Attenuation of UV-C Solar Radiation as a Function of Altitude (0 ≤ z ≤ 100 km): Rayleigh Diffusion and Photo Dissociation of O&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Influence

José Luis Pinedo-Vega,J Ignacio Dávila-Rangel,Sonia Azucena Saucedo-Anaya,Eduardo Manzanares-Acuña,David Jacobo Navarro-Solís,Carlos Ríos-Martínez,Valentín Badillo-Almaraz,Fernando Mireles-García

doi:10.4236/acs.2017.74039

Abstract

In this paper, we present an analysis of attenuation for UV-C radiation () as a function of the altitude z () by calculating the interaction ratio between the UV-C radiation and the molecular species susceptible of interact with UV-C radiation. The Rayleigh scattering spectral cross sections were calculated, the UV-C spectral cross sections of the species susceptible of interact with UV-C radiation and the UV extraterrestrial (ETR) solar spectrum were standardized with wavelength steps of 1 nm, and The International Standard Atmosphere model (ISO 1972) was adapted to calculate the molecular density. These data were utilized to calculate the photodissociation and Rayleigh scattering ratios as a function of the altitude and to determine to what measure the photodissociation and the Rayleigh diffusion were determinants of the attenuation of UV-C radiation. It became clear that the photo dissociation of O2 is the primordial mechanism of attenuation for the UV-C radiation, but the Rayleigh diffusion appears like a mechanism that encreases the photon flux, raising the performance of the O2 photodissociation. The attenuation capacities of N2O, CO2 and water vapor (H2O) over the UV-C radiation are all similar, although smaller (less than 0.6%), and this is due to their low concentration. The O3, has the theoretical greater attenuation capacity, but it is found in mid-range altitudes (), where the residual UV-C photons has almost vanished by O2 photo dissociation or Rayleigh diffusion, so the real effect over the UV-C attenuation is minimum.

Highlights

It is well known that UV-C radiation does not reach the surface of the Earth.there is no precise knowledge about its spectral attenuation.The attenuation of UV radiation, in general, is the result of the interaction of the photons with the species or molecules that are susceptible to interact
We present an analysis of attenuation for UV-C radiation ( λ ≤ 290 nm ) as a function of the altitude z (0 ≤ z ≤ 100 km) by calculating the interaction ratio between the UV-C radiation and the molecular species susceptible of interact with UV-C radiation
It became clear that the photo dissociation of O2 is the primordial mechanism of attenuation for the UV-C radiation, but the Rayleigh diffusion appears like a mechanism that encreases the photon flux, raising the performance of the O2 photodissociation

Summary

Introduction

There is no precise knowledge about its spectral attenuation. The attenuation of UV radiation, in general, is the result of the interaction of the photons with the species or molecules that are susceptible to interact. The spectral photodissociation ratio Rλ ( z) can be defined as the number of molecular photodissociation produced by the solar radiation of each wavelength λ at any altitude in the atmosphere. This must be proportional to the spectral photon flow φλ ( z ) and to the molecular density N ( z ) of each chemical species at z altitude

Methods

Results

Conclusion