Acoustic Forecasts for 900Hz on 9 September 1500Z, 1800Z and 2100Z, Issued 7 September 2009

This page shows our acoustic variability predictions computed using our predicted ocean state over the QPE Acoustic/OMAS Area. The purpose is to guide acoustic sensor placement. The acoustic modeling covers a 56km by 33 km rectangle area with a 31 by 31 grid resolution. A source (900 and 600 Hz frequency) is placed at each grid point and sound is propagated to 15 km distance in 8 different directions (with 45 degree intervals). An N(=8) by 2D transmission loss TL(latitude,longitude,bearing,depth,range) at each grid point is forecast using the parabolic equation Range-dependent Acoustic Model (RAM). A two-layer depth-dependent geo-acoustic model is applied here: 20 m deep sediment layer on the top of basement with sound sound speed (c) 1,800 m/s, density (ρ) 2.0 g/cm3 and attenuation (α) 0.5 dB/λ.

The sediment type depends on the local water depth (WD) : 

WD < 140m: Sand sediment (sound speed ratio: 1.038, ρ: 1.90 g/cm3, α: 0.9 dB/λ)
140m < WD < 210m: Muddy-sand (sound speed ratio: 1.021, ρ: 1.76 g/cm3, α: 1.15 dB/λ)
210m < WD: Mud (sound speed ratio: 0.980 , ρ: 1.42 g/cm3, α: 0.1 dB/λ)

1500ZAcoustic Vertical Sections
Acoustic Climate Maps - 60±5 db
1800ZAcoustic Vertical Sections
Acoustic Climate Maps - 60±5 db
2100ZAcoustic Vertical Sections
Acoustic Climate Maps - 60±5 db
 NetCDF Files

Fcst. for 9 Sep. 15Z
Acoustic Climate Maps for a TL drop to 60±5 db
TL(xs,ys,ts)
(TL (db) for source at 900Hz, 60m averaged over all bearings, 6-8km ranges and 20-100m depths)		 Expected Range (km) at fixed time ts for source at (xs,ys)
(Mean Range on 09Sep 15Z at which TL drops to 60±5 db averaged over all bearings and 20-100m depths, for source at 900Hz, 60m)		 Expected Range (km) in cross-slope direction at fixed time ts for source at (xs,ys)
(Mean Range on 09Sep 15Z at which TL in cross-slope direction drops to 60±5 db averaged over 20-100m depths, for source at 900Hz, 60m)		 Expected Range (km) in along-slope direction at fixed time ts for source at (xs,ys)
(Mean Range on 09Sep 15Z at which TL in along-slope direction drops to 60±5 db averaged over 20-100m depths, for source at 900Hz, 60m)		 Expected Range (km) at fixed time ts for source at (xs,ys) and receiver at 27m depth
(Mean Range on 09Sep 15Z at which TL drops to 60±5 db for receiver at 27m depth, averaged over all bearings, for source at 900Hz, 60m)
Std Dev in Depth of TL Std Dev in Depth
of Expected Range		 Std Dev in Depth
of Expected X-Slope Range		 Std Dev in Depth
of Expected Along-Slope Range		 Std Dev in Bearing
of Expected Range for 27m Receiver
Std Dev in Bearing of TL Std Dev in Bearing
of Expected Range		      
     

Fcst. for 9 Sep. 18Z
Acoustic Climate Maps for a TL drop to 60±5 db
TL(xs,ys,ts)
(TL (db) for source at 900Hz, 60m averaged over all bearings, 6-8km ranges and 20-100m depths)		 Expected Range (km) at fixed time ts for source at (xs,ys)
(Mean Range on 09Sep 18Z at which TL drops to 60±5 db averaged over all bearings and 20-100m depths, for source at 900Hz, 60m)		 Expected Range (km) in cross-slope direction at fixed time ts for source at (xs,ys)
(Mean Range on 09Sep 18Z at which TL in cross-slope direction drops to 60±5 db averaged over 20-100m depths, for source at 900Hz, 60m)		 Expected Range (km) in along-slope direction at fixed time ts for source at (xs,ys)
(Mean Range on 09Sep 18Z at which TL in along-slope direction drops to 60±5 db averaged over 20-100m depths, for source at 900Hz, 60m)		 Expected Range (km) at fixed time ts for source at (xs,ys) and receiver at 27m depth
(Mean Range on 09Sep 18Z at which TL drops to 60±5 db for receiver at 27m depth, averaged over all bearings, for source at 900Hz, 60m)
Std Dev in Depth of TL Std Dev in Depth
of Expected Range		 Std Dev in Depth
of Expected X-Slope Range		 Std Dev in Depth
of Expected Along-Slope Range		 Std Dev in Bearing
of Expected Range for 27m Receiver
Std Dev in Bearing of TL Std Dev in Bearing
of Expected Range		      
     

Fcst. for 9 Sep. 21Z
Acoustic Climate Maps for a TL drop to 60±5 db
TL(xs,ys,ts)
(TL (db) for source at 900Hz, 60m averaged over all bearings, 6-8km ranges and 20-100m depths)		 Expected Range (km) at fixed time ts for source at (xs,ys)
(Mean Range on 09Sep 21Z at which TL drops to 60±5 db averaged over all bearings and 20-100m depths, for source at 900Hz, 60m)		 Expected Range (km) in cross-slope direction at fixed time ts for source at (xs,ys)
(Mean Range on 09Sep 21Z at which TL in cross-slope direction drops to 60±5 db averaged over 20-100m depths, for source at 900Hz, 60m)		 Expected Range (km) in along-slope direction at fixed time ts for source at (xs,ys)
(Mean Range on 09Sep 21Z at which TL in along-slope direction drops to 60±5 db averaged over 20-100m depths, for source at 900Hz, 60m)		 Expected Range (km) at fixed time ts for source at (xs,ys) and receiver at 27m depth
(Mean Range on 09Sep 21Z at which TL drops to 60±5 db for receiver at 27m depth, averaged over all bearings, for source at 900Hz, 60m)
Std Dev in Depth of TL Std Dev in Depth
of Expected Range		 Std Dev in Depth
of Expected X-Slope Range		 Std Dev in Depth
of Expected Along-Slope Range		 Std Dev in Bearing
of Expected Range for 27m Receiver
Std Dev in Bearing of TL Std Dev in Bearing
of Expected Range		      
     

UTC and Taiwan time conversion
UTC 0000 0300 0600 0900 1200 1500 1800 2100
CST 0800 1100 1400 1700 2000 2300 0200 (+1) 0500 (+1)

Available Forecast NetCDF Files
Physics Fcst for Sep 8-10  MIT_phys_2009090708_2009090800_2009091000_03h.nc.gz
Acoustics Fcst for Sep09 1500Z MIT_acoustic_TL_2009090708_2009090915_2009090915_00h_900.nc.gz
1800Z MIT_acoustic_TL_2009090708_2009090918_2009090918_00h_900.nc.gz
2100Z MIT_acoustic_TL_2009090708_2009090921_2009090921_00h_900.nc.gz

The file names can be interpreted as follows (all times are in UTC):

       time of last
      analysis field           time of last
      in simulation            fields in file
         yyyymmddHH            yyyymmddHH
MIT_phys_2009072512_2009072812_2009073000_03h.nc.gz
                    yyyymmddHH            HH
                   time of first        frequency with which
                   fields in file       fields are stored in file

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