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Satellite and Tower Data Reveal Unique Climate Over the Southern Sierra Nevada
Eric WallerDepartment of Environmental Science, Policy, and Management
University of California, Berkeley
SSCZO Annual MeetingFresno, CA
8/4/14
MODIS Aqua (~1 PM)April Cloud Frequency,2003-2011
Average MODIS (Aqua) 2012 Diel Land Surface Temperature Range (Day – Night)
{Clear Sky Days!}
Δ 0C
Average Annual MODIS Diel Land Surface Temperature Range (C)
Aver
age
Annu
al M
OD
IS
Clou
d Fr
eque
ncy
(%)
R2 = 0.58Sequoia Points
Other Sierra NevadaPoints
405 meters
1160 meters
2015 meters
2700 meters
NoonFebruaryMarch
April
January
Average ½ Hourly Temperature by Month: 2015 meter site
Noon
Average ½ Hourly Dew Point Temperature by Month: 2015 meter site
Afternoonpeaks
Noon
Average ½ Hourly Relative Humidity by Month: 2015 meter site
Noon
Average ½ Hourly Relative Humidity by Month: 2015 m site, Clear Afternoons
Noon
Average ½ Hourly Relative Humidity for 4 Towers: April
Noon
No daytime warm-up at tower at 2015 meters
Average ½ Hourly Temperature for 4 Towers: April
°C
October minus April maximum temperature (California mountains unusually cold in April!)
Where’s this cold spring air coming from?
-still cold North Pacific
-Pacific high migrating north: winds/weather generally coming from
northwest rather than the west (confirmed by NCEP/NARR data)
-meridional flow: cutoff or closed lows
Regional and local conditions that favor Giant Sequoia:
-Low wind-Frequent high afternoon humidity and cloud cover-Late spring shift in precipitation -Cold spring storms: late spring shift in snowfall
A lot of these factors that could be beneficial to Sequoia could be reducing sublimation substantially as well.
A need for better Sierra-wide mapping of sublimation?
This area also has among the lowest average wind speeds in the world.
Giant Sequoia is responding to some combination of these climatic features – basically outcompeting other species in this unique climate regime.
In sum:
Unusually cloudy, particularly on spring afternoons (strongest predictor of Giant Sequoia distribution)
But there are a lot of (cor)related variables:• Unusually low spring temperatures (April COLDER than January)• Low diel temperature range (so spring afternoons especially cool)• Afternoon peaks in water vapor
• Highest relative humidity in the afternoon • Lowest vapor pressure deficit in the afternoon
• Extremely low wind
Much of this unusual behavior only evident at height
NOT PRE-DAWN!
Targeted climatic measurements above the surface
Daily patterns of temperature and humidity (rather than just min and max or average)
Extra measurements: wind, radiation (direct and diffuse), etc.
Relate to plant phyisological ecology and productivity
Some extra factors to consider in assessing climates