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Great Sand Dunes Wilderness Area Trends Analysis
The tables and figures below show the trends analysis results for 20% worst, middle 60% and 20% best days at GRSA1 based on light extinction coefficient data from 1994 to 2003. Overall, there are no significant  trends in aerosol light extinction in 20% worst days, middle 60% days, and  20% best days. But significant increase trends are found for nitrate and soil extinction in the worst days. Very high CM extinctions are observed in worst days of 1994, 2002 and 2000, which are believed to be associated with local dust events. 

Table 1. Number of valid measurements used in the trends analysis
Site Year StartDate EndDate NoMeas
GRSA1 1994 1/1/1994 12/31/1994 98
GRSA1 1995 1/4/1995 12/30/1995 102
GRSA1 1996 1/3/1996 12/28/1996 100
GRSA1 1997 1/1/1997 12/31/1997 99
GRSA1 1998 1/3/1998 12/30/1998 97
GRSA1 1999 1/2/1999 12/29/1999 101
GRSA1 2000 1/1/2000 12/29/2000 99
GRSA1 2001 1/1/2001 12/24/2001 109
GRSA1 2002 1/2/2002 12/31/2002 105
GRSA1 2003 1/3/2003 12/29/2003 118
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)
GRSA1 1994 36.19 7.91 1.03 6.29 1.47 2.23 17.26
GRSA1 1995 21.63 9.70 1.11 5.05 1.72 1.13 2.92
GRSA1 1996 23.69 7.68 0.90 6.63 1.81 2.11 4.56
GRSA1 1997 23.58 9.60 2.46 4.05 1.44 1.63 4.40
GRSA1 1998 27.00 11.01 1.69 7.47 2.02 1.40 3.41
GRSA1 1999 24.56 7.06 1.60 5.85 1.83 1.80 6.42
GRSA1 2000 32.93 7.10 1.85 9.55 2.25 2.75 9.43
GRSA1 2001 24.59 8.24 1.93 4.98 1.25 2.37 5.82
GRSA1 2002 30.14 6.12 2.65 5.74 1.34 2.81 11.48
GRSA1 2003 31.25 7.15 1.77 10.33 2.16 3.15 6.69
               
Slope (1/Mm/Year)   0.786 -0.206 0.124 0.259 0.050 0.166 0.434
S-Value   15 -15 23 9 7 25 13
P-Value   0.108 0.108 0.023 0.242 0.300 0.014 0.146

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)
GRSA1 1994 13.73 5.36 1.10 3.14 1.07 0.54 2.51
GRSA1 1995 12.63 4.57 1.09 2.85 1.22 0.92 1.98
GRSA1 1996 12.64 4.74 0.76 2.83 1.13 0.96 2.22
GRSA1 1997 13.59 5.63 1.09 3.10 0.97 0.61 2.19
GRSA1 1998 15.49 6.00 1.26 4.51 1.17 0.62 1.93
GRSA1 1999 13.25 4.48 0.75 3.73 1.11 0.75 2.43
GRSA1 2000 15.48 5.31 1.09 3.92 1.24 0.90 3.02
GRSA1 2001 14.61 5.52 1.14 3.08 0.99 0.79 3.10
GRSA1 2002 14.61 4.69 1.61 3.50 1.06 1.15 2.59
GRSA1 2003 13.97 4.59 1.17 3.86 1.00 0.94 2.41
               
Slope (1/Mm/Year)   0.167 -0.022 0.014 0.093 -0.012 0.038 0.071
S-Value   13 -5 15 13 -9 19 13
P-Value   0.146 0.364 0.108 0.146 0.242 0.054 0.146

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)
GRSA1 1994 7.56 2.59 1.21 1.85 0.69 0.22 1.01
GRSA1 1995 6.49 1.97 1.15 1.51 0.71 0.36 0.80
GRSA1 1996 6.28 2.03 0.78 1.54 0.58 0.37 0.97
GRSA1 1997 6.94 2.81 0.57 1.66 0.73 0.43 0.74
GRSA1 1998 9.60 3.48 0.84 2.61 0.81 0.46 1.40
GRSA1 1999 7.16 2.23 0.54 1.85 0.81 0.49 1.22
GRSA1 2000 7.25 2.76 0.66 1.70 0.69 0.30 1.14
GRSA1 2001 7.32 2.70 0.62 1.61 0.66 0.44 1.29
GRSA1 2002 7.94 2.61 0.96 1.99 0.70 0.36 1.31
GRSA1 2003 7.19 2.01 0.58 2.33 0.55 0.45 1.27
               
Slope (1/Mm/Year)   0.093 0.003 -0.048 0.046 -0.005 0.014 0.043
S-Value   13 1 -17 17 -7 17 19
P-Value   0.146 0.500 0.078 0.078 0.300 0.078 0.054

Page last updated 30 March 2005