1. Improving the AMSR-E snow depth product: recent developments Richard Kelly University of Waterloo, Canada.

2. Outline Current product: performance of the satellite only product Development issues – RFI – Lake behaviour – Forest attenuation Observations and Conclusions

3. Current snow depth product: Approach (AMSR-E observation-based) where fd=50% ff=40% r=12.5km fd=10% ff=40% IFOV radius=12.5 km Forest stand

4. Performance (2002-2003)

5. comments Retrievals are conducted at the IFOV level (not at the grid-averaged level) Retrievals are then aggregated to coarser grid (0.25x025 deg) Tb correction (forest only) is built into the retrievals but not perfectly formulated. RFI and water bodies not well accounted for.

6. RFI issues

7. RFI Kidd, C.(2006) 'Radio frequency interference at passive microwave earth observation frequencies’, International Journal of Remote Sensing,27:18,3853 — 3865

8. MODIS-Daily 2 Feb. 20093 Feb. 20094 Feb. 2009 5 Feb. 20096 Feb. 20097 Feb. 2009 8 Feb. 20099 Feb. 200910 Feb. 2009 From sat.dundee.ac.uk RFI impacts

9. UK AMSR-E Daily Snow 2.2.2009 Missing / bad Water 320 – 540 160 - 320 80 - 160 40-80 1 - 40 0 SWE [mm] RFI impacts

10. 10V GHz 10V-36V (current) 5 February 2009 RFI impacts

11. Adjusted retrievals without the use of the 10 GHz channel in UK.

12. Lake issues

13. Much of the Arctic and sub-Arctic are dominated by lake cover (fractions of 40% not uncommon). At 25 km grid resolution lakes will play an important role But what is that role and can lake signals be identified? Time series of data for 9 years.

14. Kang et al. (2010) GRSL 7(4)

15. A note on gridding and AMSR-E measurement samples 10 km AMSR-E sampling grid LOI Depending on the proximity threshold (x), may or may not be daily, but it will be for a consistent location x

16. Water Fraction 0-10% 11-20% 21-30% 31-50% >50% Forest Fraction 0% 1-10% 11-20% 21-30% 31-50% >50% 0 400 km MOD44W Water mask & MODIS VCF 25 km diameter circle averaged on 1 km grid 25km

17. Snow depth (cm) Date AMSR snow depth (0.25x0.25 deg gridded)

18. Nearest WMO snow depth / air temperature Snow depth (cm) Date Mean Temp (C) 0% FF & 37% WF 0% FF & 35% WF

19. Tb (K) Date AMSR Tbs (36V & 18V): centre within 4 km of locations of interest

20. AMSR Tbs (36V & 18V) Lake freeze-up Snow accumulation on lake Snow and lake ice melt

21. Forest fraction

22. Water Fraction 0-10% 11-20% 21-30% 31-50% >50% Forest Fraction 0% 1-10% 11-20% 21-30% 31-50% >50% 0 400 km MOD44W Water mask & MODIS VCF 25 km diameter circle averaged on 1 km grid

23. Snow depth (cm) Date AMSR snow depth (0.25x0.25 deg gridded)

24. AMSR Tbs (36V & 18V): centre within 4 km of locations of interest Tb (K) Date

25. Forest & lakes combined

26. Water Fraction 0-10% 11-20% 21-30% 31-50% >50% Forest Fraction 0% 1-10% 11-20% 21-30% 31-50% >50% 0 400 km And when you mix forest and lakes…. MOD44W Water mask & MODIS VCF 25 km diameter circle averaged on 1 km grid

27. Snow depth (cm) Date AMSR snow depth (0.25x0.25 deg gridded)

28. 4% Water fraction and 55% forest fraction

29. AMSR Tbs (36V & 18V): centre within 4 km of locations of interest Tb (K) Date

30. Areas of development RFI can be accommodated in the current implementation by a of 10 GHz observations with 18 GHz in the affected areas Water fraction changes the nature of a Tb difference or ratio. 18 GHz is sensitive to lake ice thickness so that  Tb is not necessarily a function of  SD or SWE. Forest fraction/structure reduces sensitivity (known). But it is likely not a linear forest fraction attenuation effect Forest and water fraction together require correction before SWE inversion is applied. Recent work by Langlois et al. (2011) has demonstrated new approach to transmissivity correction and lake fraction can likely be corrected for (ongoing work) Operational implementation of forest and lake correction is yet to be completed.

31. Is it not time we began looking at grids that are higher resolution – 25 km EASE grid was chosen because the SSM/I 37 GHz approximate this resolution? AMSR-E/GCOM-W are at 10x14 km at 36 GHz. Perhaps a higher spatial resolution (e.g. 12.5km grid)? Thank you