some problems of spherical harmonic filter

From: Song Feng (songfeng AT XXXXXX)
Date: Mon Feb 18 2002 - 17:38:51 MST

  • Next message: Dennis Shea: "Re: some problems of spherical harmonic filter"

    Hi everyone

    I am trying to use some of the NCL functions for spatial smoothing of global data. The data I used have 6 variables and all variables have the same structure and same dimensions. I noticed that my code work reasonable well for 4 variables. For the other two variables (dudt, divk) the results are also good except for 925-700hPa levels. I check the original data of "dudt" and "divk" and found no strange values for the 925-700 levels. I wonder if you can help me to figure out why my results are wrong for those 3 levels and good for other levels. The following is the code I used:

     a = new ( (/054,17,73,073 /), float)
     b = new ( (/054,17,73,073 /), float)
      T = 16
      shaec(dudt,a,b) ; for 925-700hPa level, The values of "dudt" are around 10^ -5 or 10^ -6
      tri_trunc (a,b,T)
      exp_tapersh (a,b, 10, 2)
       dudtt= dudt
       shsec(a,b,dudtt)
    ; ***** "dudtt" is the output after spherical harmonic filter. For 925-700hPa levels, the values of "dudtt" are around 10^0 or 10^2.
    ; ***** for other levels, the outputted "dudtt" matched the original "dudt" very well.
      printVarSummary (dudtt)
      printVarSummary (dudt)
      delete (a)
      delete (b)

    Song Feng



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