AirMOSS: L2 Hourly In-Ground Soil Moisture at AirMOSS Sites, 2011-2015

There are 29 files in NetCDF v4 (*.nc4) format with this data set.

This data set provides level 2 (L2) hourly volumetric (cm3/cm3) soil moisture profiles from in-ground sensors at seven North American sites as part of the Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) project. Three profiles were installed at each site, sampling at seven different depths per profile (2 cm to 80 cm). Initial sampling began at three sites in September 2011 and additional sites were added during 2012 and 2013. All sampling concluded in December 2015. The AirMOSS project used an airborne radar instrument to estimate root-zone soil moisture at 10 study sites across North America. These in-ground soil moisture data were collected to calibrate and validate the AirMOSS data.

Project:  Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS)

The goal of NASA’s Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) investigation is to provide high-resolution observations of root-zone soil moisture over regions representative of the major North American climatic habitats (biomes), quantify the impact of variations in soil moisture on the estimation of regional carbon fluxes, and extrapolate the reduced-uncertainty estimates of regional carbon fluxes to the continental scale of North America.

• The AirMOSS campaign used an airborne ultra-high frequency synthetic aperture radar flown on a Gulfstream-III aircraft to derive estimates of soil moisture down to approximately 1.2 meters.
• Extensive ground, tower, and aircraft in-situ measurements were collected to validate root-zone soil measurements and carbon flux model estimates.

The AirMOSS soil measurements can be used to better understand carbon fluxes and their associated uncertainties on a continental scale. Additionally, AirMOSS data provide a direct means for validating root-zone soil measurement algorithms from the Soil Moisture Active & Passive (SMAP) mission and assessing the impact of fine-scale heterogeneities in its coarse-resolution products.

Related Data:

Soil Moisture Profiles and Temperature Data from SoilSCAPE Sites, USA

AirMOSS: L2 Hourly Precipitation at AirMOSS Sites, 2011-2015 

A full list of AirMOSS data products is available at: https://airmoss.ornl.gov/dataproducts.html.

Spatial Coverage: Seven sites across the USA, Canada, and Mexico

Spatial Resolution: Point locations

Temporal Coverage: 20110901 to 20151231

Temporal Resolution: Hourly

Study Area (coordinates in decimal degrees)

Data File Information

There are 29 files in NetCDF v4 (*.nc4) format with this data set.

File-naming convention

L2IGSM_calibrated_SITE_yyyymmdd_vv.nc4

where:

L2IGSM_calibrated = data product name

SITE = six character site name (see Table 1)

yyyymmdd = start date of data file

vv = data version number

Example file names: L2IGSM_calibrated_DUKEFR_20150101_03.nc4

          L2IGSM_calibrated_BERMSP_20140101_03.nc4

Table 1. AirMOSS sites where in-ground soil moisture (IGSM) was recorded. The seven standard sampling depths were: 2, 5, 10, 20, 40, 60, 80 cm.

Table 2. Data fields in the IGSM data files (e.g. L2IGSM_calibrated_DUKEFR_20150101_03.nc4)

 cm3/cm3

The Level 2 in-ground soil moisture data were collected to calibrate and validate other, higher-level, AirMOSS data products including the Level 2/3 Root Zone Soil Moisture estimates for each AirMOSS flight (Cuenca et al, 2015).

These data are provided with no QA information. The in-situ data were subjected to calibration procedures described in detail in Cuenca et al. (2015).

The goal of the Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) investigation is to provide high-resolution observations of root-zone soil moisture over regions representative of the major North American climatic habitats (biomes), quantify the impact of variations in soil moisture on the estimation of regional carbon fluxes, and extrapolate the reduced-uncertainty estimates of regional carbon fluxes to the continental scale of North America. See Chapin et al. (2012) for more details.

AirMOSS Flights

These Level 2 in-situ data are one set of products generated by the AirMOSS campaign.

For AirMOSS, NASA's Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) was flown on a Gulfstream-III aircraft, making frequent flights over ten sites (given in Table 3) in 9 different biomes of North America over the course of four years. In-ground soil moisture was not measured at all sites.

Table 3. AirMOSS sites

Beginning in September 2012, the AirMOSS instrument flew 215 flight campaigns. A summary of flight campaigns by year and site is found in Table 4. Typically, the aircraft made repeat visits to sites in the same region in a single week and then proceeded to another region. Most sites had at least three campaigns per year. The Harvard and Howland forest sites were flown together in a single day. In 2012, Chamela, La Selva, and Tonzi were not surveyed.

Table 4. Summary of AirMOSS flight campaigns.

A complete list of AirMOSS flights can be found at: https://airmoss.ornl.gov/flights.html.

AirMOSS Level 2 In Ground Soil Moisture Data

The objective of the in situ soil profile instrumentation was specifically to monitor soil water content over a depth representative of that which will have an impact on the P-band radar signal. Each of the seven AirMOSS sites sampled (Table 1) had three monitored soil profiles installed approximately 40 to 50 m apart along a “representative” (in terms of soil texture and vegetation) transect within the footprint of the flux tower. The in-situ observation system for the NASA AirMOSS project used 5-TE and 5-TM sensors by Decagon Devices (Pullman, WA) to observe volumetric SWC. Standard installation depths for these sensors at these sites were 2, 5, 20, 40 60 and 80 cm depths. In addition to volumetric SWC and temperature, the 5-TE is capable of measuring electrical conductivity in soil. These sensors determine volumetric water content by measuring the apparent (or bulk) dielectric permittivity (Eb) of the media (e.g. soils and peat) using capacitance/frequency domain technology. Since 5-TE and 5-TM sensors were installed in various soils in different biomes for this project, verification and calibration of these sensors was critical. Calibration of 5- TE and 5-TM sensors consists of two steps: 1) sensor specific calibration and 2) site specific calibration. Calibration methods and additional details are available in Cuenca et al. (2015).

Chapin, E., A. Chau, J. Chen, B. Heavey, S. Hensley, Y. Lou, R. Machuzak, and M. Moghaddam. 2012. AirMOSS: An Airborne P-band SAR to measure root-zone soil moisture, 2012 IEEE Radar Conference, Atlanta, GA, 2012, pp. 0693-0698. http://dx.doi.org/10.1109/RADAR.2012.6212227

Cuenca, R.H.,Y. Hagimoto, T.M. Ring, and J.P. Beamer. 2015. Interpretation of in situ observations in support of P-band radar retrievals. Geoscience and Remote Sensing Symposium (IGARSS), 2015 IEEE International. 5083-5086. http://dx.doi.org/10.1109/IGARSS.2015.7326976