Field Notes

Twitchell Alfalfa: 2013-09-18 11:45:00 (DOY 261)
Author: Cove Sturtevant
Others: Joe, Laurie

Summary: Dug water well next to radiation boom, too difficult to reach water table. Swapped out flux instrument pole.

Twitchell Alfalfa
2013-09-18

We arrived about 11:45 PDT, meeting Laurie at the site who we had dropped off earlier to begin LAI, spectral, and clip plot measurements. It was windy, sunny, and warm (25 C). Joe worked on digging a water well next to the radiation boom while I checked the tower. The well was very difficult to dig. The top layer of soil was dry with a moist layer below, but then the soil was extremely hard and dry, looking very mineral. I helped Joe later and we got the hole down to a meter with still no water table. The home-made extension Joe brought for the auger wasnt going to cut it below that level, so we put the PVC pipe in and will try to go deeper next time. Frank might have an auger we can use.

We also swapped out the flux instrument pole for one with a larger diameter so it would fit in the mount without shims. Swap successful. One of the bolts for the mount was now too short and we didn't have any slightly longer ones so MacGyver made a super long bolt fit making the thickest washer ever (see pic). Tower is at the same height. Sonic aligned to true north. I took a measurement of the 7700 orientation w.r.t. the sonic: middle of 7700 path is 30 cm from middle of sonic path at 86 N (true).

7500 readings:
CO2 = 380 ppm (same after cleaning)
H2O = 460 mmol m-3 (same after cleaning)
SS = 73.8% (74.7% after cleaning)
T = 26.1 C
p = 101.1 kPa
sos = 348.7 m s-1

7700 readings:
CH4: 1.92 ppm (same after cleaning)
RSSI: 35% (85% after cleaning)
Reservoir was full

MET looked good.
Radiation looked good.

2 photos found

20130918TA_CS_thickwasher.JPG ( 2013-09-18 12:33:50 ) Full size: 1296x968
Fancy bolt job