Researcher Amy McNally spent two weeks in Yanco, Australia to participate in the three week Soil Moisture Active Passive Experiment-4 (SMAPEx-4) field campaign in May. The field campaign measures soil moisture and related data using ground and airborne instruments. The data is used to validate actual data and algorithms from the SMAP satellite. In the following Q&A, McNally shares her experience on the SMAPEx-4 ground validation team and her first impressions of Australia.
McNally and her team pack up at the end of a long day of taking ground measurements (photographer Amy McNally)
NASA: What do you do at NASA’s Goddard Space Flight Center for your day job?
McNally: I am a Post-doctoral researcher in the hydrologic sciences lab, where I am customizing the NASA Land Information System for food and water security applications in Africa and the Middle East. This work supports the US Agency for International Development (USAID) and the Famine Early Warning Systems Network (FEWS NET). Day-to-day, I run hydrologic models that use remotely sensed, satellite inputs (rainfall, vegetation, and soil moisture) and use the outputs to answer USAID’s questions about, for example, the current water crises in western Yemen and southern Botswana.
What are your tasks in the SMAPEx-4 field campaign?
Starting at six every morning, we are measuring near-surface soil moisture and recording the land use/land cover type (mostly, crops and pastures), vegetation height, and the presence/absence of irrigation. We sample every 250 meters (0.15 miles), which adds up to walking about 9 kilometers (5.6 miles) a day over 5 hours.
How does your fieldwork compare and contrast to your job back at Goddard?
The work is very different! This fieldwork is physical labor – 9 km of walking is a lot for people who normally sit at a desk. However, it is still important to pay attention to details, stay organized, be efficient with time, troubleshoot problems with equipment (including the mini-computer/data logger and software) and help out other members of the team.
What do you enjoy about being part of SMAPEx-4?
First, we get to meet other scientists from all over the world who are interested in remote sensing hydrology. My sampling team has people from South Korea, China, Iran, Panama and Australia. Our similar research experiences are a good starting point for conversations about all of our differences – in research (ranging from algorithm development to downscaling to applications) and culture (food, language and customs).
Second, it’s also great to be walking in the outdoors for hours. And of course, just being in Australia! We see so many different types of birds (emus!), as well as kangaroos, foxes and lots of sheep. But nothing tops the koalas!
How has this experience changed your perspective on how you understand SMAP data?
This was a great opportunity to learn more about the SMAP mission as well as other current microwave satellites (Soil Moisture and Ocean Salinity and Aquarius). Since I work on SMAP applications, it was interesting to learn more about the airborne active and passive sensors, and the design of the field sampling strategy that will be used for calibration/validation activities. I have greater appreciation for all the hard work that so many people are doing to make the SMAP mission a success.
For more updates from the field, visit the SMAPEx-4 blog.
Amy NcNally (Front) of NASA, Alex White (Far left) of USDA and other members learn how to operate their field equipment. (Photographer Lynn McKee)
McNally with her ground validation team. Photographed from left to right: Amy McNally, Fuqin Li, Sabah Sabaghy, Seokhyeon Kim (photographer/captain Alan Marks)
Taking ground measurements in the field on a particularly windy day with potentially rainy clouds (photographer Amy McNally)
Spotting a koala while out in the field (photographer Amy McNally)
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
I am writing this post from Iceland, a few days after the last team members left Kulusuk, Greenland. Back from the field, we spent five days packing up our equipment and organizing the container for the end-of-summer field campaign. Overall the firn aquifer field campaign was a success. However, since we experienced difficult weather conditions, we did not fully complete our initial goals because we were not able to bring the seismic equipment into the field (the snow surface conditions prevented us from using snowmobiles which were required for the seismic surveys). The weather is difficult in this region, which makes measurements more challenging to make. Therefore, we needed to make adjustments to maximize the science that could be done.
Olivia uses everything available to dry our tents.
Anatoly and Lora ready to go home via Reykjavik, Iceland.
We spent 14 days camping on the ice sheet at a location about 130 kilometers northwest of Kulusuk, at a latitude close to the Arctic Circle. We spent three days extracting a 56-meter firn/ice core using a combination of an electromechanical drill and an electrothermal 4-inch drill provided by IDDO. We equipped the freshly drilled borehole with temperature sensors and a pressure transducer to monitor the seasonal changes of the firn aquifer temperatures and to monitor the changes in height of the water table. In the meantime, our team deployed a piezometer above, within, and below the aquifer to measure hydraulic permeability with a vertical resolution of 1 foot. In addition, aquifer water samples were collected to date the water by using different techniques. I invite you read Olivia’s blog post for further details on the water sampling. We measured ice surface velocity using a high-precision GPS from UNAVCO. Finally, we successfully used the magnetic resonance to estimate the volume of water in the in a non-destructive way as described by Lynn in our previous blog post.
In terms of weather, we experienced a five-day snowstorm with two storms back to back which dropped about 1 meter of snow. After the snowfall, katabatic winds started, blowing this freshly fallen snow at 40 knots and our tents needed hourly maintenance for about 36 hours to avoid being buried. The small mountain tent was too much work to maintain and we decided to only stay in the bigger Arctic Oven tents. At the end of the storm, important efforts were necessary to dig out camp and the cargo lines, which exhausted the team. In addition, the relatively warm temperatures during the storm (maximum at about -5˚C) got us wet and it was difficult to dry out. After 72 hours of continuous shoveling and tremendous efforts to avoid being buried and maintain camp, our PIs voted for team extraction as safety was compromised. Two days later we were picked up by the B-212 Air Greenland helicopter and after 50 minutes of travel we arrived safely in Kulusuk.
Olivia and camp after the five-day storm.
Monitoring station ready to transmit data (temperature and pressure) for a year or more.
Last evening in the field.
Overall, this field season was instructive and extremely helpful to plan our next field campaign which will happen in September this year. We confirmed that southeast Greenland was a challenging place to work, but we successfully collected a great hydrology data set, as well as confirmed the potential of the magnetic resonance to estimate liquid water content over a 80 by 80 meter wired loop. We postponed the radar and seismic studies for the fall campaign since we would be more likely able to bring a snowmobile to the field, crucial of the deployment of such experiments.
Lynn and Olivia enjoying the Kulusuk sunset on their last day.
The quiet village of Kulusuk in the evening light with resting huskies.
Northern lights from the Kulusuk Hotel.
The spring 2015 campaign is now over. I hope you enjoyed reading the blog posts, and we now wish for a great and warm summer! Please stay tuned as we will be back in August/September for additional measurements on this part of the Greenland ice sheet, and will update the blog then.