Three main steps are identified. The user manually interacts with the NWC/GEO software package during the installation and preparation step, and the GEO-iSHAI execution step is automatically monitored by the Task Manager (if real time environment is selected).
The right to use, copy or modify this software is in accordance with EUMETSAT Policy for the NWC/GEO software package.
Once the user has obtained the necessary permissions to download the software package, the software installation procedure does not require special resources. It is restricted to decompress the distribution file (a gzip-compressed tar file) and to successfully build the executable GEO-iSHAI-v401 file to be stored into the $SAFNWC/bin directory.
After the steps shown in the “System Version Document for the NWC/GEO” (code NWC/CDOP2/AEMET/SW/SCVD), GEO-iSHAI-v401 of the NWC/GEO is installed and configured in the system. The operational use of NWC/GEO requires the definition of some configuration files in order to select the regions to be processed and some configuration parameters of the corresponding configuration file.
A set of default GEO-iSHAI model configuration file (extension *.cfm) is provided with the software package. There are default GEO-iSHAI model configuration file for any NWC/GEO supported satellite and for P and HYB modes. As all configuration files, it is an ASCII file, so further modification can be easily performed with a text editor. The configuration file manages all processes in the executable file.
The automatic set of pre-defined time scheduling (of the preparation step) relies on Programmed Task Definition Files.
An output CMA netCDF file for the same slot and region is mandatory as input to GEO-iSHAI and for this reason it GEO-CMA-v51 has to be executed before GEO-iSHAI-v401 execution.
Also NWP spatial preprocessing should be done by the Task Manager or with the AllMappingNWP tool if the GEO-iSHAI is executed in P mode.
If GEO-iSHAI is executed in HYB mode (configurable in the iSHAI configuration file using the keyword NWP_EXEC_MODE fixed to HYB) the NWP spatial preprocessing is needed only for GEO-CMA generation but it is not needed for GEO-iSHAI. In HYB mode, GEO-iSHAI opens and manages directly the hybrid GRIB files.
The execution step is the real-time processing of SEVIRI images over one region with real SEVIRI images. This process consists of the launch of the command GEO-iSHAI-v401 along with the required parameters (slot, region file name and model configuration file).
It could be done interactively by the user or automatically in near real time by the Task manager. The execution of GEO-iSHAI cannot be till GEO-CMA-v51 has finished for the same slot and region. The GEO-iSHAI-v401 is then performed following the corresponding configuration file. The use of the GEO-iSHAI-v401 command is very easy on scripts. Here, an example of execution is provided:
GEO-iSHAI-v401 YYYY-MM-DDThh:mm:00Z region.cfg configuration_file.cfm
Where:
YYYY-MM-DDThh:mm:00Z is the date (YYYY-MM-DD) and hour (hh:mm:00Z) of the GEO satellite image
region.cfg is the name of file with region to use
configuration_file.cfm is the name of the ASCII file with the configurable parameter that GEO-iSHAI needs.
GEO-iSHAI has been designed as modular and configurable by the user as possible. In order to configure it, the configurable options are collected in the GEO-iSHAI configuration file. GEO-iSHAI model configuration file allows an easy management of all GEO-iSHAI keywords that can be changed by the user. Each model configuration file is an ASCII file, so further modifications can be easily performed with a text editor.
The GEO-iSHAI running time scheduling relies on the Programmed Task Definition File. This process consists in running GEO-iSHAI-v401 command along with the required parameters (slot, region file and model configuration file) by the Task Manager.
Since the model configuration file is the third argument required by the GEO-iSHAI program, to change the configuration used to execute the GEO-iSHAI code is as easy as to change the third argument when the GEO-iSHAI is executed or edit it. Thus, several GEO-iSHAI configuration files can be available by the user in the $SAFNWC/config and GEO-iSHAI can be executed on real time with different configuration depending on the region to process, the hour of the image, etc. As an example, users can execute GEO-iSHAI with a large FOR’s width in a global or large region with only one iteration and execute GEO-iSHAI over a small region centred in their countries with FOR’s width 3x3 and three iterations.
When setting up the execution conditions, users must look for a balance among the region size, the computer resources and the following configurable keywords of the configuration file: BT_RMS_THRESHOLD, LSIZE_FOR, CSIZE_FOR and MAX_ITERATIONS.
Also this mechanism allows to change the GEO-iSHAI execution mode (P or HYB) editing or using different configuration file changing the NWP_EXEC_MODE keyword.