Acoustic Forecasts for 24 August 1200Z, 900Hz and 600Hz, Issued 24 August 2009

This modeling is to designed show the acoustic variability computed using predicted oceanography over the QPE Acoustic Area. The purpose of the work is to provide a better insight into the oceanographic variability for the purpose of sensor placement. In order to do so, a 56km by 33 km rectangle area is chosen for such acoustic modeling, which covers most interesting area for OMAS activities. A 31 by 31 point grid has been chosen. 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 estimated by using 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)

Based on TL (latitude,longitude,bearing,depth,range), expected range (R) of transmission for TL drop to 60 (+/-5)dB level and 80 (+/-5) dB level are estimated as R_60 (latitude,longitude,bearing,depth,range) and R_80 (latitude, longitude, bearing, depth,range). The mean and standard deviation (over depth or bearing angles) of those three variable are shown in the following figures.

900HzAcoustic Climate Maps - 60±5 db
Acoustic Climate Maps - 80±5 db
600HzAcoustic Climate Maps - 60±5 db
Acoustic Climate Maps - 80±5 db
 NetCDF Files

Fcst. for 24 Aug. 12Z - 900Hz
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 24Aug 000Z 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 24Aug 000Z 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 24Aug 000Z 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 24Aug 000Z 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		      
     

Acoustic Climate Maps for a TL drop to 80±5 db
Expected Range (km) at fixed time ts for source at (xs,ys)
(Mean Range on 24Aug 000Z at which TL drops to 80±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 24Aug 000Z at which TL in cross-slope direction drops to 80±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 24Aug 000Z at which TL in along-slope direction drops to 80±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 24Aug 000Z at which TL drops to 80±5 db for receiver at 27m depth, averaged over all bearings, for source at 900Hz, 60m)
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 Expected Range		      
     

Fcst. for 24 Aug. 12Z - 600Hz
Acoustic Climate Maps for a TL drop to 60±5 db
TL(xs,ys,ts)
(TL (db) for source at 600Hz, 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 24Aug 000Z at which TL drops to 60±5 db averaged over all bearings and 51-71m depths, for source at 600Hz, 60m)		 Expected Range (km) in cross-slope direction at fixed time ts for source at (xs,ys)
(Mean Range on 24Aug 000Z at which TL in cross-slope direction drops to 60±5 db averaged over 51-71m depths, for source at 600Hz, 60m)		 Expected Range (km) in along-slope direction at fixed time ts for source at (xs,ys)
(Mean Range on 24Aug 000Z at which TL in along-slope direction drops to 60±5 db averaged over 51-71m depths, for source at 600Hz, 60m)		 Expected Range (km) at fixed time ts for source at (xs,ys) and receiver at 27m depth
(Mean Range on 24Aug 000Z at which TL drops to 60±5 db for receiver at 27m depth, averaged over all bearings, for source at 600Hz, 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		      
     

Acoustic Climate Maps for a TL drop to 80±5 db
Expected Range (km) at fixed time ts for source at (xs,ys)
(Mean Range on 24Aug 000Z at which TL drops to 80±5 db averaged over all bearings and 51-71m depths, for source at 600Hz, 60m)		 Expected Range (km) in cross-slope direction at fixed time ts for source at (xs,ys)
(Mean Range on 24Aug 000Z at which TL in cross-slope direction drops to 80±5 db averaged over 51-71m depths, for source at 600Hz, 60m)		 Expected Range (km) in along-slope direction at fixed time ts for source at (xs,ys)
(Mean Range on 24Aug 000Z at which TL in along-slope direction drops to 80±5 db averaged over 51-71m depths, for source at 600Hz, 60m)		 Expected Range (km) at fixed time ts for source at (xs,ys) and receiver at 27m depth
(Mean Range on 24Aug 000Z at which TL drops to 80±5 db for receiver at 27m depth, averaged over all bearings, for source at 600Hz, 60m)
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 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 Aug24-00Z  MIT_phys_2009082300_2009082400_2009082600_03h.nc.gz
Acoustics Fcst for Aug24-00Z 600Hz MIT_acoustic_TL_2009082300_2009082412_2009082412_00h_600.nc.gz
900Hz MIT_acoustic_TL_2009082300_2009082412_2009082412_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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