1,720,975 research outputs found
Model-data fusion based analysis of global terrestrial permafrost domain
No full textThe CARDAMOM model-data fusion (MDF) software was used to generate an analysis (0.5x0.5 degree, 2001-2019, monthly time step) of the carbon (C) and water (H2O) cycles across the global terrestrial permafrost regions. CARDAMOM used time series information on leaf area index, total woody biomass, net biome exchange of CO2 and a prior in the initial value of soil C stocks, to train an intermediate complexity model of the terrestrial ecosystem (DALEC4). CARDAMOM retrieves ensembles of parameters are estimates for DALEC4 uniquely for each pixel within the analysis domain, from these ensembles the uncertainty associated with analysis can be directly quantified. Permafrost domain defined under the RECCAP2 definition (https://www.globalcarbonproject.org/reccap/, accessed 22/08/2023).
The analysis output includes uncertainty bounded estimates of ecosystem gross fluxes (e.g. photosynthesis, plant respiration, decomposition and fire), C stocks (labile, foliage, wood, fine roots, litter and soil) and their internal dynamics (e.g. allocation fractions of photosynthate and tissue mortality).
The dataset relates to the upcoming publication Smallman, T.L., Williams, M. (in submission). 'Two decades of permafrost region CO2, CH4, and N2O budgets suggest a small net greenhouse gas source to the atmosphere. Permafrost region budgets of greenhouse gases and lateral fluxes of carbon and nitrogen for the years 2000-2020 based on bottom-up and top-down approaches'.Metadata for the variables provided are given in the netcdf files. This includes the complete geographic extent and temporal coverage and variable definitions
ACM-GPP-ETv1
No full textSource code and example for the aggregated canopy model for gross primary productivity and evapotranspiration version 1 (ACM-GPP-ET v1). ACM-GPP-ETv1 is a model of intermediate complexity representing coupled daily plant carbon (photosynthesis or GPP) and water cycles (transpiration, soil evaporation and evaporation of canopy intercepted rainfall). ACM-GPP-ET represents the whole plant hydraulic pathway balancing available water supply and evaporative demand through ecophysiological principles.Software is composed of an input / output code (written in R) and an analysis code base of the simulation mode (written in Fortran). The software package include a example file "ACM_GPP_ET_single_site_test.r", an ./input directory and ./src. The example file deals with input and output of the analysis. The ./input directory contains input drivers for a single site example. The ./src directory contains two Fortran files. ./src/ACM_GPP_ET.f90 contains the main source code of the ACM-GPP-ET model while ./src/ACM_GPP_ET_R_interface.f90 handles in needed interface between the R component of the analysis system and the main Fortran model
Model-data fusion based analysis of climate response of semi-dry tropical forests in the Yucatan, Mexico
No full textTropical forests hold large stocks of carbon in biomass and face pressures from changing climate and anthropogenic disturbance. Understanding the impact of these pressures on biomass is vital for effective forest management and conservation over the next century. Forests' capacity to store biomass under future conditions and accumulate biomass during regrowth after clearance are major knowledge gaps. Here we use chronosequence data, satellite observations and a C-cycle process model to diagnose woody C dynamics in two major dry forest ecotypes (semi-deciduous and semi-evergreen) in Yucatán, Mexico. Woody biomass differences between mature semi-deciduous (90 MgC/ha) and semi-evergreen (175 MgC/ha) forest landscapes are mostly explained by differences in climate (c. 60%), particularly temperature, humidity and soil moisture effects on production. Functional variation in foliar phenology, woody allocation, and wood turnover rate explained c. 40% of biomass differences between ecotypes. Modelling experiments explored varied forest clearance and regrowth cycles, under a range of climate and CO2 change scenarios up to 2100. Climate scenario projections indicate that production and steady state biomass in both ecotypes were reduced by forecast warming and drying (mean biomass 2021-2100 reduced 16-19% compared to 2001-2020), but compensated by fertilisation from rising CO2. Functional analysis indicates that trait adjustments could amplify biomass losses by c. 70%. Experiments with disturbance and recovery across historically reported levels for the Yucatán indicate reductions to mean forest biomass stocks over 2021-2100 similar in magnitude to climate change impacts (10-19% reductions for disturbance with recovery). Forest disturbance without regrowth amplifies biomass loss by three- or four-fold. Our results identify the potential for functional adjustments, hypothesised to limit climate risks, to magnify biomass reductions over the coming century. However, the range of impacts of land use and land use change are as, or more, substantive than the totality of direct and indirect climate impacts. The dataset is related to the upcoming publication "Isolating the effects of regrowth and functional adjustments on climate and land use impacts on Yucatán's forest biomass in the twenty-first century" (in review).All dataset description are provided within the associated readme.tx
CARDAMOM Kenyan C-cycle analysis (0.25 degree, monthly, 2014-2017): Forest and savannah specific
No full textThis dataset contains two netCDF file reporting terrestrial C-cycle analysis of Kenya at 0.25 x 0.25 degree spatial and monthly temporal resolutions for 2014 to 2017. One analysis specifically focused on forested land of Kenya, the other analysis focused on savannah land. The analysis uses the CARDAMOM model-data fusion framework to retrieve information on Kenya's terrestrial C-cycle uncertainty uniquely for each location based on location and time specific observations and their uncertainties. The files contains pixel-level estimates of C storage (plant tissues and dead organic matter), C fluxes (photosynthesis, respiration, fire emissions), allocation of C to plant tissues and their residence times. All variables include uncertainty information reporting the 2.5 %, 25 %, 50 %, 75 % and 97.5% quantiles.This dataset contains two netCDF file reporting terrestrial C-cycle analysis of Kenya at 0.25 x 0.25 degree spatial and monthly temporal resolutions for 2014 to 2017. One analysis specifically focused on forested land of Kenya, the other analysis focused on savannah land. The analysis uses the CARDAMOM model-data fusion framework to retrieve information on Kenya's terrestrial C-cycle uncertainty uniquely for each location based on location and time specific observations and their uncertainties. The files contains pixel-level estimates of C storage (plant tissues and dead organic matter), C fluxes (photosynthesis, respiration, fire emissions), allocation of C to plant tissues and their residence times. All variables include uncertainty information reporting the 2.5 %, 25 %, 50 %, 75 % and 97.5% quantiles
Atmospheric profiles of CO₂ as integrators of regional scale exchange
Full text linkThe global climate is changing due to the accumulation of greenhouse gases (GHGs) in the atmosphere, primarily due to anthropogenic activity. The dominant GHG is CO₂ which originates from combustion of fossil fuels, land use change and management. The terrestrial biosphere is a key driver of climate and biogeochemical cycles at regional and global scales. Furthermore, the response of the Earth system to future drivers of climate change will depend on feedbacks between biogeochemistry and climate. Therefore, understanding these processes requires a mechanistic approach in any model simulation framework. However ecosystem processes are complex and nonlinear and consequently models need to be validated against observations at multiple spatial scales. In this thesis the weather research and forecasting model (WRF) has been coupled to the mechanistic terrestrial ecosystem model soil-plant-atmosphere (SPA), creating WRF-SPA. The thesis is split into three main chapters: i. WRF-SPA model development and validation at multiple spatial scales, scaling from surface fluxes of CO₂ and energy to aircraft profiles and tall tower observations of atmospheric CO₂ concentrations. ii. Investigation of ecosystem contributions to observations of atmospheric CO₂ concentrations made at tall tower Angus, Dundee, Scotland using ecosystem specific CO₂ tracers at seasonal and interannual time scales. iii. An assessment of detectability of a policy relevant national scale afforestation by observations made at a tall tower. Detectability of changes in atmospheric CO₂ concentrations was assessed through a comparison of a control simulation, using current day forest extent, and an experimentally afforested simulation using WRF-SPA. WRF-SPA performs well at both site and regional scales, accurately simulating aircraft profiles of CO₂ concentration magnitudes (error <+- 4 ppm), indicating appropriate source sink distribution and realistic atmospheric transport. Hourly observations made at tall tower Angus were also well simulated by WRF-SPA (R² = 0.67, RMSE = 3.5 ppm, bias = 0.58 ppm). Analysis of CO₂ tracers at tall tower Angus show an increase in the seasonal error between WRF-SPA simulated atmospheric CO₂ and observations, which coincides with simulated cropland harvest. WRF-SPA does not simulate uncultivated land associated with agriculture, which in Scotland represents 36 % of agricultural holdings. Therefore, uncultivated land components may provide an explanation for the increase in model-data error. Interannual variation in weather is indicated to have a greater impact on ecosystem specific contributions to atmospheric CO₂ concentrations at Angus than variation in surface activity. In a model experiment, afforestation of Scotland was simulated to test the impact on Scotland’s carbon balance. The changes were shown to be potentially detectable by observations made at tall tower Angus. Afforestation results in a reduction in atmospheric CO₂ concentrations by up to 0.6 ppm at seasonal time scales at tall tower Angus. Detection of changes in forest surface net CO₂ uptake flux due to afforestation was improved through the use of a network of tall towers (R² = 0.83) compared to tall tower Angus alone (R² = 0.75)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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