(BRAVO) Study: Final Report. - Desert Research Institute

Final Report — September 2004
The 1999 average temperatures in July and August were statistically different (at the
0.05 level) from temperatures during the same months in previous years, but are still within 2
°C. We also conclude that the mean relative humidities in July, August, and October 1999
were statistically different (at the 0.05 level) than during the same months in the previous
five years; however, the standard deviation in the five-year data set indicates considerable
variability from year to year. The 1999 values were not consistently higher or lower than the
averages during the historical period.
Wind data from 1995 through 1999 were also examined, though only qualitatively.
Wind roses in Figures 7-1 through 7-4 (again grouped by month) illustrate monthly
distributions of wind speed and direction for 1995-98 versus 1999. (The numerals in the
centers indicate the percentages of time that the wind was calm.) There are some differences,
such as a stronger SE component in July 1999 and a varying NW component in October 1999
(less frequent NW winds, but more frequent high speeds from the NNW than the historical
period). However, the roses are generally similar enough to indicate that wind patterns at
Big Bend during the BRAVO Study were generally characteristic of those in the previous
years.
Big Bend National Park Month of
July 1, 1995 through July 31, 1998
Big Bend National Park during BRAVO
July 1, 1999 through July 31, 1999
N
N
27%
21%
18
14
9
7
W 5.4%
E
W 6.7%
E
Level: 10 m
S
Winds: Direction
Level: 10 m
S
Winds: Direction
1.01 to 1.54 3.09 to 5.14 8.23 to 10.8
1.54 to 3.09 5.14 to 8.23 >= 10.8 (m/s)
Number of Records Used: 2463
1.01 to 1.54 3.09 to 5.14 8.23 to 10.8
1.54 to 3.09 5.14 to 8.23 >= 10.8 (m/s)
Number of Records Used: 744
Figure 7-1. Comparison of wind roses for July 1995-1998 (left) and 1999 (right).
7-2