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Bryce Canyon National Park Trends Analysis
The tables and figures below show the trends analysis results for 20% worst, middle 60% and 20% best days at BRCA1 based on light extinction coefficient data from 1994 to 2003. Aerosol light extinction coefficients in 20% worst days increased by ~0.4 (1/Mm)/Year and the trend is close to significant (P-value = 0.08), which is due to the increase in nitrate and fine soil extinction. At the same time, sulfate extinction decreased significantly in the worst days. Overall, there is no significant trend in aerosol light extinction in middle 60% days. But there is significant increase in nitrate and decrease in LAC light extinction. Significant decrease trend is found for aerosol light extinction coefficients in 20% best days, which is caused mainly by decrease in nitrate, soil and CM light extinction.

Table 1. Number of valid measurements used in the trends analysis 
Site Year StartDate EndDate NoMeas
BRCA1 1994 1/8/1994 12/31/1994 90
BRCA1 1995 1/4/1995 12/30/1995 95
BRCA1 1996 1/3/1996 12/28/1996 100
BRCA1 1997 1/1/1997 12/31/1997 103
BRCA1 1998 1/3/1998 12/26/1998 98
BRCA1 1999 1/2/1999 12/29/1999 81
BRCA1 2000 1/1/2000 12/29/2000 107
BRCA1 2001 1/1/2001 12/30/2001 91
BRCA1 2002 1/2/2002 12/31/2002 104
BRCA1 2003 1/3/2003 12/29/2003 110
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)
BRCA1 1994 21.24 7.78 1.15 5.74 1.97 0.84 3.75
BRCA1 1995 19.76 8.70 1.14 4.87 1.87 0.83 2.36
BRCA1 1996 26.40 5.77 1.33 10.61 4.17 0.97 3.55
BRCA1 1997 24.59 6.71 1.90 9.59 2.57 0.89 2.93
BRCA1 1998 21.39 7.08 1.87 7.13 1.75 1.02 2.53
BRCA1 1999 22.43 5.27 2.40 8.17 2.08 0.84 3.67
BRCA1 2000 21.68 7.35 2.72 5.84 2.14 1.03 2.59
BRCA1 2001 23.16 7.32 3.64 6.16 1.91 1.28 2.84
BRCA1 2002 31.14 5.01 1.61 14.46 2.78 1.47 5.80
BRCA1 2003 24.17 5.11 1.93 9.20 2.42 1.13 4.38
               
Slope (1/Mm/Year)   0.436 -0.229 0.249 0.325 0.043 0.044 0.081
S-Value   17 -19 25 11 7 29 11
P-Value   0.078 0.054 0.014 0.190 0.300 0.005 0.190

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)
BRCA1 1994 13.21 5.01 1.15 3.10 1.06 0.63 2.26
BRCA1 1995 11.72 4.17 1.20 2.71 1.47 0.56 1.61
BRCA1 1996 12.44 3.96 1.20 3.27 1.38 0.59 2.03
BRCA1 1997 11.17 4.13 1.13 2.66 1.09 0.41 1.77
BRCA1 1998 11.84 4.05 1.23 3.42 1.10 0.41 1.64
BRCA1 1999 12.64 4.29 1.40 3.05 1.04 0.52 2.33
BRCA1 2000 11.32 4.15 1.41 2.74 1.08 0.50 1.43
BRCA1 2001 12.21 4.74 1.26 2.89 1.13 0.56 1.64
BRCA1 2002 12.05 3.66 1.97 2.75 0.84 0.69 2.14
BRCA1 2003 10.59 3.30 1.43 2.92 1.00 0.50 1.44
               
Slope (1/Mm/Year)   -0.142 -0.094 0.040 -0.020 -0.030 -0.004 -0.039
S-Value   -13 -15 33 -3 -19 -3 -9
P-Value   0.146 0.108 0.001 0.431 0.054 0.431 0.242

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)
BRCA1 1994 6.60 2.31 1.49 1.32 0.43 0.19 0.86
BRCA1 1995 5.94 1.84 1.45 1.12 0.52 0.17 0.83
BRCA1 1996 5.24 1.58 1.06 1.17 0.68 0.15 0.61
BRCA1 1997 5.50 2.09 0.69 1.25 0.60 0.18 0.68
BRCA1 1998 5.26 1.84 0.69 1.12 0.45 0.17 0.99
BRCA1 1999 5.72 1.93 0.66 1.48 0.51 0.17 0.97
BRCA1 2000 4.93 1.81 0.72 1.30 0.48 0.14 0.49
BRCA1 2001 5.22 2.13 0.86 0.88 0.49 0.18 0.68
BRCA1 2002 4.53 1.70 0.84 1.03 0.43 0.11 0.42
BRCA1 2003 4.15 1.32 0.57 1.26 0.38 0.13 0.49
               
Slope (1/Mm/Year)   -0.204 -0.066 -0.070 -0.013 -0.017 -0.006 -0.034
S-Value   -33 -15 -23 -7 -17 -21 -19
P-Value   0.001 0.108 0.023 0.300 0.078 0.036 0.054

Page last updated 30 March 2005