GOES-R Land Surface Temperature
Frequently Asked Questions about the GOES-R Land Surface Temperature Product
1) What is this product?
The GOES-R Land Surface Temperature product produces land surface temperature in degrees K (which is converted to degrees F locally in AWIPS) for all clear pixels. The resolution of this product is 2km. The GOES-R Land Surface Temperature product is created both day and night. It is accurate to within 3 degrees C. The product has a range of -60 degrees C to 57 degrees C. The GOES-R Land Surface Temperature product is considered quantitative for less than 70 degrees local zenith angle. At larger zenith angles, it is considered qualitative.1
This product is useful when trying to assess the temperature at ground level, especially over areas where in-situ temperature readings are not available.
2) How often do I receive this data?
The cadence of the Land Surface Temperature product is every 60 minutes for FD, CONUS, and Mesoscale images
3) How do I display this product in AWIPS-II?To display this product in AWIPS-II, go to the "GOES-R" tab of the CAVE menu, then select "Derived Products." From there, select the region of interest (GOES-E, GOES-W, or GOES Test), then FD Then, select the Land Surface Temperature product.
Alternately, use the AWIPS Product Browser. Select "Sat", then either "GOES-16" or "GOES-17". From there, choose "Full Disk" and select "LST."
4) How do I interpret the color maps associated with this product?
Color maps have not yet been created for this product.
5) What other imagery/products might I use in conjunction with this product?
This product can be used in conjunction with surface observations to better identify the location of air masses. This product can also be used to identify temperatures in areas of no direct observations (due to remoteness or technological issues). This product can also be used to assess the stability of the atmosphere when overlayed in AWIPS with the GOES-R Derived Stability Indices or model-derived stability parameters.
6) How is this product created?
The GOES-R Land Surface Temperature product is only calculated on pixels that are determined to be clear by the GOES-R Cloud Mask algorithm. It utilizes GOES-R bands 11.2 um and 12.3 um. The GOES-R Cloud Top Height product relies on the infrared observations to avoid discontinuities associated with the transition from day to night.
The derived data used to calculate the cloud top height include1:
- GOES-R Cloud Mask product - The ABI cloud mask (ACM) algorithm generates the option 1 product of a binary clearsky mask, as well as a 4-level cloud mask which indicates four cloudiness conditions for each pixel: clear, probably clear, probably cloudy, and cloudy.
- GOES-R Snow Cover product - Currently, snow cover is an ABI level-2 product measured as a fraction of snow cover (FSC) with a refresh rate of 60 minutes and ice cover is another ABI level-2 product with a refresh rate of every 180 minutes. It is expected that an intermediate snow/ice mask will be derived from these ABI level-2 products. Meanwhile we suggest applying a threshold of FSC >50% for generating a snow mask intermediate product.
- GOES-R Total Precipitable Water product - The GOES-R AWG sounding team has developed the algorithm to generate the TPW as one of the baseline products, covering CONUS, full disk and mesoscale, with a horizontal resolution of 10 km and accuracy at 1 mm and precision at 3 mm. This product offers better quality, higher spatial and temporal resolutions than the current NCEP forecast data. It is our intention to use the ABI TPW as the LST algorithm input upon availability and further test for meeting the LST requirement.
- GOES-R Land Surface Emissivity - Land surface emissivity is an option-2 ABI product retrieved using time continuity. Currently, it is developed for CONUS only, with a spatial resolution of 10 km and a precision of 0.06 refreshed every 6 hours. Again this product would be the preferred input to LST algorithm because of the higher spatial, temporal resolutions and better quality in comparison to the monthly mean emissivity retrieval.
The ancillary data used to calculate the cloud top height include1:
- Land Sea Mask - The 1 km resolution land/sea mask will be used for GOES-R ABI products. It is created by SSEC/CIMSS based on NASA MODIS collection 5. Several categories are available in the land/sea mask, including shallow, moderate and deep oceans, land, shoreline, shallow, ephemeral, and deep inland water. LST will be calculated for all land and inland water pixels.
Water Vapor - The water vapor information is extracted from the NCEP analysis and model forecast data. The Aviation model (AVN) provides global forecast every six hours and files in grib format can be downloaded through FTP. Currently we are using the 1° global coverage file, which may be replaced by higher resolution coverage at 0.25° in the future. An index file is available to point each ABI pixel to the corresponding TPW grid in the grib file.
Emissivity - The Global Infrared Land Surface Emissivity is downloaded from the UW-Madison Baseline Fit Emissivity Database (http://cimss.ssec.wisc.edu/iremis/). This global database of infrared land surface emissivity is derived using input from the Moderate Resolution Imaging Spectroradiometer (MODIS) operational land surface emissivity product (MOD11). The baseline fit method (Seemann et al., 2007), based on a conceptual model developed from laboratory measurements of surface emissivity, is applied to fill in the spectral gaps between the six emissivity wavelengths available in MOD11. Emissivity in the baseline fit database is available globally at ten wavelengths (3.6, 4.3, 5.0, 5.8, 7.6, 8.3, 9.3, 10.8, 12.1, and 14.3 microns) with 0.05 degree spatial resolution. Corresponding emissivity values will be extracted and mapped into the ABI full disk area. They can then be applied to the LST algorithm to generate LST products.
Snow/Ice Mask - The IMS snow and ice product is available daily for northern hemisphere. It incorporates a wide variety of satellite imagery (AVHRR, GOES, SSMI, etc.) as well as derived mapped products (USAF Snow/Ice Analysis, AMSU, AMSR-E, NCEP models, etc.) and surface observations. The product is presently used as an operational input into several NWS computer weather prediction models as well as several other governmental agencies. Currently it is available at about 4 km (6144x6144) grid from NSIDC with a slight delay. Near real-time gridded data is available in ASCII format by request (http://www.natice.noaa.gov/ims/).
It is worth noting that LST is generated for snow/ice pixels but indicated with QC flags. Therefore the requirement for snow/ice mask is limited for the QC flag control. It is also worth noting that current ABI snow/ice product is quantitative out to 55 degree of LZA and qualitative beyond that, while the LST is required to be out to 70 degree. A product quality information (PQI) flag is defined to indicate the LST is derived within 55° LZA, or alternative snow/ice mask will be used. 1
In addition to the sensor data and the ancillary data, algorithm coefficients and some criterion values for algorithm selection and for quality control flags will be ingested as the input data.
1Yu, Yunyue, Dan Tarpley, Hui Xu, and Ming Chen. NOAA NESDIS Center for Satellite Applications and Research GOES-R Advanced Baseline Imager (ABI) Algorithm Theoretical Basis Document for Land Surface Temperature v.2.0. 21 September 2010. http://www.goes-r.gov/products/ATBDs/baseline/baseline-LST-v2.0.pdf