Geostationary Cloud
Algorithm Testbed
(GEOCAT) Processing
Mike Pavolonis and Andy Heidinger (NOAA/NESDIS/STAR)
Corey Calvert and William Straka III (UW-CIMSS)
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Outline
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History/background
Description of Capabilities
Limitations
Future Plans
Availability
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History/Background
• GEOCAT was developed by the AWG Cloud Application
Team for testing prospective GOES-R cloud algorithms.
• Cloud algorithms require the use of many channels and
much ancillary data. GEOCAT is therefore capable of
running many non-cloud algorithms. In recognition of this,
other AWG teams are already utilizing GEOCAT for their
own development work (e.g. winds, land).
• We were directed by the AWG to incorporate all
compatible CIMSS algorithms into GEOCAT. This work is
just beginning.
• We are considering changing the C in GEOCAT from
Cloud to something more general (e.g. Community,
Comprehensive, etc…).
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GEOCAT Capabilities (1)
• GEOCAT’s Philosophy: Provide navigated and
calibrated geostationary imager radiances, ancillary data
(e.g. NWP, surface maps, etc…), and fast model
generated clear sky radiance data structures to product
producing subroutines (e.g. algorithms), and to provide a
common algorithm output structure, whose definition is
transparent to the algorithm developer.
• Major benefits of design: 1). Allows for multiple
algorithms for the same and/or different products to be
processed with a single invocation of the GEOCAT
executable. 2). Adding new algorithms is simple. 3). The
code is self-optimizing so that no unnecessary
calculations or IO are performed. 4). The user specifies
which of the available algorithms to run.
• Supported GEO platforms: GVAR (e.g. GOES 8-15
imagers), MSG (SEVIRI), and MTSAT.
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Algorithm developer fills out template which
passes information to algorithm interface
Channel
dependency
Ancillary
data directory
path
Pointer to
algorithm
procedure
Number of
data pointers
to allocate
Textual
algorithm
description
info.
GEOCAT
List of
pointer
names to
allocate
NWP and
RTM
dependency
Cloud mask
and cloud
phase
dependency
Output
indicator
flag
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GEOCAT Capabilities (2)
• Several generic utility functions are available
to algorithm developers such as, matrix
inversion, interpolation, atmospheric profile
utilities, spatial uniformity, etc…
• Instrument dependant Planck function is
available to the algorithm developer.
• GEOCAT allows data from previous or
“future” times to be easily loaded into memory
so that algorithms can take advantage of the
temporal resolution of geostationary data.
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Flexible Spatial Domain
Full Domain
Satellite Zenith
Defined Domain
Line/Element
Defined Domain
The spatial domain is
defined at run-time
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GEOCAT Conceptual Model
-Satellite Images
-Ancillary Data
GEOCAT
L1 (radiances)
L2 (pixel-level products)
RTM (clear radiances)
Calibrated/navigated radiances and
ancillary data are loaded into data
structures that can be accessed by
algorithms
Navigation
and
Calibration
Map ancillary
data to pixel
level
Execute
higher order
algorithms
Calculate
clear sky
radiances
(if needed)
Execute
lower order
algorithms
Output from high order algorithms
is
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available to lower level algorithms
Ancillary Data
Parameter: Global NWP
fields (e.g. temperature,
water vapor, ozone, etc…)
Source: GFS or GDAS
Native Spatial
Resolution: 0.5 or 1.0
degree
Time Resolution: 6-hours
Note: The vertical profile
variable are interpolated to
the standard 101 AIRS
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levels
Ancillary Data
Parameter: Surface
emissivity (for channels 7 16)
Source: Seeman and
Borbas (2006)
Native Spatial
Resolution: 5-km
Time Resolution: monthly
mean
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Ancillary Data
Parameter: Surface
elevation
Source: GTOPO-30
Native Spatial
Resolution: 8-km
Time Resolution: static
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Ancillary Data
Parameter: Surface land
type
Source: AVHRR-based
from UMD
Native Spatial
Resolution: 1-km
Time Resolution: static
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Ancillary Data
Parameter: Snow/ice
mask
Source: IMS - Northern
Hemisphere, SSMI Southern Hemisphere
Native Spatial
Resolution: 4-km
(Northern Hemisphere),
25-km (Southern
Hemisphere)
Time Resolution: daily
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Ancillary Data
Parameter: Coast mask
Source: NASA
Native Spatial
Resolution: 1-km
Time Resolution: static
Notes: Coast mask
indicates distance from
coast (1 - 10 km), as
sensitivity to coastline will
vary from application to
application
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Ancillary Data
Parameter: Volcano mask
Source: Smithsonian
Native Spatial
Resolution: 1-km
Time Resolution: static
Notes: These data indicate
how close a given satellite
pixel is to a volcano
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Ancillary Data
Parameter: Climatological
sea surface temperature
Source: OISST
Native Spatial
Resolution: 1-degree
Time Resolution: monthly
mean
Notes: Higher resolution
SST from 0.5 GFS is used
when available
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Infrared Radiative Transfer Model
For each channel in memory,
the following is available:
•Clear sky TOA radiances and
brightness temperatures
•Atmospheric transmittances
and radiance profiles at 101
levels
Currently, only PFAST (Woolf, CIMSS) is available in
GEOCAT. We plan on adding the CRTM once shortwave,
cloudy RTM, and trace gas updates have been made. 17
RTM Bias Analysis
M E T E O S A T -8 (O b s e rve d - C a lc u la te d )
1 9 A u g u s t 2 0 0 6 (W a te r)
RTM bias analysis shows
expected behavior (based
on prior experience),
which gives confidence
that the RTM/NWP fields
are implemented properly
in GEOCAT.
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Water
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TBD08
TBD10
TBD11
TBD14
TBD15
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TBD16
2
M E T E O S A T -8 (O b s e rve d - C a lc u la te d )
1 9 A u g u s t 2 0 0 6 (L a n d )
0
8
-2
0
2
4
6
8
10
12
14
T im e (U T C )
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TBD08
TBD10
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T e m p e ra tu re (K )
T e m p e ra tu re (K )
TBD12
TBD11
TBD12
TBD14
TBD15
4
TBD16
2
0
Land
-2
0
2
4
6
8
10
12
T im e (U T C )
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Example Usage
Command-line arguments are used to specify
run-time options.
./geocat -verbose -maxsatzen 70 -nscans 200 -use_seebor -use_snow \
-area_dir ./ -l1_dir ./ -l2_dir ./ -dumpch 2 5 14 \
-a 2 4 -f met08_disk_1_2006_015_1200.area.gz
L1
Output
L2
Output
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Known GEOCAT Limitations
• Limited built-in algorithm precedence
• No surface reflectance ancillary data
• No built-in shortwave radiative transfer
procedures
• CRTM is not yet installed in GEOCAT (we are
waiting for additional updates - e.g. SW RTM,
cloudy RTM, trace gases)
• GEOCAT does not produce Level 3 (e.g.
gridded) data
• Only tested with Intel Fortran 90 compiler
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Near-term Plan
• Our interpretation is that all compatible
CIMSS AWG algorithms will be delivered to
the AIT via GEOCAT.
• We are beginning to coordinate this effort with
the CIMSS PI’s.
• At this point, we do not know of any CIMSS
algorithms that are not compatible. This will
be confirmed when the funding kicks off.
• We are also beginning to develop GEOCAT
documentation.
• The AIT will determine GEOCAT’s role,
beyond delivering CIMSS algorithms.
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GEOCAT Availability
• Several groups at CIMSS and the Winds
AWG are using GEOCAT.
• We would prefer non-CIMSS usage to be
coordinated through the AIT.
• The version of GEOCAT used to implement
and deliver CIMSS algorithms will be
delivered to the AIT.
• AIT requirements on GEOCAT prior to the
delivery of CIMSS algorithms needs to be
determined.
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