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ESA GlobSnow - project overview

GCW 1st Implementation meetingGeneve, 23 Nov. 2011

K. Luojus & J. Pulliainen (FMI)+ R. Solberg (NR)

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• ESA-GlobSnow project: Production of novel hemispherical snow extent (SE) and snow water equivalent (SWE) climate data records.

• Generation of long time-series employing FMI supercomputing facilities at Helsinki (daily, weekly and monthly maps of SE and SWE for northern hemisphere)

• Near-real-time GlobSnow processing system and data archives located in Sodankylä.

• Consortium members: Finnish Meteorological Institute (FMI) with ENVEO IT GmbH (Austria), GAMMA Remote Sensing (Switzerland), Norwegian Computing Center, Finnish Environment Institute (SYKE), and Environment Canada (EC).

• Details and products available at www.globsnow.info

ESA GlobSnow

30 year-long CDR time-series on snow conditionsof Northern Hemisphere (ESA-GlobSnow SWE)

• First time reliable daily spatial information on SWE (snow cover):- Snow Water Equivalent (SWE) - Snow Extent and melt (+grain size)

- 25 km resolution (EASE-grid)- Time-series for 1979-2011

• Passive microwave radiometer data combined with ground-based synoptic snow observations- Variational data-assimilation

• Available at open data archive (www.globsnow.info)

• Demonstration of NRT processing started on October 2010

• Greenland, glaciers & mountains masked out

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SWE algorithm selection & validation

SWE estimates from 5 algorithms evaluated for Eurasia (1994-1997)• FMI Assimilation algorithm (Pulliainen 2006)• EC SWE suite (Goodison, Walker, Goita, Derksen et al. 1993-2009)• Chang et al. 1987 (original channel difference algorithm)• SPD-algorithm (Asbacher 1989)• Armstrong and Brodzik 2001-algorithm (Improved channel difference)

SWE algorithm evaluation for 09/1994 and 12/1997 (SSM/I data)

• Evaluations for North America and Finland were carried out in addition to the analyses for Eurasia

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Validation data – INTAS SSCONE data

INTAS SSCONE data (from the former USSR and Russia)• There are 1294 snow path stations with data from the USSR

• Manual (0.5 – 2km) transects measuring snow depth• There were 450 path stations with data for 1994-1997

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Overall performance for SWE algorithmsEurasia 09/1994 – 12/1997

Reference data: independent snow transects

Name RMSE bias Corr.coeff Unbiased RMSE Samples

FMI algorithm – used for GlobSnow) 43.2 mm -3.1 mm 0.611 43.1 mm 26063

EC algorithm 67.6 mm -28.2 mm 0.210 61.5 mm 18109

Chang et al. 1987 (asc node)Chang et al. 1987 (desc node)

71.6 mm70.7 mm

-8.4 mm1.6 mm

0.0110.029

71.1 mm70.8 mm

2672627521

SPD algorithm (asc node)SPD algorithm (desc node)

67.1 mm63.9 mm

-12.7 mm-3.1 mm

0.0520.121

65.9 mm63.9 mm

2955929451

Armstrong et al. 2001 (asc node)Armstrong et al. 2001 (desc node)

72.3 mm73.7 mm

-44.1 mm-42.9 mm

0.0440.029

57.3 mm59.9 mm

2179624791

SWE retrieval (data assimilation vs. channel diff.)• Density scatterplot (assimilated vs. satellite only SWE)• Ground truth data is INTAS SCCONE SWE transect data

F 17SSM/I

F 13SSM/I

F 11SSM/I

F 8SSM/ISMMR

F 13SSM/I

F 11SSM/I

F 8SSM/ISMMR

F 17SSM/I

• RMS error and retrieval bias calculated independently for each year 1980-2009• Reference data: snow transects from Russia (INTAS-SCCONE)

Consistency of SWE retrieval 1980 - 2009

SWE<150 mm

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GlobSnow SE Dataset

• SE retrieval using ERS-2 ATSR-2 and Envisat AATSR data

- Finnish Environment Institute’s SCAmod algorithm.

- Norwegian Linear Reflectance’ (NLR) fractional snow cover (FSC) algorithm;

- 15 years SE data record has been produced using optical imagery from ATSR-2 (1995-) and AATSR (2002-) on a hemispherical scale. yellow – clouds

green – bare groundwhite – snow cover

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Daily, weekly and monthly products

April 2003

19 April 2003

10 April 2003

Optical data ~ 1km spatial resolution

March 2010

1 March 2010

3 March 2010

Examples of monthly products, 2010

April 2003

May 2003

June 2003

Examples of monthly products, 2010

Apr 4 2011

Example:Trend analysisusingSWE product

Apr 4 2011

Snow clearance date • Example for year

2008• Time series of 30

years processed and distributed along the SWE product

Frost tube measurements in Finland• Operated by Finnish environmental institute• Default configuration: Three frost tubes in three

different locations: Open area, Forest and Bog site.

• Manually recorder three times per month (usually 6th, 16th and 26th). During freezing and thawing 5 times.

• Almost 40 manually recorded frost tube “stations”.

• In Sodankylä, automatic temperature profile measurements installed next to frost tubes for comparison.

Frost tube locations

• Typically three tubes in three main land classes: forest, bog, open

Forest

Bog

Open

Two winter time-series: ELBARA-II and frost/snow

Inc. angle: 50°

Snow Snow

Frost Frost

Hemispherical trend of snow extent (PMW ~25km)

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Hemispherical trend of snow mass

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Production of novel global snow extent (SE) and snow water equivalent (SWE) climate data records (15 and 30 years of snow cover information)

- coarse resolution (25km) SWE and SE for 1979 – 2011- medium resolution (1km) SE for 1995 – 2011

Additionally, near-real-time GlobSnow processing demonstration is ongoing with open data access (started on October 2010)

Additional information and all GlobSnow products available at www.globsnow.info

GlobSnow - Summary

Any Questions ?(GlobSnow-handouts available…)

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