A comparison of two identification and tracking methods for polar lows

In this study, we compare two different cyclone-tracking algorithms to detect North Atlantic polar lows, which are very intense mesoscale cyclones. Both approaches include spatial filtering, detection, tracking and constraints specific to polar lows. The first method uses digital bandpass-filtered mean sea level pressure (MSLP) fieldsin the spatial range of 200�600 km and is especially designed for polar lows. The second method also uses a bandpass filter but is based on the discrete cosine transforms (DCT) and can be applied to MSLP and vorticity fields. The latter was originally designed for cyclones in general and has been adapted to polar lows for this study. Both algorithms are applied to the same regional climate model output fields from October 1993 to September 1995 produced from dynamical downscaling of the NCEP/NCAR reanalysis data. Comparisons between these two methods show that different filters lead to different numbers and locations of tracks. The DCT is more precise in scale separation than the digital filter and the results of this study suggest that it is more suited for the bandpass filtering of MSLP fields. The detection and tracking parts also influence the numbers of tracks although less critically. After a selection process that applies criteria to identify tracks of potential polar lows, differences between both methods are still visible though the major systems are identified in both

Features and Outcomes of 899 Patients With Drug-Induced Liver Injury: The DILIN Prospective Study

The drug-induced liver injury network (DILIN) is conducting a prospective study of patients with DILI in the United States. We present characteristics and subgroup analyses from the first 1257 patients enrolled in the study

Automated Knowledge Discovery from Simulators

In this paper, we explore one aspect of knowledge discovery from simulators, the landscape characterization problem, where the aim is to identify regions in the input/ parameter/model space that lead to a particular output behavior. Large-scale numerical simulators are in widespread use by scientists and engineers across a range of government agencies, academia, and industry; in many cases, simulators provide the only means to examine processes that are infeasible or impossible to study otherwise. However, the cost of simulation studies can be quite high, both in terms of the time and computational resources required to conduct the trials and the manpower needed to sift through the resulting output. Thus, there is strong motivation to develop automated methods that enable more efficient knowledge extraction

Thinking Like a Duck: Fall Lake Use and Movement Patterns of Juvenile Ring-Necked Ducks before Migration

<div><p>The post-fledging period is one of the least studied portions of the annual cycle in waterfowl. Yet, recruitment into the breeding population requires that young birds have sufficient resources to survive this period. We used radio-telemetry and generalized estimating equations to examine support for four hypotheses regarding the drivers of landscape scale habitat use and movements made by juvenile ring-necked ducks between the pre-fledging period and departure for migration. Our response variables included the probability of movement, distances moved, and use of different lake types: brood-rearing lakes, staging lakes, and lakes with low potential for disturbance. Birds increased their use of staging areas and lakes with low potential for disturbance (i.e., without houses or boat accesses, >100 m from roads, or big lakes with areas where birds could sit undisturbed) throughout the fall, but these changes began before the start of the hunting season and their trajectory was not changed by the onset of hunting. Males and females moved similar distances and had similar probabilities of movements each week. However, females were more likely than males to use brood-rearing lakes later in the fall. Our findings suggest juvenile ring-necked ducks require different lake types throughout the fall, and managing solely for breeding habitat will be insufficient for meeting needs during the post-fledging period. Maintaining areas with low potential for disturbance and areas suitable for staging will ensure that ring-necked ducks have access to habitat throughout the fall.</p></div

Hypotheses we considered to explain movements and lake use of juvenile ring-necked ducks in the fall.

<p>These hypotheses are not mutually exclusive.</p

Summary of ΔQIC^* measures (model weights^†) associated with generalized estimating equation (GEE) models fit to each of 2 movement-based response variables and 3 wetland characteristics response variables.

<p>^*QIC (Pan 2001) is a measure of model performance for general estimating equations; smaller values indicating better fit, and ΔQIC = QIC – min(QIC).</p>†<p>Model weights = , where M = the number of models in the model set.</p>‡<p>Non-disturbed lakes included all lakes >5,000,000 m² in size, waterfowl refuges, and lakes >100 m from a road with no boat access or house on the lake.</p><p>Bold values indicate the ‘best fit’ model for each response variable.</p

Distances radio-marked ring-necked ducks moved between locations in successive weeks, given they changed lakes.

<p>Open circles correspond to observed proportions (with 95% confidence intervals) during the falls of 2007–2010. Solid black line gives predictions from the ‘best-fit’ generalized estimating equation model (chosen using QIC). The gray vertical line (and hatched fill) demarcates the hunting season.</p

Study area and capture locations of young ring-necked ducks.

<p>Black dots indicate capture locations of birds on brood-rearing lakes in north-central Minnesota, USA during 2007–2010. Lakes and rivers are depicted in grey.</p