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  • 1
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    Representing model uncertainty in the Met Office convection permitting ensemble prediction system and its impact on fog forecasting (2016)
    Wiley
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    Publication Date: 2016-07-15
    Description: Representing model uncertainty in convection-permitting ensemble prediction systems is a developing area of research. While methods for including variability to account for model uncertainty at the global scales are quite mature, it is not clear that these methods will necessarily be applicable at the convective-scale. One such method is the Random Parameter (RP) scheme, where parameters from the physics parametrizations are perturbed at regular intervals throughout the forecast. In this work, we adapt the RP scheme to represent model uncertainty in the Met Office's convection permitting ensemble prediction system for the UK (MOGREPS-UK). The revised version of the RP scheme is applied to a sub-set of model parameters, chosen to target specific physical processes relevant to the UK forecast. Objective verification scores from two one-month trials show particular improvements for visibility and surface temperature when the RP scheme is used. Application of the RP scheme results in a modest increase in the ensemble spread for all surface parameters. The results of low visibility case studies show that applying the RP scheme enables the ensemble to capture observed fog events otherwise missed by the forecast. Overall, the RP scheme has a positive effect on MOGREPS-UK, and demonstrates the benefit of schemes that target known areas of model uncertainty.
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
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  • 2
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    New schemes to perturb sea-surface temperature and soil moisture content in MOGREPS (2013)
    Wiley
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    Publication Date: 2013-06-08
    Description: This paper investigates two schemes that perturb sea-surface temperatures (SSTs) and soil moisture content (SMC) in the Met Office Global and Regional Ensemble Prediction System (MOGREPS), to address a known deficiency of a lack of ensemble spread near the surface. Results from a two-month long trial during the northern hemisphere summer show positive benefits from these schemes. These include a decrease in the spread deficit of surface temperature and improved probabilistic verification scores. SST perturbations exhibit a stronger impact than SMC perturbations, but when combined the increased spread from the two schemes is cumulative. A regional ensemble system driven by the global ensemble members largely reflects the same changes seen in the global ensemble but cycling fields, like SMC, between successive regional forecasts does show some benefit.
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
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  • 3
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    Projected Changes in Interannual Variability of Peak Snowpack Amount and Timing in the Western United States (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract Interannual variability of mountain snowpack has important consequences for ecological and socioeconomic systems, yet changes in variability have not been widely examined under future climates. Physically based snowpack simulations for historical (1970–1999) and high‐emission scenario (RCP 8.5) mid‐21st century (2050–2079) periods were used to assess changes in the variability of annual maximum snow water equivalent (SWEmax) and SWEmax timing across the western United States. Models show robust declines in the interannual variability of SWEmax in regions where precipitation is projected to increasingly fall as rain. The average frequency of consecutive snow drought years (SWEmax 〈 historical 25th percentile) is projected to increase from 6.6% to 42.2% of years. Models also project increases in the variability of SWEmax timing, suggesting reduced reliability of when SWEmax occurs. Differences in physiography and regional climate create distinct spatial patterns of change in snowpack variability that will require adaptive strategies for environmental resource management.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Elevation-dependent responses of streamflow to climate warming (2014)
    Wiley
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    Publication Date: 2014-03-26
    Description: Warming will affect snowline elevation, potentially altering the timing and magnitude of streamflow from mountain landscapes. Presently, the assessment of potential elevation-dependent responses is difficult because many gauged watersheds integrate drainage areas that are both snow- and rain-dominated. To predict the impact of snowline rise on streamflow, we mapped the current snowline (1980 m) for the Salmon River watershed (Idaho, USA) and projected its elevation after 3 °C warming (2440 m). This increase results in a 40% reduction in snow-covered area during winter months. We bolster this analysis by collecting streamflow records from a new, elevation-stratified gauging network of watersheds contained within high (2250 – 3800 m), mid (1500 – 2250 m) and low (300 – 1500 m) elevations that isolate snow, mixed, and rain-dominated precipitation regimes. Results indicate that lags between percentiles of precipitation and streamflow are much shorter in low elevations and that their annual percentiles (Q 25 & Q 75 ) of streamflow occur 30 – 50 days earlier than in mid- and high-elevation watersheds. Extreme events in low elevations are dominated by low- and no-flow events whereas mid- and high-elevations experience large magnitude floods. Only mid- and high-elevation watersheds are strongly cross-correlated with catchment-wide flow of the Salmon River, suggesting that changes in contributions from low-elevation catchments may be poorly represented using mainstem gauges. As snowline rises, mid-elevation watersheds will likely exhibit behaviors currently observed only at lower elevations. Streamflow monitoring networks designed for operational decision making or change detection may require modification to capture elevation-dependent responses of streamflow to warming. This article is protected by copyright. All rights reserved.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 5
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    Comparison of different representations of model error in ensemble forecasts (2019)
    Wiley
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    Publication Date: 2019
    Description: Geographical distribution of T+6 h ensemble spread, using different model error representations and the same initial conditions, for zonal wind component (m s−1) at 500 hPa. (a) represents the CNT run, (b) the difference between SPT and CNT, and (c) the difference between AI and CNT The use of analysis increments to represent model error in the Met Office ensemble prediction system is compared with the use of stochastic parametrizations. Since analysis increments can take into account more possible sources of forecast error than stochastic parametrizations which only represent specific sources of error, the spread of the ensemble and the reliability are markedly improved. There is an increase in the rms error of the ensemble mean for some fields. This may be because analysis increments cannot represent state‐dependent statistics, but may also result from the use of initial condition perturbations from the operational ETKF rather than an ensemble data assimilation with a consistent treatment of model error.
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
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  • 6
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    A Seasonal to Interannual View of Inorganic and Organic Carbon and pH in Western Lake Superior (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract To investigate the carbon cycle of Lake Superior, Earth's largest freshwater lake by surface area, we performed total organic carbon, dissolved organic carbon, chlorophyll, spectrophotometric pH, total inorganic carbon, and alkalinity measurements on seasonal samples from the western lake. The last three parameters, along with in situ temperature, were used to calculate the partial pressure of carbon dioxide in surface water (pCO2(w)) using the CO2SYS algorithm. There was a strong positive correlation between pH and water temperature and a weaker but significant positive correlation between pH and chlorophyll concentration. Total organic carbon exhibited higher nearshore concentrations (as determined by a negative correlation with total water column depth); such a spatial relationship did not appear in the inorganic carbon parameters (total inorganic carbon, pH, or pCO2(w)). Western Lake Superior exhibited net outgassing in spring, little net gas transfer in summer, and some outgassing in the fall. The pCO2(w) values were negatively correlated with both water temperature and chlorophyll concentration. Seasonal differences in pCO2(w) in Lake Superior appeared more strongly driven by biology and terrestrial inputs as compared to direct effects of temperature on CO2 solubility. Interannual data from the long‐term Great Lakes Environmental Database data set indicated that lake alkalinity has been increasing over the past 20 years, and lake surface water pH appeared relatively stable. Modeling pH change over the same time frame in CO2SYS shows that increases in alkalinity and lake surface water temperature counteract the increase in atmospheric carbon dioxide concentration, leading to a relatively constant pH, consistent with observational data.
    Print ISSN: 2169-8953
    Electronic ISSN: 2169-8961
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Regional sensitivities of seasonal snowpack to elevation, aspect, and vegetation cover in western North America (2017)
    Wiley
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    Publication Date: 2017-07-16
    Description: In mountains with seasonal snow-cover, the effects of climate change on snowpack will be constrained by landscape-vegetation interactions with the atmosphere. Airborne lidar surveys used to estimate snow depth, topography, and vegetation were coupled with reanalysis climate products to quantify these interactions and to highlight potential snowpack sensitivities to climate and vegetation change across the western U.S. at Rocky Mountain (RM), Northern Basin and Range (NBR), and Sierra Nevada (SNV) sites. In forest and shrub areas, elevation captured the greatest amount of variability in snow depth (16-79%) but aspect explained more variability (11-40%) in alpine areas. Aspect was most important at RM sites where incoming shortwave to incoming net radiation (SW:NetR ) was highest (∼0.5), capturing 17-37% of snow depth variability in forests and 32-37% in shrub areas. Forest vegetation height exhibited negative relationships with snow depth and explained 3-6% of its variability at sites with greater longwave inputs (NBR and SNV). Variability in the importance of physiography suggest differential sensitivities of snowpack to climate and vegetation change. The high SW:NetR and importance of aspect suggests RM sites may be more responsive to decreases in SW:NetR driven by warming or increases in humidity or cloud-cover. Reduced canopy-cover could increase snow depths at SNV sites, and NBR and SNV sites are currently more sensitive to shifts from snow to rain. The consistent importance of aspect and elevation suggest that changes in SW:NetR and the elevation of the rain/snow transition zone could have widespread and varied effects on western U.S. snowpacks.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    The Met Office convective-scale ensemble, MOGREPS-UK (2017)
    Wiley
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    Publication Date: 2017-08-08
    Description: Since 2012 the Met Office has been running a short-range convective-scale ensemble prediction system over the UK, known as MOGREPS-UK. In this paper we consider MOGREPS-UK in its past, present and future configurations. We describe the evolution of the system during its first few years as an operational model and explain the rationale behind its development. The operational configuration of MOGREPS-UK is evaluated using neighbourhood verification techniques which allow the comparison of ensemble and deterministic forecasts in a probabilistic sense. We compare the performance of MOGREPS-UK to that of the higher resolution UK deterministic convective-scale model, the UKV, and show that over a three-month long trial MOGREPS-UK performs better for all variables considered. Plans of future upgrade options of MOGREPS-UK that take advantage of the increased computing capacity at the Met Office are discussed. Three different options were compared: increasing the domain size (now implemented), decreasing the horizontal grid-spacing, and increasing the number of ensemble members. Objective verification results from month-long winter and summer trials show that all options have their benefits, with the most improvement seen with the increase in ensemble size, particularly for precipitation.
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
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  • 9
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    A new flow cytometry method enabling rapid purification of fossil pollen from terrestrial sediments for AMS radiocarbon dating (2013)
    Wiley
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    Publication Date: 2013-03-03
    Description: Radiocarbon ( 14 C) accelerator mass spectrometry (AMS) dating has played a significant role towards improving our understanding of the timing of events and rates of change in archaeological and environmental records over the last 50 000 years. Although it is not always possible to find suitable macrofossils for 14 C dating, microfossils, notably plant pollen, are a viable alternative. Obtaining preserved pollen samples of known provenance and of sufficient quantity for dating by 14 C AMS is, however, challenging because of time-consuming methods of extraction and purification and possible contamination from other organic material. Here we report a new, rapid and straightforward method using flow cytometry (FCM) to distinguish, sort and collect sufficient quantities of fossil pollen with minimal contamination from lake sediments for radiocarbon dating. Using this approach, we demonstrate 14 C AMS ages that date back to at least 40 ka BP. While future work may be required to refine purification methodologies for different sample types and to precisely quantify the dating limit of this approach, FCM dating of microfossils shows considerable promise in generating robust geochronological frameworks for sequences that have previously proved problematic. Copyright © 2013 John Wiley & Sons, Ltd.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
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  • 10
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    Salmonella enterica serovar Typhi live vector vaccines finally come of age (2009)
    Wiley
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    Publication Date: 2009-05-05
    Print ISSN: 0818-9641
    Electronic ISSN: 1440-1711
    Topics: Biology , Medicine
    Published by Wiley
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