Blog from August, 2008

Starting 06:00 today, John, Khoung, Lou, and I started the reconfig to array 4.  This marks the end of array3.

- shutdown all adams except profile

- dropped horiz arrays

- split into 2 teams:

S&K: shifted sensors to east array; set EMT/up-guy system on bottom 13 [note new sonic installed for 13b; 5t replaced since array appeared bent]

J&L: dropped upwind 3-8

- lunch

S&K: mostly installed Pref tubing; moved downwind1&pressure1; cabled east side of array; rerouted power&e-net to upwind

J&L: dropped upwind 9-11; roughly placed trident tripods

Left at 18:00 -- turned on downwind1&pressure1 to check them out, but array is still close to ground.

A long day, but we're on schedule...

Still to do:

- horiz array:

    - cable west side

    - drill holes to set top EMT boom guys

    - raise and attach top boom guys

- tridents:

    - level/orient tripods

    - build last 2 trident masts

    - add sonics

    - erect

For my own sanity, I try here to document all the heights so far:

 (These are now updated with the array 4 values.  Not all of these make sense [different measurements when things weren't moved].  I'm working now to resolve them.)

*3/18/09, TWH added the height of the sonic measurement volume above the top of the boom (5.5? cm).

**Note that the 7m sonic was moved up "about 4-5 cm" on Aug 3 at 09:41 (see logbook entry)

 "-" means shouldn't have changed from last

"x" means value not needed

TRH at "5m" and "4m" were moved between array 2 and array 3, but measured during array 4.

final values to be used in bold

ref4 was 0.040m above ref3, but for the profiles, the reference was the top of the lowest sonic boom, which was 0.027m below ref3.

We plan to change from array 3 to array4 tomorrow.  Currently 60 hours, with 13 unstable for array3 (since Steve&I leveled it).

No <major> issues known.  <minor> issues are:

- The sonic that is now at 8m (formerly 7m) appears to have been high.  We'll replace it during the reconfig.

- Sonic at 5t appears to have top arm bent (though data look okay in daily plots?)  We'll replace it during the reconfig.

- Pressure system has pref that varies with heat convection -- presumably real.  We've been measuring pref using one of the 14 p' transducers (11b) so that this "error" can be removed from the data.

- We also have an independent 15th p' sensor, but it is only being recorded at coarse resolution at 1sps.

- Humidity on the TRH at 5.8m is still a bit odd, but it has been a very low priority.  (Steve and I already swapped sensors once.)

Wish us luck on the reconfig beginning at 6am tomorrow!  We'll start by dropping the horiz array and then split into two groups to work on both the horiz array and upwind array reconfigurations.  John and I tried erecting a trident today (without sonics) and it went <okay>, though we're still a bit nervous about adding an extra 50 lbs and $24,000 to it...

John and I started some preliminary work on array4:

- x-y dimensions from middle of east rohn tower to baseline pins for new tripods 10u, 7u, and 4u:

4u, x=3.055-1/2 rohn tube diam, y=7.778-6.379

7u: x=3.053-1/2 tube, y=9.066-6.379

10u: x=3.050-1/2 tube, y=10.374-6.379

Better estimates of y: 10u-7u= 1.288, 10u-4u=2.585

Existing 7u tripod is set up ~21.5cm upwind of baseline 7u pin (intended to be double the distance between mast and tripod center tube centers).

Confirmed that tripod 7u azimuth is close to perpendicular to crosswind line.

Shot array 4 reference to 7u tripod and east rohn tower -- ref 4 is 4.0cm above ref 3 (closer to ref 2).

To follow-up on the leak check yesterday (which showed a slow leak), I repeated this test today:

1033 P=1004.88 (pinched off)

1034 unpinched Pref (so I could read pressure easily) P=1007.29

1037 installed tee, P=1007.32

1038 blew in, P= 1029 dropping

1039 pinched entire array, P=1025 still dropping

1041 tighten tee, P=1021.5 still dropping

1043 pinched off 11b P=1018.9, still dropping

~1100-1113 reseated both reservoir endcaps with more Teflon tape and plumbers' grease.  Was able to screw in at least 3 whole turns more (due to grease lubrication)., P=1007.29 (had been open to outside)

1114 blow in, P=1048.3, dropping slowly

1117 P=1046.9, dropping slowly

1119 open 11b, P=1046.6, no obvious change in rate of dropping

1120 open entire array, P=1046.3, again no obvious change

1127 disconnect tee

1129 back to normal, P=1007.27

1134 backfill hole (again!) P=1007.6

Conclusion: reservoir had leak with 10min constant due to not-completely-seated endcaps.  They are now seated better, with a much smaller leak (though the decrease in P could have been moderated by a change in temperature, that should have increased P).

We still have the wind correlation to investigate...

John and Khoung just swapped 7m and 8m sonics.  Now 8m speeds are higher.  7m speeds are perhaps a bit low.  Now S/N720 is at 8m and 369 is at 7m.  (I just interrupted the data stream to determine this.)

I guess this means that 720 has been reading high all this time (and still is)?

6-4-09 (twh) swap occurred from 14:45 - 15:25

between 1440 - 1522, Khoung tried the pinch test again, removing all of the array of tubing.  During this test, the overall noise in p[ref].11b was significantly less, indicating that part (but not all) of the p' problems still are tubing related.

At 1525, he sucked on the reservoir and reconnected the (entire) tubing.  It appears that the tubing has a leak with a time constant of about 10min.  This was actually desirable(!), but indicates that we still have some sleuthing to do.

I finally been able to look at the data from when John removed the etherant yesterday.  During the entire 5-hour period, the speeds from 7m are higher than those at 8m.  Thus, the difference is not due to flow around the etherant.  (I had suspected that this would be the case several days ago when I noted that the speed difference (all u-component) was not a function of wind direction.)

John and Khoung are now swapping the 7m & 8m sonics to diagnose this problem further.

Still trying to work several problems:

1. P.0m is only 1Hz, only about same resolution as Pref, so not much help monitoring Pref after all.  Thus, change back to monitor Pref with 11b's 202BG
2. Data from P.0m yesterday showed Pref fluctuations.  Try to damp these by removing potential leak (old capillary leak) and add more steel wool.

~0900: opened ref volume

• - removed cap with capillary leak
• - stuffed more steel wool (about double) in this side
• - replace cap with solid cap
• - removed sample cap
• - stuffed more steel wool in this side
• - replaced cap

0925-0937: sat in this configuration to allow P.0m to monitor Pref

0937:

• - removed garden hose from CHATS system, noted that big hose fitting was somewhat loose, repaired with teflon tape?
• - changed P.0m from AHATS Pref to garden hose/Bedard
• - plumbed Pref back to CHATS system (using 11b.4.8m 202BG)

0955: covered up with dirt/space blanket again

To test the 8m sonic data, we removed the etherant at about 0800 today.  We reinstalled it about 1330.  Between these times, we were recording data from downwind1, profile, and pressure1 only on their usb drives.  Therefore, we downloaded all drives today.  However, our "spare" for upwind wouldn't mount (after we had successfully retrieved data from it off of profile or downwind1).  We're working to revive the drive (my Mac was able to reformat it with a FAT filesystem), but in the meantime, upwind's old pocketec was reinstalled.

The covars are still rerunning on the merged data, so I haven't yet been able to check on whether the sonic was affected.

At 1512, I pinched off the entire reference pressure tubing so that both Pref and P.0m measured just the reference volume.  (It turned out that P.0m's RS232 connector fell off, so we didn't get data from it for any of these tests .)

At 1618, I opened the above, but pinched off lines to only connect 6b.

At ~1745, I opened the above connecting the entire tubing system, but pinched off Pref (after reconnecting the P.0m signal).

A first look at the Pref data shows no difference -- the pressure fluctuations are still coming from the volume?

We just made several more measurements:

1. Heights of sensors on the horizontal array (between top of boom and Ref 3 mark, to check if the arrays are level and at the same heights):

 Looks like everything is within a 4mm range of each other -- pretty good to me!.

2. Distance between end of boom clamps and boom pins is 3.5cm for the PAM clamps and 3.2cm for the ASTER clamps.  Thus, the longitudinal spacing would be 3mm less than I reported in an earlier message [I'll try to revisit this and actually produce numbers.]

3. x-y spacing between upwind and downwind arrays:

x between middle of downwind Rohn tower and middle of square upwind masts: 512.5-1.6+3.1=5.140m (10u) and 511.3-1.6+3.1cm=5.128m (3u).

y between middle of boom for 1b and center of square mast for 11u: (12.76-2.585)-(5.84-0.30)=4.64m

4. Distance perpendicular to array to berm: 18.62m to 11u, 10.85m to 3u

AHATS (sometime)daily status 8/3/08

Staff: Militzer, Oncley, Nguyen, Tudor&Verstraete with ISS.
John replaced Steve yesterday.  Lou arrived the day before and
Laura leaves tomorrow.

Temps: 99F/57F yesterday

Activity highlights:
- Changed sensor to monitor Pref to free up the fast-response sensor to
make a completely independent measurement.  All measurements appear to
agree...
- I noticed dust devils in the pressure signal yesterday -- these
probably are the first ever with a tight array of pressure measurements!
- We <think> we've completed documentation of array 3.

For more details, see the ahats logbook at https://wiki.ucar.edu/display/ahatslogbook

Good wind direction:
array#3 (jul 29 12:30-present) now has 40 hours (8 unstable, 32 stable).
We're planning on switching to array #4 on Tom's schedule on 6-7 Aug.

Local data storage: (we downloaded everything on 30 July)
------------------
upwind:/dev/sda1 57685532 7961492 49724040 14% /var/tmp/usbdisk
downwind1:/dev/sda1 57685532 8849776 48835756 15% /var/tmp/usbdisk
downwind2:/dev/sda1 57685532 10443500 47242032 18% /var/tmp/usbdisk
profile:/dev/sda1 57685532 5801844 51883688 10% /var/tmp/usbdisk
pressure1:/dev/sda1 3897204 1800328 2096876 46% /var/tmp/usbdisk
pressure2:/dev/sda1 3897204 1857176 2040028 48% /var/tmp/usbdisk

aster:/dev/sdb1 721075720 368028044 353047676 52% /media/isff2
isff: /dev/sdc1 1922890480 544537872 1280675404  30% /media/isff15

Pressure:
--------
(+/- = ~1 std deviation among variables at the same height)

11.b now measuring p with the 202BG connected between the
Bedard port and CHATS reference.  P.0m [poor name] now is the
portable Paroscientific standard with reasonable resolution, but
low sampling rate.

p: ok, +/- 0.03 mb
p'p': ok, +/- 0.0005 mb^2
w'p': ok, +/- 0.001 m/s mb
t: ok, 2 degC
Pref: ok, glitch yesterday ~noon when opened to install new sensor

P: ok

Profile: [,select.p]
--------
glitches on 8m when we replaced it today (0900-0930)

T: ok
RH: sensor that is now at 5.8m is strange.  Since sonics are now at this
level, we may work to fix it.

diag: ok
samples.sonic: ok
spd: ok?, 8m still lower than 7m sometimes.  (Even after the swap today!)
Maybe the WiFi antenna is bothering it...
dir: ok
w: ok
tc: ok, 8m low by ~0.3 degC? (related to the speeds being low as well?)
w'w': ok
u*: ok, some imaginary values with light winds
sigma_w/u*:
w'tc': ok
h2o: normal, 2 g/m^3 offset from dat("Q"), except in afternoon.
w'h2o': ok, 0.03 m/s g/m^3 at midday
co2: ok, 15-20 mmol/m^3 (some nights have large values, some don't [last
night]).  Presumably related to shallow nocturnal boundary layers,
but I haven't gone through the sodar data yet.
w'co2': ok, -0.01 m/s mmo/m^3 at midday

Upwind (hts=4.8): [,select.u]
----------------

diag: ok
samples.sonic: ok
spd: ok, +/- 20 cm/s
dir: ok, why isn't this better now that angles are shot??
w: ok, +/- 5 cm/s
tc:  ok, +/- 0.2 deg, biases somewhat larger
w'w': ok, +/- 0.005 m^2/s^2  (30 min avg for second moments)
u*: ok,  +/- 2 cm/s, some imaginary
sigma_w/u*:
w'tc': ok, +/- 0.01 m/s degC
tc'tc': ok, +/- 0.05 degC^2

Downwind Lower (hts=4.8): [,select.b]
------------------------

diag: ok
samples.sonic: ok

spd: ok, +/- 20 cm/s
dir: ok, why isn't this better now that angles are shot??
w: ok, +/- 5 cm/s, leveling helped!
tc:  ok, +/- 0.2 deg, biases up to +/-0.8
w'w': ok, +/- 0.005 m^2/s^2  (30 min avg for second moments)
u*: ok,  +/- 2 cm/s, some imaginary
sigma_w/u*:
w'tc': ok, +/- 0.01 m/s degC
tc'tc': ok, +/- 0.05 degC^2

Downwind Upper (hts=5.8): [,select.t]
------------------------

diag: ok
samples.sonic: ok
spd: ok, +/- 10 cm/s, 3t outlier
dir: ok, +/- 2 deg, why isn't this better now that angles are shot??
11t outlier
w: ok, +/- 5 cm/s, leveling helped!
tc:  ok, +/- 0.2 degC, offsets up to 0.6 degC
w'w': ok, +/- 0.01 m^2/s^2  (30 min avg for second moments)
u*: ok,  +/- 2 cm/s, som imaginary
sigma_w/u*:
w'tc': ok, +/- 0.01 m/s degC
tc'tc': ok, +/- 0.05 degC^2

----------------------------------------------------------------

This is the list with viper on the top and the power supply on the bottom.

Also see  https://wiki.ucar.edu/display/ahatslogbook/2008/07/17/GPIO+boards+in+pressure+systems

Profile boom heights from top of boom (inside of clamp on the other side) to the ref 3 mark: