1. Cloud and sea ice masking at high latitudes Steinar Eastwood (met.no)

2. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 Cloud and sea ice masking at high latitudes General conditions Cloud masking SST and Sea ice Focus on the Arctic

3. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 General condition Good coverage by polar orbiters Satellite passes all times of day Winter: no day Summer: no night

4. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 General condition Good coverage by polar orbiters Satellite passes all times of day Winter: no day Summer: no night Twilight last longer

5. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 Cloud masking Much clouds and often persistent clouds Challenging with long twilight, cloud mask methods more uncertain Challenging with long night time periods General cloud mask schemes often underestimate cloud cover Need additional cloud tests for SST retrieval Probabilistic approach most flexible, easy to change how strict masking to apply

6. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 Probabilistic approach For AVHRR N17

7. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 SST and Sea Ice Include or Mask Radarsat SAR image

8. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 SST and Sea Ice Include or Mask Include –Ice Surface Temp Radarsat SAR image

9. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 SST and Sea Ice Include or Mask Include –Ice Surface Temp Mask –PMW Ice conc products OSI SAF ice concentration Greenland-Svalbard

10. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 SST and Sea Ice Include or Mask Include –Ice Surface Temp Mask –PMW Ice conc products –Coarse resolution, ice move around OSI SAF ice concentration Greenland-Svalbard

11. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 SST and Sea Ice Include or Mask Include –Ice Surface Temp Mask –PMW Ice conc products –Coarse resolution, ice move around –Need extra masking based on on-board instr. –Probabilistic approach most flexible AVHRR ch1,2,4

12. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 SST and Sea Ice – masking AVHRR ch 1,2,4AVHRR ch 2,6,4 Daytime: Can distinguish between clouds and ice using 1.6um or 3.7um, but do not need to. Twilight: 1.6um and 3.7um very week signal.

13. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 Night time algorithms (at met.no) ‏ Still under development Much harder to distinguish between cloud and ice

14. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 T4 T4-T5T4T3-T5 stdT4std(T3-T5)‏ std(T4-T5)‏

15. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 Sea ice in Skagerrak January-March 2010 N18 ch.1-2-4

16. GHRSST HL TAG meeting, Copenhagen, 17-03-2010 N18 ch 1-2-4 ch 2-3b-4

17. GHRSST HL TAG meeting, Copenhagen, 17-03-2010

18. Tasks for GHRSST HL TAG How is sea ice handled in each GHRSST product? –Use of daily ice concentration products? –Additional threshold or probabilistic masking? –Separate flags/indicators ? Document these issues Monitor performance Common efforts in creating training data, MDBs for sea ice with “dummy” stations