The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Systematic biases in satellite SST observations and analyses over the Southern Ocean Helen Beggs and George Paltoglou Centre for Australian Weather and Climate Research, Bureau of Meteorology, Melbourne, Australia Presented to GHRSST HL-TAG Workshop, Boulder, 2 March 2011

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Introduction Divergence of Satellite SST data streams over Southern Ocean Divergence of SST analyses over Southern Ocean RAMSSA L4 analysis case study for Nov 2007 New calibration of daytime HRPT AVHRR SSTskin using latitude in airmass term Way forward?

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Existing Southern Ocean Satellite SST Observations South of 45°S large bias separation between different satellite SST data streams Is this due to differences in calibration of AVHRR and AMSR-E SST over Southern Ocean? Could this cause the wide divergence of different daily SST analyses over Southern Ocean? Reynolds et al., (2010) J. Climate Nighttime Mean Zonal Satellite Bias wrt Reynolds AMSR+AVHRR SST (1 Jan 2006 – 31 Dec 2008)

L4 SST - GHRSST Multi-Product Ensemble L4P SST (14 Apr 2010) CMC MW+IR OSTIA MW+IR GAMSSA MW+IR MGDSST MW+IRRTG IR NCDC IR

CMC minus GMPE (L4-SQUAM) Satellite SST bias-corrected using buoys and ships

OSTIA minus GMPE (L4-SQUAM) Satellite SST bias-corrected using AATSR and buoys

GAMSSA minus GMPE (L4-SQUAM) No bias-correction apart from using sses_bias values in L2P files

RTG (Hi-Res) minus GMPE (L4-SQUAM)

NCDC AMSR-E + AVHRR minus GMPE (L4-SQUAM) Satellite SST bias-corrected using buoys and ships

GMPE minus Drifting Buoys (L4-SQUAM)

Mean(RAMSSA SSTfnd minus MW+IR Analysis SST) 1 – 30 Nov 2007 Reynolds AMSR-E + AVHRRODYSSEA OSTIAREMSS MW + IR Beggs et al. (2011) AMOJ

StDev(RAMSSA SSTfnd minus MW+IR Analysis SST) 1 – 30 Nov 2007 Reynolds AMSR-E + AVHRRODYSSEA OSTIAREMSS MW + IR Beggs et al. (2011) AMOJ

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology RAMSSA SSTfnd minus MW+IR Analysis SST Matchups between RAMSSA SSTfnd and different multi-sensor SST analyses from GHRSST GDAC Dates: 1 – 30 Nov 2007 Domain: “North”: 20  N – 40  S, 60  E – 170  W “South”: 40  S – 70  S, 60  E – 170  W Matchup criteria: Data matched if within 24 hours. Coarser resolution analyses were linearly interpolated to grid resolution of higher resolution analysis.

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Satellite SSTfnd minus Buoy SSTfnd SSTfnd obtained by filtering out observations where: day NWP winds < 6 m/s night NWP winds < 2 m/s Matchups between different satellite SSTfnd data streams and buoy SSTfnd observations Dates: 1 – 30 Nov 2007 Domain: “North”: 20  N – 40  S, 60  E – 170  W “South”: 40  S – 70  S, 60  E – 170  W Matchup criteria: Data matched if within 24 hours and within +/- 1/24  lat and lon Note: HRPT AVHRR SST used were Legacy BoM products

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology IMOS NOAA-19 HRPT AVHRR SSTfnd vs Drifting Buoy SSTfnd (Night) Matchups weighted towards high and low latitudes for regression coefficients

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology IMOS NOAA-19 HRPT AVHRR SSTfnd vs Drifting Buoy SSTfnd (Day) Latitude dependent air-mass term in BT  SST algorithm Matchups weighted towards high and low latitudes for regression coefficients

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology How to improve satellite SST accuracy over Southern Ocean? Sustain dual-view, along-track, scanning radiometers on satellites (eg. AATSR, SLSTR, …) Improve cloud and ice masking Improve calibration of AVHRR and geostationary satellite IR SST sensors Physical retrieval methods Regional rather than global cal Improve single pixel error estimates Deploy a sustained array of radiometers on ships to validate satellite IR SST Improve the availability and accuracy of SSTdepth observations over Southern Ocean from: ships moored buoys Drifting buoys Argo floats CTDs on seals, penguins, …. BoM/IMOS IMOS

CTDs on Elephant Seals send RT Southern Ocean data to GTS

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Extra Slides for discussion

IMOS Southern Ocean Flux Station Deployed 17 March 2010 at 47  S, 142  E Hourly averages available from IMOS Ocean Portal every 4 hours Data streams: –SST –Salinity –Air Temperature –Winds –Humidity –SW and LW radiation –Air pressure –Precipitation

Skin SST Radiometer on Southern Ocean Cruise CSIRO’s DAR011 radiometer deployed on RV Southern Surveyor during SOFS mooring deployment cruise in March m winds > 5 m/s for study period Contact for data DAR011 SSTskin Ship SBE 3 SST6m Mooring SST1m

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology RAMSSA SSTfnd(date) minus Analysis SST(date) Over region: 60°E - 180°E, 20°N - 65°S (RAMSSA domain) Period: 1 Oct 2007 – 31 Mar 2008 ODYSSEA MW+IR Daily 1/10° SSTfnd: ± 0.40°C OSTIA MW+IR Daily 1/20° SSTfnd: 0.10 ± 0.35°C BoM Legacy Daily 1/4° SSTblend: 0.07 ± 0.46°C Reynolds MW+IR Daily 1/4° SSTblend: 0.00 ± 0.54°C RSS MW+IR Daily ~1/11° SSTfnd: 0.07 ± 0.53°C

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Analysis SST(date) minus Buoy SSTfnd(date+1) Over region: 60°E - 180°E, 20°N - 65°S (RAMSSA domain) Period: 1 Oct 2007 – 31 Mar 2008 RAMSSA MW+IR Daily 1/12° SSTfnd: 0.0 ± 0.4°C OSTIA MW+IR Daily 1/20° SSTfnd: 0.0 ± 0.4°C ODYSSEA MW+IR Daily 1/10° SSTfnd: 0.1 ± 0.5°C RSS MW+IR Daily ~1/11° SSTfnd:-0.1 ± 0.5°C Reynolds MW+IR Daily 1/4° SSTblend: 0.0 ± 0.6°C BoM Legacy Daily 1/4° SSTblend: -0.1 ± 0.6°C

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Analysis SST (date) minus Buoy SSTfnd(date+1) Over region: 180°W to 180°E, 75°N - 75°S (global) Period: 20 May – 30 Aug 2008 OSTIA MW+IR Daily 1/20° SSTfnd:-0.07 ± 0.44°C GAMSSA MW+IR Daily 1/4° SSTfnd:-0.04 ± 0.50°C ODYSSEA MW+IR Daily 1/10° SSTfnd: ± 0.58°C NCDC MW+IR Daily 1/4° SSTblend:-0.03 ± 0.64°C BoM Operational Weekly 1° SST1m: ± 0.71°C

L4 SST - GHRSST Multi-Product Ensemble L4P SST (14 Apr 2010) CMC MW+IR UKMO OSTIA MW+IRBoM GAMSSA MW+IR JMA MGDSST MW+IR RTG IRNCODA MW+IR

Regional Australian Multi-Sensor SST Analysis System (Contact: Helen Beggs) Based on legacy BoM optimal interpolation regional SST analysis system Depth: Foundation (pre-dawn SST) Resolution: Daily, 1/12° Domain: 60°E - 170°W, 20°N - 70°S Start: 0130 UT, Finish: ~0430 UT Data Inputs: 1 km HRPT AVHRR (NOAA-18, -19) 9 km NAVOCEANO GAC AVHRR (NOAA-18, METOP-A) L2P 25 km AMSR-E (Aqua) L2P 1/6° AATSR (EnviSat) Buoy and ship obs (GTS) 1/12° NCEP ice concentration analyses BGF: Combination of previous day’s RAMSSA and BoM Weekly Global SST Analysis Uses: Boundary condition for BoM operational regional NWP models (LAPS 0.375, MesoLAPS, TCLAPS, ACCESS-R, ACCESS-A, ACCESS-C, …) Validating OceanMAPS SST5m analyses/forecasts V1.0: Operational 13 Jun 2007 RAMSSA analyses available as netCDF L4 files from ftp://podaac.jpl.nasa.gov/pub/GHRSST/ data/L4/AUS/ ftp://podaac.jpl.nasa.gov/pub/GHRSST/ data/L4/AUS/ See ceantemp/sst.shtml ceantemp/sst.shtml

Global Australian Multi-Sensor SST Analysis System (Contact: Helen Beggs) Based on RAMSSA v1.2 code Depth: Foundation (pre-dawn SST) Resolution: Daily, 1/4° Domain: global Start: 0230 UT, Finish: ~0500 UT Data Inputs: 9 km NAVOCEANO GAC AVHRR (NOAA-18, METOP-A) L2P 25 km AMSR-E (Aqua) L2P 1/6° AATSR (EnviSat) Buoy and ship obs (GTS) 1/12° NCEP ice concentration analyses BGF: Combination of previous day’s GAMSSA and Reynolds climatology Uses: Boundary condition for BoM operational global NWP model (ACCESS-G) Initialisation of new seasonal forecast models (POAMA 2.0) V1.0: Operational 2 Oct 2008 GAMSSA analyses available as GHRSST-L4 files from ftp://podaac.jpl.nasa.gov/pub/GHRSST/ data/L4/GLOB/ABOM ftp://podaac.jpl.nasa.gov/pub/GHRSST/ data/L4/GLOB/ABOM

Drifting + Moored Buoys Input observations for regional SST analysis

1 km HRPT AVHRR SST1m 17 km AATSR SSTskin 25 km AMSR-E L2P SSTsubskin 9 km x 4 km GAC AVHRR L2P SST1m

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Filtering for Diurnal Warming Events Using hourly mean surface wind speeds from BoM  resolution NWP forecast model: During Day-time: Remove observations where wind < 6 m/s During Nighttime: Remove observations where winds < 2 m/s Thresholds based on Donlon et al. (2002) 1 – 30 Nov 2006: 60°E - 170°W, 20°N - 70°S

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology How does RAMSSA compare with other IR + MW SST GHRSST-L4 analyses available from ftp://podaac.jpl.nasa.gov/pub/GHRSST/data/L4/GLOB/ftp://podaac.jpl.nasa.gov/pub/GHRSST/data/L4/GLOB/ ?

RAMSSA  L4 SSTfnd OSTIA 0.05  L4 SSTfnd NCDC 0.25  AMSRE+AVHRR L4 SSTblend RSS 0.09  MW+IR L4 SSTfnd OSTIA 0.05  L4 SSTfnd

NCDC 0.25  AMSRE+AVHRR L4 SSTblendRAMSSA  L4 SSTfnd RSS 0.09  MW+IR L4 SSTfnd OSTIA 0.05  L4 SSTfnd STD = 0.42 K STD = 0.57 K STD = 0.39 K STD = 0.58 K

ODYSSEA 0.1  L4 SSTfndRAMSSA  L4 SSTfnd RSS 0.09  MW+IR L4 SSTfnd OSTIA 0.05  L4 SSTfnd STD = 0.42 K STD = 0.49 K STD = 0.39 K STD = 0.58 K

RSS MW+IR 1/11  SSTfnd Reynolds AMSR-E+AVHRR 1/4  SSTblend Met Office OSTIA 1/20  SSTfnd Ifremer ODYSSEA 1/10  SSTfnd

RSS MW+IR 1/11  SSTfnd Reynolds AMSR-E+AVHRR 1/4  SSTblend Met Office OSTIA 1/20  SSTfnd Ifremer ODYSSEA 1/10  SSTfnd

Improving Ship SSTdepth Observations Matchups between MTSAT-1R SST and drifting buoys, moored buoys and IMOS ships for 1 Jan 2008 to 19 Apr 2010

Improving Ship SSTdepth Observations Matchups between MTSAT-1R SST and drifting buoys, moored buoys, non-IMOS ships and IMOS ships for 1 Jan 2008 to 19 Apr 2010 My dream! – accurate SST sensors on all VOS ships reporting SST obs to the GTS

GAMSSA SSTfnd(date) minus Analysis SST(date) Over region: 180°W to 180°E, 75°N - 75°S (global) Period: 20 May – 30 Aug 2008 GAMSSA – OSTIA MW+IR Daily 1/20° SSTfnd: 0.07 ± 0.46°C GAMSSA – ODYSSEA MW+IR Daily 1/10° SSTfnd: ± 0.58°C GAMSSA – BoM Operational Weekly 1° SST1m: 0.00 ± 0.61°C GAMSSA – NCDC MW+IR Daily 1/4° SSTblend:-0.02 ± 0.62°C