Test of a combined X-band Doppler polarimetric radar & Doppler lidar system for all-weather wind shear detection at Nice Airport

Abrupt changes in the wind velocity or direction near the ground can cause serious hazards to aircraft during approach or departure operations. That is why the French Air Navigation Service Provider (DSNA) is requesting Météo France to design reliable, appropriate and cost-efficient technical solutions to detect, quantify and alert on the presence of low-level wind shear at a number of French airports. The Nice-Côte d'Azur airport has been chosen as the first evaluation platform of the solutions proposed by Météo France. Its location between sea and mountains and the runway directions parallel to the coast line are main reasons for either clear air or convection wind shears disturbing air traffic. A first real-time experiment was carried out in 2009 and confirmed the capacity of a Doppler lidar set-up at the airport to detect and monitor wind shears in clear air conditions up to significant ranges (8 – 10 km), but also the range coverage reduction of the lidar in cases of precipitation. Consequently, decision was taken to perform another real-time experiment in 2011 combining both a Doppler lidar and an X-band Doppler polarimetric radar, in order to have an all-weather detection and monitoring of wind shears around the airport. This approach is in line with several past or ongoing developments elsewhere in the world, such as the integration of lidar alerts inside the FAA wind-shear detection system in the USA, the instrumental set-up of the Hong-Kong airport or the German project to equip the airports of Munich and Frankfurt with lidar-radar couples. This experimentation, named « Nice 2011 », started in March 2011 with the installation of a Doppler lidar at Nice airport. An X-band Doppler polarimetric radar is going to be set up in May. The experiment will last 6 months in order to test the radar, lidar system in a variety of situations. The aim of this experimentation is to evaluate the contribution of these instruments, in association with the « traditional » systems like the ground stations, to the development of a detection and alert system. We would like in particular to evaluate the necessary level of automation, the role of the forecaster and the kind of products best suited to air control management. The first stage will be to evaluate the performance of the instruments and their operation and maintenance conditions. On the radar side, some key technical questions are: can the radar be placed at the airport or is it preferable to place it a few kilometres away from the airport? What are the required and the ideal revisit time for accurate wind shear monitoring? What is the optimal scan strategy (elevation angles) of the radar? What waveform and signal processing should be used at X-band to obtain high-quality Doppler winds with no range folding, large Nyquist velocities and minimal ground-clutter / sea clutter contamination? The algorithms proposed by the constructors will be evaluated on a number of representative meteorological conditions and some preliminary specifications will be given for the development of an alert system.