Zuhal Akyurek, A. Unal Sorman - H-SAF

Table 4.1. Contingency table for the snow cover product validation.
Snow Cover Product
Snow Presence
None
In-situ
Observation
Snow Presence a b
None c d
POD = a / (a+b) (4.1)
HR = (a+d) / (a+b+c+d) (4.2)
CSI = a / (a+b+c) (4.3)
Table 4.2. The comparison of the validation in terms of POD, HR, and CSI
Nov Dec Jan Feb Mar
ANSA-
25km
ANSA-
5km
ANSA-
25km
ANSA-
5km
POD (%) 80.00 90.33 93.57 97.44 98.78 81.97 88.59
HR (%) 73.78 84.44 86.13 90.75 93.31 68.37 74.27
CSI (%) 70.75 83.85 85.73 90.69 93.19 64.96 71.35
ii-Validation for Slovakia
Results of snow extent comparison are presented in Figures 4.3 and 4.4. The comparison was
performed on agreement and disagreement percentages on a daily basis (Figure 4.3). The
relationship of the percent agreement of the ANSA blended product and the MODIS and AMSR-
E input products alone for January 2008 are given in Figure 4.4. It is observed that the ANSA
blended snow products do not improve the mapping of snow cover extent relative to using either
MODIS or AMSR-E products alone for January 2008 in Slovakia. The Probability of detection
(POD), hit rate (HR) and critical success index (CSI) for January 2008 are presented in Table
4.3.
In the first five days in January 2008, the agreement of ANSA with field observations is around
80%. During this period blended snow products improve the snow mapping compared to MODIS
and AMSR-E products alone. In the second and third weeks of January due to high cloud
coverage, only contribution was observed from AMSR-E. The low spatial resolution of AMSR-
E, and shallow snow cover decrease the agreement percentages. Increased snow extent
comparison agreement was seen in the last five days of January. The difficulty of retrieving old
snow fell on the forest area was seen in the validation of blended snow products.
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