AST_08 v003

ASTER L2 Surface Kinetic Temperature


PI: U.S./Japan ASTER Science Team

Description

The ASTER Surface Kinetic Temperature (AST_08) is generated using the five Thermal Infrared (TIR) bands (acquired either during the day or night time) between 8 and 12 µm spectral range. It contains surface temperatures at 90 m spatial resolution for the land areas only. Surface kinetic temperature provides a vital input to studies of volcanism, thermal inertia, surface energy, and high-resolution mapping of fires. This product is derived using the same algorithm as the ASTER Surface Emissivity AST_05 Product.

Surface kinetic temperature is determined by applying Planck's Law using the emissivity values from the Temperature/Emissivity Separation (TES) algorithm, which uses atmospherically corrected ASTER surface radiance (TIR) data. The TES algorithm first estimates emissivity in the TIR channels using the Normalized Emissivity Method (NEM). These estimates are used along with Kirchoff's Law to account for the land-leaving TIR radiance that is due to sky irradiance. That figure is subtracted from TIR radiance iteratively to estimate the emitted radiance from which temperature is calculated using the NEM module.

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Characteristics

Improvements/Changes from Previous Versions

The Science Scalable Scripts-based Science Processor for Missions (S4PM) Version 3.4 algorithm has additional input data options that provide better input data coverage (simultaneously acquired MODIS data versus 6-hourly modeled NCEP input data) and consequently more accurate Level 2 output data. The updated algorithm includes the following improvements:

  • A new option has been added to use MODIS Version 6.1 (MOD07_L2) Temperature, Water Vapor, and Pressure inputs. The default order option will remain as National Centers for Environmental Prediction (NCEP)/Global Data Assimilation System (GDAS).
  • The default for the Ozone input data was switched from NCEP/Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS) to the new Total Ozone Analysis using Solar Backscatter UltraViolet Version 2 (SBUV/2) and TOVS (TOAST)/Earth Probe-Total Ozone Mapping Spectrometer (EPTOMS) option.
  • The Level 2 algorithm has been updated to provide a fall back option for the Temperature/Water Vapor/Pressure and Ozone input selections. Both selections will automatically revert to the next lower input if the selected input is not available.
    • The Temperature/Water Vapor/Pressure input will fall back from MOD07 to NCEP/GDAS then to Climatology.
    • The Ozone input will fall back from TOAST/EPTOMS to OZ_DLY/TOVS then to Climatology.

Collection and Granule

Collection

Characteristic Description
CollectionTerra ASTER
DOI10.5067/ASTER/AST_08.003
File Size~3 MB
Temporal ResolutionOther
Temporal Extent2000-03-04 to Present
Spatial ExtentGlobal
Coordinate SystemUniversal Transverse Mercator (UTM)
DatumWorld Geodetic System (WGS84)
File FormatHDF-EOS
Geographic Dimensions~60 km x 60 km

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers1
Columns/Rows700 x 830
Pixel Size90 m

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
KineticTemperature Surface kinetic temperature composite Kelvin 16-bit unsigned integer N/A N/A 200 to 3200 0.1

There are three groups of ancillary data inputs used in the atmospheric correction of ASTER Level 2 products:

  1. Ozone data input: The default for the Ozone input data is the new Total Ozone Analysis using Solar Backscatter UltraViolet Version 2 (SBUV/2) and TOVS (TOAST)/Earth Probe-Total Ozone Mapping Spectrometer (EPTOMS) option. The fall back option is the National Centers for Environmental Prediction (NCEP)/Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS). The NCEP/TOVS data are acquired from a NOAA satellite, and provides the ancillary column ozone data twice daily. The second fall back option is the Naval Research Laboratory's (NRL) Ozone Climatology dataset.
  2. Aerosol data input: The NRL Aerosol Climatology ancillary data are the only available input.
  3. Temperature, Atmospheric pressure, and Moisture Profile data inputs: Simultaneously acquired MODIS Version 6.1 (MOD07_L2) Temperature, Water Vapor, and Pressure inputs were added as a new option on October 23, 2019. The default order option will remain as the NCEP-Global Data Assimilation System (GDAS) which is available every 6 hours. The second alternative is the NRL Climatology data which are based on modeling, simulation, and prediction. They are static, monthly, averaged datasets, therefore, used only as a last resort.

Known Issues

The AST_08 products do not yet include the OPERATIONALQUALITYFLAGEXPLANATION field in the metadata file to indicate if a fall back has occurred and identify which input source was used to generate the Level 2 product files. A future release will include this metadata attribute information.

Documentation

Using the Data

E-Learning

Observing Land from Space: Interacting with Geospatial Data from NASA's LP DAAC

View from NASA Terra's Zoom Lens: All About the ASTER Sensor

Data In Action

Highlights from the NASA DEVELOP National Program Spring 2017 Term

Sensing Our Planet: NASA Earth Science Research Features 2014

Highlights from the Literature: October to December 2014

Tools

Citation

DOI: 10.5067/ASTER/AST_08.003

About the Image

Terra ASTER surface kinetic temperature data from the AST_08 product over Guatemala on January 8, 2018.

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