bluuebunny/crossref_metadata_2025 huggingface dataset:
Amelioration of Established Diabetic Nephropathy by Combined Treatment with SMP-534 (Antifibrotic Agent) and Losartan in db/db Mice
Authors: Sugaru Eiji , Nakagawa Tsutomu , Ono-Kishino Michiko , Nagamine Jun , Tokunaga Teruhisa , Kitoh Makoto , Hume W. Ewan , Nagata Ryu , Taiji Mutsuo
Published: December 2006

Background/Aims: Diabetic nephropathy is the main cause of end-stage renal disease. Previously we have demonstrated that SMP-534 (an antifibrotic agent) prevents the development of diabetic nephropathy in db/db mouse and that combined treatment with SMP-534 and losartan (antihypertensive agents) markedly prevents the development of diabetic nephropathy compared with single treatment. SMP-534 or losartan was prophylactically administered to db/db mice before the onset of diabetic nephropathy. In the present study, we evaluated the efficacy of combined treatment when administration was started after the onset of diabetic nephropathy. Methods:db/db mice were raised untreated until 17 weeks of age, by which time increase of urinary albumin was noted, and then treated with SMP-534 and/or losartan for another 8 weeks. Biochemical and histological analyses were performed at 25 weeks of age. Results: Combined treatment with SMP-534 and losartan markedly prevented the increase ofurinary albumin and ameliorated the progression of mesangial matrix expansion, even when administration was started long after the increase of urinary albumin. Conclusion: The study results indicate that a combination of SMP-534 and losartan might be a valuable therapeutic approach for the treatment of diabetic nephropathy even when administration is started after the onset of diabetic nephropathy.
Mass-Spectrometric Identification of a Novel Angiotensin Peptide in Human Plasma
Authors: Jankowski Vera , Vanholder Raymond , van der Giet Markus , Tölle Markus , Karadogan Sevil , Gobom Johan , Furkert Jens , Oksche Alexander , Krause Eberhard , Anh Tran Thi Nguyet , Tepel Martin , Schuchardt Mirjam , Schlüter Hartmut , Wiedon Annette , Beyermann Michael , Bader Michael , Todiras Mihail , Zidek Walter , Jankowski Joachim
Published: December 2006

Objective—Angiotensin peptides play a central role in cardiovascular physiology and pathology. Among these peptides, angiotensin II (Ang II) has been investigated most intensively. However, further angiotensin peptides such as Ang 1-7, Ang III, and Ang IV also contribute to vascular regulation, and may elicit additional, different, or even opposite effects to Ang II. Here, we describe a novel Ang II-related, strong vasoconstrictive substance in plasma from healthy humans and end-stage renal failure patients.

Methods and Results—Chromatographic purification and structural analysis by matrix-assisted laser desorption/ionisation time-of-flight/time-of-flight (MALDI-TOF/TOF) revealed an angiotensin octapeptide with the sequence Ala-Arg-Val-Tyr-Ile-His-Pro-Phe, which differs from Ang II in Ala1instead of Asp1. Des[Asp1]-[Ala1]-Ang II, in the following named Angiotensin A (Ang A), is most likely generated enzymatically. In the presence of mononuclear leukocytes, Ang II is converted to Ang A by decarboxylation of Asp1. Ang A has the same affinity to the AT1receptor as Ang II, but a higher affinity to the AT2receptor. In the isolated perfused rat kidney, Ang A revealed a smaller vasoconstrictive effect than Ang II, which was not modified in the presence of the AT2 receptor antagonist PD 123319, suggesting a lower intrinsic activity at the AT1receptor. Ang II and Ang A concentrations in plasma of healthy subjects and end-stage renal failure patients were determined by matrix-assisted laser desorption/ionisation mass-analysis, because conventional enzyme immunoassay for Ang II quantification did not distinguish between Ang II and Ang A. In healthy subjects, Ang A concentrations were less than 20% of the Ang II concentrations, but the ratio Ang A / Ang II was higher in end-stage renal failure patients.

Conclusion—Ang A is a novel human strong vasoconstrictive angiotensin-derived peptide, most likely generated by enzymatic transformation through mononuclear leukocyte-derived aspartate decarboxylase. Plasma Ang A concentration is increased in end-stage renal failure. Because of its stronger agonism at the AT2receptor, Ang A may modulate the harmful effects of Ang II.
Cardiomyocyte-Specific Overexpression of Nitric Oxide Synthase 3 Prevents Myocardial Dysfunction in Murine Models of Septic Shock
Authors: Ichinose Fumito , Buys Emmanuel S. , Neilan Tomas G. , Furutani Elissa M. , Morgan John G. , Jassal Davinder S. , Graveline Amanda R. , Searles Robert J. , Lim Chee C. , Kaneki Masao , Picard Michael H. , Scherrer-Crosbie Marielle , Janssens Stefan , Liao Ronglih , Bloch Kenneth D.
Published: December 2006

Myocardial dysfunction contributes to the high mortality of patients with endotoxemia. Although nitric oxide (NO) has been implicated in the pathogenesis of septic cardiovascular dysfunction, the role of myocardial NO synthase 3 (NOS3) remains incompletely defined. Here we show that mice with cardiomyocyte-specific NOS3 overexpression (NOS3TG) are protected from myocardial dysfunction and death associated with endotoxemia. Endotoxin induced more marked impairment of Ca
2+
transients and cellular contraction in wild-type than in NOS3TG cardiomyocytes, in part, because of greater total sarcoplasmic reticulum Ca
2+
load and myofilament sensitivity to Ca
2+
in the latter during endotoxemia. Endotoxin increased reactive oxygen species production in wild-type but not NOS3TG hearts, in part, because of increased xanthine oxidase activity. Inhibition of NOS by
N
G
-nitro-
l
-arginine-methyl ester restored the ability of endotoxin to increase reactive oxygen species production and xanthine oxidase activity in NOS3TG hearts to the levels measured in endotoxin-challenged wild-type hearts. Allopurinol, a xanthine oxidase inhibitor, attenuated endotoxin-induced reactive oxygen species accumulation and myocardial dysfunction in wild-type mice. The protective effects of cardiomyocyte NOS3 on myocardial function and survival were further confirmed in a murine model of polymicrobial sepsis. These results suggest that increased myocardial NO levels attenuate endotoxin-induced reactive oxygen species production and increase total sarcoplasmic reticulum Ca
2+
load and myofilament sensitivity to Ca
2+
, thereby reducing myocardial dysfunction and mortality in murine models of septic shock.
Clinical Deterioration After Intravenous Recombinant Tissue Plasminogen Activator Treatment
Authors: Saqqur Maher , Molina Carlos A. , Salam Abdul , Siddiqui Muzaffar , Ribo Marc , Uchino Ken , Calleja Sergio , Garami Zsolt , Khan Khaurshid , Akhtar Naveed , O’Rourke Finton , Shuaib Ashfaq , Demchuk Andrew M. , Alexandrov Andrei V.
Published: December 2006

Background and Purpose—

Patients may experience clinical deterioration (CD) after treatment with intravenous recombinant tissue plasminogen activator (rt-PA). We evaluated the ability of flow findings on transcranial Doppler to predict CD and outcomes on modified Rankin Scale.

Methods—

Patients with acute stroke received intravenous rt-PA within 3 hours of symptom onset at four academic centers. CD was defined as an increase in the National Institutes of Health Stroke Scale (NIHSS) score by 4 points or more within 24 hours. Poor long-term outcome was defined by modified Rankin Scale ≥2 at 3 months. Transcranial Doppler findings were interpreted using the Thrombolysis in Brain Ischemia flow grading system as persistent arterial occlusion, reocclusion, or complete recanalization. Multiple regression analysis was used to identify transcranial Doppler flow as a predictor for CD after controlling for age, sex, baseline NIHSS, hypertension, and glucose.

Results—

A total of 374 patients received intravenous rt-PA at 142±60 minutes (median pretreatment NIHSS score 16 points). At the end of intravenous rt-PA infusion, transcranial Doppler showed persistent arterial occlusion in 219 patients (59%), arterial reocclusion in 54 patients (14%), and complete recanalization in 101 patients (27%). CD occurred in 44 patients: 36 had persistent arterial occlusion or reocclusion (82%), 13 symptomatic intracerebral hemorrhage (29%), and both persistent occlusion/reocclusion and symptomatic intracerebral hemorrhage in 10 patients (23%). After adjustment, patient risk for CD with persistent occlusion was OR 1.7 (95% CI: 0.7 to 4) and with arterial reocclusion 4.9 (95% CI: 1.7 to 13) (
P
=0.002). Patient risk for poor long-term outcomes with persistent occlusion, partial recanalization, or reocclusion was OR 5.2 (95% CI: 2.7 to 9,
P
=0.001).

Conclusions—

Inability to achieve or sustain vessel patency at the end of rt-PA infusion correlates with the likelihood of clinical deterioration and poor long-term outcome. Early arterial reocclusion on transcranial Doppler is highly predictive of CD and poor outcome.
Accuracy of the Siriraj and Guy’s Hospital Stroke Scores in Urban South Africans
Authors: Connor Myles D. , Modi Girish , Warlow Charles P.
Published: December 2006

Background and Purpose—

The burden of stroke in sub-Saharan Africa is already high and likely to increase, but few patients with stroke have access to brain imaging. Distinguishing pathologic stroke types is relevant both for clinical management and epidemiologic studies. We assessed the accuracy of two stroke scores in distinguishing stroke types in a population known to have a high prevalence of intracranial hemorrhage but low prevalence of atherosclerosis and compared them with the clinicians’ assessment of stroke type with computed tomography brain scanning as the “gold standard.”

Methods—

We assessed the stroke scores and the clinicians’ blind assessment of pathologic stroke type in consecutive black patients with stroke included in the Johannesburg Hospital Stroke Register over 23 months. We calculated the accuracy of the scores and clinicians compared with computed tomography brain scan (sensitivity, specificity, positive predictive value, likelihood ratio, κ statistic).

Results—

Two hundred twenty-two patients were scanned and assessed within 15 days. Sixty-two (28%) had cerebral hemorrhage and nine (4%) subarachnoid hemorrhage. Neither the Siriraj (sub-Saharan Africa) nor Guy’s Hospital score was accurate or offered much advantage over clinician assessment (sensitivity 0.60 and 0.34, specificity 0.88 and 0.95 for intracranial hemorrhage in the Siriraj Stroke Score and Guy’s Hospital Stroke Score, respectively; sensitivity 0.70 and 0.71, specificity 0.84 and 0.74, respectively, for ischemic stroke). Although the scores were more accurate when we used new cutoff points, they then failed to diagnose over 80% of stroke types.

Conclusions—

The Siriraj Stroke Score and Guy’s Hospital Stroke Score are not sufficiently accurate for use in either epidemiologic studies or to guide clinical management in sub-Saharan Africa at present.
Can Any Public Good Come from Evangelicals? Theological Paradigms and Possibilities Toward a Transforming South Africa
Authors: Le Bruyns Clint
Published: November 2006

This article employs the methodological framework of Gabriel Fackre on contemporary evangelicalism to explore the discernible public import of the evangelical movement within South Africa. It argues that evangelicals are already participants in public life and can potentially contribute to the healing of a divided and scarred South Africa through their respective ecclesial and theological capital.
The Rights of Children: A New Agenda For Practical Theology in South Africa
Authors: Yates Hannelie , Swart Ignatius
Published: November 2006

The aim of this article is to give prominence to the rights of children as a new agenda for Practical Theology in South Africa. Adopting a distinctly contextual approach, the article takes a critical look at the problematic situation of children in present-day South Africa and then focuses attention on the emergence of a children's rights agenda, both internationally and in South African society. A discussion of these aspects leads the authors to address pertinently the issue of Christian theology's complementary role in the children's rights agenda, which, however, is problematised in the light of theology's one-sided and limited involvement thus far in the issue of children. It is argued that a practical theological paradigm – in which a praxis of liberation, change and transformation is of prime importance – should reflect an active involvement in the children's rights agenda. In the light of the special realities of South African society, the importance of meeting distinct contextual and hermeneutical challenges is stated as condition for an effective practical theological involvement in the problematics of the rights of children.
He Darkens Me with Brightness: The Theology of Pseudo-Dionysius in Hilduin's Vita of Saint Denis
Authors: Delaporte Marianne
Published: November 2006

In the 9th century Hilduin of Saint Denis wrote two lives of Saint Denis for Louis the Pious, one in prose and one in poetry. These lives, predominantly the prose, were partially a collage of two previous lives and other documents to which Hilduin had access, including the works of Pseudo-Dionysius, which Hilduin first translated for the West. Hilduin displays particular originality as a hagiographer by giving us a synopsis and some commentary upon the Pseudo-Dionysian opus. By examining the first portion of the vita, which includes the nine chapters dedicated to the writings of the saint, one can begin to examine how Hilduin understand Pseudo-Dionysian theology and its impact upon the entire vita.
Fictive Scheintod and Christian Resurrection
Authors: Perkins Judith
Published: November 2006

In his chapter titled 'Resurrection' in Fiction as History, Glen Bowersock examines examples of 'apparent death' (Scheintod) in Graeco-Roman narrative fictions. He concludes his analysis by questioning 'whether the extraordinary growth in fictional writing, and its characteristic and concomitant fascination with resurrection' might be 'some kind of reflection of the remarkable stories that were coming out of Palestine in the middle of the first century A.D.' In this essay I will offer that rather than seeing a relation of influence between fictive prose narratives and Christian discourse (especially Christian bodily resurrection discourse) of the early centuries C.E., these sets of texts should be recognised as different manifestations of an attempt to address the same problem, that of negotiating notions of cultural identity in the matrix of early Roman imperialism. That these texts share similar motifs and themes – gruesome and graphic descriptions of torture, dismemberment, cannibalism and death – results not necessarily from influence, but that they converge around the same problem, drawing from a common cultural environment in the same historical context.
The Roles of the Hadley Circulation and Downward Control in Tropical Upwelling
Authors: Zhou Tiehan , Geller Marvin A. , Hamilton Kevin
Published: November 2006

Several idealized models of tropical upwelling are presented in order to clarify the roles of the nonlinear Hadley circulation and extratropical wave driving. In particular, it is shown that the Hadley circulation and wave-driven circulation interact to determine the nature of tropical upwelling. The authors explain several observed features such as maximum upwelling in the summer subtropics and the annual variation of the upwelling.
A Bootstrap Technique for Testing the Relationship between Local-Scale Radar Observations of Cloud Occurrence and Large-Scale Atmospheric Fields
Authors: Marchand Roger , Beagley Nathaniel , Thompson Sandra E. , Ackerman Thomas P. , Schultz David M.
Published: November 2006

A classification scheme is created to map the synoptic-scale (large scale) atmospheric state to distributions of local-scale cloud properties. This mapping is accomplished by a neural network that classifies 17 months of synoptic-scale initial conditions from the rapid update cycle forecast model into 25 different states. The corresponding data from a vertically pointing millimeter-wavelength cloud radar (from the Atmospheric Radiation Measurement Program Southern Great Plains site at Lamont, Oklahoma) are sorted into these 25 states, producing vertical profiles of cloud occurrence. The temporal stability and distinctiveness of these 25 profiles are analyzed using a bootstrap resampling technique.

A stable-state-based mapping from synoptic-scale model fields to local-scale cloud properties could be useful in three ways. First, such a mapping may improve the understanding of differences in cloud properties between output from global climate models and observations by providing a physical context. Second, this mapping could be used to identify the cause of errors in the modeled distribution of clouds—whether the cause is a difference in state occurrence (the type of synoptic activity) or the misrepresentation of clouds for a particular state. Third, robust mappings could form the basis of a new statistical cloud parameterization.
Testing and Comparing the Modified Anomalous Diffraction Approximation
Authors: Mitchell David L. , Baran Anthony J. , Arnott W. P. , Schmitt C.
Published: November 2006

The modified anomalous diffraction approximation (MADA) is used to predict absorption and extinction in water and ice clouds, but it does not predict the scattering phase function or asymmetry parameter g. In conjunction with g parameterizations, it has been used in satellite remote sensing and to treat the radiative properties of ice clouds in global climate models. However, it has undergone only limited testing. This study 1) compares extinction efficiencies (Qext) predicted by MADA for a laboratory grown ice cloud against corresponding Qext measurements over the wavelength range 2–14 μm; 2) tests absorption efficiencies (Qabs) and Qext predicted by MADA against those predicted by T-matrix theory and the finite difference time domain (FDTD) method; and 3) compares MADA with three popular schemes used for predicting the radiative properties of cirrus clouds. In addition, the photon tunneling process may contribute up to 45% of the absorption in water clouds at some terrestrial wavelengths, but its role in ice clouds is uncertain since it depends on particle shape. For the first time, the efficiency of photon tunneling was parameterized in terms of ice particle shape. Finally, an alternate formulation of MADA that offers some physical insights is presented.

MADA errors relative to the Qext measurements were 3.0% on average, while mean MADA errors relative to Qabs from T-matrix, over the wavelength range 2–18 μm (size parameter range 2–22), were 5.9%. The mean error for the single scattering albedo relative to T-matrix calculations was 2.5%. MADA absorption errors relative to FDTD over the wavelength range 3–100 μm were no greater than 15% for six ice particle shapes. Finally, the absorption coefficients predicted by MADA and two other popular parameterizations generally agreed within 5%.
Turbulent Velocity-Variance Profiles in the Stable Boundary Layer Generated by a Nocturnal Low-Level Jet
Authors: Banta Robert M. , Pichugina Yelena L. , Brewer W. Alan
Published: November 2006

Profiles of mean winds and turbulence were measured by the High Resolution Doppler lidar in the strong-wind stable boundary layer (SBL) with continuous turbulence. The turbulence quantity measured was the variance of the streamwise wind velocity component σ2u. This variance is a component of the turbulence kinetic energy (TKE), and it is shown to be numerically approximately equal to TKE for stable conditions—profiles of σ2u are therefore equivalent to profiles of TKE. Mean-wind profiles showed low-level jet (LLJ) structure for most of the profiles, which represented 10-min averages of mean and fluctuating quantities throughout each of the six nights studied. Heights were normalized by the height of the first LLJ maximum above the surface ZX, and the velocity scale used was the speed of the jet UX, which is shown to be superior to the friction velocity u* as a velocity scale. The major results were 1) the ratio of the maximum value of the streamwise standard deviation to the LLJ speed σu/UX was found to be 0.05, and 2) the three most common σ2u profile shapes were determined by stability (or Richardson number Ri). The least stable profile shapes had the maximum σ2u at the surface decreasing to a minimum at the height of the LLJ; profiles that were somewhat more stable had constant σ2u through a portion of the subjet layer; and the most stable of the profiles had a maximum of σ2u aloft, although it is important to note that the Ri for even the most stable of the three profile categories averaged less than 0.20. The datasets used in this study were two nights from the Cooperative Atmosphere–Surface Exchange Study 1999 campaign (CASES-99) and four nights from the Lamar Low-Level Jet Project, a wind-energy experiment in southeast Colorado, during September 2003.
Melting Layer Cloud Observed during R/V Mirai Cruise MR01-K05
Authors: Yasunaga Kazuaki , Yoneyama Kunio , Kubota Hisayuki , Okamoto Hajime , Shimizu Atsushi , Kumagai Hiroshi , Katsumata Masaki , Sugimoto Nobuo , Matsui Ichiro
Published: November 2006

In this study, cloud profiling radar and lidar were used to determine the frequency distribution of the base heights of cloudy layers with little (or no) falling condensate particles. The data were obtained from stationary observations conducted from Research Vessel Mirai over the tropical western Pacific (around 1.85°N, 138°E) from 9 November to 9 December 2001. The observed cloudy layers had base heights predominantly in the range of 4.5–6.5 km. Almost all cloudy layers with a base in the range of 4.5–6.5 km had thickness thinner than 500 m, and the frequency peak of the base heights of measured cloudy layers is considered to represent the common occurrence of midlevel thin clouds.

Midlevel thin clouds were frequently observed even during the active phase of the Madden–Julian oscillation (MJO). Composite analysis of radiosonde-derived relative humidity and temperature lapse rate indicates that the midlevel thin cloud in the MJO active period is generated via melting within the stratiform cloud, rather than by detrainment of surface-based convection.
The Madden–Julian Oscillation Recorded in Early Observations from the Tropical Rainfall Measuring Mission (TRMM)
Authors: Masunaga Hirohiko , L’Ecuyer Tristan S. , Kummerow Christian D.
Published: November 2006

A satellite data analysis is performed to explore the Madden–Julian oscillation (MJO) focusing on the potential roles of the equatorial Rossby (ER) and Kelvin waves. Measurements from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and Visible/Infrared Scanner (VIRS) are analyzed in the frequency–wavenumber domain to identify and ultimately filter primary low-frequency modes in the Tropics. The space–time spectrum of deep-storm fraction estimated by PR and VIRS exhibits notable Kelvin wave signals at wavenumbers 5–8, a distinct MJO peak at wavenumbers 1–7 and periods of about 40 days, and a signal corresponding to the ER wave. These modes are separately filtered to study the individual modes and possible relationship among them in the time–longitude space. In 10 cases analyzed here, an MJO event is often collocated with a group of consecutive Kelvin waves as well as an intruding ER wave accompanied with the occasional onset of a stationary convective phase. The spatial and temporal relationship between the MJO and Kelvin wave is clearly visible in a lag composite diagram, while the ubiquity of the ER wave leads to a less pronounced relation between the MJO and ER wave. A case study based on the Geostationary Meteorological Satellite (GMS) imagery together with associated dynamic field captures the substructure of the planetary-scale waves. A cross-correlation analysis confirms the MJO-related cycle that involves surface and atmospheric parameters such as sea surface temperature, water vapor, low clouds, shallow convection, and near-surface wind as proposed in past studies. The findings suggest the possibility that a sequence of convective events coupled with the linear waves may play a critical role in MJO propagation. An intraseasonal radiative–hydrological cycle inherent in the local thermodynamic conditions could be also a potential factor responsible for the MJO by loosely modulating the envelope of the entire propagation system.
Further Results on Moist Nearly Neutral Flow over a Ridge
Authors: Miglietta M. M. , Rotunno R.
Published: November 2006

In a recent study, the authors performed numerical simulations of moist nearly neutral flows over a ridge using the Weather Research and Forecasting (WRF) Model in a regime where the Coriolis force can be neglected and with the simple Kessler (warm rain) microphysical scheme. In the present work, further numerical solutions using more general and realistic experimental conditions are discussed. The upstream-propagating disturbance, which was found in the author’s previous study to desaturate the initially saturated sounding for intermediate mountain heights, is present for all the simulations with taller mountains considered in the present work. The inclusion of the Coriolis force however suppresses the upwind propagation of the dry region and weakens the downstream development of convective cells.

The sensitivity to different microphysical schemes has also been investigated. The simple Kessler scheme was compared with a more complete scheme, by Lin et al., which includes ice species. Some differences between the warm-rain-only and ice-microphysics simulations emerge mainly as a consequence of the different distributions of initial cloud water needed to produce a steady-state environmental flow. The effects of the different microphysical schemes on the rainfall rate have also been analyzed, with significant differences between them emerging in the case of narrower mountains. Finally, the sensitivity of the rainfall to the surface temperature has been studied, showing that for higher surface temperatures, the rainfall rate can be smaller although the available water content is larger, as a consequence of the differing microphysical processes activated in the different temperature regimes.
Stochastic Models for the Kinematics of Moisture Transport and Condensation in Homogeneous Turbulent Flows
Authors: O’Gorman Paul A. , Schneider Tapio
Published: November 2006

The transport of a condensing passive scalar is studied as a prototype model for the kinematics of moisture transport on isentropic surfaces. Condensation occurs whenever the scalar concentration exceeds a specified local saturation value. Since condensation rates are strongly nonlinear functions of moisture content, the mean moisture flux is generally not diffusive. To relate the mean moisture content, mean condensation rate, and mean moisture flux to statistics of the advecting velocity field, a one-dimensional stochastic model is developed in which the Lagrangian velocities of air parcels are independent Ornstein–Uhlenbeck (Gaussian colored noise) processes. The mean moisture evolution equation for the stochastic model is derived in the Brownian and ballistic limits of small and large Lagrangian velocity correlation time. The evolution equation involves expressions for the mean moisture flux and mean condensation rate that are nonlocal but remarkably simple. In a series of simulations of homogeneous two-dimensional turbulence, the dependence of mean moisture flux and mean condensation rate on mean saturation deficit is shown to be reproducible by the one-dimensional stochastic model, provided eddy length and time scales are taken as given. For nonzero Lagrangian velocity correlation times, condensation reduces the mean moisture flux for a given mean moisture gradient compared with the mean flux of a noncondensing scalar.
Dynamical Subgrid-Scale Parameterizations from Direct Numerical Simulations
Authors: Frederiksen Jorgen S. , Kepert Steven M.
Published: November 2006

Dynamical subgrid-scale parameterizations of stochastic backscatter, eddy drain viscosity, and net eddy viscosity have been formulated and calculated for two-dimensional turbulent flows on the sphere based on the statistics of direct numerical simulations (DNSs) with the barotropic vorticity equation. A relatively simple methodology based on a stochastic model representation of the subgrid-scale eddies, but which takes into account the memory effects of turbulent eddies, has been employed. The parameterizations have a cusp behavior at the cutoff wavenumber of the retained scales and have closely similar forms to those based on eddy damped quasi-normal Markovian (EDQNM) and direct interaction approximation (DIA) closure models. Large-eddy simulations (LESs) incorporating DNS-based subgrid-scale parameterizations are found to have kinetic energy spectra that compare closely with the results of higher-resolution DNS at the scales of LES for both isotropic turbulence and Rossby wave turbulence. The methodology presented is general and should be equally applicable to parameterizations of baroclinic processes and convective processes. Applications of the parameterizations to climate models and prediction models are discussed.
Further Analysis of Lorenz’s Maximum Simplification Equations
Authors: Lakshmivarahan S. , Baldwin Michael E. , Zheng Tao
Published: November 2006

The goal of this paper is to provide a complete picture of the long-term behavior of Lorenz’s maximum simplification equations along with the corresponding meteorological interpretation for all initial conditions and all values of the parameter.
Are the North Atlantic Oscillation and the Northern Annular Mode Distinguishable?
Authors: Feldstein Steven B. , Franzke Christian
Published: November 2006

This study addresses the question of whether persistent events of the North Atlantic Oscillation (NAO) and the Northern Annular Mode (NAM) teleconnection patterns are distinguishable from each other. Standard daily index time series are used to specify the amplitude of the NAO and NAM patterns. The above question is examined with composites of sea level pressure, and 300- and 40-hPa streamfunction, along with tests of field significance.

A null hypothesis is specified that the NAO and NAM persistent events are indistinguishable. This null hypothesis is evaluated by calculating the difference between time-averaged NAO and NAM composites. It is found that the null hypothesis cannot be rejected even at the 80% confidence level. The wave-breaking characteristics during the NAM life cycle are also examined. Both the positive and negative NAM phases yield the same wave-breaking properties as those for the NAO.

The results suggest that not only are the NAO and NAM persistent events indistinguishable, but that the NAO/NAM events are neither confined to the North Atlantic, nor are they annular.
The Evolution of Dispersion Spectra and the Evaluation of Model Differences in an Ensemble Estimation of Error Statistics for a Limited-Area Analysis
Authors: Ştefănescu Simona Ecaterina , Berre Loïk , Pereira Margarida Belo
Published: November 2006

An ensemble of limited-area forecasts has been obtained by integrating the Aire Limitée Adaptation Dynamique Développement International (ALADIN) limited-area model, in cold-starting mode, from an ensemble of Action de Recherche Petite Echelle Grande Echelle (ARPEGE) global analyses and forecasts. This permits error covariances of the ALADIN 6-h forecast and of the ARPEGE analysis to be estimated. These two fields may be combined in a future ALADIN analysis.

The evolution of dispersion spectra is first studied in a perfect model framework. The ARPEGE analysis reduces the large-scale dispersion of the ARPEGE background by extracting some information from observations. Then, the digital filter initialization reduces the small-scale dispersion by removing the noise caused by interpolation of the ARPEGE analysis onto the ALADIN grid. Finally, the ALADIN 6-h forecast strongly increases the small-scale dispersion, in accordance with its ability to represent small-scale processes.

Some model error contributions are then studied. The variances of the differences between the ALADIN and ARPEGE forecasts, which are started from the same ARPEGE analysis, are of smaller scale than are the ALADIN and ARPEGE perfect model dispersions. The small-scale part of these ARPEGE–ALADIN model differences is shown to correspond to structures that are represented by ALADIN and not by ARPEGE. Therefore, this part may be added to the ARPEGE analysis dispersion. The residual large-scale part is more ambiguous, but it may be added to the ALADIN dispersion; this may reflect some effects of the coupling inaccuracies, and strengthen (in a future ALADIN analysis) the use of the large-scale information from the ARPEGE analysis.
Application of Principal Component Analysis to CHAMP Radio Occultation Data for Quality Control and a Diagnostic Study
Authors: Zeng Zhen , Zou X.
Published: November 2006

A principal component analysis (PCA) method is applied to Challenging Minisatellite Payload (CHAMP) level-2 radio occultation (RO) observations and the corresponding global analyses from the National Centers for Environmental Prediction (NCEP) in March 2004. The PCA is performed on a square symmetric vertical correlation matrix of observed or modeled RO profiles. By decomposing the matrix into pairs of loadings (EOFs) and associated principal components (PCs), outliers are identified and important modes that explain most variances of the vertical variability of the atmosphere as represented by the GPS RO data and the NCEP analyses are extracted and compared. Specifically, a quality control of RO data based on Hotelling’s T 2 index is applied first, which removes 255 RO profiles from 4884 total profiles (about 5%) and smoothes the distributions of PC modes, making the remaining GPS RO dataset much more meaningful. The leading PC mode for global refractivity explains 60% of the total variance and is associated with a symmetric zonal pattern, with positive anomalies in the Tropics and negative anomalies at the two poles. The second PC mode explains an additional 16% of the total variance and shows a dipole pattern with positive anomalies in the North Pole and negative anomalies in the South Pole. Three significant positive anomalies are also found in the second and third PC modes over three predominant convective areas in the western Pacific, South America, and Africa in the Tropics. The first leading PC mode calculated from global NCEP analyses compared favorably with that from CHAMP observations, which proves that NCEP analyses are capable of representing most of the variance of the atmospheric profiles. However, disagreements between CHAMP observations and NCEP analyses are noticed in the second EOF over the Tropics and the Southern Hemisphere (SH). It is also found that the NCEP analyses describe CHAMP-observed larger vertical scale features better than smaller-scale features, captures features of more leading EOF modes in the Northern Hemisphere than in the SH and the Tropics, and does not capture the vertical structures revealed by the EOFs in CHAMP observations near and above the tropopause in the Tropics.
Evaluation of Operational Model Cyclone Structure Forecasts during Extratropical Transition
Authors: Evans Jenni L. , Arnott Justin M. , Chiaromonte Francesca
Published: November 2006

Cyclone structure is known to be directly linked to the sensible weather effects produced by the weather system. The extratropical transition (ET) process leads to immense changes in cyclone structure and therefore to changes in the associated weather experienced. Although structure is clearly an important cyclone characteristic, validation of cyclone structure forecasts in operational numerical models has not been previously performed. In this study, short-term (12–36 h) forecasts of cyclone structure from tropical genesis to the completion of ET are validated using fields from the Navy Operational Global Atmospheric Prediction System and the NCEP Aviation model. The cyclone phase space (CPS) is used to quantify differences between forecast and analyzed storm structure, both on a point-by-point basis and through a cyclone-type-based comparison. This cyclone-type comparison exploits a previously defined breakdown of cyclone structure regimes in the CPS. The impacts of synthetic vortex insertion on the ensuing agreement between forecast and analyzed storm structure are explored. While the results show reasonable forecast skill for well-defined (i.e., nonhybrid) systems, cyclones in the process of ET are found to be poorly forecast, emphasizing the need for improved understanding and simulation of the structural changes experienced by ET cyclones.
The Behavior of Synoptic-Scale Errors in the Eta Model
Authors: Elmore Kimberly L. , Schultz David M. , Baldwin Michael E.
Published: November 2006

A previous study of the mean spatial bias errors associated with operational forecast models motivated an examination of the mechanisms responsible for these biases. One hypothesis for the cause of these errors is that mobile synoptic-scale phenomena are partially responsible. This paper explores this hypothesis using 24-h forecasts from the operational Eta Model and an experimental version of the Eta run with Kain–Fritsch convection (EtaKF).

For a sample of 44 well-defined upper-level short-wave troughs arriving on the west coast of the United States, 70% were underforecast (as measured by the 500-hPa geopotential height), a likely result of being undersampled by the observational network. For a different sample of 45 troughs that could be tracked easily across the country, consecutive model runs showed that the height errors associated with 44% of the troughs generally decreased in time, 11% increased in time, 18% had relatively steady errors, 2% were uninitialized entering the West Coast, and 24% exhibited some other kind of behavior. Thus, landfalling short-wave troughs were typically underforecast (positive errors, heights too high), but these errors tended to decrease as they moved across the United States, likely a result of being better initialized as the troughs became influenced by more upper-air data. Nevertheless, some errors in short-wave troughs were not corrected as they fell under the influence of supposedly increased data amount and quality. These results indirectly show the effect that the amount and quality of observational data has on the synoptic-scale errors in the models. On the other hand, long-wave ridges tended to be underforecast (negative errors, heights too low) over a much larger horizontal extent.

These results are confirmed in a more systematic manner over the entire dataset by segregating the model output at each grid point by the sign of the 500-hPa relative vorticity. Although errors at grid points with positive relative vorticity are small but positive in the western United States, the errors become large and negative farther east. Errors at grid points with negative relative vorticity, on the other hand, are generally negative across the United States. A large negative bias observed in the Eta and EtaKF over the southeast United States is believed to be due to an error in the longwave radiation scheme interacting with water vapor and clouds. This study shows that model errors may be related to the synoptic-scale flow, and even large-scale features such as long-wave troughs can be associated with significant large-scale height errors.
Low-Level Convergence Lines over Northeastern Australia. Part I: The North Australian Cloud Line
Authors: Goler Robert , Reeder Michael J. , Smith Roger K. , Richter Harald , Arnup Sarah , Keenan Tom , May Peter , Hacker Jorg
Published: November 2006

Observations of dry-season north Australian cloud lines (NACLs) that form in the Gulf of Carpentaria region of northern Australia and the sea-breeze circulations that initiate them are described. The observations were made during the 2002 Gulf Lines Experiment (GLEX) and include measurements made by an instrumented research aircraft. The observations are compared with numerical simulations made from a two-dimensional cloud-scale model. Particular emphasis is placed on the interaction between the east coast and west coast sea breezes near the west coast of Cape York Peninsula. The sea breezes are highly asymmetric due to the low-level easterly synoptic flow over the peninsula. The west coast sea breeze is well defined with a sharp leading edge since the opposing flow limits its inland penetration, keeping it close to its source of cold air. In contrast, the east coast sea breeze is poorly defined since it is aided by the easterly flow and becomes highly modified by daytime convective mixing as it crosses over the peninsula. Both the observations and the numerical model show that, in the early morning hours, the mature NACL forms at the leading edge of a gravity current. The numerical model simulations show that this gravity current arises as a westward-moving land breeze from Cape York Peninsula. Convergence at the leading edge of this land breeze is accompanied by ascent, which when strong enough produces cloud. Observations show that the decay of the NACL is associated with a decline in the low-level convergence and a weakening of the ascent.
Assessing the Impact of Simulated COSMIC GPS Radio Occultation Data on Weather Analysis over the Antarctic: A Case Study
Authors: Cucurull L. , Kuo Y-H. , Barker D. , Rizvi S. R. H.
Published: November 2006

The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission was launched in April 2006. As part of its mission, COSMIC will provide approximately 2500–3000 global positioning system (GPS) radio occultation (RO) soundings per day distributed uniformly around the globe. In this study, a series of sensitivity experiments are conducted to assess the potential impact of COSMIC GPS RO data on the regional weather analysis over the Antarctic. Soundings of refractivity are assimilated into the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model using its three-dimensional variational data assimilation system. First, the sensitivity of the analysis to the background error statistics and balance constraints is analyzed. Then the effects of the data distribution and the observational error of the simulated refractivity observations are examined. In this study, the simulated soundings are based on a realistic set of orbit parameters of the COSMIC constellation. Analysis of the assimilation results indicates the significant potential impact of COSMIC data on regional analyses over the Antarctic. In the one case studied here, the root-mean-square differences between the background and observed values are reduced by 12% in the horizontal wind component, 17% in the temperature variable, 8% in the specific humidity, and 22% in the pressure field when COSMIC GPS RO data are assimilated into the system by using a 6-h assimilation time window. These preliminary results suggest that COSMIC GPS RO data can have a significant impact on operational numerical weather analysis in the Antarctic.
A Singular Vector Perspective of 4DVAR: The Spatial Structure and Evolution of Baroclinic Weather Systems
Authors: Johnson Christine , Hoskins Brian J. , Nichols Nancy K. , Ballard Susan P.
Published: November 2006

The extent to which the four-dimensional variational data assimilation (4DVAR) is able to use information about the time evolution of the atmosphere to infer the vertical spatial structure of baroclinic weather systems is investigated. The singular value decomposition (SVD) of the 4DVAR observability matrix is introduced as a novel technique to examine the spatial structure of analysis increments. Specific results are illustrated using 4DVAR analyses and SVD within an idealized 2D Eady model setting. Three different aspects are investigated. The first aspect considers correcting errors that result in normal-mode growth or decay. The results show that 4DVAR performs well at correcting growing errors but not decaying errors. Although it is possible for 4DVAR to correct decaying errors, the assimilation of observations can be detrimental to a forecast because 4DVAR is likely to add growing errors instead of correcting decaying errors. The second aspect shows that the singular values of the observability matrix are a useful tool to identify the optimal spatial and temporal locations for the observations. The results show that the ability to extract the time-evolution information can be maximized by placing the observations far apart in time. The third aspect considers correcting errors that result in nonmodal rapid growth. 4DVAR is able to use the model dynamics to infer some of the vertical structure. However, the specification of the case-dependent background error variances plays a crucial role.
Effects of Vertical Wind Shear and Storm Motion on Tropical Cyclone Rainfall Asymmetries Deduced from TRMM
Authors: Chen Shuyi S. , Knaff John A. , Marks Frank D.
Published: November 2006

Vertical wind shear and storm motion are two of the most important factors contributing to rainfall asymmetries in tropical cyclones (TCs). Global TC rainfall structure, in terms of azimuthal distribution and asymmetries relative to storm motion, has been previously described using the Tropical Rainfall Measuring Mission Microwave Imager rainfall estimates. The mean TC rainfall distribution and the wavenumber-1 asymmetry vary with storm intensity and geographical location among the six oceanic basins. This study uses a similar approach to investigate the relationship between the structure of TC rainfall and the environmental flow by computing the rainfall asymmetry relative to the vertical wind shear. The environmental vertical wind shear is defined as the difference between the mean wind vectors of the 200- and 850-hPa levels over an outer region extending from the radius of 200–800 km around the storm center. The wavenumber-1 maximum rainfall asymmetry is downshear left (right) in the Northern (Southern) Hemisphere. The rainfall asymmetry decreases (increases) with storm intensity (shear strength). The rainfall asymmetry maximum is predominantly downshear left for shear values > 7.5 m s−1. Large asymmetries are usually observed away from the TC centers. As TC intensity increases, the asymmetry maximum shifts upwind to the left. The analysis is further extended to examine the storm motion and the vertical wind shear and their collective effects on TC rainfall asymmetries. It is found that the vertical wind shear is a dominant factor for the rainfall asymmetry when shear is >5 m s−1. The storm motion–relative rainfall asymmetry in the outer rainband region is comparable to that of shear relative when the shear is <5 m s−1, suggesting that TC translation speed becomes an important factor in the low shear environment. The overall TC rainfall asymmetry depends on the juxtaposition and relative magnitude of the storm motion and environmental shear vectors in all oceanic basins.