A new approach to determine the Top of Atmosphere earth Outgoing Radiation using the Geant4 toolkit

Monitoring accurately the amount of the incoming solar radiation reaching the ground surface and the outgoing radiation at the top of the atmosphere (TOA) is crucial for quantifying the earth's energy budget as well as for understanding and modelling the climate system and its evolution. In the present investigation, we explore the use of the Geant4 Monte Carlo toolkit and a new reference spectrum SOLAR/SOLSPEC [1] to develop a new model to estimate the spectral distribution of Top of Atmosphere Outgoing Radiation (TOR). The system is implemented in Geant4, a toolkit [2] that simulates the passage of particles through matter. SOLAR-ISS is a high resolution solar spectrum with a mean absolute uncertainty of 1.26% at 1σ. The TOR is estimated for a clear atmosphere and at different air mass (AM). For quality analysis, the performance of this model is examined and evaluated by comparing Geant4 simulation results with those of the DISORT code, where the relative mean difference is less than 7.29% overall the spectral domain from 280 to 3000 nm for a well defined case. The characteristics, such as transmittance and reflectance, etc., of the present and previous results will be analysed and compared to evaluate the performance of Geant4. We can upgrade the current tools with more powerful, efficient, and accurate prototyping. Furthermore, We will consider the design of a graphical user interface for the creation of the simulation input file, this utility will serve as a guideline that helps the user to run a simulation.