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Comment: Migrated to Confluence 5.3

The attached following plots were made with our Splus function, plot.tilt, that does a linear least squares fit to find the plane of mean flow, and plots the wind vector elevation angle vs azimuth. The planar fit becomes a sine wave curve on the tilt plot.

See EOL sonic tilt documentation.

From a long term plot of the sonic "diag" value, I chose two periods where the the values were consistently very small. plot.tilt discards 5 minute wind averages when "diag" is above 0.01, or more than 1% of the data has a non-zero CSAT3 diagnostic value.

For the upper sonics at 16, 30 and 43 meters, the minimum wind speed used for the fit was 1.0 m/s. For the lower sonics at 2 and 7 meters, the minimum wind speed was set to 0.5 m/s. This didn't have much effect on the fit, however.

Feb 21 to April 4, 2011

Section
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Column

2 meters
Image Added

Column

7 meters
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Column

16 meters
Image Added

Column

30 meters
Image Added

Column

43 meters
Image Added

Aug 5 to Aug 17, 2011

Section
bordertrue
Column

Image Added

Column

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Column

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Column

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date

height (m)

lean

leanaz

w offset (m/s)

elevation residual rms (deg)

offset residual rms (m/s)

notes

Mar Feb-Apr 2011

2

4.1

-1.7

0.03

2.9

0.04

 

 

7

5.9

8.2

0.07

5.7

0.08

 

 

16

5.9

-0.2

-0.01

3.1

0.011

 

 

30

4.5

-2.1

0.02

2.7

0.014

 

 

43

4.3

-5.9

0.04

3

0.02

 

Aug 2011

2

5.6

-6.3

0.04

2.6

0.03

 

 

7

9.1

-1.4

0.06

7

0.09

large tilt value, too much scatter for good fit

 

16

5.9

4.6

-0.01

3.6

0.01

 

 

30

4.3

-0.9

0.00

3.6

0.01

 

 

43

4.4

-5.5

0.01

4.2

0.02

 

Tom says that typical sag droop of sonic booms results in 1 to 2 degree tilts, which would be 180 degees different in azimuth from the above values.. The sonic booms point up-slope from the tower, so the approximate 5 degree tilts seen here are a combination of the boom "droop" and the slope of the terrain.

These tilts appear to be due to the slope of the terrain, which is downward in the -u direction, in the direction that the sonic boom points. If the terrain was not sloping, these would be a "backwards" boom tilt, i.e. the booms not drooping from the tower but angling upward. They generally agree on an approximate 4. 5 degree slope tilt of the terrain sonics relative to the sonicsmean flow, except the 9.9 degree tilt for the 7m sonic in Aug 2011.

Gallery
includemanitou_mar2011_2m.png, manitou_mar2011_7m.png, manitou_mar2011_16m.png, manitou_mar2011_30m.png, manitou_mar2011_43m.png
columns5
titleMarch 2011

...

There appears to be some local "disturbance in the force", causing a pinched effect at 2 meters, and to a lesser extent at 7 meters, so that winds straight into the sonic have an additional downward inclination.

There seems to be good agreement at 16 meters and above between the two fits. I suggest using the average of the two values for those levels. Perhaps we need to look at more data for 2 and 7 meters.

...

Code Block
languagenone
dpar(start="2011 2 21 00:25",end="2011 4 4 07:26",coords="instrument")
dpar(hts=2)
plot.tilt(flag="diag",ellim=10,spdmin=0.5)