Validation in Arctic conditions Steinar Eastwood (met.no) David Poulter (NOCS) GHRSST9, Perros-Guirec OSI SAF METOP SST, days mean

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Validation in Arctic conditions What is special about the Arctic? Availability of in situ observations. How can we use the HRDDS? Some validation results and lessons learned during OSI SAF METOP SST validation work.

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Sea Ice concentration Areas of interest: –Inner Arctic –Outer Arctic (Barents Sea) –Arctic conditions (Baffin Bay, Hudson Bay, Labrador Sea)

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF What is special about Arctic? Dry atmosphere Low SST Illumination conditions High air-sea temperature difference Sea ice cover –MIZ –Polynyas –Climatologies From REMSS AMSR-E MDB All match-ups,

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF What is special about Arctic? Dry atmosphere Low SST Illumination conditions High air-sea temperature difference Sea ice cover –MIZ –Polynyas –Climatologies OSI SAF METOP SST, , 8 days mean

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF What is special about Arctic? Dry atmosphere Low SST Illumination conditions High air-sea temperature difference Sea ice cover –MIZ –Polynyas –Climatologies

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF What is special about Arctic? Dry atmosphere Low SST Illumination conditions High air-sea temperature difference Sea ice cover –MIZ –Polynyas –Climatologies

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF What is special about Arctic? Dry atmosphere Low SST Illumination conditions High air-sea temperature difference Sea ice cover –MIZ –Polynyas –Climatologies OSI SAF Ice Conc

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Dry atmosphere Low SST Illumination conditions High air-sea temperature difference Sea ice cover –MIZ –Polynyas –Climatologies , 8 days mean SST What is special about Arctic?

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF What is special about Arctic? Dry atmosphere Low SST Illumination conditions High air-sea temperature difference Sea ice cover –MIZ –Polynyas –Climatologies Well covered by polar orbiters.....but often cloudy

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Availability of in situ observations Drifting buoys during Usually very few drifting buoys visit the Arctic through GTS

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Availability of in situ observations Usually very few drifting buoys visit the Arctic through GTS “Poleward” project deploys more than 100 drifters in 2007 and 2008 Ships available, also in inner Arctic, but how representative for SST? Drifters trajectories since deployment (in 2007). Courtesy of Inga Koszalka, University of Oslo, Norway.

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF How to use HRDDS in validation? Find general performance of SST products from in situ in Arctic: –METOP –AATSR –AMSR-E Use HRDDS for more detailed validation studies –Intercomparison between satellites for more details METOP – AATSR METOP - AMSR

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Drifting buoys from Confidence level 4 and 5 Open sea only Daytime (T11,T12)Night time (T37,T11,T12) BiasStdNumBiasStdNum Global Arctic Inner Arctic Antarctic N-Atlantic Tropics METOP MDB validation (OSI SAF)

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF METOP MDB validation (OSI SAF) What about using conventional ship observations? High standard deviations, different biases compared to drifters Even in situ from research vessels show bad validation results DaytimeNight time BiasStdNumBiasStdNum Global Arctic Inner Arctic Antarctic N-Atlantic Tropics

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF In situ ship observations Select all ships that went into the inner Arctic during summer Plot the global match-ups for these ships during

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF AATSR MDB validation (Medspiration) Drifters from Confidence level 4 and 5 DaytimeNight time BiasStdNumBiasStdNum Global Arctic Antarctic N-Atlantic Tropics

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF AATSR MDB validation (Medspiration)

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF AMSR-E MDB validation (REMSS) Drifters from Provided by Chelle Gentemann Comparable results with Medspiration MDB All day BiasStdNum Global Arctic Antarctic N-Atlantic Tropics

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF AMSR-E MDB validation (REMSS) Global Arctic

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF High standard deviation at daytime in Arctic DaytimeNight time BiasStdNumBiasStdNum Global Arctic Antarctic N-Atlantic Tropics METOP MDB validation (OSI SAF)

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF HRDDS in Arctic Time series of average SSTs at the HR-DDS site in the Chukchi Sea; Black symbols represent METOP-A SSTs, dashed lines with symbols represent analysis SST products (green is OSTIA), dashed lines without symbols represent climatological products, solid lines represent model SSTs, large circles represent NOAA AVHRR observations. Note the general consensus of SST data, with the exception of three extremely cold METOP-A SSTs.

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF HRDDS in Arctic A scatter plot of the maximum negative deviation from reference SST for each HR-DDS granule at the Bear Island site against the median solar zenith angle for the granule.

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF High standard deviation at daytime in Arctic DaytimeNight time BiasStdNumBiasStdNum Global Arctic Antarctic N-Atlantic Tropics METOP MDB validation (OSI SAF)

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF METOP MDB validation (OSI SAF) Remove solar zenith angle cases in Arctic DaytimeNight time BiasStdNumBiasStdNum Global Arctic Antarctic N-Atlantic Tropics

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Cloud issues in the Arctic C A B SST close to twilight north of Bering Strait

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Cloud issues in the Arctic C A B A C B Extra cloud and ice flag in METOP SST retrieval Uses Bayesian approach to determine probabilities of clouds, ice and open water Uses fractions between visible channels –A3/A1 –A2/A1

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Cloud issues in the Arctic Applies the extra cloud and ice flag up to 90 degrees solar zenith angle (instead of 85)

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF HRDDS: AMSR-AATSR SST difference Bias (K) of whole area AMSR-E SSTs to whole area high quality AATSR SSTs in Arctic regions with a 360 minute time window. Mean bias is K, standard deviation is 1.47 K Positive bias at low SSTs, less at higher SSTs. Compares well with MDB comparison. Larger bias in inner Arctic compared to North Atlantic.

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF HRDDS: AVHRR-AATRS SST difference Positive bias at day, less at night Compares well with MDB comparisons Bias (K) of focus area METOP-A SSTs to focus area AATSR SSTs in Arctic regions with a 720 minute time window. Mean bias is 0.54 K, standard deviation is 1.11 K

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Conclusion Conventional shipobs are not reliable HRDDS is very useful for detailed validation studies in the Arctic IR SST products are usually accurate in the Arctic (std), but not always precise (biases) MW has some bias issues Mind your cloud masking in the Arctic!

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Extra slides

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF SST MDB tool On-line tool to list content of METOP SST MDB Station-by-station Monthly averages –Station –Area Mean or Central SST

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF SST vs ice concentration Ships also go into the sea ice. Measures the ice concentration, together with the SST.

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Deployment of “Poleward” drifters More info on: /

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Ship SST obs August – September 2006 A few ships in the Arctic.

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF Ship SST obs August – September 2007 More ships in the Arctic during the International Polar Year A few ship campaigns will go into the Arctic basin, and also into the sea ice.

GHRSST9 meeting, June 2008, Perros-Guirec OSI SAF First results from MDB, ships Available ships DBLK – Polar Stern (germ ocean.res.ship) NEPP – USCGC Healy (am ocean.res.ship) LAHV – Jan Mayen (nor ocean.res.ship) UANA – Fritjof Nansen (russ ocean.res.ship) LJIT – Håkon Mosby (nor ocean.res.ship) LMEL – G.O.Sars (nor ocean.res.ship) ++