TH3.TO4.1.pptx

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TH3.TO4.1.pptx

  1. 1. Improving the AMSR-E snow depth product: recent developments<br />Richard Kelly<br />University of Waterloo, Canada.<br />
  2. 2. Outline<br />Current product: performance of the satellite only product<br />Development issues<br />RFI<br />Lake behaviour<br />Forest attenuation<br />Observations and Conclusions<br />
  3. 3. Current snow depth product:<br />Approach (AMSR-E observation-based)<br />where<br />fd=50%<br />ff=40%<br />r=12.5km<br />fd=10%<br />ff=40%<br />IFOV radius=12.5 km<br />Forest stand<br />
  4. 4. Performance (2002-2003)<br />
  5. 5. comments<br />Retrievals are conducted at the IFOV level (not at the grid-averaged level)<br />Retrievals are then aggregated to coarser grid (0.25x025 deg)<br />Tb correction (forest only) is built into the retrievals but not perfectly formulated.<br />RFI and water bodies not well accounted for.<br />
  6. 6. RFI issues<br />
  7. 7. RFI<br />Kidd, C.(2006) 'Radio frequency interference at passive microwave earth observation frequencies’, International Journal of Remote Sensing,27:18,3853 — 3865<br />
  8. 8. RFI impacts<br />MODIS-Daily<br />2 Feb. 2009<br />3 Feb. 2009<br />4 Feb. 2009<br />5 Feb. 2009<br />6 Feb. 2009<br />7 Feb. 2009<br />8 Feb. 2009<br />9 Feb. 2009<br />10 Feb. 2009<br />From sat.dundee.ac.uk<br />
  9. 9. RFI impacts<br />UK AMSR-E<br />Daily Snow 2.2.2009<br />Missing / bad<br />Water<br />320 – 540<br />160 - 320<br />80 - 160<br />40-80<br />1 - 40<br />0<br />SWE [mm]<br />
  10. 10. RFI impacts<br />10V-36V (current)<br />10V GHz<br />5 February 2009<br />
  11. 11. Adjusted retrievals without the use of the 10 GHz channel in UK.<br />
  12. 12. Lake issues<br />
  13. 13. Much of the Arctic and sub-Arctic are dominated by lake cover (fractions of 40% not uncommon). <br />At 25 km grid resolution lakes will play an important role<br />But what is that role and can lake signals be identified?<br />Time series of data for 9 years.<br />
  14. 14. Kang et al. (2010) GRSL 7(4)<br />
  15. 15. A note on gridding and AMSR-E measurement samples<br />Depending on the proximity threshold (x), may or may not be daily, but it will be for a consistent location<br />10 km<br />25 km<br />LOI<br />x<br />10 km<br />AMSR-E sampling grid<br />
  16. 16. MOD44W Water mask & MODIS VCF<br />25 km diameter circle averaged on 1 km grid<br />25km<br />Water Fraction<br /> 0-10%<br /> 11-20%<br /> 21-30%<br /> 31-50%<br /> >50%<br />Forest Fraction<br /> 0%<br />1-10%<br /> 11-20%<br />21-30%<br /> 31-50%<br /> >50%<br />0 400 km<br />
  17. 17. AMSR snow depth (0.25x0.25 deggridded)<br />Snow depth (cm)<br />Date<br />
  18. 18. Nearest WMO snow depth / air temperature<br />0% FF & 37% WF<br />Mean Temp (C)<br />Snow depth (cm)<br />0% FF & 35% WF<br />Date<br />
  19. 19. AMSR Tbs (36V & 18V): centre within 4 km of locations of interest<br />Tb (K)<br />Date<br />
  20. 20. AMSR Tbs (36V & 18V)<br />Lake <br />freeze-up<br />Snow and lake ice melt<br />Snow accumulation <br />on lake <br />
  21. 21. Forest fraction<br />
  22. 22. MOD44W Water mask & MODIS VCF<br />25 km diameter circle averaged on 1 km grid<br />Water Fraction<br /> 0-10%<br /> 11-20%<br /> 21-30%<br /> 31-50%<br /> >50%<br />Forest Fraction<br /> 0%<br />1-10%<br /> 11-20%<br />21-30%<br /> 31-50%<br /> >50%<br />0 400 km<br />
  23. 23. AMSR snow depth (0.25x0.25 deg gridded)<br />Snow depth (cm)<br />Date<br />
  24. 24. AMSR Tbs (36V & 18V): centre within 4 km of locations of interest<br />Tb (K)<br />Date<br />
  25. 25. Forest & lakes combined<br />
  26. 26. And when you mix forest and lakes….<br />MOD44W Water mask & MODIS VCF<br />25 km diameter circle averaged on 1 km grid<br />Water Fraction<br /> 0-10%<br /> 11-20%<br /> 21-30%<br /> 31-50%<br /> >50%<br />Forest Fraction<br /> 0%<br />1-10%<br /> 11-20%<br />21-30%<br /> 31-50%<br /> >50%<br />0 400 km<br />
  27. 27. AMSR snow depth (0.25x0.25 deg gridded)<br />Snow depth (cm)<br />Date<br />
  28. 28. 4% Water fraction and 55% forest fraction<br />
  29. 29. AMSR Tbs (36V & 18V): centre within 4 km of locations of interest<br />Tb (K)<br />Date<br />
  30. 30. Areas of development<br />RFI can be accommodated in the current implementation by a of 10 GHz observations with 18 GHz in the affected areas<br />Water fraction changes the nature of a Tb difference or ratio. 18 GHz is sensitive to lake ice thickness so that DTb is not necessarily a function of DSD or SWE.<br />Forest fraction/structure reduces sensitivity (known). But it is likely not a linear forest fraction attenuation effect<br />Forest and water fraction together require correction before SWE inversion is applied. Recent work by Langloiset al. (2011) has demonstrated new approach to transmissivity correction and lake fraction can likely be corrected for (ongoing work)<br />Operational implementation of forest and lake correction is yet to be completed.<br />
  31. 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?<br />AMSR-E/GCOM-W are at 10x14 km at 36 GHz. Perhaps a higher spatial resolution (e.g. 12.5km grid)?<br />Thank you<br />

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