The impact of model-error correlation on regional data assimilative models and their observational arrays

Data assimilative models often minimize a penalty functional that measures model adjustment and model-data misfit. The penalty functional builds assumptions about model error into the analysis. Usually, errors from different parts of the model (e.g., dynamics and boundary conditions) are presumed to be uncorrelated. This is clearly not a valid assumption in regional models where uncertain large-scale forcing affects open-ocean boundary conditions. In this study, calculations with a regional wind-driven inverse model provide a specific example where model error from uncertain wind stress is correlated with model error from uncertain open boundary conditions. This physically realistic scenario motivates development of a more general penalty functional that includes model-error correlation. In fact, model-error correlations must be included in order to meet the objective of making the open-ocean boundaries behave like the open ocean. Statistical issues for the generalized inverse model are described in the context of objective analysis. Implications for array design are addressed. For data assimilative models that incorrectly neglect model-error correlation, data should not come from open-ocean boundary regions. Rather, data should come from the interior of the regional domain. There is no such restriction on data placement for the assimilative model that correctly accounts for model-error correlation

Generalized inverse with shipboard current measurements: Tidal and nontidal flows in Long Island Sound

A simple linear shallow-water model forced by tidal boundary conditions can capture most of the tide height variability in Long Island Sound. In this sense, the tides are easy to model. The modeled tidal currents can be subtracted from measurements in order to obtain estimates of subtidal circulation. But linear shallow-water dynamics is not accurate enough for this purpose. Allowing for dynamical errors with a generalized inverse model leads to improved estimates of tidal and nontidal flow. The analysis provides expected errors for the prior (before inversion) and posterior (after inversion) tidal velocity field. Estimates of the flow field in central Long Island Sound are obtained with current measurements from a ship-mounted Acoustic Doppler Current Profiler (ADCP) survey. Inversion of data from a single ten-hour survey improves tidal predictions, as verified with independent data. Furthermore, the posterior penalty functional is shown to be an effective test statistic for the existence of nontidal flow. The inverse model reduces model-data misfit, using interior dynamics and open-boundary conditions as weak constraints. Model-data misfit can also be reduced by tuning the friction parameter in the prior tidal model. However, in contrast with inversion, tuning degrades predictability

The Amish Symposium

The Amish is a 500-some page university press-sized handbook that touches on a variety of topical areas. The book is the culmination of two and a half decades each of Kraybill’s, Johnson-Weiner’s, and Nolt’s work about the Amish. Karen Johnson-Weiner published a series of linguistic studies through the 1990s, and from these spring-board works later explored more fully schools and New York settlements. Donald Kraybill’s first Amish-focused publication was a Durkheimian study of the Amish and suicide in 1986. From then on he has maintained this functionalist orientation in comparative studies of plain Anabaptists and Amish responses to cultural, economic, and political change. Steven Nolt’s work follows two threads: Amish history, of which his A History of the Amish (1992) stands as the premiere testament, and Amish identity, realized most fully in Plain Diversity (2007), co-authored with Thomas Meyers. While Kraybill and Nolt have collaborated on seven publications, this is Johnson-Weiner’s first publication with either. Given the book’s volumous size and its claim to be the first generalist book about the Amish since John Hostetler’s first edition of Amish Society (1963), we as co-editors felt the book merited special review via a symposium in JAPAS. Three respondents provide reviews: a scholar of the Amish, a scholar outside Amish studies, and an Amishman. The first is Steven Reschly, a JAPAS editorial board member whose research focuses on Midwestern Amish and Amish from around the 1870s to 1930s. His work extends Bourdieau’s theories by arguning for a community-based Amish repetoire of action. The second reviewer is Benjamin Zeller, who has published several books about New Religious Movements and religion & food. He is Assistant Professor of Religion at Lake Forest College. The third reviewer is Tom Coletti, a long-term convert to the Amish and a farmer in the Union Grove, NC, community. Megan Bogden, a former student in Ohio State University’s Amish Society course, provides a brief book summary. —Cory Anderson, co-edito

The North Atlantic circulation: Combining simplified dynamics with hydrographic data

We estimate the time-averaged velocity field in the North Atlantic from observations of density, wind stress and bottom topography. The flow is assumed geostrophic, with prescribed Ekman pumping at the surface, and no normal component at the bottom. These data and dynamics determine velocity to within an arbitrary function of (Coriolis parameter)/(ocean depth), which we call the “dynamical free mode.” The free mode is selected to minimize mixing of potential density at mid-depth. This tracer-conservation criterion serves as a relatively weak constraint on the calculation. Estimates of vertical velocity are particularly sensitive to variations in the free mode and to errors in density. In contrast, horizontal velocities are relatively robust. Below the thermocline, we predict a strong O (1 cm/sec) westward flow across the entire North Atlantic, in a narrow range of latitude between 25N and 32N. This feature supports the qualitative (and controversial) conjecture by Wüst (1935) of flow along the “Mediterranean Salt Tongue.” Along continental margins and at the Mid-Atlantic Ridge, predicted bottom velocity points along isobaths, with shallow water to the right. These flows agree with many long-term current measurements and with notions of the circulation based on tracer distributions. The results conflict with previous oceanographic-inverse models, which predict mid-depth flows an order of magnitude smaller and often in opposite directions. These discrepancies may be attributable to our relatively strong enforcement of the bottom boundary condition. This involves the plausible, although tenuous, assertion that the flow “feels” only the large-scale features of the bottom topography. Our objective is to investigate the consequences of using this hypothesis to estimate the North Atlantic circulation

Hardiness as a predictor of success for marine corps first responders in training

Military personnel and first responders operate in complex operational environments, and must be able to perform under physical, psychological, and emotional stress. Research suggests that resiliency assuages stress and improves the performance of military personnel and first responders. However, there are no studies examining the effects of resiliency on military first responders in training. The purpose of this research was to determine whether the dispositional hardiness traits of commitment, control and challenge displayed by Marine aircraft rescue and firefighting (ARFF) specialist trainees correlated to success in classroom performance, success during practical exercises, higher graduation rates. The theoretical foundation for this ex post facto quantitative study was psychological and organizational resiliency, as represented by Kobasa\u27s hardiness theory. The convenience sample consisted of 60 Marine ARFF specialists trainees using self-report surveys during 2013. Independent samples t tests and hierarchical regression analyses revealed no statistical significance between higher hardiness levels and academic and practical application performance, although physical injury and other factors not measured by the hardiness construct were found to impact graduation rates negatively. The implications for positive social change include expanding organizational conceptions of resilience to measure dispositional factors not assessed by hardiness. This study may also offer insights into improving Marine Corps and first responder selection, training, and educational programs, as well as their performance and quality of life