Landsat Level-2 Provisional Surface Temperature products, which are part of the U.S. Landsat Analysis Ready Data (ARD) product bundle (Dwyer et al. 2018), were used for calculating LST. The Provisional Surface temperature values are computed from Landsat Collection 1 Level-1 thermal infrared bands and Top of Atmosphere (TOA) Reflectance. The calcuations are corrected for atmospheric variations between dates, sensors and locations (i.e., water vapor, ozone, aerosol optical thickness, clouds and digital elevation) using ancillary datasets such as Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Emissivity Database (GED) data, ASTER Normalized Difference Vegetation Index (NDVI) data, as well as atmospheric profiles, specific humidity, and air temperature from reanalysis data.
The Provisional Surface Temperature data were accessed using Earth Explorer (https://earthexplorer.usgs.gov/) in June 2021. All cloud-free (<1% cloud cover) images from June, July, and August during each year of analysis (1985, 1990, 1995, 2000, 2005, 2010, 2015, 2020) were used for the calculation. Temperature values in Kelvin were converted to Celsius, and a composite for each year was computed using the average of the input images. Compositing was completed in ArcGIS. Images were reprojected to NAD_1983_2011_StatePlane_Arizona_Central_FIPS_0202.
*Table 1*. Images included in yearly composites of LST. In some years (1985, 1995, 2015) only a single cloud free image was available during the summer months.
|year|images |
|:---|:-------------------------------------------- |
|1985|//LANDSAT/LT05/C01/T1_SR/LT05_037037_19850723 |
|1990|//LANDSAT/LT05/C01/T1_SR/LT05_037037_19900619 |
| |//LANDSAT/LT05/C01/T1_SR/LT05_037037_19900822 |
|1995|//LANDSAT/LT05/C01/T1_SR/LT05_037037_19950703 |
|2000|//LANDSAT/LT05/C01/T1_SR/LT05_037037_20000614 |
| |//LANDSAT/LT05/C01/T1_SR/LT05_037037_20000801 |
|2005|//LANDSAT/LT05/C01/T1_SR/LT05_037037_20050612 |
| |//LANDSAT/LT05/C01/T1_SR/LT05_037037_20050628 |
| |//LANDSAT/LT05/C01/T1_SR/LT05_037037_20050831 |
|2010|//LANDSAT/LT05/C01/T1_SR/LT05_037037_20100626 |
| |//LANDSAT/LT05/C01/T1_SR/LT05_037037_20100813 |
|2015|//LANDSAT/LC08/C01/T1_SR/LC08_037037_20150827 |
|2020|//LANDSAT/LC08/C01/T1_SR/LC08_037037_20200621 |
| |//LANDSAT/LC08/C01/T1_SR/LC08_037037_20200707 |
| |//LANDSAT/LC08/C01/T1_SR/LC08_037037_20200808 |
| |//LANDSAT/LC08/C01/T1_SR/LC08_037037_20200824 |
The intent is that the surface temperature can be used in time-series analysis, however, current products are only provisional and all users of the surface temperature product should include this disclaimer: “USGS Landsat Surface Temperature Science Product may report unvalidated results for certain observational conditions.” While the compositing step was performed to reduce outliers and value uncertainty, users should remain cautious in comparing raw values over time because the images are captured on different days/months under different meteorological conditions. Please see the Landsat Surface Temperature Product Guide (USGS 2018) and product overview (https://www.usgs.gov/centers/eros/science/usgs-eros-archive-landsat-archives-landsat-level-2-provisional-surface?qt-science_center_objects=0#qt-science_center_objects) for more information.
*References*
- Dwyer, J.L., Roy, D.P., Sauer, B., Jenkerson, C.B., Zhang, H., and Lymburner, L., 2018, Analysis ready data—Enabling analysis of the Landsat archive: Remote Sensing, v. 10, no. 9, art. no. 1363. doi.org/10.3390/rs10091363
- U.S. Geological Survey, Department of the Interior. (2018). “Landsat Provisional Surface Temperature Product Guide” LSDS-1330, Version 2.0. EROS: Sioux Falls, South Dakota. https://www.usgs.gov/media/files/landsat-provisional-surface-temperature-product-guide
