AUTHORS:
Dr. Jason Beringer #
Dr. Matthew Sturm %
Dr. F.S. Chapin III @
Dr. Larry Hinzman &
# School of Geography and Environmental Science
PO Box 11A
Monash University
Clayton, Victoria, 3800
AUSTRALIA
Ph: +61 3 9905 9352
Fax: +61 3 9905 2948
Email: Jason.beringer@arts.monash.edu.au
%USA-CRREL-Alaska
P.O. Box 35170
Ft. Wainwright, AK 99703-0170
United States of America
Ph: 907-353-5183
Fax: 907-353-5142
@ Institute of Arctic Biology
311 Irving I Bldg
University of Alaska Fairbanks
Fairbanks, AK, 99775-7000
USA
& University of Alaska Fairbanks
Water and Environmental Research Center
P.O. Box 755860
Fairbanks, Alaska 99775-5860 U.S.A.
Phone 1-907-474-7331
Fax 1-907-474-7979
e-mail ffldh@uaf.edu
web http://www.uaf.edu/water/
DATA SET OVERVIEW:
A single flux tower was constructed by Jason Beringer and operated during the
snowmelt period at Ivotuk by Matt Sturm. Data processing and analysis was undertaken
by Jason Beringer. Climate data were collected by Larry Hinzman. Sensible, latent
and CO2 fluxes were measured along with net radiation from Larry Hinzman.
SITE:
Data were taken at the Ivotuk MOSS site. MOSS (Sphagnum sp.) Dominanted Moist
Acidic Tundra (MOSS)
Site I4
Latitude 68 28.8237984
Longitude 155 44.6473464
Elevation 552.839 m
Slope=1.24 o
Aspect=312 oMagnetic
Measurement period 8/5 to 14/6 year 2000.
DATA COLLECTION AND PROCESSING:
Surface energy exchanges
A single tower wasdeployed to obtain microclimatic and eddy-covariance measurements
in order to characterize the radiation, energy and trace gas exchanges during
the snowmelt period. Measurements of radiation, energy and trace gas exchanges
were made at over tundra using the eddy covariance technique [Eugster et al.
1997].
We used a 10 m tower. Radiation measurements were made as close as practical to the top of the towers to minimize the potential of shading from above and to maximize the surface area within the effective sensor footprint [Schmid 1997]. Eddy-covariance measurements were made at varying heights above the vegetation (Table 1). Three dimensional wind velocities were measured using a 3-D ultrasonic anemometer (Gill Solent, model HS) and were co-ordinate rotated [McMillen 1988]. Turbulent fluctuations of CO2 and H2O were measured using a closed path infrared gas analyser (Licor, model LI-6262). The CO2 and H2O time series were lagged against the sonic temperature series so that they were in phase with each other. Scalar quantities were linearly detrended and bell tapered [Stull 1988]. A 3 mm internal diameter "Bev-A-Line" intake tube was used for the gas analyzer with an aspiration rate of approximately 7 L.min-1 that ensured turbulent flow in the sample line [Philip 1963]. In addition, 1.5 m of insulated copper tubing was placed inline to minimize temperature-induced density fluctuations [Leuning and Judd 1996]. The observations were logged at 10 Hz to a nearby laptop PC.
The enclosure was heated using an electric lightbulb and the intake air was warmed by using a heating strip along a 1m long copper air intake tube. The tube also reduced temperature fluctations.
The w'T' cospectra for each site followed the idealized cospectra [Kaimal et al. 1972] and the w'CO2' and w'H2O' were spectrally corrected following [Eugster and Senn 1995]. Spectral correction factors for water vapour were less than 1.4 during daylight hours. The energy balance closure ((Q/Rn) was generally less than 15% as a fraction of net radiation during the daylight hours (Table 1) indicating satisfactory measurement techniques and confidence in the measured fluxes [Eugster et al. 1997].
Climate data was collected by Larry Hinzman and further details on these measurements may be found in the JOSS data archives
The time system used here is local Alaskan Daylight Time (ADT), which is (UTC -8 Hours). Throughout this paper the term daily refers to the 24-hour period from midnight to midnight and daytime refers to the period when net radiation is positive (10:00-18:00). Solar noon at Council was around 15:00.
DATA FORMAT:
These files are saved in two formats *.xls being an Excel4 worksheet and *.txt being a comma delineated text file.
The files contain one or more of the following parameters and the parameter names are given at the top of each column. The following table gives the parameter definitions.
Note that in each flux file there is a VALIDY column which is a flag to indicate good quality data. Data with a 8 is identified as good data.
TYEAR -9999 8.3 Year
TDAY -9999 8.3 Day of Year
THOURMIN -9999 8.3 Hour_Minute
TTIME -9999 TIME1 Excel format date/time
JOSS_TIM -9999 19.0
IMEANWD -9999 8.3 Mean sonic wind direction
IMEANWS -9999 8.3 Mean sonic wind speed (m.s-1)
IMEANT -9999 8.3 Mean sonic virtual air temperature 2m (oC)
IMEANH2O -9999 8.3 Mean water vapor content LI6262 (g.kg-1)
IMEANCO2 -9999 8.3 Mean CO2 concentration LI6262 (ug.g-1)
I_VALIDY -9999 8.3 Valid data code where 8 is good data
I_H -9999 8.3 Sensible heat flux (Wm-2)
I_LE -9999 8.3 Latent heat flux (Wm-2)
I_FC -9999 8.3 CO2 flux (ug.g-1.m-2.s-1)
I_TA_3M -9999 8.2 Hinzman met station Air temp 3m (oC)
I_SNOW_D -9999 8.2 Hinzman snow depth Ivotuk (cm)
INCID_SW -9999 8.0 Hinzman Incoming shortwave radiation (Wm-2)
REFLECT -9999 8.0 Hinzman Reflected shortwave radiation (Wm-2)
NET_RAD -9999 8.0 Hinzman Net radiation (Wm-2)