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Table 3: Number of equivalent Snow-Only coincident sites (n=88)
12.5k
25k
Swath
SWE Calculation SSM/I
55
AMSR-E AMSR-E AMSR-E
Core_SWE
(63%)
50
42 (48%) 20 (23%) 56 (64%)
Fractional_Core_SWE (57%)
58
29 (33%) 11 (13%) 49 (56%)
Derived_SWE
(66%)
45
32 (36%) 15 (17%) 54 (61%)
Fractional_Derived_SWE (51%) 24 (27%) 7 (8%) 45 (51%)
Table 4: Number of equivalent Actual-Conditions coincident sites (n=88)
SWE Calculation SSM/I
51
Core_SWE
(58%)
44
Fractional_Core_SWE (50%)
45
Derived_SWE
(51%)
33
Fractional_Derived_SWE (38%)
12.5k
AMSR-E
34
(39%)
27
(31%)
26
(30%)
23
(26%)
304
25k
AMSR-E
13
(15%)
10
(11%)
9
(10%)
7
(8%)
Swath
AMSR-E
52
(59%)
45
(51%)
49
(56%)
40
(45%)
By weighting the in-situ SWE values by the percentage of snow cover found at the sites (i.e.
reading down each column) the agreement with the remote sensing estimates decreases by an
average of approximately 10% in the Snow-Only data set, and by an average of approximately 7%
in the Actual-Conditions data set. Further, the remote sensing SWE algorithm generally had a
higher level of agreement with Core_SWE measurements than with Derived_SWE values.
Therefore, for a patchy snow cover, it appears that the MSC SWE algorithm had the closest
agreement with ground SWE measurements based only on the core samples
Further analyses using only these Core_SWE measurements found that, on average, the remote
sensing algorithm tended to overestimate the patchy in-situ SWE measurements in all cases (Table
5). This was not surprising since the remote sensing algorithm was originally derived for a
complete snow cover.
Table 5: Mean differences in SWE values between remote sensing estimates and in-situ measurements
(for core samples only)
12.5k
25k
Swath
SSM/I AMSR-E AMSR-E AMSR-E
Snow-Only Core_SWE 4.8 17.7 32.1 5.4
Actual-Conditions Core_SWE 8.7 21.6 35.9 9.3
We also wanted to examine the effect that varying land covers had on the spaceborne SWE
estimates. The ranges in ground SWE measurements were very high, particularly when the
sampling sites included shelter belts and fallow fields, which were found to have drastically
different snow conditions than stubble fields and pastures. Table 6 shows that there is little
difference in the mean SWE values representative of stubble fields (26.1 mm) and pastures (23.0
mm), but great disparity between these values and fallow fields (1.7 mm) and shelter belts (94.8
mm).