Graham Weedon
The Met Office, Foundation Science, Department Member
Detailed studies have been conducted into the the nature of the systematic diurnal errors in near-surface temperatures and winds in MetUM forecasts over the UK. These studies have included off-line JULES simulations, case studies with the... more
Detailed studies have been conducted into the the nature of the systematic diurnal errors in near-surface temperatures and winds in MetUM forecasts over the UK. These studies have included off-line JULES simulations, case studies with the UKV and month-long DA-trials, and detailed comparison has been made with both the operational network of surface sites and the Met Office Observational Research site at Cardington. While the issues involve complex interactions between the land surface representation, the boundary layer turbulence scheme and their interaction with the resolved scale flow, some proposed changes to the model configuration will be taken forward into testing for possible inclusion in RA1 (for example, improvements to parameters representing the properties of vegetation and stable boundary layer turbulence). Key recommendations for further work are: • more realistic UKV surface characteristics (tile fractions, canopy height, albedo and LAI) are urgently required with sug...
Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity,... more
Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.
Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity,... more
Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.
Magnetic susceptibility from the Blue Lias Formation from five sites in southern Britain, UK, supplement to: Weedon, Graham P; Page, Kevin N; Jenkyns, Hugh C (2019): Cyclostratigraphy, stratigraphic gaps and the duration of the Hettangian Stage (Jurassic): insights from the Blue Lias Formation of...more
Measurements of volume magnetic susceptibility (vol MS) measured in the field at five sections of the Blue Lias Formation in southern Britain, UK. The sites are Pinhay Bay to West Cliff, Lyme Regis (Dorset); St Audries Bay (Somerset);... more
Measurements of volume magnetic susceptibility (vol MS) measured in the field at five sections of the Blue Lias Formation in southern Britain, UK. The sites are Pinhay Bay to West Cliff, Lyme Regis (Dorset); St Audries Bay (Somerset); Quantocks Head (Somerset); St Marys Well Bay at Lavernock (Glamorgan); Southam Quarry, near Long Itchington (Warwickshire). Each data set includes: stratigraphic height; astronomically tuned time scale; composite time scale; vol MS (SI units); short eccentricity filter output; lithology of measurement; previously published bed number; ammonite biohorizon, ammonite subzone; ammonite zone. In the case of limestone nodules within light marl measurements are made through the limestone nodules if they constitute 50% or more of the section along the bedding planes. For horizons with widely spaced limestone nodules (< 50% along bedding) light marl is measured instead. Volume MS measurement procedures are described by Weedon, Jenkyns and Page (2018). Astron...
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Lithostratigraphic and magnetic-susceptibility logs for four sections in the Blue Lias Formation are combined with a re-assessment of the ammonite biostratigraphy. A Shaw plot correlating the West Somerset coast with the Devon/Dorset... more
Lithostratigraphic and magnetic-susceptibility logs for four sections in the Blue Lias Formation are combined with a re-assessment of the ammonite biostratigraphy. A Shaw plot correlating the West Somerset coast with the Devon/Dorset coast at Lyme Regis, based on 63 common biohorizon picks, together with field evidence, demonstrate that intra-formational hiatuses are common. Compared to laminated shale deposition, the climate associated with light marl is interpreted as both drier and stormier. Storm-related non-deposition favoured initiation of limestone formation near the sediment–water interface. Areas and time intervals with reduced water depths had lower net accumulation rates and developed a greater proportion of limestone. Many homogeneous limestone beds have no ammonites preserved, whereas others contain abundant fossils. Non-deposition encouraged shallow sub-sea-floor cementation which, if occurring after aragonite dissolution, generated limestones lacking ammonites. Abunda...
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The understanding of land surface hydrology is critical for planning human activities involving freshwater resources. We assess how atmospheric forcing data uncertainties affect land surface model (LSM) simulations by means of an... more
The understanding of land surface hydrology is critical for planning human activities involving freshwater resources. We assess how atmospheric forcing data uncertainties affect land surface model (LSM) simulations by means of an extensive evaluation exercise using a number of state-of-the-art remote sensing and station-based datasets. For this purpose, we use the CO2-responsive ISBA-A-gs LSM coupled the CNRM version of the Total Runoff Integrated Pathways (CTRIP) river routing model. We perform multi-forcing simulations over the Euro-Mediterranean area (25°–75.5° N, 11.5° W–62.5° E, at 0.5° resolution) from 1979 to 2012. The model is forced using four atmospheric datasets. Three of them are based on the ERA-Interim reanalysis (ERA-I). The fourth dataset is independent from ERA-Interim: PGF, developed at Princeton University. The hydrological impacts of atmospheric forcing uncertainties are assessed by comparing simulated surface ...
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Research Interests: Earth Sciences, Environmental Science, Computer Science, Climate Change, Climatology, and 15 moreHigh Pressure, Phenology, Forest fire, Biosphere, Land Cover, IEEE, Ecology and Environment, Oscillations, Precipitation, Regression Model, El Nino, Fire regime, Growing Season, Arctic Oscillation, and remote sensing data
Six land surface models and five global hydrological models participate in a model intercomparison project [Water Model Intercomparison Project (WaterMIP)], which for the first time compares simulation results of these different classes... more
Six land surface models and five global hydrological models participate in a model intercomparison project [Water Model Intercomparison Project (WaterMIP)], which for the first time compares simulation results of these different classes of models in a consistent way. In this paper, the simulation setup is described and aspects of the multimodel global terrestrial water balance are presented. All models were run at 0.5° spatial resolution for the global land areas for a 15-yr period (1985–99) using a newly developed global meteorological dataset. Simulated global terrestrial evapotranspiration, excluding Greenland and Antarctica, ranges from 415 to 586 mm yr−1 (from 60 000 to 85 000 km3 yr−1), and simulated runoff ranges from 290 to 457 mm yr−1 (from 42 000 to 66 000 km3 yr−1). Both the mean and median runoff fractions for the land surface models are lower than those of the global hydrological models, although the range is wider. Significant simulation differences between land surfac...
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An 18-yr time series of the fraction of absorbed photosynthetically active radiation (fAPAR) taken in by the green parts of vegetation data from the NOAA Advanced Very High Resolution Radiometer (AVHRR) instrument series was analyzed for... more
An 18-yr time series of the fraction of absorbed photosynthetically active radiation (fAPAR) taken in by the green parts of vegetation data from the NOAA Advanced Very High Resolution Radiometer (AVHRR) instrument series was analyzed for interannual variations in the start, peak, end, and length of the season of vegetation photosynthetic activity in central and east Siberia. Variations in these indicators of seasonality can give important information on interactions between the biosphere and atmosphere. A second-order local moving window regression model called the “camelback method” was developed to determine the dates of phenological events at subcontinental scale. The algorithm was validated by comparing the estimated dates to phenological field observations. Using spatial correlations with temperature and precipitation data and climatic oscillation indices, two geographically distinct mechanisms in the system of climatic controls of the biosphere in Siberia are postulated: centr...
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Research Interests: Earth Sciences, Geology, Oceanography, Climatology, Stable Isotopes, and 15 moreAbrupt Climate Change, Holocene, North Atlantic, Stable Isotope, Chironomids, Lake Sediments, Surface Water, Ice Cores, Oxygen Isotopes, Oxygen Isotope, Early Holocene, Air Temperature, Thermal Ionization Mass Spectrometry, Ice Sheets, and Lacustrine Carbonates
The rate of above-ground woody biomass production, W(P), in some western Amazon forests exceeds those in the east by a factor of 2 or more. Underlying causes may include climate, soil nutrient limitations and species composition. In this... more
The rate of above-ground woody biomass production, W(P), in some western Amazon forests exceeds those in the east by a factor of 2 or more. Underlying causes may include climate, soil nutrient limitations and species composition. In this modelling paper, we explore the implications of allowing key nutrients such as N and P to constrain the photosynthesis of Amazon forests, and also we examine the relationship between modelled rates of photosynthesis and the observed gradients in W(P). We use a model with current understanding of the underpinning biochemical processes as affected by nutrient availability to assess: (i) the degree to which observed spatial variations in foliar [N] and [P] across Amazonia affect stand-level photosynthesis; and (ii) how these variations in forest photosynthetic carbon acquisition relate to the observed geographical patterns of stem growth across the Amazon Basin. We find nutrient availability to exert a strong effect on photosynthetic carbon gain across...
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Warnaars, Tanya; Harding, Richard; Blyth, Eleanor; Weedon, Graham; Ludwig, Fulco; Wiberg, David; Hagemann, Stefan; Tallaksen, Lena; van Lanen, Henny; Kabat, Pavel. 2011 WATCH Final year activity report. WATCH IP.(WATCH Project No.... more
Warnaars, Tanya; Harding, Richard; Blyth, Eleanor; Weedon, Graham; Ludwig, Fulco; Wiberg, David; Hagemann, Stefan; Tallaksen, Lena; van Lanen, Henny; Kabat, Pavel. 2011 WATCH Final year activity report. WATCH IP.(WATCH Project No. 036946)(Unpublished)
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Page 1. Astronomical calibration of the Jurassic time-scale from cyclostratigraphy in British mudrock formations By Graham P. Weedon1, Hugh C. Jenkyns2, Angela L. Coe3 and Stephen P. Hesselbo2 1Department of Environment ...
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Today the deep western boundary current (DWBC), east of New Zealand is the most important route for deep water entering the Pacific Ocean. Large-scale changes in deep water circulation patterns are expected to have been associated with... more
Today the deep western boundary current (DWBC), east of New Zealand is the most important route for deep water entering the Pacific Ocean. Large-scale changes in deep water circulation patterns are expected to have been associated with the development of the East Antarctic Ice Sheet (EAIS) - Close to the main source of bottom water for the DWBC. Here we present sortable silt mean grain size data from ODP Site 1123 spanning the middle Miocene from ~15.5-12.5 Ma, a period of significant global ice accumulation associated with EAIS growth. These data reveal variability in speed of the Pacific inflow on the timescale of the 41 ka orbital obliquity cycle. As similar orbital-scale flow changes have recently been demonstrated for the Pleistocene epoch, collectively these variations suggest that a strong coupling between changes in the speed of the deep Pacific inflow and high-latitude climate forcing may have been a persistent feature of the global thermohaline circulation system for at least the past 15 Ma. Furthermore, long-term changes in flow speed suggest an intensification of the DWBC under an inferred increase in Southern Component Water production. This occurred at the same time as and may be causally linked to decreasing Tethyan outflow and major EAIS growth between 15.6-13.6 Ma. These results provide evidence that a major component of the deep thermohaline circulation was associated with the middle Miocene growth of the EAIS and support the view that this period was an important step in the development of the Neogene icehouse climate.
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... Jupp, TE; Weedon, GP; Los, SO; Taylor, CM. 2007 Feedbacks between vegetation and precipitation inferred from remote sensing. [Poster] In: EGU Conference, Vienna. Vienna, EGU, 06809. Full text not available from this repository. ...
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Increasingly, environmental scientists, palaeoceanographers and geologists are collecting quantitative records of environmental changes (time series) from sediments, ice cores, cave calcite, corals and trees. This book explains how to... more
Increasingly, environmental scientists, palaeoceanographers and geologists are collecting quantitative records of environmental changes (time series) from sediments, ice cores, cave calcite, corals and trees. This book explains how to analyze these records, using straightforward explanations and diagrams rather than formal mathematical derivations. All the main cyclostratigraphic methods are covered, including spectral analysis, cross-spectral analysis, filtering, complex demodulation, and wavelet and singular spectrum analysis. Practical problems of time-series analysis are considered in detail. Recent research into various types of tidal and climatic cycles is summarized.
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Abstract. Uncertainty in the terrestrial water cycle, as represented by land surface model outputs, is investigated as a function of uncertainty in the WATCH Forcing Data. Three alternative forcing datasets were created involving changes... more
Abstract. Uncertainty in the terrestrial water cycle, as represented by land surface model outputs, is investigated as a function of uncertainty in the WATCH Forcing Data. Three alternative forcing datasets were created involving changes to: a) rainfall and snowfall, b) ...
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... However, all other indicators of intense shock deformation described for the Toba ignimbrite, including shock ... in feldspar, were observed at all localities, some as distant from the caldera as 2000 km ... As to the second concern,... more
... However, all other indicators of intense shock deformation described for the Toba ignimbrite, including shock ... in feldspar, were observed at all localities, some as distant from the caldera as 2000 km ... As to the second concern, because of the exceedingly complex struc-ture of the ...
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