OSSE Nature Run Data Set

Forecast date:                00Z 5 February 1993
Frequency of Archive:         6 hour
Period:                       06Z 5 Feb93 -00Z  7 Mar 93
                              Starts from 6 hour forecast to 720 hour forecast
                              Total 120 periods
Resolution:                   T213 spectral and N160(reduced Gaussian)
                                   (about 60Km)
                              31 levels

Content of the Nature run data set
List of the variables 
Reduced Gaussian grid  N160
     Surface fields, Cloud liquid water content,  Cloud cover 
     
T213 spectral
     Log surface pressure,   T U V Q W

Simulated observation in BUFR format  (FM 94 - X Ext. BUFR)
     SYNOP, ASCAT,   TOVS,  ATOVS,  DWL


[Reduced Gaussian Grid]

Reduced Gaussian grid  N160
     Number of latitudes between equator to pole: 160
    Number of longitudes varies from 12 to 640

Full Gaussian  G160
     Number of longitudes  is fixed at  640
     

     Both N160 and T213 data are expanded to G160.
     Linear interpolation from N160  to G160
     Grid points for N160 are a subset of G160
     Original values are saved on N160 grids.
     Note that only values on N160 are used by the model.


Number of longitudes : 

N160 grids alway include GM (0E)




[Vertical levels]
     31 half levels
     Keep ECMWF model levels.  

     Level 1  is the top level
     Level 31 is the lowest level

     Pressure at half level  k  (Pk)

     Pk=(pk + pk+1)/2      (Pascals)

     pk = Ak + Bk x exp(lnsp) 

     A and B are given at 32 full levels  (pk)
     p32 = surface pressure,    p1 = 0
     

Get As and Bs                      

Radiation
          Archived Radiation cx(t):
                Accumulation  from forecast time 0  to t
                    unit:        Jm-2

          x(t)=(cx(t+6)-cx(t-6))/(12*3600)
          
          x: radiation averaged between t-6 to t+6
               unit Wm-2
          
          cx(720)/(720*3600):  30 days mean radiation
          

[Documentation]



A_B.dat:                 As and Bs
OBS.varlist:             Content of simulated observation   
TOVS9302.doc:            List of tapes for  observed TOVS
ec_obs.doc:              Documentation on tapes 
                              for simulated observation     
ecctape.doc:             Documentation on tapes model data
ecmwf_table_128:         ECMWF grib table for printing
g160data.970304:         Memo sent on 3/4/97
                         About G160 data, vertical coordinates, wgrib etc. gausslat.f:              
                         Subroutine to compute Gaussian latitudes
G160.ctl                 grads contoll file for G160 data
 	                 This explain the structure and contents of the data
local_table_2_version_128:
                         ECMWF grib table, computer readable format
red.nglon.N160.dat:      Number of longitudes for N160
userlist:                List of interested people
README.ossedoc           This list