Field Notes

<--2010-09-02 05:27:00 | 2010-10-07 10:00:00-->

Tonzi: 2010-09-10 12:00:00 (DOY 253)
Author: Hideki Kobayashi
Others: Siyan

Summary: Extensive LAI, canopy, and radiation measurements.

Effect of single scattering in gap fraction measurements

Hideki Kobayashi

10/20/45 degree view cap measurement

On September 10, 2010, Siyan and I went to Tonzi site. It was clear, no clouds during the daytime. We got to the field site at around 11:00 PST (noon DST), and started measurements at about 1:00 PST (2:00 DST). During the measurements, solar zenith angle changed from 35.9 (1pm) to 52.6 (3pm). Solar azimuth angle changed 26 degree from south (1pm) to 63 degree from the south (3pm).

I set up two LAI-2000 sensors at the top of the flux tower. “Baldocchi” sensor was used for 10 and 20 degree view cap measurements and “Gong” sensor was used for 45 degree view cap. The sensors’ view caps were oriented to the exact east direction. The “Baldocchi” sensor was also used for PAR measurements using LiCOR PAR sensor (SN Q29882, MULT;-148.81, tcoff: 0.0036, Units micromols-1m-2 per microA, cal data10 JUL 01). This PAR sensor is quite old and we have not recalibrated it. Later, we will compare it with Kip and Zonen’s one. The PAR sensor was installed near other radiation sensors at the top of the tower. I installed this PAR sensor as far from the tower frames as possible. Diffuse PAR measurements were performed by making shadow using a paddle. The first 3-4 PAR readings and the last PAR 3-4 readings of “Baldocchi” sensor are diffuse PARs at the top of the tower (so almost no obstacles in the sky). 270 degree sky radiation measurements were also conducted for two LAI-2200 measurements before I started the measurements with 10/20/45 degree view cap. In these measurements, the sensors are pointed to the north direction to block the direct sun beam. So I am sure that the beam is not contaminated in the 270 degree view cap measurements. I used the sensor with SN3002 for 20 and 45 degree measurements and the sensor with SN3004 for 10 degree measurements

For 10/20/45 degree measurements, I first took one above reading (“A”) at the top of the tower, and started below canopy measurements (“B”). We have three north-south transects. Each transect has 11 points with a 30 m interval. During the first (the most eastern side) and the second (middle) transect measurements, I kept every 30m sampling. In the last transect (the most western side), I measured roughly every 2m. This 2m sampling is not exact 2m because we take the measurements ever 2 foot-steps. However, we believe that it is close to 2m. All samplings were exact east. I used flags and a compass to determine the east direction, which Siyan made flags correctly before we started the measurements.

Individual tree experiment

I chose 22 trees for the gap measurements. I chose the trees as diverse as possible (from small to large trees). I used a 10 degree view cap. Each time, I first took one above reading at an open space, and then took below data along a crown every about 1m (every one foot step). At the same time, Siyan took vertical view photos using a digital camera with a bubble level. The locations of these photo measurements are completely matched with LAI-2200 measurements.

Gap fractions were also measured by digital photos. I used RICOH R8 digital camera. All photos are vertical view (view zenith angle=0.0). The field of view of the photo is 42.133 degree in vertical direction and 56.178 degree in horizontal direction.

Filename and description

- 10D1400.txt
Below reading for 10 degree view cap. The first and the last data “A” are the above canopy reading measured at the top of the flux tower. There is another “A” reading, which is 26th data. This is NOT real above reading. This “A” splits two different sampling intervals. The gap data from the 2nd to25th were measured every 30m and from 27th to 186th were measured every 2m interval. Reference above reading is the file “Baldocchi_100910.txt”

- 20D1600.txt
Below reading for 20 degree view cap. I forgot to take “A” sample to split the 30m interval experiment and the 2m interval experiment, but the number of total samplings are the same as “10D1400.txt”. So the gap data from the 2nd to25th were measured every 30m and from 26th to 185th were measured every 2m interval. Reference above reading is the file “Baldocchi_100910.txt”

- 45D1400.txt
Below reading for 45 degree view cap. The first and the last data “A” are the above canopy reading measured at the top of the flux tower. There is another “A” reading, which is 26th data. This is NOT real above reading. This “A” splits two different sampling intervals. The gap data from the 2nd to25th were measured every 30m and from 27th to 186th were measured every 2m interval. Reference above reading is the file “Gong_100910.txt”

- 270D-02.txt
270 degree view cap measurements. I took tree samples at the top of the flux tower. This data corresponds to 45D1400.txt

- 270D-04.txt
270 degree view cap measurements. I took tree samples at the top of the flux tower. This data corresponds to 10D1400.txt

- 270D-02-2.txt
270 degree view cap measurements. I took tree samples at the top of the flux tower. This data corresponds to 20D1600.txt

- Avobe10D20D_100910.txt
Above canopy readings for 10/20 degrees

- Gong_100910.txt
Above canopy readings for 45 degree

- Total_diffuse20100910.xls
Diffuse and total radiation measured at the big open space and measured at the top of the flux tower.

- TREE_GAP.txt, TREE_GAP.xlsx
Individual tree gap measurements using 10 degree view cap. However, I realized that I forgot to match the sensor direction well. So above and below readings are not matched…. Next time, in October I will use hole view cap so that those mistakes can be avoid..

Field Data

No tank data

No TZ Well data found

No TZ Moisture Point data found

No VR Moisture Point data found

No TZ grass heigth found

No VR grass heigth found

Tree DBH