Field Notes

Field visit on February 27^th, 2003
Dennis Baldocchi and Tess Krebs

Tonzi

Arrived Tonzi site 10:00 am, intermittent cloudy with rain showers and cool. Saw nice coherent structures in w’ and photosynthetic signal despite low sunlight.

The laptop computer on the tower system was 10 minutes slow. We used a Garmin GPS to reset the clock. Also reset laptop computer time on the floor system.

The aspirator on the understory temperature sensor was working. On the tower, we checked ambient temperature and relative humidity against hand-held measurements made inside the aspirator. The initial T_ambient and RH with the original installed sensor were 10.97 and 68.28% respectively. The handheld comparison yielded 10.8 degrees and 61% relative humidity. The temperature was okay to within 0.1-0.2 degrees and the relative humidity was significantly off. Discussed having Laurie Koteen and Tess Krebs calibrate temperature and relative humidity and then swap sensors.

Water vapor was observed off scale due to wetness, then came back on scale during observation, all other measurements were fine. Large water vapor variance.

On the floor system, in the .23X file, the 8^th channel reads 0. Same file as soil moisture. Also, one of the soil moisture probes is off, reading about 300 while the rest were above 800.

CR23X6 on tower had failed. Swapped it out, but we lost data. sn ???? came off and sn ???? went on. Will need to fill gaps with Vaira data.

Serial #28 sonic. Lat 38 N 24.797 Lon 120 W 57.047

Average grass height 4.29 cm +- 2 cm. Took leaf nitrogen samples.

Soil Moisture Measurements

Vaira

Arrived Vaira 3:00 pm. It had cleared by then. The solar panel batteries were somewhat drained (the yellow LED was on) and the solar amps were kind of low.

As we did at the Tonzi site, we compared the in situ ambient temperature and relative humidity with a hand-held sensor measured inside the aspirator. The original T_ambient was 11.94 and the original relative humidity was 67.9 percent. The values with the hand held were 11.8 degrees and 67 percent, respectively. So both temperature and relative humidity seemed acceptable.

The soil heat flux plate 3 had been miswired, as L1 H2 and was changed to L1 H1. The signal went from offscale to onscale.

All the watchdog signals looked good.