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Climate Data Record (CDR) Program

Climate Algorithm Theoretical Basis Document (C-ATBD)

AVHRR Polar Pathfinder (APP)

CDR Program Document Number: CDRP-ATBD-0572 Configuration Item Number: 01B-24a Revision 1.0 / September 16, 2015

CDR Program AVHRR Polar Pathfinder (APP) C-ATBD CDRP-ATBD-0572 Rev. 1.0 09/16/2015

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REVISION HISTORY

Rev. Author DSR No. Description Date

1 Yinghui Liu, CIMSS UW-Madison; Jeff Key, NOAA; Andrew Heidinger, NOAA

DSR-734 Initial baseline submission to the CDR Program Library

09/16/2015

CDR Program AVHRR Polar Pathfinder (APP) C-ATBD CDRP-ATBD-0572 Rev. 1.0 09/16/2015

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TABLE of CONTENTS

1. INTRODUCTION .............................................................................................................................. 8 1.1 Purpose ..................................................................................................................................................... 8 1.2 Definitions................................................................................................................................................. 8 1.3 Document Maintenance ............................................................................................................................ 9

2. OBSERVING SYSTEMS OVERVIEW ............................................................................................ 9 2.1 Products Generated .................................................................................................................................. 9 2.2 Instrument Characteristics ...................................................................................................................... 10

3. ALGORITHM DESCRIPTION ...................................................................................................... 13 3.1 Algorithm Overview ................................................................................................................................ 13 3.2 Processing Outline................................................................................................................................... 14

3.2.1 Data Ingest ............................................................................................................................................. 15 3.2.2 Calibration.............................................................................................................................................. 15 3.2.3 Navigation .............................................................................................................................................. 15 3.2.4 Compositing .......................................................................................................................................... 15

3.3 Algorithm Input ....................................................................................................................................... 16 3.3.1 Primary Sensor Data .............................................................................................................................. 16 3.3.2 Ancillary Data ......................................................................................................................................... 16 3.3.3 Derived Data .......................................................................................................................................... 17 3.3.4 Forward Models ..................................................................................................................................... 17

3.4 Theoretical Description ........................................................................................................................... 17 3.4.1 Physical and Mathematical Description ................................................................................................. 18 3.4.2 Data Merging Strategy ........................................................................................................................... 20 3.4.3 Numerical Strategy ................................................................................................................................ 20 3.4.4 Calculations ............................................................................................................................................ 20 3.4.5 Look-Up Table Description ..................................................................................................................... 21 3.4.6 Parameterization ................................................................................................................................... 21 3.4.7 Algorithm Output ................................................................................................................................... 21

4. TEST DATASETS AND OUTPUTS ............................................................................................. 22 4.1 Test Input Datasets ................................................................................................................................. 22 4.2 Test Output Analysis ............................................................................................................................... 22

4.2.1 Reproducibility ....................................................................................................................................... 22 4.2.2 Precision and Accuracy .......................................................................................................................... 24 4.2.3 Error Budget ........................................................................................................................................... 25

5. PRACTICAL CONSIDERATIONS ................................................................................................ 26 5.1 Numerical Computation Considerations .................................................................................................. 26 5.2 Programming and Procedural Considerations ......................................................................................... 26 5.3 Quality Assessment and Diagnostics ....................................................................................................... 26 5.4 Exception Handling ................................................................................................................................. 26

CDR Program AVHRR Polar Pathfinder (APP) C-ATBD CDRP-ATBD-0572 Rev. 1.0 09/16/2015

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5.5 Algorithm Validation ............................................................................................................................... 26 5.6 Processing Environment and Resources .................................................................................................. 26

6. ASSUMPTIONS AND LIMITATIONS ........................................................................................ 26 6.1 Algorithm Performance ........................................................................................................................... 26 6.2 Sensor Performance ................................................................................................................................ 33

7. FUTURE ENHANCEMENTS......................................................................................................... 33 7.1 Enhancement 1 ....................................................................................................................................... 33

8. REFERENCES .................................................................................................................................. 34

APPENDIX A. ACRONYMS AND ABBREVIATIONS ................................................................... 36

CDR Program AVHRR Polar Pathfinder (APP) C-ATBD CDRP-ATBD-0572 Rev. 1.0 09/16/2015

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LIST of FIGURES

Figure 1: Equatorial crossing time of NOAA POES. (Figure is from www.star.nesdis.noaa.gov/smcd/emb/vci/VH/vh_avhrr_ect.php. The original ECT data are from www.ospo.noaa.gov/Products/ppp/navpage.html.) .................................................................................. 13

Figure 2: Flow chart of processing steps to generate APP from AVHRR GAC level 1b data for a single target time. ................................................................................................................................................. 14

Figure 3: APP channel 1 reflectance (%) at 1400 LST of north pole on July 1 of the year 1982, 1986, 1989, 1996, 2002, and 2007. ................................................................................................................................ 23

Figure 4: APP channel 4 BT (K) at 1400 LST of south pole on January 1 of the year 1982, 1986, 1989, 1996, 2002, and 2007. ................................................................................................................................ 23

Figure 5: Channel 1 reflectance (%) and channel 4 BT (K) at 1400 LST of north pole on July 1 of the year 2007 from APP (upper row) and MODIS Aqua (lower row). ....................................................................... 25

Figure 6: Time series daily AVHRR channel 4 brightness temperatures from January 1, 1982 to August 23, 2006 at Barrow, Alaska for 1400 local solar time. Note: there are no data available from September 14, 1994 to January 18, 1995. .....................................................