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Geostationary Cloud Algorithm Testbed

(GEOCAT) ProcessingMike Pavolonis and Andy Heidinger (NOAA/NESDIS/STAR)

Corey Calvert and William Straka III (UW-CIMSS)

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Outline

• 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

NWP and RTM

dependency

Cloud mask and cloud

phase dependency

Output indicator

flag

List of pointer

names to allocate

Textual algorithm

description info.

Number of data pointers to allocate

Pointer to algorithm procedure

GEOCAT

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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 DomainFull 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

GEOCATNavigation

andCalibration

Map ancillarydata to pixel

level

Calculateclear skyradiances(if needed)

Executelower orderalgorithms

Executehigher orderalgorithms

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

Output from high order algorithms is available to lower level algorithms

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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 levels

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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 ModelFor 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.

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RTM Bias AnalysisRTM bias analysis shows expected behavior (based on prior experience), which gives confidence that the RTM/NWP fields are implemented properly in GEOCAT.

METEOSAT-8 (Observed - Calculated)19 August 2006 (Water)

-2

0

2

4

6

8

0 2 4 6 8 10 12 14 16 18 20 22Time (UTC)

Temperature (K)

TBD08

TBD10

TBD11

TBD12

TBD14

TBD15

TBD16

Water

METEOSAT-8 (Observed - Calculated)19 August 2006 (Land)

-2

0

2

4

6

8

0 2 4 6 8 10 12 14 16 18 20 22Time (UTC)

Temperature (K)

TBD08

TBD10

TBD11

TBD12

TBD14

TBD15

TBD16

Land

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Example Usage

./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

Command-line arguments are used to specify run-time options.

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.