This table summarizes the sonic and prop vane azimuths. Azimuth angles were shot relative to magnetic north with the datascope.
date |
stn |
whom |
sonic (measured,magnetic) |
sonic Vazimuth (calculated,true) |
prop (measured,magnetic) |
prop azimuth (calc,true) |
notes |
|---|---|---|---|---|---|---|---|
6/29 |
1 |
Kurt, Rus |
356.3, 356.7 |
267.8 |
92.3, 92.6 |
273.8 |
|
|
|
|
|
|
|
|
|
6/24 |
2 |
Gordon, Dan |
357.0 |
268.3 |
93.3 |
274.6 |
|
6/29 |
2 |
Kurt |
357.0 |
268.3 |
93.3 |
274.6 |
good agreement with 6/24 |
|
|
|
|
|
|
|
|
6/29 |
3 |
Kurt |
353.0 |
264.3 |
93.2 |
274.5 |
|
|
|
|
|
|
|
|
|
6/24 |
4 |
Gordon, Dan |
354.3 |
265.6 |
92.6 |
273.9 |
|
6/29 |
4 |
Kurt |
353.5 |
264.8 |
88.9 |
270.2 |
prop disagrees (-3.7 deg) with 6/24 |
7/5 |
4 |
Dan, Kris |
354.2 |
265.5 |
|
|
Magnetic declination = 1.3 deg E
sonic: Vazimuth = measured + declination - 90
Vazimuth is the direction that the sonic V axis is pointing, and is the rotation angle of horizontal wind components from instrument to geographic coordinates.
prop: azimuth = measured + declination + 180
prop azimuth is the angle that is added to the wind directions measured by the propvane, so that they are relative to true north.
1 Comment
Dan Rajewski
Dan and Russ took the 10m prop azimuth for NCAR4 on July 22 around 12:45 CDT. The measured angle was 94.9 degrees so the azimuth angle calculated would be 276.2.
The method in holding the data scope required that scope be set on one of the rungs of the ladder because the corn had reached its maximum height. The wind moving around the top leaves of the canopy also made difficulty in keeping the 10m prop in view of the cross hairs of the data scope. I would suggest taking an average of all three readings for 6/24,6/29, and 7/5. The 10 m prop was not checked on July 5 because only the orientation of the sonic anemometer may have changed when Kris and I swapped out the krypton sensors. If need be I can get another measurement during Steve's visit to the site on Monday.