Field Notes

<--2013-02-14 10:30:00 | 2013-02-28 10:40:00-->
Other sites visited today: Twitchell Rice | West Pond | DWR Corn | Sherman Island
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Mayberry: 2013-02-21 12:00:00 (DOY 52)
Author: Joe Verfaillie
Others: Cove

Summary: LI7700 lost line lock - reset, 7700 calibrated, 7500 reporting bad chopper temp - could not fix, replace set of TCs at Tule Tower, removed surface DO.

Mayberry
2013-02-21

I arrived about 12 noon with cove. It was clear, cool and sunny. The earlier breeze died and it became warm in the sun. The Levees were mowed sometime before last weekï¿½s visit. The tules and cattails are all very brown.

When we arrived the 7700 had lost its line lock and was reading about zero. We manually forced a line lock by lowering the laser temperature from 30.7 to 30C and then reset it to automatic. Then we calibrated the 7700 sn 0224. We cleaned the mirrors and RSSI rose from 54 to 85. It was relatively well calibrated, zero was off by about +11ppb and span was off by about +10ppb.

Then we looked at the 7500. It was reporting a bad chopper temperature and the CO2 and H2O readings seemed low. We called and talked to Licor, but they were not much help. They suggested unplugging and re-plugging all the cables, then finally to flex the head cable. This changed the chopper temperature voltage from near zero to about 5V for a bit but did not seem to affect the densities. Ultimately we left it in place to record the methane flux at least. Next time out we need to be prepared to swap the cable and possibly the whole 7500/7550 set.

Next we went out to the Tule tower to swap out a set of thermocouples and check on the surface DO. The DO was reading low and did not climb when exposed to the air, so we removed it for a check in the lab. The open water set 1 of the TCs has been lying flat on the bottom for a while due to a broken stick. We removed this set completely and installed a new set of eight TCs. The old set had TCs at +10, +4, +2, -2, -4, -8, -16, and -32cm. The new set has TCs at +50, +40, +30, +20, +10, 0, -16, and -32cm. However we could not get the stick in to the right depth so these depths are about 6cm higher than they are supposed to be. [Note by Daphne Szutu 2019-03-04: Based on the data, these depths seem to be in the wrong order. The depths are -32, -16, 0, +10, +20, +30, +40, +50cm.]

The wireless link from the main tower to the tule tower worked perfectly.

5 photos found

MB_autocam_20130220_1345.jpg ( 2013-02-20 13:45:02 ) Full size: 1920x1440
Ship on the River