Field Notes

<--2013-02-21 12:00:00 | 2013-03-14 10:40:00-->
Other sites visited today: Sherman Island | Twitchell Rice | West Pond | DWR Corn

Mayberry: 2013-02-28 10:40:00 (DOY 59)
Author: Cove Sturtevant
Others: Laurie

Summary: Re-installed surface DO probe. Removed lower DO probe for testing. 7500 readings okay, but replaced main cable anyway. 7700 lost line lock again, loose power cable found.

Mayberry
2013-02-28

Permanent tower
We arrived about 10:40 PST. There were clear skies, and it was warm with a good breeze. There was a lot of cottony cattail material all over everything and actively blowing through the air. I cleaned the tower instruments and downloaded data while Laurie went into the water to collect water samples, install surface DO probe #4 in the channel. Some issues with the tower and DO probe noted below.

7500 readings:
CO2: 380 ppm
H2O: 560 mmol m-3
agc: 32.5
When Joe and I came out last week, the densities were too low and the chopper temperature flag was raised. After talking to LI-COR last week, we ended up leaving the instrument and brought a replacement cable and 7500/7550 this week. However, when I got to the tower the densities seemed fine, the chopper flag was no longer raised, and the chopper temp voltage was 2.15 (normal). Since LI-COR thought last week that the main cable from the 7550 to the 7500 might be bad, I swapped out the cable anyway but left the rest of the system as-is.

Current 7700 readings:
CH4 = 0 ppm (no line lock), 1.9 ppm after reset
RSSI = 20-40 variable (cottony material on spider webs wavering in the path), 80 after cleaning
The reservoir was full.

The line-lock on the 7700 was lost when I checked the instrument. This was also the case last week. I reset it and then watched it waver and lose itself. I rebooted the instrument and it happened again, then it remained steady after I reset it a final time. I noticed that the secondary block temperature was “set” at 30 °C and the “actual” was also near this value when the line lock was good, but then the actual block temperature fluctuated to low values (10-20 °C) when the line lock lost itself. Although the actual block temperature subsequently returned to normal, the line lock remained lost until reset. I called LI-COR for suggestions. They instructed to check for a loose power cable. What do you know, it was loose! I don’t think we have moved this instrument or touched the power cable since August. Beware the slow fingers of sabotage in the Delta climate.

After the 7700 was online and stable, I noted that a warning icon was present next to the 7700 s/n in the 7500 program. The warning informed me that the readings were not synchronized, and to check the clock settings. I did so and everything was fine, all settings were usual. The 7500 clock was on automatic and the 7700 clock was slaved, both on Pacific Standard time. I watched the two clocks change together identically. Perhaps this is a spurious flag, but we should keep an eye on the data.

Out in the water, Laurie successfully reinstalled the upper DO probe (s/n #4). It read ~31 after install. Per instructions from Sara, she tried to get calibration readings for the lower DO probe (s/n #7) by holding it out of water, shaded, and upside down so that the membrane was facing up. The readings were supposed to increase to atmospheric, but they decreased instead and continued to decrease when replaced in the water. She pulled the probe for testing in the lab. Note: no jumper cable to ground was installed in its place, and the reading was ~21 (similar to the DO in the Tules) after removing. This data needs to be deleted in the MET.

2 photos found

MB_autocam_20130227_1415.jpg ( 2013-02-27 14:15:03 ) Full size: 1920x1440
Hawk on 7700