Icing still represents a major threat to aviation. This CAL module focuses on the occurrence of icing in stratiform clouds. A method to detect icing probability from satellite images in combination with radar and radiosonde data is presented.
Ice formation on wings and inside of the jet engine of planes causes around 15% of weather related aircraft accidents. Most icing occurs inside cumulonimbus clouds when supercooled droplets freeze with contact of the aircraft body. But also in stratiform clouds icing represents a major threat to aircrafts during landing and take-off phase. In this CAL module, icing hazards related to stratiform clouds are examined. The introductory chapter focuses on the different types of icing and the physical principles leading to ice formation on aircrafts. Satellite products from geostationary and polar orbiting satellites help differentiating between ice and water clouds. A sample of satellite images and products illustrate this capability. Additional data sources like radiosoundings and radar imagery are useful completions to the satellite data. Interpretation of radiosoundings in view of icing occurrence is the main topic of chapter 4. The usefulness of radar data for detecting ice clouds is demonstrated. Three case studies complement the theoretical part of the training module, showing typical weather situations where severe icing represented a serious threat to aircrafts in the past. These case studies combine the above mentioned data sources in the frame of a practical situation. The CAL module finishes on a suggested procedure for nowcasting icing from stratiform clouds. Exercises offering the possibility to test the acquired knowledge form the end of this module.