Began January 9, 2013

Following the SCP project, we tested each sonic in a zero-wind enclosure within the EOL temperature chamber, measuring wind component offsets and sonic temperature errors over the nominal range -30 C to 55 C.  The procedure is to warm the chamber up to 55 C and then slowly decrease the temperature linearly to -30 C, followed by slowly increasing the temperature back to 55 C.  The zero-wind enclosure holds two sonic heads on their sides (with the v-axis vertical) and electronics, one above the other and separated with a horizontal layer of rigid blue foam.  On the cool-down cycle, the atmosphere around the top sonic is unstably stratified (cold enclosure lid above warmer air) and that around the bottom sonic is stably stratified (cold enclosure bottom below warmer air).  The opposite is true during the warm-up cycle.  Both the wind component data and the sonic temperature data have significantly less variance when the air is stably stratified, and thus we use data from the bottom sonic during the cool-down cycle and data from the upper sonic during the warm-up cycle.

The following table shows wind component offsets as okay if the u and v offsets are less than +/- 4 cm/s and the w offsets less than +/- 2 cm/s (between - 20 C and 30 C).  If the zero wind offset exceed these thresholds, the table lists the temperature range of the over-limit offset and the largest amplitude of the offset.  The plots of offsets versus temperature can then be examined to determine the exact nature of the offset.

The sonic temperature corrections are listed as the slope and offset of a linear fit (between -20 C and 30 C), Tc = offset + slope*tc.sonic, where Tc is calculated from temperature, relative humidity, and pressure measured in the zero-wind enclosure.  Rudy also calculated the sonic temperature correction (again from -20 to 30 C) by interpolating the speed-of-sound temperatures of the hygrothermometers to the height of the sonic.

Note that we have repeated the laboratory tests on SN0923 and SN0833 to determine the reproducibility of the results.   The velocity component offsets agree within less than 2 cm/s and the temperature offsets agree within 0.06-0.10 C and the slopes agree within 0.2-0.3%, for an overall agreement of no worse than 0.1 C.

SCP Site

EOL cal

Sonic

Owner

Cal date

u

v
 

w

tc offset
(degC)

tc slope

rms dev
from fit (degC)

Ah1

1/09/13

0923

UC Davis (KT)

15aug12

ok

7 - 23 C;
-7.7 cm/s
@ 14 C

ok

0.10
0.84

1.0223
1.011

0.07
0.18

repeat calibration

1/10/13

0923

"

"

ok

7 - 23 C;
-7.7 cm/s
@ 14 C

ok

0.04

1.0204

0.06

Ah2 ("glitching in high winds")

1/09/13

0833

UC Davis (KT)

29aug12

ok

ok

ok

0.69
0.96

0.9971
1.001

0.08
0.13

repeat calibration

1/10/13

0833

"

"

ok

ok

ok

0.79

0.9938

0.08

Ah2 (after 10/19/12@10:15)

2/04b/13

0671

ISFS

28jun12

ok

ok

ok

-0.13
1.04

1.0172
1.003

0.10
0.17

Aph3

1/14/13

0743

RAL (Gochis)

05jul12

ok

ok

ok

0.15
0.95

1.0206
1.005

0.11
0.17

A4

2/06b/13

1120

ISFS

19jul12

ok

23 - 30 C;
-6.4 cm/s
@ 30 C

ok

-0.19
1.01

1.0193
1.01

0.06
0.19

Ah5

1/14/13

0732

RAL (Gochis)

09jul12

ok

ok

ok

0.86
1.19
1.18

1.0004
1.008
1.003

0.11
0.15
0.16

Ah6

2/07/13

0800

ISFS

19jun12

ok

ok

ok

0.08
1.23

1.0156
1.008

0.08
0.19

A7

2/04/13

0673

ISFS

18jul12

ok

ok

ok

1.10
1.11

0.9979
1.008

0.09
0.18

Ap8

1/11/13

0176

UC Davis (KT)

22aug12

ok

ok

ok

0.50
1.09

1.0272
1.003

0.05
0.22

Ap9

2/05/13

1121

ISFS

08dec11

ok

ok

ok

-0.63
0.7

1.0137
1.006

0.10
0.23

Ap10

2/05/13

0677

ISFS

17jul12

ok

ok

ok

1.16
1.12

0.9995
1.006

0.10
0.20

Ars11

2/07b/12

0674

ISFS

13aug12

ok

ok

ok

0.96
1.03

0.9977
1.008

0.08
0.17

Ap12

2/01/13

0855

ISFS

12sep12

ok

ok

ok

0.95
0.91

0.9975
1.009

0.11
0.19

A13

1/31b/13

0745

RAL (Gochis)

09jul12

ok

ok

ok

1.21
1.06

0.9978
1.011

0.11
0.19

Ap14

2/06b/13

1124

ISFS

19jul12

ok

ok

ok

0.89
1.03

1.0048
1.014

0.08
0.21

A15

2/05b/13

1122

ISFS

08dec11

ok

ok

ok

-0.44
0.66
 

1.0161
1.029

0.07
0.50

A16

1/30/13

0740

RAL (Gochis)

28aug12

ok

ok

ok

-1.88
0.97

0.9979
1.007

0.06
0.18

A17

2/01/13

0856

ISFS

31jan12

ok

19 - 30 C;
-10.4 cm/s
@ 30 C

29 - 30 C;
2.2 cm/s
@ 30 C

-0.62
0.55
0.69

1.0145
1.001
0.985

0.10
0.17
0.26

A18

1/15/13

0744

RAL (Gochis)

05jul12

ok

ok

ok

0.41
0.96

1.0210
1.014

0.13
0.21

repeat calibration

2/07b/13

0744

"

"

ok

ok

ok

0.01

1.0227

0.06

A19 (broken joint;
removed 9/22/12)

 

0672

ISFS

17jul12

NA

NA

NA

NA

NA

NA

A19 (installed 9/24/12)

1/11/13

0178

UC Davis (KT)

9sep12

ok

ok

ok

0.72
0.26

1.0001
1.007

0.10
0.20

C.1m

1/07/13

0200

UC Irvine (JRP)

27jun12

ok

ok

ok

-0.04
0.83

1.0192
1.007

0.10
0.21

C.2m

1/07/13

0197

UC Irvine (JRP)

03jul12

ok

ok

ok

0.74
1.26

0.9900
1.003

0.07
0.21

M.05m

1/15/13

1455

USFS (WJM)

29aug12

ok

ok

ok

0.66
1.1

1.0004
0.992

0.08
0.23

M.1m

2/07/13

1117

ISFS

08dec11

29 - 30 C;
4.3 cm/s
@ 30 C

16 - 27 C;
4.6 cm/s
@ 21 C

ok

1.06
1.12

0.9976
1.001

0.10
0.17

M.2m (until 9/27/12@15:03?)

 

0538

ISFS


NA

NA

NA

NA

NA

NA

M.2m

2/04b/13

0536

ISFS

27jun12

ok

ok

ok

0.80
1.27

0.9993
1.000

0.08
0.15

M.3m

2/01b/13

0540

ISFS

28mar12

27 - 30 C;
4.5 cm/s
@ 30 C

ok

ok

-0.20
-0.08

0.9930
0.994

0.15
0.15

repeat calibration

2/08/13

0540

"

"

27 - 30 C;
4.6 cm/s
@ 30 C

ok

ok

-1.87

1.0125

0.09

M.4m

1/29/13

0738

RAL (Gochis)

29aug12

22 - 28 C;
-4.5 cm/s
@ 25 C

18 - 25 C;
-4.3 cm/s
@ 21 C

ok

-0.26
1.1

1.0197
1.002

0.11
0.14

M.5m (until 9/27/12@15:03?)

 

0671

ISFS

 

NA

NA

NA

NA

NA

NA

M.5m

2/06b/13

0537

ISFS

21jun12

ok

ok

ok

-0.19
1.05

1.0134
1.003

0.09
0.14

M.10m

2/01b/13

1119

ISFS

09aug12

ok

ok

ok

-0.12
1.28

1.0137
1.000

0.16
0.21

repeat calibration

2/08/13

1119

"

"

ok

ok

ok

1.22

0.9969

0.09

M.20m

1/31b/13

0741

RAL (Gochis)

3jul12

ok

ok

ok

-0.09
0.43

1.0199
1.008

0.09
0.16