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Thursday, June 4, 2015

Weather Summary Update: Spring 2015; by Dr. Richard Chapleau


A storm system moving over the Tehachapi Mountains, viewed from the verdant blooming Antelope Valley, March 2015.


It seems like the California drought is a hot topic on everyone’s mind these days, and that’s certainly a good thing. But can we understand more about the severity of the regional drought here on Tejon Ranch and its effects on biodiversity by looking closely at weather instrument data to see how much rain falls, or where the temperature is most extreme? How is the weather changing over time? How does precipitation vary across the diverse topography of the Ranch and what effects does it produce? Good questions, and we’re just beginning to see some tantalizing patterns.

On the Ranch, the Conservancy monitors seven (soon to be eight) weather stations spread out across the 270,000 acres that make up the Ranch. From our lowest elevation sites in the San Joaquin Valley (500 feet), up to our highest elevation in the Tehachapi Mountains (6800 feet), and over to our high desert grass and shrublands of the Antelope Valley in the extreme western Mojave Desert (3000 feet), there’s an extraordinary diversity of elevation and aspect. For this season’s weather summary, we’re looking closely at three of the seven stations. Here’s a look at the data for the spring months, plus the total rainfall from October 2014 through April 2015 at each station.

Comanche Point
San Joaquin Valley, elevation 562 feet
Total Rainfall October 2014-April 2015: 1.11 inches


Average temperature (°F)
Maximum temperature (°F)
Minimum temperature (°F)
Precipitation (inches)
February
65.4
76.7
52.9
0.00
March
66
90.1
47.7
0.00
April
64.3
93.4
39.6
0.09
 

Michener
Ridgeline of mountains north of Gorman, elevation 4716 feet
Total Rainfall October 2014-April 2015; 5.30”


Average temperature (°F)
Maximum temperature (°F)
Minimum temperature (°F)
Precipitation (inches)
February
53.7
71
34.6
0.22
March
55.6
79
34.9
0.43
April
53.6
80.8
33.4
0.44

Antelope Canyon
Antelope Valley, elevation 3594 feet
Total Rainfall October 2014-April 2015; 6.64”


Average temperature (°F)
Maximum temperature (°F)
Minimum temperature (°F)
Precipitation (inches)
February
57
83.1
34.2
0.66
March
57.7
82
31
0.80
April
57
83.1
34.2
0.66

Notice that the Antelope Canyon weather station reported the most rain at 6.64 inches, far more than the amount seen on the San Joaquin side of the Ranch. Docents and professional staff both noted the spectacular wildflower display in the Antelope Valley. Additionally, pronghorn seemed exceptionally easy to view this spring in the Antelope Canyon area, and three new fawns have been observed adjacent to this canyon.

In contrast, Comanche Point actually experienced three months during October-April with no rain at all. In fact, wildflower viewing on the San Joaquin side was cancelled for the season due to a sparse display. What we did see in this area was an astounding density and distribution of exotic invasive mustard species—Saharan mustard (Brassica tournefortii), short pod mustard (Hirschfeldia incana), and hedge mustards (Sisymbrium spp.). Land managers across the state have been marveling at the banner year that invasive mustards are having, and Tejon Ranch is no exception. Warm and dry winters seem to favor these concerning species—something for managers to be aware of in planning weed treatment efforts in future growing seasons.

We’d love to look at longer trends in the weather data--do springs flow more in wet seasons or is groundwater unaffected? Is Antelope Canyon a small microenvironment that tends to see more rain, or was this just a fluke “outlier” year? Are pronghorn always in that area in the spring, or did they gather there just for this season? Does the weather information we’re gathering here at the Ranch agree with weather stations from nearby locations?  We’ve just started gathering and analyzing the weather data, and are working to upgrade the actual station instruments. Some weather stations are older than others, and require a loving touch to maintain. Over the next few years, we hope to upgrade all of the stations, and perhaps add more stations in other interesting areas of the Ranch. Still, it’s fascinating to look at this one snapshot of spring season and see the overt response of precipitation driving biodiversity.




Dr. Richard Chapleau is a retired science teacher who lives in the Antelope Valley neighboring Tejon Ranch. He and his wife Lisa Chapleau, a retired math teacher, have been volunteering with the Conservancy for a year and have inspired Conservancy staff with their keen smarts, their many talents, and their phenomenal generosity of time, expertise, and exceptional homegrown eggs. Among other kind donations of time and energy, they have taken the helm of our weather program--maintaining weather stations, downloading and organizing data, and analyzing results. This spring they installed a newly acquired RainWise weather station at the Conservancy office in Lebec with a live link online for real-time weather data. Check it out at: