A Principal Component-based Radiative Transfer Model (PCRTM), which can calculate TOA radiance or reflectance spectra from 50 cm^-1 to 40,000 cm^-1 (200 mm to 0.25 mm) was developed. It demonstrated very good accuracy relative to reference Line-by-Line radiative transfer models and saves orders of magnitude in computational time. The PCRTM performs radiative transfer calculation in a limited number of monochromatic wavelengths, which avoids the approximation assumptions that are made in the correlated-K method. The PCRTM model was developed for hyperspectral sensors such as AIRS, CrIS, IASI, NAST-I, SHIS, FIRST, and CLARREO-IR in the thermal IR spectral region and CLARREO-Solar, CPF, TEMPO, EMIT, OMI, and SCIAMACHY in the solar spectral region. The PCRTM's accuracy was demonstrated via RTM intercomparisons and with real satellite observations from AIRS, CrIS, IASI, SCIAMACHY, EMIT, etc. The PCRTM has been used in many satellite remote sensing applications. Examples include forward modeling in Level-2 and Level-3 retrieval algorithms, high-fidelity satellite instrument simulators and instrument performance trade studies, spectral and radiometric accuracy characterizations of satellite Level-1 data, tools for inter-satellite calibrations, tools for satellite RTM lookup table generations, and tools for generating physically based training datasets for Artificial Intelligence (AI) algorithms.

The sixth report of IPCC 2023 indicates that the situation of the planet is not encouraging: global emissions of greenhouse gases continue to increase, the effects of rising temperatures are increasingly evident, there is a growing degradation of the coasts, sea levels are rising, and beach erosion is accelerating. The present work aims to evaluate the multi-decadal changes of Topocalma beach, located in Litueche, O’Higgins Region, Chile. Characterization of the beach changes was carried out using Landsat imagery (5 TM, 7 ETM+, 8 OLI and 9 OLI) and Sentinel-2, with in situ data and hydrodynamic and climatic data. The CoastSat algorithm was used to obtain more than 350 shorelines' positions, obtained between 1985 and 2004. Spatial pattern variability associated with climatic events, such as the earthquake–tsunami in 2010 and storm surges from 2015 to 2023, was quantified. The beach waves show intra-seasonal and inter-annual variability, with an average height of 2.5 m related to ENSO (El Niño Southern Oscillation) and SAM (Southern Annular Mode) events. Regarding the beach, there is evidence that in the distal section, the erosion predominates in multi-year phases (1991-1992; 1996; 2000; 2005; 2008; 2023-2024), while in the proximal section, there is a clear dominance of recovery/accumulation influenced by Topocalma wetland. The beach shows a -0.41m/year rate of erosion for the entire series of this study. From 2015, with the increase in storm surges, there is evidence of progressive changes in the decrease in the net width of the beach (rates from -0,2 m/year to -1,5 m/year), an erosive trend that is maintained until the end of the series. The use of free-access satellite imagery provides valuable information for coastal management related to the erosion, which in turn contributes to territorial planning for the protection of communities and coastal ecosystems.