bluuebunny/crossref_metadata_2025 huggingface dataset:
Similarities and differences between the Brazilian and African counterparts of the Neoproterozoic Araçuaí-West Congo orogen
Authors: Pedrosa-Soares A. C. , Alkmim F. F. , Tack L. , Noce C. M. , Babinski M. , Silva L. C. , Martins-Neto M. A.
Published: January 2008

The Araçuaí–West Congo orogen encompasses orogenic domains located to the SE of the São Francisco Craton in Brazil, and to the SW of the Congo Craton in Africa. From the opening of the precursor basin to the last orogenic processes, the evolution of the orogen lasted from the very beginning of the Neoproterozoic up to the Cambrian–Ordovician boundary. After the spreading of the South Atlantic Ocean in Cretaceous time, the Araçuaí–West Congo orogen was split into two quite different but complementary counterparts. The Brazilian side (Araçuaí orogen) inherited two thirds of the whole orogenic edifice, including all the Neoproterozoic ophiolite slivers, the entire magmatic arc and syn-collisional to post-collisional magmatism, and the suture zone. The African counterpart (West Congo Belt), a fold–thrust belt free of Neoproterozoic ophiolite and Pan-African orogenic magmatism, inherited the thick pile of bimodal volcanic rocks of the Early Tonian rift stage, implying that the precursor basin was an asymmetrical rift with the thermal–magmatic axis located in the West Congo Belt. Both counterparts of the Araçuaí–West Congo orogen include Neoproterozoic glaciogenic deposits, allowing tentative lithostratigraphic correlations, but identification of the ice ages remains uncertain because the lack of sufficient well-constrained geochronological data.
Disorders of Childhood and Adolescence: Gender and Psychopathology
Authors: Zahn-Waxler Carolyn , Shirtcliff Elizabeth A. , Marceau Kristine
Published: January 2008

Early-onset disorders (e.g., conduct problems, autism) show a marked male preponderance, whereas adolescent-onset disorders (e.g., depression, anxiety) show a marked female preponderance. A developmental psychopathology framework provides a means to investigate complex gender-related etiologies of these different disorders. This review focuses on biological and environmental factors implicated in the development of conduct problems and depression in boys and girls. Boys and girls showed certain differences in types, rates, comorbidities, antecedents, correlates, and trajectories of these problems. Origins of male and female preponderant problems are likely to be rooted, in part, in biological, physical, cognitive, and social-emotional differences in boys and girls that can precede the expression of clinical problems. These male-like and female-like characteristics are considered regarding conduct problems and depression to explore how they inform biological and environmental theories about gender and psychopathology. At the same time, because boys and girls also show many similarities, it is important to avoid sex-stereotyping mental health problems.
Cost-Effective Early Childhood Development Programs from Preschool to Third Grade
Authors: Reynolds Arthur J. , Temple Judy A.
Published: January 2008

Although findings on the positive effects of early childhood development programs have been widely disseminated, less attention has been given to program impacts across the entire period of early childhood. This review summarizes evidence on the effects and cost-effectiveness of programs and services from ages 3 to 9. The major focus is preschool programs for 3- and 4-year-olds, full-day kindergarten, school-age programs including reduced class sizes, and preschool-to-third-grade interventions. Participation in preschool programs was found to have relatively large and enduring effects on school achievement and child well-being. High-quality programs for children at risk produce strong economic returns ranging from about $4 per dollar invested to over $10 per dollar invested. Relative to half-day kindergarten, the positive effects of full-day kindergarten have been found to be relatively small and generally do not last for more than a year. Although no formal economic analyses have been conducted, the economic return per dollar invested would be expected to be close to zero. Among early-school-age programs, preschool plus school-age interventions (PK-3) for children at risk are linked to higher levels of school performance into adolescence. The Child-Parent Center PK-3 Program shows a return of $6 to $9 per dollar invested. Class-size reductions show evidence of positive effects, with economic returns of roughly $3 per dollar invested. The causal mechanisms of long-term effects are discussed. Key principles to promote intervention effectiveness are offered.
Modern Approaches to Conceptualizing and Measuring Human Life Stress
Authors: Monroe Scott M.
Published: January 2008

The idea that adverse life circumstances and negative life events contribute to disorder and disease has long been held. Advances in conceptualizing and defining these conditions under the common label of life stress have led to progress in measuring both the environmental and individual response characteristics that may promote disorder and disease. In general, a substantial and growing research literature supports the basic premise that life stress plays an important role in the development of many psychological and physical problems. Recent research, too, strongly suggests that interest in life stress in relation to health and disease will accelerate over the coming years. Yet debates and controversies remain concerning how to best conceptualize and measure life stress, which presents distinctive challenges for advancing the field. The present review examines the major issues pertaining to these debates, controversies, and challenges, for they will be crucial to resolve if progress is to be made in understanding ways in which life stress may or may not contribute to psychological and physical disorders.
Pediatric Bipolar Disorder
Authors: Leibenluft Ellen , Rich Brendan A.
Published: January 2008

In the past decade, interest in and research on pediatric bipolar disorder (BD) has increased substantially. Prevalence rates of the disorder have doubled in outpatient settings, while twice as many research articles on pediatric BD were published in the past five years as in the prior decade. This review focuses on recent developments in the study of pediatric BD. We examine current research on the diagnostic boundaries of BD in youths, in particular the issues of episodicity and irritability, and provide assessment guidelines. We review data elucidating the pathophysiology of pediatric BD, with a focus on how these results may inform diagnosis. Finally, we discuss treatment approaches for pediatric BD, particularly psychotherapeutic interventions. Throughout the review, we pay particular attention to youths with severe chronic irritability, hyperarousal, and hyperreactivity, who reflect the population in whom the diagnosis of BD is most debated.
Human mesenchymal stem cells stimulated by TNF-α, LPS, or hypoxia produce growth factors by an NFκB- but not JNK-dependent mechanism
Authors: Crisostomo Paul R. , Wang Yue , Markel Troy A. , Wang Meijing , Lahm Tim , Meldrum Daniel R.
Published: January 2008

Understanding the mechanisms by which adult stem cells produce growth factors may represent an important way to optimize their beneficial paracrine and autocrine effects. Components of the wound milieu may stimulate growth factor production to promote stem cell-mediated repair. We hypothesized that tumor necrosis factor-α (TNF-α), endotoxin (LPS), or hypoxia may activate human mesenchymal stem cells (MSCs) to increase release of vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), insulin-like growth factor 1 (IGF-1), or hepatocyte growth factor (HGF) and that nuclear factor-κB (NFκB), c-Jun NH2-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) mediates growth factor production from human MSCs. To study this, human MSCs were harvested, passaged, divided into four groups (100,000 cells, triplicates) and treated as follows: 1) with vehicle; 2) with stimulant alone [24 h LPS (200 ng/ml), 24 h TNF-α (50 ng/ml), or 24 h hypoxia (1% O2)]; 3) with inhibitor alone [NFκB (PDTC, 1 mM), JNK (TI-JIP, 10 μM), or ERK (ERK Inhibitor II, 25 μM)]; and 4) with stimulant and the various inhibitors. After 24 h incubation, MSC activation was determined by measuring supernatants for VEGF, FGF2, IGF-1, or HGF (ELISA). TNF-α, LPS, and hypoxia significantly increased human MSC VEGF, FGF2, HGF, and IGF-1 production versus controls. Stem cells exposed to injury demonstrated increased activation of NFκB, ERK, and JNK. VEGF, FGF2, and HGF expression was significantly reduced by NFκB inhibition (50% decrease) but not ERK or JNK inhibition. Moreover, ERK, JNK, and NFκB inhibitor alone did not activate MSC VEGF expression over controls. Various stressors activate human MSCs to increase VEGF, FGF2, HGF, and IGF-1 expression, which depends on an NFkB mechanism.
The dual role of CD44 as a functional P-selectin ligand and fibrin receptor in colon carcinoma cell adhesion
Authors: Alves Christina S. , Burdick Monica M. , Thomas Susan N. , Pawar Parag , Konstantopoulos Konstantinos
Published: January 2008

Selectins and fibrin(ogen) play key roles in the hematogenous dissemination of tumor cells, and especially of colon carcinomas. However, the fibrin(ogen) receptor(s) on colon carcinoma cells has yet to be defined along with its relative capacity to bind fibrinogen versus fibrin under flow. Moreover, the functional P-selectin ligand has yet to be validated using intact platelets rather than purified selectin substrates. Using human CD44-knockdown and control LS174T cells, we demonstrate the pivotal involvement of CD44 in the P-selectin-mediated binding to platelets in shear flow. Quantitative comparisons of the binding kinetics of LS174T versus P-selectin glycoprotein ligand-1 (PSGL-1)-expressing THP-1 cells to activated platelets reveal that the relative avidity of P-selectin-CD44 binding is more than sevenfold lower than that of P-selectin-PSGL-1 interaction. Using CD44-knockdown LS174T cells and microspheres coated with CD44 immunoprecipitated from control LS174T cells, and purified fibrin(ogen) as substrate, we provide the first direct evidence that CD44 also acts as the major fibrin, but not fibrinogen, receptor on LS174T colon carcinoma cells. Interestingly, binding of plasma fibrin to CD44 on the colon carcinoma cell surface interferes with the P-selectin-CD44 molecular interaction and diminishes platelet-LS174T heteroaggregation in the high shear regime. Cumulatively, our data offer a novel perspective on the apparent metastatic potential associated with CD44 overexpression on colon carcinoma cells and the critical roles of P-selectin and fibrin(ogen) in metastatic spread and provide a rational basis for the design of new therapeutic strategies to impede metastasis.
Involvement of mammalian sirtuin 1 in the action of ethanol in the liver
Authors: You Min , Liang Xiaomei , Ajmo Joanne M. , Ness Gene C.
Published: January 2008

Chronic ethanol feeding causes liver steatosis in animal models by upregulating the sterol regulatory element-binding protein 1 (SREBP-1), which subsequently increases the synthesis of hepatic lipid. SREBP-1 activity is regulated by reversible acetylation at specific lysine residues. The present study tests the hypothesis that activation of SREBP-1 by ethanol may be mediated by mammalian sirtuin 1 (SIRT1), a NAD+-dependent class III protein deacetylase. The effects of ethanol on SIRT1 were determined in cultured rat hepatoma cells and in the livers of ethanol-fed mice. In rat H4IIEC3 cells, we observed that ethanol exposure induced SREBP-1c lysine acetylation and SREBP-1c transcriptional activity. The effect of ethanol was abolished by expression of wild-type SIRT1 or by treatment with resveratrol, a known potent SIRT1 agonist. Conversely, knocking down SIRT1 by the small silencing SIRT1 plasmid SIRT1shRNA or expression of a SIRT1 mutant, SIRT1(H363Y), did not negate the ethanol effect. These findings suggest that the effect of ethanol on SREBP-1 is mediated, at least in part, through SIRT1 inhibition. Consistent with the in vitro findings, chronic ethanol feeding substantially downregulated hepatic SIRT1 in mice. Inhibition of hepatic SIRT1 activity was associated with an increase in the acetylated active nuclear form of SREBP-1c in the livers of ethanol-fed mice. Our results indicate an essential role for SIRT1 in mediating the effects of ethanol on SREBP-1 and hepatic lipid metabolism, as well as the development of alcoholic fatty liver. Hence, SIRT1 may represent a novel therapeutic target for treatment of human alcoholic fatty liver disease.
Adverse renal consequences of obesity
Authors: Griffin Karen A. , Kramer Holly , Bidani Anil K.
Published: January 2008

Emerging evidence indicates that obesity, even in the absence of diabetes, contributes significantly to the development and progression of chronic kidney disease (CKD). Glomerular hyperfiltration/hypertrophy in response to the increased metabolic needs of obesity are postulated to lead to the development of glomerulosclerosis (GS) in a manner analogous to that in reduced renal mass states. Nevertheless, the individual risk for developing GS with obesity is very low. It is proposed that glomerular hyperfiltration/hypertrophy are per se not pathogenic in the absence of an enhanced glomerular blood pressure (BP) transmission, and the modest preglomerular vasodilation that is likely present in the large majority of obese individuals is not sufficient to result in such increased BP transmission. However, in the small subset of obese individuals who are also born with a substantially reduced nephron number, there is a greater risk of enhanced glomerular BP transmission due to the substantially greater preglomerular vasodilation. Of perhaps greater clinical importance, similar additive deleterious effects of obesity on BP transmission would be expected in individuals with reduced renal mass, either congenital or acquired, or with concurrent renal disease, leading to accelerated progression. Of note, a low birth weight may be a risk factor for not only reduced nephron numbers at birth, but also for obesity and hypertension, resulting in a clustering of risk factors for progressive GS. Therefore, even though the individual risk for developing obesity GS is low, the cumulative impact of obesity on the public health burden of CKD is likely to be large because of its huge prevalence.
Cues for Sound Localization Are Encoded in Multiple Aspects of Spike Trains in the Inferior Colliculus
Authors: Chase Steven M. , Young Eric D.
Published: January 2008

To localize sound, information from three cues—interaural timing differences (ITDs), interaural level differences (ILDs), and spectral notch cues (SNs)—must be properly integrated. The inferior colliculus (IC) receives convergent input from neurons encoding all three cues. Using virtual space stimuli and information theoretic techniques, we investigated the coding of the various localization cues in single neurons of the IC under different encoding schemes. Here we focus on the analysis of information encoded by first-spike latency, in comparison to previous results on discharge rate and ongoing spike timing. The results show that the localization cues converge to different degrees in particular neurons. ITD information is conveyed most strongly by spike rate, with small amounts of independent information in latency and ongoing spike timing. ILD information shows a similar pattern, with larger mutual information values for all three cues. For these cues, ongoing spike timing does not typically contribute independent information over that captured by a joint rate/first-spike latency code. SNs are coded by both rate and first-spike latency, but ongoing spike timing significantly enhances their representation in a best frequency–dependent manner, as long as the temporal envelope of the stimulus can be used in the decoder. The differential coding of the localization cues suggests that information about multiple cues could be multiplexed onto the responses of single neurons.
Obligatory Adaptation of Saccade Gains
Authors: Srimal Riju , Diedrichsen Jörn , Ryklin Edward B. , Curtis Clayton E.
Published: January 2008

We tested the hypothesis that saccade gains adapt to minimize error between the visual target and the saccade endpoint of every saccade we make even when the errors on sequential saccades are not directionally consistent. We utilized a state-space model that estimated the degree to which saccade gains were modified by the magnitude and direction of errors made on the previous trial. Importantly, to show that learning did not depend on the accumulation of directionally consistent errors, we fit the model to saccades made to targets that were displaced in a random direction during the saccade, thereby inducing errors with directions that were not sequentially the same. Saccade gains clearly adapted on a trial-by-trial basis despite that the perturbations were random, and the average amount of learning per trial was of similar magnitude as that found in a constant displacement of the target. These results indicate that saccade adaptation is a rapid and obligatory process that does not require conscious awareness.
Protease-Resistant Glucose-Dependent Insulinotropic Polypeptide Agonists Facilitate Hippocampal LTP and Reverse the Impairment of LTP Induced by Beta-Amyloid
Authors: Gault Victor A. , Hölscher Christian
Published: January 2008

Type 2 diabetes has been identified as a risk factor for Alzheimer's disease (AD). Insulin signaling is often impaired in AD, contributing to the neurodegeneration observed in AD patients. One potential strategy to overcome this impairment is to normalize insulin signaling in the brain. In the present study, we have examined the effects of an enzyme-resistant analogue of glucose-dependent insulinotropic polypeptide (GIP), N-AcGIP, on synaptic plasticity. N-AcGIP is a stable, long-acting peptide hormone that regulates glucose homeostasis and insulin release. We tested the effects of native GIP and the agonist N-AcGIP on synaptic plasticity [long-term potentiation (LTP)] in the hippocampus [15 nmol, administered intracerebroventricularly (icv)] and report for the first time that both peptides have enhancing effects on LTP. In contrast, the antagonist of GIP, Pro(3)GIP (15 nmol icv), reduced LTP. Injection of beta-amyloid(25–35) (100 nmol), a peptide that aggregates in brains of AD patients, also impaired LTP. The injection of N-AcGIP (15 nmol icv) 30 min prior to injection of amyloid(25–35) (100 nmol icv) fully reversed the impairment of LTP induced by beta-amyloid. The results demonstrate for the first time that GIP (particularly enzyme-resistant forms) not only directly modulates neurotransmitter release and LTP formation, but also protects synapses from the detrimental effects of beta-amyloid fragments on LTP formation. The use of enzyme-resistant analogues of GIP show great promise as a potential novel treatment for preventing neurodegenerative processes in AD and other related disorders.
Summation of Excitatory and Inhibitory Synaptic Inputs by Motoneurons With Highly Active Dendrites
Authors: Hyngstrom Allison S. , Johnson Michael D. , Heckman C. J.
Published: January 2008

We investigated summation of steady excitatory and inhibitory inputs in spinal motoneurons using an in vivo preparation, the decerebrate cat, in which neuromodulatory input from the brain stem facilitated a strong persistent inward current (PIC) in dendritic regions. This dendritic PIC amplified both excitatory and inhibitory synaptic currents two- to threefold, but within different voltage ranges. Amplification of excitatory synaptic current peaked at voltage-clamp holding potentials near spike threshold (about −55 to −50 mV), whereas amplification of inhibitory current peaked at significantly more depolarized levels (about −45 to −40 mV). Thus the linear sum of excitatory and inhibitory currents tended to vary from net excitatory to net inhibitory as holding potential was depolarized. The actual summed currents, however, diverged from the predicted linear currents. At the peak of excitation, summation averaged about 15% sublinear (actual sum was less positive than the linear sum). In contrast, at the peak of inhibition, summation averaged about 18% supralinear (actual more positive than linear). Moreover, these nonlinear effects were substantially larger in cells where the variation from peak excitation to peak inhibition for linear summation was larger. When descending neuromodulatory input was eliminated by acute spinalization, PIC amplification was not observed and summation tended to be either sublinear or approximately linear, depending on input source. Overall, in cells with strong PICs, nonlinear summation of excitation and inhibition does occur, but this nonlinearity results in a more consistent relationship between membrane potential and the summed excitatory and inhibitory current.
Encoding of Stimulus Frequency and Sensor Motion in the Posterior Medial Thalamic Nucleus
Authors: Masri Radi , Bezdudnaya Tatiana , Trageser Jason C. , Keller Asaf
Published: January 2008

In all sensory systems, information is processed along several parallel streams. In the vibrissa-to-barrel cortex system, these include the lemniscal system and the lesser-known paralemniscal system. The posterior medial nucleus (POm) is the thalamic structure associated with the latter pathway. Previous studies suggested that POm response latencies are positively correlated with stimulation frequency and negatively correlated with response duration, providing a basis for a phase locked loop-temporal decoding of stimulus frequency. We tested this hypothesis by analyzing response latencies of POm neurons, in both awake and anesthetized rats, to vibrissae deflections at frequencies between 0.3 and 11 Hz. We found no significant, systematic correlation between stimulation frequency and the latency or duration of POm responses. We obtained similar findings from recording in awake rats, in rats under different anesthetics, and in anesthetized rats in which the reticular activating system was stimulated. These findings suggest that stimulus frequency is not reliably reflected in response latency of POm neurons. We also tested the hypothesis that POm neurons respond preferentially to sensor motion, that is, they respond to whisking in air, without contacts. We recorded from awake, head-restrained rats while monitoring vibrissae movements. All POm neurons responded to passive whisker deflections, but none responded to noncontact whisking. Thus like their counterparts in the trigeminal ganglion, POm neurons may not reliably encode whisking kinematics. These observations suggest that POm neurons might not faithfully encode vibrissae inputs to provide reliable information on vibrissae movements or contacts.
Protein Kinase D in the Cardiovascular System
Authors: Avkiran Metin , Rowland Alexandra J. , Cuello Friederike , Haworth Robert S.
Published: January 2008

The protein kinase D (PKD) family is a recent addition to the calcium/calmodulin-dependent protein kinase group of serine/threonine kinases, within the protein kinase complement of the mammalian genome. Relative to their alphabetically superior cousins in the AGC group of kinases, namely the various isoforms of protein kinase A, protein kinase B/Akt, and protein kinase C, PKD family members have to date received limited attention from cardiovascular investigators. Nevertheless, increasing evidence now points toward important roles for PKD-mediated signaling pathways in the cardiovascular system, particularly in the regulation of myocardial contraction, hypertrophy and remodeling. This review provides a primer on PKD signaling, using information gained from studies in multiple cell types, and discusses recent data that suggest novel functions for PKD-mediated pathways in the heart and the circulation.
Kinematic and Moisture Characteristics of a Nonprecipitating Cold Front Observed during IHOP. Part I: Across-Front Structures
Authors: Friedrich Katja , Kingsmill David E. , Flamant Cyrille , Murphey Hanne V. , Wakimoto Roger M.
Published: January 2008

A wide array of ground-based and airborne instrumentation is used to examine the kinematic and moisture characteristics of a nonprecipitating cold front observed in west-central Kansas on 10 June 2002 during the International H2O Project (IHOP). This study, the first of two parts, is focused on describing structures in the across-front dimension. Coarsely resolved observations from the operational network and dropsondes deployed over a 200-km distance centered on the front are combined with higher-resolution observations from in situ sensors, Doppler radars, a microwave radiometer, and a differential absorption lidar that were collected across a ∼40-km swath that straddled a ∼100-km segment of the front.

The northeast–southwest-oriented cold front moved toward the southeast at ∼8–10 m s−1 during the morning hours, but its motion slowed to less than 1 m s−1 in the afternoon. In the early afternoon, the cold front separated cool air with a northerly component flow of 2–4 m s−1 from a 10-km-wide band of hot, dry air with 5 m s−1 winds out of the south-southwest. The average updraft at the frontal interface was ∼0.5 m s−1 and slightly tilted back toward the cool air. A dryline was located to the southeast of the front, separating the hot, dry air mass from a warm, moist air mass composed of 10 m s−1 southerly winds. Later in the afternoon, the warm, moister air moved farther to the northwest, approaching the cold front. The dryline was still well observed in the southwestern part of the observational domain while it vanished almost completely in the northeastern part. Low-level convergence (∼1 × 10−3 s−1), vertical vorticity (∼0.5 × 10−3 s−1), and vertical velocity (∼1 m s−1) increased. The strong stable layer located at ∼2.0–2.5 km MSL weakened in the course of the afternoon, providing a basis for the development of isolated thunderstorms. The applicability of gravity current theory to the cold front was studied. There was evidence of certain gravity current characteristics, such as Froude numbers between 0.7 and 1.4, a pronounced feeder flow toward the leading edge, and a rotor circulation. Other characteristics, such as a sharp change in pressure and lobe and cleft structures, remain uncertain due to the temporally and spatially variable nature of the phenomenon and the coarse resolution of the measurements.
A New Approximate Solution of the Optimal Nonlinear Filter for Data Assimilation in Meteorology and Oceanography
Authors: Hoteit I. , Pham D-T. , Triantafyllou G. , Korres G.
Published: January 2008

This paper introduces a new approximate solution of the optimal nonlinear filter suitable for nonlinear oceanic and atmospheric data assimilation problems. The method is based on a local linearization in a low-rank kernel representation of the state’s probability density function. In the resulting low-rank kernel particle Kalman (LRKPK) filter, the standard (weight type) particle filter correction is complemented by a Kalman-type correction for each particle using the covariance matrix of the kernel mixture. The LRKPK filter’s solution is then obtained as the weighted average of several low-rank square root Kalman filters operating in parallel. The Kalman-type correction reduces the risk of ensemble degeneracy, which enables the filter to efficiently operate with fewer particles than the particle filter. Combined with the low-rank approximation, it allows the implementation of the LRKPK filter with high-dimensional oceanic and atmospheric systems. The new filter is described and its relevance demonstrated through applications with the simple Lorenz model and a realistic configuration of the Princeton Ocean Model (POM) in the Mediterranean Sea.
The ECPC Coupled Prediction Model
Authors: Yulaeva E. , Kanamitsu M. , Roads J.
Published: January 2008

This paper presents a new Experimental Climate Prediction Center (ECPC) Coupled Prediction Model (ECPM). The ECPM includes the Jet Propulsion Laboratory (JPL) version of the Massachusetts Institute of Technology (MIT) ocean model coupled to the ECPC version of the National Centers for Environmental Prediction (NCEP) Atmospheric Global Spectral Model (GSM). The adjoint and forward versions of the MIT model forced with the NCEP atmospheric analyses are routinely used at JPL for ocean state assimilation. An earlier version of the GSM was used for the NCEP–Department of Energy reanalysis-2 project and for operational seasonal forecasts at NCEP. The ECPM climatology and internal variability derived from a 56-yr-long coupled integration are compared with the observations and reanalysis data. Though the ECPM exhibits climatological biases, these biases are relatively small and comparable to the systematic errors produced by other well-known coupled models, including the recent NCEP Climate Forecast System. The internal variability of the model resembles the observations. ECPM simulates both seasonal and interannual variability in the tropical Pacific reasonably well. The model has good skill in reproducing the mechanism of ENSO evolution as well as ENSO teleconnection patterns (including the Indian monsoon–ENSO relationship). The skill of the ECPM in predicting 1994–2006 SST anomalies over the Niño-3.4 region is shown to be comparable to other coupled models. These retrospective forecasts were used for deriving a model climatology for real-time seasonal forecasts that are currently produced and displayed at ECPC.
Impact of the Assimilation of CHAMP Refractivity Profiles on Environment Canada Global Forecasts
Authors: Aparicio Josep M. , Deblonde Godelieve
Published: January 2008

The data assimilation system of Environment Canada (EC) is adapted to accept GPS radio occultation (GPSRO) data. Observations of this type are available with extensive coverage from several satellites. In this study, experiments are performed to compare the skill of EC’s three-dimensional variational data assimilation (3DVAR) system (including all data normally assimilated operationally), with and without the addition of radio occultation refractivity data from the Challenging Minisatellite Payload for Geophysical Research (CHAMP). These data were not available at the time studied as near-real-time (NRT) observations. However, data from this and other radio occultation missions are now available as NRT data, and the conditions (latency, reliability) are improving. It is expected that NRT GPSRO data from a number of satellite missions will continue to be available through the following years. The results of the assimilation tests are evaluated against the following three data types: radiosondes (temperature and dewpoint depression), satellite brightness temperatures (from the Advanced Microwave Sounding Unit-A), and GPS radio occultation refractivity profiles. For the 6-h forecasts, the differences between GPSRO observations and forecasts (O − F) are significantly reduced in the experiment that assimilates the GPSRO data. This reduction increases as the experiment proceeds in time, and stabilizes after a transient period of approximately 2 weeks, suggesting that the addition of GPSRO data to the assimilation system has a beneficial, persisting, and cumulative effect. This effect is more pronounced in the stratosphere than in the troposphere. In the stratosphere, the standard deviation of GPSRO (O − F) of the experiment that assimilates GPSRO decreases after the initial transient period by approximately 10%. This improvement can best be observed in the southern stratosphere where reductions of the order of 30% are common. This shows that, as a globally distributed and vertically well-resolved source of data, the GPSRO observations are not only useful for assimilation, but also as a tool to quantify the forecast skill of the assimilation system. Comparisons with radiometer and radiosonde data confirm the positive impact in these geographical areas. Longer-range forecasts (up to 6 days) also show a positive impact with similar geographical and altitude distribution.
A Dynamical Investigation of the May 2004 McMurdo Antarctica Severe Wind Event Using AMPS*
Authors: Steinhoff Daniel F. , Bromwich David H. , Lambertson Michelle , Knuth Shelley L. , Lazzara Matthew A.
Published: January 2008

On 15–16 May 2004 a severe windstorm struck McMurdo, Antarctica. The Antarctic Mesoscale Prediction System (AMPS) is used, along with available observations, to analyze the storm. A synoptic-scale cyclone weakens as it propagates across the Ross Ice Shelf toward McMurdo. Flow associated with the cyclone initiates a barrier jet along the Transantarctic Mountains. Forcing terms from the horizontal equations of motion are computed in the barrier wind to show that the local time tendency and momentum advection terms are key components of the force balance. The barrier jet interacts with a preexisting near-surface radiation inversion over the Ross Ice Shelf to set up conditions favorable for the development of large-amplitude mountain waves, leading to a downslope windstorm in the Ross Island area. Hydraulic theory can explain the structure of the downslope windstorms, with amplification of the mountain waves possibly caused by wave-breaking events. The underestimation of AMPS wind speed at McMurdo is caused by the misplacement of a hydraulic jump downstream of the downslope windstorms. The dynamics associated with the cyclone, barrier jet, and downslope windstorms are analyzed to determine the role of each in development of the severe winds.
Numerical Study of the Local Downslope Wind “Hirodo-Kaze” in Japan
Authors: Fudeyasu Hironori , Kuwagata Tsuneo , Ohashi Yukitaka , Suzuki Shin-ichi , Kiyohara Yasutomo , Hozumi Yu
Published: January 2008

The “Hirodo-kaze,” a local strong wind accompanying the downslope winds in Japan, is examined using a mesoscale numerical model. The model successfully reproduces the major features of the observed Hirodo-kaze that occurred in association with Typhoon Pabuk. During the Hirodo-kaze, the severe downslope winds in the transitional flow develop in the lower troposphere below the mean-state critical layer. The Hirodo-kaze is closely linked to the strong wind region accompanying the severe downslope winds. After the cessation of the Hirodo-kaze, distinct mountain waves dominate in the lower troposphere where the Scorer parameter l2 decreases with height. The region of strong wind retreats windward as the Hirodo-kaze ceases. Temporal changes in the characteristics of mountain waves in the lee of Mt. Nagi are primarily attributed to the changes in the large-scale environmental winds due to the movement of the intense cyclone.

Environmental conditions favorable for the occurrence of the Hirodo-kaze include strong northerlies in the lower troposphere overlain by southerlies in the middle troposphere. The intense cyclone that moves over the sea southwest of the Kii peninsula creates favorable environmental conditions that support the occurrence of the Hirodo-kaze.
Numerical Simulations of the Microphysics and Electrification of the Weakly Electrified 9 February 1993 TOGA COARE Squall Line: Comparisons with Observations
Authors: Fierro Alexandre O. , Leslie Lance M. , Mansell Edward R. , Straka Jerry M.
Published: January 2008

A cloud scale model with a 12-class bulk microphysics scheme, including 10 ice phases and a 3D lightning parameterization, was used to investigate the electrical properties of a well-documented tropical squall line from the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE). Consistent with observations, the simulated maximum updraft speeds across the squall line seldom exceeded 10 m s−1, which was expected given the relatively shallow 30-dBZ echo tops that rarely extended above the top of the mixed-phase layer (−20°C isotherm). Enhanced warm rain processes caused most of the liquid water to precipitate near the gust front at lower levels (below 4 km AGL), which accounted for the small amounts of graupel and cloud water content present in the mixed-phase region and, consequently, for generally weak charging and electrification.

Most of the charge present in the squall line was generated within a few storm cells just behind the leading edge of the gust front that had sufficiently strong updraft speeds near the melting level to produce moderate values of graupel mixing ratio (>0.5 g kg−1). In contrast, the trailing stratiform region at the back of the line, which was mainly composed of ice crystals and snow particles, contained only weak net charge densities (<0.03 nC m−3). The spatial collocation of regions characterized by charge densities exceeding 0.01 nC m−3 and noninductive (NI) charging rates greater than 0.1 pC m−3 s−1 in this stratiform region suggests that NI charging is a plausible source for the majority of this charge, which was confined to discrete regions having small amounts of graupel (approximately 0.1–0.3 g kg−1) and cloud water content (CWC; ∼0.1 g m−3).

The simulated weak updraft speeds and shallow echo tops resulted in a system exhibiting little overall total lightning activity. Although the 5-min average intracloud (IC) flash rate rarely exceeded 10 flashes per minute and only 3 negative cloud-to-ground (−CG) lightning flashes were produced during the entire 4 h and 30 min of simulation, this still was more electrical activity than observed. This tendency for the model to generate more lightning flashes than observed remained when the inductive charging mechanism was turned off, which reduced the total amount of simulated flashes by about 43%. The three CG flashes and the great majority of the IC flashes occurred within the strongest cells located in the mature zone, which exhibited a normal tripole charge structure.
Comparison of In-Canopy Flux Footprints between Large-Eddy Simulation and the Lagrangian Simulation
Authors: Prabha T. V. , Leclerc M. Y. , Baldocchi D.
Published: January 2008

Flux footprints for neutral shear-driven canopy flows are evaluated using large-eddy simulation (LES) and a Lagrangian stochastic (LS) model. The Lagrangian stochastic model is driven by flow statistics derived from the large-eddy simulation. LES results suggest that both surface and elevated sources inside the canopy contribute equally to the cumulative flux from an upwind distance of 4 times the canopy height. LES flux footprints are more contracted than those obtained using the Lagrangian stochastic model. This is attributed to an enhanced vertical diffusion and reduced horizontal diffusion. The ejection and sweep contributions to momentum exchange in the Lagrangian stochastic model are weaker than those in the large-eddy simulation. Ejections of low-momentum air dominate at all levels in the canopy modeled by the LES. In contrast, high-momentum sweep events are dominant within the LES canopy and low-momentum ejection events are dominant above the canopy. Dispersion parameters for the first- and second-order statistics of concentration from both LES and LS for three line sources representing the canopy crown, midcanopy, and surface sources are also investigated. Lagrangian model results are sensitive to the choice of the time scale. A time scale based on the dissipation rate agrees well with the LS and LES plume heights of surface source. However, flux footprints from LS are closer to those from the LES, while an intermediate time scale (0.15z/σw) was used inside the canopy.
How Well Do Regional Climate Models Reproduce Radiation and Clouds in the Arctic? An Evaluation of ARCMIP Simulations
Authors: Tjernström Michael , Sedlar Joseph , Shupe Matthew D.
Published: January 2008

Downwelling radiation in six regional models from the Arctic Regional Climate Model Intercomparison (ARCMIP) project is systematically biased negative in comparison with observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment, although the correlations with observations are relatively good. In this paper, links between model errors and the representation of clouds in these models are investigated. Although some modeled cloud properties, such as the cloud water paths, are reasonable in a climatological sense, the temporal correlation of model cloud properties with observations is poor. The vertical distribution of cloud water is distinctly different among the different models; some common features also appear. Most models underestimate the presence of high clouds, and, although the observed preference for low clouds in the Arctic is present in most of the models, the modeled low clouds are too thin and are displaced downward. Practically all models show a preference to locate the lowest cloud base at the lowest model grid point. In some models this happens also to be where the observations show the highest occurrence of the lowest cloud base; it is not possible to determine if this result is just a coincidence. Different factors contribute to model surface radiation errors. For longwave radiation in summer, a negative bias is present both for cloudy and clear conditions, and intermodel differences are smaller when clouds are present. There is a clear relationship between errors in cloud-base temperature and radiation errors. In winter, in contrast, clear-sky cases are modeled reasonably well, but cloudy cases show a very large intermodel scatter with a significant bias in all models. This bias likely results from a complete failure in all of the models to retain liquid water in cold winter clouds. All models overestimate the cloud attenuation of summer solar radiation for thin and intermediate clouds, and some models maintain this behavior also for thick clouds.
Some Space–Time Spectral Analyses of Tropical Convection and Planetary-Scale Waves
Authors: Hendon Harry H. , Wheeler Matthew C.
Published: January 2008

Three aspects of space–time spectral analysis are explored for diagnosis of the organization of tropical convection by the Madden–Julian oscillation (MJO) and other equatorial wave modes: 1) definition of the background spectrum upon which spectral peaks are assessed, 2) alternate variance preserving display of the spectra, and 3) the space–time coherence spectrum. Here the background spectrum at each zonal wavenumber is assumed to result from a red noise process. The associated decorrelation time for the red noise process for tropical convection is found to be half as long as for zonal wind, reflecting the different physical processes controlling each field. The significance of spectral peaks associated with equatorial wave modes for outgoing longwave radiation (OLR), which is a proxy for precipitating deep convection, and zonal winds that stand out above the red background spectrum is similar to that identified using a background spectrum resulting from ad hoc smoothing of the original spectrum. A variance-preserving display of the space–time power spectrum with a logarithmic frequency axis is useful for directly detecting Kelvin waves (periods 5–15 days for eastward zonal wavenumbers 1–5) and for highlighting their distinction from the MJO. The space–time coherence of OLR and zonal wind is predominantly associated with the MJO and other equatorial waves. The space–time coherence is independent of estimating the background spectrum and is quantifiable; thus, it is suggested as a useful metric for the MJO and other equatorial waves in observations and simulations. The space–time coherence is also used to quantify the association of Kelvin waves in the stratosphere with convective variability in the troposphere and for detection of barotropic Rossby–Haurwitz waves.
Characteristics of the Northern Australian Rainy Season
Authors: Smith I. N. , Wilson L. , Suppiah R.
Published: January 2008

A trend of increasing rainfall over much of north and northwest Australia over recent decades has contrasted with decreases over much of the rest of the continent. The increases have occurred during the summer months when the rainy season is dominated by the Australian monsoon but is also affected by other events such as tropical cyclones, Madden–Julian oscillations, and sporadic thunderstorms. The problem of diagnosing these trends is considered in terms of changes in the timing of the rainy season. While numerous definitions for rainy/monsoon season onset exist, most are designed to be useful in a predictive sense and can be limited in their application to diagnostic studies, particularly when they involve predetermined threshold amounts. Here the authors define indices, based on daily rainfall observations, that provide relatively simple, robust descriptions of each rainy season at any location. These are calculated using gridded daily rainfall data throughout the northern Australian tropics and also for selected stations. The results indicate that the trends in summer rainfall totals over the period from 1950 to 2005 appear to be mainly the result of similar trends in average intensity. Furthermore, the links between the September–October average Southern Oscillation index indicate that ENSO events affect season duration rather than average intensity. Because duration and average intensity are derived as independent features of each season, it is argued that the trends in rainfall totals are largely unrelated to trends in ENSO and most likely reflect the influence of other factors. Finally, diagnosing these features of the rainy season provides a basis for assessing the confidence one can attach to different climate model projections of changes to rainfall.
Soil Thermal and Ecological Impacts of Rain on Snow Events in the Circumpolar Arctic
Authors: Rennert Kevin J. , Roe Gerard , Putkonen Jaakko , Bitz Cecilia M.
Published: January 2008

Rain on snow (ROS) events are rare in most parts of the circumpolar Arctic, but have been shown to have great impact on soil surface temperatures and serve as triggers for avalanches in the midlatitudes, and they have been implicated in catastrophic die-offs of ungulates. The study of ROS is inherently challenging due to the difficulty of both measuring rain and snow in the Arctic and representing ROS events in numerical weather predictions and climate models. In this paper these challenges are addressed, and the occurrence of these events is characterized across the Arctic. Incidents of ROS in Canadian meteorological station data and in the 40-yr ECMWF Re-Analysis (ERA-40) are compared to evaluate the suitability of these datasets for characterizing ROS. The ERA-40 adequately represents the large-scale synoptic fields of ROS, but too often has a tendency toward drizzle. Using the ERA-40, a climatology of ROS events is created for thresholds that impact ungulate populations and permafrost. It is found that ROS events with the potential to harm ungulate mammals are widespread, but the large events required to impact permafrost are limited to the coastal margins of Beringia and the island of Svalbard. The synoptic conditions that led to ROS events on Banks Island in October of 2003, which killed an estimated 20 000 musk oxen, and on Svalbard, which led to significant permafrost warming in December of 1995, are examined. Compositing analyses are used to show the prevailing synoptic conditions that lead to ROS in four disparate parts of the Arctic. Analysis of ROS in the daily output of a fully coupled GCM under a future climate change scenario finds an increase in the frequency and areal extent of these events for many parts of the Arctic over the next 50 yr and that expanded regions of permafrost become vulnerable to ROS.