Mountain waves occurrence in Polish Carpathians and their influence on aviation operations

Mountain regions, as defined by the International Civil Aviation Organization (ICAO), cover less than 5% of Poland, but highly variable orography dominates almost whole southern border of the country. Under favorable conditions, orographic gravity waves are observed in the wind field over significant part of southern Poland, influencing airspace users. 

Private aircrafts, weighing around five tons and often less, experience orographically induced turbulence directly but not exclusively over the mountainous areas: rotors occurring downstream generate moderate or severe turbulence as well. Moreover, their presence may not be evident in cloudiness so that the pilot encounters so-called clear air turbulence (CAT). Airports located downstream can experience low level wind shear which creates additional difficulties for take-off and landing operations, and if encountered unprepared, can result in a dangerous loss of lift. It is recommended by the ICAO that mountain waves (MTW) of moderate or severe intensity are included in aviation weather forecasts products. 

This study presents the MTW climatology in Polish Carpathians, focusing mainly on the Tatra mountains, using observational data and ERA5 reanalysis. Typical synoptic situations favorable for MTW occurrence in southern Poland are summarized. Based on an extreme case of a devastating downslope windstorm in the Tatra mountains in 2013, the impact of numerical model resolution on resolving the mountain wave effects is investigated using high resolution WRF (Weather Research and Forecasting model) simulations. 

This project has been supported by the subsidy of the Meteorological Service for Civil Aviation of Institute of Meteorology and Water Management – National Research Institute of Poland, "Excellence Initiative - Research University" program at AGH University of Krakow (grant agreement no. 598707), and the subsidy of the Ministry of Science and Higher Education.