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Dynamical Climate Drivers of Forest Fire in Western North America and Beyond
No full textBurned forest area has increased significantly in Western North America in recent decades, driven in part by climate conditions becoming more conducive to fire. This dissertation advances our understanding of the large-scale climate dynamics that drive drought and forest fire in Western North America and similar regions around the world. We also investigate the causes and implications of climate model biases in simulating natural climate variability, particularly for modes and phases of variability with large impacts on drought and fire in Western North America.
In the first chapter, we identify regional and global climate patterns in preceding seasons that typically influence the year-to-year variability of burned summer forest area in California. High vapor pressure deficit (VPD), high temperatures, low precipitation, high subsidence, high geopotential height, low soil moisture, and low snowpack and snowmelt anomalies all correlate significantly with July California burned area as far back as the January before the fire season. These climate anomalies occur as part of a hemispheric scale pattern with weak connections to the tropical Pacific Ocean. We explain how climate and weather anomalies, particularly extreme heat, drove the record-breaking burned-area year of 2018.
VPD, a function of temperature and humidity, is a skillful seasonal predictor of burned area in the southwestern United States (the ”Southwest”). Unexpectedly, despite the increased capacity of a warmer atmosphere to hold water vapor, near-surface specific humidity decreased from 1970 to 2019 in much of the Southwest, particularly in spring, summer, and fall. In Chapter 2, we identify declining near-surface humidity from 1970 to 2019 in the Southwest with reanalysis and in situ station data. Focusing on the interior Southwest in the months preceding the summer forest fire season, we find that an early spring decline in precipitation in the interior region induced a decline in soil moisture and evapotranspiration, drying the lower troposphere in summer. This prior season precipitation decline is in turn related to a trend toward a Northern Hemisphere stationary wave pattern that places a high pressure ridge over the interior Southwest. Using fixed humidity and temperature scenarios and the observed exponential relationship between VPD and burned forest area, we estimate that with no increase in temperature at all, the humidity decline alone would still lead to nearly one-quarter of the observed VPD-induced increase in burned area over 1984–2019.
Sea-surface temperature variability in the Pacific plays a powerful role in evolving global hydroclimate on decadal timescales, particularly in Western North America. Chapter 3 evaluates the ability of the current generation of climate models (CMIP6) to simulate realistic decadal sea-surface temperature variability in the Pacific and its teleconnections to circulation, precipitation, and aridity around the world. Using CMIP6 model large ensembles, we evaluate model fidelity in reproducing spatial and temporal characteristics of the Pacific Decadal Oscillation (PDO) and the Interdecadal Pacific Oscillation (IPO), and their hydroclimate teleconnections compared to observations. We find that models’ underestimation of decadal-scale Pacific SST variability is associated with their inability to produce large-amplitude decadal swings in precipitation in Southwestern North America that drive decadal variability in VPD. Finally, in Chapter 4, we investigate and contrast the possible climate drivers of observed increases in fire in the southwestern U.S. versus Eastern Australia, two of the most fire-prone regions of the world with significant, opposite-signed hydroclimate teleconnections to modes of Pacific decadal variability. We show that in both regions, VPD has increased with a large contribution from anthropogenic climate change. In the southwestern U.S., the recent trend in the tropical Pacific west--east sea surface temperature (SST) gradient contributed positively to the VPD-induced increase in burned forest area since 1984. However, in Eastern Australia, the tropical Pacific SST gradient trend has likely offset the anthropogenic climate change-induced increase in burned forest area
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Pacific Decadal Variability and Its Hydroclimate Teleconnections in CMIP6 Models
No full textNatural decadal climate variability in the Pacific, such as the Pacific decadal oscillation (PDO) or the interdecadal Pacific oscillation (IPO), plays a powerful role in evolving global hydroclimate on decadal time scales. Recent generations of general circulation models (GCMs) have been found to simulate the spatial pattern of the PDO well but struggle to capture temporal variability on decadal time scales. To use GCMs to project future climate, we must understand the degree to which climate models can successfully reproduce historical PDO and IPO spatial patterns, temporal behavior, and influence on hydroclimate. We calculate PDO and IPO spatial patterns and time series using 16 models within the CMIP6 archive, all with large (n ≥ 10) ensembles, and compare them to observations in an integrated assessment of models’ ability to represent Pacific decadal variability spatiotemporally. All models underestimate decadal variability in the PDO and IPO and have a westward bias in their PDO and IPO North Pacific SST anomalies. We also evaluate hydroclimate teleconnections of the PDO and IPO in models using PDO- and IPO-associated precipitation, circulation, low-cloud, and vapor pressure deficit anomalies. We show that models’ underpowered decadal variability in the Pacific is consistent with their inability to reproduce large-amplitude decadal swings in precipitation in southwestern North America and that models are virtually unable to produce a 30-yr precipitation trend in the southwest of the magnitude observed from 1982 to 2011. We emphasize the importance of model fidelity in simulating Pacific decadal variability for accurate representation of decadal-scale hydroclimate change in Pacific-teleconnected land regions
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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