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Water Resources Research
RESEARCH ARTICLE
10.1002/2013WR013711
Key Points:
Hydrologic modeling data set from
high-elevation, snow-dominated
catchment
Hydrologic data set reflects
enhanced radiative forcings of
snowpack processes
Senator Beck Basin is representative
of many Colorado River tributary
headwaters
Mountain system monitoring at Senator Beck Basin,
San Juan Mountains, Colorado: A new integrative data source
to develop and evaluate models of snow and hydrologic
processes
Christopher C. Landry1, Kimberly A. Buck1, Mark S. Raleigh2, and Martyn P. Clark2
1
Center for Snow and Avalanche Studies, Silverton, Colorado, USA, 2National Center for Atmospheric Research, Boulder,
Colorado, USA
Abstract A hydrologic modeling data set is presented for water years 2006 through 2012 from the SenaSupporting Information:
Readme
Data set 1–6
Correspondence to:
C. C. Landry,
[email protected]
Citation:
Landry, C. C., K. A. Buck, M. S. Raleigh,
and M. P. Clark (2014), Mountain
system monitoring at Senator Beck
Basin, San Juan Mountains, Colorado: A
new integrative data source to
develop and evaluate models of snow
and hydrologic processes, Water
Resour. Res., 50, 1773–1788,
doi:10.1002/2013WR013711.
Received 19 FEB 2013
Accepted 6 FEB 2014
Accepted article online 12 FEB 2014
Published online 26 FEB 2014
tor Beck Basin (SBB) study area. SBB is a high altitude, 291 ha catchment in southwest Colorado exhibiting a
continental, radiation-driven, alpine snow climate. Elevations range from 3362 m at the SBB pour point to
4118 m. Two study plots provide hourly forcing data including precipitation, wind speed, air temperature
and humidity, global solar radiation, downwelling thermal radiation, and pressure. Validation data include
snow depth, reflected solar radiation, snow surface infrared temperature, soil moisture, temperatures and
heat flux, and stream discharge. Snow water equivalence and other snowpack properties are captured in
snowpack profiles. An example of snow cover model testing using SBB data is discussed. Serially complete
data sets are published including both measured data as well as alternative, corrected data and, in conjunction with validation data, expand the physiographic scope of published mountain system hydrologic data
sets in support of advancements in snow hydrology modeling and understanding.
1. Introduction
Herein, we describe a hydrometeorological data set from the snow-dominated, high-elevation Senator Beck
Basin (SBB) study area, located at Red Mountain Pass (37 540 24.800 N, 107 430 34.600 W) in the western San
Juan Mountains range, southern Rocky Mountains, USA. SBB was conceived and purpose-built in 2003 as a
hydrologic research watershed and mountain system observatory by the independent, not-for-profit Center
for Snow and Avalanche Studies (CSAS) based in Silverton, Colorado (Figure 1). With elevations from 3362
m at the subalpine basin pour point to the 4118 m basin summit, SBB is a discrete catchment exhibiting a
continental, radiation-driven, alpine snow climate [Armstrong and Ives, 1976; Armstrong and Armstrong,
1987; Sturm et al., 1995; Mock and Birkeland, 2000]. Situated within headwaters of the Colorado River, and in
close proximity to the headwaters of the Rio Grande River, SBB is one of the five locations identified by Bales
et al. [2006] as providing critical data to improve understanding of mountain hydrology in the western
United States.
The high elevation of the Senator Beck Basin (3362–4118 m) distinguishes SBB from other snow-dominated
North American experimental watersheds such as the Reynolds Creek Experimental Watershed (RCEW) in
the intermountain high desert of southwestern Idaho (1000–2200 m) and the HJ Andrews LTER in the Oregon Cascades (410–1630 m). Marmot Creek Experimental Watershed in the Canadian Rockies (1585–2805
m), the Fraser Experimental Forest (2680–3903 m) near Fraser, Colorado, and the Niwot Ridge LTER (2900–
4100 m) located near Boulder, CO, all share alpine characteristics with SBB. However, much of the Niwot
Ridge LTER infrastructure is located on the ridge adjacent to the adjoining Green Lakes watershed and the
largely forested (and lower elevation) Marmot Creek Experimental Watershed is located at 51 N, with correspondingly different snow cover and radiation conditions. Further, both Marmot Creek and the Fraser
Experimental Forest have applied intensive forest management techniques designed to manipulate hydrologic yields.
To the best of our knowledge, with the notable exception of RCEW [Marks, 2001; Reba et al., 2012], these
other snow-dominated experimental watersheds as well as more recently developed critical zone observatories (CZOs) in the Jemez Mountains of New Mexico (1700–3432 m) and Southern Sierra Nevada (400–
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Figure 1. Orthophoto and location map of the Senator Beck Basin Study Area (SBB) catchment showing infrastructure locations of Senator Beck Study Plot (SBSP), Swamp Angel Study
Plot (SASP), Senator Beck Stream Gauge (SBSG), and Putney Study Plot (PTSP) as well as the Red Mountain Pass locale of the San Juan Mountains, Colorado. Study plot photos are of
SBSP looking southwest, SASP looking southwest, SBSG from above, and PTSP from the east, with SBB in the distance, far right. UTM grid coordinates of 1000 m, zone 13, are shown on
the image border.
2700 m) have not yet presented specific, coherent hydrologic data sets containing serially complete, multiyear precipitation, snow, solar and thermal radiation, temperature, humidity, and wind measurements in
conjunction with streamflow measured at the study area pour point. Our intent is to expand the physiographic scope of published mountain system hydrologic data sets to include an especially high-elevation
watershed experiencing snow cover conditions and radiative processes that are otherwise underrepresented and which may constitute an end-member among research watersheds. The following sections
describe SBB infrastructure, the data collected, summary data for water years (WY) 2006–2012, the construction of serially complete data to support model development and evaluation, and an example application
of snow model testing using SBB data.
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2. Site Description
Senator Beck Basin is a 291 ha headwater catchment of Red Mountain Creek and the Uncompahgre River
and spans elevations from 3362 m at the SBB pour point and stream gauge to 4118 m at the basin highpoint. The Uncompahgre River is a major tributary to the Gunnison River, itself a major tributary to the Colorado River providing water to seven states in the western United States. SBB also immediately adjoins
headwater catchments of the Animas River, a major tributary of the San Juan River, and headwaters of the
San Miguel River, a major tributary to the Dolores River, all of which are also tributaries to the Colorado
River. The headwater of the Rio Grande River is located 24 km southeast of SBB, flowing to the Gulf of Mexico and Atlantic Ocean. SBB is operated under a Special Use Permit issued by the Grand Mesa, Uncompahgre, and Gunnison National Forest to CSAS. The permit authorizes CSAS’s nonexclusive utilization of those
public lands for mountain system research, monitoring, and field education through 2040.
SBB consists of primarily alpine terrain composed of bare rock and tundra above 3700 m, bands of Krumholtz from 3700 to 3600 m, and subalpine forest below 3600 m. While SBB elevations, terrain characteristics,
plant communities, volcanic geology, and weather are representative of adjoining terrain and catchments
in the western San Juan Mountains, SBB is comparatively pristine and does not contain modern roads or
established foot trails and comparatively minor, residual impacts of historic precious metals mining in the
locale. SBB water quality, therefore, is also comparatively high despite the heavily mineralized volcanic geology. The U.S. Forest Service prohibits motorized winter recreation (snowmobiling) in SBB.
3. Automated and Manual Measurements
Four separate arrays of monitoring infrastructure, including a stream gauging station, have been developed
at SBB to support hydrologic research and mountain system monitoring (Figure 1). Year-round data collection began in water year (WY) 2005 capturing continuous automated measurements of near-surface meteorological fields (precipitation, temperature, humidity, wind, radiation, and atmospheric pressure), snow
depth, soil moisture, soil temperature and soil heat flux, and streamflow. A distinguishing characteristic of
SBB data are the extensive suite of radiation measurements, including direct broadband solar radiation,
direct near-infrared/shortwave-infrared (NIR/SWIR) solar radiation, diffuse broadband solar radiation at solar
noon, downwelling thermal radiation, reflected broadband shortwave radiation, reflected NIR/SWIR radiation, and infrared snow surface temperature.
Two intensively instrumented study plots represent the principal SBB landscape domains—alpine tundra
and subalpine forest—and both plots contain nearly identical weather, soils, snowpack, and radiation instrumentation. The Senator Beck Study Plot (SBSP, 3714 m) captures data at an exposed, near-level location in
the alpine tundra where wind strongly influences snowpack formation. Precipitation is not monitored at
this site. The Swamp Angel Study Plot (SASP, 3371 m) is located in a large, near-level forest clearing located
near the SBB pour point. Terrain surrounding SASP provides shelter and optimizes snowpack and precipitation measurements under minimal wind influence. Both SBSP and SASP have adjoining snow plots where
time series of snowpack profiles are conducted in previously undisturbed snow.
A third instrumentation array is located immediately east of SBB at a ridge-top site developed in the 1970s,
the Putney Study Plot (PTSP, 3756 m), 42 m higher than SBSP. This site, on a subsummit of an extended
ridgeline, minimizes local terrain influences on measurements of wind speed and direction, air temperature,
and humidity. PTSP data therefore augment measurements of those parameters at SASP and SBSP, where
known terrain effects occur, and provide a baseline for those parameters (at 3756 m) with which to compare SASP and SBSP conditions. In developing this hydrologic data set, PTSP data have been used to estimate missing data for those parameters at the other two SBB plots. Due to SBB’s high-elevation and
continental snow climate, instrumentation riming episodes are extremely rare, minor, and short-lived.
Finally, Senator Beck Stream Gauge (SBSG, 3362 m) is a broad-crested, notched weir located at the SBB pour
point, in a small gorge incised through a bedrock outcrop.
Forcing data are captured in 1, 3, and 24 h summary arrays at SBSP, SASP, and PTSP; additional solar noon
data are collected in 2 min arrays at SBSP and SASP. Forcing data at SBSP and SASP include precipitation
(SASP only), wind speed and direction, air temperature and relative humidity, direct and diffuse incoming
solar radiation, incoming thermal radiation, and barometric pressure (SASP only). Continuous, year-round
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Table 1. Forcing Data for the SBSP, SASP, and PTSP Sites, Including Parameters Measured, Current Sensor, Site, Measurement Height (Above Ground), Selected Mean Water Year Values, and Period of Recorda
Parameter
Current Sensor
Site
Measurement Height (m)
Mean Water Year Value
Period of Record (WY)
Precipitation
Wind speed and direction
ETI Noah II (30.5 cm)
RM Young Wind Monitor 05103-5
Air temperature
Vaisala HMP50YA
Vaisala CS500, HMP50YA
Vaisala HMP35-C
Vaisala HMP50YA
Vaisala CS500, HMP50YA
Vaisala HMP35-C
K&Z CM21 Pyranometer
SASP
SBSP
SASP
PTSP
SBSP
SASP
PTSP
SBSP
SASP
PTSP
SBSP
SASP
SBSP
SASP
SBSP
SASP
SBSP
SASP
SASP
5.5
9.6, 4.0
6.0, 3.8
9.5
3.8, 8.7
3.4, 6.0
3.1
3.8, 8.7
3.4, 6.0
3.1
9.4
5.7
9.4
5.7
9.4
5.7
9.4
5.7
4.1
1190 mm
3.0 m s21, 265
1.2 m s21, 222
5.4 m s21, 213
21.2 C, 20.7 C
0.5 C, 0.8 C
21.3 C
57.9%, 55.6%
62.1%, 58.4%
57.1%
213 W m22
188 W m22
112 W m22
97 W m22
Na
Na
229 W m22
249 W m22
na
2005–2012
2005–2012
2005–2012
2007–2012b
2005–2012c
2005–2012c
2007–2012b
2005–2012c
2005–2012c
2007–2012b
2005–2012d
2005–2012e
2005–2012d
2005–2012e
2005–2012d
2005–2012e
2005–2012d
2005–2012e
2005–2012
Humidity
Incoming solar radiation
Incoming solar radiation
Incoming thermal radiation
K&Z CM21 RG695
NIR/SWIR Pyranometer
K&Z CM21 Pyranometer
Swiss ASRB Shadow Arm
K&Z CG-4 Pyrgeometer
Barometric pressure
Vaisala PTB101B
Diffuse incoming solar radiation
a
Manufacturer abbreviations: CSI 5 Campbell Scientific, Inc.; K&Z 5 Kipp & Zonen.
PTSP data were interrupted during summers 2005 and 2006 to avoid lightning damage.
c
PTSP data were interrupted during summers 2005 and 2006, SBSP and SBSP upper position data begin 8 February 2006.
d
SBSP data for this parameter began 19 January 2005.
e
SASP data for this parameter began 25 January 2005.
b
data for those parameters began in WY 2005, noting that radiation measurements began midwinter that
season.
At PTSP, forcing data include wind speed and direction, air temperature, and relative humidity. PTSP data
collection began during WY 2005 but was interrupted during summers 2005 and 2006 until year-round,
continuous operation of the site began in WY 2007.
System response (validation) data collected at SBSP and SASP include snow depth, reflected solar radiation,
snow surface infrared temperature, snow water equivalent (measured manually), soil temperatures, soil
heat flux, and soil moisture. Soil measurements began during the summer of 2005. Formal snowpack profiles are performed in time series’ at both SBSP and SASP throughout the snow covered season. Stream discharge is measured immediately below SASP in 1 and 24 h arrays. SBSG data began in summer 2005 and
are collected seasonally from late winter through early winter; sensors are removed during the very low
base flows during overwinter months to prevent ice damage. No validation data are collected at PTSP.
4. Data Descriptions
Table 1 summarizes forcing data collected at SBB during the WY 2005–2012 period of record, listing the current sensors deployed by site, their type and height, and summary statistics. Table 2 presents the same
information for system response (validation) parameters.
4.1. Data Availability
The SBB data described herein are available in the Supporting Information, while additional data (e.g., data
after WY 2012) are presented at the CSAS website (http://www.snowstudies.org/data) in a variety of formats
and compilations. Serially complete meteorological forcing data are presented for SASP and SBSP for WY
2006–2012, with associated readme files describing file contents and missing data in-fill methods. Second,
all SBB data, including SBSG and PTSP data, are also available in continuous, comma delimited format for
the entire period of record, including years subsequent to WY 2012. Comprehensive metadata are provided
and document study site development, sensor details and histories, data logger programming, and complete data file structure for all sites. Raw seasonal data sets in spreadsheet format are also available for all
SBB sites for the period of record at the CSAS website. Finally, snow profiles containing SWE and other
measurements, and other summary data sets are also available at the CSAS website, including Sensor Status
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Table 2. Validation Data for the SBSG, SBSP, and SASP Sites, Including Parameters Measured, Current Sensor, Site, Measurement Height (Above Ground), Selected Mean Water Year
Values, and Period of Recorda
Parameter
Current Sensor
Site
Measurement Height (m)
Water Year Value
Period of Record (WY)
Stream discharge
Druck PDCR 1830–8388 Vented Transducer
SBSG
na
2005–2012
Snow depth
CSI SR50 ultrasonic distance ranger
Snow water equivalence
Manual observations
3.6
3.2
Collected during snow profiles
Reflected solar radiation
K&Z CM21 Pyranometer
Reflected solar radiation
K&Z CM21 RG695 NIR/SWIR Pyranometer
Infrared snow surface temperature
AlpuG SnowSurf
Soil moisture (VLWC)
CSI CS616 water content reflectometer
Soil temperature
CSI 107 Temperature Probe
Soil heat flux
REBS HFT-3.1
SBSP
SASP
SBSP
SASP
SBSPb
SASPc
SBSPb
SASPc
SBSPd
SASPe
SBSP
SASP
SBSP
SASP
SBSP
SASP
Max 2,082,000 m3 (WY2008)
Min 1,306,000 m3 (WY2012)
Max 2.91 m (WY2005)
Max 2.90 m (WY2008)
Max 1101 mm (WY2005)
Max 999 mm (WY2011)
121 W m22
99 W m22
58 W m22
51 W m22
na
3.6
3.2
3.6
3.2
3.6
3.2
20.10
0.0, 20.1, 20.2, 20.25
0.0, 20.1, 20.2, 20.4
20.03
20.03
Mean 32%
Mean 26%
1.8, 1.8, 1.7, 1.8 C
4.1, 3.9, 4.0, 4.1 C
0.1 W m22
0.1 W m22
2003–2012
2004–2012
2003–2012
2003–2012
2005–2012
2005–2012
2005–2012
2005–2012
2005–2012
2005–2012
a
Manufacturer abbreviations: CSI 5 Campbell Scientific, Inc.; K&Z 5 Kipp & Zonen.
SBSP data for this parameter began 19 January 2005.
SASP data for this parameter began 25 January 2005.
d
SBSP data for this parameter began 12 December 2005.
e
SASP data for this parameter began 12 May 2006.
b
c
Workbooks (see section 4.4.2). SBB data usage and citation policies are also posted at the CSAS website,
with contact information for additional details.
4.2. Meteorological and Other Forcing Data
4.2.1. Precipitation
Continuous measurements of precipitation, as rain and snow, are collected at the well-sheltered SASP site
only; wind exposure at the alpine SBSP site precludes effective measurement of precipitation. The ETI Noah
II precipitation gauge at SASP includes an Alter shield with constrained tines. Both raw and wind-corrected
precipitation data are presented to illustrate gauge capture efficiency and show a cumulative 6% undercapture based on WMO equations for the 8 year period of record (Figure 2). Adjoining snow board measurements over five winter seasons and 57 interval measurements found a mean precipitation gauge
undercapture rate for winter storms of 20.6% (median 5 0.0%).
Total measured precipitation for WY 2005–2012 ranged from a high of 1397 mm in WY 2011 to a low of 903
mm in WY2012. Over that 8 year period, 74% of precipitation fell as snow, and the remainder as rain, as
directly observed or inferred from SASP data. The southwest United States monsoon dominates July and
August weather at SBB. Given the high elevations, rain on snow events have been very rare, and minor, at
SBB between November and May, as evidenced by calculated wet-bulb data (Figure 3). Marks et al. [2013]
showed that the wet-bulb temperature is a better predictor of precipitation phase than air temperature.
Mixed-phase precipitation events are
more frequent in September and
October than in June, the driest
month of the water year. Phase allocation for those mixed events has
been based on measured snowfall,
temperature and other SBB data, and
direct observations. The addition of
phase detection sensors to SBB sites
Figure 2. Measured and wind-corrected cumulative precipitation at SASP for WY
would enable more definitive detec2006–2012, estimating 6% under-catch by the precipitation gauge for that 8 year
tion of mixed-phase precipitation as
period.
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and when such events, and midwinter rain-on-snow events, may
increase in frequency due to
regional warming. Recent water
years have included both very wet
(2008) and very dry (2012) winters,
similar in magnitude to period of
record extremes observed at the
nearby Red Mountain Pass SnoTEL
site, located 1.8 km south of SASP
and at a similar elevation (3413 m).
4.2.2. Wind
Wind speed and direction are monitored at all three study plots, with a
single sensor at PTSP and with stationary ‘‘lower’’ and ‘‘upper’’ sensors
at SBSP and SASP. Wind conditions
at PTSP preclude the formation of
any significant snow cover at that
site. Mid-day sensor heights above
the seasonal snow cover at SASP
and SBSP are documented in supplemental winter season Sensor Status Workbooks (see Ancillary Data
discussion in section 4.4.2). These
wind sensors have a speed measurement range of 0–60 m s21 with
threshold sensitivity of 0.9 m s21.
Figure 3. Hourly calculated wet-bulb temperatures during periods of precipitation
Both scalar and resultant mean
>0 mm, by month, over the WY 2006–2012 period of record at (a) SBSP and (b) SASP.
wind speed data are calculated
Data are shown for all precipitation hours (regardless of snow cover) and all precipitation hours with snow cover (i.e., measured snow depth >0 mm).
using Campbell Scientific Loggernet
2.1c Instruction P69, along with
resultant direction and standard
deviation of direction. Among those three sites, as described above, PTSP captures the most representative
ridgetop wind speed and direction data in the Red Mountain Pass and SBB locale.
Water year 24 h mean wind speeds over the six complete years of record (WY 2007–2012) at PTSP ranged
from 6.1 to 7.0 m s21 (scalar) and from 4.8 to 5.9 m s21 (resultant) and directions ranged from 204.8 to
221.2 (resultant). Mean (resultant) wind direction for the WY 2007–2012 period was 213.4 with standard
deviation 35.8 and the peak gust recorded during that period was 48.1 m s21.
SBSP data, by comparison, clearly reflect the influence of surrounding SBB terrain, biasing wind direction as
well as reducing speeds, compared to PTSP. Mean 24 h wind speeds at the upper wind monitor sensor at
SBSP were 4.1 (scalar) and 3.0 m s21 (resultant) over the WY 2005–2012 period, and directions ranged from
259.7 to 272.7 (resultant). Mean (resultant) wind direction for the WY 2005–2012 period was 265.5 with
standard deviation 42.7 and peak gust at SBSP was 36.0 m s21 during that period.
Wind behavior at SASP is substantially constrained by adjoining sheltering terrain and vegetation and does
not represent general wind conditions in SBB or the Red Mountain Pass locale. Mean 24 h wind speed for
the period of record at SASP was only 1.2 m s21 (scalar) and 0.6 m s21 (resultant) and directions ranged
from 214.5 to 227.5 (resultant). Mean (resultant) wind direction for the WY 2005–2012 period was 221.7
with standard deviation 58.3 and peak gust at SASP was 21.4 m s21 during that period. This diminution of
wind speeds at SASP routinely occurs during storms as well as fair weather. For example, during a 20 h
storm from 27–28 February 2012, mean wind speed at SASP was 1.7 m s21. During the same storm, PTSP
mean wind speed was 11.9 m s21, fully seven times the average speed at SASP. PTSP logged a peak gust of
35.6 m s21 during the storm, almost four times the SASP peak gust of 9.0 m s21.
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Figure 4. Mean hourly wind speeds, by month, for WY 2005–2012 period at SASP, SBSP, and PTSP.
Unsurprisingly, winter is windier than summer at all three sites, albeit nominally so at SASP, and April is the
windiest month (Figure 4). Parsing wind speeds during hours with measured precipitation (at SASP) from
hours without precipitation reveals that hours with precipitation are windier during winter months at SBSP
and PTSP, but not during summer months; SASP wind data revealed no such differences (not shown).
4.2.3. Air Temperature
Air temperatures are monitored at all three sites, with a single sensor at PTSP and with stationary ‘‘lower’’
and ‘‘upper’’ sensors at SBSP and
SASP (upper sensors were added to
both sites in February 2006). Sensor
Status Workbooks (section 4.4.2)
document the mid-day height of
these sensors above the snow cover
surface at SASP and SBSP; snow
cover rarely accumulates at PTSP. In
the absence of available line power,
air temperature (and humidity) sensors are not mechanically ventilated.
Air temperature measurements may,
therefore, contain errors attributable
to radiative forcing, as described at
high-elevation sites [Georges and
Kaser, 2002; Huwald et al., 2009] and
in grasslands [Nakamura and Mahrt,
2005]. Figure 5 illustrates the seasonal range in SBB air temperatures
as well as systematic differences
from site-to-site.
Figure 5. Measured monthly (a) maximum, (b) mean, and (c) minimum air temperatures at SASP, SBSP, and PTSP for WY 2006–2012.
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Because of its exposed location,
rarely calm conditions, and generally
bare ground during winter, PTSP
data are considered the least terrain
affected and most representative
measured data available for ridgetop
air temperature (at 3756 m) in the
Red Mountain Pass locale and the
least likely to include errors from
reflected radiation warming of the
sensor. For WY 2007–2012, PTSP
water year maximum hourly air temperatures ranged from 16.2 to
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18.3 C, while minimums ranged from 224.7 to 248.1 C. PTSP mean water year temperatures ranged from
22.1 to 20.5 C during that period.
Cold air drainage from upper SBB into the sheltered SASP terrain pocket often results in colder overnight
low temperatures than at either PTSP or SBSP. Further, comparatively still air during daylight hours and
lower elevation at SASP often yields the highest daily maximum air temperatures observed among the
three sites, perhaps enhanced by thermal heating from the forest cover surrounding the SASP clearing. For
WY 2004–2012, SASP water year maximum hourly air temperatures (lower sensor) ranged from 19.7 to
22.3 C, while minimums ranged from 231.5 to 224.8 C. SASP mean water year temperatures ranged from
20.1 to 1.2 C during that period. While the terrain characteristics at SASP clearly do influence air temperatures maximums and minimums, the potential impacts of direct and reflected solar radiation on the sensors
cannot be dismissed (discussed further below).
SBSP’s location in the open, alpine portion of the basin results in less overnight pooling of cool air and less
still air during daylight hours than at SASP. For WY 2005–2012, SBSP water year maximum hourly air temperatures (lower sensor) ranged from 15.2 to 18.3 C, while minimum hourly temperatures ranged from 232.0
to 225.0 C. SBSP mean water year air temperatures ranged from 21.75 to 20.4 C during that period.
We evaluated the difference in temperature at SASP and SBSP over the WY 2005–2012 period as a composite function of time of day and time of year (Figure 6). After accounting for the elevation difference, SASP
was, on average, a little more than 2 C warmer than SBSP during mid-day, perhaps partially explained by
radiative heating of the sensor and differences in ambient ventilation, and about 1.5 C colder than SBSP at
night, likely due to cold air pooling.
In order to assess the potential magnitude of radiative forcing errors on SASP and SBSP temperature data,
we applied four different correction methods to hourly composite data for the WY 2005–2012 period (Figure 7). The resulting temperature corrections at mid-day vary from 0.6 [Nakamura and Mahrt, 2005] to 2.3 C
[Huwald et al., 2009] at SASP, and 0.4 to 1.5 C at SBSP. Two additional correction approaches were also
applied [Kent et al., 1993; Anderson and Baumgartner, 1998]. The most aggressive correction method is the
Huwald et al. [2009] method, which was developed at a Swiss glacier. The Nakamura and Mahrt [2005]
method was developed in a grassland environment and the Kent et al. [1993] and Anderson and Baumgartner [1998] methods were developed in an oceanic environment.
If we assume that the Huwald et al. [2009] approach is the most appropriate correction approach for snow
covered environments and apply it to both sites, we find that the SASP mid-day correction is about 0.7 C
greater than the SBSP correction (2.5 C–1.8 C 5 0.7 C). This does not account fully for the 2 C mid-day difference found in Figure 6. Thus, we cannot completely attribute temperature differences at SASP and SBSP
to just elevation and radiative heating effects. Further investigations into the site and environmental factors
influencing air temperature measurements at these sites may refine our understanding of those data at
SBB, and at other mountain study areas. Our hydrologic data set includes the measured temperatures as
well as four sets of corrected air temperature data employing the four correction methodologies described.
4.2.4. Humidity
Humidity is monitored at all three sites, with a single sensor at PTSP and with paired ‘‘lower’’ and ‘‘upper’’
sensors at SBSP and SASP, beginning in February 2006 when an upper sensor was added to both of those
sites. Humidity sensors are integrated into the same device measuring air temperatures at those sites. None
of the humidity (or air temperature) sensors are actively ventilated. Sensor Status Workbooks (section 4.4.2)
document the mid-day height of these sensors above the snow cover surface at SASP and SBSP; snow cover
rarely accumulates at PTSP. Data are initially captured as relative humidity but vapor pressure and dew
point temperature are also provided; all measures reflect the comparatively ‘‘dry’’ continental, highelevation location of SBB.
4.2.5. Radiation
4.2.5.1. Incoming Solar Radiation
Incoming solar radiation has been monitored continuously since January 2005 at both SBSP and SASP by
identical arrays of three pyranometers mounted at the top of their respective masts. Each site contains an
up-looking broadband pyranometer (0.305–2.800 mm) and a filtered near-infrared/shortwave-infrared pyranometer (0.780–2.800 mm), collecting hourly data. A second up-looking broadband pyranometer mounted
under a fixed shadow arm collects once-a-day measurements of diffuse incoming solar radiation in 2 min
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Figure 6. Differences in measured air temperature at SASP (3371 m) and SBSP (3714 m) as a function of time of day and time of year, averaged over WY 2006–2012. The mean difference between the sites over the entire study period was first removed before calculating the
hourly differences to account for temperature differences due to elevation.
arrays at/near solar noon. Figure 8 presents examples of midmonth, clear day values for incoming solar radiation at both SASP and SBSP.
In the absence of line power availability, radiometers are neither ventilated nor heated at either site. Consequently, up-looking radiometers at the well-sheltered SASP site are often obstructed by new snow accumulation and valid data are interrupted until the sensors can be swept clean. SASP up-looking radiometer
status (clear, obscured, swept) is logged in Sensor Status Workbooks—see section 4.4.2. Wind and an
absence of riming conditions at SBSP result in extremely rare occasions when up-looking radiometers at
that site are obscured and SBSP data are considered effectively continuous, in comparison. Of the two sites,
the alpine SBSP site experiences slightly less reduction, by terrain, of total hours of irradiance. The subalpine
Figure 7. Four air temperature corrections methods are applied to composite hourly air temperature measurements (lower sensor) at SASP and SBSP for the WY 2005–2012 period.
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Figure 8. SBSP downwelling radiation (direct solar, solar NIR/SWIR, and thermal) is shown for selected clear, midmonth days during WY 2012. With slightly different horizons resulting in
marginally decreased sky view near dawn and dusk, SASP data for the same days are only slightly lower.
SASP site experiences negligible shading by trees. Table 1 summarizes data for (complete) water years
2006–2012 for those sensors.
4.2.5.2. Incoming Thermal Radiation
Incoming thermal radiation has been monitored continuously since January 2005 at both SBSP and SASP by
pyrgeometers (4.5–42 mm) mounted adjacent to the up-looking broad band pyranometer at the top of
those respective masts. Because of its subalpine location, the SASP pyrgeometer field of view includes forest
cover and a higher fraction of terrain than the alpine SBSP pyrgeometer. During winter months, the SBSP
field of view contains very little exposed bare ground or tundra vegetation and most terrain is snow covered. Of the two sites, the alpine SBSP site experiences the least reduction by terrain of total hours of irradiance. Figure 8 presents examples of midmonth, clear day values for incoming thermal radiation at both
SASP and SBSP.
In the absence of line power, pyrgeometers are neither ventilated nor heated at either site. Consequently,
the up-looking pyrgeometer at SASP is often obstructed by new snow accumulation and valid data are
interrupted until it can be swept clean. Wind conditions and an absence of riming conditions at SBSP result
in extremely rare occasions when up-looking radiometers at that site are obscured, and valid SBSP incoming
radiation data are considered continuous. Up-looking radiometer status (clear, obscured, swept) is logged
in Sensor Status Workbooks—see section 4.4.2). Table 1 summarizes data for (complete) water years 2006–
2012 for those sensors.
4.3. Validation Data
4.3.1. Stream Discharge
Discharge is measured at the Senator Beck Stream Gauge (SBSG), a broad-crested, notched weir installed in
fall 2003 at the SBB pour point. Gauge rating was conducted during the summer of 2004 and valid SBSG
data begin in May 2005. Stream stage is measured with a pressure transducer installed in the pool immediately above the weir in late winter and removed in late fall. Water temperature and electrical conductivity
are also measured. Given the very low base flow rates observed in early winter, those sensors are removed
during overwinter months to prevent ice damage and then reinstalled as snowmelt discharge begins (Table
3). Using measurements collected upon reinstallation of sensors in late winter, overwinter discharge is conservatively estimated at 0.003 m3 s21 (0.1 cfs). Channel bed movement is routine during spring runoff, as
stage at the weir approaches and exceeds 30 cm (1 foot), partially filling the pool upstream of the weir. That
pool is restored to its nominal depth as soon as is practical after snowmelt runoff declines to a safe level.
Bed movement occurrences later in summer and fall are rare and brief. Total estimated cumulative SBB discharge for water years 2006–2012 ranged from 1,306,000 m3 (1059 acre feet) in 2012 to 2,082,000 m3 (1688
acre feet) in 2008.
To date, SBSG hourly and daily peak flows have occurred during the snowmelt season, enhanced by radiative forcing by dust-on-snow. High flows in summer and fall associated with rain events are also observed,
often within an hour of the rain event. Water years 2005–2012 hourly peak flows ranged from 0.40 m3 s21
(2007) to 0.75 m3 s21 (2010).
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Table 3. SBSG Operations Including Date When Automated Discharge Measurements Begin, Date of Peak Discharge, and Date Automated Discharge Measurements Are Stopped, by
Season
Begin Q Measurements
WY
2005
2006
2007
2008
2009
2010
2011
2012
Peak Q
End Q Measurements
Date
Q (m3/s)
Q (cfs)
Date
Hour
Q (m3/s)
Q (cfs)
Date
Q (m3/s)
Q (cfs)
15 May
5 Apr
15 Mar
15 Mar
4 Mar
7 Mar
15 Mar
11 Mar
0.0065
0.0025
0.0221
0.0019
0.0016
0.0014
0.0025
0.0012
0.230
0.090
0.782
0.067
0.055
0.049
0.088
0.043
23 May
27 May
2 Jun.
20 May
25 Jun
5 Jun
29 Jun
1 Jun
1600
1900
1900
2000
2300
1700
2000
1900
0.5932
0.4058
0.4046
0.5610
0.5927
0.7524
0.6179
0.4160
20.95
14.33
14.29
19.81
20.93
26.57
21.82
14.69
3 Nov
31 Oct
18 Nov
23 Nov
21 Nov
26 Nov
15 Nov
8 Nov
0.0080
0.0225
0.0094
0.0057
0.0026
0.0081
0.0055
0.0013
0.281
0.793
0.331
0.200
0.092
0.285
0.193
0.046
An analysis of the basin water balance during WY 2007–2012 was conducted to determine how annual precipitation is typically partitioned into streamflow, evapotranspiration, and storage (e.g., groundwater
recharge). Wind-corrected precipitation measurements made at the Swamp Angel site were assumed representative of the basin. Potential evapotranspiration (PET) was calculated at the Senator Beck site using the
Penman-Monteith equation and measurements of temperature, humidity, wind speed, and radiation. Over
this 6 year period, mean annual precipitation was 1260 mm, and approximately 50% of the annual precipitation was partitioned into streamflow (Figure 9). Three separate estimates of mean annual ET (Turc-Pike
equation, modeled sublimation with summer ET 5 PET, and Thornthwaite water balance estimate) ranged
from 23 to 46%, leaving a positive residual of 4 to 27% in the annual mass balance (Figure 9). Assuming
annual changes in storage contributes primarily to groundwater recharge, the range of residuals encompasses the estimate of Claassen et al. [1986], who found that there was a net export of water to deep
groundwater in the San Juan Mountains on the order of 12%. Unresolved sources of uncertainty in the calculated water balance include precipitation variability across the basin and blowing snow sublimation.
4.3.2. Snow Cover Depth and Snow Water Equivalent
Ultrasonic sensors monitor snow cover depth at SASP and SBSP and SWE is measured manually in conjunction with formal snow cover profiles collected adjacent to the SASP and SBSP instrument towers. Those formal snow profiles are performed monthly in early winter and weekly during late winter and spring at SASP,
and as feasible given avalanche conditions at SBSP (see section 4.4.2).
Due to wind redistribution of snow and terrain roughness, SWE and snow depth vary substantially between
the SBSP instrument tower and adjoining snow profile plot. Snow depth measured at the SBSP tower is typically less than that measured within the adjoining snow profile plot, due to wind effects. Maximum snow
depths (at 2400 h) at the tower
for WY 2005–2012 ranged from
1.37 m in WY 2012 to 2.91 m in
WY 2005. Maximum measured
SWE values in the adjoining snow
profile plot ranged from 618 mm
in WY 2012 to 1101 mm in WY
2005.
Figure 9. Mean annual water balance of the Senator Beck Basin based on measured precipitation (P), streamflow (Q), and meteorological data from WY 2007 to 2012. Windcorrected P measurements at SASP were assumed representative of the basin. Three estimates of mean annual ET are shown: (i) the Turc-Pike (Budyko-type) equation based on
potential ET (PET) and P, (ii) the sum of SNTHERM simulated sublimation (during snowcovered periods) and PET (during snow-free periods), and (iii) the Thornthwaite monthly
water balance model (calibrated to observed Q). The residual is calculated as R 5 P-Q-ET.
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SASP snow profiles are performed in the comparatively uniform and deeper snow cover
within the snow profile plot,
reducing the wind-induced spatial variability of snowpack properties between profiles. Snow
profiles and SWE measurements
are performed in a time series of
adjoining snow profiles within a
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portion of the plot, leaving the remainder undisturbed for visiting researchers. Maximum SASP snow cover
depths (at 2400 h) for WY 2005–2012 ranged from 1.91 m in WY 2012 to 2.90 m in WY 2008. During that
period, SASP maximum water year values at the SASP snow profile plot ranged from 542 mm SWE in WY
2012 to 999 mm SWE in WY 2011.
4.3.3. Reflected and Emitted Radiation
Reflected solar radiation has been monitored at both SBSP and SASP since January 2005 by identical arrays
of down-looking pyranometers mounted on an arm extending due south from their respective towers. Each
down-looking array contains a broadband pyranometer (0.305–2.800 mm,) and a filtered near-infrared/shortwave-infrared pyranometer (0.780–2.800 mm), identical instruments to those monitoring incoming solar
radiation. In combination, the difference in reflected radiation measured by these paired pyranometers enables parsing of snow grain size effects on snow albedo from the effects of contaminants such as dust in the
snow surface [Painter et al., 2007, 2012; Skiles et al., 2012].
A down-looking, infrared snow surface temperature sensor is also mounted on the same arm, collecting
‘‘spot’’ measurements of snow temperatures. The viewing field of these sensors does not include either the
instrument tower or vegetation in the vicinity of SASP. These infrared snow surface temperature data are
collected in lieu of down-looking pyrgeometer measurements, whose much larger field of view would
include nonsnow emitters of thermal radiation, including the host tower.
Inevitably, a shadow is cast by the arm containing these down-looking radiometers onto the snow surface
within the field of view of these sensors. The arm was designed to minimize the size of that shadow. The
extensive snow cover to the east, south, and west of these arrays enables a full complement of forwardscattering reflected radiation to reach the down-looking pyranometers.
4.3.4. Soil Moisture
Volumetric liquid water content (VLWC) was measured continuously by a single water content reflectometer
installed horizontally at 10 cm below the soil surface at both SBSP and SASP, in conjunction with other soil
sensors. Soil temperatures are also measured continuously at 210 cm depth at both sites and fall as low as
21.9 C at SBSP and 21.7 C at SASP in winter. All soil sensors were installed in July 2005 and have been
undisturbed since. As described earlier, the SBSP soil sensor array was installed in a shallow pocket of soil,
rich in organics and covered in alpine grasses. The SASP soil sensor array is deployed in well-draining
colluvium.
As with soil temperatures, substantial seasonal variations occur in volumetric water content at both sites
(Figure 10). As fall and early winter snow cover begins to develop, both sites exhibit modest (SASP) or large
(SBSP) declines in reported VLWC until stabilizing as snow depths approach 1 m. Although free water can
exist at subfreezing soil temperatures, it is unclear to what degree these declines in early winter VLWC are
the result of soil freezing or the result of soil moisture scavenging by the snowpack above, as perennially
strong vapor pressure gradients develop within the shallow snow cover in early winter [Sturm and Benson,
1997], or whether these declines in VLWC are a result of both processes.
During midwinter months, SASP VLWC increases slowly (Figure 10a) whereas VLWC is very stable at 10–12%
at SBSP (Figure 10b), perhaps indicating that soils are, indeed, frozen. As the snow cover begins to ablate
and becomes isothermal, SASP data show a steady increase in VLWC; SBSP shows more incremental
increases. At the final stage of snowmelt, SBSP VLWC data show a very rapid and large increase related to
observed ponding of snowmelt water near the soil array and sheet flow over the array. VLWC at both sites
shows varied behavior during the subsequent summer. SASP VLWC data show consistently large declines in
VLWC immediately after snow cover is lost, and continued drying during June (except 2011), the driest
month of the year. VLWC then fluctuates at SASP throughout the summer and fall monsoonal rain season,
typically at lower values than observed at SBSP.
4.3.5. Soil Temperature
Soil temperatures are continuously monitored at four depths at SBSP and at SASP, including the soil surface.
Soil conditions vary substantially between those sites. Colluvial gravels at the SASP site extend to a depth of
at least 2 m whereas conditions at the SBSP site range from exposed bedrock to shallow pockets of soil less
than 0.5 m deep in terrain depressions. SBSP soil temperatures are measured in one such pocket of soil,
with the lower of the three subsurface sensors at the bottom of the soil column, 25 cm below the surface.
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Figure 10. WY 2008 soil heat flux at the ground surface, snow depth, and soil volumetric liquid water content (VLWC) and soil temperature
at 10 cm below the soil surface are shown for (a) SASP and (b) SBSP and illustrate typical relationships observed each year.
The lowest soil temperature sensor at SASP is 40 cm below the surface. Dense grasses completely cover the
SBSP soil plot whereas bare soil is present within the SASP soil plot.
Seasonal patterns are evident in soil temperatures in this snow-dominated system (Figure 10). Following
diurnally fluctuating temperatures during summer and fall, accumulating snow in late fall begins to insulate
and moderate that variability. As the snow cover approaches 0.5 m in depth, soil temperatures stabilize just
below 0 C for the duration of snow cover. From 2005–2012, soil temperature minimums at the alpine SBSP
site ranged from 21.9 to 20.8 C at 210 cm depth and from 21.9 to 20.9 C at the 220 cm sensor depth.
At the subalpine SASP site, where soils are deeper, those minimums ranged, over the same period, from
21.7 to 20.2 C at 210 cm depth and from 21.0 to 20.2 C at the 220 cm sensor depth.
Upon complete snow cover ablation (date of snow disappearance), soil temperatures at all depths begin a
rapid warming trend. Water year 2006–2012 soil temperature maximums at the alpine SBSP site ranged
from 8.5 to 12.9 C at 210 cm depth and from 7.3 to 9.9 C at the 220 cm sensor depth. At the subalpine
SASP site, those summer maximums ranged, over the same period, from 21.3 to 28.1 C at 210 cm depth
and from 15.9 to 20.2 C at the 220 cm sensor depth.
4.3.6. Soil Heat Flux
Soil heat flux is monitored at 2–3 cm below the soil surface at SBSP, within a thick O (organic) soil horizon,
and at 2–3 cm below the surface at SASP, within the A (topsoil) horizon (no significant O horizon present).
As with soil temperatures, snow cover >0.5 m moderates diurnal fluctuations at the soil surface during winter, stabilizing near 0 W m22 net flux, but large fluctuations occur during snow-free months (Figure 10). In
any given water year, net daily heat flux is most strongly negative during fall months, prior to snow cover
formation, and most strongly positive following complete snow cover ablation, typically in June, and before
significant plant growth begins to shade the soil surface. For water years 2006–2012, soil heat flux maximums at the alpine SBSP site ranged from 71.5 to 144.6 W m22 and heat flux minimums ranged from
228.1 to 211.7 W m22. At the subalpine SASP site maximums ranged, over the same period, from 217.4 to
366.9 W m22 and heat flux minimums ranged from 2164.4 to 266.3 W m22.
4.4. Ancillary Data
4.4.1. GIS Descriptors
GIS data layers are available showing the SBB study area watershed boundary and study plot locations. Five
additional GIS data groups are compiled from publicly available data. Those groups include 10 m raster
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grids of a digital elevation model (DEM), vegetation coverage, geology, topography, and air photos. All GIS
data are in ArcGIS file format and can be accessed through snowstudies.org/GIS.
4.4.2. Sensor Status Workbooks
In addition to these automated measurements, CSAS collects observations that complement the data
described above. Sensor Status Workbooks document the mid-day height above the snowpack surface of
all air temperature, humidity, wind, and reflected/emitted radiation sensors. While the same distance above
snow cover can be calculated, by hour, based on subtracting the automated measurement of height of
snow by ultrasonic sensors from the height above bare ground of the sensor of interest (as given in the
SASP and SBSP metadata), these Sensor Status workbooks may expedite that process.
4.4.3. Snowpack Profiles
Finally, a time series of snow profiles are performed adjacent to both SASP and SBSP throughout each winter. Those profiles include manual measurements of snow cover SWE and bulk density, a snow cover temperature profile, snow cover stratigraphy, layer densities, layer grain types and sizes, snow wetness, and
other standard observations, and are available as PDF files.
5. Construction of Serially Complete Time Series
Given that SBB radiation measurements began during midwinter WY 2005, our serially complete data sets
begin with WY 2006. The data collected at the SBSP, SASP, and PTSP sites have short periods where instruments failed, and these periods of missing data were filled using data from surrounding stations. Missing precipitation data from SASP were filled (direct insertion) using Red Mountain Pass SnoTEL data, located 1.7 km
to the south. Missing temperature, relative humidity, and longwave radiation data were filled by building linear regression equations between measurements made at the SBSP and SASP plots, and using data from
one site to predict missing periods at the other site. Instances of simultaneously missing data at both sites
were extremely rare and resolved using data from the prior 24 h period. The shortwave radiation data were
first screened to identify periods where reflected shortwave radiation was greater than downwelling shortwave radiation (this can occur when the sensor is covered with snow, which is common at the sheltered
SASP site), and these data points were flagged as being suspicious—the missing and suspicious shortwave
radiation data were then also filled using linear regression equations constructed using data from the SBSP
and SASP study plots. Finally, missing wind speed data was filled using quantile-quantile matching among all
three CSAS sites (SBSP, SASP, and PTSP)—this was done because the intersite relationships are rather weak,
meaning that in-filling based on regression (slope near zero) provides near-constant in-filled values during
missing periods, and in-filling using the quantile-quantile matching technique provides more temporal variability. The serially complete time series for water years 2006–2012 are provided along with the original data,
including integer flags that determine if a data value is filled and the method used for filling.
6. Applications of SBB Hydrologic Data
6.1. Testing of Process-Based Snow Models
To illustrate briefly how the SBB data can benefit testing of process-based snow models, we simulated
snowpack at SASP and SBSP during water years 2006–2012 with the multilayer snow thermal model
(SNTHERM) [Jordan, 1991] and model parameters commonly found in the literature. We forced SNTHERM
with local hourly temperature, precipitation (SASP data applied to both sites), scalar wind speed, relative
humidity, incoming solar, incoming thermal, and reflected solar radiation. Here we used reflected solar radiation as a forcing, rather than validation data, in order to focus on model error due to model parameters
and structure.
Simulations and observations of SWE, snow depth, and bulk snow density are shown in Figure 11. At SASP,
SNTHERM generally underestimated SWE (Figure 11a) and snow depth (Figure 11c) every year. At SBSP (Figures 11b and 11d), SNTHERM matched observed SWE and snow depth reasonably in water years 2006,
2007, 2011 overestimated SWE during water years 2008 and 2009, and underestimated SWE in water years
2010 and 2012. These variations in modeled snow mass at SBSP may have been attributed to the lack of
wind transport in the model, which is important in alpine tundra. SBSP appears to be a site where wind
scour can reduce maximum SWE by up to 40%. SNTHERM simulated snow density reasonably well at both
sites, though it tended to overestimate density at SASP (Figures 11e and 11f).
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Figure 11. SNTHERM simulated and observed SWE, snow depth, and bulk snow density at (left column) SASP and (right column) SBSP during water years 2006–2012.
The snow surface temperature observations provided some evidence that the SNTHERM underestimation
of SWE at SASP was partially attributed to the modeled energy balance. The observations indicated that
SNTHERM had a consistent warm bias in the snow surface temperature, typically on the order of 1–3 C,
with maximum diurnal differences usually occurring in the late afternoon throughout each snow season
(not shown). A warm bias in surface temperature can cause premature melt, thereby partially contributing
to SWE underestimation. Multiple hypotheses could be considered to explain the warm bias in the model
(e.g., turbulent flux parameterization in a low wind environment, thermal conductivity, snow density parameterization, etc.), and further analyses will be reported in later publications.
6.2. Classroom and Field Education
Graduate and undergraduate hydrology classes use SBB data (H. P. Marshall, personal communication, 2009).
Numerous K-12 and university and college groups have also used both the SBB site and data during on-site
snow science field camps.
7. Summary and Conclusions
The snow-dominated Senator Beck Basin Study Area at Red Mountain Pass, in the western San Juan Mountains of southwest Colorado, has captured coherent hydrologic data sets for water years 2006–2012. SBB’s
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very high elevation, latitude, and continental location result in enhanced radiative forcing of alpine snowpack processes while, also by virtue of this location, the southwest North American monsoon dominates
summer weather.
Two principal sites within SBB, one well sheltered from wind in a subalpine meadow and the other fully
exposed to wind effects in the alpine tundra, capture representative data from the primary land cover types
within the 291 ha catchment. System forcing data collected at those sites include precipitation (subalpine
site only), wind speed and direction, air temperature and relative humidity, direct and diffuse solar radiation,
downwelling thermal radiation, and barometric pressure. Validation data from those sites include snow
depth, snow water equivalence (measured manually), reflected solar radiation, infrared snow surface temperature, soil temperatures, soil heat flux, and soil moisture. A stream gauge at the basin pour point collects
SBB discharge data, and a fourth site in nearby terrain collects complementary ridgetop wind speed and
direction, air temperature, and humidity data. Additional, supplemental field observations and data summaries augment this collection of data sets.
It is our hope that SBB data, and the study area facilities themselves, will complement other such hydrologic
data sets and research venues, such as the Reynolds Creek Experimental Watershed [Reba et al., 2011],
Niwot Ridge LTER site [Williams et al., 1999], and others, and contribute to improved understanding of
hydrologic process in snow-dominated mountain systems. We expect the SBB data will be valuable for
model testing and development in high-elevation areas, where multiple years of high-quality observations
of meteorological, hydrologic, and snow variables are exceedingly rare.
Acknowledgments
We thank the editors and our
reviewers for their thoughtful and
extensive suggestions, greatly
improving our presentation of this
data set. A substantial increment of
SBB instrumentation was acquired
through National Science Foundation
collaborative research award
ATM-0431955, in collaboration with
Tom Painter, PI. Additional SBB
development was supported by a
USDA-Forest Service Rural
Development, Forestry, and
Communities grant. References to
specific instruments or manufacturers
are for descriptive purposes only and
do not constitute an endorsement.
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