Technical Report - Cooperative Agreement H8590100013
Devils Postpile National Monument – Scripps Institution of Oceanography
For period 27 Sep 2010 - 31 Dec 2011
D. Alden, D. Cayan
Scripps Institution of Oceanography, UC San Diego
26 March, 2012
Hydroclimate Weather Station
Scripps Institution of Oceanography (Scripps) has been measuring the absolute
pressure (water level + atmospheric pressure) and temperature of the middle fork
of the San Joaquin River since 2004 and collecting climate data in Devils Postpile
National Monument (DEPO) since 2005. River water level and temperature data are
sampled at 30 minute intervals with a Solinst Levelogger, which is deployed in the
river near the site of the old pump house just north of the campground. The stream
pressure and temperature data, along with a suite of weather observations, are
logged with a Scripps DL4-Met Hydroclimate Weather Station located in Soda
Springs Meadows near the DEPO Ranger Station. The hydroclimate weather station
sensor suite includes air temperature at two heights on the tower, humidity,
barometric pressure, solar radiation, fuel moisture/temperature, and soil
moisture/temperature measured at 10cm and 50cm below ground.
Maintenance of the hydroclimate weather station and the Levelogger was
performed during visits to DEPO in the period covered by the Cooperative
Agreement on 9 Oct 2010, 7 Jul 2011, and 12 Oct 2011. During each visit data were
downloaded and sensors were checked. Plots of the data returned can be found in
in Figure 1 through Figure 5. All sensors performed well with the exception of fuel
temperature. Data from this sensor was unusable between 21 Dec 2010 and 7 Jul
2011 due to broken wires caused by heavy snow load. The fuel temperature probe
was replaced during the July 2011 field trip. The heated tipping bucket was also
exchanged with a freshly calibrated unit in July 2011 as part of a routine
replacement schedule.
Time-Lapse Camera Systems
Three time-lapse camera systems were built and installed in October 2011 near Soda Springs Meadow
with the following views: 1) looking west across the meadow from the hydroclimate weather station
tower, 2) looking upriver near the site of the USGS gauging station, and 3) looking north towards Soda
Springs meadow from the footbridge to Minaret Falls. A map showing the camera locations is shown in
Figure 6.
The systems couple a Canon EOS Rebel T2i digital SLR camera with a Scripps DL4-Camera
controller as shown in Figure 7. AC power is used for the camera at site 1 allowing the camera to be
connected to the Internet. From site 1 an Eye-Fi Wireless Memory Card streams the images to a website
at Scripps 14 times a day. A sample transmitted image is shown in
Figure 8. Sites 2 and 3 rely solely on battery power. To extend the battery life at
these sites photos are taken only twice a day and stored internally for retrieval at
the end of the winter season. The set of images from the cameras will be
downloaded during our first visit to DEPO after it opens in 2012.
The camera at site 1 transmitted images through early January 2012 and then was
offline until March 2012 becoming operational again for a period of a week. No
images are currently being sent. The cause of the outages is unknown but may be as
a result of a number of factors including but not limited to issues with power, the
wireless network that the camera uses to connect to a cellular router, the physical
connection to the camera, or the DL4-Camera controller. Our technical team will not
get a chance to fully trouble-shoot the system until after the winter season.
The current status of autonomous systems is unknown. However, we are
coordinating with NPS staff to check on all the cameras when they ski into DEPO for
the April 1 snow survey.
Communications Link
Data from the hydroclimate weather station and images from the camera at site 1
are transmitted to a server at Scripps via the Internet using a Digi Connect WAN 3G
cellular router operating on the Verizon cellular network. The cellular router has
been in place since 2009 and has provided a reliable link for real-time data from
DEPO.
A private wireless network is used to transmit images from the camera to the
cellular router. During the fall of 2011 there were a few periods when the camera
experienced a loss of network connectivity. The cause of the connectivity failures is
unknown. Further investigation will take place after the winter season. By design
the camera forwarded all queued images when network connectivity resumed.
Cold Air Pooling Temperature Network
Cold-air pooling (CAP) occurs in areas of complex terrain where cold air collects,
forming a thermal inversion wherein temperatures in a lens air near the ground is
cooler than the air at higher elevations, either at the ground or in the atmospheric
column above the lens of cool air. It has been suggested that areas with CAP may
serve as a refuge for certain species. The DEPO staff has developed a network of
mini-sensors to monitor temperatures at relatively fine scale over the DEPO
landscape to investigate timing, depth, extent, and degree of cooling that
characterize CAP formation (DEPO Technical Report, provided by J. Winters, written
by D. Scott). Here we provide a view of CAP from some initial analyses from the
data collected during 2010-2011 that were provided by the DEPO staff.
To conduct this analysis, two pairs of sensor records, were selected—1) a higher
elevation site (123 at 2573m) and a lower elevation site (302 at 2334m) , and 2) a
vertically-oriented “canopy” pair, separated by 20 meters within the same tree
(Figure 9). The lowest sensor in the canopy pair was taken at 10m because the
lower sensors exhibited spells of time when they were covered with snow (1 meter
height) or simply not recording (5 meter height). Later we will investigate the
canopy temperature records in more detail, but the results from the 10 meter and
30 meter pair are still informative. The series of temperature records from the lowhigh elevation sensor pair and from the canopy sensor pair is plotted for May
through October in Figure 10. The data obtained, from a tidbit sensor at the low
elevation site and from iButton temperature sensors at the high elevation site and
the two canopy heights, was sampled at one hour or one half hour intervals, as
programmed by the DEPO staff when they deployed or serviced the sensors.
Because the temperature observations were downloaded most recently in
September 2011, this plot presents a sewn-together record of May-August 2011
combined with September-October 2010; the last two months were inserted to
obtain more samples from the warm half of the year.
In each of the frames of Figure 10, the higher sensor of the pair is shown by the blue
line and the lower sensor is shown by the black line. As expected, both pairs of
sensors exhibit a similar pattern of seasonal and intra-seasonal temperature change
during the 6 month interval that is shown. In the low-high elevation pair, it is clear
that there are several spells of days during which the low elevation sensor is cooler,
by several C, than the high elevation sensor; it is not so clear from Figure 10 how
the canopy temperatures differ. The differences in temperature low-minus-high
are plotted in Figure 11 for the two pairs of sensors. These plots clearly show that
thermal inversions (cool air pooling or CAP) often occurs during the warmer half
the year, with the greatest amount of cooling achieved in the night and early
morning hours. Comparing the two pairs, the largest cooling occurs in the lower
valley location relative to the higher elevation site, but that there is also cooling at
the low vs high canopy site. The cooling at the 10m canopy sensor relative to the 30
m sensor is not as intense as that exhibited by the low-high station pair, but the
canopy cooling would very likely be greater if a lower height (than 10m) sensor
record was employed. The low-high pair commonly experiences of 5C cooler
temperatures at the low elevation site, and cooling in excess of 12C is seen during
particularly strong events. The greatest cooling occurred during September (2010)
and appears to heighten in intensity through the summer period, but it is not known
if this is a peculiar to this short period of sample or whether this is a more general
seasonal occurrence—a longer sample is needed to test this. Importantly, the
pattern of variability of the lower elevation (height) cooling is similar for the canopy
pair as the low-high pair.
Seen from the low-high sequence, cooling tends to occur over several day spells,
presumably owing to the multi-day duration of large scale meteorological patterns.
The atmospheric circulation pattern, composited over several days with high
cooling is shown in Figure 12 (upper), indicating that a broad cell of high pressure is
seated over the region, which would feature clear skies, low winds, low humidity,
and relatively high daytime temperatures. This would then promote radiative
(infrared) nighttime cooling, stable, layered atmosphere near the ground and little
mixing, which would allow cool nighttime temperatures to collect in low elevation
valleys and pockets. Interestingly, an analogous composite of the atmospheric
circulation during days with greater cooling at high vs. low elevation sensors
exhibits a pattern that is nearly opposite, with lower than average pressure over the
region, which would tend to be associated with cloudy skies, higher winds, higher
humidities, and lower nighttime radiative heat loss.
Acknowledgements
We would like to recognize the exceptional support of this project by NPS staff at
DEPO. Their efforts throughout the planning and implementation phases have made
this project a success.
Figure 1. Water level (blue) and temperature (green) observations from
September 2010 through October 2011, recovered from Solinst Levelogger. Note
that water level has not been corrected for barometric pressure, which introduces
minor offset in water pressure readings. The San Joaquin River level reached
nearly 3 meters during early July peak flow in 2011, a result of melting of the heavy
snow accumulated during winter and spring 2011.
Figure 2. Soil moisture and soil temperature from September 2010 through
October 2011, recovered from DL4-Met Datalogger
Figure 3. Fuel moisture (blue) and fuel temperature (green) from September 2010
through October 2011, recovered from DL4-Met Datalogger
Figure 4. Precipitation (upper) and solar radiation (lower) from Sept. 2010
through Oct. 2011, recovered from DL4-Met Datalogger. Precipitation is measured
by two rain gages: heated gage (blue) melts snow when AC power is on, and
unheated gage (red) does not, resulting in a large difference in the recorded
amounts. Solar radiation may be affected by shading from snow or ice during short
periods of the year. Spikes in solar radiation are likely as a result of cumulus solar
irradiance reflectance (J.L. Laird, Harshvardhan 1997). On partially cloudy days
reflections from sides of clouds can contribute to an increase in received radiation
that exceeds clear-sky values.
Figure 5. Barometric pressure (upper), temperature (middle), and humidity
(lower) from September 2010 through October 2011, recovered from DL4-Met
Datalogger.
Figure 6. Time-lapse camera deployment sites at DEPO
Figure 7. Automated time-lapse camera system.
Figure 8. Camera image, Site 1 at the DEPO Hydroclimate Weather Station
Figure 9. Location of a segment of the DEPO temperature and humidity sensor array.
Red circles show the selected low-high elevation station pair--the high elevation site
(123 at 2573m) and low elevation site (302 at 2334m). The yellow circle shows the
selected canopy (vertical stack) site on the western edge of the floor (503 at 2315m).
Note the suffix for the site locations indicates the height of the sensor in meters.
a
b
Figure 10. Temperature (oC) at high and low elevation sites (a) and high and low
canopy sites (b). The top panel shows temperature from the selected low elevation site
(black; site 302 at 2334m) and high elevation site (blue; site 123 at 2573m). The bottom
panel shows temperature from a canopy (vertical stack) on the western edge of the
floor (site 503) for a lower sensor (black 10m) and a higher sensor (blue; 30m). Plotted
temperatures are from one hour or half hour samples. Based on data availability, data
are shown for May-August of 2011 and for September-October of 2010.
a
b
Figure 11. Temperature difference (oC) between selected high and low elevation site
sensors (a) and high and low canopy (10m minus 30m) sensors (b) . Sites are the same
as shown in Figure 9 and plotted in Figure 10. Black bars indicate times when the low
elevation temperature is warmer than that of high elevation sensor and red bars
indicated times when the low temperature is cooler. Based on availability, data are
shown for May-August of 2011 and for September-October of 2010.
a
b
m
Figure 12. 500mb height anomalies (m) during days in May through October (warm
season) when lower elevation night temperatures (as shown in Figures 1 and 2) are (a)
cooler than higher elevations and (b) warmer than higher elevations. The 500mb height
composites are based on nights (8pm to 8am) when at least 75% of the observations at
the lower elevation site 302.01 are (a) cooler or (b) warmer than the observations at the
higher elevation site 123.01. The daily compositing tool at the NOAA/ERSL site was used
to create the maps.
References:
John L. Laird, Harshvardhan, Analysis of cumulus solar irradiance reflectance (CSIR)
events, Atmospheric Research, Volume 44, Issues 3–4, June 1997, Pages 317-332,
ISSN 0169-8095, 10.1016/S0169-8095(97)00016-1.
Project Description and SOP for cold air-pooling (CAP) near Devils Postpile NM, CA.
Technical Report written by David Scott 2010.