treasure valley road dust study: final report - ResearchGate

Pecentile among days with
precipitation
100
90
80
70
60
50
40
30
20
10
0
0.01 0.1 1 10
Daily precipitation (inches)
Figure B-1. Cumulative frequency distribution of daily precipitation for days with measurable precipitation
at Boise Airport January 1940-November 2001.
Table B-2 and Figure B-2 summarize the persistence of days with precipitation. Of the
90 days per year with precipitation about 24 days each are in episodes with 1 or 2 consecutive
days. On average about 15 days per year are in episodes with 3 consecutive days; 10 days are in
episodes with 4 consecutive days. The maximum number of consecutive days on record is 16.
However, the number of consecutive days with precipitation exceeded 8 days only 12 times in 61
years.
Table B-2. Summary of precipitation persistence (consecutive days).
Consecutive days
with precipitation
Number of
occurrences
(1940-2001)
Total
Days
Occurrences per
year
Days per
year
Cumulative
days per year
16 1 16 0.02 0.26 0.26
15 1 15 0.02 0.24 0.50
13 1 13 0.02 0.21 0.71
12 2 24 0.03 0.39 1.10
11 2 22 0.03 0.36 1.45
10 1 10 0.02 0.16 1.62
9 4 36 0.06 0.58 2.20
8 12 96 0.19 1.55 3.75
7 22 154 0.36 2.49 6.24
6 34 204 0.55 3.30 9.53
5 85 425 1.37 6.87 16.40
4 163 652 2.63 10.53 26.93
3 310 930 5.01 15.03 41.96
2 742 1484 11.99 23.98 65.94
1 1474 1474 23.82 23.82 89.76
0 17049 17049 275.47 275.47 365.23
Table B-3 shows information equivalent to Table B-2, except for snowfall days rather
than precipitation (rain or snow). For days with snowfall, the snowfall is on average equivalent
to approximately 11 times the recorded liquid water equivalent. This equivalence is probably
understated since some of the days with recorded snowfall would have had a combination of
both rain and snow.
B-3