QPE Acoustics Working Group Report Phil Abbot OASIS

QPE Acoustics Working Group Report Phil Abbot, OASIS QPE Uncertainty DRI 2 nd Mtg Washington, DC 18 – 19 June 2007

Outline • Background: Passive Sonar Equation • Recent Results – SW 06/AWACS – LWAD 06 -1 Tests Close to QPE Site • Answer the Chief’s Questions

Passive Sonar Equation “Energy” Bookkeeping SNR = S – N = SL – TL – N at initial detection, SNR RD (if one sets SL – TL – N – RD = 0 then, FOM TL = SL – N – RD) QPE Focus: TL, N (Ambient Noise), Spatial. Temporal Coherence, 100 to 1, 000 Hz, SW

Recent SW 06/AWACS New Jersey Results: Environmental Uncertainty Keys • Mixed Layer Depth • Cross-Shelf Temperature Gradients - 40 m depth and Cross-shelf position of Shelfbreak Front • Depth of Temperature minimum (Cold Pool) and Mid-depth Duct • Position of Foot of Shelfbreak Front (Maximum Cross-shelf Temperature Gradients along bottom)

Daily Hydrographic Mapping and Adaptive Sampling 80 m isobath Mixed layer depth considerably deeper off shore Shelfbreak front extends seaward over upper slope Shelfbreak front moved seaward after TS Ernesto

OMAS Measured Tracks During AWACS/SW 06 7. 5 nmi Tracks based on Objective Maps and Ocean Adaptive Sampling of Environmental Keys (i. e. frontal position, cold pool duct, mixed layer depth)

AWACS/SW 06 TL Example: Horizontal Isotropy and Translational Invariance Tests TL (PMFO) @ R = 7. 5 km, f=900 Hz 7. 5 nmi OMAS 1 OMAS 2 SB Front Shelfbreak Front – Obj. Map Means in 150 Sectors TL @ R = 7. 5 km, f=900 Hz TL means robustly constant except where interacting with Shelfbreak Front. Horizontally Isotropic: ~ Yes. Translationally Invariant: Up to 7. 5 nmi SB Front

LWAD 06 -1 Site for TL Measurements using OMAS, July 2006 200 m Site 2 Site 1 1000 m 2000 m TAIWAN Bottom Bounce Site ETOPO 2 Bathy, in meters

Site 2, Temperature and Sound Speed Profiles, XCTD (1, 3, 4 and 5) and XBT (2) Temperature Sound Speed Profile Intrusions 5 2 4 Gradient 1 1 3 MLD 5 BML 3

Measured Integrated TL, Site 2, Mean TL and Histogram 550 Hz, Df = 100 Hz Ds = 27. 4 m DR = 27. 4 m Dw 110 m N = 134 s = 1. 6 d. B Mean TL

Measured Integrated TL, Site 2, Mean TL and Histogram 950 Hz, Df = 100 Hz Ds = 27. 4 m DR = 27. 4 m Dw 110 m N = 240 s = 1. 9 d. B Mean TL

Measurement and Model Comparisons, 550 and 950 Hz, ECS Bottom Model (Ref. Abbot) with ~ f 1. 8 Measurement f = 950 Hz f = 550 Hz Model Measurement Inconsistent Bottom Geoacoustic Model – What’s the Geoacoustics?

Suggested Environmental Keys: South ECS QPE Tests • Surface Mixed Layer Depth • Cross-shelf Temperature Gradients 40 m depth (TBD) and Cross-shelf position of Kuroshio • Bottom Mixed Layer Depth • Depth of Temperature minimum within Thermocline • Cool Pool and Mid-depth Ducts, if exists • Fishing Activity

Acoustic Tools • OMAS w/Sonobouys (LBL and TL) • Fixed Sources, Moored and From Ship • 4 Channel SHRUs (Single Hydrophone Receiver Units) • Bottom-Mounted HLA (Horizontal Line Array) • Cheap/Simple T-Moorings • REMUS and Gliders w/ Single Hydrophone Simple and Easy to Deploy

SLOCUM and REMUS Vehicles

Float SBE 39 T/P Micro. CAT T T T Synthetic T Micro. CAT ADCP P (tide/wave) BACS release CART release (60 m) LOCO-II (28) ENVIR. (6)

WHOI Single Hydrophone Recorder Unit (SHRU)

OASIS Mobile Acoustic Source (OMAS) OMAS Characteristics Precision Clock Calibrated Sound Source Specialized Acoustic Transmissions, w/Detection Signals LBL Tracking Systems Field Demonstrations SCORE Range 04 South China Sea 05, ECS 06 New Jersey Experiments 05, 06 Patent Pending: filed 1/4/07 Standard EMATT (LM Sippican) Length: 91. 4 cm (36”) Diameter: 12. 4 cm (4. 9”) Weight: 10 kg (22 lbs) Battery Power: Li. SO 4 Operational Characteristics Depth: 23 – 183 m, 5 m (75 - 600 ft) Speed: 1. 5 – 4 m/s (3 - 8 Knots) Endurance: 3 to 6 hrs, Speed Dependent Launch: Handheld

Probabilistic Performance Prediction Method Systems-based PDF (convolution of all PDFs, incorporates environmental and system uncertainty) : mean terms in sonar equation s: set by fluctuations of each term n: local slope of the TL~ Rn

Predictive Probability Of Detection, PPD FOM = 85 d. B First Order Approximation Prediction is controlled by 3 parameters: , and n (minimum)

Suggested Physical Oceanography/Acoustic Test Area, Including Possible OMAS Tracks (D 20 km) Acoustic Test Area (50 x 50 km)

Time of Year, Acoustic Scales • May/June, Depending on Typhoon Season and Location of Fishing Fleet • Acoustic Scales: – O(< 50 km) – Minutes to Hours to Days

Features to Exploit for Acoustics (Key Hypotheses) • Positions of: – – Gradients Kuroshio Cool Dome Mixed Layer vs. Thermocline • Bottom Sediment Variability, Shelf to Shelfbreak • Local Shipping and Sea Surface Conditions • Effects of Internal Waves

Further Needs • Pilot Cruise to address: – Effects of Kuroshio Intrusion, Cold Dome – Noise Directionality, including Local Fishing – Bottom Bathymetry and Geoacoustics Develop Baseline of Key Environmental Effects in 08 in Order to Exploit in 09

Backups

NJ Shelf 2006, D = 80 - 120 m, f = 900 Hz, Replica Processed 12. 5 km OMAS 1 OMAS 2 Means in Fron 150 Sectors t Sectors Transmission vs b Measured at R = 7. 5 km is Horizontally Isotropic When Smoothed In 150 Sectors, and has Isobathic Translational Invariance Up to 12 km, Again In 150 Sectors For bearings not including the front Data by Abbot, Emerson, Gedney

Means in 50 Windows Show the L 1 Length-Scale NJ Shelf 2006 Transmission at R = 7. 5 km, f = 900 Hz L 1 2 km, and distinct for all b L 1 scale indistinct for all b Why is this Pattern more diffuse? Front sectors The Previous 12 km Isobathic Translational Invariance of the Means Smoothed in 150 Windows gives way here, in 50 Windows, to Fluctuations of the Data that are Not Invariant To Isobathic Translation Data by Abbot, Emerson, Gedney

Individual CTD Casts for LWAD Site 2 Freq = 550 Hz Zs = 27. 4 m Zr = 27. 4 m (OMNI/DIFAR) Comparison of RAM Model Results Using Different Sound Speed Profiles Range Dependent Interpolated SSP from the Individual Casts

ECS Geoacoustic Model. 2 d. B/l @ 550 Hz Zs = 27. 4 m Zr = 27. 4 m (OMNI/DIFAR) 1690 m/s 1. 89 g/cc . 53 d. B/l @ 950 Hz 1740 m/s Full Field Model Results, f = 550 Hz Full Field Model Results, f = 950 Hz 2100 m/s (basement) 2. 03 g/cc (basement)