Coupled applications NAPS & Lewis models

1. Coupled applicationsNAPS & Lewis models Bob Sharman Becky Ruttenberg ATEC Forecaster Conference 27 July 2006

2. o o APG layout • 15 blast sites (x) • Tanks • Howitzers • Explosive detonations • Meteorological observations • 6 surface observation stations (o) • 1 upper air observation station (o s) • 18 microphone locations ( ) + o + x o x O S x x o o o x x o x x x x x x o x o o o o

3. Background • Sound propagation depends on effective speed of sound, controlled by: • Temperature stratification • Wind and wind shear • Ground absorption/reflection properties • Air absorption • Scattering by turbulence

4. Uniform atmosphere - wavefronts and rays Standard atmosphere + 0 winds Standard atmosphere + 20 m/s east wind

5. Effect of temperature inversions and wind shears wind Temperature inversion (0.8C/km) + 0 winds Standard atmosphere + west wind shear

6. Background: Effect of temperature inversions and wind shears on sound propagation Standard atmosphere + east wind Temperature inversion + east wind Standard atmosphere + east wind shear

7. sounding Effect of temperature inversions and wind shears (cont.) Uniform > 500m Uniform < 500m

8. 68 hour animation

9. APG Procedure • Use sound propagation model (Noise Assessment Prediction System – NAPS) • Acoustic ray-tracing package • Predicts peak overpressure • Includes terrain, surface contrasts • Input 1 sounding • Computes sound rays in azimuthal planes • Merges planes together to provide sound level (dB) contours • In use since early 1990s

10. Coupled MM5-NAPS spatial ensembles • Uncertainties in timing/location of mesoscale phenomena (e.g., sea breeze front) can lead to substantial gridpt-gridpt differences in MM5 pseudo-soundings • Use spatial ensembles to account for these uncertainties • Spatial ensemble consists of all pseudo-soundings within specified radius of blast site

11. Coupled MM5-NAPS spatial ensemble example (6,11) (14,9) (3,8) (9,9) (13,8) (12,13)

12. Coupled MM5-NAPS spatial ensemble example (cont.) Median dB Standard deviation dB Average dB >110 dB Probability >120 dB Probability

13. Lewis trajectory model • Inputs • RTFDDA winds • Month-specific RRA winds • Desired vertical resolution (layer.dat) • Rocket specific files (*.ini, *.txt) • Processing • Merge RTFDDA winds with RRA winds • Use Lewis method to compute downtrack and crosstrack deflections • Outputs • Merged winds, trajectory (booster + sustainer) • plots • output files (winds.dat, *.trj)

14. (a) (b) Example of RTFDDA-RRA wind merging (spatial ensemble)

15. Lewis trajectory model – used to adjust azimuth and elevation launch angle Desired impact point X Predicted impact point X wind z elev angle azimuth angle X X Desired impact point Predicted impact point downrange

16. Note: Coriolis deflection has 2 components This component (vertical) affects horizontal motions (e.g. winds) At mid-latitudes there are both components This component (horizontal) affects vertical motions Rockets are subject to both components: For nearly vertical launches horizontal component dominates and apparent deflection is to west in both hemispheres For nearly horizontal launches deflection is to right in N. hemisphere, to left in S. hemisphere In practice, sounding rockets are nearly vertical so horizontal component is the larger effect. Rotating earth

17. NP . Coriolis deflection on vertical projectile Apparent deflection westward (in both hemispheres)

18. Lewis method • Given winds, compute wind displacements crossrange (i=1), downrange (i=2) • Subtract displacements from no wind displacements • Add in Coriolis deflections • Compute corresponding azimuth and elevation angles

19. RTFDDA-GEM/Lewis spatial ensembles ensemble region Actual Impact RTFDDA 23hr fcsts 0 winds Rawin/ tower Rawin RAOB 362.27 launch 3Aug2005 1845 UTC

20. Lewis time history plots

21. Lewis output plots – impact scatter