Acoustic Forecasts for 900Hz on 5 September 1500Z and 2100Z, Issued 4 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

First, we focus below on the 130m isobath (see plot with location), which is the a priori chosen location of the acoustic sampling for this Day 2 of Leg 2. In these plots, reciprocity is used. Two of the images below at each time are vertical sections, which contain a 2D color plot and a 1D std over depth. One image corresponds to an eastward propagation, the other to a westward propagation. Consider the eastward propagation, for example. The 2D color section indicates that if the receiver is at a given depth and lat-lon (a pixel in the 2D plot), it will hear a source at 6-8km to the west (to the left) with XX db (as colored in the pixel). Also shown is the standard deviation with depth.

130m Location Mean TL Over Time - Eastward Propagation Mean TL Over Time - Westward Propagation
TL Vertical Sections - 5 September - 1500Z
Mean Eastward Propagation Mean Westward Propagation TL Field Eastward Propagation TL Field Westward Propagation
TL Vertical Sections - 5 September - 1800Z
Mean Eastward Propagation Mean Westward Propagation TL Field Eastward Propagation TL Field Westward Propagation
TL Vertical Sections - 5 September - 2100Z
Mean Eastward Propagation Mean Westward Propagation TL Field Eastward Propagation TL Field Westward Propagation

Fcst. for 5 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 51-71m depths)		 Expected Range (km) at fixed time ts for source at (xs,ys)
(Mean Range on 05Sep 15Z at which TL drops to 60±5 db averaged over all bearings and 51-71m 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 05Sep 15Z at which TL in cross-slope direction drops to 60±5 db averaged over 51-71m 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 05Sep 15Z at which TL in along-slope direction drops to 60±5 db averaged over 51-71m 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 05Sep 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 5 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 51-71m depths)		 Expected Range (km) at fixed time ts for source at (xs,ys)
(Mean Range on 05Sep 18Z at which TL drops to 60±5 db averaged over all bearings and 51-71m 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 05Sep 18Z at which TL in cross-slope direction drops to 60±5 db averaged over 51-71m 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 05Sep 18Z at which TL in along-slope direction drops to 60±5 db averaged over 51-71m 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 05Sep 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 5 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 51-71m depths)		 Expected Range (km) at fixed time ts for source at (xs,ys)
(Mean Range on 05Sep 21Z at which TL drops to 60±5 db averaged over all bearings and 51-71m 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 05Sep 21Z at which TL in cross-slope direction drops to 60±5 db averaged over 51-71m 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 05Sep 21Z at which TL in along-slope direction drops to 60±5 db averaged over 51-71m 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 05Sep 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 4-6  MIT_phys_2009090208_2009090400_2009090600_03h.nc.gz
Acoustics Fcst for Sep05 1500Z MIT_acoustic_TL_2009090208_2009090515_2009090515_00h_900.nc.gz
1800Z MIT_acoustic_TL_2009090208_2009090518_2009090518_00h_900.nc.gz
2100Z MIT_acoustic_TL_2009090208_2009090521_2009090521_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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