A GEO-iSHAI model configuration file contains all the coefficients and some constant values required by GEO-iSHAI software to run. It has by default the extension “.cfm”. The model configuration file must be placed at the $SAFNWC/config directory.
Below are described all the keywords and the options allowed in the GEO-iSHAI configuration file. They have been grouped by meaning or functions. Also some considerations that the user must take into account to fix them for operational mode:
LSIZE_FOR and CSIZE_FOR: the default width of the FOR is 3. But the width of the FOR is configurable by the user. For example, changing the width of the FOR from 3x3 to 6x6, the process speed up in a factor of 4. The best resolution is obtained with 1x1 but the price could be the high execution time if the region is large.
MAX_ITERATIONS number. It establishes the number iterations for one pixel. The default maximum number of iterations is three. Taking into account that in each one of the physical retrieval iterations is one CPU expensive routine, the decreasing of MAX_ITERATIONS can reduce the execution time.
BT_RMS_THRESHOLD
and MAX_RESIDUAL
keywords. These keywords control the level of the desired error
between the satellite bias corrected BTs and the synthetic RTTOV
BTs.
Inside GEO-iSHAI is calculated BT_RMS that is the error between the satellite bias corrected BTs and RTTOV BTs (calculated from the profile after FG regression step) at the non window channel (i.e. WV6.2, WV7.3 and IR13.4 in SEVIRI case and WV6.2, WV6.9, WV7.3 and IR13.3 in AHI or ABI case). The physical retrieval module is executed only if BT_RMS is greater than BT_RMS_THRESHOLD.
The MAX_RESIDUAL keyword is the threshold used to stop the iteration process in the physical module. MAX_RESIDUAL is the allowed error between the satellite bias corrected BTs and the RTTOV BTs.
Then, if BT_RMS_THRESHOLD is fixed
too high, it speeds up the process because only the FG regression
step is applied to a high percent of the FOR. If it is fixed too
low, the maximum iteration number is applied to a high percent of
the FOR slowing the iSHAI execution (the most CPU expensive
routine is RTTOV_K and it is called inside the physical retrieval
module).
Note: if BT_RMS_THRESHOLD is fixed to a low value and if MAX_RESIDUAL is fixed to a very low value (example 0.0001) and the number of iterations is fixed to 3, the physical retrieval process will be executed always for every clear FOR and the execution time can increase enormously.
For an optimal election, the analysis
of the histogram the error between the biases corrected satellite
bias corrected BTs and the RTTOV BTs could be used.
ZENITH_THRESHOLD Only pixels with satellite zenith angle below or equal to ZENITH_THRESHOLD are processed. Although the FG regressions coefficients are available between [0, 75º] are only validated between [0º, 70º]. For this reason the default value is 70.
BAND_CLOUDY
Over cloudy pixels, one IR BT channel degraded to 7 bits (range [0
– 127]) value is stored as a field in the iSHAI netCDF output
file. This field could be later used to generate adequate images
in which cloudy pixels are grey scaled and clear pixels are colour
scaled. By default is configured the cleanest IR window channel in
each satellite:
a) If value is 1 then BT of the FOR is calculated using the mean of all clear pixels. This is the default value.
b) If value is 2 then BT of the FOR is filled with the BTs at the warmest clear pixel in the cleanest IR window channel (IR10.8 in SEVIRI case and IR10.4 in AHI or ABI case).
POST_PROC_METHOD This keyword controls the way that the clear pixels filling inside the FOR is made.
The default
value is 1. The default method is to copy the same value to
all clear pixels in the FOR.
The other option (value 0) is to write the output only at the
clear pixel position. This means at the warmest clear pixel in the
cleanest IR window channel (IR10.8 in SEVIRI case and IR10.4 in
AHI or ABI cases) in case FOR_METHOD
is 2 or the centre in FOR_METHOD
is 1.
SAVE_PROFs_in_BINARY_files and SAVE_iSHAI_in_BINARY_file These keywords control the activation of the optional writing of the GEO-iSHAI binary files. See optional binary files description.
TOZ_CALCULATION This keyword makes the activation of calculation of TOZ if fixed to 1. The default value 0 means that no TOZ calculation is made. If activated, that implies background NWP GRIB file must have ozone data at same levels that T and humidity profiles.
The name of all
coefficients files are keywords in the configuration files. Thus,
to change a coefficient file it is only needed to change the name
of the coefficient file in the model configuration file.
The list of the configurable coefficients files in the case of MSG satellites is in the table below:
Default
configurable coefficients files for MSG satellites
in version 2021 |
|
keyword |
Default name
of FG non-linear regression coefficients files |
FG_reg_T_filename |
FG_reg_T_GEO_iSHAI_v2021_rttov11_msg_date_sep2021.bin |
FG_reg_logq_filename |
FG_reg_logq_GEO_iSHAI_v2021_rttov11_msg_date_sep2021.bin |
FG_reg_logOzone_filename |
FG_reg_logOzone_GEO_iSHAI_v2021_rttov11_msg_date_sep2021.bin |
FG_reg_SKT_filename |
FG_reg_SKT_GEO_iSHAI_v2021_rttov11_msg_date_sep2021.bin |
EOF_FILENAME |
EOF_iSHAI_v2018_date_sep2018.bin |
Binverse_covariance_matrix_filename |
Binv_iSHAI_v2018_date_sep2018.bin |
Einverse_covariance_matrix_filename |
Einv_iSHAI_v2018_msg_date_sep2018.bin |
Default
configurable coefficients files for Himawari
satellites in version 2021 |
|
keyword |
Default name
of FG non-linear regression coefficients files |
FG_reg_T_filename |
FG_reg_T_GEO_iSHAI_v2018_rttov11_AHI_date_sep2018.bin |
FG_reg_logq_filename |
FG_reg_logq_GEO_iSHAI_v2018_rttov11_AHI_date_sep2018.bin |
FG_reg_logOzone_filename |
FG_reg_logOzone_GEO_iSHAI_v2018_rttov11_AHI_date_sep2018.bin |
FG_reg_SKT_filename |
FG_reg_SKT_GEO_iSHAI_v2018_rttov11_AHI_date_sep2018.bin |
EOF_FILENAME |
EOF_iSHAI_v2018_date_sep2018.bin |
Binverse_covariance_matrix_filename |
Binv_iSHAI_v2018_date_sep2018.bin |
Einverse_covariance_matrix_filename |
Einv_iSHAI_v2018_AHI_date_sep2018.bin |
The list of the configurable coefficients files in the case of
GOES-R satellites is in the table below:
Default
configurable coefficients files for GOES-R class
satellites version 2021 |
|
keyword |
Default name
of FG non-linear regression coefficients files |
FG_reg_T_filename |
FG_reg_T_GEO_iSHAI_v2018_rttov11_ABI_date_jul2019.bin |
FG_reg_logq_filename |
FG_reg_logq_GEO_iSHAI_v2018_rttov11_ABI_date_jul2019.bin |
FG_reg_logOzone_filename |
FG_reg_logOzone_GEO_iSHAI_v2018_rttov11_ABI_date_jul2019.bin |
FG_reg_SKT_filename |
FG_reg_SKT_GEO_iSHAI_v2018_rttov11_ABI_date_jul2019.bin |
EOF_FILENAME |
EOF_iSHAI_v2018_date_sep2018.bin |
Binverse_covariance_matrix_filename |
Binv_iSHAI_v2018_date_sep2018.bin |
Einverse_covariance_matrix_filename |
Einv_iSHAI_v2018_AHI_date_sep2018.bin |
NWP_EXEC_MODE The selection of the type vertical representation of GRIB files used as background NWP and then parameters, vertical levels and spatial interpolation is fixed by this keyword. The options are:
(P) GRIBs at fixed pressure levels
(HYB) GRIB at hybrid levels.
The default is P mode but better results are obtained with HYB mode.
Keywords for establishing the parameters to be remapped and the generation of specific humidity profile when the AllMappingNWP tool is executed. These keywords are only needed in the case of using as background NWP fixed pressure levels GRIB files. These keywords are:
NWP_PARAM NWP_T 1 BLI
NWP_PARAM NWP_Q 1 BLI
NWP_PARAM NWP_OZ 1 BLI
NWP_PARAM NWP_SP 1 BLI
NWP_PARAM NWP_ST 1 BLI
NWP_PARAM NWP_SGEOP 1 BLI
NWP_PARAM NWP_2T 1 BLI
NWP_PARAM NWP_2Q 1 BLI
Keywords for establishing the grids to be read by GEO-iSHAI when executed in HYB mode. These keywords are only needed in the case to use as background NWP hybrid levels GRIB files. These keywords in the case of ECMWF are:
NWP-HYB_T t 130
NWP-HYB_Q q 133
NWP-HYB_OZ o3 203
NWP-HYB_ST skt 235
NWP-HYB_SP sp 152
NWP-HYB_GEOP z 129
As summary, the user must establish a compromise between the computer resources (CPU speed and memory) where the NWC/GEO package will be operated, the region (or regions) to process and the configurable keywords (number of iterations, BT_RMS_THRESHOLD and MAX_RESIDUAL keywords and width of the FOR) in the GEO-iSHAI model configuration.