Satellite measurements of the atmospheric concentrations of carbon dioxide (CO2), methane (CH4) and carbon monoxide (CO) require careful validation. In particular for the greenhouse gases CO2 and CH4, concentration gradients are minute challenging the ultimate goal to quantify and monitor anthropogenic emissions and natural surface-atmosphere fluxes. The upcoming European Copernicus Carbon Monitoring mission (CO2M) will focus on anthropogenic CO2 emissions, but it will also be able to measure CH4. There are other missions such as the Sentinel-5 Precursor and the Sentinel-5 series that target CO which helps attribute the CO2 and CH4 variations to specific processes. Here, we review the capabilities and use cases of a mobile ground-based sun-viewing spectrometer of the type EM27/SUN. We showcase the performance of the mobile system for measuring the column-average dry-air mole fractions of CO2 (XCO2), CH4 (XCH4) and CO (XCO) during a recent deployment (Feb./Mar. 2021) in the vicinity of Japan on research vessel Mirai which adds to our previous campaigns on ships and road vehicles. The mobile EM27/SUN has the potential to contribute to the validation of 1) continental-scale background gradients along major ship routes on the open ocean, 2) regional-scale gradients due to continental outflow across the coast line, 3) urban or other localized emissions as mobile part of a regional network and 4) emissions from point sources. Thus, operationalizing the mobile EM27/SUN along these use cases can be a valuable asset to the validation activities for CO2M, in particular, and for various upcoming satellite missions in general.

<p>The ICOsahedral Non-hydrostatic (ICON) modelling system was originally developed by DWD and MPI-M for a range of weather (forecast) and climate applications. An Aerosols and Reactive Tracers (ART) module was added by KIT to enable a comprehensive assessment of composition interactions within the atmospheric domain. Recognising that atmospheric processes happen on a multitude of temporal and spatial scales, flexible horizontal and vertical grid options are a key element of versatile model configurations in use. Here, we present a selection of results from different ICON-ART configurations that explore (stratospheric) ozone-climate interactions and stratosphere-troposphere coupling – e.g. regional climatic impacts of the ozone hole (and ozone losses in other regions) and global warming induced changes in jet-streams – in different types of integrations. In addition, we explore the potential to forecast “chemical weather” with ICON-ART, including environmental (UV) indices.</p> <p>Starting with time-slice experiments, we provide a range of examples using the ICON-ART modelling system to investigate (idealised) climate change scenarios with respect to different threshold temperatures (reached under global warming) and the climatic impact of the ozone hole (and ozone losses in other regions). For the latter, halogen induced depletion of (stratospheric) ozone can be switched on and off in our modelling world. We illustrate how such integrations allow the unambiguous attribution of certain climate change effects, e.g. the contribution of the ozone hole (and other regional ozone losses) to regional surface warming in Antarctica and changes to regional and global “effective radiative forcing”, and the change of jet stream variability under global warming. Moving on, we explore the capability of ICON-ART to work with regionally nested grids to capture accurately smaller spatial scales and to provide “meaningful” forecasts of environmental (UV) indices, thus, demonstrating comprehensively the seamless philosophy regarding processes, scales and applications with the flexible ICON-ART modelling system.</p>

<p><span>Stratospheric ozone (O</span><span>3</span><span>) absorbs biologically harmful solar ultraviolet radia</span><span>tion, mainly in the UV_B and UV_C spectral range. When reaching the surface, </span><span>such UV radiation poses a well documented hazard to human health. In order to</span> <span>quantify this amount of UV radiation and to make it generally understandable, t</span><span>he World Health Organization has defined an UV Index[1].</span> <span>It is calculated </span><span>by weighting the incoming solar irradiance at surface level between 250 and 400</span> <span>nanometers with their ”harmfulness” to the skin and scaling the results to values </span><span>that normally range between 1 and 10, surpassing 10 for excessive UV exposure.</span></p><p><span>Implementing UV Index forecasts in numerical weather prediction (NWP) </span><span>models allows to alert the public in time if special care for sun protection needs</span><br><span>to be taken. The German Weather Service (DWD) uses its NWP model ICON </span><span>(ICOsahedral Nonhydrostatic Model)[2] to offer such a forecast for Germany[3]</span><br><span>using external data such as ozone forecasts by the Royal Dutch Weather Service </span><span>(KNMI) and radiation lookup tables[4].</span></p><p><br><span>In our project we extend the capability of ICON to provide a configura</span><span>tion of self-consistent UV Index forecasts that do not require external data. </span><span>For this, we use ICON-ART[5],[6] with a linearized ozone scheme (LINOZ)[7]</span> <span>and couple the prognostic ozone to the atmospheric radiation scheme Solar-J[8].</span><br><span>Here we present the current state of our UV Index forecast system and </span><span>compare our results to available reference data.</span></p><p><span>References:</span></p><p><span>[1] World Health Organization, World Meteorological Organization, United Nations Environment Programme, and International Commission on Non-<br>Ionizing Radiation Protection. Global solar uv index : a practical guide,2002.</span></p><p><span>[2] Günther Zängl et al.. The icon (icosahedral non-hydrostatic) modelling framework of dwd and mpi-m:<br>Description of the non-hydrostatic dynamical core. Quarterly Journal of the Royal Meteorological Society, 2015.</span></p><p><span>[3] https://kunden.dwd.de/uvi/index.jsp.</span></p><p><span>[4] Henning Staiger and Peter Koepke. Uv index forecasting on a global scale. Meteorologische Zeitschrift, 2005.</span></p><p><span>[5] D. Rieger et al.. Icon–art 1.0 – a new online-coupled model system from the global to regional scale. Geoscientific Model Development, 2015.</span></p><p><span>[6] J. Schröter et al.. Icon-art 2.1: a flexible tracer framework and its application for composition studies in numerical weather forecasting and climate simulations. </span><span>Geoscientific Model Development, 2018.</span></p><p><span>[7] C. A. McLinden et al. Stratospheric ozone in 3-d models: A simple chemistry and the cross-tropopause flux. Journal of Geophysical Research: Atmospheres, 2000</span></p><p><span>[8] J. Hsu, M. J. Prather et al.. A radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-j v7.5. Geoscientific Model Development, 2017.</span></p>

<p>Validation opportunities for model data and satellite observations in the short-wave infra-red spectral range for climate monitoring are still sparse above the oceans. Klappenbach et al. (2015) and Knapp et al. (2020) developed a ship-borne setup of a Fourier-transform spectrometer (EM27/SUN FTS) for direct sunlight observations on mobile platforms such as ships or pick-ups. The housing withstands oceanic on-deck-conditions and is equipped with a custom-built fast solar tracker. Knapp et al. (2020) tested the system on a ship cruise from Vancouver, Canada to Singapore for a five-week period in 2019, during which the instrument performed reliably. The tracker provided a pointing precision of better than 0.05° for 79% of the time. The precision of atmospheric total column densities retrieved from the FTS direct sunlight spectra was found to be 0.24ppm for carbon dioxide (CO<sub>2</sub>), 1.1ppb for methane (CH<sub>4</sub>), and 0.75ppb for carbon monoxide (CO).</p><p>Our ultimate goal is to develop the setup towards autonomous operations on ships to routinely collect validation data for CO<sub>2</sub>, CH<sub>4</sub>, and CO column densities above the world's oceans. Therefore, we further improved on the FTS box. Most prominent is a simplification of the tracking algorithm from two-dimensional mapping to two one-dimensional functions, moving a 185° fisheye camera onto the tracking rotation stage, and a change to more reliable embedded computers. Those modifications allow for sun tracking down to a solar zenith angle of 75° and increase robustness against mechanical misalignments between tracker and camera. A test campaign was conducted in the vicinity of a local coal power plant in Mannheim, Germany by mounting the FTS box on a pick-up and driving a stop-and-go pattern perpendicular to the plume direction. To this purpose, a 24 V battery powering mode was implemented.</p><p>We plan another deployment of the instrument on the Japanese research vessel Mirai in February 2021. The campaign is conducted in cooperation with the Japanese National Institute for Environmental Studies (NIES) in the western North Pacific. Such routine validation opportunities of atmospheric CO<sub>2</sub>, CH<sub>4</sub>, and CO column densities would be a valuable asset for global climate monitoring.</p><p> </p><p> </p><p>Knapp, M., Kleinschek, R., Hase, F., Agustí-Panareda, A., Inness, A., Barré, J., Landgraf, J., Borsdorff, T., Kinne, S., and Butz, A.: Ship-borne measurements of XCO2, XCH4, and XCO above the Pacific Ocean and comparison to CAMS atmospheric analyses andS5P/TROPOMI, Earth System Science Data Discussions, 2020, 1–20, https://doi.org/10.5194/essd-2020-132, https://essd.copernicus.org/preprints/essd-2020-132/, 2020.</p><p>Klappenbach, F., Bertleff, M., Kostinek, J., Hase, F., Blumenstock, T., Agusti-Panareda, A., Razinger, M., and Butz, A.: Accurate mobileremote sensing of XCO2 and XCH4 latitudinal transects from aboard a research vessel, Atmospheric Measurement Techniques, 8,5023–5038, https://doi.org/10.5194/amt-8-5023-2015, 2015.</p>