Extreme convective events are increasing in northern and eastern Europe in frequency and intensity causing many deaths, injuries and damage to property every year, and accounting for major economic damages related to natural disasters in several countries. Atlantic hurricanes become extra-tropical cyclones and, sometimes, reach northern Europe. Mediterranean hurricanes (Medicanes or tropical-like cyclones) are not that frequent as other convective systems or tropical cyclones, but these can still reach the intensity of tropical cyclones, causing severe damages in the Southern European region. Supercells and connected tornadoes are also becoming more frequent in central Europe.

In recent years, attention was paid to the detection and monitoring of volcanic ash clouds as their impact on the European air traffic control system was unprecedented. In 2010 the Eyjafjallajökull eruption caused the closure of the airspace of several countries generating the largest air traffic shutdown since the World War II. Volcanic clouds are very dangerous for the aviation operations as they can cause damage of the aircraft systems and engines not only close to active volcanoes but also at large distance from the eruption, and they affect economic, political and cultural activities. Europe is located between the chain of Icelandic and Italian/African volcanoes which are unpredictable, and could easily emanate the ash clouds throughout the skies of the continent.

The recent Anak Krakatau eruption (December 2018) highlighted the issue on different techniques to distinguish volcanic ash clouds than convective clouds and the unsolved problem to understand if the cloud top was tropospheric or stratospheric. Specific discussion on this topic will be very welcome to the session.

The extreme convective clouds and the volcanic ash clouds are types of “extreme clouds”. The “extreme clouds” detection and estimation of their physical parameters is a highly multidisciplinary and challenging topic since the same techniques and instruments can be used for meteorology, volcanic monitoring, atmospheric physics and climate purposes. But there is an urgent need to develop new techniques and instruments for monitoring, detecting and modeling “extreme clouds” to develop early warning systems and to support users, decision makers and policy makers. Given the large uncertainties that still remain in the field, enlarging and coordinating the research community for developing new techniques and improving our knowledge is required. Furthermore, there is a need for improved information exchange regarding the impact of the extreme clouds on daily operations between the producers and intended uses of the information.

The objective of the session is to connect different communities in touch with the “extreme clouds”, such as scientists working in remote sensing, modelers, meteorologists, physicists, aviation managers. Thus, allowing the researchers to understand the end-users’ needs and for the end-users to understand the research capabilities.

This session solicits the latest studies from the spectrum of:
- detection, monitoring and modeling of extreme clouds,
- understanding the impact of extreme clouds on climate changes,
- proposal of new products or services focused on the end-users prospective,
- discussion on Anak Krakatau eruption (December 2018)

By considering studies over this range of topics we aim to identify new methods, detail current challenges, understand common techniques/methods and identify common discussions within the communities of atmospheric physicists, meteorologists, modelers, air traffic managers, pilots sensors engineers and engines manufacturers. We particularly welcome and encourage contributions connecting different fields such as:
- forecasting tools to support air traffic management improving the limits of the present science and new products/tools providing better services to the end-users,
- extreme clouds remote sensing with novel techniques and new sensors,
- novel techniques to detect overshooting and their impact on climate.

The aim of the session is to promote discussions between scientists on future developments, in understanding, monitoring and forecasting the extreme clouds, studying their impact and to extend the discussion with the end-users for improving air safety. This session is thus open to contributions on all aspects of remote sensing, forecast, and tools/services development such as:

- Extreme clouds remote sensing
- Extreme clouds modeling
- Extreme clouds forecasting and nowcasting
- Extreme clouds structure
- Extreme clouds and climate change
- Overshooting and Ice clouds
- Air traffic management issues related to extreme clouds
- Airport issues

Co-organized as NH1.25
Convener: Riccardo Biondi | Co-conveners: Tatjana Bolic, Stefano Corradini, Nina Iren Kristiansen
| Tue, 09 Apr, 16:15–18:00
Room 0.60
| Attendance Tue, 09 Apr, 14:00–15:45
Hall X5

Tuesday, 9 April 2019 | Room 0.60

Chairperson: Riccardo Biondi
16:15–16:30 |
| solicited
Corrado Cimarelli and the VoLT
16:30–16:45 |
| Highlight
Andrew Tupper, Chris Lucas, Anjelica Chang, Jarrad Denman, Adele Crozier, Rajneel Prasad, and Meelis Zidikheri
16:45–17:00 |
| Highlight
Fred Prata, Andrew Prata, Riccardo Biondi, Hugues Brenot, and Stefano Corradini
17:00–17:15 |
Isabelle Taylor, Elisa Carboni, Lucy Ventress, Tamsin Mather, and Roy Grainger
17:15–17:30 |
Caron Vossen, Corrado Cimarelli, Damien Gaudin, Matthias Hort, Alec Bennett, Daisuke Miki, Masato Iguchi, Jeff Lapierre, Michael Stock, and Donald Dingwell
17:30–17:45 |
Luigi Mereu, Simona Scollo, Costanza Bonadonna, Franck Donnadieu, and Frank Marzano
17:45–18:00 |
Hugues Brenot, Nicolas Theys, Jeroen Van Gent, Sophie Vandenbussche, Lieven Clarisse, Nikolaos Papagiannopoulos, Lucia Mona, Luca Bugliaro, Pascal Hedelt, Tuomas Peltonen, Juhani Lahtinen, Delia Arnold-Arias, Michelle Maree Parks, Sara Barsotti, Mauro Coltelli, William Moreland, Timo Virtanen, Klaus Sievers, Saskia Wagenaar, and Wim Som de Cerff and the WP5 EUNADICS-AV team