[gradsusr] WRF data in grads: Problem with the levels

Thu Sep 15 04:38:54 EDT 2011

Hello,

I am using WRF data files in GrADS version 2.0.a9oga, in windows.  

Having been unable to open the WRF files using xdfopen or sdfopen I have
written my own CTL file in order to open the data. Everything is working for
me except that the z levels which the file contains do not seem to
correspond to the pressure. The nc dump suggests there are 29 levels (which
is correct as there were 29 eta levels in the WRF file).  

However the range of

these levels is from 2986950,2887400,2787850 ... up to  199550, 100000. How
can these numbers be related to pressure?

All I need to know is what these Z levels mean and how I can wither convert
them to pressure or to height. Thanks for any help offered.

The Corresponding CTL file is:

dset ^wrfout_d02_%y4-%m2-%d2_%h2_%n2_00

dtype netcdf

title "Iberdrola data for Jan2008"

undef -1e+30

options template

pdef 140 140 lcc 33.87970 -11.30862777011 1 1 43.427 43.427 -3.839993 10000
10000 xdef 140 linear -4.5000000 0.004 ydef 140 linear 41.950000 0.0032 zdef
30 linear 2986950 2887400,
2787850,2688300,2588750,2489200,2389650,2290100,2190550,2091000,1991450,1891
800,1792300,1692800,1593250,1493700,1394150,1294600,1195050,1095500,995950,8
96400,

796850,697300,597750,498200,398650,299100,199550,100000

tdef 480 linear 00:00Z01jan2008 1hr

vars 4

U=>u          29  t,z,y,x westerly wind

V=>v          29  t,z,y,x southerly wind

P=>p          29  t,z,y,x  Pressure

T=>t          29  t,z,y,x  perturbation potential temperature (theta-t0)

Endvars

the ncdump is:

netcdf wrfout_d02_2007-12-31_18_00_00 {

dimensions:

         Time = UNLIMITED ; // (1 currently)

         DateStrLen = 19 ;

         west_east = 140 ;

         south_north = 140 ;

         bottom_top = 29 ;

         bottom_top_stag = 30 ;

         soil_layers_stag = 4 ;

         west_east_stag = 141 ;

         force_layers = 8 ;

         south_north_stag = 141 ;

variables:

         char Times(Time, DateStrLen) ;

         float LU_INDEX(Time, south_north, west_east) ;

                 LU_INDEX:FieldType = 104 ;

                 LU_INDEX:MemoryOrder = "XY " ;

                 LU_INDEX:description = "LAND USE CATEGORY" ;

                 LU_INDEX:units = "" ;

                 LU_INDEX:stagger = "" ;

                 LU_INDEX:coordinates = "XLONG XLAT" ;

         float ZNU(Time, bottom_top) ;

                 ZNU:FieldType = 104 ;

                 ZNU:MemoryOrder = "Z  " ;

                 ZNU:description = "eta values on half (mass) levels" ;

                 ZNU:units = "" ;

                 ZNU:stagger = "" ;

         float ZNW(Time, bottom_top_stag) ;

                 ZNW:FieldType = 104 ;

                 ZNW:MemoryOrder = "Z  " ;

                 ZNW:description = "eta values on full (w) levels" ;

                 ZNW:units = "" ;

                 ZNW:stagger = "Z" ;     (... and many more variables
listed)

// global attributes:

                 :TITLE = " OUTPUT FROM WRF V3.1.1 MODEL" ;

                 :START_DATE = "2007-12-31_18:00:00" ;

                 :SIMULATION_START_DATE = "2007-12-31_18:00:00" ;

                 :WEST-EAST_GRID_DIMENSION = 141 ;

                 :SOUTH-NORTH_GRID_DIMENSION = 141 ;

                 :BOTTOM-TOP_GRID_DIMENSION = 30 ;

                 :DX = 10000.f ;

                 :DY = 10000.f ;

                 :GRIDTYPE = "C" ;

                 :DIFF_OPT = 1 ;

                 :KM_OPT = 4 ;

                 :DAMP_OPT = 0 ;

                 :DAMPCOEF = 0.2f ;

                 :KHDIF = 0.f ;

                 :KVDIF = 0.f ;

                 :MP_PHYSICS = 6 ;

                 :RA_LW_PHYSICS = 1 ;

                 :RA_SW_PHYSICS = 1 ;

                 :SF_SFCLAY_PHYSICS = 2 ;

                 :SF_SURFACE_PHYSICS = 2 ;

                 :BL_PBL_PHYSICS = 2 ;

                 :CU_PHYSICS = 0 ;

                 :SURFACE_INPUT_SOURCE = 1 ;

                 :SST_UPDATE = 0 ;

                 :GRID_FDDA = 0 ;

                 :GFDDA_INTERVAL_M = 0 ;

                 :GFDDA_END_H = 0 ;

                 :GRID_SFDDA = 0 ;

                 :SGFDDA_INTERVAL_M = 0 ;

                 :SGFDDA_END_H = 0 ;

                 :SF_URBAN_PHYSICS = 0 ;

                 :FEEDBACK = 1 ;

                 :SMOOTH_OPTION = 0 ;

                 :SWRAD_SCAT = 1.f ;

                 :W_DAMPING = 0 ;

                 :MOIST_ADV_OPT = 1 ;

                 :SCALAR_ADV_OPT = 1 ;

                 :TKE_ADV_OPT = 1 ;

                 :DIFF_6TH_OPT = 0 ;

                 :DIFF_6TH_FACTOR = 0.12f ;

                 :OBS_NUDGE_OPT = 0 ;

                 :WEST-EAST_PATCH_START_UNSTAG = 1 ;

                 :WEST-EAST_PATCH_END_UNSTAG = 140 ;

                 :WEST-EAST_PATCH_START_STAG = 1 ;

                 :WEST-EAST_PATCH_END_STAG = 141 ;

                 :SOUTH-NORTH_PATCH_START_UNSTAG = 1 ;

                 :SOUTH-NORTH_PATCH_END_UNSTAG = 140 ;

                 :SOUTH-NORTH_PATCH_START_STAG = 1 ;

                 :SOUTH-NORTH_PATCH_END_STAG = 141 ;

                 :BOTTOM-TOP_PATCH_START_UNSTAG = 1 ;

                 :BOTTOM-TOP_PATCH_END_UNSTAG = 29 ;

                 :BOTTOM-TOP_PATCH_START_STAG = 1 ;

                 :BOTTOM-TOP_PATCH_END_STAG = 30 ;

                 :GRID_ID = 2 ;

                 :PARENT_ID = 1 ;

                 :I_PARENT_START = 14 ;

                 :J_PARENT_START = 10 ;

                 :PARENT_GRID_RATIO = 5 ;

                 :DT = 60.f ;

                 :CEN_LAT = 40.5046f ;

                 :CEN_LON = -3.839993f ;

                 :TRUELAT1 = 43.427f ;

                 :TRUELAT2 = 43.427f ;

                 :MOAD_CEN_LAT = 43.427f ;

                 :STAND_LON = -3.84f ;

                 :POLE_LAT = 90.f ;

                 :POLE_LON = 0.f ;

                 :GMT = 18.f ;

                 :JULYR = 2007 ;

                 :JULDAY = 365 ;

                 :MAP_PROJ = 1 ;

                 :MMINLU = "" ;

                 :NUM_LAND_CAT = 24 ;

                 :ISWATER = 16 ;

                 :ISLAKE = 0 ;

                 :ISICE = 0 ;

                 :ISURBAN = 0 ;

                 :ISOILWATER = 0 ;

}

Catherine Meissner
Software Development Manager

    Fjordgaten 15 
    N-3125 Tønsberg, Norway

    Switchboard +47 33 38 18 00

     <http://www.windsim.com/> www.windsim.com 

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