bluuebunny/crossref_metadata_2025 huggingface dataset:
Transcriptional Inhibition of Protease-Activated Receptor-1 Expression by Prostacyclin in Human Vascular Smooth Muscle Cells
Authors: Pape Robert , Rauch Bernhard H. , Rosenkranz Anke C. , Kaber Gernot , Schrör Karsten
Published: December 2007

Objective—

Stimulation of protease-activated receptor-1 (PAR-1) by thrombin causes vascular smooth muscle cell (SMC) mitogenesis and has been implicated in the vascular response to injury. Vascular injury is also associated with enhanced formation of PGE
2
and PGI
2
(prostacyclin). This study investigates whether PGI
2
and PGE
2
modify the expression of PAR-1 and the cellular response to thrombin in human SMC.

Methods and Results—

The PGI
2
-mimetic iloprost (1 to 100 nmol/L) attenuated mRNA, total protein, and cell surface expression of PAR-1. This was associated with inhibition of thrombin-induced mitogenesis and migration. Comparable inhibition of PAR-1 expression was observed with the selective IP-receptor agonist cicaprost, the adenylyl cyclase activator forskolin, the phosphodiesterase inhibitor isobutylmethylxanthine and the PKA activator dibutyryl-cAMP. Similar effects of PGE
2
required micromolar concentrations. The specific PKA-inhibitor Myr-PKI prevented PAR-1 downregulation by iloprost. The potential role of Rho family GTPases in PAR-1 regulation was also investigated. Iloprost decreased Rac1 mRNA and the Rac1 inhibitor NSC23766 mimicked the inhibitory effects of iloprost on PAR-1 protein—but not mRNA. The Rho kinase inhibitor Y27632 did not influence PAR-1 expression.

Conclusions—

IP-receptor agonists may limit the mitogenic actions of thrombin in human SMC by downregulating PAR-1 via modulation of cAMP-/PKA- and Rac1-dependent signaling pathways.
Critical Role of Lipid Raft Redox Signaling Platforms in Endostatin-Induced Coronary Endothelial Dysfunction
Authors: Jin Si , Zhang Yang , Yi Fan , Li Pin-Lan
Published: December 2007

Objective—

Endostatin (EST) was found to initiate a redox signaling cascade associated with activation of NADPH oxidase in endothelial cells (ECs). The present study tested whether EST stimulates clustering of ceramide-enriched lipid rafts (LRs), which assembles and activates NADPH oxidase to form redox signaling platforms.

Methods and Results—

Using confocal microscopy, we first demonstrated a colocalization of LR clusters with NADPH oxidase subunits, gp91

phox

and p47

phox

in the ECs membrane on EST stimulation. Immunoblot analysis of floated detergent-resistant membrane fractions found that in LR fractions NADPH oxidase subunits gp91

phox

and p47

phox

are enriched and that the activity of this enzyme increased dramatically, as measured by electron spin resonance (ESR) spectrometry. This EST-increased LR platform formation was shown to be attenuated by inhibition or RNA interference of acid sphingomyelinase (A-SMase). Functionally, EST pretreatment significantly impaired bradykinin or A23187-induced vasodilation in isolated small coronary arteries, which could be partially reversed by LR disruptors.

Conclusions—

The early injury effect of EST on the vascular endothelium is associated with the formation of redox signaling platforms via lipid raft clustering.
Cognitive Outcome at Early School Age in Term-Born Children With Perinatally Acquired Middle Cerebral Artery Territory Infarction
Authors: Ricci Daniela , Mercuri Eugenio , Barnett Anna , Rathbone Rachel , Cota Francesco , Haataja Leena , Rutherford Mary , Dubowitz Lilly , Cowan Frances
Published: December 2007

Background and Purpose—

To assess cognitive outcome at early school age in term-born children with middle cerebral arterial (MCA) territory infarction of perinatal onset and examine the correlation between cognitive abilities and the extent of lesions as seen on neonatal MRI, epilepsy, and hemiplegia.

Methods—

Thirty-one children were seen as newborns with an acutely evolving MCA territory infarction documented on neonatal MRI scan. IQ was assessed (WIPPSI/WISC where appropriate) and they had a standardized neurological examination at early school age. Lesion(s) site was recorded from the neonatal images.

Results—

Twenty-eight of 31 children were assessed (median age 5.75 range 5.33 to 10.33 years); 1 child died and 2 were abroad. IQ was within the normal range (mean 104, range 82 to 144) in 21 (78%); 1 child did not complete all tests but had a normal PIQ; 3 had a low and 3 an exceptionally low IQ. Verbal IQs were more varied and lower than performance IQs especially in children from multilingual backgrounds. There was no consistent association between cognitive impairment, side, or extent of the MCA lesion. Cognitive impairments were more frequent in children with seizures or hemiplegia. All 6 children with low IQ also had behavioral problems or unusual associated clinical or scan features.

Conclusions—

In our cohort a low IQ at early school age did not occur in children with the common presentation of neonatal unilateral MCA territory infarction. Cognitive impairment appeared more frequently when an MCA arterial territory infarction, even if relatively small, was associated with other risk factors.
Predicting Stroke Risk in Hypertensive Patients With Coronary Artery Disease
Authors: Coca Antonio , Messerli Franz H. , Benetos Athanase , Zhou Qian , Champion Annette , Cooper-DeHoff Rhonda M. , Pepine Carl J.
Published: December 2007

Background and Purpose—

Our understanding of factors influencing stroke risk among patients with coronary artery disease is incomplete. Accordingly, factors predicting stroke risk in hypertensive, clinically stable coronary artery disease patients were determined with data from the INternational VErapamil SR-trandolapril STudy (INVEST).

Methods—

The effect of baseline characteristics and on-treatment blood pressure (BP) were analyzed to determine the risk of stroke (fatal or nonfatal) among the 22 576 patients enrolled. Cox proportional-hazards models (unadjusted, adjusted, and time dependent) were used to identify predictors of stroke among subgroups with these characteristics present at entry and on-treatment BP.

Results—

Excellent BP control (at 24 months, >70% <140/90 mm Hg) was achieved during 61 835 patient-years of follow-up, as 377 patients had a stroke (6.1 strokes/1000 patient-years) and 28% of those patients had a fatal stroke. Increased age, black race, US residency, and history of prior myocardial infarction, smoking, stroke/transient ischemic attack, arrhythmia, diabetes, and coronary bypass surgery were associated with an increased risk of stroke. Achieving a systolic BP <140 mm Hg and a diastolic BP <90 mm Hg was associated with a decreased risk of stroke. There was no statistically significant difference in stroke risk comparing the verapamil SR–based with the atenolol-based treatment strategy (adjusted hazard ratio=0.87; 95% CI, 0.71 to 1.06;
P
=0.17).

Conclusions—

Among hypertensive patients with chronic coronary artery disease, stroke was an important complication associated with significant mortality. Black race, US residency, and conditions associated with increased vascular disease severity and arrhythmia predicted increased stroke risk, whereas achieving a BP <140/90 mm Hg on treatment predicted a reduced stroke risk.
Landslide Erosion Rate in the Eastern Cordillera of Northern Bolivia
Authors: Blodgett Troy A. , Isacks Bryan L.
Published: December 2007

The northeastern edge of the Bolivian Eastern Cordillera is an example of a tectonically active plateau margin where orographically enhanced precipitation facilitates very high rates of erosion. The topography of the steepest part of the margin exhibits the classic signature of high erosion rates consisting of high-relief V-shaped valleys where landsliding is the dominant process of hillslope erosion and bedrock rivers are incising into the landscape. The authors mapped landslide scars on multitemporal aerial photographs to estimate hillslope erosion rates. Field surveys of landslide scars are used to calibrate a landslide volume versus area relationship. The mapped area of landsliding, in combination with an estimate of the time for landslide scars to revegetate, leads to an erosion rate estimate. The estimated revegetation time, 10–35 yr, is based on analysis of multitemporal aerial photographs and tree rings. About 4%–6% of two watersheds in the region considered were affected by landslides over the last 10–35 yr. This result implies an erosion rate of 9 ± 5 mm yr−1 assuming that 90% of a single landslide reaches the river on average. Classified Landsat Thematic Mapper images show that landslides are occurring at approximately the same rate all across an approximately 40-km-wide swath within the high-relief zones of the cordillera.
On the Interaction of Jupiter’s Great Red Spot and Zonal Jet Streams
Authors: Shetty Sushil , Asay-Davis Xylar S. , Marcus Philip S.
Published: December 2007

In this paper, Jupiter’s Great Red Spot (GRS) is used to determine properties of the Jovian atmosphere that cannot otherwise be found. These properties include the potential vorticity of the GRS and its neighboring jet streams, the shear imposed on the GRS by the jet streams, and the vertical entropy gradient (i.e., Rossby deformation radius). The cloud cover of the GRS, which is often used to define the GRS’s area and aspect ratio, is found to differ significantly from the region of the GRS’s potential vorticity anomaly. The westward-going jet stream to the north of the GRS and the eastward-going jet stream to its south are each found to have a large potential vorticity “jump.” The jumps have opposite signs, and as a consequence of their interaction with the GRS, the shear imposed on the GRS is reduced. The aspect ratio of the GRS’s potential vorticity anomaly depends on the ratio of the imposed shear to the strength of the anomaly. The east–west to north–south aspect ratio is found to be ∼2:1, but without the opposing jumps it would be much greater. The GRS’s high-speed collar and quiescent interior require that the potential vorticity in the interior be approximately half that in the collar. No other persistent geophysical vortex has a significant local minimum of potential vorticity in its interior, and laboratory vortices with such a minimum are unstable.
Seasonality and Regionality of the Madden–Julian Oscillation, Kelvin Wave, and Equatorial Rossby Wave
Authors: Masunaga Hirohiko
Published: December 2007

The Madden–Julian oscillation (MJO), Kelvin wave, and equatorial Rossby (ER) wave—collectively called intraseasonal oscillations (ISOs)—are investigated using a 25-yr record of outgoing longwave radiation (OLR) measurements as well as the associated dynamical fields. The ISO modes are detected by applying bandpass filters to the OLR data in the frequency–wavenumber space. An automated wave-tracking algorithm is applied to each ISO mode so that convection centers accompanied with the ISOs are traced in space and time in an objective fashion. The identified paths of the individual ISO modes are first examined and found strongly modulated regionally and seasonally. The dynamical structure is composited with respect to the convection centers of each ISO mode. A baroclinic mode of the combined Rossby and Kelvin structure is prominent for the MJO, consistent with existing work. The Kelvin wave exhibits a low-level wind field resembling the shallow-water solution, while a slight lead of low-level convergence over convection suggests the impact of frictional boundary layer convergence on Kelvin wave dynamics. A lagged composite analysis reveals that the MJO is accompanied with a Kelvin wave approaching from the west preceding the MJO convective maximum in austral summer. MJO activity then peaks as the Kelvin and ER waves constructively interfere to enhance off-equatorial boundary layer convergence. The MJO leaves a Kelvin wave emanating to the east once the peak phase is passed. The approaching Kelvin wave prior to the development of MJO convection is absent in boreal summer and fall. The composite ER wave, loosely concentrated around the MJO, is nearly stationary throughout. A possible scenario to physically translate the observed result is also discussed.
A Tropical and Subtropical Land–Sea–Atmosphere Drought Oscillation Mechanism
Authors: Abbot Dorian S. , Emanuel Kerry A.
Published: December 2007

A two-column atmospheric model on a land–sea interface is studied. The model has sophisticated convection, cloud, and radiation schemes, a mixed layer ocean, and a bucket model to simulate land hydrology. A self-sustained oscillation in soil moisture with a period on the order of months is found. This oscillation is strongest when the model is run with parameters chosen to correspond to the arid subtropics. The effect of changing model parameters on the oscillation is explored. The existence and qualitative behavior of the oscillation are relatively robust to changes in model parameters.
Rossby Waves and Jets in Two-Dimensional Decaying Turbulence on a Rotating Sphere
Authors: Hayashi Yoshi-Yuki , Nishizawa Seiya , Takehiro Shin-ichi , Yamada Michio , Ishioka Keiichi , Yoden Shigeo
Published: December 2007

Jet formation in decaying two-dimensional turbulence on a rotating sphere is reviewed from the viewpoint of Rossby waves. A series of calculations are performed to confirm the behavior of zonal mean flow generation on the parameter space of the rotation rate Ω and Froude number Fr. When the flow is nondivergent and Ω is large, intense easterly circumpolar jets tend to emerge in addition to the appearance of a banded structure of zonal mean flows with alternating flow directions. When the system allows surface elevation, circumpolar jets disappear and an equatorial easterly jet emerges with increasing Fr. The appearance of the intense easterly jets can be understood by the angular-momentum transport associated with the generation, propagation, and absorption of Rossby waves. When the flow is nondivergent, long Rossby waves tend to be absorbed near the poles. In contrast, when Fr is large, Rossby waves can hardly propagate poleward and tend to be absorbed near the equator.
Generalized Stability of Nongeostrophic Baroclinic Shear Flow. Part II: Intermediate Richardson Number Regime
Authors: Heifetz Eyal , Farrell Brian F.
Published: December 2007

This work continues the generalized stability theory (GST) analysis of baroclinic shear flow in the primitive equations (PE), focusing on the regime in which the mean baroclinic shear and the stratification are of the same order. The Eady model basic state is used and solutions obtained using the PE are compared to quasigeostrophic (QG) solutions.

Similar optimal growth is obtained in the PE and QG frameworks for eddies with horizontal scale equal to or larger than the Rossby radius, although PE growth rates always exceed QG growth rates. The primary energy growth mechanism is the conventional baroclinic conversion of mean available potential energy to perturbation energy mediated by the eddy meridional heat flux. However, for eddies substantially smaller than the Rossby radius, optimal growth rates in the PE greatly exceed those found in the QG. This enhanced growth rate in the PE is dominated by conversion of mean kinetic energy to perturbation kinetic energy mediated by the vertical component of zonal eddy momentum flux. This growth mechanism is filtered in QG. In the intermediate Richardson number regime mixed Rossby–gravity modes are nonorthogonal in energy, and these participate in the process of energy transfer from the barotropic source in the mean shear to predominantly baroclinic waves during the transient growth process.

The response of shear flow in the intermediate Richardson number regime to spatially and temporally uncorrelated stochastic forcing is also investigated. It is found that a comparable amount of shear turbulent variance is maintained in the rotational and mixed Rossby–gravity modes by such unbiased forcing suggesting that any observed dominance of rotational mode energy arises from restrictions on the effective forcing and damping.
Mean Climate and Variability of the Atmosphere and Ocean on an Aquaplanet
Authors: Marshall John , Ferreira David , Campin J-M. , Enderton Daniel
Published: December 2007

Numerical experiments are described that pertain to the climate of a coupled atmosphere–ocean–ice system in the absence of land, driven by modern-day orbital and CO2 forcing. Millennial time-scale simulations yield a mean state in which ice caps reach down to 55° of latitude and both the atmosphere and ocean comprise eastward- and westward-flowing zonal jets, whose structure is set by their respective baroclinic instabilities. Despite the zonality of the ocean, it is remarkably efficient at transporting heat meridionally through the agency of Ekman transport and eddy-driven subduction. Indeed the partition of heat transport between the atmosphere and ocean is much the same as the present climate, with the ocean dominating in the Tropics and the atmosphere in the mid–high latitudes. Variability of the system is dominated by the coupling of annular modes in the atmosphere and ocean. Stochastic variability inherent to the atmospheric jets drives variability in the ocean. Zonal flows in the ocean exhibit decadal variability, which, remarkably, feeds back to the atmosphere, coloring the spectrum of annular variability. A simple stochastic model can capture the essence of the process. Finally, it is briefly reviewed how the aquaplanet can provide information about the processes that set the partition of heat transport and the climate of Earth.
Large-Eddy Simulation of the Onset of the Sea Breeze
Authors: Antonelli M. , Rotunno R.
Published: December 2007

This paper describes results from a large-eddy simulation (LES) model used in an idealized setting to simulate the onset of the sea breeze. As the LES is capable of simulating boundary layer–scale, three-dimensional turbulence along with the mesoscale sea-breeze circulation, a parameterization of the planetary boundary layer was unnecessary. The basic experimental design considers a rotating, uniformly stratified, resting atmosphere that is suddenly heated at the surface over the “land” half of the domain. To focus on the simplest nontrivial problem, the diurnal cycle, effects of moisture, interactions with large-scale winds, and coastline curvature were all neglected in this study. The assumption of a straight coastline allows the use of a rectangular computational domain that extends to 50 km on either side of the coast, but only 5 km along the coast, with 100-m grid intervals so that the small-scale turbulent convective eddies together with the mesoscale sea breeze may be accurately computed. Through dimensional analysis of the simulation results, the length and velocity scales characterizing the simulated sea breeze as functions of the externally specified parameters are identified.
Numerical Simulation of Baroclinic Waves with a Parameterized Boundary Layer
Authors: Plant R. S. , Belcher S. E.
Published: December 2007

A dry three-dimensional baroclinic life cycle model is used to investigate the role of turbulent fluxes of heat and momentum within the boundary layer on midlatitude cyclones. Simulations are performed of life cycles for two basic states: with and without turbulent fluxes. The different basic states produce cyclones with contrasting frontal and mesoscale flow structures. The analysis focuses on the generation of potential vorticity (PV) in the boundary layer and its subsequent transport into the free troposphere. The dynamic mechanism through which friction mitigates a barotropic vortex is that of Ekman pumping. This has often been assumed to also be the dominant mechanism for baroclinic developments. The PV framework highlights an additional, baroclinic mechanism. Positive PV is generated baroclinically due to friction to the northeast of a surface low and is transported out of the boundary layer by a cyclonic conveyor belt flow. The result is an anomaly of increased static stability in the lower troposphere, which restricts the growth of the baroclinic wave. The reduced coupling between lower and upper levels can be sufficient to change the character of the upper-level evolution of the mature wave. The basic features of the baroclinic damping mechanism are robust for different frontal structures, with and without turbulent heat fluxes, and for the range of surface roughness found over the oceans.
Use of High-Resolution Satellite Observations to Evaluate Cloud and Precipitation Statistics from Cloud-Resolving Model Simulations. Part I: South China Sea Monsoon Experiment
Authors: Zhou Y. P. , Tao W.-K. , Hou A. Y. , Olson W. S. , Shie C.-L. , Lau K.-M. , Chou M.-D. , Lin X. , Grecu M.
Published: December 2007

Cloud and precipitation simulated using the three-dimensional (3D) Goddard Cumulus Ensemble (GCE) model are compared to Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and Precipitation Radar (PR) rainfall measurements and Clouds and the Earth’s Radiant Energy System (CERES) single scanner footprint (SSF) radiation and cloud retrievals. Both the model simulation and retrieved parameters are based upon observations made during the South China Sea Monsoon Experiment (SCSMEX) field campaign. The model-simulated cloud and rain systems are evaluated by systematically examining important parameters such as the surface rain rate, convective/stratiform percentage, rain profiles, cloud properties, and precipitation efficiency.

It is demonstrated that the GCE model is capable of simulating major convective system development and reproduces the total surface rainfall amount as compared to rainfall estimated from the SCSMEX sounding network. The model yields a slightly higher total convective rain/stratiform rain ratio than the TMI and PR observations. The GCE rainfall spectrum exhibits a greater contribution from heavy rains than those estimated from PR or TMI observations. In addition, the GCE simulation produces much greater amounts of snow and graupel than the TRMM retrievals. The model’s precipitation efficiency of convective rain is close to the observations, but the precipitation efficiency of stratiform rain is much lower than the observations because of large amounts of slowly falling simulated snow and graupel. Compared to observations, the GCE produces more compact areas of intense convection and less anvil cloud, which are consistent with a smaller total cloud fraction and larger domain-averaged outgoing longwave radiation.
Is a Real Cyclogenesis Case Explained by Generalized Linear Baroclinic Instability?
Authors: Descamps L. , Ricard D. , Joly A. , Arbogast P.
Published: December 2007

Midlatitude cyclogenesis is currently often explained as resulting from the baroclinic instability of a jet flow. The present formulation of the theory, essentially resulting from the deep revision performed by Farrell, associates incipient cyclones with amplifying singular vectors of a linear propagator operator obtained by linearizing the relevant model equations (balanced or not) about a trajectory representing the jet flow alone. A major difficulty for transposing the theoretical framework to a real case, and then opening the way to quantitative verifications of the theory, is this separation of an actual realization of cyclogenesis into the cyclone as a perturbation on one side and its environment on the other. A methodology to obtain such a separation in a reasonably objective and dynamically consistent way is presented. It enables obtaining two diabatic primitive equation solutions about the 26 December 1999 intense storm, one that has the event and the other that has most of the characteristics of the exceptional baroclinic environment of that case, except the storm itself. It is then possible to employ the theoretical framework without further approximation and to compare the predicted unstable modes with the storm representing itself as a perturbation. Two aspects of the theory are especially studied. One is a comparison of the properties of the real and predicted systems, focusing on their structures. The other deals with the idea that precursor structures, although very different from the theoretical modes, trigger the cyclogenesis by exciting these modes. It appears that the classical predictions (scales, etc.) of such a theory are, for most of them, far away from the observed properties. It is clear that the structure of a singular vector has little to share with that of a real cyclone. Yet, a weaker, slower storm does occur as a result of applying the theory to the stormless trajectory.
On the Occurrence of Hollow Bullet Rosette– and Column-Shaped Ice Crystals in Midlatitude Cirrus
Authors: Schmitt C. G. , Heymsfield A. J.
Published: December 2007

Cirrus clouds in mid- and high latitudes are frequently composed of bullet rosette– and column-shaped ice crystals, which can have hollow ends. Bullet rosette–shaped ice crystals are composed of a number of bullets radiating from a central point. Research has shown that the light-scattering properties of ice particles with hollow ends are different from the scattering properties of solid ice particles. Knowledge of the frequency of occurrence of hollow particles is important to more accurately calculate the radiative properties of cirrus clouds.

This note presents the results of a survey of cirrus cloud ice crystal replicas imaged from balloon-borne Formvar (polyvinyl formal) replicators. Fifty percent to 80% of the replicated bullet rosette– and column-shaped particles had hollow ends. In bullets longer than 150 μm in length, the length of the hollows of the bullets averaged 88% of the total length of the bullet. The combined length of both hollow portions of column-shaped ice crystals varied from 50% of the length of the column for 30-μm-long columns to 80% of the length of the columns longer than 200 μm. Asymmetry parameter values estimated from cirrus cloud aircraft particle size distributions are higher by 0.014 when hollow crystals are considered. This difference leads to a 2.5 W m−2 increase for hollow crystals at the surface for a 0.5 optical depth cloud, demonstrating the importance of the incorporation of hollow particle scattering characteristics into radiative transfer calculations.
The Spacing of Orographic Rainbands Triggered by Small-Scale Topography
Authors: Kirshbaum Daniel J. , Rotunno Richard , Bryan George H.
Published: December 2007

A combination of idealized numerical simulations and analytical theory is used to investigate the spacing between convective orographic rainbands over the Coastal Range of western Oregon. The simulations, which are idealized from an observed banded precipitation event over the Coastal Range, indicate that the atmospheric response to conditionally unstable flow over the mountain ridge depends strongly on the subridge-scale topographic forcing on the windward side of the ridge. When this small-scale terrain contains only a single scale (λ) of terrain variability, the band spacing is identical to λ, but when a spectrum of terrain scales are simultaneously present, the band spacing ranges between 5 and 10 km, a value that is consistent with observations. Based on the simulations, an inviscid linear model is developed to provide a physical basis for understanding the scale selection of the rainbands. This analytical model, which captures the transition from lee waves upstream of the orographic cloud to moist convection within it, reveals that the spacing of orographic rainbands depends on both the projection of lee-wave energy onto the unstable cap cloud and the growth rate of unstable perturbations within the cloud. The linear model is used in tandem with numerical simulations to determine the sensitivity of the band spacing to a number of environmental and terrain-related parameters.
Snow Size Distribution Parameterization for Midlatitude and Tropical Ice Clouds
Authors: Field Paul R. , Heymsfield Andrew J. , Bansemer Aaron
Published: December 2007

Many microphysical process rates involving snow are proportional to moments of the snow particle size distribution (PSD), and in this study a moment estimation parameterization applicable to both midlatitude and tropical ice clouds is proposed. To this end aircraft snow PSD data were analyzed from tropical anvils [Tropical Rainfall Measuring Mission/Kwajelein Experiment (TRMM/KWAJEX), Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE)] and midlatitude stratiform cloud [First International Satellite Cloud Climatology Project Research Experiment (FIRE), Atmospheric Radiation Measurement Program (ARM)]. For half of the dataset, moments of the PSDs are computed and a parameterization is generated for estimating other PSD moments when the second moment (proportional to the ice water content when particle mass is proportional to size squared) and temperature are known. Subsequently the parameterization was tested with the other half of the dataset to facilitate an independent comparison. The parameterization for estimating moments can be applied to midlatitude or tropical clouds without requiring prior knowledge of the regime of interest. Rescaling of the tropical and midlatitude size distributions is presented along with fits to allow the user to recreate realistic PSDs given estimates of ice water content and temperature. The effects of using different time averaging were investigated and were found not to be adverse. Finally, the merits of a single-moment snow microphysics versus multimoment representations are discussed, and speculation on the physical differences between the rescaled size distributions from the Tropics and midlatitudes is presented.
Inertia–Gravity Waves Generated within a Dipole Vortex
Authors: Snyder Chris , Muraki David J. , Plougonven Riwal , Zhang Fuqing
Published: December 2007

Vortex dipoles provide a simple representation of localized atmospheric jets. Numerical simulations of a synoptic-scale dipole in surface potential temperature are considered in a rotating, stratified fluid with approximately uniform potential vorticity. Following an initial period of adjustment, the dipole propagates along a slightly curved trajectory at a nearly steady rate and with a nearly fixed structure for more than 50 days. Downstream from the jet maximum, the flow also contains smaller-scale, upward-propagating inertia–gravity waves that are embedded within and stationary relative to the dipole. The waves form elongated bows along the leading edge of the dipole. Consistent with propagation in horizontal deformation and vertical shear, the waves’ horizontal scale shrinks and the vertical slope varies as they approach the leading stagnation point in the dipole’s flow. Because the waves persist for tens of days despite explicit dissipation in the numerical model that would otherwise damp the waves on a time scale of a few hours, they must be inherent features of the dipole itself, rather than remnants of imbalances in the initial conditions. The wave amplitude varies with the strength of the dipole, with waves becoming obvious once the maximum vertical vorticity in the dipole is roughly half the Coriolis parameter. Possible mechanisms for the wave generation are spontaneous wave emission and the instability of the underlying balanced dipole.
Sling Effect in Collisions of Water Droplets in Turbulent Clouds
Authors: Falkovich Gregory , Pumir Alain
Published: December 2007

The effect of turbulence on the collision rate between droplets in clouds is investigated. Because of their inertia, water droplets can be shot out of curved streamlines of the turbulent airflow. The contribution of such a “sling effect” in the collision rate of the same-size water droplets is described and evaluated. It is shown that already for turbulence with the dissipation rate 103 cm2 s−3, the sling effect gives a contribution to the collision rate of 15-μm droplets comparable to that due to the local velocity gradient. That may explain why the formulas based on the local velocity gradient consistently underestimate the turbulent collision rate, even with the account of preferential concentration.
Temperature Phase Tilt in Unstable Baroclinic Waves
Authors: Sun Che
Published: December 2007

A general property on the phase relation in linear baroclinic instability is proved analytically: in a potential vorticity homogenization regime, the complex geometry of the quasigeostrophic equations determines that the phase lines of temperature and pressure disturbances tilt with height in opposite directions.
A Large Annual Cycle in Ozone above the Tropical Tropopause Linked to the Brewer–Dobson Circulation
Authors: Randel William J. , Park Mijeong , Wu Fei , Livesey Nathaniel
Published: December 2007

Near-equatorial ozone observations from balloon and satellite measurements reveal a large annual cycle in ozone above the tropical tropopause. The relative amplitude of the annual cycle is large in a narrow vertical layer between ∼16 and 19 km, with approximately a factor of 2 change in ozone between the minimum (during NH winter) and maximum (during NH summer). The annual cycle in ozone occurs over the same altitude region, and is approximately in phase with the well-known annual variation in tropical temperature. This study shows that the large annual variation in ozone occurs primarily because of variations in vertical transport associated with mean upwelling in the lower stratosphere (the Brewer–Dobson circulation); the maximum relative amplitude peak in the lower stratosphere is collocated with the strongest background vertical gradients in ozone. A similar large seasonal cycle is observed in carbon monoxide (CO) above the tropical tropopause, which is approximately out of phase with ozone (associated with an oppositely signed vertical gradient). The observed ozone and CO variations can be used to constrain estimates of the seasonal cycle in tropical upwelling.
The Extratropical Tropopause Inversion Layer: Global Observations with GPS Data, and a Radiative Forcing Mechanism
Authors: Randel William J. , Wu Fei , Forster Piers
Published: December 2007

Global characteristics of the extratropical tropopause inversion layer identified in radiosonde observations by Birner are studied using high vertical resolution temperature profiles from GPS radio occultation measurements. The GPS data are organized according to the height of the thermal tropopause in each profile, and a temperature inversion layer above the tropopause (with an average magnitude of 3–5 K) is found to be a ubiquitous, climatological feature. The GPS data show that the inversion layer is present for all seasons in both hemispheres, spanning the subtropics to the pole, and there is not strong longitudinal structure. Dependence of the inversion layer on upper-troposphere vorticity is studied; while anticyclones exhibit a substantially stronger inversion than cyclones (as expected from balanced dynamics), the inversion is evident for all circulation types. Radiative transfer calculations indicate that strong gradients in both ozone and water vapor near the tropopause contribute to the inversion. Significant absorption of both longwave and shortwave radiation by ozone occurs, warming the region above the tropopause. Water vapor near and immediately above the tropopause contributes to cooling, effectively enhancing the inversion.
Analysis of Wave Height Variability Using Altimeter Measurements: Application to the Mediterranean Sea
Authors: Queffeulou Pierre , Bentamy Abderrahim
Published: December 2007

Altimeter significant wave height (SWH) measurement data from six satellite missions covering 14 yr were analyzed over the Mediterranean Sea. First, data correction and screening were performed using the same method for the six altimeters [European Remote Sensing Satellites (ERS-1 and ERS-2), Ocean Topography Experiment (TOPEX), Geosat Follow-On, Jason, and Environmental Satellite (Envisat)]. The data from the TOPEX and Jason missions enabled the construction of seasonal maps of along-track SWH mean values and standard deviations. These reveal the regional short-scale sea state features associated with the specific meteorological patterns of the various geographical basins. Time series of monthly SWH mean values and standard deviations from each satellite and over the whole Mediterranean Sea were calculated and seen to be in good agreement, thus demonstrating interannual variability. The six altimeter missions used together enable the investigation of the monthly annual cycle at the short scales of the various subbasins. Significant differences are observed between the western and eastern parts of the Mediterranean Sea. The annual SWH cycle changes in both shape and amplitude depending on the subbasin. Analysis of the seasonal interannual variability confirms the existence of some degree of independence between the subbasins. Thanks to multisatellite missions and homogeneous corrections of the altimeter data, SWH time and space characteristics were able to be obtained at regional short scales. These results are independent of numerical wind and wave models. This method can be applied to any geographical region.
A Doppler Radar Emulator with an Application to the Detectability of Tornadic Signatures
Authors: May Ryan M. , Biggerstaff Michael I. , Xue Ming
Published: December 2007

A Doppler radar emulator was developed to simulate the expected mean returns from scanning radar, including pulse-to-pulse variability associated with changes in viewing angle and atmospheric structure. Based on the user’s configuration, the emulator samples the numerical simulation output to produce simulated returned power, equivalent radar reflectivity, Doppler velocity, and Doppler spectrum width. The emulator is used to evaluate the impact of azimuthal over- and undersampling, gate spacing, velocity and range aliasing, antenna beamwidth and sidelobes, nonstandard (anomalous) pulse propagation, and wavelength-dependent Rayleigh attenuation on features of interest.

As an example, the emulator is used to evaluate the detection of the circulation associated with a tornado simulated within a supercell thunderstorm by the Advanced Regional Prediction System (ARPS). Several metrics for tornado intensity are examined, including peak Doppler velocity and axisymmetric vorticity, to determine the degradation of the tornadic signature as a function of range and azimuthal sampling intervals. For the case of a 2° half-power beamwidth radar, like those deployed in the first integrated project of the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), the detection of the cyclonic shear associated with this simulated tornado will be difficult beyond the 10-km range, if standard metrics such as azimuthal gate-to-gate shear from a single radar are used for detection.
The USDA Natural Resources Conservation Service Soil Climate Analysis Network (SCAN)
Authors: Schaefer Garry L. , Cosh Michael H. , Jackson Thomas J.
Published: December 2007

Surface soil moisture plays an important role in the dynamics of land–atmosphere interactions and many current and upcoming models and satellite sensors. In situ data will be required to provide calibration and validation datasets. Therefore, there is a need for sensor networks at a variety of scales that provide near-real-time soil moisture and temperature data combined with other climate information for use in natural resource planning, drought assessment, water resource management, and resource inventory. The U.S. Department of Agriculture (USDA)–Natural Resources Conservation Service (NRCS)–National Water and Climate Center has established a continental-scale network to address this need, called the Soil Climate Analysis Network (SCAN). This ever-growing network has more than 116 stations located in 39 states, most of which have been installed since 1999. The stations are remotely located and collect hourly atmospheric, soil moisture, and soil temperature data that are available to the public online in near–real time. New stations are located on benchmark soils when possible. Future plans for the network include increasing the number of stations, improving on user-friendly data summaries, increasing data quality, and scaling the stations to the surrounding region.
Divergence and Vorticity from Aircraft Air Motion Measurements
Authors: Lenschow Donald H. , Savic-Jovcic Verica , Stevens Bjorn
Published: December 2007

This paper considers the accuracy of divergence estimates obtained from aircraft measurements of the horizontal velocity field and points out an error that appears in these estimates that has heretofore not been addressed. A procedure for eliminating this error is presented. The divergence and vorticity are estimated from the coefficients of a least squares fit to a wind field obtained from the Second Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) circular flight legs. These estimates are compared with estimates from numerical models and satellites and with airplane estimates based on tracer budgets and the temporal changes in cloud-top height. The estimates are consistent with expectations and estimates using other methods, albeit somewhat high. Furthermore, significant differences occur among the cases, likely due to the large differences in the techniques. The results indicate that the wind field technique is a viable approach for estimating mesoscale divergence if the wind measurements are accurate. The largest source of wind field systematic error may be the result of flow distortion effects on the air velocity measurement and limitations of in-flight calibrations. Because of flow distortion, the only way the current systems can be calibrated is by flight maneuvers, which assume a steady-state homogeneous nonturbulent atmosphere. Analysis of the errors in this technique suggests that wind field measurements with minimal systematic errors should provide estimates of divergence with much greater accuracy than is now possible with other existing methods.
Stratéole/Vorcore—Long-duration, Superpressure Balloons to Study the Antarctic Lower Stratosphere during the 2005 Winter
Authors: Hertzog Albert , Cocquerez Philippe , Guilbon René , Valdivia Jean-Noël , Venel Stéphanie , Basdevant Claude , Boccara Gillian , Bordereau Jérôme , Brioit Bernard , Vial François , Cardonne Alain , Ravissot Alain , Schmitt Éric
Published: December 2007

In September and October 2005, the Stratéole/Vorcore campaign flew 27 superpressure balloons from McMurdo, Antarctica, into the stratospheric polar vortex. Long-duration flights were successfully achieved, 16 of those flights lasting for more than 2 months. Most flights were terminated because they flew out of the authorized flight domain or because of energy shortage in the gondola. The atmospheric pressure (1-Pa precision) was measured every minute during the flights, whereas air temperature observations (0.25-K accuracy) and balloon positions (absolute GPS observations, 10-m accuracy) were obtained every 15 min. Fifteen-minute-averaged horizontal velocities of the wind were deduced from the successive balloon positions with a corresponding accuracy ≲0.1 m s−1. The collected dataset (more than 150 000 independent observations) provides a thorough high-resolution sampling of the polar lower stratosphere in the Southern Hemisphere from its wintertime state up to the establishment of the summer circulation in December–January. Most of the balloons stayed inside the vortex until its final breakdown, although a few were ejected toward the midlatitudes in November during filamention events associated with an increase in planetary wave activity. The balloons behaved as quasi-Lagrangian tracers during the first part of the campaign (quiescent vortex) and after the vortex breakdown in early December. Large-amplitude mountain gravity waves were detected over the Antarctic Peninsula and caused one flight termination associated with the sudden burst in the balloon superpressure.
Wavelet Filtering to Extract Coherent Vortices from Altimetric Data
Authors: Turiel Antonio , Isern-Fontanet Jordi , García-Ladona Emilio
Published: December 2007

Because of the optimal features of wavelet processing, the use of wavelets for describing and analyzing signals in 2D turbulence has been generalized since a decade ago. In spite of the close analogy between 2D turbulence and geophysical fluid dynamics, few works have tried to generalize the rich framework of wavelet techniques to the study of experimental signals in oceanography. In this paper, the authors extend a prominent wavelet technique designed for the study of direct numerical simulations (DNSs) on 2D turbulence, the coherent vortex simulation, and analyze with it ocean velocity fields obtained from sea surface height maps derived from satellite altimetry. The authors demonstrate the pertinence of this technique to describe altimetry data, resulting in a description of oceanic flows with a reduced number of degrees of freedom. In particular, it is shown that the western Mediterranean circulation is well approximated by a field of extracted coherent vortices when an appropriate wavelet basis is employed as a filter; however, about one-third of the energy is lost in this description, evidencing important differences between results obtained on the frame of 2D turbulence and oceanic data.
Evaluation of a UHF Radar Surface Current Mapping System in an Intertidal Salt Marsh
Authors: Styles Richard , Teague Calvin C.
Published: December 2007

A UHF RiverSonde radar system was deployed in an intertidal salt marsh during November and December 2005 near Georgetown, South Carolina. The purpose of this experiment was to evaluate radar performance in a coastal plain salt marsh, where the channels are highly sinuous and the flow is dominated by tides. To help evaluate radar performance, an acoustic current profiler was placed in a large subtidal channel located in the field of view of the radar. Comparisons indicated that the radar accurately reproduced both the magnitude and phasing of the surface current. Spatial coverage was generally good in the channels but much more sporadic over the marsh platform. Temporal coverage in the channel was also good and correlated with wind speed. Reliable measurements were obtained under wind speeds as low as 2–3 m s−1, which are common at this site. In addition, some unexpected signals were seen at near zero Doppler shift, which were attributed to the saltwater vegetation Spartina alterniflora, which acted as effective radar targets. However, these signals were uncorrelated and likely can be filtered.