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Oceanic very short-lived substances (VSLSs), such as bromoform (CHBr3), contribute to stratospheric halogen loading and, thus, to ozone depletion. However, the amount, timing, and region of bromine delivery to the stratosphere through one of the main entrance gates, the Indian summer monsoon circulation, are still uncertain. In this study, we created two bromoform emission inventories with monthly resolution for the tropical Indian Ocean and west Pacific based on new in situ bromoform measurements and novel ocean biogeochemistry modeling. The mass transport and atmospheric mixing ratios of bromoform were modeled for the year 2014 with the particle dispersion model FLEXPART driven by ERA-Interim reanalysis. We compare results between two emission scenarios: (1) monthly averaged and (2) annually averaged emissions. Both simulations reproduce the atmospheric distribution of bromoform from ship- and aircraft-based observations in the boundary layer and upper troposphere above the Indian Ocean reasonably well. Using monthly resolved emissions, the main oceanic source regions for the stratosphere include the Arabian Sea and Bay of Bengal in boreal summer and the tropical west Pacific Ocean in boreal winter. The main stratospheric injection in boreal summer occurs over the southern tip of India associated with the high local oceanic sources and strong convection of the summer monsoon. In boreal winter more bromoform is entrained over the west Pacific than over the Indian Ocean. The annually averaged stratospheric injection of bromoform is in the same range whether using monthly averaged or annually averaged emissions in our Lagrangian calculations. However, monthly averaged emissions result in the highest mixing ratios within the Asian monsoon anticyclone in boreal summer and above the central Indian Ocean in boreal winter, while annually averaged emissions display a maximum above the west Indian Ocean in boreal spring. In the Asian summer monsoon anticyclone bromoform atmospheric mixing ratios vary by up to 50 % between using monthly averaged and annually averaged oceanic emissions. Our results underline that the seasonal and regional stratospheric bromine injection from the tropical Indian Ocean and west Pacific critically depend on the seasonality and spatial distribution of the VSLS emissions.

Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community. International audience

Table of Contents 1. Introduction 1.1. The project AstRoMap within the Framework Programme for Research and Innovation (FP7) of the European Union 1.2. The European astrobiology environment and landscape in Europe 1.3. Setting the scene: timeline and astrobiology concepts 2. The Astrobiology Roadmap for Europe 3. Research Topic 1: Origin and Evolution of Planetary Systems 3.1. State of the art 3.2. Key objectives 3.3. Approach to achieve the key objectives 3.4. European strengths and needs 4. Research Topic 2: Origins of Organic Compounds in Space 4.1. State of the art 4.2. Key objectives 4.3. Approach to achieve the key objectives 4.4. European strengths and needs 5. Research Topic 3: Rock-Water-Carbon Interactions, Organic Synthesis on Earth, and Steps to Life 5.1. State of the art 5.2. Key objectives 5.3. Approach to achieve the key objectives 5.4. European strengths and needs 6. Research Topic 4: Life and Habitability 6.1. State of the art 6.2. Key objectives 6.3. Approach to achieve the key objectives 6.4. European strengths and needs 7. Research Topic 5: Biosignatures as Facilitating Life Detection 7.1. State of the art 7.2. Key objectives 7.3. Approach to achieve the key objectives 7.4. European strengths and needs 8. Conclusions and Recommendations 8.1. Cross-cutting issues of relevance 8.2. Towards a better coordination of astrobiology research in Europe—the need for a pan-European platform Acknowledgments References Abbreviations Used Abstract The European AstRoMap project (supported by the European Commission Seventh Framework Programme) surveyed the state of the art of astrobiology in Europe and beyond and produced the first European roadmap for astrobiology research. In the context of this roadmap, astrobiology is understood as the study of the origin, evolution, and distribution of life in the context of cosmic evolution; this includes habitability in the Solar System and beyond. The AstRoMap Roadmap identifies five research topics, specifies several key scientific objectives for each topic, and suggests ways to achieve all the objectives. The five AstRoMap Research Topics are • Research Topic 1: Origin and Evolution of Planetary Systems• Research Topic 2: Origins of Organic Compounds in Space• Research Topic 3: Rock-Water-Carbon Interactions, Organic Synthesis on Earth, and Steps to Life• Research Topic 4: Life and Habitability• Research Topic 5: Biosignatures as Facilitating Life Detection It is strongly recommended that steps be taken towards the definition and implementation of a European Astrobiology Platform (or Institute) to streamline and optimize the scientific return by using a coordinated infrastructure and funding system. Key Words: Astrobiology roadmap—Europe—Origin and evolution of life—Habitability—Life detection—Life in extreme environments. Astrobiology 16, 201–243.

Isolated anticyclones are frequently observed below the mixed layer in the Arctic Ocean. Some of these sub-surface anticyclones are thought to originate at surface fronts. However, previous idealized simulations with no surface stress show that only cyclone-anticyclone dipoles can propagate away from baroclinically unstable surface fronts. Numerical simulations of fronts subject to a surface stress presented here show that a surface stress in the same direction as the geostrophic flow inhibits dipole propagation away from the front. On the other hand, a surface stress in the opposite direction to the geostrophic flow helps dipoles to propagate away from the front. Regardless of the surface stress at the point of dipole formation, these dipoles can be broken up on a timescale of days when a surface stress is applied in the right direction. The dipole breakup leads to the deeper anticyclonic component becoming an isolated sub-surface eddy. The breakup of the dipole occurs because the cyclonic component of the dipole in the mixed layer is subject to an additional advection due to the Ekman flow. When the Ekman transport has a component oriented from the anticyclonic part of the dipole towards the cyclonic part then the cyclone is advected away from the anticyclone and the dipole is broken up. When the Ekman transport is in other directions relative to the dipole axis it also leads to deviations in the trajectory of the dipole. A scaling is presented for the rate at which the surface cyclone is advected that holds across a range of mixed layer depths and surface stress magnitudes in these simulations. The results may be relevant to other regions of the ocean with similar near-surface stratification profiles. International audience

Multilayer clouds (MLC) occur more often in the Arctic than globally. In this study a ground-based detection algorithm is developed using radiosoundings and radar from an one-year time period in Ny-Ålesund, Svalbard. The detection algorithm results in a multilayer cloud occurrence of 29 % of the investigated days. These multilayer cloud cases are further analysed regarding the possibility of ice crystal seeding. Ice crystal seeding means that an ice crystal can survive sublimation in a subsaturated layer between two cloud layers when falling through this layer. For this we analyse height profiles of relative humidity with respect to ice to identify super- and subsaturated air layers. Then the sublimation of an ice crystal of an assumed initial size of r = 100 μm on its way through the subsaturated layer is calculated. If the ice crystal still exists when reaching a lower supersaturated layer, ice crystal seeding can potentially take place. Seeding cases are found often, in 23 % of the investigated days. The identification of seeding cases is limited by the radar signal inside the subsaturated layer. Clearly separated multilayer clouds, defined by a clear interstice in the radar image, do not interact through seeding (9 % of the investigated days). Since there are various deviations between the relative humidity profiles and the radar images, for the non-seeding cases an evaluation by manual visual inspection is additionally done.

Seeking for baseline conditions has biased the atmospheric carbon dioxide (CO₂) and later on also oxygen (O₂) monitoring networks towards remote marine stations, missing part of the variability that is due to regional anthropogenic as well as land biotic activity. We present here a five-year record of atmospheric CO₂ concentrations and oxygen/nitrogen (O₂/N₂) ratio measurements from the coastal stations Lutjewad (LUT), The Netherlands and Mace Head (MHD), Ireland, derived from flask samples. O₂/N₂ ratios, a proxy for O₂ concentrations, concurrently measured with CO₂ concentrations, help determine regional CO₂ fluxes by separating land fluxes from sea fluxes. Mace Head is the closest marine baseline station to Lutjewad, located at the same latitude, and therefore is taken as a reference. During the studied period, from 2000 until 2005, we observed an average increase of CO₂ in the atmosphere of (1.7±0.2) ppm y^−1, and a change of the O₂/N₂ ratio of (−20±1) per meg y^−1. The difference between the CO₂ summer minimum and the winter maximum is 14.4 ppm and 16.1 ppm at Mace Head and Lutjewad, respectively, while the paraphase variation in the O₂ signal equals 113 per meg and 153 per meg, respectively. We also studied the atmospheric potential oxygen (APO) tracer at both stations. By this analysis, evidence has been found that we need to be careful when using APO close to anthropogenic CO₂ sources. It could be biased by combustion-derived CO₂, and models need to take into account daily and seasonal variations in the anthropogenic CO₂ production in order to be able to simulate APO over the continents.