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"MacDonald, M."
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Observed controls on resilience of groundwater to climate variability in sub-Saharan Africa
Groundwater in sub-Saharan Africa supports livelihoods and poverty alleviation
1
,
2
, maintains vital ecosystems, and strongly influences terrestrial water and energy budgets
3
. Yet the hydrological processes that govern groundwater recharge and sustainability—and their sensitivity to climatic variability—are poorly constrained
4
,
5
. Given the absence of firm observational constraints, it remains to be seen whether model-based projections of decreased water resources in dry parts of the region
4
are justified. Here we show, through analysis of multidecadal groundwater hydrographs across sub-Saharan Africa, that levels of aridity dictate the predominant recharge processes, whereas local hydrogeology influences the type and sensitivity of precipitation–recharge relationships. Recharge in some humid locations varies by as little as five per cent (by coefficient of variation) across a wide range of annual precipitation values. Other regions, by contrast, show roughly linear precipitation–recharge relationships, with precipitation thresholds (of roughly ten millimetres or less per day) governing the initiation of recharge. These thresholds tend to rise as aridity increases, and recharge in drylands is more episodic and increasingly dominated by focused recharge through losses from ephemeral overland flows. Extreme annual recharge is commonly associated with intense rainfall and flooding events, themselves often driven by large-scale climate controls. Intense precipitation, even during years of lower overall precipitation, produces some of the largest years of recharge in some dry subtropical locations. Our results therefore challenge the ‘high certainty’ consensus regarding decreasing water resources
4
in such regions of sub-Saharan Africa. The potential resilience of groundwater to climate variability in many areas that is revealed by these precipitation–recharge relationships is essential for informing reliable predictions of climate-change impacts and adaptation strategies.
Analysis of multidecadal hydrograph and precipitation data for sub-Saharan Africa shows a complex relationship between groundwater recharge and precipitation, and that a drier climate does not necessarily mean less recharge.
Journal Article
Roughness effects in turbulent forced convection
We conducted direct numerical simulations of turbulent flow over three-dimensional sinusoidal roughness in a channel. A passive scalar is present in the flow with Prandtl number
$Pr=0.7$
, to study heat transfer by forced convection over this rough surface. The minimal-span channel is used to circumvent the high cost of simulating high-Reynolds-number flows, which enables a range of rough surfaces to be efficiently simulated. The near-wall temperature profile in the minimal-span channel agrees well with that of the conventional full-span channel, indicating that it can be readily used for heat-transfer studies at a much reduced cost compared to conventional direct numerical simulation. As the roughness Reynolds number,
$k^{+}$
, is increased, the Hama roughness function,
$\\unicode[STIX]{x0394}U^{+}$
, increases in the transitionally rough regime before tending towards the fully rough asymptote of
$\\unicode[STIX]{x1D705}_{m}^{-1}\\log (k^{+})+C$
, where
$C$
is a constant that depends on the particular roughness geometry and
$\\unicode[STIX]{x1D705}_{m}\\approx 0.4$
is the von Kármán constant. In this fully rough regime, the skin-friction coefficient is constant with bulk Reynolds number,
$Re_{b}$
. Meanwhile, the temperature difference between smooth- and rough-wall flows,
$\\unicode[STIX]{x0394}\\unicode[STIX]{x1D6E9}^{+}$
, appears to tend towards a constant value,
$\\unicode[STIX]{x0394}\\unicode[STIX]{x1D6E9}_{FR}^{+}$
. This corresponds to the Stanton number (the temperature analogue of the skin-friction coefficient) monotonically decreasing with
$Re_{b}$
in the fully rough regime. Using shifted logarithmic velocity and temperature profiles, the heat-transfer law as described by the Stanton number in the fully rough regime can be derived once both the equivalent sand-grain roughness
$k_{s}/k$
and the temperature difference
$\\unicode[STIX]{x0394}\\unicode[STIX]{x1D6E9}_{FR}^{+}$
are known. In meteorology, this corresponds to the ratio of momentum and heat-transfer roughness lengths,
$z_{0m}/z_{0h}$
, being linearly proportional to the inner-normalised momentum roughness length,
$z_{0m}^{+}$
, where the constant of proportionality is related to
$\\unicode[STIX]{x0394}\\unicode[STIX]{x1D6E9}_{FR}^{+}$
. While Reynolds analogy, or similarity between momentum and heat transfer, breaks down for the bulk skin-friction and heat-transfer coefficients, similar distribution patterns between the heat flux and viscous component of the wall shear stress are observed. Instantaneous visualisations of the temperature field show a thin thermal diffusive sublayer following the roughness geometry in the fully rough regime, resembling the viscous sublayer of a contorted smooth wall.
Journal Article
John of Brienne : king of Jerusalem, emperor of Constantinople, c.1175-1237
\"John of Brienne's progress, from mid-ranking knightly status to king of Jerusalem and later Latin emperor of Constantinople, traces one of the most remarkable careers in the entire medieval period. But how and why did he achieve such heights? This biographical study of aristocratic social and geographical mobility in the 'Age of the Crusades' reassesses John's fascinating life, and explores how families and dynasticism, politics, intrigue, religion and war all contributed to John's unprecedented career. A major figure in the history of the thirteenth-century Mediterranean, and yet very much a product of the workings of the society of his day, this book reveals how John's life, and its multifarious connections to France, Italy, the German empire and the papacy, can illuminate the broad panorama of the early thirteenth-century world, and the zenith of the Crusading movement\"-- Provided by publisher.
Book
Citywide cluster randomized trial to restore blighted vacant land and its effects on violence, crime, and fear
Vacant and blighted urban land is a widespread and potentially risky environmental condition encountered by millions of people on a daily basis. About 15% of the land in US cities is deemed vacant or abandoned, an area roughly the size of Switzerland. In a citywide cluster randomized controlled trial, we investigated the effects of standardized, reproducible interventions that restore vacant land on the commission of violence, crime, and the perceptions of fear and safety. Quantitative and ethnographic analyses were included in a mixed-methods approach to more fully test and explicate our findings. A total of 541 randomly sampled vacant lots were randomly assigned into treatment and control study arms; outcomes from police and 445 randomly sampled participants were analyzed over a 38-month study period. Participants living near treated vacant lots reported significantly reduced perceptions of crime (−36.8%, P < 0.05), vandalism (−39.3%, P < 0.05), and safety concerns when going outside their homes (−57.8%, P < 0.05), as well as significantly increased use of outside spaces for relaxing and socializing (75.7%, P < 0.01). Significant reductions in crime overall (−13.3%, P < 0.01), gun violence (−29.1%, P < 0.001), burglary (−21.9%, P < 0.001), and nuisances (−30.3%, P < 0.05) were also found after the treatment of vacant lots in neighborhoods below the poverty line. Blighted and vacant urban land affects people’s perceptions of safety, and their actual, physical safety. Restoration of this land can be an effective and scalable infrastructure intervention for gun violence, crime, and fear in urban neighborhoods.
Journal Article
TaymāʼII : Catalogue of the inscriptions discovered in the Saudi-German excavations at Taymāʼ 2004-2015
Tayma' II is a Catalogue which contains all the inscriptions discovered during the 24 seasons of the Saudi- German excavations at Tayma' from 2004-15 which were funded by the German Research Foundation (DFG). The 113 objects carry inscriptions in different languages and scripts, illustrating the linguistic diversity of the oasis through time. Although the majority are fragmentary, they provide an important source for the history of the oasis in ancient and mediaeval times.0The Babylonian cuneiform inscriptions in this volume confirm for the first time the ten-year sojourn at Tayma' of the last Babylonian king Nabu-na'id (556-539 BC). In addition, Imperial Aramaic inscriptions dated by the reigns of Lihyanite kings, based at Dadan (modern al-'Ula), reveal for the first time that they ruled Tayma' at a period in the second half of the first millennium BC.0As well as editing the volume, Michael C. A. Macdonald edited the Imperial Aramaic inscriptions found from 2010-15, plus those in the form of the Aramaic script which developed in Tayma', and the Nabataean, Dadanitic, and Taymanitic texts. In addition, Hanspeter Schaudig edited the cuneiform inscriptions; Peter Stein, the Imperial Aramaic texts found from 2004-09; and Frederic Imbert, the Arabic inscriptions. Arnulf Hausleiter and Francelin Tourtet provided archaeological contributions, while Martina Trognitz curated the virtual edition of many of the texts recorded by RTI. The indexes contain the words and names from all known texts from the oasis, including those in the Tayma' Museum and other collections which will be published as Tayma' III.
Book
Changes in global groundwater organic carbon driven by climate change and urbanization
Climate change and urbanization can increase pressures on groundwater resources, but little is known about how groundwater quality will change. Here, we use a global synthesis (
n
= 9,404) to reveal the drivers of dissolved organic carbon (DOC), which is an important component of water chemistry and substrate for microorganisms that control biogeochemical reactions. Dissolved inorganic chemistry, local climate and land use explained ~ 31% of observed variability in groundwater DOC, whilst aquifer age explained an additional 16%. We identify a 19% increase in DOC associated with urban land cover. We predict major groundwater DOC increases following changes in precipitation and temperature in key areas relying on groundwater. Climate change and conversion of natural or agricultural areas to urban areas will decrease groundwater quality and increase water treatment costs, compounding existing constraints on groundwater resources.
Groundwater is Earth’s largest source of freshwater, but the cost and ease with which it is turned to drinking water is dependent on the concentration of organic carbon. Here the authors show that climate change and urbanization will likely elevate future levels of groundwater dissolved organic carbon across the globe.
Journal Article
The Briennes : The rise and fall of a Champenois Dynasty in the age of the Crusades, c. 950-1356
\"The Briennes were a highly important aristocratic family who hailed from the Champagne region of north-eastern France, but whose reach and impact extended across Europe and into the Crusader States in the Middle East. It is a highly dramatic and wide-ranging story of medieval mobility, not only up and down the social ladder, but in geographical terms as well. Although the Briennes were one of the great dynasties of the central Middle Ages, this book represents the first comprehensive history of the family. Taking the form of parallel biographies and arranged broadly chronologically, it explores not only their rise, glory and fall, but also how they helped to shape the very nature of the emerging European state system. This book will appeal to students and scholars of medieval France, the Mediterranean world, the Crusades and the central Middle Ages\"-- Provided by publisher.
Book
Predictors of willingness to get a COVID-19 vaccine in the U.S
Background
As COVID-19 vaccine distribution efforts continue, public health workers can strategize about vaccine promotion in an effort to increase willingness among those who may be hesitant.
Methods
In April 2020, we surveyed a national probability sample of 2279 U.S. adults using an online panel recruited through address-based sampling. Households received a computer and internet access if needed to participate in the panel. Participants were invited via e-mail and answered online survey questions about their willingness to get a novel coronavirus vaccine when one became available. The survey was completed in English and Spanish. We report weighted percentages.
Results
Most respondents were willing to get the vaccine for themselves (75%) or their children (73%). Notably, Black respondents were less willing than White respondents (47% vs. 79%,
p
< 0.001), while Hispanic respondents were more willing than White respondents (80% vs. 75%,
p
< 0.003). Females were less likely than males (72% vs. 79%,
p
< 0.001). Those without insurance were less willing than the insured (47% vs. 78%,
p
< 0.001). Willingness to vaccinate was higher for those age 65 and older than for some younger age groups (85% for those 65 and older vs. 75% for those 50–64,
p
< 0.017; 72% for those 35–49,
p
< 0.002; 70% for those 25–34,
p
= NS and 75% for ages 18–24,
p
= NS), but other groups at increased risk because of underlying medical conditions or morbid obesity were not more willing to get vaccinated than their lower risk counterparts.
Conclusions
Most Americans were willing to get a COVID-19 vaccine, but several vulnerable populations reported low willingness. Public health efforts should address these gaps as national implementation efforts continue.
Journal Article