This repository contains several datasets of spectral atmospheric transfer functions (i.e. path radiance, transmittances, spherical albedo) simulated with MODTRAN6 atmospheric radiative transfer model. The simulations are stored in hdf5 files using the Atmospheric Look-up table Generator (ALG) toolbox (https://doi.org/10.5194/gmd-13-1945-2020). Each dataset has an associated .xml file that includes the configuration of ALG/MODTRAN6 executions. All datasets include the input atmospheric/geometric variables that are summarized in the following table. Each dataset file has a random distribution (based on latin hypercube sampling) these input variables with varying number of points (e.g. train500.h5 contains 500 samples). The reference dataset contains 10000 samples and was used as reference for evaluating Gaussian Processes emulators. Input Variables Units Min Max O3 column concentration atm-cm 0.25 0.45 Columnar Water Vapor g/cm2 0.2 4 Aerosol Optical Thickness - 0.04 0.6 Asymmetry parameter - 0.5 0.85 Angstrom exponent - 0.1 2 Single Scattering Albedo - 0.8 1 Surface elevation km 0 2.5 Solar Zenith Angle deg 0 70 Relative Zenith Angle deg 0 180