Analysis and testing of a winter orographic precipitation model

Includes bibliographical references.May 1991.Figure 8 on text page 30 is missing from original.In the mid-1970's, an orographic precipitation model was developed by J. Owen Rhea in an effort to determine the ability to diagnose the effect of topography on winter precipitation for western Colorado. The model was tested for various time periods for differing wind regimes using upper air data and a fine-mesh topographic grid. The model is two-dimensional, steady state and multi-layer. Computations follow parcels at layer mid-points through topographically-induced moist adiabatic ascents and descents. The Lagrangian coordinate system allows for consideration of precipitation shadowing effects by upstream barriers. The model was originally tested for 13 winter seasons and the results were well correlated to observed values of snowpack water equivalent and spring and summer runoff. Although large discrepancies often existed between model and observations on a daily basis, the model frequency distribution of daily precipitation totals was realistic. This study attempted to update and improve the historical comparisons of model calculations to observations and also investigate the application of the model to current-season snowpack diagnosis and prediction. Model calculations were performed for the most recent 15 years of upper air data in addition to the 12 original seasons previously analyzed by Rhea (1978), and the correlation coefficients for model calculated precipitation values and the three observational types maintained good agreement throughout the 27 year historical period. Model calculations using an extended model winter season for the same 27 year period improved these comparisons for the precipitation gauges but had a slightly negative effect on the snowcourse and streamflow runoff relationships. When pre-model and post-model season observed precipitation data were included in the regression analysis for small basin streamflow runoff, some dramatic improvement in the correlations were noted in a few cases. The application of the model for "real-time" diagnosis of the seasonal snowpack was tested in the 1989-90 season and the results were comparable to the Soil Conservation Service predictions. Model calculations utilizing National Meteorological Center (NMC) gridded data as input were performed as a case study and the results were similar to the model calculations utilizing upper air data as well as to the observed precipitation values. The positive results of this study encourage further use of the model for "real-time" snowpack monitoring. Further case studies should be performed to test the model's ability as a predictive tool. The application of interfacing the model to a hydrological process model coupled with improvements such as the use of finer scale topography might further improve spring and summer runoff predictions.Sponsored by National Science Foundation - ATM-8813345 - ATM-8704776 - ATM-8519370.Sponsored by the Colorado Agricultural Experiment Station, Hydrometeorlogy - COL00113

Multi-camera Realtime 3D Tracking of Multiple Flying Animals

Automated tracking of animal movement allows analyses that would not otherwise be possible by providing great quantities of data. The additional capability of tracking in realtime - with minimal latency - opens up the experimental possibility of manipulating sensory feedback, thus allowing detailed explorations of the neural basis for control of behavior. Here we describe a new system capable of tracking the position and body orientation of animals such as flies and birds. The system operates with less than 40 msec latency and can track multiple animals simultaneously. To achieve these results, a multi target tracking algorithm was developed based on the Extended Kalman Filter and the Nearest Neighbor Standard Filter data association algorithm. In one implementation, an eleven camera system is capable of tracking three flies simultaneously at 60 frames per second using a gigabit network of nine standard Intel Pentium 4 and Core 2 Duo computers. This manuscript presents the rationale and details of the algorithms employed and shows three implementations of the system. An experiment was performed using the tracking system to measure the effect of visual contrast on the flight speed of Drosophila melanogaster. At low contrasts, speed is more variable and faster on average than at high contrasts. Thus, the system is already a useful tool to study the neurobiology and behavior of freely flying animals. If combined with other techniques, such as `virtual reality'-type computer graphics or genetic manipulation, the tracking system would offer a powerful new way to investigate the biology of flying animals.Comment: pdfTeX using libpoppler 3.141592-1.40.3-2.2 (Web2C 7.5.6), 18 pages with 9 figure

Estimating Detection Probabilities in Beach Seine Surveys for Estuarine Fishes

Detectability, the probability that a species is encountered if it inhabits a site, is often overlooked in fisheries research despite its potential to obscure habitat use inferences. Detectability can be estimated using models that also provide an estimate of occupancy (Ψ), the probability that a species inhabits a site. I used these models to estimate both probabilities, and to examine factors affecting detectability and occupancy for three fishes in Chesapeake Bay tributaries: young-of-the-year striped bass (Morone saxatilis), yearling Atlantic croaker (Micropogonias undulatus), and spottail shiner (Notropis hudsonius). Occupancy models were fitted to data from a seine survey conducted during summer, 2008 and 2009, in two Chesapeake Bay tributaries. Key assumptions of occupancy models relate to the extent and timing of fish movement: sites are independent, and no site-specific emigration or immigration occurs. A mark-recapture study of striped bass, and previously published studies of Atlantic croaker and spottail shiner, suggested that these assumptions were reasonable. Detectability differed among species and variation was explained by both gear-related and environmental factors. Effective net length (i.e., the distance from shore the seine was deployed) explained variation in detectability for all species; generally, when the effective seine length exceeded 12 m, detectability was higher and less variable. Detectability varied from early to late summer for Atlantic croaker and spottail shiner but not for striped bass. This variation may be attributed to increased net avoidance by Atlantic croaker during late summer and increased relative abundance of spottail shiner due to recruitment of individuals to the gear. Occupancy of striped bass and Atlantic croaker, both of which are transient species, was high (Ψ\u3e0.80), whereas the resident spottail shiner occupied fewer sites (Ψ=0.59±0.21; mean±SE) and occupancy varied by river (ΨMattaponi=0.36±0.11; ΨPamunkey=0.82±0.10). Occupancy models are useful to identify factors affecting detectability of fishes captured by seines in Chesapeake Bay tributaries, but other fisheries studies would benefit from sampling design modifications that maximize detectability and improve habitat-use inferences

Quantum Effective Action in Spacetimes with Branes and Boundaries

We construct quantum effective action in spacetime with branes/boundaries. This construction is based on the reduction of the underlying Neumann type boundary value problem for the propagator of the theory to that of the much more manageable Dirichlet problem. In its turn, this reduction follows from the recently suggested Neumann-Dirichlet duality which we extend beyond the tree level approximation. In the one-loop approximation this duality suggests that the functional determinant of the differential operator subject to Neumann boundary conditions in the bulk factorizes into the product of its Dirichlet counterpart and the functional determinant of a special operator on the brane -- the inverse of the brane-to-brane propagator. As a byproduct of this relation we suggest a new method for surface terms of the heat kernel expansion. This method allows one to circumvent well-known difficulties in heat kernel theory on manifolds with boundaries for a wide class of generalized Neumann boundary conditions. In particular, we easily recover several lowest order surface terms in the case of Robin and oblique boundary conditions. We briefly discuss multi-loop applications of the suggested Dirichlet reduction and the prospects of constructing the universal background field method for systems with branes/boundaries, analogous to the Schwinger-DeWitt technique.Comment: LaTeX, 25 pages, final version, to appear in Phys. Rev.

The Final Fate of Binary Neutron Stars: What Happens After the Merger?

The merger of two neutron stars usually produces a remnant with a mass significantly above the single (nonrotating) neutron star maximum mass. In some cases, the remnant will be stabilized against collapse by rapid, differential rotation. MHD-driven angular momentum transport eventually leads to the collapse of the remnant's core, resulting in a black hole surrounded by a massive accretion torus. Here we present simulations of this process. The plausibility of generating short duration gamma ray bursts through this scenario is discussed.Comment: 3 pages. To appear in the Proceedings of the Eleventh Marcel Grossmann Meeting, Berlin, Germany, 23-29 July 2006, World Scientific, Singapore (2007

Diffeomorphism invariant eigenvalue problem for metric perturbations in a bounded region

We suggest a method of construction of general diffeomorphism invariant boundary conditions for metric fluctuations. The case of $d+1$ dimensional Euclidean disk is studied in detail. The eigenvalue problem for the Laplace operator on metric perturbations is reduced to that on $d$-dimensional vector, tensor and scalar fields. Explicit form of the eigenfunctions of the Laplace operator is derived. We also study restrictions on boundary conditions which are imposed by hermiticity of the Laplace operator.Comment: LATeX file, no figures, no special macro