An Objective Analysis Technique for Constructing Three-Dimensional Urban-Scale Wind Fields

An objective analysis procedure for generating mass-consistent, urban-scale three-dimensional wind fields is presented together with a comparison against existing techniques. The algorithm employs terrain following coordinates and variable vertical grid spacing. Initial estimates of the velocity field are developed by interpolating surface and upper level wind measurements. A local terrain adjustment technique, involving solution of the Poisson equation, is used to establish the horizontal components of the surface field. Vertical velocities are developed from successive solutions of the continuity equation followed by an iterative procedure which reduces anomalous divergence in the complete field. Major advantages of the procedure are that it is computationally efficient and allows boundary values to adjust in response to changes in the interior flow. The method has been successfully tested using field measurements and problems with known analytic solutions

Use of models to establish source-receptor relationships and estimate relative source contributions of NO_x to air quality problems

A basic objective of the Technical Symposium on the Implications of a Low NO_x Vehicle Emission Standard is to examine the need for and technical feasibility of a low NO_x emission standard for future light-duty motor vehicles. A major component of this assessment is to estimate the changes in air quality that would result from the imposition of a low NO_x vehicle emission standard. Such an assessment requires a method for relating emission to air quality changes, i.e. a so-called air quality model. In this summary, we focus on those air quality models that may be used to estimate the impact of changes in the NO_x emission levels from motor vehicles

Convective Downmixing of Plumes in a Coastal Environment

This paper describes the results of an atmospheric tracer study in which sulfur hexafluoride (SF_6) was used to investigate the transport and dispersion of effluent from a power plant located in a coastal environment. The field study demonstrated that material emitted into an elevated stable layer at night can be transported out over the ocean, fumigated to the surface, and then he returned at ground level by the sea breeze on the next day. At night when cool stable air from the land encounters the warmer ocean convective mixing erodes the stable layer forming an internal boundary layer. When the growing boundary layer encounters an elevated plume the pollutant material, entrained at the top of the mixed layer, can be rapidly transported in ∼20 min to the surface. Various expressions for the characteristic downmixing time (λ = Z_i/w_*) are developed utilizing the gradient Richardson number, the Monin-Obukhov length and turbulence intensifies. Calculations using these expressions and the field data are compared with similar studies of convective mixing over the land

Mathematical modeling of photochemical air pollution

A particularly serious problem facing densely populated areas is the environmental degradation caused by the presence of photochemical air pollution. The problem is both pervasive and difficult to control. An important element of any rational approach directed at attempting to improve the situation is a reliable means for evaluating the air quality impact of alternative control measures. This report presents such a capability in the form of a mathematical description of the production and transport of photochemical oxidants within an urban airshed

Gender Differences in Emotion Regulation: An fMRI Study of Cognitive Reappraisal

Despite strong popular conceptions of gender differences in emotionality and striking gender differences in the prevalence of disorders thought to involve emotion dysregulation, the literature on the neural bases of emotion regulation is nearly silent regarding gender differences (Gross, 2007; Ochsner & Gross, in press). The purpose of the present study was to address this gap in the literature. Using functional magnetic resonance imaging, we asked male and female participants to use a cognitive emotion regulation strategy (reappraisal) to down-regulate their emotional responses to negatively valenced pictures. Behaviorally, men and women evidenced comparable decreases in negative emotion experience. Neurally, however, gender differences emerged. Compared with women, men showed (a) lesser increases in prefrontal regions that are associated with reappraisal, (b) greater decreases in the amygdala, which is associated with emotional responding, and (c) lesser engagement of ventral striatal regions, which are associated with reward processing. We consider two non-competing explanations for these differences. First, men may expend less effort when using cognitive regulation, perhaps due to greater use of automatic emotion regulation. Second, women may use positive emotions in the service of reappraising negative emotions to a greater degree. We then consider the implications of gender differences in emotion regulation for understanding gender differences in emotional processing in general, and gender differences in affective disorders

Global sensitivity analysis—a computational implementation of the Fourier Amplitude Sensitivity Test (FAST)

This paper describes a computational implementation of the Fourier Amplitude Sensitivity Test (FAST) and illustrates its use with a sample problem. The FAST procedure is ideally suited to the task of determining the global sensitivity of nonlinear mathematical models subjected to variations of arbitrary size in either the system parameters or initial conditions. A FORTRAN computer program, capable of performing sensitivity analyses of either algebraic or differential equation systems is described