Parameterization of the freeze/thaw discriminant function algorithm using dense in-situ observation network data

Figures & data

Table 1. Details of networks.

Network	State	Pixels	Single stations	Row	Column	In-situ observation Points	Points for parameterization
CTP-SMTMN	China	3	3	1087	233	1749	1749
			3	1087	236
			5	1088	234
USA_NET	USA	3	2	304	192	5484	5400
			2	292	170
			2	123	86
FLUXNET	Canada	3	4	302	145	6409	5400
			3	300	145
			4	297	143
FMI	Finland	1	7	827	91	3430	1800
APEX	Alaska (USA)	4	8	127	102	8167	7200
			1	139	105
			1	119	118
			1	120	112

Figure 1. The distribution of the sites over the Northern Hemisphere.

Figure 2. Results of the data separated by Equations (4) and (5) at 6.925 GHz and the original function (colour online).

Figure 3. Results of the data separated by Equations (6) and (7) at 10.65 GHz and the original function (colour online).

Figure 4. Results of the data separated by Equations (8) and (9) at 18.7 GHz and the original function (colour online).

Table 2. Accuracy of the new discriminant algorithm function.

Frequency	Orbit	Frozen (%)	Thawed (%)	Mean (%)
6.9 GHz	Ascend	84.30	91.62	88.70
	Descend	84.14	92.02	88.87
	Mean (%)	83.98	92.49	89.09
10.65 GHz	Ascend	90.82	91.38	91.15
	Descend	91.18	90.56	90.81
	Mean (%)	88.91	92.47	91.02
18.7 GHz	Ascend	87.58	91.50	89.92
	Descend	86.46	92.48	90.06
	Mean (%)	86.46	92.48	90.06

Table 3. Accuracy of the original function.

18.7 GHz (original function)
	Frozen (%)	Thawed (%)	Mean (%)
Ascend	82.83	92.93	88.90
Descend	98.32	73.26	83.44
Mean (%)	90.63	83.16	86.17

Figure 5. Distribution of classification errors among different temperature ranges for the new algorithm (ascending).

Figure 6. Distribution of classification errors among different temperature ranges for the new algorithm (descending).

Figure 7. Comparison between SMAP FTP and the results of the new discriminant function at Cambridge-Bay (colour online).

Table 4. Comparison between discriminant results of the new function and SMAP FTP at SMAP core validations sites.

			Comparison analysis
Core site	Country	Location	Ascending orbit (%)	Descending orbit (%)
BERMS-OAS	Canada	53.63 N; 106.20 W	86.81	84.89
BERMS-OBS	Canada	53.99 N; 105.12 W	83.79	84.34
Kenaston	Canada	51.41 N; 106.50 W	79.67	75.82
Sodankyla	Finland	67.36 N; 26.64 E	77.75	75.55
Saariselka	Finland	68.38 N; 27.42 E	83.24	75.82
Imnavait	USA	68.62 N; 149.30 W	70.33	82.69
Baie-James	Canada	53.41 N; 75.013 W	83.52	79.40
Cambridge-Bay	Canada	69.15 N; 105.11 W	84.89	90.38
Mean			81.25	81.11