Applications of LST
Validation of LST is of crucial importance for estimating the accuracy of the products and understanding the potential and limitations of satellite observations of LST. Validation of LST is generally carried out using a variety of techniques:
Comparison of satellite LST with in situ measurements
This is the traditional and most straightforward approach to validating LST. It involves a direct comparison of satellite-derived LST with collocated and simultaneously acquired LST from ground-based or airborne radiometers.
Comparison between AATSR LST and in situ LST data over the ARM-Oklahoma field site from 2004 to 2010 inclusive. The dashed lines show the target accuracy of the AATSR LST product during the day (red) and night (blue). The error bars represent the estimated errors on the point in situ LST observations
Comparison between AATSR LST and in situ LST data over the ARM-Niamey field site for 2006 inclusive. The dashed lines show the target accuracy of the AATSR LST product during the day (red) and night (blue). The error bars represent the estimated errors on the point in situ LST observations
This technique uses top-of-atmosphere brightness temperatures in conjunction with a radiative transfer model to simulate ground LST using data of surface emissivity and an atmospheric profile.
Inter-comparison with other LST products
A wide variety of spaceborne instruments collects thermal infrared data and many provide operational LST products. An inter-comparison of LST products from different satellite instruments can be very valuable for determining LST
Daytime inter-comparison over southern Europe between AATSR average monthly LST and SEVIRI average monthly LST for June 2006
Daytime inter-comparison over southern Europe between AATSR average monthly LST and SEVIRI average monthly LST for December 2006
Time-series analysis of the same product
Analysing time series of satellite data over a temporally stable target site allows for the identification of potential calibration drift or other issues of the instrument that manifest themselves over time. Care must be taken in distinguishing between instrument-related issues such as calibration drift and real geophysical changes of the target site or the atmosphere.
Performing a sensitivity analysis enables any sources of bias in the LST product to be quantified. Such biases may result not only from cloud contamination or instrument -related problems, but also from the LST retrieval coefficients and the tuning parameters utilised in the LST retrieval process.
Sensitivity results for the AATSR LST algorithm (nadir view geometry) for biome 20 for varying atmospheric water vapour, atmospheric temperature, and skin temperature. ‘Tropical’ (red), ‘Mid-latitude’ (green), ‘Polar-Winter’ (light blue) and ‘Polar-Summer’ (purple) refer to the reference atmosphere used in each case.
Information about previous AATSR LST Validation can be found in the original
AATSR LST Validation Report
and in many publications (see Documentation section)