Ray trace with a sound speed field

The latest version of Bellhop allows calculations with a sound speed field, which is going to be illustrated here with a ray calculation only. Let us create a gulf.env input file, which look like follows:

'Gulf sound speed field'
50.0
1
'QVW'
0 0.0 5000.0
    0.0  1536.00 /
  200.0  1506.00 /
  700.0  1503.00 /
  800.0  1508.00 /
 1200.0  1508.00 /
 1500.0  1497.00 /
 2000.0  1500.00 /
 3000.0  1512.00 /
 4000.0  1528.00 /
 5000.0  1545.00 /
'A' 0.0
 5000.00   1800.0  0.0  2.0  0.1 0.0
1				! NSD
300.0 /			        ! SD(1:NSD) (m)
101				! NRD
0.0 5000.0 /			! RD(1:NRD) (m)
1001				! NR
0.0  200.0 /			! R(1:NR ) (km)
'R'	  			! 'R/C/I/S'
51				! NBeams
-10.0 10.0 /		        ! ALPHA1,2 (degrees)
0.0  5500.0 201.0		! STEP (m), ZBOX (m), RBOX (km)

Setting OPTIONS1(1) = 'Q' allows to take into account a sound speed field, named gulf.ssp which looks like follows (the syntax is self describing):

8
0.0     12.5    25.0    37.5    50.0    75.0    100.0   125.0
1536	1536	1536	1536	1536	1536	1536	1536
1506	1508.75	1511.5	1514.25	1517	1520	1524	1528
1503	1503	1503	1502.75	1502.5	1502	1502	1502
1508	1507	1506	1505	1504	1503	1501.5	1500
1508	1506.6	1505	1503.75	1502.5	1500.5	1499	1497
1497	1497	1497	1497	1497	1497	1497	1497
1500	1500	1500	1500	1500	1500	1500	1500
1512	1512	1512	1512	1512	1512	1512	1512
1528	1528	1528	1528	1528	1528	1528	1528
1545	1545	1545	1545	1545	1545	1545	1545

Running Bellhop with this input file allows to get Fig.7.

Figure 7: Rays calculated by Bellhop with a sound speed field.