4 research outputs found
A physics-constrained machine learning method for mapping gapless land surface temperature
More accurate, spatio-temporally, and physically consistent LST estimation
has been a main interest in Earth system research. Developing physics-driven
mechanism models and data-driven machine learning (ML) models are two major
paradigms for gapless LST estimation, which have their respective advantages
and disadvantages. In this paper, a physics-constrained ML model, which
combines the strengths in the mechanism model and ML model, is proposed to
generate gapless LST with physical meanings and high accuracy. The hybrid model
employs ML as the primary architecture, under which the input variable physical
constraints are incorporated to enhance the interpretability and extrapolation
ability of the model. Specifically, the light gradient-boosting machine (LGBM)
model, which uses only remote sensing data as input, serves as the pure ML
model. Physical constraints (PCs) are coupled by further incorporating key
Community Land Model (CLM) forcing data (cause) and CLM simulation data
(effect) as inputs into the LGBM model. This integration forms the PC-LGBM
model, which incorporates surface energy balance (SEB) constraints underlying
the data in CLM-LST modeling within a biophysical framework. Compared with a
pure physical method and pure ML methods, the PC-LGBM model improves the
prediction accuracy and physical interpretability of LST. It also demonstrates
a good extrapolation ability for the responses to extreme weather cases,
suggesting that the PC-LGBM model enables not only empirical learning from data
but also rationally derived from theory. The proposed method represents an
innovative way to map accurate and physically interpretable gapless LST, and
could provide insights to accelerate knowledge discovery in land surface
processes and data mining in geographical parameter estimation
Validation of AVHRR Land Surface Temperature with MODIS and In Situ LST—A TIMELINE Thematic Processor
Land Surface Temperature (LST) is an important parameter for tracing the impact of changing climatic conditions on our environment. Describing the interface between long- and shortwave radiation fluxes, as well as between turbulent heat fluxes and the ground heat flux, LST plays a crucial role in the global heat balance. Satellite-derived LST is an indispensable tool for monitoring these changes consistently over large areas and for long time periods. Data from the AVHRR (Advanced Very High-Resolution Radiometer) sensors have been available since the early 1980s. In the TIMELINE project, LST is derived for the entire operating period of AVHRR sensors over Europe at a 1 km spatial resolution. In this study, we present the validation results for the TIMELINE AVHRR daytime LST. The validation approach consists of an assessment of the temporal consistency of the AVHRR LST time series, an inter-comparison between AVHRR LST and in situ LST, and a comparison of the AVHRR LST product with concurrent MODIS (Moderate Resolution Imaging Spectroradiometer) LST. The results indicate the successful derivation of stable LST time series from multi-decadal AVHRR data. The validation results were investigated regarding different LST, TCWV and VA, as well as land cover classes. The comparisons between the TIMELINE LST product and the reference datasets show seasonal and land cover-related patterns. The LST level was found to be the most determinative factor of the error. On average, an absolute deviation of the AVHRR LST by 1.83 K from in situ LST, as well as a difference of 2.34 K from the MODIS product, was observed
Evaluation of MODIS LST Products Using Longwave Radiation Ground Measurements in the Northern Arid Region of China
This study presents preliminary results of the validation of the Moderate Resolution Imaging Spectroradiometer (MODIS) daily LST products (MOD/MYD11A1, Version 5) using longwave radiation ground measurements obtained at 12 stations in the North Arid and Semi-Arid Area Cooperative Experimental Observation Integrated Research program. In this evaluation process, the broadband emissivity at each station was obtained from the ASTER Spectral Library or estimated from the MODIS narrowband emissivity Collection 5. A comparison of the validation results based on those two methods shows that no significant differences occur in the short-term validation, and a sensitivity analysis of the broadband emissivity demonstrates that it has a limited effect on the evaluation results. In general, the results at the 12 stations indicate that the LST products have a lower accuracy in China’s arid and semi-arid areas than in other areas, with a mean absolute error of 2–3 K. Compared with the temporal mismatch, the spatial mismatch has a stronger effect on the validation results in this study, and the stations with homogeneous land cover have more comparable MODIS LST accuracies. Comparisons between the stations indicate that the spatial mismatch can increase the influence of the temporal mismatch