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The effective radiative forcing (ERF) from aerosols and chemically reactive gases is calculated for several of the models that contributed to the CMIP6 project. The design of the experiments allowed for the calculation of the ERF due to each individual aerosol and gas, although where the aerosol and chemistry were modelled as interactive processes additional diagnostics were used to understand how these processes contributed to the overall ERF. The control used was the emission or concentration of the species in 1850 (considered the pre-industrial baseline for these experiments), with the perturbation using a specified emission or concentration of the species based on 2014 values as the present-day value. The experiments were run over a period of 30 years, with sea-surface temperatures held constant, and the ERF was obtained as the net change in TOA radiative flux between the perturbed and control run.The aerosols considered were black carbon (BC), organic carbon (OC), SO2 and NH3, and the combination of these constituents in was modelled in the ‘aer’ experiment.The chemically-reactive gases included methane, nitrous oxide (N2O), and the ozone precursors nitrogen oxides (NOx) and volatile organic compounds (VOC) as well as ozone (O3).For some models we were able to use radiative kernels to find the relative importance of rapid adjustments such as cloud changes, atmospheric temperature and water vapour in the overall value of the ERF. We also used double-calls, where the effect of the aerosol or gas was removed from the radiative transfer calculations in the model, to examine the relative contributions of aerosol-cloud interactions and direct radiative effects.The spread of the results between models is also considered, and the differences attributed to how the models represent different processes, e.g. aerosol-cloud interactions, and the complexity of the atmospheric chemistry modelling. The multi-model means are given below.Table 1 Multi-model means for ERF for aerosolsERF Wm-2 aer BC OC SO2 NH3 Multimodel Mean -1.01 0.15 -0.25 -1.03 -0.07 S.D. 0.25 0.17 0.09 0.37 0.01 Table 2 Multi-model means for ERF for chemically reactive gasesERF Wm-2 CH4 HC N2O NTCF O3 NOx VOC Multi-model mean 0.67 0.12 0.26 -0.86 0.20 0.14 0.09 S.D. 0.17 0.21 0.07 0.18 0.07 0.13 0.14 We find the overall aerosol ERF (aer in Table 1) is consistent with previous work, although the results for black carbon (BC) show adjustments that are generally weaker than in previous studies. We also found that cloud effects can have a large impact on the overall ERF, including for the chemically-reactive gases.The impact of other processes, especially atmospheric chemistry on the overall results is also discussed.

Coastal and estuarine margins are home to an increasing proportion of the global human population and its activities. Within this context, landforms play a critical role in mediating the translation of erosion and flood risk to human receptors in environmental settings that are vulnerable to the likely impacts of climate change. Predicting how coastal and estuarine landforms will evolve in response to changes in sea level and wave climate is thus of considerable importance. This is naturally a modelling problem but previous efforts have often failed to translate generic principles into models that do justice to the place-specific interactions between contemporary processes, antecedent geology, sea level history, historical morphology, engineering interventions and, not least, broader societal concerns. Progress clearly requires better models but, as we argue here, more sophisticated conceptual frameworks are also needed. Accordingly, we outline a new Coastal and Estuarine System Mapping (CESM) approach that captures the configuration of estuarine, coastal and inner shelf landform complexes within a unifying framework that also explicitly resolves the multitude of human interventions that influence shoreline change. An illustrative application to the Suffolk coast of eastern England demonstrates the potential of CESM to encourage a more participatory approach to regional shoreline management and the application of scientific understanding to the challenge of living with human and climate change impacts at the coast.

Data assimilation is predominantly used for state estimation, combining observational data with model predictions to produce an updated model state that most accurately approximates the true system state whilst keeping the model parameters fixed. This updated model state is then used to initiate the next model forecast. Even with perfect initial data, inaccurate model parameters will lead to the growth of prediction errors. To generate reliable forecasts, we need good estimates of both the current system state and the model parameters. This article presents research into data assimilation methods for morphodynamic model state and parameter estimation. First, we focus on state estimation and describe implementation of a three-dimensional variational (3D-Var) data assimilation scheme in a simple 2D morphodynamic model of Morecambe Bay, UK. The assimilation of observations of bathymetry derived from synthetic aperture radar (SAR) satellite imagery and a ship-borne survey is shown to significantly improve the predictive capability of the model over a 2-year run. Here, the model parameters are set by manual calibration; this is laborious and is found to produce different parameter values depending on the type and coverage of the validation dataset. The second part of this article considers the problem of model parameter estimation in more detail. We explain how, by employing the technique of state augmentation, it is possible to use data assimilation to estimate uncertain model parameters concurrently with the model state. This approach removes inefficiencies associated with manual calibration and enables more effective use of observational data. We outline the development of a novel hybrid sequential 3D-Var data assimilation algorithm for joint state-parameter estimation and demonstrate its efficacy using an idealised 1D sediment transport model. The results of this study are extremely positive and suggest that there is great potential for the use of data assimilation-based state-parameter estimation in coastal morphodynamic modelling. Copyright © 2012 Royal Meteorological Society

Coastal areas are already at high risk from a range of geohazards. The cumulative effect of human intervention on soft coastlines has frequently left them far from equilibrium under today’s conditions, especially in densely populated areas. Future changes in marine forcing due to climate change reinforce the need to understand and predict processes of change in shoreline position and configuration at management (decadal) scales. The UK-based iCOASST project is developing new and improved methods to predict decadal geomorphic evolution, linked to coastal erosion and flood risk management. This is based on a framework that links several components to develop a system-level understanding of this change. The framework includes: (1) new methods for system-level analysis and mapping of coast, estuary and inner shelf landform behaviour; (2) well validated ‘bottom-up’ hydrodynamic and sediment transport shelf models which can be applied at shelf scales to investigate inner shelf-coastal interactions; and (3) model compositions formed of existing or new ‘reduced complexity models’ of selected coastal landforms and processes that are suitable for multiple decadal length simulations. This will ultimately allow multiple simulations of coastal evolution which can explore uncertainties in future decadal-scale coastal response, including the effects of climate change and management choices. This paper outlines the current state of progress in the iCOASST Project.

A theoretical model of eruption plume dynamics (Woods, 1988) is used to investigate Plinian eruption columns on Venus. Results for a typical plume, in terms of the temperature, density, velocity, and radius as a function of height are given. The effects of the atmospheric pressure, the volatile content and species, and the eruption temperature on the development of high convecting plumes are discussed, demonstrating the combinations of initial conditions giving rise to either high convective plumes, or low fountains feeding pyroclastic flows. The results show that the development of high convecting plumes on Venus requires an unlikely combination of high volatile contents, high initial temperatures, and high altitude eruptions, leading to the conclusion that explosive eruptions on Venus will generally lead to pyroclastic flows.

International audience; "Water and related chemistry in the Solar System" is a Herschel Space Observatory Guaranteed-Time Key Programme. This project, approved by the European Space Agency, aims at determining the distribution, the evolution and the origin of water in Mars, the outer planets, Titan, Enceladus and the comets. It addresses the broad topic of water and its isotopologues in planetary and cometary atmospheres. The nature of cometary activity and the thermodynamics of cometary comae will be investigated by studying water excitation in a sample of comets. The D/H ratio, the key parameter for constraining the origin and evolution of Solar System species, will be measured for the first time in a Jupiter-family comet. A comparison with existing and new measurements of D/H in Oort-cloud comets will constrain the composition of pre-solar cometary grains and possibly the dynamics of the protosolar nebula. New measurements of D/H in giant planets, similarly constraining the composition of proto-planetary ices, will be obtained. The D/H and other isotopic ratios, diagnostic of Mars' atmosphere evolution, will be accurately measured in H2O and CO. The role of water vapor in Mars' atmospheric chemistry will be studied by monitoring vertical profiles of H2O and HDO and by searching for several other species (and CO and H2O isotopes). A detailed study of the source of water in the upper atmosphere of the Giant Planets and Titan will be performed. By monitoring the water abundance, vertical profile, and input fluxes in the various objects, and when possible with the help of mapping observations, we will discriminate between the possible sources of water in the outer planets (interplanetary dust particles, cometary impacts, and local sources). In addition to these inter-connected objectives, serendipitous searches will enhance our knowledge of the composition of planetary and cometary atmospheres.

The Galileo spacecraft carries a 1500-nm focal length camera with a 800 × 800 CCD detector that will provide images with a spatial resolution of 10 μrad/pixel. The spacecraft will fly by Io at the time of Jupiter Orbit Insertion (JOI) and, subsequently, while in Jupiter's orbit, will have a total of 10 close passes by Europa, Ganymede, and Callisto. These close passes, together with more distant encounters, will be used by the imaging experiment primarily to obtain high-resolution coverage of selected targets, to fill gaps left in the Voyager coverage, to extend global color coverage of each satellite, and to follow changes in the volcanic activity of Io. The roughly 390 Mbit allocated for imaging during the tour will be distributed among several hundred frames compressed by factors that range from 1 to possibly as high as 50. After obtaining high-resolution samples during the initial Io encounter at JOI, roughly 10% of imaging resources are devoted to near-terminator mapping of Io's topography at 2- to 10-km resolution, monitoring color and albedo changes of the Ionian surface, and monitoring plume activity. Observations of Europa range in resolution from several kilometers per pixel to 10 m/pixel. The objectives of Europa are (1) to determine the nature, origin, and age of the tectonic features, (2) to determine the nature, rates, and sequence of resurfacing events, (3) to assess the satellite's cratering history, and (4) to map variations in spectral and photometric properties. Europa was poorly imaged by Voyager, so the plan includes a mix of high- and low-resolution sequences to provide context. The imaging objectives at Ganymede are (1) to characterize any volcanism, (2) to determine the nature and timing of any tectonic activity, (3) to determine the history of formation and degradation of impact craters, and (4) to determine the nature of the surface materials. Because Ganymede was well imaged by Voyager, most of the resources at Ganymede are devoted to high-resolution observations. The Callisto observations will be directed mostly toward (1) filling Voyager gaps, (2) acquiring high-resolution samples of typical cratered terrain and components of the Valhalla and Asgaard basins, (3) acquiring global color, and (4) determining the photometric properties of the surface. A small number of frames will be used to better characterize the small inner satellites of Jupiter, Thebe, Amalthea, Metis, and Adrastea.

We have used automatic extraction of digital elevation models (DEMs) from stereo imagery of Mars to produce DEMs of parts of the Aeolis quadrangle of Mars. The method uses automated stereo matching based on an adaptive least squares correlation technique, which can be applied to Viking Orbiter imagery. A demonstration of the technique is presented, which focuses on the volcano Apollinaris Patera (186°W, 9°S), and the channel Ma'adim Vallis (183°W, 20°S). The topographic information derived is compared with previous determinations of topography, and a brief discussion of the relationship of the topography to the processes that have acted in the area is given. DEMs derived from stereomatching are an invaluable resource for terrain interpretation, and will provide a complementary technique to direct topographic measurements such as future missions to Mars will provide.