NWPSAF Met Office 1D-Var User Manual

Andrew Collard, Met Office, Bracknell, UK

NWPSAF-MO-UD-006

Version 2.3: 10^th June 2002
Version 3.1: 23^rd March 2004

This software and documentation was developed within the context of the EUMETSAT satellite Application Facility (NWP SAF). The partners in the NWP SAF are the Met Office, ECMWF, KNMI, and Météo-France.

Appendix D. Adding a New Radiative Transfer Model

The following provides an outline of the steps and code you need to modify to include a new fastmodel in the 1DVar code.

1. IASIMod_RTModel add model to fastmodel identities.

2. IASIMod_Constants add model regression limits (on 1DVar pressure levels, in the units of the retrieval state vector).

3. IASI_Read_ControlData add new fastmodel to cases for RTModelToUse.

4. IASI_Fastmodel_Interface add option to call new fastmodel.

5. IASI_ModelName_Interface code the calling interface and the dummy interface for the new fastmodel. Follow existing fastmodel interfaces as an example.

Note the units of the retrieval state vector variables stored in RTParams % RTBack and RTParams % RTGuess:

Temperature	degrees Kelvin
Humidity	natural logarithm of the mass mixing ratio (kg/kg)
Ozone	volume mixing ratio in ppmv with respect to dry air
Surface pressure	hectopascal

Retrieval pressure levels (in Pascal) are defined in RT_Params % Pressure_Pa.

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1.	`IASIMod_RTModel`	add model to fastmodel identities.
2.	`IASIMod_Constants`	add model regression limits (on 1DVar pressure levels, in the units of the retrieval state vector).
3.	`IASI_Read_ControlData`	add new fastmodel to cases for RTModelToUse.
4.	`IASI_Fastmodel_Interface`	add option to call new fastmodel.
5.	`IASI_ModelName_Interface`	code the calling interface and the dummy interface for the new fastmodel. Follow existing fastmodel interfaces as an example.