Dirk Van MaerckeIMAGINE Final Conference, Budapest, Meteorological effects from theory till operational use… Dirk van Maercke CSTB 24, rue Joseph Fourier F Saint-Martin d’Hères FRANCE

Dirk Van MaerckeIMAGINE Final Conference, Budapest, Effects of meteorological conditions on sound propagation  Meteorology = state of the atmosphere in the lower boundary layer  Most important effects : vertical gradients of wind and temperature

Dirk Van MaerckeIMAGINE Final Conference, Budapest, Effects of meteorological conditions on sound propagation  NMPB : based on empirical classification by Zuboff Iso standards

Dirk Van MaerckeIMAGINE Final Conference, Budapest, The Harmonoise Reference Model 1) the complexity of reality 2) frozen atmosphere + turbulence 3) stratified medium 4) simplified wave equation + effective sound speed 5) approximation by lin-log sound speed profiles

Dirk Van MaerckeIMAGINE Final Conference, Budapest, Characterisation of meteorological profiles 1) the simplified reality … requires meteorological towers 2) similarity theory = standard profile functions + parameters … can be measured directly 3) estimation of parameters based on “surface” observations ~ standard approach in air pollution… Wind speed (at z = z ref ) Wind direction Cloud cover (in octants)

Dirk Van MaerckeIMAGINE Final Conference, Budapest, THE MONIN-OBUKHOV LENGTH SCALE characterises the strength of (in)stability due to thermal fluxes  1/L = 0Neutral (heavy clouds)  1/L < 0 Stable (night)  1/L > 0 Unstable (sunny day) night day stable cold warm cold warm

Dirk Van MaerckeIMAGINE Final Conference, Budapest, The Harmonoise Engineering Model Ex: Harmonoise validation 8 wind directions, 3 wind speeds, 5 stability classes = 120 calculations ! Surface observations :W,  W, S Meteorological profiles : 1/L, U*, T* Lin/Log sound speed profile A = A T + A W cos (  SR -  W ) B = B T + B W cos (  SR -  W ) Linear sound speed profile 1/R = 1/R A + 1/R B Linear sound speed profile 1/R = 1/R A + 1/R B Measurement Propagation - direction - distance

Dirk Van MaerckeIMAGINE Final Conference, Budapest, Linking meteorological parameters to acoustical effects  The effects depend on distance (D), ray curvature (R), height of source and receiver, ground impedance, presence of screening,…  Proposal: use D/R as the dimensionless parameter to characterize the importance of meteorological effects on propagation Note:  H/D ~ D/R R

Dirk Van MaerckeIMAGINE Final Conference, Budapest, m 100 m 250 m 500 m h S = 0.3 m h R = 2.5 m  = 200 kRayls Simulation based on 250 random samples Meteorological effects versus distance…

Dirk Van MaerckeIMAGINE Final Conference, Budapest, How many classes ? 250 random samples 5 classes + turbulence

Dirk Van MaerckeIMAGINE Final Conference, Budapest, COMBINED EFFECTS OF WIND AND TEMPERATURE GRADIENTS Very favourable Favourable Neutral Unfavourable Very unfavourable  RMV-II  NMPB

Dirk Van MaerckeIMAGINE Final Conference, Budapest, Propagation classes Calculation of L den : based on frequency of occurrence

Dirk Van MaerckeIMAGINE Final Conference, Budapest, What should be measured / calculated ?  meteorological effect depend on distance, source/receiver height and frequency of occurrence Simulation 1 : flat ground, low source

Dirk Van MaerckeIMAGINE Final Conference, Budapest, What should be measured / calculated ?  meteorological effect depend on distance, source/receiver height and frequency of occurrence Simulation 2 : high source or embankment (2m)

Dirk Van MaerckeIMAGINE Final Conference, Budapest, Determination of L den and L night  Calculation and measurements:  Calculation:  Calculation of L den and L night requires (only) 4 calls to the P2P module, even less if p ij = 0 (short distances, high sources)

Dirk Van MaerckeIMAGINE Final Conference, Budapest, Meteorological Pre-processor Frequency of occurrence p ij Wind speed, Wind direction Cloud cover Day hours Evening hours Night hours Propagation distance Propagation direction Source/receiver height Meteorological data records (1 year in steps of 1 hour) Determination of frequency of occurrence per propagation class

Dirk Van MaerckeIMAGINE Final Conference, Budapest, That’s it, folks…