Short-term Temporal Fluctuations Research Articles

An online trajectory module (version 1.0) for the nonhydrostatic numerical weather prediction model COSMO

Abstract. A module to calculate online trajectories has been implemented into the nonhydrostatic limited-area weather prediction and climate model COSMO. Whereas offline trajectories are calculated with wind fields from model output, which is typically available every one to six hours, online trajectories use the simulated resolved wind field at every model time step (typically less than a minute) to solve the trajectory equation. As a consequence, online trajectories much better capture the short-term temporal fluctuations of the wind field, which is particularly important for mesoscale flows near topography and convective clouds, and they do not suffer from temporal interpolation errors between model output times. The numerical implementation of online trajectories in the COSMO-model is based upon an established offline trajectory tool and takes full account of the horizontal domain decomposition that is used for parallelization of the COSMO-model. Although a perfect workload balance cannot be achieved for the trajectory module (due to the fact that trajectory positions are not necessarily equally distributed over the model domain), the additional computational costs are found to be fairly small for the high-resolution simulations described in this paper. The computational costs may, however, vary strongly depending on the number of trajectories and trace variables. Various options have been implemented to initialize online trajectories at different locations and times during the model simulation. As a first application of the new COSMO-model module, an Alpine north foehn event in summer 1987 has been simulated with horizontal resolutions of 2.2, 7 and 14 km. It is shown that low-tropospheric trajectories calculated offline with one- to six-hourly wind fields can significantly deviate from trajectories calculated online. Deviations increase with decreasing model grid spacing and are particularly large in regions of deep convection and strong orographic flow distortion. On average, for this particular case study, horizontal and vertical positions between online and offline trajectories differed by 50–190 km and 150–750 m, respectively, after 24 h. This first application illustrates the potential for Lagrangian studies of mesoscale flows in high-resolution convection-resolving simulations using online trajectories.

Fate of β-blocker human pharmaceuticals in surface water: Comparison of measured and simulated concentrations in the Glatt Valley Watershed, Switzerland

This study focused on the occurrence and fate of four β-blockers (atenolol, sotalol, metoprolol, propranolol) in wastewater and surface water. Measured concentrations were compared with predicted concentrations using an implementation of the geo-referenced model GREAT-ER for the Glatt Valley Watershed (Switzerland). Particularly, the question was addressed how measured and simulated data could complement each other for the exposure assessment of human pharmaceuticals and other micropollutants entering surface water through wastewater treatment plants (WWTP). Concentrations in the Glatt River ranged from <LOQ to 83 ng L −1 with the highest concentrations found for atenolol. Higher loads were measured on days with combined sewer overflow events during high flow conditions. GREAT-ER was able to predict spatially resolved river concentrations based on average consumption and excretion data, removal in wastewater treatment plants (WWTPs) and dissipation and degradation processes in surface water within a factor of 2. These results indicate that modelling might be sufficient to estimate daily average exposure concentrations for compounds that are either recalcitrant or whose degradation and sorption behaviour can be predicted with confidence based on laboratory experiments. Chemical measurements, in contrast, should be reserved for assessing point sources, investigating mechanisms which lead to short-term temporal fluctuations in compound loads, and determining in-situ degradation rates in conjunction with modelling.

Composition, diversity and short-term temporal fluctuations of zooplankton communities in fish culture ponds (Pindamonhangaba), SP

The present study aimed at evaluating the composition, diversity and short-term temporal fluctuations of zooplankton communities in fish ponds. The study was carried out in two fish ponds, with 180 m(2) of water surface (6 x 30 m) each, located in the Aquiculture Centre of the Pindamonhangaba Fisheries Institute - São Paulo. The study was developed over eight weeks, from February 16 to April 6, 1998. The physical and chemical conditions of the water in the fish ponds were adequate for zooplankton development. The zooplanktonic community was characterised by high richness of species and a greater diversity was observed in the first fish pond, with a superior density of Rotifera. Temporal changes in zooplankton composition occurred in both ponds with Cladocera appearing in abundance later, in the fourth week, whereas copepods and rotifers were well represented since the beginning. Many species found are typical of fish ponds and are considered to constitute an excellent food source, showing high nutritional value for fish larvae, a good example being individuals from the Rotifera group and the micro-crustacean species Moina minuta and Thermocyclops decipiens.

Calculation of odour emissions from aircraft engines at Copenhagen Airport

In a new approach the odour emissions from aircraft engines at Copenhagen Airport are calculated using actual fuel flow and emission measurements (one main engine and one APU: Auxiliary Power Unit), odour panel results, engine specific data and aircraft operational data for seven busy days. The calculation principle assumes a linear relation between odour and HC emissions. Using a digitalisation of the aircraft movements in the airport area, the results are depicted on grid maps, clearly reflecting aircraft operational statistics as single flights or total activity during a whole day. The results clearly reflect the short-term temporal fluctuations of the emissions of odour (and exhaust gases). Aircraft operating at low engine thrust (taxiing, queuing and landing) have a total odour emission share of almost 98%, whereas the shares for the take off/climb out phases (2%) and APU usage (0.5%) are only marginal. In most hours of the day, the largest odour emissions occur, when the total amount of fuel burned during idle is high. However, significantly higher HC emissions for one specific engine cause considerable amounts of odour emissions during limited time periods. The experimentally derived odour emission factor of 57 OU/mg HC is within the range of 23 and 110 OU/mg HC used in other airport odour studies. The distribution of odour emission results between aircraft operational phases also correspond very well with the results for these other studies. The present study uses measurement data for a representative engine. However, the uncertainties become large when the experimental data is used to estimate the odour emissions for all aircraft engines. More experimental data is needed to increase inventory accuracy, and in terms of completeness it is recommended to make odour emission estimates also for engine start and the fuelling of aircraft at Copenhagen Airport in the future.

Predictive strategies in interception tasks: differences between eye and hand movements

To investigate how the sensorimotor systems of eye and hand use position, velocity, and timing information of moving targets, we conducted a series of three experiments. Subjects performed combined eye-hand catch-up movements toward visual targets that moved with step-ramp-like velocity profiles. Visual feedback of the hand was prevented by blanking the target at the onset of the hand movement. A multiple regression was used to determine the effects of position, velocity, and timing accessed before each movement on the movement amplitudes of eye and hand. The following results were obtained: 1. The predictive strategy of eye movements could be modeled by a linear regression on the basis of the position error and the target velocity. This was not the case for hand movements, for which there was a significant partial correlation between the movement amplitude and the product of target velocity and movement duration. This correlation was not observed for eye movements suggesting that the predictive strategy of hand movements takes movement duration into account, in contrast to the strategy used in eye movements. 2. To determine whether the movement amplitudes of eye and hand depend on a categorical classification between a discrete number of movement types, we compared an experiment in which target position and velocity were distributed continuously with an experiment using only four different combinations of target position and velocity. No systematic differences between these experiments were observed. This shows that the system output is a function of continuous, interval-scaled variables rather than a function of discrete categorical variables. 3. We also analyzed the component of the movement amplitudes not explained by the regression, i.e., the residual error. The residual errors between subsequent trials were correlated more strongly for eye than for hand movements, suggesting that short-term temporal fluctuations of the predictive strategy were stronger for the eye than for the hand.

Temporally fluctuating prey and interfering predators: a positive feedback

Prey densities often show fluctuating patterns over various timescales. Focusing on short-term, within-generation fluctuating patterns of local prey availability, we suggest that prey that show synchronized and high-amplitude fluctuations in availability experience decreased risks of predation, but also enhance the maintenance of predator interference hierarchies by affecting the relative foraging success of unequal conspecific interferers. When predators interfere with each other, they forage less intensely on prey, which benefits prey in terms of decreased predation risk. The system hence involves a positive feedback. We thus argue that short-term temporal fluctuations in local prey availability could be an important mechanism behind how interference-structured social predator systems are developed and sustained. The temporal fluctuations also have implications for the phenotypic diversity of predators, and may be involved in speciation processes.

Longitudinal population-based twin study of retrospectively reported premenstrual symptoms and lifetime major depression.

While family and twin studies suggest that retrospectively reported premenstrual symptoms are heritable, these studies have not accounted for the unreliability of such measures. In addition, we know little about the relationship of the familial risk factors for premenstrual symptoms and major depression. Lifetime major depression and premenstrual-related tiredness, sadness, and irritability were assessed twice over 6 years in 1,312 menstruating female twins ascertained from a population-based twin register. A twin-measurement model--which permits estimation of the etiologic roles of genetic and environmental factors with correction for errors of measurement or short-term temporal fluctuations--was applied to these data. A single premenstrual symptom factor was found that was moderately stable over time. The best-fitting twin-measurement model estimated the heritability of the stable component of premenstrual symptoms at 56% and showed no impact of family-environmental factors. A bivariate twin-measurement model estimated that the genetic and environmental risk factors for lifetime major depression contributed only modestly to the etiology of premenstrual syndrome. No evidence was found for significant biases in the twin method. Retrospectively reported premenstrual-related symptoms of depression and anxiety are moderately stable over time and, when correction is made for this level of stability, substantially heritable. The genetic and environmental risk factors for these premenstrual symptoms and lifetime major depression are not closely related.

Ultraviolet spectrophotometry of comet Giacobini-Zinner during the ICE encounter

A program of ultraviolet spectrophotometry using the International Ultraviolet Explorer (IUE) Observatory was carried out in support of the International Cometary Explorer (ICE) mission. The H 2O production rate was monitored from 1985 June to October. Between 1985 September 9 and 12, the spatial and temporal variation and abundance (or upper limits) of the remotely detectable species, C, CO, CO +, CO 2 +, CS, H, Mg +, O, OH, and S, were obtained. These observations included the time of the ICE encounter (1985 September 11.46) when the H 2O production rate was 3 × 10 28 sec −1 ± 50%. This rate is consistent with a number of gas production rates derived indirectly from the ICE experiments. The comet was in a nearly steady state around the time of encounter showing no evidence of short-term temporal fluctuations in brightness greater than 6%. A sunward-tailward asymmetry of the OH brightness was observed at 10,000 km from the nucleus. The absence of detected Mg + rules out this species as a possible ion of M Q = 24 which was detected by the Ion Composition Instrument, part of the ICE complement of instruments. Comparison of the abundance of CO 2 + ions with total electron density measured by the plasma electron and radio science experiments on ICE indicates a deficiency of ions relative to electrons. To satisfy charge balance criteria, a major population of ions not detected by remote sensing must be present.

Development of a Comprehensive Oxygen-Deficient Marine Biofacies Model: Evidence from Santa Monica, San Pedro, and Santa Barbara Basins, California Continental Borderland

An extensive data base of box core x-radiographs, bottom photographs, and box core faunal data has been employed to establish the relationships between dissolved oxygen content and (1) sediment fabric, (2) biogenic structure distribution and size trends, and (3) faunal composition and species richness in three anoxic silled basins of the California continental borderland. Sediments of anaerobic environments are generally well laminated, whereas those of aerobic and dysaerobic environments are completely bioturbated. Intermediate, partially bioturbated sediments are produced near the present dysaerobic-anaerobic boundary by short-term temporal fluctuations in the position of the dysaerobic-anaerobic boundary. Although distribution of burrow types observed in x-radiographs does not show significant control by variations in dissolved oxygen, average size of burrows decreases markedly with decreasing oxygen. In terms of surface biogenic structures, most aerobic and upper dysaerobic sea floors are dominated by tracks and trails, but lower dysaerobic sea floors are characterized by burrow openings. No surface biogenic structures were observed on anaerobic sea floors. Regular and irregular echinoids dominate sea-floor surfaces in aerobic and upper dysaerobic environments, whereas polychaetes, ophiuroids, holothurians, small arthropods, and gastropods are common on lower dysaerobic sea floors. No surface-dwelling organisms were visible on anaerobic bottoms. Box core faunal analysis indicates that species richness generally decreases with increased depth and decreasing oxygen until it reaches near zero at the dysaerobic-anaerobic boundary. The most abrupt decrease in species richness occurs at the shelf-slope transition. These observations are highly supportive of criteria cited by Rhoads and Morse (1971) and Byers (1977) for distinguishing anaerobic facies from more oxygenated facies in ancient strata. However, their criteria for distinguishing between ancient aerobic and dysaerobic facies are not as definitive. Paleontologic criteria, biogenic structure size trends, and other rock characteristics are useful for establishing paleo-oxygen gradients but not for determining specific paleo-oxygen concentrations as there are no abrupt oxygen-controlled changes in these parameters above the anaerobic-dysaerobic boundary.

Adaptive “coin-flipping”: a decision-theoretic examination of natural selection for random individual variation

A potentially important source of individual phenotypic variation is examined which has heretofore received little recognition as a general and probably widespread phenomenon. Neither the expression of genetic variation nor plasticity of the usual sort, it represents a kind of variation that is random, yet adaptive. A result of decision-theoretic strategy-mixing, such variation is needed in order to maximize long-term fitness in the face of unpredictable short-term temporal fluctuations in the environment. The variation is a product of the action of genetically controlled stochastic processes; metaphorically, it is produced because individuals are genetically programmed to “flip coins” to decide what characteristics to adopt. Thus it is not the variable phenotypic traits themselves that are genetically specified, but only the nature of the coin-flipping process that will ultimately determine them. It is shown that coin-flipping strategies of this kind are robust and can evolve under a variety of conditions.

Material Fluxes through the North-Inletmarsh System: Short-Term Temporal Fluctuations of Fungi and Related Parameters

SUMMARYThe fluctuations of fungi in the water of a creek draining 1800 ha of marsh were examined in relation to total microbial biomass (measured as adenosine 5′-triphosphate (ATP)), temperature, salinity, total volatile material (TVM), total fixed solids (TFS), and particulate organic carbon (POC). Synoptic samples were taken periodically over 10 h from 12 sites within a 320-m transect. Fungi were found to fluctuate out of phase with the tide, with high values observed at low tide and low values obtained at high tide. Similar patterns of fluctuation were obtained for TVM and POC. TFS and ATP were found to fluctuate in phase with the tide. Temperature and salinity showed very little fluctuation over the study period. Statistical analysis (Pearson's r) revealed a significant positive association between fungi and both measures of suspended organic material, TVM and POC. Conversely, significant negative correlations were found between fungi and both TFS and ATP. These data suggest that fungi are attached to particulate organic material and resuspended in the water column by ebbing tides.

Rate of resonant two-photon ionization in the presence of a partially coherent radiation field

A treatment is given of two-photon ionization in which particular attention is paid to the influence of the bandwidth of the ionizing light on the ionization rate. The model adopted for the atom is a common one, including two bound levels and a continuum. The model of the laser is general enough to allow short-term temporal fluctuations of amplitude or phase, and these fluctuations give rise to the laser bandwidth. It is found that the fluctuations have the most interesting effects on the ionization rate when the laser coherence time is shorter than the atomic memory time, as could be expected. In addition to laser bandwidth, we consider the influence on the ionization rate of the detuning of the laser from the intermediate-state resonance, the laser power, and the finite lifetime of the intermediate state. Comparisons with related earlier calculations are made and similarities and differences are pointed out.