ESA DUE GLOBSNOW Investigating Hemispherical Trends in Snow Accumulation Using GlobSnow Snow Water Equivalent Data Kari Lu...
ESA-funded GlobSnow project: Production of hemispherical scale snow extent (SE) and snow water equivalent (SWE) climate da...
GlobSnow: Long term snow products <ul><li>SWE (30 years) and SE product (15 years) + NRT demonstration </li></ul><ul><ul><...
GlobSnow – SWE ECV <ul><li>A new State-of-the-Art Snow Water Equivalent (SWE) climate data record </li></ul><ul><li>Work i...
SWE product (development by FMI & EC) <ul><li>SWE climate record for 1979 - 2010   (+ NRT demonstration) </li></ul><ul><ul...
Overview for the SWE product <ul><li>Daily maps of hemispherical snow cover: </li></ul><ul><ul><li>SWE for the permanent s...
Daily SWE product: 15 February 2008 Northern Hemisphere
SWE algorithm selection & retrieval validation <ul><li>Daily SWE estimates acquired with 5 algorithms evaluated for Eurasi...
Validation data – INTAS SSCONE data <ul><li>INTAS SSCONE data (from the former USSR and Russia) </li></ul><ul><ul><li>Ther...
Overall performance for SWE algorithms Eurasia 09/1994 – 12/1997 Evaluation with 450 INTAS snow courses 29559 29451 65.9 m...
Consistency of GlobSnow SWE retrieval  1980 - 2009 SWE<150 mm All SWE <ul><li>RMS error and retrieval bias calculated inde...
AMSR-E vs. SSM/I evaluations (2003 - 2010) <ul><li>GlobSnow SWE PMW sensor changes from SSM/I to AMSR-E at the beginning o...
<ul><li>Change of bias: DMSP-F13 results in higher snow mass (SWE) than AMSR-E, but DMSP-F17 gives a lower snow mass after...
AMSR-E vs. SSM/I trend (1980 - 2010)
SSMI, -8,2% trend for 30 years AMSR-E, -9.6% trend for 30 years AMSR-E vs. SSM/I trend (1980 - 2010)
Summary on SWE product  <ul><li>Current long term datasets on Global scale:  Monthly  from 1978,  daily  from 2002 </li></...
GlobSnow Snow Extent Dataset 28.07.11 Finnish Meteorological Institute <ul><li>SE retrieval using ERS-2 ATSR-2 and Envisat...
Daily, weekly and monthly products April 2003 19 April 2003 10 April 2003 Optical data ~ 1km spatial resolution
Examples of monthly products, 2003 April 2003 May 2003 June 2003
28.07.11 Finnish Meteorological Institute <ul><li>30+ year daily Snow Water Equivalent climate record (25 km resolution) <...
SWE algorithm evaluations: Eurasia 1994-1997 <ul><li>Detailed analyses reported within GlobSnow project documentation </li...
SWE product & trend analyses Average SWE for March 1997 Mean snow mass for March (30 year trend)
SWE product & mountain hydrology <ul><li>Baseline SWE dataset does not include estimates for mountains </li></ul><ul><ul><...
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aft_4_Luojus_GlobSnow_IGARSS_2011_final.ppt

  1. 1. ESA DUE GLOBSNOW Investigating Hemispherical Trends in Snow Accumulation Using GlobSnow Snow Water Equivalent Data Kari Luojus ( Finnish Meteorological Institute) J. Pulliainen, M. Takala, J. Lemmetyinen (FMI) C. Derksen, L. Wang (EC) S. Metsämäki (SYKE), B. Bojkov (ESA) GlobSnow project consortium: FMI, NR, ENVEO, GAMMA, SYKE, EC, Norut
  2. 2. ESA-funded GlobSnow project: Production of hemispherical scale snow extent (SE) and snow water equivalent (SWE) climate data records; along with a demonstration of a near real time processing and data dissemination chain for the products. Consortium; Finnish Meteorological Institute (FMI) with ENVEO IT GmbH (Austria), GAMMA Remote Sensing (Switzerland), Norwegian Computing Center, Finnish Environment Institute (SYKE), and Environment Canada (EC). Products and project details: www.globsnow.info Near-real-time snow map production on-going since: 1 October 2010 ESA GlobSnow
  3. 3. GlobSnow: Long term snow products <ul><li>SWE (30 years) and SE product (15 years) + NRT demonstration </li></ul><ul><ul><li>Primary products: </li></ul></ul><ul><ul><ul><li>Daily SWE / Daily fractional SE </li></ul></ul></ul><ul><ul><li>Secondary products: </li></ul></ul><ul><ul><ul><li>Weekly SWE / SE (mean and maximum) </li></ul></ul></ul><ul><ul><ul><ul><li>Sliding average: data from current day + previous 6 days </li></ul></ul></ul></ul><ul><ul><ul><ul><li>1 file for every day </li></ul></ul></ul></ul><ul><ul><ul><li>Monthly SWE / SE(mean and maximum) </li></ul></ul></ul><ul><ul><ul><ul><li>12 files per year: January, February, March… </li></ul></ul></ul></ul><ul><ul><li>Spatial coverage: Northern Hemisphere (both SE & SWE) </li></ul></ul>
  4. 4. GlobSnow – SWE ECV <ul><li>A new State-of-the-Art Snow Water Equivalent (SWE) climate data record </li></ul><ul><li>Work initiated at HUT/LST during 1990’s by Profs Pulliainen and Hallikainen </li></ul><ul><li>SWE Methodology (main body of work) published 2006 in RSE by Pulliainen </li></ul><ul><li>Past 5 years the work has been carried at FMI Arctic research centre </li></ul><ul><li>Shifted in high gear for ESA DUE GlobSnow (T.O. ESA/ESRIN: B.Bojkov) </li></ul><ul><li>-> Past 3 years of work by an experienced team (key people originally HUT/LST + team at Environment Canada) have resulted in a new SWE climate record (daily, 1979 – 2010, hemispherical SWE record) </li></ul><ul><li>Validation, spanning NH, indicates a new level of accuracy for SWE retrieval </li></ul><ul><li>Production of 30+ years SWE data on a (FMI Cray 5 XTm) super computer </li></ul><ul><li>Results presented in earlier conferences & a journal article in press (and a project document library for GlobSnow users) </li></ul>
  5. 5. SWE product (development by FMI & EC) <ul><li>SWE climate record for 1979 - 2010 (+ NRT demonstration) </li></ul><ul><ul><li>Spaceborne microwave radiometer data </li></ul></ul><ul><ul><ul><li>AMSR-E data (2003 – present) </li></ul></ul></ul><ul><ul><ul><li>SSM/I data (1987 – 2002) </li></ul></ul></ul><ul><ul><ul><li>SMMR data (1979 – 1987) </li></ul></ul></ul><ul><ul><ul><li>+ Global weather station data from WMO stations </li></ul></ul></ul><ul><li>Produced in EASE-grid projection ~ 25km resolution </li></ul><ul><li>Product includes error estimates for each SWE value </li></ul>
  6. 6. Overview for the SWE product <ul><li>Daily maps of hemispherical snow cover: </li></ul><ul><ul><li>SWE for the permanent seasonal snow area </li></ul></ul><ul><ul><li>Total snow area (Snow Extent) </li></ul></ul><ul><li>Regions with high topograpical variability are masked out </li></ul><ul><ul><li>Alpine regions </li></ul></ul><ul><ul><li>Glaciers </li></ul></ul><ul><ul><li>Greenland </li></ul></ul><ul><li>NRT production of SWE demonstrated in 2010-2011 </li></ul><ul><li>NRT to be transferred to EUMETSAT H-SAF late 2011 </li></ul><ul><li>Data format HDF4 & NetCDF CF </li></ul><ul><li>Data access through FTP & WWW </li></ul>
  7. 7. Daily SWE product: 15 February 2008 Northern Hemisphere
  8. 8. SWE algorithm selection & retrieval validation <ul><li>Daily SWE estimates acquired with 5 algorithms evaluated for Eurasia (1994-1997) </li></ul><ul><li>FMI Assimilation algorithm (Pulliainen 2006) </li></ul><ul><li>EC SWE suite (Goodison, Walker, Goita, Derksen et al. 1993-2009) </li></ul><ul><li>Chang et al. 1987 (original channel difference algorithm) </li></ul><ul><li>SPD-algorithm (Asbacher 1989) </li></ul><ul><li>Armstrong and Brodzik 2001-algorithm (Improved channel difference) </li></ul><ul><li>SWE estimates computed between 09/1994 and 12/1997 (SSM/I data) </li></ul><ul><li>Chang, SPD and Armstrong –algorithms were evaluated for both asc & desc nodes; FMI uses desc node data complemented with asc node data </li></ul><ul><li>Evaluations for North America and Finland were carried out in addition to the analyses for Eurasia </li></ul>
  9. 9. Validation data – INTAS SSCONE data <ul><li>INTAS SSCONE data (from the former USSR and Russia) </li></ul><ul><ul><li>There are 1294 snow path stations with data from the USSR </li></ul></ul><ul><ul><ul><li>Manual ground-based measurements on snow depth </li></ul></ul></ul><ul><ul><ul><li>Used as the validation data for the GlobSnow evaluations </li></ul></ul></ul><ul><ul><ul><li>There were 450 path stations with data for 1994-1997 </li></ul></ul></ul>
  10. 10. Overall performance for SWE algorithms Eurasia 09/1994 – 12/1997 Evaluation with 450 INTAS snow courses 29559 29451 65.9 mm 63.9 mm 0.052 0.121 -12.7 mm -3.1 mm 67.1 mm 63.9 mm SPD algorithm (asc node) SPD algorithm (desc node) 26726 27521 71.1 mm 70.8 mm 0.011 0.029 -8.4 mm 1.6 mm 71.6 mm 70.7 mm Chang et al. 1987 (asc node) Chang et al. 1987 (desc node) 21796 24791 57.3 mm 59.9 mm 0.044 0.029 -44.1 mm -42.9 mm 72.3 mm 73.7 mm Armstrong et al. 2001 (asc node) Armstrong et al. 2001 (desc node) 18109 61.5 mm 0.210 -28.2 mm 67.6 mm EC algorithm 26063 43.1 mm 0.611 -3.1 mm 43.2 mm FMI algorithm - (selected for GlobSnow) Samples Unbiased RMSE Corr.coeff bias RMSE Name
  11. 11. Consistency of GlobSnow SWE retrieval 1980 - 2009 SWE<150 mm All SWE <ul><li>RMS error and retrieval bias calculated independently for each year </li></ul><ul><li>Consistent inter-annual characteristics & minimal difference between sensors </li></ul>AMSR-E F 13 SSM/I F 11 SSM/I F 8 SSM/I SMMR AMSR-E F 13 SSM/I F 11 SSM/I F 8 SSM/I SMMR AMSR-E F 13 SSM/I F 11 SSM/I F 8 SSM/I SMMR AMSR-E F 13 SSM/I F 11 SSM/I F 8 SSM/I SMMR
  12. 12. AMSR-E vs. SSM/I evaluations (2003 - 2010) <ul><li>GlobSnow SWE PMW sensor changes from SSM/I to AMSR-E at the beginning of 2003 </li></ul><ul><ul><li>FPS v1.0 (current sensor set) </li></ul></ul><ul><ul><ul><li>SMMR 1979 – 1987 </li></ul></ul></ul><ul><ul><ul><li>SSM/I 1987 – 2002 </li></ul></ul></ul><ul><ul><ul><li>AMSR-E 2003 – 2010 </li></ul></ul></ul><ul><ul><li>Possible alternative sensor set (e.g. NSIDC sea ice) </li></ul></ul><ul><ul><ul><li>SMMR 1979 – 1987 </li></ul></ul></ul><ul><ul><ul><li>SSM/I 1987 - 2010 </li></ul></ul></ul><ul><li>Comparisons between for SSM/I and AMSR-E derived SWE datasets (2003-2010) conducted </li></ul>
  13. 13. <ul><li>Change of bias: DMSP-F13 results in higher snow mass (SWE) than AMSR-E, but DMSP-F17 gives a lower snow mass after summer 2009 </li></ul>2009-2010 DMSP-F17 2003 – 2008 DMSP-F13 AMSR-E vs. SSM/I evaluations (2003 - 2010)
  14. 14. AMSR-E vs. SSM/I trend (1980 - 2010)
  15. 15. SSMI, -8,2% trend for 30 years AMSR-E, -9.6% trend for 30 years AMSR-E vs. SSM/I trend (1980 - 2010)
  16. 16. Summary on SWE product <ul><li>Current long term datasets on Global scale: Monthly from 1978, daily from 2002 </li></ul><ul><ul><li>GlobSnow: Daily 30+ years ( … from launch of SMMR 1978) </li></ul></ul><ul><li>Thematic accuracy </li></ul><ul><ul><li>Current alternative algorithms </li></ul></ul><ul><ul><ul><li>Global scale 40mm – 200mm </li></ul></ul></ul><ul><ul><ul><li>Regional scale 20mm – 50mm (methods typically regionally adjusted) </li></ul></ul></ul><ul><ul><li>GlobSnow algorithm (Global scale): </li></ul></ul><ul><li>RMSE of 43.2 mm for Eurasia (diagnostic dataset; > 26 000 samples) </li></ul><ul><li>RMSE of 33.5 mm for Eurasia (for SWE < 150mm; >23 000 samples) </li></ul><ul><li>Error estimates (error bars) </li></ul><ul><ul><li>Current methods do not provide information on estimation error </li></ul></ul><ul><ul><li>GlobSnow SWE algorithm: Error estimates for each SWE estimate </li></ul></ul>
  17. 17. GlobSnow Snow Extent Dataset 28.07.11 Finnish Meteorological Institute <ul><li>SE retrieval using ERS-2 ATSR-2 and Envisat AATSR data </li></ul><ul><li>- Finnish Environment Institute’s SCAmod algorithm. </li></ul><ul><li>- Norwegian Linear Reflectance’ (NLR) fractional snow cover (FSC) algorithm; </li></ul><ul><li>- 15 years SE data record has been produced using optical imagery from ATSR-2 (1995-) and AATSR (2002-) on a hemispherical scale. </li></ul>yellow – clouds green – bare ground white – snow cover
  18. 18. Daily, weekly and monthly products April 2003 19 April 2003 10 April 2003 Optical data ~ 1km spatial resolution
  19. 19. Examples of monthly products, 2003 April 2003 May 2003 June 2003
  20. 20. 28.07.11 Finnish Meteorological Institute <ul><li>30+ year daily Snow Water Equivalent climate record (25 km resolution) </li></ul><ul><li>30+ year daily Snow Extent (PMW) climate record (25 km resolution) </li></ul><ul><li>15+ year daily Snow Extent (optical) climate record (1km resolution) </li></ul><ul><ul><li>Version 1.0 of low resolution SWE/SE (30 years) and high resolution SE (15 years) are available now </li></ul></ul><ul><ul><li>The extensive validation effort indicates a new level of accuracy for hemispherical scale SWE retrieval for the 30+ year evaluation </li></ul></ul><ul><ul><li>Long term trends indicate a clear decline in hemispherical snow mass </li></ul></ul><ul><li>The near-real-time GlobSnow processing system is on-going an operational demonstration phase (ESA GlobSnow -> Eumetsat H-SAF) </li></ul><ul><li>Products (freely available) and additional details: www.globsnow.info </li></ul>GlobSnow - Summary
  21. 21. SWE algorithm evaluations: Eurasia 1994-1997 <ul><li>Detailed analyses reported within GlobSnow project documentation </li></ul><ul><ul><li>- Accessible through the GlobSnow User www-pages </li></ul></ul>
  22. 22. SWE product & trend analyses Average SWE for March 1997 Mean snow mass for March (30 year trend)
  23. 23. SWE product & mountain hydrology <ul><li>Baseline SWE dataset does not include estimates for mountains </li></ul><ul><ul><li>Coarse resolution radiometer data not well suited for highly varied topography </li></ul></ul><ul><li>An on-going development effort to map mountains with GlobSnow SWE algorithm </li></ul><ul><li>1st “Prototype” mountain SWE dataset for 2008-2010 released: </li></ul><ul><li>www.globsnow.info/swe / </li></ul><ul><li>A more advanced version to be released by the end of summer 2011 </li></ul>

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