3 - Centre National de Recherches Météorologiques - Météo France

New generation observationsand meso-scale modelfor aeronautical icing risk detectionDevelopmentfor a rain occurrencewarning productThe present work is conducted within thescope of FLYSAFE, a 4 year Integrated Projectof the 6 th framework of the EuropeanCommission started in February 2005. Inorder to increase aircraft safety, one of themain objectives of the FLYSAFE project is toimprove weather information supplied toflight crew members. In the frame of FLYSAFE,Météo France is currently improving its nowcastingtool for the detection of in-flight icingareas called SIGMA.Innovative SIGMA developments include theuse of new generation observations such asvolumetric radar images and high resolutionMeteosat Second Generation satellite imagery,as well as the new Météo-Francemesoscale non hydrostatic NumerocalPrediction Model AROME. SIGMA algorithmhas been redesigned to be able to takeA thunderstorm nowcastingsystem for improvingcommercial flights safetyThe aim of the European project Flysafe isto improve the New generation IntegratedSurveillance System for commercial flightsby 2015. The three risks addressed aremeteorological factors, collision with theterrain and collision between aircrafts.Among the meteorological phenomenaaddressed, thunderstorms are handledthrough the development of a prototype“Weather Information Management Systemfor Cbs”, which is led in cooperation withthe German DLR, the French ONERA, theBritish Met Office and the University ofHanoverMétéo-France with DLR addresses two spatialscales: the so-called Terminal ManoeuvringArea (TMA) and the regional (i.e.European) scale. The goal is to identify, todescribe and to forecast thunderstorms at aone hour range using an object representation,with a high refreshed rate. For the TMAadvantage of these new observation inputdata elaborated by CMS ( Centre de météorologieSpatial) and CMR (Centre de météorologieRadar).Owing to these new observations, moreemphasis is put on observations comparedto NWP input data, and supercooled liquidwater diagnostic is now enhanced.In parallel to the improved observations, thenew NWP model AROME produces humidityand temperature fields with a much betterspatial resolution as well as new microphysicsfields which are very useful for diagnosticsand the forecast of super cooled liquidwater areas.Work on calibration and evaluation of the newSIGMA algorithm will carry on in 2008 with twoflight tests campaigns to be held in Februaryand August 2008 in the scope of FLYSAFE. 15scale, the data used is mainly the advancedAramis radar network data: 3D scans andtheir 2D synthesis, and dual polarizationdata for hail detection; Doppler winds areused for detecting large wind shear. Theforecast of maximum thunderstorm cell topis based on thermodynamic profile analysis.For the European scale, a radar mosaicis used, which includes data from neighbouringcountries, while handling their timeshift. Regarding the evaluation, diagnosedthunderstorm objects are checked againstcloud-to-ground lightning data, and againstthunderstorm objects diagnosed usingsatellite data. Forecast thunderstormsobjects are diagnosed using a newapproach which allows for uncertainty intime and in space.During 2008, a further evaluation will implyon-board radar data collected during aflight test experiment. 16In order to open a rain occurrence warningservice, we have settled and assessed a rainnowcasting suite. The service is specific toeach of the 38.000 French municipalities. Itcombines a warning message one hourbefore it rains, and gives more detailedinformation on the forecast rain time series.The forecast method is based on rain patternsmovements analysis using a radarmosaic, followed by an extrapolation of thenational rain depth radar estimate. Raindepth are translated in space without achange in magnitude. Using the rain depthestimate allows to benefit from its pixel-specificquality data, and the observation qualitycan hence be dynamically translated inservice quality.It was evaluated with 4 months of data,using the actual rain depth estimate as thereference. The criteria used were userorientated,and their median values werecomputed among all the municipalities;the false alarm rate amounts to 37 %,which is acceptable; the non-detectionrate is remarkably low (3 %) and the meananticipation before rain starts is 25minutes, which is below the objective. Thisnowcast is actually difficult because itaddresses quite low levels of rain. As thequality is not homogeneous over the country,this leads to open the service for only alimited part of the territory.Plans for 2008 include the use of animproved rain depth estimate, on deepeningand enlarging the evaluation, and onimprovement addressing the remainingshortcomings. 1712 . Research and development: annual report 2007