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Gila Wilderness Area Trends Analysis
The tables and figures below show the trends analysis results for 20% worst, middle 60% and 20% best days at GICL1 based on light extinction coefficient data from 1994 to 2003. Overall, there is no significant trend in aerosol light extinction in 20% worst days. But a peak is observed in 2000 caused by big OC and EC concentrations, which is believed to be associated with forest fires. There is a statistically significant increase in nitrate and soil extinction, and a decrease in sulfate and CM extinction in 20% worst days. Significant decrease trend is found for aerosol light extinction coefficients in both middle 60% and 20% best days, which is caused mainly by significantly decrease in sulfate and LAC light extinction. Nitrate extinction also significantly decreased in the 20% best days.

Table 1. Number of valid measurements used in the trends analysis
Site Year StartDate EndDate NoMeas
GICL1 1994 4/13/1994 12/28/1994 73
GICL1 1995 1/4/1995 12/30/1995 95
GICL1 1996 1/3/1996 12/25/1996 98
GICL1 1997 1/1/1997 12/31/1997 99
GICL1 1998 1/3/1998 12/30/1998 97
GICL1 1999 1/2/1999 11/27/1999 83
GICL1 2000 3/8/2000 12/29/2000 72
GICL1 2001 1/1/2001 12/30/2001 103
GICL1 2002 1/5/2002 12/31/2002 118
GICL1 2003 1/3/2003 12/29/2003 98
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)
GICL1 1994 26.05 9.82 0.64 7.88 1.93 1.12 4.66
GICL1 1995 36.16 12.88 0.65 13.71 4.45 0.75 3.73
GICL1 1996 38.85 10.17 0.84 16.48 5.00 0.89 5.47
GICL1 1997 37.69 9.63 0.78 16.75 5.34 0.88 4.30
GICL1 1998 32.30 15.09 0.68 9.44 3.01 0.72 3.37
GICL1 1999 23.89 8.93 0.66 6.92 2.02 0.99 4.36
GICL1 2000 55.20 9.57 1.28 29.57 9.70 1.19 3.89
GICL1 2001 25.72 9.32 0.67 9.02 2.38 1.44 2.90
GICL1 2002 32.39 7.57 1.14 15.31 3.40 1.67 3.31
GICL1 2003 34.31 7.74 1.30 16.67 4.25 1.42 2.93
               
Slope (1/Mm/Year)   -0.046 -0.347 0.064 0.370 0.096 0.084 -0.192
S-Value   -1 -27 23 9 5 23 -25
P-Value   0.500 0.008 0.023 0.242 0.364 0.023 0.014

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)
GICL1 1994 16.02 6.74 0.59 4.23 1.34 0.64 2.47
GICL1 1995 16.12 6.30 0.62 4.33 1.76 0.70 2.41
GICL1 1996 14.63 5.94 0.52 3.42 1.39 0.69 2.67
GICL1 1997 16.56 7.26 0.59 3.81 1.39 0.52 2.99
GICL1 1998 15.73 5.88 0.61 3.94 1.63 0.64 3.03
GICL1 1999 15.33 5.42 0.75 4.11 1.42 0.72 2.91
GICL1 2000 15.62 5.07 0.87 5.31 1.37 0.92 2.08
GICL1 2001 13.17 5.29 0.70 3.84 1.24 0.75 1.35
GICL1 2002 12.62 4.92 0.73 3.41 1.07 0.85 1.63
GICL1 2003 12.03 4.48 0.60 3.70 1.10 0.66 1.49
               
Slope (1/Mm/Year)   -0.444 -0.228 0.017 -0.056 -0.050 0.015 -0.119
S-Value   -29 -37 15 -11 -23 15 -17
P-Value   0.005 0.000 0.108 0.190 0.023 0.108 0.078

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)
GICL1 1994 8.99 3.44 0.69 2.09 0.89 0.23 1.66
GICL1 1995 7.82 2.87 0.69 1.97 1.02 0.19 1.08
GICL1 1996 6.65 2.49 0.62 1.32 0.74 0.33 1.16
GICL1 1997 7.14 2.87 0.34 1.45 0.82 0.17 1.50
GICL1 1998 7.85 2.97 0.37 1.84 0.88 0.21 1.58
GICL1 1999 7.56 2.39 0.39 1.68 0.91 0.35 1.84
GICL1 2000 6.67 2.56 0.49 2.13 0.87 0.20 0.42
GICL1 2001 6.12 2.58 0.42 1.56 0.69 0.22 0.65
GICL1 2002 5.49 2.15 0.32 1.67 0.76 0.21 0.37
GICL1 2003 4.84 1.73 0.22 1.69 0.59 0.16 0.45
               
Slope (1/Mm/Year)   -0.384 -0.131 -0.046 -0.030 -0.029 -0.004 -0.102
S-Value   -31 -25 -25 -3 -21 -7 -17
P-Value   0.002 0.014 0.014 0.431 0.036 0.300 0.078

Page last updated 30 March 2005