Report from breakout session in the High Latitude Working group Prepared by Jacob L. Høyer, Bob Grumbine and Steinar Eastwood

Agenda GDS 2.0 review related to high latitudes In situ observation overview Peter Minett Steinar Eastwood Jacob Høyer L2P ice treatment survey DW in Antarctica OSI-SAF Sea ice reanalysis (Jacob)

GDS 2.0 discussion How do the GDS 2.0 specifications meet the needs for the high latitudes ? L2P sea_ice_fraction sea_ice_fraction_dtime_from_sst sources_of_sea_ice_fraction l2p_flags L3 sea_ice_fraction sea_ice_fraction_dtime_from_sst sources_of_sea_ice_fraction l2p_flags L4 sea_ice_fraction land/sea/ice mask

GDS2.0 discussion: L2P sea_ice_fraction Sea ice fraction from concentration or 0/100 from ice edge. Only required for SST pixels Debate: Sea ice cover to be a requirement for all pixels (also where no SST is present ) ? Recommendation: put in an optional field, maybe idea for netcdf 4

GDS2.0 discussion: L2P Discussion: How can instrument ice detection information be transparent to the user? Suggesting an attribute (table ?): sea_ice_treatment 1. Use unmodified 2. Use multiple ice sources (not modified) 3. modified ice information using onboard sensors Leave it to the producers when they will modify their ice information

GDS2.0 discussion, L2P sea_ice_fraction_dtime_from_sst (time, nj, ni) Overkill, considering the nature of the sea ice products, give the times and source (daily/weekly) in the attribute. If multiple sources, list more in attributes. Recommendation: Skip field, put in attribute free form string/table values

GDS2.0 discussion L2P L2p_flags: Collapse river and lake into a inland waters ?

GDS2.0 discussion L3P No major comments, since these are carried through from the L2P

GDS2.0 discussion L4 sea_ice_fraction Very different from one producer to the next on how the sea ice treatment is done and included. When multiple sources, keep it as an attribute, and state the sources Stating the sources: either it is external ice field or the ice fields available in L2P. Recommend to Include sea_ice_fraction_error estimate if available in optional field, encourage sea ice producers to make it available

Sea Ice Survey HL-TAG organized a survey to all GHRSST L2P producers to better understand how they handles the issue of sea ice in their production chains. Sent the survey to 9 producers, got 6 answers (thanks ! ): –NAVO (Bruce McKenzie)AVHRR –JAXA (Misako Katchi)AMSR-E –PML (Peter Miller)AVHRR HRPT –MODIS (Peter Minnett)MODIS Aqua/Terra –OSI SAF (Pierre LeBorgne)METOP AVHRR –ARC (Chris Merchant)ATSR-1, ATSR-2 and AATSR

Sea Ice Survey, questions 1.External sea ice data source 2.Include Masking retrieval procedures 3.Other specific tests in addition to the cloud mask 4.Day, night, twilight differences 5.Validation of sea ice masking 6.How do you deal with sea ice over lakes 7.Plans to produce IST

Sea Ice Survey, conclusion Many producers use sea ice mask from PMW Some producers have identified ice tests within their cloud mask system Only OSI-SAF has additional ice mask step in addition to cloud mask If a global cloud mask is used, we recommend that additional instrument tests are performed (twilight issues) Very limited documented validation of the performance of the ice masking No specific plans to include Ice Surface Temperature in the production chains Full survey available on ghrsst.org –> HL_TAG

Diurnal warming in the Antarctic DW events of several K in the Antarctic Less frequent than in the Arctic Mostly in sheltered bays IFREMER/NAIAD allows a systematic remapping and visualisation of full resolution AVHRR SST AVHRR/METOP, MODIS/A and MODIS/T agree quite well in general in the Antarctic

IABP Meeting in Oslo Steinar participated in IABP meeting in Oslo Most buoy deployments on ice Need for more buoys in the high latitudes

Other in situ obs Maeri Surface drifters Argo floats Ship TSG Sea ice mass balance buoys Ice camps Research vessels Maeri Argo floats

Conclusions GDS 2.0: In general the HL-TAG supports the GDS2.0 specifications Minor comments to treatment of sea ice Sea ice treatment HL-TAG encourage the producers to validate the L2P products in the vicinity of the sea ice regions (MIZ) Encourage the L2P producers to have onboard instrument Recommend a sea ice GMPE/SUQAM

Conclusions In situ observations: HL-TAG will produce a summary of the in situ observations available for validating high latitude SST observations HL-TAG recommend more observations in the high latitudes (buoys and radiometer) Preliminary plans about a joint HL-TAG, DV-TAG and STVAL-TAG intersession meeting in February 2011.

Tasks Tasks: In situ observation overview (Jacob and Steinar) We need more information in the Arctic !! Put the sea ice survey on the web (Jacob and Steinar) Monitoring maps ?, distinguish between GTS and not.

Tasks 9 producers, 6 answers, thanks ! Most producers trust cloud mask to deal with sea ice or -1.8 cut off Several use an additional ice mask If global cloud mask use, we recommend additional instrument tests in (investigations have shown that (long period of low sun angle)

New members Dick Anne Gary, Fred Sonia