Soil Moisture Active Passive (SMAP): SMAP Gathers Soil Data in Australia

May 7th, 2015 by Kasha Patel

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.

Early mornings. Photo by Amy McNally.

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.

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.

The "group shot" photo is from Day 1 of the SMAPEx-4 field experiment. The participants are: 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.

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

Greenland Aquifer Expedition: Away From the Ice Sheet Until the Fall

May 5th, 2015 by Clément Miège

Hi there!

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.

Olivia uses everything available to dry our tents.

Anatoly and Lora ready to go home via Reykjavik, Iceland.

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.

Olivia and camp after the five-day storm.

Monitoring station ready to transmit data (temperature and pressure) for a year or more.

Monitoring station ready to transmit data (temperature and pressure) for a year or more.

Last evening in the field.

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.

Lynn and Olivia enjoying the Kulusuk sunset on their last day.

The quiet village of Kulusuk in the evening light with resting huskies.

The quiet village of Kulusuk in the evening light with resting huskies.

Northern lights from the Kulusuk Hotel.

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.

Greenland Aquifer Expedition: Final Fieldwork and an Aquifer Sighting

April 28th, 2015 by Lynn Montgomery and Anatoly Legtchenko
The slope of the ice sheet was crazy! Or we just took a very crooked picture. From left to right: Clem, Lynn, Olivia, and Anatoly.

The slope of the ice sheet was crazy! Or we just took a very crooked picture. From left to right: Clem, Lynn, Olivia, and Anatoly.

April 25, 2015 — The team had come back exhausted and cold but very happy to have a warm meal and bed on Thursday (April 23). Anatoly and I were very excited to have everyone safe after the very long and stormy two weeks they had had in the field. On Friday (April 24), the next day, we had to go back to dig out and load the 2,400 kilos of remaining gear. As a team, we discussed the possibility of trying to do the magnetic resonance (MR) measurements between the first and last flights to get the remaining gear out. It would only take about a few hours to set up and take the measurements so we were hopeful that we would have enough time to do it, as three flights would take most of the day to complete. Olivia, Clem, Anatoly, and I would head out to the camp on the ice sheet in the morning to load the rest of the remaining gear and attempt to complete the MR science at site one. Lora, Josh, and Kip would stay to help unload the incoming helicopters.

A frozen tight-water (outflow) glacier we saw on the way to the field site.

A frozen tight-water (outflow) glacier we saw on the way to the field site.

Sestrugies along the expanse of the ice sheet.

Sestrugies along the expanse of the ice sheet.

After a month of delays in Kulusuk, I had become a logistics expert. I knew how the flights worked and the pilots by name, how to organize all of the helicopter loads, and how to correspond with the team and project managers. But this would be my first experience doing science on the ice sheet. I woke up beyond excited Friday morning to finally be going to the field! As Anatoly said, “Working in Greenland is comparable to fishing: patience and good luck. And one has to have the necessary time for waiting for this chance and then to catch it.”

We headed off to the airport around 8:30 a.m., taking just personal bags packed with food and back-up gear as we did not plan to spend the night in the field. The weather couldn’t have been better; it was sunny with almost no wind and not a cloud in the sky. The Bell 212 helicopter landed at 9 a.m. and we loaded it with the MR gear and our bags. We said a quick goodbye and took off to the field. The flight was about 45 minutes from Kulusuk airport to the field camp, easily recognizable by the bright orange Arctic oven tents. We hopped out of the helicopter and immediately began unloading our gear and reloading with the gear set up by the team in the cargo lines the day before.

Fueling up the Bell 212 and giving Lora giving last minute advice.

Fueling up the Bell 212 and giving Lora giving last minute advice.

The team had filled us in on the conditions on the ice sheet including many stories about how they had to wade through the waist deep soft snow and the terrible 40-knot winds most days. I expected the worst and had dressed in my warmest layers ready to combat the harsh conditions. When we landed, there were similar conditions to Kulusuk; no wind, very sunny, and not a cloud in the sky. It was a great white expanse and we could see for miles. This was the perfect day to work and fly on the ice sheet. I took my first step off the helicopter and my foot sank down so the snow was up to my knees. The first ten minutes were like learning to walk again, as I fell with every other step trying to catch my footing while carrying boxes to load the helicopter. The pilots took off with the first load, which we had stuffed as full as possible with gear. We were alone on the ice sheet.

Loading up the first helicopter flight.

Loading up the first helicopter flight.

Anatoly, Olivia, Clem, and I decided it would be best to split into two groups. Anatoly and I would begin set up the MR and Clem and Olivia would move gear and begin to take down tents for the next flight load. We unpacked the MR gear quickly and I began placing cables to create an 80 meter by 80 meter loop then attaching connectors at each corresponding point of the cables. It was exhausting having to trudge through the snow but I knew it had to be done as fast as possible in order to get measurements before the last helicopter. Anatoly began the setup of all the computer gear in one of the remaining tents and within an hour we were beginning the measurements! Magnetic resonance imaging has never been used in this part of Greenland and in the framework of the project was seen as a challenging technique that may help to constrain hydrogeological modeling.

Anatoly taking magnetic resonance measurements.

Anatoly taking magnetic resonance measurements.

All the while, Clem and Olivia set up the next two cargo lines, took down one of the sleep tents, and shoveled out gear. While the MR measurements were running, Anatoly and I helped with shoveling and taking down the tents. The helicopter arrived for the second flight load and I even got to assist them with landing, standing in a meter or two front of the landing spot as a point of reference, then kneeling down when they got close to protect myself from the massive wind storm they bring with the rotors. We loaded the second flight just as the first and they were off again. Only one more flight to go!

Clem and Olivia digging out the tents.

Clem and Olivia digging out the tents.

Clem beginning to shovel out the gear lines.

Clem beginning to shovel out the gear lines.

Lynn and Clem with the second helicopter load.

Lynn and Clem with the second helicopter load.

We ate a quick late lunch in the remaining tent with the MR gear in it and saw the initial results. The radar, hydrology, and drilling were confirmed; there was indeed an aquifer filled with water around 20 meters below where we were standing. How cool is that?! We called Lora to check on the last helicopter flight and they had already landed and were on their way back. Anatoly needed a bit more time to finish his measurements. We devised a plan to get everything taken down in time. Olivia and I would be ready to coil all the cables and get all the connectors collected as soon as the MR was done collecting data, and Clem would take down the rest of the final tent. Anatoly gave us the “go” signal and we all sprang into action. With a little luck and a very quick pace, we put the last coil into the MR box as we heard the helicopter in the distance. Within 8 hours of exceptionally hard work, we had done what was planned to take 3-4 days.

We loaded the last few boxes with the pilots help and jumped in the helicopter ourselves. The pilots even told us they had seen polar bear prints around 10 kilometers from our camp! We scoured the ice sheet on the way back but never saw any prints. Around 50 minutes later, we were back home in Kulusuk just in time for dinner.

Greenland Aquifer Expedition: Wow, That Was a Lot of Snow

April 25th, 2015 by Lora Koenig
Tents before the storm (left) and snow reaching near the top of our tents after two storms (right).

Tents before the storm (left) and snow reaching near the top of our tents after two storms (right).

April 24, 2015 — I believe in one of my first blog posts I mentioned that we were working in an area of high accumulation (snowfall) on the Greenland Ice Sheet. I would like to change that to an area of VERY HIGH accumulation! Actually Southeast Greenland does receive the largest amount of snowfall on the entire ice sheet. In previous years we have experienced storms dumping over a meter of snow. This year we had one of those storms bringing well over a meter of snow and then 3 hours after the first storm ended we got a second, bigger storm, pushing our 5 days snow total to nearly 3 meters of snow.

The amount of snow is best summed up by a dinner conversation in our cook tent where Olivia, being on the ice sheet for the first time, asked Clem, Josh and I, ice sheet veterans, what the biggest storm we had ever been in was like. We all responded, in unison,” this is the biggest storm we have ever been in!” While the weather was not particularly cold or windy, it just kept snowing. The low wind made it possible for us to continue science measurements through the storm in a special tent, with no floor, providing both shelter and access to the snow.

The storm hit on the day we were finishing up drilling. We drilled a 56 m borehole into the aquifer, reaching water around 19 m below the snow surface just as we expected. Drilling ice cores is a routine practice on the ice sheet and allows us to see the structure of the ice and measure the ice density; it is less dense near the surface and then compacts to ice at around 35 m in this region. Josh drilled the ice core using both a mechanical drill, called the sidewinder, in the top 19 m of dry firn and with an electrothermal drill in the water saturated firn below. Josh would drill about 1 m of core every 10 minutes and then Clem and I would weigh it, measure it, record ice layers, record the ice temperature and bag certain sections for Olivia’s hydrology measurements. Once the core was processed we took the remaining core to the kitchen tent to melt for our drinking water. (The more dense ice from deeper in the ice sheet produces more water than the less dense surface snow, so we are happy to use it for making water for the camp.)

Lora with Clem reflected in goggles holding an ice core with water bubbles.

Lora with Clem reflected in goggles holding an ice core with water bubbles.

Lora processing an ice core.

Lora processing an ice core.

While we were finishing the drilling Kip and Olivia were working out the kinks of using their equipment for the first time on an ice sheet. They worked through a few freezing issues and quickly had the first every water samples from the aquifer. They melted a piezometer into the ice sheet, inserted a tube and started pumping up water. We were all ecstatic to see the water gushing out of their tube and into their sample bottles.

Water samples from the Greenland aquifer.

Water samples from the Greenland aquifer.

As the hydrology sampling continued so did the storm. We had not received another resupply flight so we were running low on fuel, did not have a snowmobile or sled to move the drill to our next site and our additional team mates and measuring equipment had yet to arrive to complete more science. We knew we were already very delayed so we made the decision to postpone our seismic measurements until the fall. In the meantime the snow continued to fall!

By the third morning of the storm we were all sinking into the snow at least up to our thighs, if not our chest. Our tents were about 7 meters apart and it could take 5 minutes, and half your energy, to break trail between them. We often found it easiest to craw on the surface as opposed to walking. While the hydrology crew collected samples the rest of us dug out camp. We dug about every 2 hours. Even during the night we would have to get out and dig. In the end Josh moved into a tent with Kip and Clem, a tight fit, but more comfortable than digging out his smaller mountain tent all night. We also moved our fuel and generators into the cook tent and let our science gear get buried in its cargo line, marked with tall poles at either end, until the end of the storm. This reduced the area we had to shovel.

Path through the snow.

Path through the snow.

Josh relaxing after digging out the cook tent.

Josh relaxing after digging out the cook tent.

As the snow continued to fall, the winds stayed low. We were thankful for the low winds but knew after the storm the katabatic winds, outflow of cold air that gravitationally flows off the ice sheet, would kick up with a vengeance. On April 20th we woke up to light snow and no winds. The storm was over so we dug out all the cargo creating snow piles over our heads. Now we needed a Helo to bring in more science gear, and fuel, so we could keep working. The surface conditions were so soft that we could no longer operate a snowmobile even if we had one. At that point we knew we would only get one site completed this season because we really couldn’t move.

The calm was short lived. By the afternoon the Katabatic started with the furry we expected. The winds increased to 30 knots very quickly. Over the next 3 days the winds blew and moved all the snow around again. We were digging out our tent almost every hour. All we were doing was digging. Digging out the tents, digging the snow out of our pockets, goggles, gloves, everywhere!  We were tired! We made a decision to end the season once a Helo could get in since we had completed most of the measurements. Today, April 23, we finally got a Helo and all flew back to Kulusuk for a nice shower and warm meal. Tomorrow we will day trip back to remove our camp and, hopefully, let Anatoly make the first every electromagnetic resonance measurement on the aquifer.

Finally our helo arrives and sinks to its belly.

Finally our helo arrives and sinks to its belly.

Greenland Aquifer Expedition: “Groundwater” Study Hits the Ice Sheet

April 23rd, 2015 by Olivia Miller, University of Utah
The team on a walk to the airport to organize gear.

The team on a walk to the airport to organize gear.

Hello! This is Olivia and I’ll be writing about the hydrology work we are doing this year on the Greenland ice sheet. A few years back some scientists on our team discovered liquid water inside the ice sheet. They partnered with us to study the water in greater depth.

We think that the snow melts at the surface, percolates down through the snow and firn, and pools inside the ice. The water fills up the air space between the ice crystals, creating an aquifer inside the ice sheet that we think behaves similarly to aquifers found on land. The hydrology that we are doing this season is basically a “groundwater” hydrology study, except that in this case it is an “ice-sheet-water” hydrology study. We will try to test our ideas about how the aquifer behaves and understand what that means for the ice sheet and sea level rise more broadly.

To answer these questions, we will collect measurements of how deep the water is and how much pressure it has to determine where the water is entering and exiting the aquifer. We will test how quickly the water travels through the firn and also collect water samples. The chemistry of the water will tell us information about how long the water has been inside the ice sheet. All of this information will give us a much better idea of how the aquifer is filling up, and where the water is going, and how quickly it moves. This kind of information is important for understanding how ice sheet melt relates to sea level rise. If the aquifer is storing water for long periods of time, than it may have less of an immediate impact on sea level rise. However, what happens if it fills up and suddenly drains quickly? Or maybe it is constantly draining?

To make our measurements and collect our samples, we had to do a lot of work to modify traditional groundwater hydrology tools and instruments to work at very cold temperatures. Groundwater hydrologists often use piezometers, long pipes that have a small opening at the bottom to let water in, to access the aquifer they are investigating. To install a piezometer into the ground, you can pound it in. To install our piezometer into the ice, we have developed a piezometer with a heated tip that can melt through the hard ice layers.

Another challenge we face is that many of the samples we collect cannot freeze, and yet we expect the temperature at our field site to often be below freezing. When we collect these samples, we completely fill the sample bottle so there is no air space in the bottle. We do this so that we can analyze gasses that are dissolved in the water back in the lab. If these samples froze, the water would expand and break the bottle, ruining the sample. To prevent these samples from freezing, we have modified several coolers to be extra-insulated and to have special heaters inside them.

It has been quite the learning experience to take all of our groundwater hydrology work to such a different environment! But this is part of what makes the science exciting. We get to try something that has never been done before.

Notes from the Field