NOAA-18 Instrument Calibration and Validation Briefing

1. NOAA-18 Instrument Calibration and Validation Briefing NOAA/NESDIS/Office of Research and Applications As of Week of June 13-17, 2005 For archived activities and latest news, please visit http://www.orbit.nesdis.noaa.gov/smcd/spb/n18calval

2. Weekly Highlights (June 13 - 17) • AVHRR • AVHRR on-orbit verification of calibration results (Sullivan) • A few minor revisions in geolocation pixel offsets (Sullivan) • Vicarious calibration results (Wu and Sullivan) • HIRS • Correct HIRS geolocation confirmed by Chalfant • HIRS noise analysis and a few telecon with NASA, OSD and ITT (Cao, Reale ) • A website developed for displaying HIRS calibration trending (Cao) • Intercomparison with NOAA-16 (Reale) • AMSU-A • Characterization of instrument asymmetry and angular dependent biases (Weng) • On orbit AMSU NEDT table (Tsan) • Geolocation error (Weng) • MHS • On orbit MHS NEDT table (Tsan) • MHS and AMSU-B inter-comparison (Reale and Ferraro) • SBUV/2 • No report

3. NOAA-18 Instrument Payload We focus on these instruments: • AVHRR/4 Advanced Very High Resolution Radiometer • HIRS/4 High Resolution Infrared Sounder • AMSU-A Advanced Microwave Sounding Unit-A • MHS Microwave Humidity Sounder • SBUV/2 Solar Backscattered Ultraviolet Radiometer

4. Calibration and Validation Legend • PRT: Platinum Resistance Thermometers • NEDN/T: Noise Equivalent Delta Radiance/Temperature • ATOVS: Advanced TIROS Operational Vertical Sounder (TOVS) • TOAST: Total Ozone Analysis using SBUV/2 and TOVS • MSPPS: Microwave Surface and Precipitation Product System • NDVI: Normalized Difference Vegetation Index • SST: Sea Surface Temperature • UV: Ultraviolet • TPW: Total Precipitable Water • CLW: Cloud Liquid Water

5. ORA NOAA-18 Instrument Cal/Val Mission Goals • Monitor and improve NOAA-18 instrument post-launch calibration • Assess and quantify instrument noises though analyzing calibration target counts and channel measurements • Monitor possible instrument anomaly and provide recommended solution • Quantify satellite navigation and geolocation errors • Characterize other biases in radiance and products such as cross-track asymmetry through forward modeling and inter-satellite calibration • Validate NESDIS NOAA-18 products (ATOVS and MSPPS, TOAST, UV index, NDVI, SST) for operational implementation • Provide early demonstration and assessments of NOAA-18 data for improving numerical weather prediction through JCSDA

6. Mitch Goldberg: ORA/SMCD Division Chief, - Management and Technical Oversight Fuzhong Weng: ORA/SMCD/Sensor Physics Branch Chief and NOAA-18 cal/val team leader, instrument asymmetry and microwave products and algorithms, radiance bias assessments for NWP model applications Changyong Cao: HIRS instrument calibration Fred Wu: AVHRR VIS/IR instrument calibration Tsan Mo: AMSU/MHS instrument calibration Jerry Sullivan: AVHRR thermal channel calibration/ NDVI validation Tony Reale: HIRS/AMSU/MHS sounding channel/products validation Mike Chalfant: HIRS/AMSU/MHS sounding channel/products validation /geolocation Ralph Ferraro: AMSU/MHS window channels/MSPPS products validation Larry Flynn: SBUV product validation Tom Kleespies: AMSU on-orbit verification Hank Drahos: Sounding product validation Dan Tarpley: AVHRR product NDVI monitoring John LeMashall: Impacts assessments of NOAA-18 data for NWP applications Our Team

7. HIRS Cal/Val News • A telecon was held by NASA for the HIRS/NOAA-18 investigation. Evidence suggests that the noise in HIRS/NOAA-18 longwave channels are decreasing slowly after the initial drop last Friday. • A calibration trending website showing NEDN to assist in the diagnosis of the HIRS NEDN problem http://www.orbit.nesdis.noaa.gov/smcd/spb/multisensor/hirs/nedn • Developed experimental web based trending system in 2 days led by Dr. Changyong Cao • Longterm trend of all calibration cycles clearly shows that ch1 spaceview drifted out of range; a large upspike in count std before the noise drop • Web based trending time series is extremely useful for instrument diagnosis • More intercomparison results with NOAA-16 HIRS

8. HIRS/4 On-Orbit NEDN (6/14/2005) On-orbit NEDN needs to be fully assessed and is needed for NCEP data assimilation system and physical sounding retrieval system Red: channel noise can not be assessed Yellow: Noise level is assessed but out of spec.

9. N18 (left) vs N16 (right) for calibrated HIRS radiance temperature for channel 6 (upper) and 9 (lower); June 6-7, 18Z to 6Z. The color scales per channel, respectively are identical allowing direct color comparison. N18 channels are more noisy but less than for lower frequency channels 1 thru 5.

10. AVHRR Cal/Val News • AVHRR on-orbit verification of calibration target counts • Space and blackbody counts are stable • 4 PRT temperatures approach the same values, implying blackbody is in the equilibrium state as satellite moves into the dark part • AVHRR calibration algorithms work well • The blackbody temperature changes are monitored and shows in a small range of variability (only 2K) • Thermal channel (3-5) calibration is healthy • Wu’s Vis/IR calibration algorithms are working well • AVHRR NDVI products from NOAA-18 are of the similar quality to NOAA-16’s due to robust visible channel calibration • AVHRR geolocation error • 3 pixels (N-S) and 2 pixels (E-W) offsets are identified using the NDVI vegetation index as a land-sea tag

11. AVHHR Space and Blackbody Count SPACE: The Space Count is electronically clamped and should remain constant over many orbits. BLACKBODY: The blackbody temperature changes during an orbit, so the Blackbody Count also changes. However, for almost all 1-minute intervals, the temperature only varies by about 0.02K. An average blackbody count for 1 minute is computed, then the RMS (root-mean-square) around this average. The 1-minute RMS is plotted for many orbits: this is a measure of AVHRR stability when viewing a constant-temperature blackbody.

12. AVHRR Blackbody Temperature Monitoring When the NOAA-18 satellite moves into the dark (black portion of Solar Zenith Angle curve) the temperatures measured by the 4 PRTs approach each other, indicating a more uniform temperature across the blackbody. This is an important part of C. Cao’s assertion that the dark part of the orbit is the most accurate place to estimate the true AVHRR gain, a strategy we’ll use to preprocess the 25-year AVHRR data set.

13. AMSU Cal/Val News • It appears that AMSU-A2 has a geolocation error with one pixel offset in both E-W and N-S directions • AMSU-A2 and A1 window channel channels scan dependent biases are derived by differentiating radiative transfer simulations and measurements. Our preliminary results show AMSU-A2 module show less asymmetry than the previous AMSU-A2. However, AMSU-A1 module channel3 display larger asymmetry. The characterization of these asymmetry is needed for microwave products and improving NWP data assimilation quality control of using AMSU data • AMSU-A NEDT on orbit is calculated and shows nearly all channel meet specification • AMSU post-launch calibration parameter information data base (CPIDS) were successfully updated for larger cold space calibration counts • AMSU-A2 cold space calibration count errors tolerance is increased from 25 counts to 50 counts • Overall AMSU calibration algorithms are healthy with reasonable gains, and variability in cold and warm calibration targets

14. AMSU-A On-Orbit NEDT

15. NOAA-18 AMSU Asymmetry Characterization Vertical coordinate shows the mean differences between simulations and observations. Horizontal coordinate is the local zenith angle which corresponds to beam position from 1 to 30. AMSU-A2 module includes two frequencies of 23.8 and 31.4 GHz, A1 module include 50.3 and 89 GHz. It appears A2 module does not show any asymmetric features as previous AMSU-A2 which is very positive news. The results are preliminary and are based on 6 days of average.

16. NOAA-18 AMSU Geolocation Offset AMSU-A channel 1 image over the west coast of California. The striking contrast between land and ocean from microwave window channel is normally used for a sanity check for geolocation. It appears that there is one pixel offset in AMSU earth location in both E-S and N-S directions. This offset is being under investigation

17. MHS Cal/Val News • MHS was verified as being properly geolocated • he NOAA-18 MHS NEDT for each channel was calculated and is better than AMSU-B • MHS looks overall nominal except for a possible slight warm bias for the 183 +/- 1 and +/- 3 GHz channels. • MHS produces robust rainfall products and detect more light precipitation

18. MHS On-Orbit NEDT MHS AMSU-B

20. SBUV/2 Status • SBUV/2 is making some measurements in its standard operating mode • Ozone retrieval is performed. The change in total ozone behavior yesterday is probably related to a test switching from anode to cathode mode for the PMT

21. Overall Summary • Most instruments are meeting specification with the current exception of HIRS • AMSU-A NEDT meets specification • AVHRR NOAA-18 NDVI product appear to be consistent with NOAA-16 • MHS noise is lower than AMSU-B • All instruments except AVHHR/3) have been verified as being properly geolocated

22. Next Step • Continue monitoring HIRS/4 noises with the trending website and trending website updated for other sensors • Inter-satellite calibration using simultaneous nadir overpassing (SNO) method • Assess the readiness of AMSU and MHS with global forward model simulations for NWP applications