It’s 3 a.m. in Yanco, Australia, a remote region located 380 miles (612 kilometers) west of Sydney. While most people are still in bed, a small team of scientists prepares for takeoff in an aircraft that will gather data about the soil below. The early-risers are investigating the amount of moisture in the top 2 inches (5 centimeters) of the soil — a measurement similar to those made by NASA’s Soil Moisture Active Passive (SMAP) observatory orbiting 426 miles (685 kilometers) above in space.
Photo by Amy McNally.
Four hours later at daybreak, three more teams of scientists will head out on foot with specialized tools to measure soil moisture, vegetation coverage and surface roughness.
In total, around 40 scientists are studying the Australian soil as part of the Soil Moisture Active Passive Experiments-4 (SMAPEx-4) field campaign from the ground and air — the first major soil moisture field campaign conducted since SMAP launched Jan. 31, 2015. The three-week study, conducted from May 2 to May 22, is designed to validate soil moisture measurements from SMAP.
SMAP provides global soil moisture measurements every two to three days. The global maps will improve weather prediction, enhance flood forecasting and inform agricultural practices, including during droughts.
“Our scientists are taking the time to validate the SMAP products,” said Peggy O’Neill, SMAP deputy project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “This field campaign will help provide proof that our hard work is paying off.”
This field campaign is the fourth in a series of five SMAPEx campaigns in the region. Jeff Walker, the SMAPEx-4 project lead and professor at Monash University in Melbourne, Australia, says the previous campaigns were for algorithm development using aircraft instruments that simulated SMAP readings, but this campaign is for validation of actual SMAP algorithms and products.
“The aircraft campaign is the best way to directly test the algorithm for SMAP’s core soil moisture product at a spatial resolution of 9 kilometers,” said Simon Yueh, SMAP’s project scientist at the Jet Propulsion Laboratory in Pasadena, California. “The campaign’s three week duration will allow the observations of some precipitation and dry down cycles to validate the SMAP products over a variety of conditions.”
The SMAP satellite is estimated to pass over the Yanco region at approximately 6 a.m. local time and provide three high-resolution readings per week that the SMAPEx scientists can use. SMAP carries an active radar and passive radiometer. The active microwave radar sends a signal to the ground and measures the reflected radar pulse sent back to SMAP—a measurement called backscatter. SMAP’s passive radiometer measures brightness temperatures, a measurement of temperature based on how much microwave radiation is naturally coming from the ground. These SMAP measurements are converted to soil moisture observations.
The aircraft, also carrying a radar and radiometer, provides microwave backscatter and brightness temperature observations at high resolution to help verify SMAP’s products. The aircraft flies for about six hours during a SMAP overpass and mimics SMAP’s readings in terms of wavelength, viewing angle and resolution ratio.
On foot, scientists are measuring soil moisture directly. They use probes that stick into the ground and measure the amount of water in the top inches of the soil. These data are used to evaluate the calculated soil moisture measurements from aircraft and SMAP. The Yanco region has diverse climate, soil, vegetation and land cover, which allows for more rigorous testing of the SMAP algorithm over a variety of surface types and conditions.
Amy NcNally (front) of NASA, Alex White (far left) of USDA and other members learn how to operate their field equipment. Photo by Lynn McKee, USDA.
The field teams also measure the land’s vegetation coverage and surface roughness. Vegetation is important to factor in, as it influences the radar and radiometer signals observed by SMAP. For instance, denser vegetation tends to block signals from the soil surface and can appear as a warm to the SMAP radiometer. This would tend to produce lower (or drier) retrieved soil moisture measurements if the presence of vegetation was not taken into account.
The field campaign is a large effort involving several parties. The SMAPEx-4 team includes scientists from Australia, The Netherlands, Germany, France and the United States, including from NASA and the U.S. Department of Agriculture (USDA). The campaign receives vital support from Yanco Agriculture Institute in Yanco, Australia in providing facilities, storage, heavy ovens and scales— items that would be difficult and costly to import. Walker, a member of the SMAP Science Definition Team, and his colleagues have been planning these campaigns for years with the first one starting in 2010. The last SMAPEx campaign in the series is scheduled in the Yanco region in September 2015.
Participants from day 1 of the SMAPEx-4 field experiment: Wasin Chaivaranont, Paul Daniel, Shuvashis Dey, Ying Gao, Anouk Gevaert, Stefania Grimaldi, Muhsiul Hassan, Tom Jackson, Jon Johanson, François Jonard, Seokhyeon Kim, Fuqin Li, Yoann Malbéteau, Ian Marang, Alan Marks, Lynn McKee, Amy McNally, Grey Nearing, Philipp Pohlig, Luigi Renzullo, Chris Rüdiger, Sabah Sabaghy, Vivien Stefan, Jeff Walker, Alex White, Frank Winston, Xiaoling Wu and Nan Ye. Photo by Lynn McKee, USDA.
“Field experiments are one of the most demanding parts of validation in terms of human and fiscal resources. Therefore, they must be well designed and focused on specific objectives,” said Tom Jackson, SMAP Science Team calibration/validation lead and research hydrologist at the USDA.
To read blogs from the scientists participating in the field campaign, visit: smapex4.blogspot.com.au
For more information about the SMAPEx campaigns, visit: http://www.smapex.monash.edu.au/
For more information about SMAP, visit: http://www.nasa.gov/smap
Sab Kim
Jet Propulsion Laboratory
Updates on the vegetation conditions are provided here, monitored by the crop structure team. There were localized thunderstorms on July 15th, which gave 8 mm rainfall according to the local weather data. I happened to be in the field(!) and believe the campaign fields received much more. Some fields outside the low-altitude flight lines were not visited by the structure team. The conditions of these fields were instead monitored by the vegetation teams.
All the crops grew enough to start to make grains, and the percent ground covered by the vegetation was 80% to 100%, according to observations made between July 7th and 17th. The corn plants grew to 225cm high and will not grow much further even after the rainfall on 15th. Instead tassels and ears are developing, but no cobs yet.
Tassels on 2.2 m corn, July 17
Canola seed pods, July 5.
For more information, visit the SMAP Blogs From the Field site.
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.
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.
Tracy (U. Guelph) and Brian (U. Manitoba) were making LAI and NDVI measurements, respectively, in a soybean field.
Example of a typical soil profile: Litter (not shown), then organic layer (brownish orange layer), then soil (gray-colored layer), and then groundwater.
For more information, visit the SMAP Blogs From the Field site.
Grant Wiseman
Agriculture and Agri-Food Canada
Another hot and dry week here in southern Manitoba has us missing the rain just a little bit. We have experienced a very nice dry down cycle in weeks 3 and 4 after a wet up period initially in weeks 1 and 2. By all accounts this will contribute to a very informative and descriptive dataset.
Some sandy loam soils have approached zero volumetric moisture levels, while many clay soils remain high at 25 or 30 percent but it has become rather difficult to insert moisture probes. Even morning dew levels have subsided. Dare I say, “Let it rain?”
Field crews are well into their groove with many not requiring the use of GPSs or maps for navigation any longer. On a much-deserved scheduled down day some team members took in the Canada Day festivities and fireworks on July 1st at Assiniboine Park or The Forks.
We’re two thirds of the way through and going strong, looking forward to the home stretch!
For more information, visit the SMAP Blogs from the Field page.
Narendra Das
Jet Propulsion Laboratory
I am signing off from SMAPVEX12 at Winnipeg with good vibes, pleasant memories and expectation that this will be a very successful campaign. I hope that, like me, most of my teammates have learnt substantially about the study area and had a great field sampling experience, and have also made many good friends during interactions and group dinners.
I conducted crop structure sampling of various crops (corn, beans, canola, wheat, and pasture) for the last one month and witnessed the growth spurt in crops within the one month span. Even though I knew about crop responses to weather variables I was amazed to see such a rapid response of crop growth to conducive environment conditions, especially for canola and corn.
Dr. Tsang, Dr. Jackson, Narendra, and Sab
Corn plants on 06-09-2012
Corn plants on 06-30-2012
For more information and pictures, visit the SMAP Blogs from the Field page.
