NASA studies vegetation canopy water content, soil moisture

Dec 22, 2011 By Beth Hagenauer
NASA's DC-8 airborne science laboratory flew low over San Joaquin Valley farm fields while specialized instruments collected data during the vegetation canopy and soil moisture study. Credit: Jane Peterson/NSERC

( -- Scientists seeking insight into the role vegetation plays in water fluctuation between soil and the atmosphere recently conducted research using specialized sensors during a series of NASA Airborne Science flights over California's San Joaquin Valley.

A high-altitude ER-2, a DC-8 flying laboratory and Gulfstream III , all based at NASA's Dryden Aircraft Operations Facility in Palmdale, Calif., made a series of flights over the southern , one of the most productive agricultural areas of the United States, between June 2010 and November 2011. The aircraft carried several specialized instruments designed to evaluate diurnal in the canopy area of almond and pistachio orchards near Lost Hills, Calif., and vineyards near Delano, Calif.

The primary sensors used to monitor vegetation canopy were the MASTER, or MODIS/ASTER, airborne simulator and AVIRIS, or Airborne Visible/Infrared Imaging Spectrometer. These NASA-developed instruments, when mounted on an aircraft, can acquire data sets with a range of spatial resolution better than . Collecting MASTER and AVIRIS data several times a day from the air made it possible to monitor the diurnal evapotranspiration and vegetation canopy water content changes.

Morning, left, and afternoon, right, MASTER imagery of the study site consisting of three pistachio and eight almond blocks. Lightness in color on the right image indicates the lower vegetation canopy water content. Labels on left image are orchard block numbers. Credit: University of California, Davis

NASA's MASTER and AVIRIS spectrometers mounted in the ER-2, a civilian version of the Air Force's U-2, gathered data from 65,000 feet altitude at about 11 a.m. and again about 3 p.m. during flights in May and November 2011. The ER-2 can acquire MASTER and AVIRIS data simultaneously, with both instruments tracking estimates of vegetation water content. In addition, MASTER monitors evaporation and transpiration.

The G-III carries the Synthetic Aperture Radar designed and operated by NASA's Jet Propulsion Laboratory in Pasadena, Calif. Located in a specialized pod attached to the belly of the aircraft, the sensor acquires repeat-path data from an altitude of 41,000 feet. During four flights over the target area at solar noon, or roughly 1 p.m., in June 2010 and May, June and November 2011, the UAVSAR collected data to determine soil moisture changes. Two of the G-III's missions took place on days the ER-2 flew.

The DC-8 carried MASTER on five flights to an altitude of about 13,000 feet, traversing the study area twice each day to acquire both morning and afternoon data. This aircraft allowed the sensors to acquire higher spatial resolution than the ER-2, but the DC-8 cannot carry MASTER and AVIRIS concurrently. The DC-8 flew one flight in June 2010 and two flights each day on June 28 and June 30, 2011. The NASA G-III was also in the air with the DC-8 to obtain measurements on June 29, 2010, and June 30, 2011.

In addition to the data-collection flights, scientists gathered leaf samples from the orchards and soil moisture measurements. The study plots were visited during the morning and afternoon on the day before a flight, the day of a flight and the day after to determine the water content of leaves over the course of a day.

Along with ground-based sampling of evapotranspiration, and vegetation water content measurements, the MASTER, AVIRIS and UAVSAR data collection at different altitudes allowed for a tracking of water changes between the ground, canopy and atmosphere throughout the day. The various hours of collection were important to this study because canopy water content has been proven to decrease from morning to afternoon.

Explore further: Western Australian landscape isn't as tectonically stable as previously thought

Related Stories

NASA airborne radar set to image Hawaiian volcanoes

Apr 04, 2011

( -- The Kilauea volcano that recently erupted on the Big Island of Hawaii will be the target for a NASA study to help scientists better understand processes occurring under Earth's surface.

NASA flies greenhouse gas mission over Nevada salt flat

Jul 07, 2011

Scientists from NASA's Ames Research Center, Moffett Field, Calif., joined a multi-institute team of researchers June 17-27, 2011, to investigate carbon dioxide and methane gas emissions from a dry lake bed and neighboring ...

NASA Sensor Completes Initial Gulf Oil Spill Flights

May 28, 2010

( -- NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument collected an image over the site of the Deepwater Horizon BP oil rig disaster on May 17, 2010. Crude oil on the surface ...

DC-8 flying lab validates laser instruments

Aug 11, 2011

( -- Twenty scientists went aloft aboard NASA’s DC-8 flying laboratory in late July to conduct an airborne test of four very different laser techniques for remotely measuring atmospheric carbon ...

NASA Airborne Radar Studies Haiti Earthquake Faults

Jan 27, 2010

In response to the disaster in Haiti on Jan. 12, NASA has added a series of science overflights of earthquake faults in Haiti and the Dominican Republic on the island of Hispaniola to a previously scheduled ...

Recommended for you

Fjords are 'hotspots' in global carbon cycling

10 hours ago

While fjords are celebrated for their beauty, these ecosystems are also major carbon sinks that likely play an important role in the regulation of the planet's climate, new research reveals.

Warm oceans caused hottest Dust Bowl years in 1934/36

11 hours ago

Two ocean hot spots have been found to be the potential drivers of the hottest summers on record for the Central US in 1934 and 1936. The research may also help modern forecasters predict particularly hot ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.