Detailed Reports on the Validationof the SGLI Products

5．Cryosphere Products

別1 - 15. Validation Results of Cryosphere Products
5.1 Evaluation Summary
Product

Snow and Ice
covered area (incl.
cloud detection)
Okhotsk sea-ice
distribution
Snow and ice
surfaceTemperature

Snow grain size ofshallow layer

ReleasethresholdStandard
accuracy

Targetaccuracy

10%

7%

10%

Status*1

Evaluation Methods

5%○Comparison with other satellite (MODIS)
data.

5%

3%

○

5K

2K1K

◎

100%

50%

30%

○*

Comparison with other satellite (MODIS)
data.
Comparison with in-situ observation (AWS
thermal radiometer data) other satellite(MODIS) data.
Comparison with climatology (relation
between snow surface temperature andsnow grain size) for the release threshold.
In addition, comparison with in-situ
observation data at Greenland for thestandard accuracy. *After the quality
control of SGLI data, the snow grain size
product has a potential to achieve thestandard accuracy.

*1 Symbols denote as follows; 〇: the release threshold achieved, ◎: the standard accuracy achieved, ☆: the target accuracy achieved.

別1 - 25. Validation Results of Cryosphere Products
5.2 (a) Snow and Ice covered area (SICE)

Validation Method:-Overall classification errors are evaluated comparing SGLI derived SICE with other satellite products. Relativeerrors are calculated by using the following equation.
𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 % =1
∑ 𝑆𝑆 𝑖𝑖 −𝑇𝑇 𝑖𝑖
𝑁𝑁1∑ 𝑇𝑇 𝑖𝑖
𝑁𝑁

2

∗ 100

(N: the number of data, S: SGLI obs., T: other satellite data.)

Validation data and condition etc.:-Snow covered area: MOD10C2 Snow Cover Extent ProductSea-ice covered area: MOD29E1D Sea Ice ProductSun-lit regions in the Northern Hemisphere are the target area for the evaluation of SICE accuracy. Eight-day
composite data of SICE were generated for SGLI and MODIS and then used for the comparison.

Validation period:-Mar. 14th to Aug. 20th 2018

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5. Validation Results of Cryosphere Products
5.2 (a) Snow and Ice covered area (SICE)*Snow Fraction > 10%

Validation Results: White: snow cover, Blue: sea-ice cover

SGLI

Relative Error = 9.39%
Bias = 744,064 km2

Jun.26th to Jul.3rd 2018

MODIS

Snow and sea-ice cover derived from SGLI and MODIS data

Scatter plot between MODIS and SGLI SICE

Estimated errors

Release threshold

Standard accuracy

Target accuracy

9.4%

10%

7%

5%

Release threshold is achieved

別1 - 45. Validation Results of Cryosphere Products
5.2 (b) Okhotsk sea-ice distribution (OKID)

Validation Method:-Overall classification errors are evaluated comparing SGLI derived sea-ice distribution with other satellite
products. Relative errors are calculated by using the following equation.
𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 % =1
∑ 𝑆𝑆 𝑖𝑖 −𝑇𝑇 𝑖𝑖𝑁𝑁1∑ 𝑇𝑇 𝑖𝑖
𝑁𝑁2∗ 100(N: the number of data, S: SGLI obs., T: other satellite data.)

Validation data and condition etc.:-Sea-ice covered area: MOD29E1D Sea Ice ProductSun-lit regions within the Okhotsk sea (43-63 deg.N, 135-163 deg.E) are the target area for the evaluation ofOKID accuracy. Eight-day composite data of OKID were generated for SGLI and MODIS and then used for thecomparison.

Validation period:-Mar. 14th to Aug. 20th 2018

MOD29E1D 1day composited
EASE grid dataRe-projection to Sinusoidal tile

8 days8day composite
Sea Ice Extent
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5. Validation Results of Cryosphere Products
5.2 (b) Okhotsk sea-ice distribution (OKID)*Snow Fraction > 10%

Validation Results:

Relative Error = 9.05%
Bias = 91,081km2

SGLI Reflectance

SGLI sea-ice (OKID)

Scatter plot between MODIS and SGLI SICE

Estimated errors

Release threshold

Standard accuracy

Target accuracy

9.1%

10%

5%

3%

Release threshold is achieved

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5. Validation Results of Cryosphere Products
5.2 (c) Snow and ice surface Temperature (SIST)

Validation Method:-Release threshold: Overall RMS errors are evaluated comparing SGLI derived SIST with thosefrom other satellite products.
Standard accuracy: RMS errors are evaluated comparing SGLI SIST with those from in-situ
thermal radiometer measurements on the ground.

Validation data and condition etc.:-Snow and ice surface temperature: MOD11A1 Land Surface Temperature Product (1 km tile)
Other satellite: Sun-lit regions in the Northern Hemisphere are the target area for theevaluation of SIST accuracy. Daily tile data of SGLI SIST were compared with that of MOD11A1product.
In-situ data: In-situ measured SISTs calculated from thermal radiometer data installed at thePROMICE Automatic Weather Stations (AWS) were used for the comparison with SGLI SIST. The
in-situ data acquired at within the time difference of 30 minutes from SGLI observations areused and compared with SGLI SISTs at the nearest neighbor of in-situ sites.

Validation period:-Jul. 1st to Sep. 30th 2018

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5. Validation Results of Cryosphere Products
5.2 (c) Snow and ice surface Temperature (SIST)

Validation Results:

MOD11A1RMSE = 2.6K
Bias = 0.25K[K]C2AB_SIST

For the release thresholdevaluation (vs. MODIS product)

For the standard accuracy evaluation(vs. AWS measurements)

Estimated errors

Release threshold

Standard accuracy

Target accuracy

Other sat.: 2.6K
In-situ: 1.5K

5K （vs. other sat.）

2K （vs. in-situ）

1K （vs. in-situ）

Release threshold and Standard accuracy are achieved
別1 - 8

5. Validation Results of Cryosphere Products
5.2 (d) Snow grain size of shallow layer (SGSL)

Validation Method:-Release threshold: Overall errors are evaluated comparing SGLI derived SGSL with climatological relationshipbetween snow grain size and snow surface temperature derived from the past observations.
Standard accuracy: RMS errors are evaluated comparing SGLI SGSL with those from in-situ data obtained bysnow pit works on the ground. Relative errors are calculated by using the following equation.
𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 % =1
∑ 𝑆𝑆 𝑖𝑖 −𝑇𝑇 𝑖𝑖
𝑁𝑁1∑ 𝑇𝑇 𝑖𝑖
𝑁𝑁2∗ 100(N: the number of data, S: SGLI obs., T: other satellite data.)

Validation data and condition etc.:-Climatology: Surface temperature dependence of snow grain size observed in the past study using GLI (Hori etal., 2006) was confirmed. For example, steep increase of snow grain size at the melting point of ice, andgradual increase of snow grain size with surface temperature at the lower temperature range below 0 ℃.
In-situ data: A sun-lit snow field (E-GRIP site) over the Greenland ice sheet is the target area for the evaluationof SGSL accuracy. In-situ data were obtained with instruments (IceCube/ HISSGraS) that measures specificsurface area (SSA) of snow particles. The in-situ derived SSAs acquired within the time difference of 10
minutes from SGLI observations were converted to optically equivalent sphere grain sizes and then comparedwith SGLI SGSL (250 m resolution) at the nearest neighbor of the in-situ site.

Validation period:-Jul. 2nd to 16th 2018

Reference: Hori, M., Aoki, Te., Stamnes, K., Li, W. (2007). ADEOS-II/GLI snow/ice products - Part III: Retrieved results, Remote Sensing of Environment,111, 291-336.

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5. Validation Results of Cryosphere Products
5.2 (d) Snow grain size of shallow layer (SGSL)

Field experiments at EGRIP, Greenland in 2018

Grain size (μm)

Grain size ( μm)

Validation Results:

GLIHori et al. (2006)

EGRIP
Cloud contaminations
were confirmed onsky-camera images

SGLI
Surface temp.(K)

SGLI-derived snow grain size on Jul. 13th 2018

SGLI-derived SGSLs are consistent with
Climatological relationship between those obtained at the Greenland ice
snow surface temperature and snow sheet (EGRIP) in July 2018.
grain size

RMSE = 85.97%(33.4% if the cloud effects are eliminated.)

Estimated errors

Release threshold

Standard accuracy

Target accuracy

86% (33%*)

100%

50%

30%

Release threshold is achieved(*if the cloud effects are eliminated by quality assurance process in next updates, the standard accuracy can be achieved.)

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