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Eos, Vol. 94, No. 11, 12 March 2013
VOLUME 94
NUMBER 11
12 MARCH 2013
EOS, TRANSACTIONS, AMERICAN GEOPHYSICAL UNION
PAGES 105–112
A Network for Observing
Great Basin Climate Change
such processes as plant phenology, snow
accumulation, and snowmelt (Figure 1,
insets C and D). Webcams may be operated
manually from any computer connected to
the Internet, thus providing visual access of
the sites to a wide audience, from researchers
to school children.
Additional instrumentation can be added
to the stations. For example, sap flow sensors
and point dendrometers that continuously
quantify stem radial growth were added to
trees along the transects to measure the
timing of transpiration and growth in woody
plant species. Further, the actual amounts
and timing of precipitation, temperature, and
atmospheric vapor pressure deficit (VPD, also
known as evaporative demand), as collected
by sensors on the networks, can be compared
with tree ring growth patterns (from increment cores and microcores) recorded by the
new dendrometers to more finely calibrate
climate–tree ring relationships and enable
more accurate reconstruction of past
conditions. In a separate experiment, cold air
drainage is being monitored within a wash
located between two stations. Sensors have
been spatially distributed to measure air
temperature, wind speeds, tree sap flow, and
plant water status to better understand the
geographic and climatic conditions in which
cold air drainage is favored and to determine
the linkage between cold air movement and
plant response.
All the instruments in each NevCAN station
are located within an area of 1 hectare
(0.01 square kilometer). This footprint (1) is
an appropriate scale for modeling purposes
that rely upon satellite data and gridded
remote sensing products and (2) provides
sufficient space for establishing replicated
experimental plots for future studies. Detailed
plant lists have been made for each site, and
ongoing studies that combine ground truth
with remote sensing data are under way to
provide a complete and accurate representation of the plant communities found at each
elevation.
PAGES 105 –106
The ability to evaluate accurately the
response of the environment to climate
change ideally involves long‐term continuous
in situ measurements of climate and
landscape processes. This is the goal of the
Nevada Climate‐Ecohydrology Assessment
Network (NevCAN), a novel system of
permanent monitoring stations located across
elevational and latitudinal gradients within
the Great Basin hydrographic region
(Figure 1). NevCAN was designed, first, to
quantify the daily, seasonal, and interannual
variability in climate that occurs from basin
valleys to mountain tops of the Great Basin in
the arid southwest of the United States;
second, to relate the temporal patterns of
ecohydrologic response to climate occurring
within each of the major ecosystems that
compose the Great Basin; and, last, to
monitor changes in climate that modulate
water availability, sequestration of carbon,
and conservation of biological diversity.
NevCAN is the only long‐term climate
monitoring network specifically designed to
measure altitudinal and latitudinal variation
in climate change across the Great Basin, a
major ecoregion in the conterminous United
States. While NevCAN shares several features
with the National Ecological Observatory
Network (NEON), it has been undertaken at a
grassroots level—meaning that its concept,
design, and construction were the efforts of
field scientists—and is designed to address
science questions particularly relevant to
semiarid and mountainous environments. In
addition to providing free and open access to
real‐time data and data products through the
Nevada Climate Change Portal (NCCP; http://
sensor.nevada.edu/NCCP/Default.aspx), the
network has also been engineered to provide
data for immediate use by a wide range of
environmental scientists. Further,
it has been designed to be a sustainable
platform for both experimental and observa-
BY S. MENSING, S. STRACHAN, J. ARNONE,
L. FENSTERMAKER, F. BIONDI, D. DEVITT,
B. JOHNSON, B. BIRD, AND E. FRITZINGER
tional research, and its sensors have been
chosen to enable synergy between hydrological, ecological, and climatological research.
Transect Design
NevCAN has been built as two basin‐to‐
mountaintop transects, one in the north
across the Snake Range and Great Basin
National Park and another in the south across
the Sheep Range, about 35 kilometers
northwest of the Las Vegas metropolitan
center (Figure 1). The Snake Range transect
experiences a winter‐dominated precipitation
regime characterized by Pacific frontal storm
systems with summer thunderstorms still
common (see Table S1 in the additional
supporting information that can be found in
the online version of this article). This west‐to‐
east transect includes seven new stations plus
an existing eddy covariance station, located
in the center of each major vegetation zone
along the transect’s altitudinal gradient. The
Sheep Range transect is within a summer‐
dominated precipitation regime with a
relatively large component of annual moisture
coming from monsoonal systems. This south‐
to‐north transect includes four new stations
plus an existing National Resources
Conservation Service Soil Climate Analysis
Network (SCAN) site.
Each station site is instrumented with a
common set of equipment selected to monitor
aspects of the surface hydrologic balance and
key ecological processes. Sensors measure
precipitation (snow and rain), air temperature,
wind speed and direction, incoming and
outgoing long‐ and short‐wave electromagnetic radiation (to help track ecosystem
energy balance, changes in the fraction of
solar energy absorbed, and nighttime cloud
cover), relative humidity, barometric pressure,
and soil moisture and temperature. The
majority of these sensors are capturing data
at intervals as fine as 1 minute so that
research across a broad range of temporal
scales may be pursued. A webcam that can
pan, tilt, and zoom is mounted on each tower
to provide real‐time assessment of site
conditions as well as archival photographs to
quantify temporal and spatial dynamics of
© 2013. American Geophysical Union. All Rights Reserved.
Climate Data During the First Year
of NevCAN Operation
NevCAN’s first year of operation
(1 October 2011 to 30 September 2012)
has yielded annual averages and totals
for a number of climate variables using
10‐minute values recorded at each transect
site. Table S1 illustrates the range of climatic
Eos, Vol. 94, No. 11, 12 March 2013
Fig. 1. Map of the Nevada Climate-Ecohydrology Assessment Network (NevCAN) transects. Inset A shows the subalpine station on the western
slope of the Snake Range at an elevation of 3360 meters with Pinus longaeva (bristlecone pine), Picea engelmannii (Engelmann spruce), and
Pinus flexilis (limber pine). Inset B illustrates cross-section profiles of tower elevations for each transect. Landscape monitoring by this site’s
webcam is illustrated in insets C and D, here showing patterns of snowmelt and snowfall that can be correlated with sensor climatic data.
conditions represented by the two transects,
and Figure S1 shows how these climate
variables change with elevation. The slope
of each line in Figure S1 represents the
environmental lapse rate, meaning the rate
of change in an environmental variable with
each unit of increase in elevation.
Clear elevational trends were seen in
annual measures of climate, including those
that codetermine or describe aridity (VPD,
mean annual precipitation, mean annual
temperature, and wind speed). As expected,
air temperature, number of growing degree‐
days (classified as when air temperature is
equal to or above freezing, indicating that
plant growth can occur), the date of freezing
(when air temperature was sustained below
−2 °C), and VPD decreased with increasing
elevation at both transects. By contrast,
precipitation, date of last freezing, number
of days with snow cover, the aridity/moisture
index that indicates how dry or moist an
environment is based on the quotient of
mean annual precipitation (measure of
water input), and mean annual temperature
(a proxy for evaporation potential) increased
with elevation (Figure S1). Wind speeds did
not vary with any trends among sites at the
southern transect but decreased with
increasing elevation at the northern transect.
All of these elevational patterns observed
during the first year of NevCAN operation,
in concert with patterns observed in future
years, will provide a quantitative baseline
for analyzing possible shifts in the “steepness”
of measured lapse rates that may be caused
by natural and anthropogenic climate
change.
Somewhat surprising was that elevational
lapse rates for most climate variables differed
between the northern and southern transects.
Steeper lapse rates observed at the southern
transect indicated a greater role of elevation
in determining precipitation, moisture
(decrease in aridity), and number of days
with snow cover (Figure S1). At the northern
transect, steeper lapse rates showed faster
elevational changes in date of last hard frost,
mean annual air temperature, and date of first
hard frost (Tables S2 and S3).
Latitudinal differences in climate observed
during the first year of NevCAN operation
occurred mostly as expected. The southern
transect exhibited higher mean annual air
temperature (by 4.5 °C), more growing
degree‐days (69), lower precipitation
(by about 80 millimeters), fewer days
with snow cover (by 101 days), and lower
moisture index values. There was almost
no difference between transects in dates of
the first and last hard frosts or in vapor
pressure deficit.
© 2013. American Geophysical Union. All Rights Reserved.
A Rich Data Source
A tiny sample of the data available from
these transects has been explored, but they
nonetheless illustrate the potential for
NevCAN’s use in environmental change
research. The great variety of climates
expressed across the range of ecosystems
represented by NevCAN’s transect sites
affords numerous opportunities for research
and education.
Currently, researchers are analyzing
sensor data to determine what ecoclimatic
variables control seasonal growth of trees
and shrubs across the entire elevational
gradient. NevCAN has added various
experimental sensor arrays on the landscape
centered on individual stations to identify
and monitor microclimates that play a
critical role in water availability and biological diversity.
Archived data and imagery may be queried
through the NCCP for each sensor
or a combination of sensors at time steps
ranging from 1 minute (meteorological) to
1 hour (webcams), with aggregation into
longer‐term averages available as an option
prior to download. Data are available to
anyone, and those interested in studying
climate variability and climate change
impacts through this new data set are
Eos, Vol. 94, No. 11, 12 March 2013
encouraged to learn more at http://sensor.
nevada.edu/NCCP/Default.aspx.
Acknowledgment
This material is based upon work supported by the U.S. National Science
Foundation under grant EPS‐0814372.
— SCOTT MENSING and SCOTTY STRACHAN,
Department of Geography, University of Nevada,
Reno; E-mail: [email protected]; JAY ARNONE,
Division of Earth and Ecosystem Sciences,
Desert Research Institute, Reno, Nev.; LYNN
FENSTERMAKER, Division of Earth and Ecosystem
Sciences, Desert Research Institute, Las Vegas, Nev;
FRANCO BIONDI, Department of Geography, University of Nevada, Reno; DALE DEVITT, Department of
Soil and Water Science, University of Nevada, Las
Vegas; BRITTANY JOHNSON, Division of Earth and
Ecosystem Sciences, Desert Research Institute,
Reno, Nev.; BRIAN BIRD, Department of Soil and
© 2013. American Geophysical Union. All Rights Reserved.
Water Science, University of Nevada, Las Vegas;
and ERIC FRITZINGER, Department of Computer
Sciences, University of Nevada, Reno