Ozone simulations with ICON for the improvement of UV predictions
Authors: Weber Simon , Ruhnke Roland , Scharun Christian , Seifert Axel , Braesicke Peter 
Published: March 2022

&lt;p&gt;&lt;span&gt;Ozone (O&lt;/span&gt;&lt;sub&gt;&lt;span&gt;3&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;) in the stratosphere absorbs the biologically harmful ultraviolet radiation from the sun (most of the UV-B radiation) and prevents it from reaching the earth's surface. The high-energy UV radiation can destroy genetic material in the cells of plants and animals, as well as humans. Without the stratospheric ozone layer, life on Earth as we know it would not be possible.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;The German Weather Service (DWD) provides UV index maps to inform and warn the population about high UV exposure [1]. For this purpose, data from the golobal forecast model ICON (ICOsahedral Non-hydrostatic model) [2], external ozone data and an own UV model are used to generate a forecast of the UV index, which is visualized e.g. on the DWD website as a forecast.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;In this project, a self-consistent framework is developed in cooperation with the DWD to generate UV index maps entirely in ICON. For this purpose, a linearized ozone scheme (LINOZ) [3] is optimized for daily ozone forecasts (including a procedure to create an initial ozone distribution). This is done as an extension of the ICON-ART structure [4] [5] (ART: Aerosols and Reactive Trace gases). A radiative transfer model for solar radiation (Cloud-J) [6] was implemented and adapted for the calculation of UV radiation fluxes and indices. Since the entire system is to be provided to the DWD as an efficient solution for UV index predictions, special emphasis is placed on comprehensive functionality at very low computational cost. An important part of the work is therefore also the validation and optimization of the procedures and workflows in order to produce reliable and high-quality forecasts.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;We present preliminary results of the UV radiative flux through the atmosphere modeled by ICON-ART on a global scale and over selected areas, its diurnal variation, and the influence of clouds on UV intensity.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Comment:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;This project is funded by the German Weather Service under Extramural Research with the following number: 4819EMF03.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;[1] https://kunden.dwd.de/uvi/index.jsp&lt;/p&gt;&lt;p&gt;[2] Z&amp;#228;ngl, G., et al., The ICON (ICOsahedral Non-hydrostatic) modelling framework of DWD MPI-M: Description of the non-hydrostatic dynamical core. Q.J.R. Meteorol. Soc., 141(687), 563-579 (2014)&lt;/p&gt;&lt;p&gt;[3] McLinden, C. A., et al., Stratospheric ozone in 3-D models: A simple chemistry and the cross-tropopause flux, Journal of Geophysical Research: Atmospheres, 105(D11), 14653-14665 (2000)&lt;/p&gt;&lt;p&gt;[4] Rieger, D., et al., ICON-ART - A new online-coupled model system from the global to regional scale, Geosci. Model Dev., 8(6), 1659-1676 (2015)&lt;/p&gt;&lt;p&gt;[5] Schr&amp;#246;ter, et al., ICON-ART 2.1: a flexible tracer framework and its application for composition studies in numerical weather forecasting and climate simulations. Geosci. Model Dev., 11(10), 4043-4068 (2018)&lt;/p&gt;&lt;p&gt;[6] Prather, M.J., Photolysis rates in correlated overlapping cloud fields: Cloud-J 7.3c. Geosci. Model Dev., 8(8), 2587-2595 (2015)&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;