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3D1_s



Sonic Anemometer at Air-Sea Interaction Tower

Wind speed is calculated from a 3-axis sonic anemometer (Solent Model R2) located at the ASIT, 41 19.500' N, 70 34.000' W. The height of the anemometer is 18.4 meters above mean sea level. This type of anemometer measures the wind speed with no moving parts. Instead, it measures how long it takes two pulses of sound, moving in opposite directions, to travel a known distance. The pulses are created and detected using pairs of transducers and are inaudible to humans. The time of flight is shorter for the pulse moving with the wind, so the difference in time is a measure of the wind speed between the transducers. Three pairs of transducers are used to measure the wind speed and wind direction.

Most of the data parameters include valus for the mean and median value as well as the standard deviation of the variable. The table below shows the field name suffix used to differentiate amoung the different values:

Field name Description
_mean The mean value of the variable over the averaging period
_m50 The median value of the variable over the averaging period
_std The standard deviation of the variable over the averaging period
_length The number of valid data points collected over the averaging period

Here is the list of field names:

Field name Description Units
Year The year the data were collected n/a
Yday Decimal year day UTC, January 1 at 00:00 is 1.0
MO The month the data was collected UTC
DA The day the data were collected UTC
HH The hour the data were collected UTC
MM The minute the data were collected UTC
SS The second the data were collected UTC
lrec_3d1 Total number of records collected during averaging period n/a
wspd_3d1_mean mean wind speed
wdir_3d1 mean wind directions degrees from North true
w_3d1 vertical velocity m/s
tson_3d1_mean air temp from speed of sound Deg C
winst_3d1 ??Instantaneous Wind Speed m/s
wspd_3d1_m50 median wind directions degrees from North true
tson_3d1_m50 median air temp from speed of sound Deg C
wspd_3d1_std std along-wind windspeed m/s
v_3d1_std std cross-wind component m/s
w_3d1_std std vertical wind component m/s
uv_3d1_var covariance m^2/s^2
uw_3d1_var covariance m^2/s^2
vw_3d1_var covariance m^2/s^2
wT_3d1_var covariance vertical wind speed with air temp ??
wspd_3d1_length # recs between 0 100 and < 4*std from mean n/a
tson_3d1_length # recs between -25 and 35 and < 4*std from mean n/a

Calibrations: R2 SN:080 - ??? (12V 422 coms - 4800 Baud) R2 SN:0123 - 11/24/04


7/21/05 - Swapped out SN080 (dropping out) with Model R2 SN0123 (11/24/04 calibration)