CLPX Field Experiment Plan - December 7, 2001

Table 16. Matrix of corrections for airborne gamma snow water equivalent measurements (cm), showing uncertainty resulting from soil moisture estimates. To determine the SWE correction for inaccurate estimates of background soil moisture, find the value corresponding to the estimated value (M0) on the Y-axis, and the correct value (M0') on the X-axis. For example, if SWE was calculated using a M0 of 20%, but M0' was actually 30%, the SWE correction is +1.5 cm. To determine the SWE correction for inaccurate estimates of subnivean soil moisture, find the value corresponding to the estimated value (M) on the X-axis, and the correct value (M') on the Y-axis. For example, if SWE was calculated using a M of 25%, but M' was actually 30%, the SWE correction is -0.7 cm. The total SWE correction is the sum of the two correction terms. The matrix illustrates that a 5% error in either soil moisture term results in an absolute error in SWE of between 0.5 cm and 0.9 cm. In general the following relationships apply: 1) if M0 is overestimated and M is underestimated, SWE is overestimated and both correction terms are negative; 2) if M0 is under-estimated and M is over-estimated, SWE is under-estimated and both correction terms are positive; 3) if M0 and M are both under- or over-estimated, the correction terms will be of opposite sign.
 
Estimated
Background
SM
(M0)
 
 
 

Correct
Subnivean
SM
(M')

 100 -12.8 -11.9 -11.0 -10.2 -9.4 -8.6 -7.9 -7.2 -6.5 -5.9 -5.2 -4.6 -4.0 -3.5 -2.9 -2.4 -1.9 -1.4 -0.9 -0.5 0
95 -12.3 -11.4 -10.5 -9.7 -8.9 -8.1 -7.4 -6.7 -6.0 -5.4 -4.8 -4.2 -3.6 -3.0 -2.5 -2.0 -1.4 -1.0 -0.5 0 0.5
90 -11.9 -10.9 -10.1 -9.2 -8.4 -7.7 -6.9 -6.2 -5.6 -4.9 -4.3 -3.7 -3.1 -2.6 -2.0 -1.5 -1.0 -0.5 0 0.5 0.9
85 -11.4 -10.5 -9.6 -8.7 -8.0 -7.2 -6.5 -5.8 -5.1 -4.4 -3.8 -3.2 -2.6 -2.1 -1.5 -1.0 -0.5 0 0.5 1.0 1.4
80 -10.9 -10.0 -9.1 -8.3 -7.5 -6.7 -6.0 -5.3 -4.6 -3.9 -3.3 -2.7 -2.1 -1.6 -1.0 -0.5 0 0.5 1.0 1.4 1.9
75 -10.4 -9.5 -8.6 -7.7 -6.9 -6.2 -5.5 -4.8 -4.1 -3.4 -2.8 -2.2 -1.6 -1.1 -0.5 0 0.5 1.0 1.5 2.0 2.4
70 -9.9 -8.9 -8.0 -7.2 -6.4 -5.7 -4.9 -4.2 -3.6 -2.9 -2.3 -1.7 -1.1 -0.5 0 0.5 1.0 1.5 2.0 2.5 2.9
65 -9.3 -8.4 -7.5 -6.7 -5.9 -5.1 -4.4 -3.7 -3.0 -2.4 -1.7 -1.1 -0.6 0 0.5 1.1 1.6 2.1 2.6 3.0 3.5
60 -8.7 -7.8 -6.9 -6.1 -5.3 -4.6 -3.8 -3.1 -2.5 -1.8 -1.2 -0.6 0 0.6 1.1 1.6 2.1 2.6 3.1 3.6 4.0
55 -8.2 -7.2 -6.4 -5.5 -4.7 -4.0 -3.2 -2.5 -1.9 -1.2 -0.6 0 0.6 1.1 1.7 2.2 2.7 3.2 3.7 4.2 4.6
50 -7.6 -6.6 -5.8 -4.9 -4.1 -3.4 -2.6 -1.9 -1.3 -0.6 0 0.6 1.2 1.7 2.3 2.8 3.3 3.8 4.3 4.8 5.2
45 -6.9 -6.0 -5.1 -4.3 -3.5 -2.7 -2.0 -1.3 -0.6 0 0.6 1.2 1.8 2.4 2.9 3.4 3.9 4.4 4.9 5.4 5.9
40 -6.3 -5.4 -4.5 -3.7 -2.9 -2.1 -1.4 -0.7 0 0.6 1.3 1.9 2.5 3.0 3.6 4.1 4.6 5.1 5.6 6.0 6.5
35 -5.6 -4.7 -3.8 -3.0 -2.2 -1.4 -0.7 0 0.7 1.3 1.9 2.5 3.1 3.7 4.2 4.8 5.3 5.8 6.2 6.7 7.2
30 -4.9 -4.0 -3.1 -2.3 -1.5 -0.7 0 0.7 1.4 2.0 2.6 3.2 3.8 4.4 4.9 5.5 6.0 6.5 6.9 7.4 7.9
25 -4.2 -3.3 -2.4 -1.6 -0.8 0 0.7 1.4 2.1 2.7 3.4 4.0 4.6 5.1 5.7 6.2 6.7 7.2 7.7 8.1 8.6
20 -3.4 -2.5 -1.6 -0.8 0 0.8 1.5 2.2 2.9 3.5 4.1 4.7 5.3 5.9 6.4 6.9 7.5 8.0 8.4 8.9 9.4
15 -2.6 -1.7 -0.8 0 0.8 1.6 2.3 3.0 3.7 4.3 4.9 5.5 6.1 6.7 7.2 7.7 8.3 8.7 9.2 9.7 10.2
10 -1.8 -0.9 0 0.8 1.6 2.4 3.1 3.8 4.5 5.1 5.8 6.4 6.9 7.5 8.0 8.6 9.1 9.6 10.1 10.5 11.0
5 -0.9 0 0.9 1.7 2.5 3.3 4.0 4.7 5.4 6.0 6.6 7.2 7.8 8.4 8.9 9.5 10.0 10.5 10.9 11.4 11.9
0 0 0.9 1.8 2.6 3.4 4.2 4.9 5.6 6.3 6.9 7.6 8.2 8.7 9.3 9.9 10.4 10.9 11.4 11.9 12.3 12.8
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Estimated Subnivean Soil Moisture (M)                          Correct Background Soil Moisture (M0')