HYSPLIT Forum: hysplitbbs.arl.noaa.gov

When I use the gdas0p5,55 levels.In the info.txt says
55 hybrid sigma-pressure Levels
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0.9999, 0.9947, 0.9886, 0.9817, 0.9739,
1.9648, 1.9544, 2.9425, 4.9288, 6.9132,
8.8954, 11.875, 16.853, 21.827, 26.799,
33.769, 41.735, 49.699, 59.660, 69.619,
80.576, 91.531, 102.49, 113.44, 123.39,
133.35, 143.30, 151.26, 157.22, 162.18,
165.15, 166.12, 165.09, 162.07, 157.05,
150.04, 142.02, 132.01, 122.01, 111.00,
99.002, 88.000, 78.000, 68.000, 59.000,
52.000, 45.000, 39.000, 34.000, 29.000,
25.000, 21.000, 18.000, 15.000, 13.000

The pressure level is defined as: P = A + B*PRSS,
where PRSS is the surface pressure and A.B is defined as the level
(ie., 16.9640 = 980 hPa when the surface pressure is 1000 hPa)
Who knows the A,B Value?

A is the number to the left of the decimal point and B is the number to the right of the decimal point including the decimal point in the list of hybrid sigma-pressure levels. For example, 33.769 as given in the table gives a letter A of 33 and B of 0.769, therefore assuming surface pressure is 1000 hPa the pressure level is 33+0.769*1000= 782 hPa.

Thanks very much!