SUMMARY
OF
CHANGES OF iSHAI VERSION 2018.1 WITH RESPECT TO PREVIOUS
VERSION iSHAI VERSION 2016
GEO-iSHAI algorithm remains based in Jun Li’s algorithm for GOES
Sounder physical retrieval algorithm (physical iterative approach
with non-linear regression as first guess) but adapted for RTTOV and
other GEO imager instruments. Jun Li (CIMSS-Wisconsin) algorithm is
also the one proposed as Day-1 algorithm for the GOES-R processing
by NOAA (Li, 2010).
GEO-iSHAI release 2018.1 has some major updates due to the
introduction of the support of other GEO satellites than SEVIRI. In
version 2018.1 Himawari and GOES-R class satellites are also
supported.
The use of RTTOV-11.2 in version 2018.1 implies that the number of
RTTOV pressure levels remains in 54 RTTOV pressure levels. For this
reason all the coefficients has been calculated using the GEO-iSHAI
validation dataset for 2017 year with vertical dimensions adjusted
to the used RTTOV pressure levels.
In previous versions there were separated EOFs coefficients files
for temperature and humidity that after reading where combined to
build the full EOF matrix. In version 2018.1, the full EOFs matrix
is read from a single coefficient file.
The GEO-iSHAI code version 2018.1 has been also adapted to ABI
instrument on board GOES-R satellites with minor changes in the code
and the generation of a set of iSHAI coefficients for GOES-R. In
version 2018 Himawari and MSG satellites were supported.
GEO-iSHAI Total Ozone (TOZ) output was introduced as a new output in
release 2016. TOZ is calculated from the ozone profile after
applying only the non-linear regression step. In version 2016 in the
ozone non-linear regressions, the collocated real bias corrected
satellite BTs and the temperature profile, the logarithm of ozone
profile and the skin temperature from background NWP profile were
used as inputs. Thus, neither the physical retrieval step nor the
iSHAI retrieved profile (result of FG or physical retrieval step
depending on BT_RMS_THREHOLD keyword) were not used in the ozone
profile estimation. In version 2018.1; this has been changed and in
the ozone non-linear regressions, the collocated real bias corrected
satellite BTs and the temperature profile, the logarithm of specific
humidity profile and the skin temperature from the iSHAI retrieved
profile and the logarithm of ozone profile from the background NWP
profile are used as inputs.
A summary of the changes of iSHAI version 2016 with respect to
previous version former PGE13 SPhR version 2013 is available here.