bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of ovarian sex hormones and downhill running on fiber-type-specific HSP70 expression in rat soleus
Authors: Bombardier E. , Vigna C. , Iqbal S. , Tiidus P. M. , Tupling A. R.
Published: April 2009

This study examined the influence of the ovarian sex hormones, estrogen and progesterone, on the fiber-type-specific response of the inducible 70-kDa heat shock protein (HSP70) to damaging exercise in rat soleus. Ovariectomized female rats were divided into three treatment groups ( n = 16 per group): sham (S), progesterone (P; 25 mg pellet), and estrogen (E; 0.25 mg pellet). Each treatment group was divided into control and exercised groups. After 8 days of sham or hormone treatment, animals ran downhill intermittently for 90 min (17 m/min, −13.5° grade) on a treadmill, and soleus muscles were removed 24 h postexercise. HSP70 expression was assessed in whole muscle homogenates by Western blotting and in individual muscle fiber types by immunohistochemical analysis of serial cross sections of soleus samples. Comparisons between control groups showed that HSP70 expression in soleus was increased ( P < 0.05) in E compared with both S and P. No difference ( P > 0.05) was observed between S and P. Following downhill running, HSP70 content in soleus was increased ( P < 0.05) compared with control in S and P, but not ( P > 0.05) in E. As a result, soleus HSP70 content following downhill running was not different ( P > 0.05) between any of the treatment groups. Under all conditions, HSP70 content was higher in type I vs. type II fibers, and the effects of both estrogen and exercise on HSP70 expression in soleus were also more pronounced in type I vs. type II fibers. These results demonstrate that 1) estrogen regulates HSP70 expression in skeletal muscle, increasing basal HSP70 expression and preventing further increases in HSP70 in response to exercise; 2) progesterone is not involved in the regulation of HSP70 expression in skeletal muscle; and 3) the effects of estrogen and exercise on HSP70 expression in skeletal muscle are fiber type specific.
Spontaneous Activity of Auditory Nerve Fibers in the Barn Owl (Tyto alba): Analyses of Interspike Interval Distributions
Authors: Neubauer Heinrich , Köppl Christine , Heil Peter
Published: April 2009

In vertebrate auditory systems, the conversion from graded receptor potentials across the hair-cell membrane into stochastic spike trains of the auditory nerve (AN) fibers is performed by ribbon synapses. The statistics underlying this process constrain auditory coding but are not precisely known. Here, we examine the distributions of interspike intervals (ISIs) from spontaneous activity of AN fibers of the barn owl ( Tyto alba), a nocturnal avian predator whose auditory system is specialized for precise temporal coding. The spontaneous activity of AN fibers, with the exception of those showing preferred intervals, is commonly thought to result from excitatory events generated by a homogeneous Poisson point process, which lead to spikes unless the fiber is refractory. We show that the ISI distributions in the owl are better explained as resulting from the action of a brief refractory period (∼0.5 ms) on excitatory events generated by a homogeneous stochastic process where the distribution of interevent intervals is a mixture of an exponential and a gamma distribution with shape factor 2, both with the same scaling parameter. The same model was previously shown to apply to AN fibers in the cat. However, the mean proportions of exponentially versus gamma-distributed intervals in the mixture were different for cat and owl. Furthermore, those proportions were constant across fibers in the cat, whereas they covaried with mean spontaneous rate and with characteristic frequency in the owl. We hypothesize that in birds, unlike in mammals, more than one ribbon may provide excitation to most fibers, accounting for the different proportions, and that variation in the number of ribbons may underlie the variation in the proportions.
Analyzing Variability in Neural Responses to Complex Natural Sounds in the Awake Songbird
Authors: Graña Gilberto David , Billimoria Cyrus P. , Sen Kamal
Published: April 2009

Studies of auditory processing in awake, behaving songbirds allow for the possibility of new classes of experiments, including those involving attention and plasticity. Detecting and determining the significance of plasticity, however, requires assessing the intrinsic variability in neural responses. Effects such as rapid plasticity have been investigated in the auditory system through the use of the spectrotemporal receptive field (STRF), a characterization of the properties of sounds to which a neuron best responds. Here we investigated neural response variability in awake recordings obtained from zebra finch field L, the analog of the primary auditory cortex. To quantify the level of variability in the neural recordings, we used three similarity measures: an STRF-based metric, a spike-train correlation-based metric, and a spike-train discrimination-based metric. We then extracted a number of parameters from these measures, quantifying how they fluctuated over time. Our results indicate that 1) awake responses are quite stable over time; 2) the different measures of response are complementary—specifically, the spike-train–based measures yield new information complementary to the STRF; and 3) different STRF parameters show distinct levels of variability. These results provide critical constraints for the design of robust decoding strategies and novel experiments on attention and plasticity in the awake songbird.
Direction and Contrast Tuning of Macaque MSTd Neurons During Saccades
Authors: Crowder Nathan A. , Price Nicholas S. C. , Mustari Michael J. , Ibbotson Michael R.
Published: April 2009

Saccades are rapid eye movements that change the direction of gaze, although the full-field image motion associated with these movements is rarely perceived. The attenuation of visual perception during saccades is referred to as saccadic suppression. The mechanisms that produce saccadic suppression are not well understood. We recorded from neurons in the dorsal medial superior temporal area (MSTd) of alert macaque monkeys and compared the neural responses produced by the retinal slip associated with saccades (active motion) to responses evoked by identical motion presented during fixation (passive motion). We provide evidence for a neural correlate of saccadic suppression and expand on two contentious results from previous studies. First, we confirm the finding that some neurons in MSTd reverse their preferred direction during saccades. We quantify this effect by calculating changes in direction tuning index for a large cell population. Second, it has been noted that neural activity associated with saccades can arrive in the parietal cortex ≤30 ms earlier than activity produced by similar visual stimulation during fixation. This led to the question of whether the saccade-related responses were visual in origin or were motor signals arising from saccade-planning areas of the brain. By comparing the responses to saccades made over textured backgrounds of different contrasts, we provide strong evidence that saccade-related responses were visual in origin. Refinements of the possible models of saccadic suppression are discussed.
Intrinsic Factors Influencing the Infection by Helminth Parasites in Horses under an Oceanic Climate Area (NW Spain)
Authors: Francisco I. , Arias M. , Cortiñas F. J. , Francisco R. , Mochales E. , Dacal V. , Suárez J. L. , Uriarte J. , Morrondo P. , Sánchez-Andrade R. , Díez-Baños P. , Paz-Silva A.
Published: April 2009

A coprological survey to determine the influence of some intrinsic factors (breed, age, and sex) on the infection by helminth parasites in equine livestock (n=418) under an oceanic climate area (NW Spain) was conducted. Faecal samples were individually collected and analyzed by the coprological techniques. The main strongylid genera identified wereTrichonemaandCyalocephalusspp (small strongyles) andStrongylusandTriodontophorus(large strongyles). The prevalence of gastrointestinal nematode was 89% (95% CI 86, 92) and 1% cestoda (0, 2). The percentage of horses with strongyloid parasites was 89% (86, 92), 11% (8, 14) forParascaris, and 3% (1, 5) forOxyuris. The highest prevalence for ascariosis was observed in the youngest horses (<3 years), for oxyurosis in the >10 years animals, and for strongylosis in the 3–10 years ones. Females were significantly more parasitized than males. A negative correlation between the age and the egg-excretion of ascarids and strongyles was recorded. The autochthonous and the English Pure Blood horses were the most parasitized. We concluded that the infections by helminths, especially the strongyloids, are significantly common in the region, so that greater importance should be given to this situation.
Contemplative Practice and Textual Agency in Advaita Vedānta
Authors: Dalal Neil
Published: April 2009

Advaita Vedāntins consider contemplative practice (nididhyāsana) as one of the primary practices for gaining self-knowledge and liberation. However, the nature of contemplative practice is both ambiguous and contested. How do Advaita Vedānta practitioners actually engage this contemplative process? What are the relationships between contemplative practice, scriptural study, and liberating experience? This paper explores the nature of contemplative practice based on fieldwork with contemporary Advaita Vedānta monks from the Arsha Vidya Gurukulam.
The Tie that Binds: Connecting Biography and Ethnography
Authors: Raj Selva
Published: April 2009

The author explores his transformation from religious practitioner to ethnographer and the responses he received from academic colleagues, religious colleagues, and laypeople and the ethical challenges such responses posed. He then suggests that the scholar's performance of ethnography can be understood through a classical Hindu schema of the life cycle.
How Does One Study a “Masterpiece of the Oral and Intangible Heritage of Humanity”? Ethnographic Reflections on Kerala's Kūtiyāttam
Authors: Sullivan Bruce
Published: April 2009

This article presents issues encountered in ethnographic fieldwork in Kerala, south India, on a tradition of Sanskrit theatre called Kūtiyāttam. Key issues include recent changes in both the audience and performing troupes as Kerala's society has become more egalitarian, and reduced ritual activity by priests. Kūtiyāttam has been transformed from a devotional offering in temples to a cultural performance viewed as an art form. Ethnographic research on this tradition has contributed to international recognition and patronage. In this case, ethnographic fieldwork affects both the researchers and the subjects of their research.
On the Algorithms Used to Compute the Standard Deviation of Wind Direction
Authors: Farrugia Pierre S. , Borg James L. , Micallef Alfred
Published: April 2009

The standard deviation of wind direction is a very important quantity in meteorology because in addition to being used to determine the dry deposition rate and the atmospheric stability class, it is also employed in the determination of the rate of horizontal diffusion, which in turn determines transport and dispersion of air pollutants. However, the computation of this quantity is rendered difficult by the fact that the horizontal wind direction is a circular variable having a discontinuity at 2π radians, beyond which the wind direction starts again from zero, thus preventing angular subtraction from being a straightforward procedure. In view of such a limitation, this work is meant to provide new mathematical expressions that simplify both the computational and analytical work involved in handling the standard deviation of wind direction. This is achieved by deriving a number of Fourier series and Taylor expansions that can represent the minimum angular distance and its powers. Using these expressions, the relation between two algorithms commonly used to determine the standard deviation of wind direction is analyzed. Furthermore, given that these trigonometric expansions effectively reduce the mathematical complexity involved when dealing with circular statistics, their potential application to solve other problems is discussed.
A Combination of Cluster Analysis and Kappa Statistic for the Evaluation of Climate Model Results
Authors: Kücken Martin , Gerstengarbe Friedrich-Wilhelm , Orlowsky Boris
Published: April 2009

The authors present a combination of different statistical methods for the validation of climate simulation data with respect to observational data of the same spatial and temporal coverage. It is assumed that simulated data and observed data are both given as time series at locations such as grid cells or station locations. The aim of this approach is to quantify the agreement between the two spatial structures of observed and simulated data. These spatial structures consist of the spatial distributions of clusters (obtained from a cluster analysis) that contain climatologically similar locations. If the spatial distribution of clusters were identical for the observed and the simulated data, the simulation would describe the spatial structure of the observations perfectly. Differences from this ideal situation can be objectively quantified using the κ statistic. If the simulation data have shortcomings, the different κ variants can be used to diagnose where these are located. The method is demonstrated using simulation data from the Statistical Regional Model (STAR) for Germany. The combination of cluster analysis and κ statistic proves to be an excellent tool for quantifying the spatial correctness of climate models that can be extended to multimodel comparisons. It can thereby serve as a standard measure for climate model evaluation.
The Mesoscale Dynamics of Thin Tropical Tropopause Cirrus
Authors: Durran Dale R. , Dinh Tra , Ammerman Marie , Ackerman Thomas
Published: April 2009

Thin cirrus clouds in the tropical tropopause layer (TTL) are warmed through the absorption of infrared radiation. The response of the cloud and the surrounding atmosphere to this thermal forcing is investigated through linear theory and nonlinear numerical simulation. Linear solutions for the circulations forced by a fixed heat source representative of TTL cirrus clouds show ascent in the region of the heating, accompanied by horizontal flow toward the heat source at the base of the heated layer and horizontal outflow at the top of the layer. Gravity waves propagate positive temperature perturbations well beyond the lateral edges of the heated region. Cool layers that also spread horizontally are produced immediately above and below the heated region.

Numerical simulations with a cloud-resolving model allow the radiative heating to change in response to the redistribution of the cloud by the evolving velocity field. The basic atmospheric response in the numerical simulations is nevertheless similar to that generated by the fixed heat source. In the numerical simulations, the advection of ice crystals by the radiatively forced velocity field also lofts the cloud, while horizontally spreading its top and narrowing its base. Ice crystal sedimentation is neglected in these calculations, but it appears that the radiatively induced upward vertical velocities are likely strong enough to maintain clouds consisting of very small crystals (radii less than 4 μm) against sedimentation for many hours.
Relative Roles of Land–Sea Distribution and Orography in Asian Monsoon Intensity
Authors: Xu Zhongfeng , Fu Congbin , Qian Yongfu
Published: April 2009

The relative impacts of various land–sea distributions (LSDs) and mountains on Asian monsoon extent and intensity are assessed using a series of AGCM simulations. The air–sea coupling effects are not considered in this study. All simulations were integrated with zonal mean SST, globally uniform vegetation, soil color, and, except several simulations, soil texture. The results show that the LSD plays a more fundamental role than orography in determining the extent of Asian and African monsoons. The tropical zonal LSD and Asian mountains both play a crucial role for establishing summer monsoon convection over the South Asian region. The monsoon circulation index (MCI1) defined by the difference of zonal wind between 850 and 200 hPa is used to measure the intensity of the South Asian summer monsoon. The large-scale meridional land–sea thermal contrast between the Eurasian continent and the Indian Ocean only induces a 1.8 m s−1 increase of MCI1. The presence of the Indian subcontinent and Indochina peninsula (Asian mountains), however, induces a 6.6 (7.4) m s−1 increase of MCI1 associated with the release of latent heat of condensation. Clearly, the tropical subcontinental-scale zonal LSD and the Asian mountains almost equally contribute to the increase of MCI1 and play a more important role than the large-scale meridional LSD between the Eurasian continent and the Indian Ocean. Possible mechanisms of how the tropical subcontinental-scale zonal LSD and Asian mountains impact the Asian summer monsoon circulation and precipitation are also discussed.
Cross-Frequency Coupling, Skewness, and Blocking in the Northern Hemisphere Winter Circulation
Authors: Rennert Kevin J. , Wallace John M.
Published: April 2009

Variability in daily wintertime [December–February (DJF)] 500-hPa heights on low [L: <(30 day)−1], intermediate [M: (6–30 day)−1], and high [H: >(6 day)−1] frequencies is examined using 40-yr ECMWF Re-Analysis (ERA-40) data. Leading EOFs of L correspond to planetary-scale teleconnection patterns; those of M to retrograding, eastward-dispersing long waves oriented along great circle routes; and those of H to baroclinic waves in the climatological-mean storm tracks. In the Atlantic sector, EOF 1 of M appears to be embedded in EOF 1 of L.

Cross-frequency coupling between L and M exhibits distinctive patterns. In the Atlantic sector the negative polarity of the North Atlantic Oscillation (NAO) with above-normal heights over Greenland is associated with enhanced M variability over Greenland. An analogous relationship is observed in the Pacific sector between an NAO-like pattern and the variance of M over Alaska. Cross-frequency coupling between L and H in both sectors is indicative of a reinforcement of the background flow by the baroclinic waves. Cross-frequency coupling between L and M is responsible for most of the skewness of the anomalies in the 500-hPa height field.

Linear wave dynamics evidently play an important role in M. Composites of high amplitude anomalies of contrasting signs over Baffin Bay exhibit similar spatial structures (apart from the sign reversal) and they exhibit a similar evolution, with westward phase propagation and downstream development characteristic of the behavior of Rossby waves. It is argued that teleconnection patterns exhibit memories much longer than the 7–10-day decorrelation time of daily indices formed by projecting unfiltered daily fields onto their spatial patterns.
Coupled Climate Simulation by Constraining Ocean Fields in a Coupled Model with Ocean Data
Authors: Fujii Yosuke , Nakaegawa Toshiyuki , Matsumoto Satoshi , Yasuda Tamaki , Yamanaka Goro , Kamachi Masafumi
Published: April 2009

The authors developed a system for simulating climate variation by constraining the ocean component of a coupled atmosphere–ocean general circulation model (CGCM) through ocean data assimilation and conducted a climate simulation [Multivariate Ocean Variational Estimation System–Coupled Version Reanalysis (MOVE-C RA)]. The monthly variation of sea surface temperature (SST) is reasonably recovered in MOVE-C RA. Furthermore, MOVE-C RA has improved precipitation fields over the Atmospheric Model Intercomparison Project (AMIP) run (a simulation of the atmosphere model forced by observed daily SST) and the CGCM free simulation run. In particular, precipitation in the Philippine Sea in summer is improved over the AMIP run. This improvement is assumed to stem from the reproduction of the interaction between SST and precipitation, indicated by the lag of the precipitation change behind SST. Enhanced (suppressed) convection tends to induce an SST drop (rise) because of cloud cover and ocean mixing in the real world. A lack of this interaction in the AMIP run leads to overestimating the precipitation in the Bay of Bengal in summer. Because it is recovered in MOVE-C RA, the overestimate is suppressed. This intensifies the zonal Walker circulation and the monsoon trough, resulting in enhanced convection in the Philippine Sea. The spurious positive correlation between SST and precipitation around the Philippines in the AMIP run in summer is also removed in MOVE-C RA. These improvements demonstrate the effectiveness of simulating ocean interior processes with the ocean model and data assimilation for reproducing the climate variability.
Analysis of the Relationship of U.S. Droughts with SST and Soil Moisture: Distinguishing the Time Scale of Droughts
Authors: Wu Renguang , Kinter James L.
Published: April 2009

The impacts of droughts depend on how long droughts persist and the reasons why droughts extend to different time scales may be different. The present study distinguishes the time scale of droughts based on the standardized precipitation index and analyzes the relationship of boreal summer U.S. droughts with sea surface temperature (SST) and soil moisture. It is found that the roles of remote SST forcing and local soil moisture differ significantly for long-term and short-term droughts in the U.S. Great Plains and Southwest. For short-term droughts (≤3 months), simultaneous remote SST forcing plays an important role with an additional contribution from soil moisture. For medium-term and long-term droughts (≥6 months), both simultaneous and antecedent SST forcing contribute to droughts, and the soil moisture is important for the persistence of droughts through a positive feedback to precipitation. The antecedent remote SST forcing contributes to droughts through soil moisture and evaporation changes. The tropical Pacific SST is the dominant remote forcing for U.S. droughts. The most notable impacts of the tropical Pacific SST are found in the Southwest with extensions to the Great Plains. Tropical Indian Ocean SST forcing has a notable influence on medium-term and long-term U.S. droughts. The relationships between tropical Indian and Pacific Ocean SST and boreal summer U.S. droughts have undergone obvious long-term changes, especially for the Great Plains droughts.
Intraseasonal Latent Heat Flux Based on Satellite Observations
Authors: Grodsky Semyon A. , Bentamy Abderrahim , Carton James A. , Pinker Rachel T.
Published: April 2009

Weekly average satellite-based estimates of latent heat flux (LHTFL) are used to characterize spatial patterns and temporal variability in the intraseasonal band (periods shorter than 3 months). As expected, the major portion of intraseasonal variability of LHTFL is due to winds, but spatial variability of humidity and SST are also important. The strongest intraseasonal variability of LHTFL is observed at the midlatitudes. It weakens toward the equator, reflecting weak variance of intraseasonal winds at low latitudes. It also decreases at high latitudes, reflecting the effect of decreased SST and the related decrease of time-mean humidity difference between heights z = 10 m and z = 0 m. Within the midlatitude belts the intraseasonal variability of LHTFL is locally stronger (up to 50 W m−2) in regions of major SST fronts (like the Gulf Stream and Agulhas). Here it is forced by passing storms and is locally amplified by unstable air over warm SSTs. Although weaker in amplitude (but still significant), intraseasonal variability of LHTFL is observed in the tropical Indian and Pacific Oceans due to wind and humidity perturbations produced by the Madden–Julian oscillations. In this tropical region intraseasonal LHTFL and incoming solar radiation vary out of phase so that evaporation increases just below the convective clusters.

Over much of the interior ocean where the surface heat flux dominates the ocean mixed layer heat budget, intraseasonal SST cools in response to anomalously strong upward intraseasonal LHTFL. This response varies geographically, in part because of geographic variations of mixed layer depth and the resulting variations in thermal inertia. In contrast, in the eastern tropical Pacific and Atlantic cold tongue regions intraseasonal SST and LHTFL are positively correlated. This surprising result occurs because in these equatorial upwelling areas SST is controlled by advection rather than by surface fluxes. Here LHTFL responds to rather than drives SST.
Climate Response of the Equatorial Pacific to Global Warming
Authors: DiNezio Pedro N. , Clement Amy C. , Vecchi Gabriel A. , Soden Brian J. , Kirtman Benjamin P. , Lee Sang-Ki
Published: April 2009

The climate response of the equatorial Pacific to increased greenhouse gases is investigated using numerical experiments from 11 climate models participating in the Intergovernmental Panel on Climate Change’s Fourth Assessment Report. Multimodel mean climate responses to CO2 doubling are identified and related to changes in the heat budget of the surface layer. Weaker ocean surface currents driven by a slowing down of the Walker circulation reduce ocean dynamical cooling throughout the equatorial Pacific. The combined anomalous ocean dynamical plus radiative heating from CO2 is balanced by different processes in the western and eastern basins: Cloud cover feedbacks and evaporation balance the heating over the warm pool, while increased cooling by ocean vertical heat transport balances the warming over the cold tongue. This increased cooling by vertical ocean heat transport arises from increased near-surface thermal stratification, despite a reduction in vertical velocity. The stratification response is found to be a permanent feature of the equilibrium climate potentially linked to both thermodynamical and dynamical changes within the equatorial Pacific. Briefly stated, ocean dynamical changes act to reduce (enhance) the net heating in the east (west). This explains why the models simulate enhanced equatorial warming, rather than El Niño–like warming, in response to a weaker Walker circulation. To conclude, the implications for detecting these signals in the modern observational record are discussed.
A Statistical Methodology to Discover Precipitation Microclimates in Southeast Louisiana: Implications for Coastal Watersheds*
Authors: Van Cooten Suzanne , Elmore Kimberly L. , Barbé Donald E. , McCorquodale J. Alex , Reed Denise J.
Published: April 2009

This study quantifies the spatial distribution of precipitation patterns on an annual basis for southeast Louisiana. To compile a long-term record of 24-h rainfall, rainfall reports collected by National Weather Service (NWS) cooperative observers were gathered from National Climatic Data Center (NCDC) archives, private collections of observational data held at regional and local libraries, NWS offices, and local utility providers. The reports were placed into a digital database in which each station’s record was subjected to an extensive quality control process. This process produced a database of daily rainfall reports for 59 south Louisiana stations for the period 1836–2002, with extensive documentation for each site outlining the differences between the study’s data and the data available from the NCDC Web page. A statistical methodology was developed to determine if the four NCDC climate divisions for southeast Louisiana accurately depict average monthly rainfall for the area. This method employs cluster analysis, using Euclidean distance as the measure of dissimilarity for the clustering technique. To resolve missing rainfall observations, an imputation scheme was developed that uses the two most similar stations (based on Euclidean distance) to determine appropriate values for missing rainfall observations. Results from this testing structure show statistical evidence of precipitation microclimates across south Louisiana at higher spatial scales than those of the NCDC climate zones. Quantifying the spatial extent of daily precipitation and documenting historical trends of precipitation provides critical design information for regional infrastructure within this highly vulnerable area of the central Gulf Coast region.
Lagrangian Analysis of the Meridional Overturning Circulation in an Idealized Ocean Basin
Authors: Van Roekel Luke P. , Ito Taka , Haertel Patrick T. , Randall David A.
Published: April 2009

The Lagrangian ocean model is used as a tool to simulate the response of the basin-scale overturning circulation to spatially variable diapycnal mixing in an idealized ocean basin. The model explicitly calculates the positions, velocities, and tracer properties of water parcels. Owing to its Lagrangian formulation, numerical diffusion is completely eliminated and water parcel pathways and water mass ages can be quantified within the framework of the discrete, advective transit time distribution. To illustrate the ventilation pathways, simulated trajectories were tracked backward in time from the interior ocean to the surface mixed layer where the water parcel was last in contact with the atmosphere. This new diagnostic has been applied to examine the response of the meridional overturning circulation to highly localized diapycnal mixing through sensitivity experiments. In particular, the focus is on three simulations: the first holds vertical diffusivity uniform; in the second, the vertical diffusivity is confined within an equatorial box; and the third simulation has a diffusivity pattern based on idealized hurricane-induced mixing. Domain-integrated deep ventilation rates and heat transport are similar between the first two cases. However, locally enhanced mixing yields about 30% younger water mass age in the tropical thermocline due to intense localized upwelling. In the third simulation, a slower ventilation rate of deep waters is found to be due to the lack of abyssal mixing. These results are interpreted using the classical theories of abyssal circulation, highlighting the strong sensitivity of the ventilation pathways to the spatial distribution of diapycnal mixing.
Can a Unique Model Describe the Raindrop Shape–Size Relation? A Clue from Polarimetric Radar Measurements
Authors: Gorgucci Eugenio , Chandrasekar V. , Baldini Luca
Published: April 2009

A method is proposed to retrieve raindrop shape–size relations from the radar measurements of reflectivity factor Zh, differential reflectivity Zdr, and specific differential phase Kdp at S band. This procedure is obtained using a domain defined by the two variables Kdp/Zh and Zdr where the drop size distribution (DSD) variability is collapsed onto a line and any variation is essentially due to the drop shape variability. To obtain information on the raindrop shape–size relation underlying a set of radar observations, this domain is studied in conjunction with another domain describing the relation between the drop axial ratio (or shape) and its equivolumetric diameter. Using an initial drop shape and choosing a set of DSDs described by a normalized gamma model, polarimetric radar measurements are produced by simulation. An averaged curve of Kdp/Zh versus Zdr is obtained and compared with the same curve obtained from the radar data. By changing the initial axial ratio relation, a procedure of minimization between the two curves is developed to derive the underlying drop shape–size relation governing the radar measurements under consideration. Three sets of radar data collected in different climatic regions are analyzed to evaluate whether there is a unique shape–size relation.
A Quantum Cascade Laser–Based Reflectometer for On-Orbit Blackbody Cavity Monitoring
Authors: Gero P. Jonathan , Dykema John A. , Anderson James G.
Published: April 2009

Satellite measurements pinned to international standards are needed to monitor the earth’s climate, quantify human influence thereon, and test forecasts of future climate change. Credible observations require that measurement uncertainties be evaluated on orbit during a mission’s operational lifetime. The most accurate spaceborne measurements of thermal infrared radiance are achieved with blackbody calibration. The physical properties of blackbody cavity surface coatings are known to change upon extended exposure to the low earth orbit environment. Any such drift must be quantified to continue correctly calibrating observed radiance on orbit. A method is presented to diagnose the effective emissivity of a blackbody cavity in situ using a quantum cascade laser (QCL)-based reflectometer. QCLs provide high-power single-mode output in the thermal infrared and have small mechanical footprints that facilitate integration into existing optical systems. The laser reflectivity in a test blackbody cavity was measured to be 9.22 × 10−4 with an uncertainty of 8.9 × 10−5, which is equivalent to a detection limit of 3 mK in the error in radiance temperature for a calibration blackbody (at 330 K and 1000 cm−1) resulting from cavity emissivity drift. These results provide the experimental foundation for this technology to be implemented on satellite instruments and thus eliminate a key time-dependent systematic error from future measurements on orbit.
Semiautonomous FTS Observation System for Remote Sensing of Stratospheric and Tropospheric Gases
Authors: Hannigan James W. , Coffey Michael T. , Goldman Aaron
Published: April 2009

A solar-viewing Fourier transform spectrometer (FTS) at Thule, Greenland (76.5°N, 68.8°W, 225 m MSL), has been in operation as part of the Network for the Detection of Atmospheric Composition Change [NDACC; formerly the Network for the Detection of Stratospheric Change (NDSC)] since 1999. Observations have been made, on average, 77 days yr−1 during the 8 months, excluding polar night. The semiautonomous operation of the instrument, including its associated optical, cryogenic, and control systems, is of primary importance to acquiring long-term data records efficiently and is herein described. Discussed in this paper are the data processing and spectra analysis methodology that are used to convert the measured interferograms into geophysical data products. Vertical profile retrievals derived from the high-resolution solar absorption spectra use the optimal estimation method. Total column amounts then represent the integration of these vertical profiles. As an example of this process, results are presented for daily average total column amounts of HF, HCl, ClONO2, and CCl2F2 from 2001 through 2007. The means of unperturbed summertime observations are used in a preliminary study of their annual trends.
The Impact of Lightning Data Assimilation on a Winter Storm Simulation over the North Pacific Ocean
Authors: Pessi Antti T. , Businger Steven
Published: April 2009

In this paper, the potential of lightning data assimilation to improve NWP forecasts over data-sparse oceans is investigated using, for the first time, a continuous, calibrated lightning data stream. The lightning data employed in this study are from the Pacific Lightning Detection Network/Long-Range Lightning Detection Network (PacNet/LLDN), which has been calibrated for detection efficiency and location accuracy. The method utilizes an empirical lightning–convective rainfall relationship, derived specifically from North Pacific winter storms observed by PacNet/LLDN. The assimilation method nudges the model’s latent heating rates according to rainfall estimates derived from PacNet/LLDN lightning observations. The experiment was designed to be employed in an operational setting. To illustrate the promise of the approach, lightning data from a notable extratropical storm that occurred over the northeast Pacific Ocean in late December 2002 were assimilated into the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5). The storm exhibited a very electrically active cold front with most of the lightning observed 300–1200 km away from the storm center. The storm deepened rapidly (12 hPa in 12 h) and was poorly forecast by the operational models. The assimilation of lightning data generally improved the pressure and wind forecasts, as the validation of the model results using available surface and satellite data revealed. An analysis is presented to illustrate the impact of assimilation of frontal lightning on the storm development and dynamics. The links among deep convection, thermal wind along the front, and cyclogenesis are explicitly explored.
Chemical Source Inversion Using Assimilated Constituent Observations in an Idealized Two-Dimensional System
Authors: Tangborn Andrew , Cooper Robert , Pawson Steven , Sun Zhibin
Published: April 2009

A source inversion technique for chemical constituents is presented that uses assimilated constituent observations rather than directly using the observations. The method is tested with a simple model problem, which is a two-dimensional Fourier–Galerkin transport model combined with a Kalman filter for data assimilation. Inversion is carried out using a Green’s function method and observations are simulated from a true state with added Gaussian noise. The forecast state uses the same spectral model but differs by an unbiased Gaussian model error and emissions models with constant errors. The numerical experiments employ both simulated in situ and satellite observation networks. Source inversion was carried out either by directly using synthetically generated observations with added noise or by first assimilating the observations and using the analyses to extract observations. Twenty identical twin experiments were conducted for each set of source and observation configurations, and it was found that in the limiting cases of a very few localized observations or an extremely large observation network there is little advantage to carrying out assimilation first. For intermediate observation densities, the source inversion error standard deviation is decreased by 50% to 90% when the observations are assimilated with the Kalman filter before carrying out the Green’s function inversion.
Effect of the Andes Cordillera on Precipitation from a Midlatitude Cold Front
Authors: Barrett Bradford S. , Garreaud RenéD. , Falvey Mark
Published: April 2009

The effects of the Andes Cordillera, the major mountain range in South America, on precipitation patterns of baroclinic systems approaching from the southeast Pacific remain largely unstudied. This study focuses on a case in late May 2008 when an upper-level trough and surface cold front produced widespread precipitation in central Chile. The primary goal was to analyze the physical mechanisms responsible for the structure and evolution of the precipitation.

Weather Research and Forecasting (WRF) model simulations indicate that as an upper-level trough approached central Chile, midtropospheric flow below 700 hPa was blocked by the high topography and deflected poleward in the form of a barrier jet. This northerly jet had wind maxima in excess of 15 m s−1, was centered around 925 hPa, and extended westward 200 km from the mountains. It intersected the cold front, which approached from the south near the coast, thereby increasing convergence along the frontal surface, slowing its equatorward progress, and enhancing rainfall over central Chile. Another separate region of heavy precipitation formed over the upwind slopes of the cordillera. A trajectory analysis confirmed that the barrier jet moved low-level parcels from their origin in the moist southeast Pacific boundary layer to the coast. When model topography was reduced to twenty percent of its original height, the cold front advanced more rapidly to the northeast, generated less precipitation in central Chile between 33° and 36°S, and produced minimal orographic precipitation on the upwind Andean slopes. Based on these findings, the high topography appears responsible for not only orographic precipitation but also for substantially increasing precipitation totals over the central coast and valley.
Difficulties with Correcting Radar Rainfall Estimates Based on Rain Gauge Data: A Case Study of Severe Weather in Montana on 16–17 June 2007
Authors: Vasiloff Steven V. , Howard Kenneth W. , Zhang Jian
Published: April 2009

The principal source of information for operational flash flood monitoring and warning issuance is weather radar–based quantitative estimates of precipitation. Rain gauges are considered truth for the purposes of validating and calibrating real-time radar-derived precipitation data, both in a real-time sense and climatologically. This paper examines various uncertainties and challenges involved with using radar and rain gauge data in a severe local storm environment. A series of severe thunderstorm systems that occurred across northeastern Montana illustrates various problems with comparing radar precipitation estimates and real-time gauge data, including extreme wind effects, hail, missing gauge data, and radar quality control. Ten radar–gauge time series pairs were analyzed with most found to be not useful for real-time radar calibration. These issues must be carefully considered within the context of ongoing efforts to develop robust real-time tools for evaluating radar–gauge uncertainties. Recommendations are made for radar and gauge data quality control efforts that would benefit the operational use of gauge data.
Skill of a Ceiling and Visibility Local Ensemble Prediction System (LEPS) according to Fog-Type Prediction at Paris-Charles de Gaulle Airport
Authors: Roquelaure Stevie , Tardif Robert , Remy Samuel , Bergot Thierry
Published: April 2009

A specific event, called a low-visibility procedure (LVP), has been defined when visibility is under 600 m and/or the ceiling is under 60 m at Paris-Charles de Gaulle Airport, Paris, France, to ensure air traffic safety and to reduce the economic issues related to poor visibility conditions. The Local Ensemble Prediction System (LEPS) has been designed to estimate LVP likelihood in order to help forecasters in their tasks. This work evaluates the skill of LEPS for each type of LVP that takes place at the airport area during five winter seasons from 2002 to 2007. An event-based classification reveals that stratus base lowering, advection, and radiation fogs make up for 78% of the LVP cases that occurred near the airport during this period. This study also demonstrates that LEPS is skillful on these types of event for short-term forecasts. When the ensemble runs start with initialized LVP events, the prediction of advection fogs is as skillful as the prediction of radiation fog events and stratus base lowering. At 3 and 6 h before the runs where LVP events were initialized, LEPS still shows positive skill for radiation fog events and stratus base lowering cases.
Influences of Resource Limitations and Transmission Costs on Epidemic Simulations and Critical Thresholds in Scale-Free Networks
Authors: Huang Chung-Yuan , Tsai Yu-Shiuan , Sun Chuen-Tsai , Hsieh Ji-Lung , Cheng Chia-Ying
Published: April 2009

Critical thresholds represent one of the most important diffusion indicators of epidemic outbreaks. However, we believe that recent studies have overemphasized ways that the power-law connectivity distribution features of social networks affect epidemic dynamics and critical thresholds. As a result, two important factors have been overlooked: resource limitations and transmission costs associated with social interactions and daily contact. Here we present our results from the simultaneous application of mean-field theory and an agent-based network simulation approach for analyzing the effects of resources and costs on epidemic dynamics and critical thresholds. Our main findings are: (a) a significant critical threshold does exist when resources and costs are taken into consideration, and it has a lower bound whenever contagion events occur in scale-free networks; (b) when transmission costs increase or individual resources decrease, critical contagion thresholds in scale-free networks grow linearly and steady density curves shrink linearly; (c) regardless of whether the resources of individuals obey delta, uniform, or normal distributions, they have the same critical thresholds and epidemic dynamics as long as the average value of usable resources remains the same across different scale-free networks; and (d) the spread of epidemics in scale-free networks remains controllable as long as resources are properly restricted and intervention strategy investments are significantly increased.
Bullying in Middle School as a Function of Insecure Attachment and Aggressive Attitudes
Authors: Eliot Megan , Cornell Dewey G.
Published: April 2009

This study tested a model for understanding peer bullying as the product of aggressive attitudes and insecure attachment. A sample of 110 sixth grade students completed self-report measures that assessed attitudes toward the use of aggressive behaviour with peers and distinguished secure from insecure parental attachment. Bullying behaviour was assessed using self- and peer-report. Path analyses indicated that aggressive attitudes mediated a relationship between insecure attachment and bullying behaviour. These findings have theoretical and applied implications for bullying prevention.
Stability and Change in Patterns of Peer Rejection
Authors: Greenman Paul S. , Schneider Barry H. , Tomada Giovanna
Published: April 2009

Poor school adjustment is a known correlate of peer rejection in childhood. However, the impact of change in sociometric status on children's academic performance over time is unclear. The aim of this study was to determine whether improvement or decline in children's sociometric status would predict corresponding changes in their academic performance trajectories. Two hundred and seventy-two boys and 252 girls in Florence, Italy (mean age at Time 1: 7.42 years) and their teachers participated in this 18-month investigation. Hierarchical linear models indicated that children who were rejected by their peers across the four measurement points of the study demonstrated consistently worse academic performance than did children who were not rejected throughout, whereas children who were regularly accepted by their peers performed better in school than did their peers who were rejected one or more times. A number of children who became rejected exhibited an academic decline, but others who became accepted showed improvement. The implications of these results for children, parents, teachers and school administrators are discussed.
Academic and Behaviour Associates of Peer Status for Children in a Caribbean Community Findings from the St Vincent Child Study
Authors: Jimerson Shane R. , Durbrow Eric H. , Wagstaff David A.
Published: April 2009

Studies of peer relations among children living in rural developing communities are rare. This study examined peer status in 168 children (ages 6—12) living in a rural community in a developing community, St Vincent, the West Indies. The present study used ANOVA to test hypotheses about the relations between peer status and academic scores and teacher-ratings of delinquency, learning problems, conduct and sensitivity. Using a peer nomination procedure, children were classified into four groups [i.e. rejected (28), popular (24), average (85), controversial (8) and neglected (23)]. The results of this study revealed that rejected children had significantly lower academic scores than popular children even when learning problems and age were controlled. Unlike children in developed societies, rejected children did not have significantly higher teacher ratings of sensitivity, delinquency and conduct problems. Cultural considerations and future research directions are also discussed.