Field Notes

<--2012-08-16 09:30:00 | 2012-08-23 11:45:00-->

Mayberry: 2012-08-18 10:00:00 (DOY 231)
Author: Jaclyn Hatala
Others: Erich Matthes

Summary: LI-7700 CH4 concentrations were way off, disconnected and reconnected power to LI-7700 and readings are OK

Yesterday when looking at the Mayberry permanent tower data I saw that the CH4 density was way off starting around 4pm on DOY 210 (July 28) and CH4 density has been bad since then (about 20 days total). Values were an order of magnitude smaller than they ought to have been (densities around 0.004 mmol/m3 rather than 0.08 mmol/m3 - 0.1ppm instead of 1.9ppm). All other values for the LI-7700 (RSSI, temperature, and pressure) were fine. No idea what event precipitated the bad values, since it was about 2 and a half days after the field visit on July 26th when values were fine.

I drove out to the permanent tower this morning, arriving around 10am local time with dissipating clouds and a slight breeze from the west. Connecting to the LI-7700, I confirmed that the readings were bad - instrument was reading 0.1ppm CH4. RSSI, temp and pressure were all good. The first thing I tried was disconnecting and reconnecting the power to the LI-7700, and everything was fine after that - CH4 density was reading 0.08 mmol/m3 (1.9ppm). The power switch possibly rebooted either internal LI-7700 software or some part of the laser that was hung up? I will call Licor on Monday morning to ask them about this.

After restarting the LI-7700, I pulled the USB key to make sure the data were recording properly, and indeed all looked good after the power switch. I also stopped by the Mayberry portable tower and checked data collection (including a check to make sure the data was recording on the USB key) and all looked good.

Checking the CH4 density every field visit should definitely be a priority to make sure this doesn't happen again. And I'll update everyone on what Licor says about what might have made this happen, so that we can minimize our risk of this happening in the future.

2 photos found

MB_autocam_20120818_0645.jpg ( 2012-08-18 06:45:02 ) Full size: 1920x1440
Crow on tower cross arm