Spectral longwave atmospheric irradiance determination for site-and date-specific passive radiative cooling modeling

Year: 2026

Authors: Belotti C., Manara J., Vidi S., Pattelli L., Hameury J.

Autors Affiliation: CNR, Ist Nazl Ott, INO, Via Madonna Piano 10, I-50019 Sesto Fiorentino, Firenze, Italy; Ctr Appl Energy Res CAE, Magdalene Schoch Str 3, D-97074 Wurzburg, Germany; Ist Nazl Ric Metrol INRiM, Str Cacce 91, I-10135 Turin, Italy; Lab Natl Metrol & essais LNE, 29 Ave Roger Hennequin, F-78190 Trappes, France.

Abstract: The effectiveness of passive radiative cooling is highly dependent on local atmospheric conditions, particularly the spectral distribution of downward longwave radiation. Many existing models rely on simplified or generalized assumptions such as fixed atmospheric profiles or empirical fits based on surface-level parameters that overlook important aspects of the vertical composition and spectral variability of the atmospheric column. In this work, we present a python-based workflow that generates site-and time-specific estimates of surface downward thermal radiation resolved into sixteen longwave spectral bands with hourly resolution. Our method combines reanalysis data from open ECMWF ERA5 and seasonal climatology data, and the RRTM_LW radiative transfer model, allowing for consistent incorporation of cloud effects based on the available input data. We demonstrate the application of this tool by constructing spectrally resolved Typical Meteorological Year (TMY) datasets and show how it can be used to improve energy balance calculations for radiative coolers. Comparisons with simplified approaches highlight the systematic errors arising when spectral and vertical atmospheric information are neglected.

Journal/Review: SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS

Volume: 91      Pages from: 105046-1  to: 105046-12

More Information: This work is supported by the European project PaRaMetriC, code 21GRD03. The project 21GRD03 PaRaMetriC received funding from the European Partnership on Metrology, co-financed by the European Union’s Horizon Europe Research and Innovation Programme, and from the Participating States.
KeyWords: Passive radiative cooling; Downwelling longwave atmospheric irradiance; Surface downward thermal radiation; ERA5 reanalysis; Radiative transfer modeling; Typical Meteorological Year; Thermal energy balance modeling
DOI: 10.1016/j.seta.2026.105046