PreViBOSS
The aim of the project was to identify atmospheric visibility change predictors on a hourly time scale, among multi-sensor observation data sets, including ground-based instruments and satellites. The project involved the collaboration of CNRS and HYGEOS.
Assistance tool for fog formation nowcasting on a site
- shows the evolution of local observed parameters in real time,
- shows the evolution of the regional cloud cover observed by satellite,
- shows results of weather modelling for the site,
- identifies the fog formation type,
- computes fog formation probability according to 6 observed predictors [Elias et al., 2017].
Animations are proposed for several situations:
- Succeeded nowcasting of a developed fog (scenario F1): 15 November 2011
- False alarm of a developed fog (scenario F1): 13 November 2011
- Missed fog, starting as a thin fog (scenario U5), and then developing in th vertical direction: 01 November 2011
- Succeeded nowcasting of a thin fog and false alarm, under cloud-free sky (scenario F2): 19 November 2011
- Succeeded nowcasting of a thin and short fog under cirrus (scenarii F3 and F7): 20 November 2011 and 21 November 2011
- False alarm of a thin fog under cirrus (scenario F3): 28 November 2011
Predictors
Six predictors were selected [Elias et al., 2017], from several parameters which can be observed operationally in an airport:
- visibility level and change in time;
- local and regional cloud cover observed by satellite and ceilometer;
- vertical gradient of temperature.
We also conducted a study on the impact of the hydrated aerosols composing the mist: they can have a significant impact in radiative transfer in the fog as they contribute by ~20% in the visibility drop at the fog formation [Elias et al., 2009]; [Elias et al., 2015].
Extinction in the 2011/11/15 fog is caused not only by fog droplets but also by hydrated aerosols.
Funder: DGA via the RAPID scheme
Duration: 2010 - 2013
Contact at Hygeos: Thierry Elias