This dataset here contains only the observations from the network of ultrasonic anemometers and associated aspirated thermohygrometers consisting of 12 stations total grouped into 3 x 4 stations (SUSAN ABC, 1234). SUSAN stands for ‘SUbcanopy Sonic Anemometer Network’. Station locations for the WS1 ARCFLO experiment were selected to capture the greatest extent of spatial variability of the airflow. The first subset of stations (SUSAN A1,A2,A3,A4) were deployed near the flux tower near the mouth of the WS1, the second subset of stations (SUSAN B1,B2,B3,B4) were deployed about 200m upslope in the vicinity of the creek, and the third subset of stations (SUSAN C1,C2,C3,C4) in close proximity to the confluence of the two smaller creeks in the upper part of WS1 approx. 1 km upstream.
With the exceptions of SUSAN A2, which was mounted on WS1 tower and SUSANs C1 and C2, which were mounted on a temporary 40ft tower, all SUSAN subunits were mounted on adjustable tripods to facilitate sonic leveling. SUSANs A and B were powered by line power whereas SUSAN C was powered by four AGM 12-volt batteries. These batteries were recharged every 4 to 6 days with a portable generator.
Sonics were connected to loggers with 300 ft of AGU 24 communications cable. Data was transmitted to the Campbell Sci. Cr3000 data loggers through RS-485 protocol and translated to RS-422 by CommFront 485-422 TTL converters contained within the logger weatherproof box. With this deployment configuration we aimed to capture individual submeso features as they propagated up or down the watershed past various sensors (see deployment map).
Each subset of SUSAN (SUbcanopy Sonic ANemeometer) is comprised 4 Young 8100VRE UltraSonic Anemometers and 4 Vaisala HMP Thermohygrometers logging to a Campbell Scientific CR3000 Micrologger. Each of three SUSAN arrays is named by convention starting with a letter, ’A’, ’B’, or ’C’ and each subunit is numbered 1 through 4. All Vaisala HMP thermohygrometers are model 155 except for units C3 and C4 which are model 45C. All thermohygrometers are housed in an electrically aspirated radiation shield.
For this experiment three SUSAN systems logged data at 20Hz and also logged data averaged at 1- minute intervals. Data was stored on 2-gigabyte SanDisk Extreme III flash cards by Campbell Scientific NL-155 Compact Flash Modules attached to each logger. Periodically, the flash card would be swapped so data could be uploaded from the flash card to a PC and then converted to ASCII format using the Campbell Scientific Card Convert program (a subunit of LoggerNet).
The sonic anemometer raw data (20 Hz) were processed post field collection using the Matlab based program BMMFLUX, written and developed by PI Christoph Thomas. During the processing, raw (20 Hz) data are checked according to instrument data quality flags and user-assigned plausibility thresholds: %% Plausibility limits for wind components (m/s) and sonic temperature (deg C) of raw signals: plaus_u = [-30,30]; plaus_v = [-30,30]; plaus_w = [-30,30]; plaus_T = [-30,50].
The observations from the thermohygrometers were not processed with BMMFLUX, but samples were aggregated into 1 min averages of air temperature and vapor pressure by the data logger. These logger-produced data were then combined with the 1-min averaged data output of BMMFLUX to yield the data described here.
Note: In the variable label, ‘unrotated’ means recorded in the native sonic anemometers coordinate system (Ux, Uy, Uz as indicated in the manual).
The label ‘rotated’ means that the winds were rotated into streamlines coordinate most suitable for micrometeorological purposes by performing two rotations (1: mean cross-wind equals zero m/s, 2: mean vertical motions equals zero m/s, for details see: Wilczak, J.M., Oncley, S.P., Stage, S.A., 2001. Sonic anemometer tilt correction algorithms. Boundary-Layer Meteorol. 99, 127–150.). Wind directions were also orrected for the instrument azimuth. The results are cylindrical coordinates commonly known as ‘wind speed’ and ‘wind direction’. The wind directions were not corrected for magnetic declination (With a latitude of 44.2 N and longitude of 122.2 W the declination was given by (http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp) on 7/27/2012 is 15 degrees, 35 minutes = 15.583 degrees).
