Aviation Meteorology: Observations and Models. Introduction
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This special issue of Pure and Applied Geophysics contains an introduction plus 14 papers related to Aviation Meteorology. The papers cover important topics such as wind, gust, turbulence, visibility related to fog and precipitation, convection and lightning, icing, and high ice water content and engine icing. These research areas are important to develop applications for aviation meteorology, and in particular, aviation operations. The results discussed in this special issue are generated by research efforts conducted internationally, and include several review papers. Review papers on aviation meteorology (Gultepe et al. 2019a), gravity waves and convectively-induced turbulence (Sharman and Trier 2019), lidars (Thobois et al. 2019), and geostationary satellites (Ellrod and Pryor 2019), as well as supersite observations (Gultepe et al. 2019b) provided extensive details for operational applications. Some of these papers were included in various international conferences, including the EGU (European Geophysical Union) aviation meteorology sessions, that took place in Vienna, Austria, during 2016–2018.
For this volume we focused on scientific and operational issues that affect flight conditions, such as aircraft climb, and drag and lift forces. The review paper by Gultepe et al. (2019a) clearly shows that wind, turbulence (including gust), and visibility are more often a cause of aircraft flight disruptions, rather than other factors, such as icing conditions studied in Chuang et al. (2019), convection, and pollution-dust, which also play important roles for aviation operations. Therefore, more research is needed to characterize aircraft flying conditions and ground based operations and environments.
Aviation meteorology needs new instrumental platforms and analysis techniques to improve safety conditions for flight environments. These platforms need to be developed as a part of integrated systems, such as ground based in situ observations, and remote sensing platforms, that include both ground and space based operational satellites. Although presently unmanned aerial vehicle (UAV) and unmanned aerial systems (UAS) platforms have not been used for operations, they are becoming very popular for atmospheric research, especially for dangerous conditions such as hurricanes, convective storms, and icing environments (Griffin and Velden 2019), as well as NWP (numerical weather prediction) simulations and initializations. The UAVs can carry various miniature sensors for weather research and observations (Gultepe et al. 2019b). In this topical special issue, the importance of UAVs for future atmospheric research has also been emphasized for high level and low-level flight conditions and weather research.
Ground based in situ observations of various aviation meteorology related parameters can be obtained for extreme weather conditions within climate and wind tunnel laboratories (Gultepe et al. 2019b). Two of these, including the University of Ontario Institute of Technology (UOIT) climatic wind tunnel (CWT) and NASA Glen wind tunnel, have been used for simulating Arctic and icing environments, respectively (Gultepe et al. 2019a). Climatic wind tunnel tests are also important for simulating aircraft aerodynamic conditions that had been summarized by many others (Dodson 2005; Tomek et al. 2006; Bell 2002; Ross 2011).
Weather forecasts have been improved over short and long-time periods, using various analysis systems, such as NWP models (Chachere and Pu 2019), nowcasting-based systems, integrated methods, and statistical-based methods such as neural network and artificial intelligence (AI) systems (Kneringer et al. 2019; Zheng et al. 2018). This topical issue provides the current status and challenges of these systems. While none of these systems alone can provide accurate predictions of meteorological parameters over short or long-time periods, integrating these methods can be used more confidently to improve aircraft physical and managerial flying conditions, including conditions on the ground (Kutty et al. 2019; França et al. 2019). Several papers focusing on these issues are included in this issue.
The accuracy of forecasting and nowcasting aviation weather using numerical models and remote sensing techniques still remains difficult, mainly because of the lack of observations for physical and dynamical parameterizations as a part of numerical models (Weston et al. 2019). Presently, typical numerical forecast models lack sufficient time and space resolutions and appropriate physical parameterizations to represent aircraft scales (10–100 m) in estimating aerodynamic and microphysical processes. Simple approaches, e.g., using only temperature and relative humidity with respect to water (RHw) to calculate icing rates, can lead to uncertainties of more than 30% in many conditions.
This topical special issue points out that improvements of in situ observations and microphysical parameterizations are required to reduce aviation related accidents. Pu et al. (2019) stated the importance of microphysical parameterizations for convective systems and NWP sensitivity for various parameterizations. However, detailed 3D models do not represent certain scales and use large scale parameterizations for predictions; furthermore, these 3D models are currently not practical to be used operationally because of processing time of numerical algorithms based on smaller time and space scales. The capability of these models needs to be improved mainly for wind speed and direction, gust, visibility and ceiling, convection, and icing conditions. For example, Gultepe et al. (2019a) stated that on average, 60 people die because of fog-related accidents every year in Canada, which is comparable to impacts resulting from other severe weather events, and these numbers can be much higher based on international considerations. In fact, the worst accident in aviation history occurred due to fog and low visibility impacting aircraft take off processes on March 27, 1977. Two Boeing 747 passenger airliners collided on the runway of Tenerife Airport on the Spanish island of Tenerife, one of the Canary Islands. The crash claimed a total of 583 fatalities (Smith 2017). As is the case in most weather-related aviation accidents, several conditions combined leading to the accident occurrence, however certainly dense fog played a critical role. The two aircraft would have been aware of one another’s presence in fair conditions, but because of dense fog, neither aircraft could see one another until it was too late.
Wind and turbulence activities factor into the aircraft landings and takeoffs conditions (Sharman and Trier 2019). In reality, wind measurements at airports lack the needed resolution over the horizontal and vertical scales. Therefore, improvements in wind measurements can only be done by using state of the art observational platforms such as lidars and UAVs (Thobois et al. 2019; Gultepe et al. 2019b). Doppler lidars (Thobois et al. 2019) adaptable for airport use can provide wind speed, directional shear, gust, and turbulence conditions over short time and space scales at airports and during landings and takeoffs. As a result, these new platforms can be used to more accurately define safety conditions for aviation applications.
While this publication broadly covers the whole of aviation meteorology, less information on Polar flight conditions is noted, although major issues related to cold temperature and snow conditions, as well as ice fog, are discussed extensively. To simulate Polar conditions, climate wind tunnels (e.g., UOIT CWT, Gultepe et al. 2019b) can be used to test aircraft parts and pieces, but these also need to be validated using real flight environments. In reality, freezing fog and ice fog occur often in cold climates, particularly in the high Arctic and Antarctic regions, and can create adverse weather conditions for aviation and marine applications, that need to be addressed seriously as air traffic and marine transportation increases over the Arctic regions.
Guest editors wish to thank the scientific contributors to this topical issue and we also gratefully acknowledge funding support for Editor I. Gultepe by Environment and Climate Change Canada (ECCC) and the Canadian National Search and Rescue (SAR) Secretariat. In addition, our sincere thanks go to Drs. Renata Dmowska and Alexander Rabinovich, Editors in Chief for topical and regular issues at Pure and Applied Geophysics, for inviting our working group to prepare this topical issue, handling the review process and providing invaluable advice. Special thanks are also given to all contributors, who submitted their valuable work to this topical issue as well as to all reviewers.
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