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The attached 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 on the tilt plot.

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.

date

height (m)

lean

leanaz

w offset (m/s)

elevation residual rms (deg)

offset residual rms (m/s)

notes

Mar 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

 

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

 

These tilts appear to be due to the slope of the terrain, slopeing down in the -u direction, in the direction that the sonic boom points. If the terrain was not sloping, these would be a "backwards" tilt, i.e. the booms not drooping from the tower but angling upward.

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)
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