4.4 Bogussing

  A procedure has been developped in order to try and improve the forecast of tropical cyclone in ARPEGEALADIN : it is called "bogussing", or "configuration 927E". This configuration is working in 3 steps :

     

1.

Bogussing of ALADIN : a configuration EE927 is run in adiabatic mode with translation activated to move the model cyclone (actually the minimum of surface pressure in the model) to the observed location (refer to NFPTTYP, FPMUCEN and FPLOCEN). In order not to translate the orography, one should first lower the orography to zero, then translate, and finally re-set the original orography.

2.

ARPEGE background : this is a file ARPEGE which should contain the fields of a given ARPEGE history file, all in gridpoint representation. Furthermore the surface pressure should be the true one, not its logarithm. This file aims to be used for the third step :

3.

Bogussing of ARPEGE : this configuration is a kind of "reverse configuration E927" : starting from the ARPEGE background file and the ALADIN bogussed file, a new ARPEGE file is build, containing the local translation of fields in the vicinity of the tropical cyclone.

To run this configuration 927E (aladin to arpege) you have to run the model ALADIN (setting LELAM=.TRUE. or -m aladin in command line) with the namelist of a configuration 927 in adiabatic mode and with the incremental process as described below :

   

NFPINCR

:

Definition

: Control of incremental post-processing. Set NFPINCR=1 to activate the incremental process.

Scope

: Integer which value can be only 0 or 1.

Default value

: 0

Namelist location

: NAMFPC

    You will have also to provide 3 input files :

ELSCF${CNMEXP(1:4)}ALBC

: the ALADIN file before bogussing

ICMSH${CNMEXP(1:4)}INIT

: the ALADIN bogussed file

BGPX${CNMEXP(1:4)}${CFPDOM}

: the ARPEGE background file

Remark : this "incremental" process can be considered like the "tangent linear post-processing of the poor", as it does not really works on incrents ...