Temporal and Geographical Variation in Martian Surface Dust Lifting Processes

Numerical experiments were completed examining the variability of key aspects of the Martian dust cycle and investigating their importance in predicting conditions for spacecraft atmospheric descent and landing. The dust cycle – lifting, transportation and deposition – is a significant Martian climate cycle. The geographical and temporal variation in dust lifting processes were investigated using a Martian Global Circulation Model. The geographical representation of Martian dust lifting by wind stress was used to explore the experimental impact of changes in model resolution. It was found that increasing the resolution improved the model's geographical representation of observed dust lifting regions, such as resolving important storm-forming regions in the northern hemisphere. This improvement was unanticipated in the case of changes in vertical resolution, and the horizontal resolution work identified an important length scale for dust lifting (of the order of 100 kilometres). The temporal variation of a dust lifting process was investigated through experiments focusing on the diurnal variability of Martian dust devils (small-scale convective vortices). This research compared results with published lander and rover observations and found that dust devils were more active during morning hours than anticipated, suggesting that the generally accepted description of dust devil behaviour on Mars is incomplete. Predictions were made of the atmospheric and near-surface environment encountered by the ESA ExoMars Schiaparelli landing module. The experiments produced a reasonable representation of atmospheric quantities along the descent trajectory and were able to generate similar low-altitude wind fields to those reported by the spacecraft. The global-scale model also out-performed a higher resolution mesoscale model. These findings are significant in the field of Martian climate modelling, are important for the planning of Martian dust devil observation campaigns and future missions to the planet`s surface, and will also be relevant to researchers operating atmospheric models for other planetary bodies

Wind-Stress Dust Lifting in a Mars Global Circulation Model: Representation across Resolutions

The formation of Martian dust storms is believed to be driven by dust lifting by near-surface wind stress (NSWS). Accurately representing this dust lifting within Mars Global Circulation Models (MGCMs) is important in order to gain a full understanding of the Martian dust storm cycle. Parameterisations of dust lifting by NSWS exist within several MGCMs; implementations differ but they all follow a similar design, so progress within one model is relevant to the entire field. Few studies have explored in detail how the results of these parameterisations can be affected by changing the horizontal resolution of the model. An accurate parameterisation of dust lifting by NSWS will lift a representative dust mass, reproducing characteristic dust optical depths in the atmosphere. The geographical distribution of the dust lifting by NSWS will also change throughout the year, affecting patterns of dust storm formation and development. Currently, suitable values for dust lifting parameters must be identified at every new model resolution. Resolutions of ~5° latitude x ~5° longitude are often used to model the Martian climate, as thermal tides and long-term weather patterns can be well represented at this resolution. However, smaller scale phenomena (such as near-surface winds driven by local topography) cannot be accurately depicted at this resolution. We use the LMD-UK MGCM to complete multi-year simulations across multiple model resolutions. Our experiments range from ‘low’ resolution ~5° lat x ~5° lon to ‘high’ resolution ~1° lat x ~1° lon. In experiments with fixed, constant lifting parameters, we find that higher resolution simulations lift more dust, but that this trend is asymptotic. At low resolutions, dust lifting increases proportionately with the increase in number of horizontal gridboxes. However, at high resolutions, doubling the number of gridboxes results only in a 30% increase in the total dust mass lifted. Geographical and temporal distributions of dust lifting are investigated, as well as the total dust lifted, in order to assess the optimum parameters for each resolution, and to develop a calibration scheme for this dust lifting across model resolutions. The scheme is verified through comparison with spacecraft observations of dust optical depths and dust storm locations

How Do Martian Dust Devils Vary Throughout the Sol?

Dust devils are vortices of air made visible by entrained dust particles. Dust devils have been observed on Earth and captured in many Mars lander and orbiter images. Martian dust devils may be important to the global climate and are parameterised within Mars Global Circulation Models (MGCMs). We show that the dust devil parameterisation in use within most MGCMs results in an unexpectedly high level of dust devil activity during morning hours. In contrast to expectations, based on the observed behaviour of terrestrial dust devils and the diurnal maximum thermal contrast at the surface, we find that large areas of the modelled Martian surface experience dust devil activity during the morning as well as in the afternoon, and that many locations experience a peak in dust devil activity before mid-sol. Using the UK MGCM, we study the amount of surface dust lifted by dust devils throughout the diurnal cycle as a proxy for the level of dust devil activity occurring. We compare the diurnal variation in dust devil activity with the diurnal variation of the variables included in the dust devil parameterisation. We find that the diurnal variation in dust devil activity is strongly modulated by near-surface wind speeds. Within the range of daylight hours, higher wind speeds tend to produce more dust devil activity, rather than the activity simply being governed by the availability of heat at the planet's surface, which peaks in early afternoon. We compare our results with observations of Martian dust devil timings and obtain a good match with the majority of surface-based surveys. We do not find such a good match with orbital observations, but these data tend to be biased in their temporal coverage. We propose that the generally accepted description of dust devil behaviour on Mars is incomplete, and that theories of dust devil formation may need to be modified specifically for the Martian environment. Further dust devil observations are required to support any such modifications

Comparison of Global-Scale and Mesoscale Modelling of Vertical Profiles in the Martian Atmosphere: How Does Model Resolution Impact Predictions of Conditions at Mission Landing Sites?

Detailed modelling of the Martian atmosphere is completed for every spacecraft designed to land on the planet’s surface. This provides the most complete picture of the environment that the descending module will be entering and travelling through, and facilitates planning of the Entry, Descent and Landing (EDL) phase of the mission. The selected resolution of an atmospheric model can impact the results of the experiments performed. The complexities of atmospheric modelling also require models of different scales to best represent the behaviour of different scale atmospheric phenomena. Comparisons between multiple model results and in situ data are crucial for improving future environmental predictions for missions landing on Mars. This work describes how changes in model scale and resolution (horizontal and vertical) can impact experimental results, using as a case study the selected landing site of the European Space Agency (ESA) Schiaparelli module. Schiaparelli was part of ESA’s ExoMars 2016 mission; the module descended through the Martian atmosphere on 19th October 2016. Experiments were completed that encompassed the period of Schiaparelli’s descent, using both a global-scale and a mesoscale model. The global model used in this work is the UK version of the LMD (Laboratoire de Météorologie Dynamique) Mars Glob-al Circulation Model (“the MGCM”), a 3D multi-level spectral model of the Martian atmosphere up to an altitude of ~100 km [1]. The mesoscale model used in this work is the LMD Martian Mesoscale Model (MMM) [2]; in these experiments an altitude of ~50 km was modelled in the mesoscale. Multiple resolution experiments were completed using the MGCM; results range from a ‘low’ resolution ~5° latitude x ~5° longitude (a resolution typically used for Martian climate modelling) to a ‘high’ resolution ~1° lat x ~1° lon. The vertical dimension is modelled using a set number of vertical layers; in these experiments the number of vertical layers selected was between 23 and 100. Experiments were run for a simulated year, starting from initial conditions based upon prior atmospheric observations, thus providing an independent prediction of conditions through the period of this case study. The MMM experiments were com-pleted in a set of nested resolutions, ranging from the outer, lowest resolution results at 63 km x 63 km, to the inner, highest resolution results at 7 km x 7 km. MMM experiments were completed using 60 vertical layers. Previous comparisons of global-scale and meso-scale modelling have focused on areas containing small-scale topographical variation that is not present in the global scale models. This work considers the relatively flat topography of the Schiaparelli site – a location that is more representative of the majority of historical Martian landing sites than areas that contain severe, small-scale topographical variation. Initial analysis has focused on constructing vertical profiles from the model output at both experimental scales, following preliminary information on the descent trajectory of the Schiaparelli module. An example comparison of atmospheric profiles constructed from MGCM results at different model resolutions. The plot displays atmospheric temperature obtained from experiments completed at different vertical resolutions: 23 and 100 vertical levels. There is a good match between the results, with a root mean square deviation (RMSD) of 9.83 K be-tween the results for the full height of the profiles; the RMSD reduces to 2.05 K when considering only the lowest ~10 km of the profiles (approximately one scale height). A comparison of vertical atmospheric temperature profiles from MGCM and MMM results. While the trend in the results is similar, the results differ by ~10 K between the models through most of the profile, down to a height of ~3 km above the surface. Between 50 and 3 km above the surface the RMSD of the profiles is 9.79 K; below 3 km (down to the lowest MGCM model lay-er) the match is closer, with an RMSD of 2.59 K. Further comparisons have been completed between the MGCM and MMM results, such as wind speed and direction, including consideration of the wider topographical and atmospheric context of Schiaparelli’s landing site and EDL period. These results show that, for the region considered within this case study, changing the horizontal or verti-cal resolution used in MGCM experiments does not greatly impact the results obtained. Similarly, the MMM results do not vary more than ~4 K with chang-ing horizontal resolution. In both cases, lower resolu-tions results (which are quicker and less computationally expensive to complete) are a good approximation of higher resolution results. Additionally, the similarity of the trends seen in the results from the different scale models suggests that global-scale model results are a reasonable approximation for mesoscale model results, for a number of potential landing locations on Mars. The module successfully transmitted some data that was captured during its descent, primarily from engineering sensors; this data includes the module's trajectory and attitude during the mission’s EDL phase. The ExoMars AMELIA (Atmospheric Mars Entry and Landing Investigations and Analysis) team aim to use the data returned by Schiaparelli during descent, combined with dynamic modelling of the module's motion, to reconstruct atmospheric profiles of density, pressure, temperature and wind speed [3]. Upon the release of the Schiaparelli data, the results from both the MGCM and MMM experiments will be compared with the data, supporting the work of the AMELIA team. References: [1] Forget et al. (1999) JGR, 104, E10. [2] Spiga et al. (2009) JGR, 114, E2. [3] Ferri et al. (2012) 9th International Planetary Probe Workshop

Evaluating soil moisture simulations from a national-scale gridded hydrological model over Great Britain

•Study Region: The study covers sites across Great Britain. •Study Focus: Soil moisture information is important for a range of applications including flood and drought monitoring, seasonal hydrological forecasting, and agricultural management. However, spatially distributed soil moisture estimates for sub-surface soils are scarce despite their importance. The Grid-to-Grid hydrological model (G2G) was primarily developed to simulate river flows at a national scale, but can also output simulated depth-integrated soil moisture on a 1 km grid. Here, we evaluate G2G soil moisture simulations against in situ neutron probe (NP) observations at 85 sites across Great Britain, to evaluate whether modelled soil moisture outputs have value and to identify areas for improvement. •New Hydrological Insights for the Region: Despite large uncertainties in observed soil moisture within a site, there was a good temporal correlation between observed and modelled soil moisture, with Pearson correlation values exceeding 0.7 for 77% of sites. However, the model tended to under-predict soil moisture values (median bias of −12 cm/m) and over-predict variation (median standard deviation error of 2 cm/m). Model agreement with observations was generally better for areas with deep or mid-depth mineral soils and worst in areas of peat. Based on this evaluation against NP observations, we demonstrate that G2G soil moisture is a useful resource for estimating relative wetness of the soil, but not necessarily the soil moisture content values themselves

Hydro-PE: gridded datasets of historical and future Penman-Monteith potential evaporation for the United Kingdom

We present two new potential evaporation datasets for the United Kingdom: a historical dataset, Hydro-PE HadUKGrid, which is derived from the HadUK-Grid gridded observed meteorology (1969&ndash;2021); and a future dataset, Hydro-PE UKCP18 RCM, which is derived from UKCP18 regional climate projections (1980&ndash;2080). Both datasets are suitable for hydrological modelling, and provide Penman-Monteith potential evapotranspiration parameterised for short grass, with and without a correction for interception on days with rainfall. The potential evapotranspiration calculations have been formulated to closely follow the methodology of the existing Meteorological Office Rainfall and Evaporation Calculation System (MORECS) potential evapotranspiration, which has historically been widely used by hydrological modellers in the United Kingdom. The two datasets have been created using the same methodology, to allow seamless modelling from past to future. Hydro-PE HadUK-Grid shows good agreement with MORECS in much of the United Kingdom, although Hydro-PE HadUK Grid is higher in the mountainous regions of Scotland and Wales. This is due to differences in the underlying meteorology, in particular the wind speed, which are themselves due to the different spatial scales of the data. Hydro-PE HadUK-Grid can be downloaded from https://doi.org/10.5285/9275ab7e-6e93-42bc-8e72-59c98d409deb (Brown et al., 2022) and Hydro-PE UKCP18 RCM can be downloaded from https://doi.org/10.5285/eb5d9dc4-13bb-44c7-9bf8-c5980fcf52a4 (Robinson et al., 2021).</p

A North Atlantic tephrostratigraphical framework for 130-60 ka b2k:new tephra discoveries, marine-based correlations, and future challenges

Building chronological frameworks for proxy sequences spanning 130–60 ka b2k is plagued by difficulties and uncertainties. Recent developments in the North Atlantic region, however, affirm the potential offered by tephrochronology and specifically the search for cryptotephra. Here we review the potential offered by tephrostratigraphy for sequences spanning 130–60 ka b2k. We combine newly identified cryptotephra deposits from the NGRIP ice-core and a marine core from the Iceland Basin with previously published data from the ice and marine realms to construct the first tephrostratigraphical framework for this time-interval. Forty-three tephra or cryptotephra deposits are incorporated into this framework; twenty three tephra deposits are found in the Greenland ice-cores, including nine new NGRIP tephras, and twenty separate deposits are preserved in various North Atlantic marine sequences. Major, minor and trace element results are presented for the new NGRIP horizons together with age estimates based on their position within the ice-core record. Basaltic tephras of Icelandic origin dominate the framework with only eight tephras of rhyolitic composition found. New results from marine core MD99-2253 also illustrate some of the complexities and challenges of assessing the depositional integrity of marine cryptotephra deposits. Tephra-based correlations in the marine environment provide independent tie-points for this time-interval and highlight the potential of widening the application of tephrochronology. Further investigations, however, are required, that combine robust geochemical fingerprinting and a rigorous assessment of tephra depositional processes, in order to trace coeval events between the two depositional realms

Flood impacts across scales: towards an integrated multi-scale approach for Malaysia

Flooding is a recurring challenge across Malaysia, causing loss of life, extensive disruption and having a major impact on the economy. A new collaboration between Malaysia and UK, supported by the Newton-Ungku Omar Fund, aims to address a critical and neglected aspect of large-scale flood risk assessment: the representation of damage models, including exposure, vulnerability and inundation. In this paper we review flood risk and impact across Malaysia and present an approach to integrate multiple sources of information on the drivers of flood risk (hazard, exposure and vulnerability) at a range of scales (from household to national), with reference to past flood events. Recent infrastructure projects in Malaysia, such as Kuala Lumpur’s SMART Tunnel, aim to mitigate the effects of flooding both in the present and, ideally, for the foreseeable future. Our collaborative project aims to develop and assess a new multi-scale model of flood risk in Malaysia for current and projected future scenarios, and to address climate adaptation questions of policy relevance for flood stakeholders. This approach will enable us to identify the preferred adaptation pathways given multiple scenarios of climate and socio-economic change in Malaysia, and, beyond the life of our project, internationall

2019 ESC/EAS guidelines for the management of dyslipidaemias : Lipid modification to reduce cardiovascular risk

Correction: Volume: 292 Pages: 160-162 DOI: 10.1016/j.atherosclerosis.2019.11.020 Published: JAN 2020Peer reviewe

Common variants at ABCA7, MS4A6A/MS4A4E, EPHA1, CD33 and CD2AP are associated with Alzheimer's disease

We sought to identify new susceptibility loci for Alzheimer's disease through a staged association study (GERAD+) and by testing suggestive loci reported by the Alzheimer's Disease Genetic Consortium (ADGC) in a companion paper. We undertook a combined analysis of four genome-wide association datasets (stage 1) and identified ten newly associated variants with P ≤ 1 × 10−5. We tested these variants for association in an independent sample (stage 2). Three SNPs at two loci replicated and showed evidence for association in a further sample (stage 3). Meta-analyses of all data provided compelling evidence that ABCA7 (rs3764650, meta P = 4.5 × 10−17; including ADGC data, meta P = 5.0 × 10−21) and the MS4A gene cluster (rs610932, meta P = 1.8 × 10−14; including ADGC data, meta P = 1.2 × 10−16) are new Alzheimer's disease susceptibility loci. We also found independent evidence for association for three loci reported by the ADGC, which, when combined, showed genome-wide significance: CD2AP (GERAD+, P = 8.0 × 10−4; including ADGC data, meta P = 8.6 × 10−9), CD33 (GERAD+, P = 2.2 × 10−4; including ADGC data, meta P = 1.6 × 10−9) and EPHA1 (GERAD+, P = 3.4 × 10−4; including ADGC data, meta P = 6.0 × 10−10)