C5.08A: A multi-decadal, coastal sea surface temperature product for Australasia – why we need it - Helen Beggs
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This document discusses the need for a multi-decadal, high resolution (1 km) coastal sea surface temperature (SST) product for the Australasia region produced using Advanced Very High Resolution Radiometer (AVHRR) data. The Bureau of Meteorology has produced such a product from 1992 to present using direct broadcast AVHRR data from Australia and Antarctica. The product includes different levels of processing and temporal/spatial resolutions to suit various applications like coral bleaching monitoring and ocean model validation. New versions use adaptive calibration and error statistics techniques to improve SST accuracy compared to other products.
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C5.08A: A multi-decadal, coastal sea surface temperature product for Australasia – why we need it - Helen Beggs
- 1. A multi-decadal, coastal sea surface temperature product for Australasia – why we need it Helen Beggs1* , Christopher Griffin1 , Leon Majewski1 , Edward King2# , Janice Sisson1 and Zhihong Li1 1 Bureau of Meteorology, Melbourne, Australia 2 CSIRO Oceans and Atmosphere Flagship, Hobart, Australia *Leader, IMOS Satellite SST Products Sub-facility # Leader, IMOS Satellite Remote Sensing Facility
- 2. Why do we need 1 km resolution AVHRR SST Products? Passive infra-red sensors on polar- orbiting satellites provide the highest resolution SST observations from space (~1 km) but cannot sense SST under cloud. Pre-2002 (MODIS) the only wide swath, 1 km resolution, satellite SSTs available were direct- broadcast AVHRR SST from NOAA polar-orbiters.
- 3. Australia has direct broadcast AVHRR data back to 1992 from reception stations in Australia and Antarctica. Using this data set, Bureau of Meteorology has produced 23 years of Group for High Resolution SST (GHRSST) format products with error estimates and quality flags per pixel. IMOS 1 km AVHRR SST 1 month day+night L3S February 2008
- 4. Range of IMOS-GHRSST products N18: 04:01:33 N18: 2011-04-30 04:01:33 N18: 04:01:33 N18: 05:42:09 L1B Swath BT multi-swath, single sensor multi-swath, multi-sensor, multi-day (3-day) multi-swath, multi-sensor, (1-day)single swathSwath SST N19: 02:01:49 N19: 03:40:20 N18: 04:01:33 N19: 05:22:46 N18: 05:42:09 L3U L3C L3S L3S L2P + 6-day, 14-day, 1-month L3S
- 5. Why day-only, night-only and day+night L3S products? 2 km IMOS night L3S2 km IMOS day+night L3S 2 km IMOS day L3S 1 Jan 2014
- 6. L4 interpolated SST vs L3S composite SST 1 km G1SST L4 2 km IMOS night L3S 1 km MUR L4 2 km IMOS day+night L3S 2 km IMOS day L3S
- 7. Different IMOS-GHRSST Products suit different applications L3C (2 km gridded, multiple swath) Research into diurnal warming • Great Barrier Reef (Xiaofang Zhu, PhD Uni of Miami) • Tropical Warm Pool (Haifeng Zhang, PhD UNSW@ADFA) Mean Mar 2010 NOAA-19 ΔSST
- 8. Different IMOS-GHRSST Products suit different applications L3U (2 km gridded, single swath) Real-time SST maps • www.fishtrack.com • IMOS OceanCurrent (http://oceancurrent.imos.org.au/sst. php) OceanCurrent SST Map 6 May 2015
- 9. Different IMOS-GHRSST Products suit different applications L3S (gridded, multiple sensor) • Nowcasting of coral bleaching • ReefTemp NextGen uses night- only 1-day L3Shttp://www.bom.gov.au/mari newaterquality • Near RT maps of SST • IMOS OceanCurrent uses day-only, night-only 3-day L3S • Validation of high res ocean models ReefTemp 1-day SST Anomaly 1 Jan 2014
- 10. fv02 L2P SST on-line routine verification http://opendap.bom.gov.au:8080/thredds/fileServer/abom_imos_ghrsst_archive/v02.0fv02/Validation/web/index.html
- 11. fv02 L2P SST on-line verification http://opendap.bom.gov.au:8080/thredds/fileServer/abom_imos_ghrsst_archive/v02.0fv02/Validation/web/index.html
- 12. • See http://imos.org.au/sstproducts.html • Come to the Ocean Remote Sensing Users Workshop, Melbourne, 9th – 11th Nov 2015 • contact h.beggs@bom.gov.au Want to know more?
- 13. Additional slides for discussion
- 14. How does IMOS fv02 AVHRR L3C differ from Pathfinder AVHRR L3C SST? • Wider swath width • Higher spatial resolution - 1.1 km x 1.1 km cf 4.4 km x 1.1 km resolution at nadir • More ancillary fields - IMOS product has error estimates per pixel to comply with GHRSST spec • More satellites - IMOS uses all available NOAA satellites, Pathfinder only one at a time • IMOS back to 1992, Pathfinder back to 1981 • IMOS real-time, Pathfinder > 1 year behind • IMOS uses "adaptive calibration" and "adaptive error statistics" to "tune" AVHRR SSTs using regional in situ data to minimise error IMOS L3U Pathfinder L3C
- 15. Useful pixel-by-pixel information (following GHRSST 2.0 format) 20131007 night composite from multiple satellites "L3S" + wind speed + aerosol + sea ice fraction SST quality_level flags analysis bias standard_deviation count
- 16. Different IMOS-GHRSST Products suit different applications L3C (gridded, multiple swath) Research into diurnal warming • Great Barrier Reef (Xiaofang Zhu, PhD Uni of Miami) • Tropical Warm Pool (Haifeng Zhang, PhD UNSW@ADFA) Mean Mar 2010 NOAA-19 ΔSST Mean Mar 2010 ACCESS-R 10 m WindsMean Mar 2010 ACCESS-R SSI
- 17. fv02 L2P SST on-line verification http://opendap.bom.gov.au:8080/thredds/fileServer/abom_imos_ghrsst_archive/v02.0fv02/Validation/web/index.html
- 18. fv02 L2P SST on-line verification http://opendap.bom.gov.au:8080/thredds/fileServer/abom_imos_ghrsst_archive/v02.0fv02/Validation/web/index.html
- 19. Temporal Averaging vs Spatial Interpolation Eg. North Queensland, 1 Jan 2014 mean SSTfnd products 1-day 2 km L3S 3-day 2 km L3S 1-month 2 km L3S 6-day 2 km L3S Daily 1 km G1SST L414-day 2 km L3S
- 20. Temporal Averaging vs Spatial Interpolation Eg. North Queensland, 1 Jan 2014 night-only L3S products 1-day 2 km L3S 3-day 2 km L3S 1-month 2 km L3S 6-day 2 km L3S Daily 1 km G1SST L414-day 2 km L3S
- 21. Temporal Averaging vs Spatial Interpolation Eg. North Queensland, 1 Jan 2014 day-only L3S products 1-day 2 km L3S 3-day 2 km L3S 1-month 2 km L3S 6-day 2 km L3S Daily 1 km G1SST L414-day 2 km L3S
- 22. Multi-satellite day+night SSTfnd for 2 Jun 2014 3-day 2 km L3S 6-day 2 km L3S Daily 1 km MUR L4 1-day 2 km L3S 1-month 2 km L3S14-day 2 km L3S
- 23. New to fv02 IMOS AVHRR SST: “Adaptive Calibration”! • Running 1 year calibration window, adjusted monthly • Tuned on best matchups with in situ SST • Performance measured on an expanded matchup data set NOAA-19 Performance -0.35 -0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0 31/12/2004 31/12/2005 31/12/2006 31/12/2007 31/12/2008 Date Bias(Median) Two Channel Pathfinder Adaptive NLSST "3" Channel NOAA-19 Performance 0 0.1 0.2 0.3 0.4 0.5 0.6 31/12/2004 31/12/2005 31/12/2006 31/12/2007 31/12/2008 Date Bias(RSD) Two Channel Pathfinder Adaptive NLSST "3" Channel Median RSD Pathfinder IMOS 0.0 -0.1 -0.2 -0.3 2005 2006 2007 2008 2009 2005 2006 2007 2008 2009 0.6 0.4 0.2 0.0
- 24. Adaptive Sensor Specific Error Statistics (SSES) • Per platform basis • Rolling 1 year window adjusted frequently (every 1 to 6 days) • Measurements are weighted by time (120 day time constant) • Attributes considered (6- dimensions) − time of day, − satellite zenith angle, − quality level, − latitude, longitude, age SSES_bias
- 25. SSES Bias estimate performance • Applying the bias correction improves the bias compared with in situ SST at all quality levels • Dashed lines show before bias correction QL = 5 QL = 4 QL = 3 QL = 2 NOAA-12
- 26. SSES Standard Deviation • Standard deviation of AVHRR SSTs cf in situ SSTs at different quality levels are given in all IMOS SST files • Variation over time (median standard deviation over the in situ matchups) is shown at the right for NOAA-12 QL = 5 QL = 4 QL = 3 QL = 2
Hinweis der Redaktion
- Near-coastal applications such as high-res ocean models, fishing and coral bleaching nowcasting need accurate high res SST products with known uncertainties
- These products are available either as geolocated swath products (L2P) or 2 km gridded composite (level 3) SST products either as single swath (L3U), single satellite (L3C) or multiple satellite L3S products over a number of days to fill in the gaps due to cloud. The L3C and L3S products are available as day-only, night-only or day+night files up to real-time. Range of useful file types (swath/gridded, day/night/day+night, 1/3/6/14/30 day) for different applications Level 1a = unpacked data (engineering units) Level 1b = calibrated, geolocated data Level 2 = product in native, swath, format Level 3 = regridded data, L3U = 1 single swath remapped to a standard grid L3C = the combination of data from multiple swaths, from one sensor (over a defined time period) L3S = the combination of data from multiple swaths, from multiple sensors (over a defined time period, currently 1-day, 3-day, 6-day, 14-day and 1-month)
- During the day-time in regions of the ocean with clear skies, high solar radiation and low winds a warm layer can form in the top few meters of the ocean. The top few microns (thermal skin) in the tropics can experience diurnal warming of several degrees, as was the case on 1st January 2014 off Cairns.
- There are several statistically interpolated level 4 (L4) SST products available, including NASA’s 1 km daily global G1SST and MUR analyses that interpolate 1 km satellite SST data. G1SST ingests IMOS AVHRR SST and MODIS data whereas MUR ingests MODIS but no 1km AVHRR SSTs. However, global L4 products do not currently resolve either the diurnal cycle or the fine spatial ocean features close to reefs and coasts. Day-only or night-only IMOS SST products can be used to measure diurnal warming in coastal regions and SST changes over 2 km spatial scales as close as 2 km to coasts. Note that all daily L4 products interpolate between day and night SST data, and use the previous day's analysis combined with climatology to fill in where no data exists for that date. MUR and G1SST L4 are produced by NASA JPL. IMOS AVHRR 1-day L3S is produced by the Australian Bureau of Meteorology.
- IMOS day-only and night-only L3C products are being used in two PhD projects to study diurnal warming over the Great Barrier Reef and the Tropical Warm Pool.
- IMOS-GHRSST products are also used in a range of real-time coastal applications, such as FishTrack, IMOS OceanCurrent …
- … and the Bureau of Meteorology’s coral bleaching nowcasting system, ReefTemp NextGen. They are also being used to validate high resolution ocean models, such as 4 km eReefs and 10 km OceanMAPS.
- Validation plots for the IMOS AVHRR products are now available on line for each NOAA satellite, with verification against drifting buoys, IMOS ships, Argo floats and moored buoys.
- IMOS HRPT AVHRR SST swaths are wider than those for Pathfinder. Pathfinder has 4.4 km x 1.1 km pixels whereas IMOS has 1.1 km x 1.1 km pixels.
- Shows: night-time composite skin SST for multiple satellites. Quality level based on proximity to cloud only. Bias with respect to drifting buoy SSTs and corected to skin. Varies smoothly over space with latitude and longitude. Sst_count shows the number of observations that contributed to the composite. L2P flags field contains information on land, deviation from analysis, etc Analysis gives the most recent GAMSSA multi-sensor SST analysis. Standard deviation based on matchups with drifting buoys calculated daily but using a model that uses the past year of matchups weighted to most recent observations. sses_count field gives the degrees of freedom used in calculating the bias and standard deviation estimates.
- Note that all daily L4 products interpolate between day and night SST data, and use the previous day's analysis combined with climatology to fill in where no data exists for that date. G1SST L4 contain "foundation" SST, mostly night-time data. G1SST L4 is produced by the NASA OurOcean Project. IMOS AVHRR L3S is produced by the Australian Bureau of Meteorology.
- Note that all daily L4 products interpolate between day and night SST data, and use the previous day's analysis combined with climatology to fill in where no data exists for that date. G1SST L4 contain "foundation" SST, mostly night-time data. G1SST L4 is produced by the NASA OurOcean Project. IMOS AVHRR L3S is produced by the Australian Bureau of Meteorology.
- Note that all daily L4 products interpolate between day and night SST data, and use the previous day's analysis combined with climatology to fill in where no data exists for that date. G1SST L4 contain "foundation" SST, mostly night-time data. G1SST L4 is produced by the NASA OurOcean Project. IMOS AVHRR L3S is produced by the Australian Bureau of Meteorology.
- Mauve curve represents the pathfinder algorithm (2 channel linear daytime, 3 channel at night, non latitude banded), with an analysis SST term added to the fit. Tuned on best matchups with in situ SST (highest quality level, mid range winds, low deviation from “fitted norm”), Performance measured on an expanded dataset (lower quality allowed, relaxed bounds on other parameters).
- Quality level is determined from proximity to cloud using the CLAVR cloud determination system, time of day includes sun zenith angle such that prior to midday and post midday the angles have opposite sign. This provides a specific offset between ascending and descending orbits of the same platform, and is thus not intended to be used for continuous times throughout the day.