The meteorological part in the european project DELICAT - DEmonstration of LIdar based Clear Air Turbulence

Turbulence is a serious problem that affects airlines operations. The latest studies show an increase of the accidents number 3 times greater than the air traffic evolution. This situation is likely to worsen due to the development of the traffic in the near future. Among various types of turbulence, clear air turbulence (CAT) is the most difficult to avoid, as it can not be detected visually by the pilot. To improve the onboard detection of CAT, the DELICAT (DEmonstration of LIdar based Clear Air Turbulence) project has been funded by the seventh framework program (FP7) of the European Commission. Thirteen partners representing various fields of activity, research centers, industries, universities, and meteorological centers are involved in this project for a period of three years (2009-2012). The objective is to validate the concept of onboard LIDAR based medium-range turbulence detection (10 km to 30 km detection of turbulence which allows securing the passengers and the crew members by seat belts fastening). During the DELICAT project the LIDAR will be installed onboard the NLR research aircraft for a flight test campaign. The LIDAR data will then be compared with the aircraft sensors (acceleration, air speed, temperature) collected during the flight test along the flight path.

Along the project the meteorological expertise is brought by Météo-France and ICM (Interdisciplinary Centre for Mathematical and Computational Modelling - Warsaw University). To support the choice of the best locations and periods for the flight test campaign, CAT indices climatologies have been elaborated by using among others, the ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis database (1989-2008). The chosen CAT indices Ellrod (1 and 2), based on the product of horizontal deformation (completed by the convergence term in the Ellrod2 index) and vertical wind shear derived from the numerical model wind forecast, are often used operationally by the forecasters. For each month, maps have been provided for different vertical flight levels covering the world as well as a focus on Europe. Those climatologies were compared with short term wind speed climatology covering North Atlantic and Europe based on the COAMPS NWP model.

Another part of the work is the improvement of the turbulence nowcasting systems. A study will evaluate the impact of the increased resolution of the NWP model. Some CAT indices will be calculated and compared with the AMDAR (Aircraft Meteorological DAta Relay) turbulence measurements during the first months of 2010. Also machine learning based CAT predictor will be tested this way. A meteorological assistance will be provided during the flight tests in order to help in the good progress of the project. Last but not least, the flight test campaign will give the opportunity to verify the indices previously selected by using all the aircraft sensors data and also the LIDAR measurements.