Satellite and Tower Data Reveal Unique Climate Over the Southern Sierra Nevada Eric Waller Department of Environmental Science, Policy, and Management University of California, Berkeley SSCZO Annual Meeting Fresno, CA 8/4/14

MODIS Aqua (~1 PM) April Cloud Frequency,

Average MODIS (Aqua) 2012 Diel Land Surface Temperature Range (Day – Night) {Clear Sky Days!} Δ 0CΔ 0C

Average Annual MODIS Diel Land Surface Temperature Range (C) Average Annual MODIS Cloud Frequency (%) R 2 = 0.58 Sequoia Points Other Sierra Nevada Points

405 meters 1160 meters 2015 meters 2700 meters

Noon February March April January Average ½ Hourly Temperature by Month: 2015 meter site

Noon Average ½ Hourly Dew Point Temperature by Month: 2015 meter site Afternoon peaks

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