Question about pressure layering

[Lanhui Sun]

I encountered an error during the execution, but I have already checked the settings for NLEVELS and NPROF, and they match the values in the prof.dat file
“enter number of threads to use
2024/09/04 14:32:42 Open scattering coefficient file ../../rtcoef_rttov13/hydrotable/hydrotable_fy3_mwhs2e.dat
2024/09/04 14:32:45 fatal error in module rttov_iniscatt
iniscatt : problem with user-defined pressure layering
2024/09/04 14:32:45 fatal error in module rttov_scatt
error in rttov_iniscatt
rttov_scatt error
1

TEST FAILED: Error during the execution of example_rttovscatt_fwd.exe
”
Any assistance with resolving this issue would be greatly appreciated.

[James Hocking]

Hi,

This error can occur if you have more than one pressure half-level (cld_profiles(:)%ph(:)) that is smaller than 0.004985 hPa. You would also have problems if more than one pressure level (profiles(:)%p(:)) was smaller than this value.

What are the pressure levels and half-levels in your profile?

Best wishes,
James

[Lanhui Sun]

Thank you very much for your reply! I checked, and the pressure values for each of my profiles are mostly between 50 hPa and 1000 hPa. Here is a part of the profile data.
”
! p ph t q cc clw ciw rain snow
! [hPa] [hPa] [K] [ppmv] [0-1] [kg/kg] [kg/kg] [kg/kg] [kg/kg]
0.519E+02 0.000E+00 0.212E+03 0.134E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.559E+02 0.539E+02 0.211E+03 0.117E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.601E+02 0.580E+02 0.210E+03 0.130E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.647E+02 0.624E+02 0.209E+03 0.153E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.696E+02 0.672E+02 0.207E+03 0.175E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.749E+02 0.723E+02 0.206E+03 0.212E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
”
I am considering whether it is related to the following two commands that interpolate the pressure values.
opts%interpolation%addinterp = .TRUE.
opts%interpolation%reg_limit_extrap = .TRUE.

[James Hocking]

Hi,

I should have also said that it is important that no two pressure levels are equal and that no two pressure half-levels are equal: they must each be strictly monotonically increasing starting from index 1. You need to check your whole profile, or copy all the profile data here so I can see it (including the surface parameters).

In your profile extract above, you seem to have a top pressure half-level at 0 hPa, and then the second one is at about 54 hPa: you may see large errors in the simulations by not representing the atmosphere between 0 and 54 hPa. If any channels that you are simulating have significantly non-zero weighting functions in this region of the atmosphere (quite likely to be true), the simulation errors will be large. Generally you should try to provide a reasonable representation of the whole atmosphere in the profile. That said, this should not cause the error message you are seeing.

When you run RTTOV-SCATT, you should specify options in the rttov_options_scatt derived type (the variable “opts_scatt” in example_rttovscatt_fwd.F90), rather than in the rttov_options derived type as you have indicated above.

RTTOV-SCATT automatically enables the RTTOV interpolator anyway, and the opts_scatt%reg_limit_extrap option can be true or false (true recommended, and true is the default), but it is not related to the error message you are seeing.

Best wishes,
James

[Lanhui Sun]

Thank you very much for pointing out my issue. I will promptly correct the data and code. After your suggestion, I realized the problem was that the surface layer’s half pressure (ph) was larger than the 2-meter pressure. I deleted the last row of the data for “! p ph t q cc clw ciw rain snow” (i.e., the surface layer), and after that, it ran normally. May I ask if there are any issues with handling it this way? Thank you for your response!
! — Profile 80 —
!
! Vertical profiles:
!
! p ph t q cc clw ciw rain snow
! [hPa] [hPa] [K] [ppmv] [0-1] [kg/kg] [kg/kg] [kg/kg] [kg/kg]
0.104E+01 0.000E+00 0.263E+03 1.000E-06 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.113E+01 0.108E+01 0.257E+03 1.000E-06 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.122E+01 0.117E+01 0.254E+03 0.999E-06 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.132E+01 0.127E+01 0.252E+03 0.101E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.143E+01 0.137E+01 0.251E+03 0.102E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.155E+01 0.149E+01 0.252E+03 0.103E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.168E+01 0.161E+01 0.254E+03 0.103E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.181E+01 0.174E+01 0.255E+03 0.101E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.196E+01 0.189E+01 0.254E+03 0.972E-06 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.212E+01 0.204E+01 0.252E+03 0.902E-06 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.229E+01 0.221E+01 0.251E+03 0.825E-06 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.248E+01 0.239E+01 0.249E+03 0.834E-06 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.269E+01 0.258E+01 0.248E+03 0.110E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.291E+01 0.280E+01 0.247E+03 0.181E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.314E+01 0.303E+01 0.245E+03 0.302E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.340E+01 0.327E+01 0.244E+03 0.447E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.368E+01 0.354E+01 0.242E+03 0.580E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.398E+01 0.383E+01 0.241E+03 0.673E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.431E+01 0.415E+01 0.239E+03 0.720E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.466E+01 0.449E+01 0.238E+03 0.728E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.505E+01 0.486E+01 0.237E+03 0.702E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.546E+01 0.525E+01 0.235E+03 0.651E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.591E+01 0.568E+01 0.234E+03 0.588E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.639E+01 0.615E+01 0.233E+03 0.528E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.692E+01 0.666E+01 0.232E+03 0.474E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.749E+01 0.720E+01 0.231E+03 0.427E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.810E+01 0.779E+01 0.231E+03 0.383E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.876E+01 0.843E+01 0.230E+03 0.341E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.948E+01 0.912E+01 0.230E+03 0.297E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.103E+02 0.987E+01 0.229E+03 0.252E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.111E+02 0.107E+02 0.228E+03 0.208E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.120E+02 0.116E+02 0.227E+03 0.170E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.130E+02 0.125E+02 0.227E+03 0.144E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.141E+02 0.135E+02 0.225E+03 0.132E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.152E+02 0.146E+02 0.224E+03 0.132E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.165E+02 0.158E+02 0.223E+03 0.139E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.178E+02 0.171E+02 0.222E+03 0.148E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.193E+02 0.186E+02 0.221E+03 0.156E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.209E+02 0.201E+02 0.220E+03 0.165E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.226E+02 0.217E+02 0.218E+03 0.175E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.244E+02 0.235E+02 0.217E+03 0.178E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.264E+02 0.254E+02 0.215E+03 0.176E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.286E+02 0.275E+02 0.214E+03 0.172E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.310E+02 0.298E+02 0.213E+03 0.168E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.335E+02 0.322E+02 0.212E+03 0.164E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.362E+02 0.349E+02 0.212E+03 0.162E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.392E+02 0.377E+02 0.213E+03 0.160E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.424E+02 0.408E+02 0.213E+03 0.161E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.459E+02 0.442E+02 0.213E+03 0.158E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.497E+02 0.478E+02 0.213E+03 0.142E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.538E+02 0.517E+02 0.211E+03 0.122E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.582E+02 0.560E+02 0.210E+03 0.119E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.629E+02 0.606E+02 0.207E+03 0.146E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.681E+02 0.655E+02 0.204E+03 0.191E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.737E+02 0.709E+02 0.201E+03 0.235E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.797E+02 0.767E+02 0.199E+03 0.246E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.863E+02 0.830E+02 0.198E+03 0.277E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.934E+02 0.898E+02 0.195E+03 0.275E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.101E+03 0.972E+02 0.195E+03 0.308E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.627E-37
0.109E+03 0.105E+03 0.197E+03 0.341E-05 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.118E+03 0.114E+03 0.198E+03 0.511E-05 0.164E+00 0.000E+00 0.115E-06 0.000E+00 0.000E+00
0.128E+03 0.123E+03 0.199E+03 0.637E-05 0.365E+00 0.000E+00 0.414E-06 0.000E+00 0.157E-21
0.139E+03 0.133E+03 0.203E+03 0.102E-04 0.291E+00 0.000E+00 0.909E-06 0.000E+00 0.000E+00
0.150E+03 0.144E+03 0.207E+03 0.164E-04 0.143E+00 0.000E+00 0.108E-05 0.000E+00 0.165E-18
0.162E+03 0.156E+03 0.211E+03 0.267E-04 0.150E+00 0.000E+00 0.149E-05 0.000E+00 0.226E-21
0.176E+03 0.169E+03 0.215E+03 0.415E-04 0.254E+00 0.000E+00 0.342E-05 0.000E+00 0.413E-19
0.190E+03 0.183E+03 0.219E+03 0.582E-04 0.113E+00 0.000E+00 0.419E-05 0.000E+00 0.000E+00
0.205E+03 0.198E+03 0.223E+03 0.653E-04 0.000E+00 0.000E+00 0.673E-06 0.000E+00 0.000E+00
0.222E+03 0.214E+03 0.228E+03 0.795E-04 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.241E+03 0.231E+03 0.232E+03 0.116E-03 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.260E+03 0.250E+03 0.237E+03 0.129E-03 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.282E+03 0.271E+03 0.241E+03 0.355E-03 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.171E-37
0.305E+03 0.293E+03 0.246E+03 0.855E-03 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.330E+03 0.317E+03 0.251E+03 0.125E-02 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.357E+03 0.343E+03 0.254E+03 0.171E-02 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.782E-29
0.386E+03 0.372E+03 0.258E+03 0.225E-02 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.418E+03 0.402E+03 0.262E+03 0.280E-02 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.133E-37
0.453E+03 0.435E+03 0.266E+03 0.331E-02 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.490E+03 0.471E+03 0.270E+03 0.380E-02 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.530E+03 0.510E+03 0.274E+03 0.473E-02 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.573E+03 0.551E+03 0.277E+03 0.593E-02 0.130E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
0.615E+03 0.594E+03 0.279E+03 0.746E-02 0.245E+00 0.760E-14 0.000E+00 0.124E-06 0.000E+00
0.656E+03 0.636E+03 0.281E+03 0.864E-02 0.202E+00 0.000E+00 0.000E+00 0.599E-06 0.000E+00
0.696E+03 0.676E+03 0.284E+03 0.979E-02 0.230E+00 0.000E+00 0.000E+00 0.139E-05 0.000E+00
0.734E+03 0.715E+03 0.286E+03 0.109E-01 0.248E+00 0.000E+00 0.000E+00 0.214E-05 0.000E+00
0.770E+03 0.752E+03 0.287E+03 0.123E-01 0.259E+00 0.000E+00 0.000E+00 0.350E-05 0.000E+00
0.803E+03 0.786E+03 0.289E+03 0.131E-01 0.263E+00 0.000E+00 0.000E+00 0.501E-05 0.000E+00
0.833E+03 0.818E+03 0.290E+03 0.136E-01 0.263E+00 0.000E+00 0.000E+00 0.596E-05 0.000E+00
0.861E+03 0.847E+03 0.292E+03 0.142E-01 0.261E+00 0.000E+00 0.000E+00 0.624E-05 0.000E+00
0.885E+03 0.873E+03 0.293E+03 0.152E-01 0.258E+00 0.000E+00 0.000E+00 0.673E-05 0.000E+00
0.907E+03 0.896E+03 0.294E+03 0.168E-01 0.253E+00 0.000E+00 0.000E+00 0.804E-05 0.000E+00
0.926E+03 0.917E+03 0.295E+03 0.182E-01 0.464E+00 0.286E-04 0.000E+00 0.927E-05 0.000E+00
0.943E+03 0.934E+03 0.296E+03 0.193E-01 0.395E+00 0.237E-04 0.000E+00 0.968E-05 0.000E+00
0.957E+03 0.950E+03 0.297E+03 0.201E-01 0.000E+00 0.000E+00 0.000E+00 0.981E-05 0.000E+00
0.970E+03 0.964E+03 0.298E+03 0.204E-01 0.000E+00 0.000E+00 0.000E+00 0.950E-05 0.000E+00
0.980E+03 0.975E+03 0.299E+03 0.206E-01 0.000E+00 0.000E+00 0.000E+00 0.885E-05 0.000E+00
0.989E+03 0.985E+03 0.300E+03 0.207E-01 0.000E+00 0.000E+00 0.000E+00 0.802E-05 0.000E+00
0.997E+03 0.993E+03 0.301E+03 0.209E-01 0.000E+00 0.000E+00 0.000E+00 0.717E-05 0.000E+00
0.100E+04 0.100E+04 0.301E+03 0.211E-01 0.000E+00 0.000E+00 0.000E+00 0.639E-05 0.000E+00
!
! Near-surface variables:
! 2m T (K) 2m q (kg/kg) 2m p (hPa) 10m wind u (m/s) 10m wind v (m/s)
!
301.227 0.022 999.844 14.01512 -4.96728
!
! Skin variables:
! Skin T (K) Salinity FASTEM parameters for land surfaces
!
301.9148254394531 35.0 3.0 5.0 15.0 0.1 0.3
!
! Surface type (0=land, 1=sea, 2=sea-ice) and water type (0=fresh, 1=ocean)
!
1 1
!
! Elevation (km), latitude and longitude (degrees)
!
0.0 14.0 132.5
!
! Sat. zenith and azimuth angles(degrees)
!
5.161487102508545 83.22803497314453
!
! — End of profile 80 —

[James Hocking]

The disadvantage in simply removing that bottom layer is that you exclude some hydrometeors from the simulation.

The best thing to do probably depends on the source of the data. For example, another approach might be to set the bottom full pressure to 999.744 hPa (slightly smaller than the surface pressure), and then set the bottom half pressure level to be 999.844 hPa (the surface pressure). Then you would not have to omit that bottom layer. But whether this makes sense depends on the how the original profile data is representing the atmosphere.

Best wishes,
James

[Author]

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