bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tropical‐wide teleconnection and oscillation. II: The enso‐monsoon system
Authors: Miykoda K. , Navarra A , Ward M. N. 
Published: July 2010

AbstractTwo teleconnection indices, discussed in Part I, i.e. the Tropical‐wide Oscillation Index (TOI) and the Walker circulation Index (WAI), are applied to the analysis of the ENSO‐monsoon (El Niño Southern Oscillation‐Asian monsoons) system. the first hypothesis presented in Part I was that the TOI for July‐August‐September (JAS) is closely related to the Indian summer monsoon index as well as the Southern Oscillation Index. As a result, the TOI represents the lead‐lag characteristics of the tropical circulation variability over the eastern hemisphere (45°E‐170°E) and simultaneously its interaction with the ENSO over the equatorial Pacific. the second hypothesis was that there are two types of connection between the ENSO and Asian monsoons: type I with distinct connection in space and time, and type II without connection. the WAI provides a measure for this connection. This idea is supported by comparisons of observed and model teleconnection structures in Part I.Part II investigates these relations further. Time‐lag correlations are calculated between the key indices and atmospheric variables over the equatorial Indo‐Pacific Oceans. If type II years, derived by the WAI, are removed from the 34‐year time series, correlations between the TOI and these variables increase appreciably, now showing clearly the biennial character. the analysis identifies a sequence of events involving biennial oscillation of the ENSO‐monsoon system from approximately JAS(‐1) to JAS(O), followed by intensification of the ENSO from JAS(O) to November‐December‐January(+1). the ENSO‐monsoon oscillation system is not sinusoidal but skewed.To show the geographical patterns associated with the above sequence of events, planar maps are presented of the lag correlation between the observed TOI(JAS) and (i) vertical velocity at the 500hPa level, (ii) precipitation, (iii) sea surface temperature (SST), and (iv) atmospheric sea level pressure. Distinct geographical distributions of the ENSO‐monsoon oscillation emerge in both the observations and model data. One pattern is characterized by a horseshoe shape over the Pacific, which is generally symmetric around the equator, but with geographical differences depending on location in the lag sequence. the other pattern is a see‐saw shape, primarily a standing oscillation located in the eastern South Pacific and the Indian Oceans, resembling the sea‐level‐pressure pattern found by Trenberth and Shea. Applying the lead‐lag relationship, it is demonstrated that the SST over the central Pacific four months ahead can be projected, based on the TOI(JAS). Conversely, the intensity of the Indian monsoon rainfall for non‐type II years can be projected 15 months ahead by the SST over the eastern Pacific Ocean. This indicates that the ENSO‐monsoon oscillation system is quasi‐periodic, as opposed to irregular, with a two‐year cycle; this is clearly revealed with the removal of type II years.
Radiative forcing and climate sensitivity: The ozone experience
Authors: Christiansen Bo 
Published: July 2010

AbstractThe climatic impact of ozone perturbations is studied with a general‐circulation model by considering both the radiative forcing at the tropopause and the change in the near‐surface temperature. In particular, we focus on the vertical sensitivity by imposing the perturbations in different vertical layers. the simulations are done in perpetual‐January mode and with climatological sea ice. the main part of the analysis is focused on global‐mean values and in particular on the surface energy budget. Moderate sensitivities related to weak positive feedbacks are found when the perturbation is applied to the troposphere or the lower stratosphere, while larger sensitivities are found for perturbations in the higher stratosphere. This difference in the feedbacks is argued to be related to the vertical partitioning of the radiative forcing determined by the relative strengths of the long‐wave and short‐wave forcings. While the larger part of the short‐wave forcing, which dominates for ozone perturbations in the higher stratosphere, penetrates to the surface, the long‐wave forcing is predominantly deposited in the free troposphere. When the model is forced at the surface, latent‐heat flux effectively transports energy to the free troposphere restoring the lapse rate to its unperturbed value. Conversely, when the forcing is located in the free troposphere transport to the surface is limited. For the experiments under consideration the radiative forcing and the climate sensitivity are found to be robust and only slightly sensitive to the definition of the tropopause. As a measure of climate change the forcing adjusted for thermal changes in the stratosphere is superior to both the instantaneous forcing and to the forcing obtained after dynamical changes in the stratosphere.
Four‐dimensional variational assimilation of special sensor microwave/imager total column water vapour in the ECMWF model
Authors: Gérard É. , Saunders R. W. 
Published: July 2010

AbstractSpecial Sensor Microwave/Imager (SSM/I) radiances have been used to infer a total column water‐vapour amount using a one‐dimensional variational retrieval in the European Centre for Medium‐Range Weather Forecasts (ECMWF) forecast model. These retrievals are then assimilated using the operational, four‐dimensional variational (4DVar) analysis at ECMWF. the impact of assimilating the total column water vapour on the ECMWF analyses and forecasts is assessed. the primary impact is on the model analysed humidity fields in the tropics and southern hemisphere where 2 to 4% more water vapour is included in the lower troposphere. the addition of moisture in the model also has an impact on the meridional circulation. No impact is seen in the mean extratropical forecast performance but a case study is presented of the improved forecast of low‐pressure systems in the Southern Ocean, when SSM/I data are used in 4DVar.
North atlantic oscillatiodannular mode: Two paradigms—one phenomenon
Authors: Wallace John M. 
Published: July 2010

AbstractThe North Atlantic Oscillation (NAO), as defined in the studies of Sir Gilbert Walker ca. 1930, and the zonal‐index cycle, as elaborated by investigators at the Massachusetts Institute of Technology some twenty years later, are different interpretations of the same entity, whose time variations are well represented by the leading principal component of the northern hemisphere sea‐level pressure field. The NAO paradigm envisions this phenomenon as involving a unique teleconnection pattern in the Atlantic sector that varies on interannual and longer time‐scales in association with large‐scale atmosphere‐ocean interaction. In contrast, the zonal‐index‐cycle paradigm posits the existence of independent, fundamentally zonally symmetric (or ‘annular’) modes of variability in the northern and southern hemispheres, both of which fluctuate on intraseasonal as well as interannual time‐scales. Spontaneous interactions between the zonally symmetric flow and the eddies are viewed as being largely responsible for the variability of the annular modes at the higher frequencies, and a variety of different mechanisms including, but by no means limited to, atmosphere‐ocean interaction are viewed as potentially capable of forcing them at the lower frequencies. The NAO and ‘annular mode’ paradigms offer contradictory interpretations of the causal linkages that are responsible for the observed correlations between North Atlantic climate variability and variations in a diverse array of zonally averaged quantities. They suggest different research agendas and they evoke quite different images in the popular press. It is argued that the two paradigms cannot be equally valid and that it is in the interests of the community to come to a consensus as to which of them is more appropriate. Rules of evidence are proposed as a basis for making that decision.
A gcss model intercomparison for a tropical squall line observed during toga‐coare. I: Cloud‐resolving models
Authors: Redelsperger J.‐L. , Brown P. R. A. , Guichard F. , How C. , Kawasima M. , Lang S. , Montmerle T. , Nakamura K. , Saito K. , Seman C. , Tao W. K. , Donner L. J. 
Published: July 2010

AbstractResults from eight cloud‐resolving models are compared for the first time for the case of an oceanic tropical squall line observed during the Tropical Ocean/Global Atmosphere Coupled Ocean‐Atmosphere Response Experiment. There is broad agreement between all the models in describing the overall structure and propagation of the squall line and some quantitative agreement in the evolution of rainfall. There is also a more qualitative agreement between the models in describing the vertical structure of the apparent heat and moisture sources.The three‐dimensional (3D) experiments with an active ice phase and open lateral boundary conditions along the direction of the system propagation show good agreement for all parameters. The comparison of 3D simulated fields with those obtained from two different analyses of airborne Doppler radar data indicates that the 3D models are able to simulate the dynamical structure of the squall line, including the observed double‐peaked updraughts. However, the second updraught peak at around 10 km in height is obtained only when the ice phase is represented. The 2D simulations with an ice‐phase parametrization also exhibit this structure, although with a larger temporal variability.In the 3D simulations, the evolution of the mean wind profile is in the sense of decreasing the shear, but the 2D simulations are unable to reproduce this behaviour.
A GCSS model intercomparison for a tropical squall line observed during toga‐coare. II: Intercomparison of single‐column models and a cloud‐resolving model
Authors: Bechtold P. , Redelsperger J.‐L. , Beau I. , Blackburn M. , Brinkop S. , Grandper J.‐Y. , Grant A. , Gregory D. , Guichard F. , How C. , Ioannidou E. 
Published: July 2010

AbstractThis paper presents single‐column model (SCM) simulations of a tropical squall‐line case observed during the Coupled Ocean‐Atmosphere Response Experiment of the Tropical Ocean/Global Atmosphere Programme. This case‐study was part of an international model intercomparison project organized by Working Group 4 ‘Precipitating Convective Cloud Systems’ of the GEWEX (Global Energy and Water‐cycle Experiment) Cloud System Study.Eight SCM groups using different deep‐convection parametrizations participated in this project. The SCMs were forced by temperature and moisture tendencies that had been computed from a reference cloud‐resolving model (CRM) simulation using open boundary conditions. The comparison of the SCM results with the reference CRM simulation provided insight into the ability of current convection and cloud schemes to represent organized convection. The CRM results enabled a detailed evaluation of the SCMs in terms of the thermodynamic structure and the convective mass flux of the system, the latter being closely related to the surface convective precipitation. It is shown that the SCMs could reproduce reasonably well the time evolution of the surface convective and stratiform precipitation, the convective mass flux, and the thermodynamic structure of the squall‐line system. The thermodynamic structure simulated by the SCMs depended on how the models partitioned the precipitation between convective and stratiform. However, structural differences persisted in the thermodynamic profiles simulated by the SCMs and the CRM. These differences could be attributed to the fact that the total mass flux used to compute the SCM forcing differed from the convective mass flux. The SCMs could not adequately represent these organized mesoscale circulations and the microphysicallradiative forcing associated with the stratiform region. This issue is generally known as the ‘scale‐interaction’ problem that can only be properly addressed in fully three‐dimensional simulations.Sensitivity simulations run by several groups showed that the time evolution of the surface convective precipitation was considerably smoothed when the convective closure was based on convective available potential energy instead of moisture convergence. Finally, additional SCM simulations without using a convection parametrization indicated that the impact of a convection parametrization in forced SCM runs was more visible in the moisture profiles than in the temperature profiles because convective transport was particularly important in the moisture budget.
The second compare exercise: A model intercomparison using a case of a typical mesoscale orographic flow, the pyrex iop3
Authors: Georgelin Marc , Bougeault Philippe , Black Thomas , Brzovic Nedjlejka , Buzzi Andrea , Calvo Javier , Cassé Vincent , Desgagné Michel , El‐Khatib Ryad , Geleyn Jean‐Francois , Holt Teddy , Hong Song‐You , Kato Teruyuki , Katzfey Jack , Kurihara Kazuo , Lacroix Bruno , Lalaurette Francois , Lemaitre Yvon , Mailhot Jocelyn , Majewski Detlev , Malguzzi Pietro , Masson Valery , McGregor John , Minguzzi Enrico , Paccagnella Tiziana , Wilson Clne 
Published: July 2010

AbstractFifteen models have been evaluated for their ability to simulate the various phenomena of a mesoscale orographic flow sampled during the Pyrénées experiment (PYREX). A pure forecast exercise has been conducted and model performances were assessed using numerous observations. for additional experiments were also performed in order to discriminate between small‐scale errors and large‐scale induced errors, and to discuss an optimal specification of model terrain height and roughness for use with envelope orography and effective roughness length parametrizations.The comparison results reveal systematic errors for all the models: the local winds are too weak, the mountain‐wave amplitude is too large and the lee vortices are poorly represented. Since forcing by analyses did not correct the errors, they can be therefore mainly attributed to the model representation of orography. The blocking created by the model topography at low level is under‐represented and the model topography does not sufficiently slow the flow.A positive consequence of the effective roughness length parametrization is to reduce the mountain‐wave amplitude. Negligible benefit occurs from the use of an envelope orography parametrization. Although it favours the appearance of the lee vortices, the latter appear too early, the local winds remain too weak, and the mountain‐wave amplitude is enhanced. The comparison of the computed pressure drag with the observed one is reasonably good for most of the models but the pressure drag is found to be more correlated to the lee vorticity than to the mountain wave.
The impact of a physically based microphysical scheme on the climate simulation of the meteorological office unified model
Authors: Wilson Damian 
Published: July 2010

AbstractThe predictions of two, large‐scale precipitation schemes for a general‐circulation model are compared within a development version of the Meteorological Office's climate model. One scheme contains a prognostic ice content and a representation of mixed‐phase microphysical processes, whereas the second scheme is a diagnostic scheme where condensate is partitioned into liquid and ice as a function of temperature. Results show that, although the overall near‐surface conditions are similar, significant differences occur in the structure of clouds predicted by the two schemes. The total precipitation rate is similar, but the microphysical scheme has less convective activity than the temperature‐partition scheme, because of the different subgrid nature of the schemes. Layer‐cloud amounts are changed due to both changes in condensate and changes in its diagnosis. More ice is predicted by the microphysical scheme, mainly as a result of reduced fall speeds of ice particles. This shows the need for global measurement methods of ice‐water content to be developed.
Density currents in two‐layer shear flows
Authors: Xue Ming 
Published: July 2010

AbstractAn earlier two‐fluid model of an idealized densitycurrent in low‐level shear is extended to include variable upper‐level shear. Far‐field solutions are determined, based on the conservation of mass, momentum and vorticity, and the conservation of Bernoulli function (energy) along streamlines for inviscid flows. It is found that the upper‐level and low‐level shears play similar roles in controlling the depth of steady‐state density‐currents. In most cases, large positive upper‐level shear supports a deeper density‐current and steeper front, and therefore a stronger updraught. It is also found that when the low‐level shear is weak and upper‐level shear occupies about half the domain depth, larger positive shear can result in a shallower rather than a deeper density‐current. This behaviour was not found for either constant shear flow or flows with only low‐level shear. The behaviour is understood by examining the flow structure and flow‐force components as a function of the upper‐level shear, Furthermore, by allowing the upper‐level shear to vary, an overturning flow is permitted ahead of the density current. This was not possible in the earlier model in which the upper‐level flow was assumed to be constant. The present extension allows us to draw closer analogues between the model solutions and the circulation patterns found in typical squalllines in sheared environments.Time‐dependent numerical experiments are conducted for a range of upper‐ and low‐level shears. The depth and the propagation speed of simulated density‐currents are found to agree very well with predictions by the idealized theoretical model. This verifies the validity of the theoretical model. In addition, numerical experiments with identically zero low‐level shear but differing upper‐level shears suggest that the deeper shear is as important as the low‐level shear in determining the uprightness of the upward branch of inflow. In fact, the presence of positive low‐level inflow shear may not be essential. Such results are also supported by the theoretical model, and may have important implications for our understanding of squall‐line dynamics.
Total‐ozone imaging over north america with GOES‐8 infrared measurements
Authors: Orsolini Y. J. , Karcher F. 
Published: July 2010

AbstractInfrared observations from the Geostationary Operational Environmental Satellite (GOES‐8) are used to provide high‐resolution synoptic maps of total ozone over North America for 23/24 February 1996. The infrared retrievals are validated with total ozone measured by the Global Ozone Monitoring Experiment instrument. In the GOES‐derived total‐ozone maps, one can identify fine‐scale structures. A prominent one is a slow‐moving, slender filament with a typical contrast of 30 Dobson units, stretching across North America along the 40°N latitude circle. A high‐resolution ozone simulation using European Centre for Medium‐range Weather Forecasts winds for this period also displays total‐ozone filaments characterized by high contrasts. There are more filamentary structures in the model.
Temperature changes over short distances as shown by records in the Edinburgh district
Authors: Spence M. T. 
Published: July 2010

AbstractTemperature records for six meteorological stations in and around Edinburgh are examined and some of the differences in the records are discussed in relation to topographical and other features of the locality. It is found that, in summer, a t the time of maximum temperature, the vertical gradient of temperature in a valley might average some four times the dry adiabatic “lapse‐rate.” Rather big temperature differences are also found between the coast and a valley some four miles inland. The bearing of trees and hedges on the results is considered.
Some characteristics of the mean annual circulation over the British Isles
Authors: Goldie A. H. R. 
Published: July 2010

AbstractThe westerly component of the mean annual drift of air over the northern part of the British Isles has, during the last 30 years, attained maxima at intervals mostly of four years. Using this element as an index for classifying the years, the writer sets out the special features which in 1,arious corresponding years have affected weather, temperature, rainfall, sunshine and gales in the British Isles.It is shown that years in which the westerly component of air drift reached a maximum have been characterised on the average by warmer and drier conditions and their summers individually by sunnier conditions than other years of the series; years preceding a maximum (so far as the available statistics enable the point to be explored) appear mostly to have been characterised by a high duration of winds of gale force and by a maximum “latitude‐exchange” of air.Attention is called to the fact that Lockyer, over 30 years ago. noted the existence of a 3–8 year period in atmosphere pressure in India, Australasia and South America, and that more recently Elton, from biological researches and Kershaw from consideration of sunshine data, have remarked on the probability of a climatic factor with a period of about four years.
Effect of CH···O hydrogen bond length on the geometric and spectroscopic features of the peptide unit of proteins
Authors: Scheiner Steve 
Published: July 2010

AbstractA formamide molecule is allowed to form a CH···O H‐bond with a glycine dipeptide in both its C5 and C7 internal conformations. As this intermolecular H‐bond is elongated, the contraction of the CH covalent bond is monitored, as is its vibrational stretching frequency and intensity, along with NMR chemical shifts of the atoms involved in the H‐bond. The degree of shortening of the CH bond becomes progressively smaller as the proton acceptor is moved further away, as does the blue shift of the CH stretching frequency, and the chemical shift of the bridging proton. These changes are monotonic and regular enough that experimental evaluation of CH bond length or blue shift or proton NMR chemical shift may be used to accurately predict the energetics of the H‐bond for any particular geometry. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010