3472, 2023.

The Meteomatics Meteodrone is a small Unmanned Aircraft System (UAS) designed to collect high-resolution vertical profiles of atmospheric parameters such as temperature, humidity, wind speed and direction, and barometric pressure. Since its founding in 2012, Meteomatics has undertaken an iterative development of the Meteodrone technology, with regular releases of incremental enhancements. The newest model, the MM-670, features major improvements to measurement accuracy, flight capabilities and reliability, and safety and regulatory compliance, making it suitable for routine operational and research use.

In 2023, Meteomatics is continuing to install a network of 15 Meteodrones around Switzerland and has initiated a pilot weather forecasting project at one site in North Dakota, USA in collaboration with its partners Grand Sky and TruWeather Solutions. In both cases, Meteodrones are launched remotely from semi-automated Meteobase drone-in-a-box systems and routinely flown to collect profiles to a maximum of approximately 6,000 metres AMSL.

The data collected by the Meteodrones can fill gaps in the existing weather observation network, especially in the boundary layer regions where extreme weather events occur. This data is used for nowcasting purposes and to improve the accuracy of Meteomatics-developed 1 km-resolution Weather and Research Forecasting (WRF) models. In this presentation, we will share learnings from our research that has enabled the transition to operational use of Meteodrones, including how the technology has evolved and specific issues have been investigated and addressed.  In addition, future applications of this new technology, including improvements to nowcasts and forecasts, will be be discussed and evaluated.

How to cite: Guay, B., Fengler, M., and Hammerschmidt, L.: Improving Nowcasts and Forecasts via Operational Use of Meteomatics Meteodrones, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8632, https://doi.org/10.5194/egusphere-egu23-8632, 2023.

Aviation emissions perturb the atmosphere through CO₂ and non-CO₂ effects, which include, for instance, the radiative effects of contrail cirrus, H₂O emissions, and NO_x induced changes on atmospheric ozone and methane concentrations. The life-time of these non-CO₂ perturbations is in the order of hours to days or weeks, and thus the resulting climate impact is highly dependent on the background atmospheric conditions, which vary with time, location, and altitude of emission. Mitigation strategies to reduce aviation climate impact could exploit this dependency on weather conditions, e.g., optimizing aircraft trajectories to minimize their climate impact. In particular, previous research shows the potential of “eco-efficient” trajectories, which lead to significant climate impact reductions at limited cost increases [1]. However, a strategy to identify days with a high mitigation potential is currently missing. For this purpose, we investigate in our study the correlation between days characterized by the identification of anomalously high numbers of eco-efficient trajectories, and the atmospheric conditions simulated on those days, e.g., considering the strength and location of the jet stream.

We use the ECHAM/MESSy Atmospheric Chemistry (EMAC) model, a numerical chemistry and climate simulation system that includes sub-models describing tropospheric and middle atmosphere processes and their interaction with oceans, land and human influences [2]. Our simulations include the submodels ACCF [3], using prototype algorithmic Climate Change Functions (aCCFs) to estimate the climate effects of aviation emissions, and AIRTRAF [4], optimizing aircraft trajectories under the atmospheric conditions simulated by EMAC. The total Average Temperature Response in 20 years (ATR20) of NO_x, contrails, CO₂, and H₂O from each flight is computed using the aCCFs [5]. We conduct 1-year simulations optimizing 100 European flights per day. Our results show that 20% of the flights are responsible for about 70% of the total climate impact reduction, and that these flights are not homogeneously distributed over the simulated days: a strong daily variability is found, due to the aCCFs gradients variability under different atmospheric conditions.

Acknowledgment: FlyATM4E has received funding from the SESAR Joint Undertaking under grant agreements No. 891317 under European Union's Horizon 2020 research and innovation program. ClimOp has received funding from European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 875503.

[1] Matthes, S., et al.: Climate-optimized trajectories and robust mitigation potential: Flying atm4e, Aerospace, 7, 1–15, https://doi.org/10.3390/aerospace7110156, 2020.

[2] Jöckel, P., et al.: Development cycle 2 of the Modular Earth Submodel System (MESSy2), Geoscientific Model Development, 3, 717–752, https://doi.org/10.5194/gmd-3-717-2010, 2010.

[3] Yin, F., et al.: Predicting the climate impact of aviation for en-route emissions: The algorithmic climate change function submodel ACCF 1.0 of EMAC 2.53, Geosci. Model Dev. Discuss. [preprint], https://doi.org/10.5194/gmd-2022-220, in review, 2022.

[4] Yamashita, H., et al.: Newly developed aircraft routing options for air traffic simulation in the chemistry–climate model EMAC 2.53: AirTraf 2.0, Geoscientific Model Development, 13, 4869–4890, https://doi.org/10.5194/gmd-13-4869-2020, 2020.

[5] Dietmüller, S., et al.: A python library for computing individual and merged non-CO₂ algorithmic climate change functions: CLIMaCCF V1.0, Geosci. Model Dev. Discuss. [preprint], https://doi.org/10.5194/gmd-2022-203, in review, 2022.

How to cite: Castino, F., Yin, F., Grewe, V., Yamashita, H., and Matthes, S.: Weather patterns characterizing eco-efficient aircraft trajectories, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9169, https://doi.org/10.5194/egusphere-egu23-9169, 2023.

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 dose exceeds 7g for a single descent in summer), Niamey and Dubai. During ascent, ingestion is largest during the take-off phase of flight, 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.

How to cite: Ryder, C., Bezier, C., Dacre, H., Clarkson, R., Marinou, E., Proestakis, M., Amiridis, V., Vaughan, M., Kipling, Z., Benedetti, A., and Parrington, M.: How much Desert Dust do Aircraft Engines Ingest at Major Airports?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15969, https://doi.org/10.5194/egusphere-egu23-15969, 2023.

Recent studies showed that the modified YSU scheme, which added a fog top-down diffusion mechanism (ysu_topdown_pblmix), facilitated the bottom lifting of valley fog and sea fog by taking into account the “top-down” turbulent mixing and entrainment enhancement due to radiative cooling at the fog top, thus eliminating false fog areas. The applicability of this scheme to fog processes over the North China Plain is of interest. In this paper, we compared and analyzed the simulated effects of the modified YSU scheme on three fog events over the North China Plain with conventional ground-based data, 15-layer gradient and 5-layer eddy-related observations from atmospheric boundary tower. It was found that, unlike the results of existing studies, considering the fog-top turbulent diffusion mechanism resulted in lower TS scores for the fog area in the North China Plain, especially for the deep fog processes. A specific analysis of the simulated performance of a frontal fog on 17-20 December, 2016 showed that although the modified YSU scheme improved the simulation of nighttime near-surface temperature, humidity and vertical development of the fog layer, the simulated fog-top turbulence was too strong compared with the actual observations, resulting in a shorter fog duration and a significantly reduced fog area. By adjusting the parameter to reduce the intensity of the fog top turbulence entrainment, this operation can effectively reduce the under-reporting of the fog area and improve the simulation of fog over the North China Plain.

How to cite: Tian, M. and Wu, B.: The Evaluation of Modified YSU Scheme and Parameter Adjustment on the Simulation of Fog over the North China Plain, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4263, https://doi.org/10.5194/egusphere-egu23-4263, 2023.

The objective of this study is to investigate the vertical profiles of shallow fog events that occurred during the FATIMA (Fog and turbulence in the marine atmosphere) field campaign. The project took place over Sable Island and the surrounding ocean during July 2022. The profiles of meteorological and physical parameters were collected by instruments on 1) an Aeryon UAV (Unmanned Aerial Vehicle), 2) a TBS (Tethered Balloon System), 3) a MWR (microwave radiometer), 4) meteorological towers, and 5) radiosonde balloons released approximately every 3 hrs. Atmospheric profiles of temperature (T), relative humidity with respect to water (RHw), horizontal wind speed (Uh), as well as particle counts from the OPC-N3 (23 bins from 0.3 μm to 40 μm) when RHw~100%, and the fog vertical microphysics structure using in-situ observations are evaluated. Various parameters such as liquid water content (LWC), droplet number concentration (Nd), mean volume diameter (MVD), and aerosol number concentration (Na) are analyzed to elicit issues related to measurements. Based on the profiles of visibility (Vis), droplet size spectra, and meteorological parameters such as RHw, T, and Uh from the UAV and turbulence towers, we will be able to investigate the vertical variability for several shallow marine fog events.

In this presentation, issues related to atmospheric boundary layer profiling and vertical mixing processes will be investigated using in-situ observations from the profiling platforms, as well as a well instrumented UAV. Results will be discussed by emphasizing the future sensor developments and investigating the microphysical parameterizations.

This work was funded by the Grant N00014-21-1-2296 (Fatima Multidisciplinary University Research Initiative) of the Office of Naval Research, administered by the Marine Meteorology and Space Program.

How to cite: Gultepe, I., Fernando, J. H., Pardyjak, E., Wang, Q., Hoch, S., Perelet, A., Jesus, R.-P., and Dorman, C.: Profiling of Shallow Marine Fog using a UAV and Remote Sensing Observations over the Sable Island during FATIMA, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10484, https://doi.org/10.5194/egusphere-egu23-10484, 2023.

Freezing fog is a type of cold fog that forms when the air temperature (Ta) is below 0℃. Although Ta is below 0℃, the water droplets can remain in a liquid state rather than freezing. Freezing-fog conditions can pose a significant hazard to aviation and marine operations because it can reduce visibility severely, and ice accumulates rapidly on the surfaces such as aircraft, ship, and roads. Observations collected during the CFACT (Cold Fog Amongst Complex Terrain) Project from 7 January – 24 February, representing cold-fog events over Heber Valley of Utah, are used in the analysis. The objectives of this study are to characterize freezing fog microstructure in detail with respect to droplet size distribution, critical diameter related to activation, and visibility. In the analysis, freezing fog (FZFG) and droplet size spectra will be examined theoretically and experimentally. The droplet activation and critical diameter forming in frozen-fog droplets will be revealed using the Köhler curve. The effect of the droplet-growth process on visibility changes for two cold-fog cases is examined and results are discussed. Preliminary analysis suggests that freezing-fog droplet growth strongly depends on environmental conditions, including Ta, relative humidity (RH), and liquid water content (LWC) as well as droplet number concentration (Nd). It is concluded that microphysical parameterizations should investigate freezing-fog droplet formation and growth in more detail because presently it is lacking in NWP predictions. 

How to cite: Durmus, O., Gultepe, I., Pu, Z., Hoch, S., Pardyjak, E., Hallar, A. G., and Perelet, A.: Droplet Growth and Its Impact on Visibility During Freezing Fog Events from CFACT, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11108, https://doi.org/10.5194/egusphere-egu23-11108, 2023.

Based on mesoscale automatic weather stations, NCEP FNL reanalysis data and satellite retrivaled fog from 2015 to 2020, the distinction of the land fog and sea fog over the Bohai coastal zone were analyzed. It shows although Bohai coastal fog often occur, they frequently divided into land fog or sea fog by western coastline. In order to explore the causing of this phenomenon, the Bohai coastal fog were selected as the research object in this work. Four types of fog events were taken into account according the following situations, (1) only land fog, (2) Land fog drifting to over marine areas, (3) only Sea fog, (4) Sea fog drifting to over inlands.

According to the statistics of the above four fog types, the characteristics and diurnal variation difference of fog show that, although the sea fog and land fog have the same inter-monthly distribution trend and all the most in winter, the difference was still significant. Land fog was more than sea fog in the autumn and winter, while on the contrary in the spring and summer. The event of sea fog and land fog clearly separated by the western coastline mostly occurs in the spring and winter night and lasted less than 12 h.

In order to further understand the reason that the coastal fog do or not cross the coastline, Firstly, we compared the two land fog events. One land fog occurred while not crossing the coastline, the other spread to the sea. The results show that, under the condition of a weaker weather systematic low-level circulation, the sea-land breeze thermal circulation humidify the inland air, which is favorable to land fog formation. The eastward inland fog moving into the marine area and dissipate due to the higher sea temperature. The stronger offshore wind is favorable for land fog drifting to the sea, and the fog over the sea can develop with the lower sea temperature. The sensitivity simulation experiment using WRF further made sure, when the SST increased by 5%, as the sea-land breeze strengthened, the fog area that is slightly offshore in the control experiment would retreat to the west of the coastline, and the land fog also showed more dense; while when the SST decreased by 5%, the sea-land wind is suppressed, resulting in the fog cases that originally stopped at the west coastline will spread and cover the Bohai area and maintain for a long time.

Secondly, by comparing the two marine fog events, which did or not diffuse westerly across the coastline, the results explore that, under the condition of obvious weather systematic low-level circulation, sea wind is favorable for sea fog diffusing to inland. Without systematic low-level circulation transportation, intensity of thermal differences between sea and land and suitable land temperature will determine whether sea fog can cross the western coastline. In conclusion, the thermal differences and its intensity between sea and land jointly to the favorable systematic low-level atmospheric circulation determine the finely location of fog in the coastal zone area.

How to cite: Wu, B.: Effect of both sea-land thermal difference and low-level circulation on finely location of Bohai coastal fog, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14627, https://doi.org/10.5194/egusphere-egu23-14627, 2023.

Fog and low-level stratus have been recognised as a hazardous weather phenomenon leading to several losses in time, money and even human life above all in aviation but also in other forms of transportation, such as navigation and land transportation. The forecast of low-level stratus and fog is one of the most difficult issues of aviation meteorology due to spatial and temporal variability of their characteristics and high dependence on local conditions. So, weather observations can be used for statistical dependencies of fog/low-level stratus characteristics on numerical model outputs.

To study fog and low-level stratus characteristics occurring at the airport of Lviv, Ukraine, three-hourly meteorological observations in the period of 2010-2020 are used. Applying a statistical approach annual, seasonal and diurnal distribution of fog and low stratus and their frequency distribution associated with various meteorological parameters are obtained.

It was shown that at the airport of Lviv low-level stratus more frequently (60% of all cases) forms in the November-December-January-February period, whereas in July and August it is least frequently observed (less than 5% of all cases). Distribution of the fog observations with respect to months also is inhomogeneous. Fog mainly forms from October to January (56% of all cases) with the maximum (19%) in November. From March to September fog happen rarely with minimum in June (3% of all cases). No distinct diurnal cycle of the low-level stratus occurrence can be revealed from the data, however low-level stratus more frequently occurs during the nighttime and in morning. As opposed to low-level stratus for fog the highest frequency is observed in the hours before sunrise, while when the day sets in, frequencies are declining and increasing at night.

Low-level stratus is the most commonly associated with surface temperatures of 0.0 to +8.0°С and relative humidity of 80 to 95% (32% of all cases), by comparison with 35% of all fog cases observed at temperatures of 0.0 to +6.0°С and relative humidity of 96 to 100%.

In all seasons of the year, the highest frequency of low-level stratus (from 35 to 40% of all cases) is in interval of 3...4 m/s, whereas fog is the most frequently observed in calm weather (from 37 to 77% of all cases). In autumn and winter, both under low-level stratus and fog, surface wind is characterized by high occurrence frequency of west, north-west (around 25% of low-level stratus cases and 10% of fog cases) and south, south-east (around 30% of all cases) directions. In spring and summer, north, north-west and west directions are most frequently reported in low-level stratus cases (47% of low-level stratus cases in spring and 69% in summer). For fog in spring and summer the same wind directions are typical (18% of fog cases in spring and 10% in summer). However, it should be noticed that in spring the east direction is often observed for both fog and low-level stratus.

How to cite: Khomenko, I. and Hustenko, O.: Fog and low-level stratus characteristics at the airport of Lviv from surface observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17403, https://doi.org/10.5194/egusphere-egu23-17403, 2023.

Effectively communicating hazardous weather conditions to the general aviation (GA) community is a
continuously evolving effort of US National Weather Service (NWS) Aviation Weather Center (AWC)
operations. AWC has started to transition text heavy products in favor of easily interpreted dynamic
graphics that provide additional information that was never fully realized through text alone.
AWC provides domestic and international aviation weather forecasts and warnings, disseminated
through traditional product dissemination as well as directly to end users through AviationWeather.gov.
The web site is currently undergoing a complete rewrite, in order to both modernize and improve
consistency. Customer feedback has been gathered over multiple years and the rewrite is intended to
address a number of issues in a comprehensive manner.
Many products that were previously available in multiple formats are now presented through a more
integrated framework, allowing for the user to combine different datasets as desired. The Graphical
Forecasts for Aviation (GFA), first developed as a replacement for the traditional text Area Forecast,
now spans a wide variety of weather information in a one stop Geographic Information Systems (GIS)
interactive web framework. The site is designed to adjust to available screen real estate, making the
same data and interface available on a variety of platforms from desktop computers to tablets and
phones.
The new site has been in an experimental status since spring of 2022, while AWC collects feedback on
the new design and performed a social science user assessment in partnership with the US Federal
Aviation Administration’s (FAA) Aviation Weather Demonstration and Evaluation service group. This
presentation will discuss the design and features of the new site, as well as lessons learned from the
aviation weather user community during the development and evaluation.

How to cite: Cross, A., Avay, S., Hepper, R., Vietor, D., and Stevens, N.: Effectively Communicating Aviation Hazards through Modernized Web Products, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17422, https://doi.org/10.5194/egusphere-egu23-17422, 2023.