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SMAP - Soil Moisture Active Passive - Mapping soil moisture and freeze/thaw state from Space
BLOGS FROM THE FIELD
Field Work in Croplands and Forests
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Photo 1: 10:30 pm at Winnipeg. Summer here features long hours of daylight. This may offer unique Cal/Val opportunities to obtain ground truth at the same time as SMAP.
July 13, 2012
Steven Chan
Jet Propulsion Laboratory

As an avid photographer, I totally agree with what Diane Arbus said, “I really believe there are things that nobody would see if I didn't photograph them.” So here in this blog I’m taking a more photojournalistic approach. Enjoy!

My work in SMAPVEX12 primarily consisted of two tasks: Vegetation sampling in crop fields and soil moisture sampling in forests. The two tasks alternated according to PALS flight schedule and weather conditions. Because I arrived in July, my observations were all about the later phase of the campaign.

Our cropland vegetation sampling involved measurements of optical parameters (e.g., LAI and NDVI) and allometric parameters (e.g., height and diameter). On a typical day we visited up to six fields to collect data and actual plant samples.

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Photo 2: SMAPVEX12 Regional Operation Center or the ROC.

So far we had visited wheat, soybean, canola, and corn fields. From an algorithm development standpoint, the wide range of vegetation properties represented by these fields will provide a valuable data set that would help improving radar and radiometer forward modeling efforts.

Compared with cropland vegetation sampling, forest soil moisture sampling is not for the faint-hearted (pun intended)! Not only were forest sites more remote than other sites from the ROC, but also they were less accessible by vehicles.

In one particular forest site, for example, we had to carry our supplies and tools (e.g., water, batteries, shovels, tins, knife, soil moisture probes, etc.) and walked half a mile to get to the “entrance” of the site. Soil moisture measurement in forests is a lot more time-consuming than soil moisture measurement in croplands, so we normally could not return to the base until close to 4:00 pm.

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Photo 5: Shoulder high Canola plants. In some fields they were already 5-6 ft tall. Canola plants tend to entangle one another, so walking through required a lot of effort.
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Photo 4: Wheat had matured quite a bit since the beginning of the campaign. Here Brian, Hida (U. Guelph), and Tracy were carrying plant samples for further analysis at the ROC.
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Photo 3: Here Tracy (U. Guelph) and Brian (U. Manitoba) were making LAI and NDVI measurements, respectively, in a soybean field.
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Photo 8: At the end of the day, several teams convened to a common spot to have some fun together. Before we headed back to the ROC we posed for a group picture (not all of us were in the picture though).
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Photo 7: Tracy was explaining the benefits of SMAP to a local farmer (far right) at Elm Creek. He looked excited at what we were doing. On our second visit, we saw this gentleman again. This time, it was he, not we, who was explaining the benefits of SMAP to other local residents!
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Photo 6: Towards the end of my stay, we visited a number of corn fields. Most corn plants were already taller than us. In fact, if we did not follow closely one another, it would be easy to lose visibility and get lost. Getting lost in a corn field is like getting lost in a corn maze, except that no one would be able to find you and get you out.
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Photo 10: Example of a typical soil profile: Litter (not shown), then organic layer (brownish orange layer), then soil (gray-colored layer), and then groundwater.
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Photo 9. Forest soil moisture sampling team. Left to right: Karel, Ruzbeh, and Steven. Alexandra was not with us that day.

Besides remoteness and difficulty of access there were additional hurdles to be overcome. Of these, our battles with insects ranked first on the list. In almost all forest sites we visited, we were continuously bombarded by ticks, flies, and mosquitoes. In one site, we could not even kneel down to make soil moisture measurement because there were too many fire ants on the ground. These sites were not maintained (or not so regularly), so there were no clear pathways either. To move forward we had to push through tree branches after tree branches, and step over fallen trees after fallen trees. In some tough spots we even had to cut our way out using a long machete.

Despite these difficulties my field work in forests had been quite rewarding. First, I worked with a group of fun partners (Ruzbeh -- USC, Karel – U. Sherbrooke, and Alexandra – MIT). Any fatigue resulting from hard labor was usually dissipated quickly with one deep laugh or two. Second, I learned first-hand what a typical soil profile looks like, how a vegetation dielectric measurement is made, and why mixed forests pose such a challenge to theoretical modeling.

Within a week SMAPVEX12 will come to a glorious finish. My feeling is that history will confirm this is an important field campaign in terms of data quality, observation duration, biome variety, sensor diversity, sampling extensiveness, and international partnership.

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Photo 13: The vastness of forests is humbling. Here Alexandra was shown walking after collecting a few soil samples for gravimetric analysis.
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Photo 12: We had to watch out for dangling dead trees. Young, sharp, and semi-rigid branches were also a hazard by snapping back at our faces as we moved forward.
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Photo 11: Forest is in many ways like human population. There are young trees; there are also old trees. Dead trees due to termites just fall down and begin decaying.
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Photo 16: We measured the dielectric properties of trunks, leaves, and vines. We also measured how these properties vary with direction relative to the Sun.
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Photo 15: July 27, 2012 is only a few days away. If there were an Olympic game on shovel throwing, here would be a match between USA and France.
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Photo 14: Even in forests well-defined by a single specie (aspen here), the reality may not be what we imagine or try to formulate on paper.


and finally...

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Photo 19: Most people desire to be understood, and so do trees. Apparently, this tree appreciated our analytic work with a smiley.
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Photo 18: A previous team (Mariko, Parag, Vanessa) had scouted the sites and carefully labeled locations. Without their hard work our's would not have been possible.
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Photo 17: We also collected actual leaf samples. Our measurements were automated by computer software. This saved us a lot of time in data logging.
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Photo 20: July 12, 2012 was an off day due to thunderstorm (see the looming cloud behind the sign). As soon as I spotted this roadside attraction, I cannot help pulling over immediately to take a look. Interestingly, the sign is located in the City of Landmark.

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