1
$\begingroup$

Taking a sounding prediction from GFS 1° horizontal resolution(from ready.arl.noaa.gov) with normal pressure levels looks like this:

PRESS HGT(MSL) TEMP DEW PT  WND DIR  WND SPD
 HPA       M      C     C       DEG     M/S  
 E = Estimated Surface Height

  969.   438.    6.7    5.4   358.8     3.3
  950.   586.    5.1    4.4     1.8     5.0
  925.   803.    3.6    3.0    14.6     5.5
  900.  1025.    2.2    1.7    28.8     6.6
  850.  1485.   -0.2   -0.4    48.6     9.7
  800.  1970.   -2.2   -2.5    60.6    11.1
  750.  2480.   -4.6   -4.9    66.1    11.3
  700.  3020.   -7.0   -7.3    65.0    11.0
  650.  3597.   -8.9   -9.4    63.7    11.5
  600.  4215.  -10.9  -13.8    72.1    11.7
  550.  4878.  -15.3  -20.1    76.3     9.3
  500.  5591.  -20.6  -22.6    87.2     7.3

But doing the same with GFS 0.25° horizontal resolution that is given only in Hybrid-sigma pressure levels seems like this(for the same area and time and GFS run):


    PRESS HGT(MSL) TEMP DEW PT  WND DIR  WND SPD
     HPA       M      C     C       DEG     M/S  
     E = Estimated Surface Height

      998.   186.E
      995.   213.E   7.6    5.9    34.7     2.1
      990.   287.E   7.5    5.5    33.3     3.1
      983.   369.E   7.0    5.0    35.3     3.6
      975.   475.E   6.6    4.4    34.1     4.3
      967.   575.E   6.1    3.8    31.6     4.8
      958.   686.E   5.6    3.4    31.9     5.2
      948.   828.E   5.1    2.9    29.9     5.6
      936.   982.E   4.4    2.3    33.9     6.0
      923.  1147.E   3.8    1.9    36.5     6.7
      908.  1355.E   3.0    1.5    41.6     8.0
      893.  1572.E   2.2    1.2    46.3     9.4
      875.  1827.E   1.2    0.7    51.2    10.7
      856.  2111.E   0.3   -0.1    55.3    11.5
      835.  2426.E  -0.5   -0.9    59.1    11.9
      811.  2795.E  -1.5   -1.8    61.9    11.7
      786.  3189.E  -2.5   -2.8    64.3    11.2
      760.  3610.E  -3.9   -4.3    65.7    11.1
      731.  4093.E  -5.2   -5.6    65.7    11.1
      701.  4608.E  -7.7   -8.1    65.6    11.4
      670.  5168.E  -8.5   -8.9    67.9    12.2
      637.  5789.E  -9.2   -9.9    67.0    13.0
      603.  6443.E -11.1  -12.6    64.4    13.0
      568.  7135.E -14.0  -15.4    64.4    11.0
      533.  7863.E -17.6  -19.2    82.7     8.0
      498.  8582.E -20.8  -25.2    98.2     8.0

First normal sounding says that GFS's prediction about where 500 hPa would lie is 5591 meters geopotential height. Which is a normal value. But the 2nd sounding with hybrid-sigma pressure levels says 498≈500 hPa level is on 8582 meters which is absurd.

So my question is how to convert geopotential heights of the hybrid-sigma pressure levels to normal in order to know where the real height of e.g 850 hPa is? Since i can find from 1st sounding at which heights 850 hPa lies, but from the 2nd i can't.

Or how to convert hybrid-sigma pressure levels to normal pressure levels?

Ready.ARL.NOAA has a guide(https://ready.arl.noaa.gov/READYmetdata.php) of what hybrid-sigma-levels correspond to GFS, but it doesn't seem to provide a way of doing anything of what i want.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.