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Bridger Wilderness Area Trends Analysis
The tables and figures below show the trends analysis results for 20% worst, middle 60% and 20% best days at BRID1 based on light extinction coefficient data from 1994 to 2003. No significant trend is observed for aerosol light extinction coefficients in 20% worst days. The nitrate extinction increased significantly in the worst days and in middle 60% days. Significant decrease trend is found for aerosol light extinction coefficients in 20% best days, which is caused mainly by decrease in sulfate, nitrate, and CM light extinction.

Table 1. Number of valid measurements used in the trends analysis 
Site Year StartDate EndDate NoMeas
BRID1 1994 1/1/1994 12/31/1994 96
BRID1 1995 1/4/1995 12/23/1995 96
BRID1 1996 1/10/1996 12/28/1996 94
BRID1 1997 1/1/1997 12/27/1997 97
BRID1 1998 1/3/1998 12/30/1998 92
BRID1 1999 1/2/1999 12/29/1999 83
BRID1 2000 1/1/2000 12/29/2000 106
BRID1 2001 1/1/2001 12/30/2001 112
BRID1 2002 1/5/2002 12/31/2002 106
BRID1 2003 1/3/2003 12/29/2003 116
Table 2. Trends analysis for 20% worst visibility days
Site Year Bep (1/Mm) Sulfate_Ext (1/Mm) Nitrate_Ext (1/Mm) OMC_Ext (1/Mm) LAC_Ext (1/Mm) Soil_Ext (1/Mm) CM_Ext (1/Mm)
BRID1 1994 20.41 6.67 0.71 7.89 1.67 1.09 2.38
BRID1 1995 16.11 5.73 0.70 5.20 1.50 0.57 2.40
BRID1 1996 25.01 6.70 1.23 10.08 2.79 0.93 3.28
BRID1 1997 17.43 7.10 1.20 3.82 1.27 0.59 3.44
BRID1 1998 21.83 7.03 1.26 8.80 1.81 0.90 2.03
BRID1 1999 21.68 5.80 1.14 8.26 1.76 1.02 3.70
BRID1 2000 21.60 5.32 1.42 9.00 2.51 0.90 2.43
BRID1 2001 21.45 6.95 1.65 6.92 1.53 1.45 2.95
BRID1 2002 22.74 5.39 2.00 10.00 2.11 1.05 2.20
BRID1 2003 22.66 5.47 1.07 11.20 2.09 0.72 2.11
               
Slope (1/Mm/Year)   0.255 -0.082 0.112 0.368 0.055 0.018 -0.029
S-Value   13 -11 21 17 9 7 -5
P-Value   0.146 0.190 0.036 0.078 0.242 0.300 0.364

Table 3. Trends analysis for middle 60% visibility days
 
Site Year Bep (1/Mm) Sulfate_Ext (1/Mm) Nitrate_Ext (1/Mm) OMC_Ext (1/Mm) LAC_Ext (1/Mm) Soil_Ext (1/Mm) CM_Ext (1/Mm)
BRID1 1994 10.78 3.89 0.78 3.29 0.70 0.43 1.70
BRID1 1995 9.53 3.74 0.77 2.40 0.99 0.29 1.34
BRID1 1996 11.26 3.98 0.72 3.41 1.15 0.46 1.54
BRID1 1997 9.69 3.76 0.74 2.47 0.75 0.25 1.70
BRID1 1998 12.22 4.48 0.75 4.02 1.02 0.35 1.59
BRID1 1999 11.81 3.66 0.82 3.79 1.09 0.49 1.97
BRID1 2000 10.01 3.98 0.99 2.95 0.89 0.29 0.91
BRID1 2001 10.57 4.31 1.09 2.66 0.94 0.47 1.10
BRID1 2002 9.94 3.63 1.37 2.47 1.03 0.45 0.99
BRID1 2003 9.36 3.22 1.14 2.89 0.87 0.36 0.88
               
Slope (1/Mm/Year)   -0.105 -0.033 0.053 -0.045 0.006 0.003 -0.088
S-Value   -9 -11 29 -5 3 7 -19
P-Value   0.242 0.190 0.005 0.364 0.431 0.300 0.054

Table 4. Trends analysis for 20% best visibility days
Site Year Bep (1/Mm) Sulfate_Ext (1/Mm) Nitrate_Ext (1/Mm) OMC_Ext (1/Mm) LAC_Ext (1/Mm) Soil_Ext (1/Mm) CM_Ext (1/Mm)
BRID1 1994 5.24 2.35 0.88 0.94 0.36 0.11 0.59
BRID1 1995 5.07 1.80 0.88 1.28 0.39 0.11 0.60
BRID1 1996 4.55 2.00 0.64 0.96 0.47 0.09 0.39
BRID1 1997 4.91 1.96 0.46 1.37 0.29 0.12 0.71
BRID1 1998 5.78 2.20 0.55 1.33 0.44 0.08 1.18
BRID1 1999 5.14 2.10 0.43 1.55 0.41 0.13 0.53
BRID1 2000 4.35 2.17 0.42 1.05 0.38 0.09 0.25
BRID1 2001 4.40 1.93 0.52 0.79 0.70 0.12 0.34
BRID1 2002 3.73 1.70 0.50 0.79 0.41 0.08 0.24
BRID1 2003 3.37 1.43 0.41 0.91 0.32 0.09 0.20
               
Slope (1/Mm/Year)   -0.187 -0.051 -0.047 -0.027 0.002 -0.001 -0.044
S-Value   -27 -19 -29 -9 3 -3 -25
P-Value   0.008 0.054 0.005 0.242 0.431 0.431 0.014

Page last updated 30 March 2005