bluuebunny/crossref_metadata_2025_split huggingface dataset:
The deep‐atmosphere Euler equations with a mass‐based vertical coordinate
Authors: Wood Nigel , Staniforth Andrew 
Published: July 2003

AbstractThe terrain‐following hydrostatic pressure‐coordinate system for the shallow‐atmosphere Euler equations is generalized for deep atmospheres using a mass‐based vertical coordinate. A consequent benefit is that an existing (shallow atmosphere) hydrostatic primitive‐equations model, which uses a pressure‐based terrain‐following vertical coordinate, could be modified for non‐hydrostatic deep‐atmosphere applications, without the need to change the scientific and computing infrastructure substantially in which it is embedded. © Crown copyright, 2003. Royal Meteorological Society
Stratospheric temperatures in Antarctic winter: does the 40‐year record confirm midlatitude trends in stratospheric water vapour?
Authors: Roscoe H. K. , Colwell S. R. , Shanklin J. D. 
Published: June 2003

AbstractWater vapour is a potent greenhouse gas, and the observed increases in water vapour in the stratosphere act to cool it. Possible changes in stratospheric temperatures are important for future ozone loss because colder temperatures in the edge region of the Antarctic ozone hole act to increase polar stratospheric clouds there, and so delay recovery of the ozone hole. Trends in lower‐stratospheric temperature within the core of the Antarctic vortex in winter should be a unique indicator of trends in stratospheric water vapour, because neither changes in CO2 nor in ozone have a large effect on temperature in the lower stratosphere in the dark. Here, measured stratospheric temperatures southward of 70°S in winter are presented and their quality and corrections discussed. The character and magnitude of the long‐term changes at Halley (76°S) are similar from 100 to 70 hPa and at 50 hPa, whether corrected for sonde changes or not, and are also similar to those at other Antarctic sites. We found no significant trend in temperatures at Halley between 1960 and 2000, which is inconsistent with the change calculated from the trend in lower‐stratospheric water vapour in northern hemisphere midlatitudes between 1960 and 2000. Over the shorter interval between 1980 and 2000 at Halley, the change in temperature was −1.8±0.6 K, in agreement with the change calculated from the trend in stratospheric water vapour in northern hemisphere midlatitudes between 1980 and 2000. The differences between these periods are discussed in terms of: possible fortuitous agreement between 1980 and 2000; the poorer representation and quality of the measurements of stratospheric water vapour between 1960 and 1980; and a possible large variation in the rate of oxidation of CH4 to H2O in the upper stratosphere between 1960 and 1980. Such a variation in oxidation rate was observed by satellite between 1992 and 1999. Copyright © 2003 Royal Meteorological Society
Simulation of satellite channel radiances in the Met Office Unified Model
Authors: Ringer M. A. , Edwards J. M. , Slingo A. 
Published: July 2003

AbstractA system is described which allows satellite channel radiances to be simulated within both the numerical weather prediction and climate versions of the Met Office Unified Model. It is based on a spherical harmonics version of the radiation code that calculates radiative fluxes and heating rates in the climate model and it uses the same pre‐processing software and molecular absorption database. In the results shown here, fractional cloud cover is represented by decomposition into separate columns. The methodology is described and results of off‐line tests of the code against high spectral resolution calculations are presented. Examples of infrared window and water vapour channel brightness temperatures simulated using the global forecast model are then compared with Meteosat 7 imagery. The utility of radiance simulations for model validation studies is illustrated by these comparisons, and other applications are also discussed. © Crown copyright, 2003. Royal Meteorological Society
Dependence of aqua‐planet simulations on time step
Authors: Williamson David L. , Olson Jerry G. 
Published: June 2003

AbstractAqua‐planet simulations with Eulerian and semi‐Lagrangian dynamical cores coupled to the NCAR CCM3 parametrization suite produce very different zonal average precipitation patterns. The model with the Eulerian core forms a narrow single precipitation peak centred on the sea surface temperature (SST) maximum. The one with the semi‐Lagrangian core forms a broad structure often with a double peak straddling the SST maximum with a precipitation minimum centred on the SST maximum. The different structure is shown to be caused primarily by the different time step adopted by each core and its effect on the parametrizations rather than by different truncation errors introduced by the dynamical cores themselves. With a longer discrete time step, the surface exchange parametrization deposits more moisture in the atmosphere in a single time step, resulting in convection being initiated farther from the equator, closer to the maximum source. Different diffusive smoothing associated with different spectral resolutions is a secondary effect influencing the strength of the double structure. When the semi‐Lagrangian core is configured to match the Eulerian with the same time step, a three‐time‐level formulation and same spectral truncation it produces precipitation fields similar to those from the Eulerian.It is argued that the broad and double structure forms in this model with the longer time step because more water is put into the atmosphere over a longer discrete time step, the evaporation rate being the same. The additional water vapour in the region of equatorial moisture convergence results in more convective available potential energy farther from the equator which allows convection to initiate farther from the equator. The resulting heating drives upward vertical motion and low‐level convergence away from the equator, resulting in much weaker upward motion at the equator. The feedback between the convective heating and dynamics reduces the instability at the equator and decreases the convection there. The behaviour of the parametrizations depends on the amount of water inserted into the troposphere during a discrete time step. This is as important as the rate of insertion. Experiments are described that support this explanation. Copyright © 2003 Royal Meteorological Society
The behaviour of large‐scale model cloud schemes under idealized forcing scenarios
Authors: Wilson Damian , Gregory David 
Published: July 2003

AbstractThe behaviour of widely used large‐scale cloud schemes is assessed in the idealized framework of a single grid box forced by uniform warming or cooling. The general advantages and disadvantages of using diagnostic and prognostic schemes are compared, as are characteristics of observational relationships and specific parametrization schemes used in general‐circulation models. It is noted that all parametrization schemes fail to produce, in some way, the correct behaviour when the grid box is forced and initial conditions altered. The reasons for this fundamental result are discussed. Closures for prognostic cloud schemes under uniform forcing are investigated, and a closure developed which closely meets the theoretically ideal behaviour. © Crown copyright, 2003. Royal Meteorological Society
A comparison of two methods for developing the linearization of a shallow‐water model
Authors: Lawless A. S. , Nichols N. K. , Ballard S. P. 
Published: July 2003

AbstractWe develop the linearization of a semi‐implicit semi‐Lagrangian model of the one‐dimensional shallow‐water equations using two different methods. The usual tangent linear model, formed by linearizing the discrete nonlinear model, is compared with a model formed by first linearizing the continuous nonlinear equations and then discretizing. Both models are shown to perform equally well for finite perturbations. However, the asymptotic behaviour of the two models differs as the perturbation size is reduced. This leads to difficulties in showing that the models are correctly coded using the standard tests. To overcome this difficulty we propose a new method for testing linear models, which we demonstrate both theoretically and numerically. © Crown copyright, 2003. Royal Meteorological Society
The dynamics of NAO teleconnection pattern growth and decay
Authors: Feldstein Steven B. 
Published: July 2003

AbstractThis investigation performs both diagnostic analyses with NCEP/NCAR re‐analysis data and forced, barotropic model calculations to examine the dynamical mechanisms associated with the growth and decay of the North Atlantic Oscillation (NAO) teleconnection pattern. The diagnostic calculations include projection and composite analyses of each term in the stream‐function‐tendency equation.The results of the analyses reveal a complete life cycle of growth and decay within approximately two weeks. The positive NAO phase is found to develop after anomalous wavetrain propagation across the North Pacific to the east coast of North America. This contrasts with the negative NAO phase which appeared to develop in situ.Both high‐frequency (period <10 days) and low‐frequency (period >10 days) transient eddy fluxes drive the NAO growth. After the NAO anomaly attains its maximum amplitude, the high‐frequency transient eddy fluxes continue to drive the NAO anomaly in a manner that is consistent with a positive feedback process. The decay of the NAO occurs through both the divergence term and the low‐frequency transient eddy fluxes. The temporal and spatial properties of the divergence term are found to be consistent with Ekman pumping. These results illustrate many important differences between the NAO and Pacific/North American (PNA) teleconnection patterns, perhaps most striking being that the NAO life cycle is dominated by nonlinear processes, whereas the PNA evolution is primarily linear, In addition, the relation between the NAO and the zonal index is discussed. Copyright © 2003 Royal Meteorological Society
Effects of vertical differencing in a minimal hurricane model
Authors: Zhu Hongyan , Smith Roger K. 
Published: July 2003

AbstractThe minimal three‐layer hurricane model developed by the authors is reformulated with a Charney–Phillips grid (CP‐grid) in the vertical instead of the Lorenz grid (L‐grid) that was used in the original model. It has been shown by others that the popular L‐grid supports a computational mode in the temperature field that can lead to inaccuracies, especially when moist processes are involved. Here we compare calculations of the hurricane model using the L‐grid and CP‐grid. We present evidence that the computational mode is excited in the L‐grid model during the period of rapid vortex intensification, which begins when grid‐scale latent‐heat release occurs in the core region. Thus it would appear that the solution in the mature stage of evolution is contaminated by this mode. We show also that the vortex asymmetries that develop during the mature stage are sensitive to the choice of vertical grid and argue that those that occur in the CP‐grid formulation are more realistic. It is possible that the computational mode is a spurious feature of many earlier studies of asymmetries in hurricane models in which moist processes are represented. Copyright © 2003 Royal Meteorological Society
Flow regimes in the winter stratosphere of the northern hemisphere
Authors: Gray L. J. , Sparrow S. , Juckes M. , O'neill A. , Andrews D. G. 
Published: July 2003

AbstractA stratosphere–mesosphere model is used to investigate the response of the northern‐hemisphere stratospheric flow regime to changes in tropospheric wave forcing and equatorial wind direction. An ensemble approach is employed to assess changes in variability. The flow regime of the modelled atmosphere is broadly determined by the strength of the imposed tropospheric forcing. However, there exists a region of parameter space, where the tropospheric forcing is intermediate, in which the tropospheric control of the stratospheric response is substantially weakened. Under these circumstances the ambient background flow of the stratosphere into which the tropospheric planetary waves propagate is important. We define three flow regimes based upon the likelihood of stratospheric warming events, which may have a correspondence in the real atmosphere. With low tropospheric forcing major warming events never occur. With strong tropospheric forcing major warmings always occur. With intermediate forcing, which we suggest may be the case for most of the time in the northern hemisphere, there is reduced tropospheric control, greater uncertainty in the stratospheric response and an increased window of opportunity for influence from other factors such as early‐winter initial conditions, the Quasi‐Biennial Oscillation (QBO) and possibly the solar cycle. We emphasize the importance of using Eliassen–Palm (EP) flux diagnostics not only to examine the extent of ‘wave activity’ but also to examine where the interaction of the waves with the mean flow is strongest. The latter suggests that flow modification in the upper stratosphere as the Aleutian high is developing is a key aspect of the early stages of the stratospheric warming. The model shows strong evidence that the flow in the mid and upper stratosphere modifies the EP fluxes at the lower boundary and that the wave fluxes through the lower boundary should be considered as part of the response to forcing rather than as the forcing per se. We also highlight the role of travelling anticyclones in the build up of the Aleutian high, the subsequent sudden stratospheric warming and, hence, the modelled variability. These anticyclones are features of the subtropical upper stratosphere with maximum amplitude at the stratopause. Warm disturbed winters are associated with travelling anticyclones that have larger amplitude than average and are more effective in penetrating polewards. Copyright © 2003 Royal Meteorological Society
Layer‐wise attribution of vertical motion and the influence of potential‐vorticity anomalies on synoptic development
Authors: Dixon M. A. G. , Thorpe A. J. , Browning K. A. 
Published: June 2003

AbstractA methodology is presented for attributing vertical motion to potential vorticity (PV) in a explicit manner using the quasi‐geostrophic omega equation. The methodology is then used to determine the contribution individual PV anomalies make to the synoptic development. It is shown how the total vertical motion may be decomposed into self‐generating and interaction terms. The former correspond to vertical motion that arises from one PV region alone, whilst each of the interaction terms represent vertical motion due to the interaction of two different regions of PV. The method is applied to a number of cyclones studied in the Fronts and Atlantic Storm‐Tracks Experiment in order to determine the dynamical role of individual PV regions in cyclogenesis. For purposes of comparison, cyclones were chosen to be representative of the types (A, B and C) of an extended Petterssen–Smebye scheme devised by Deveson, Browning and Hewson. In terms of our new PV method, the Type A and B cyclones exhibit only subtle differences, with the upper‐level layer of PV playing a larger role in the case of the Type B cyclone. A much larger difference is apparent between the Type A and B cyclones on the one hand, and the Type C cyclone on the other: in the Type C cyclone, the upper‐level PV self‐generating term plays an important role, whereas in the Type A and B cases the influence of the upper‐level PV is largely restricted to the interaction terms. In all of the cases, the vertical motion attributable to the interaction between the low‐level PV and boundary thermal gradient was found to be large. Hence, from the viewpoint of instantaneous attribution, we conclude that the low‐level PV is always important. Copyright © 2003 Royal Meteorological Society
Small‐scale rainfall mechanisms for an idealized convective southerly flow over the Alps
Authors: Gheusi François , Stein Joel 
Published: June 2003

AbstractRain‐producing flows over the south side of the Alps are investigated with an idealized high‐resolution (2.5 km) numerical configuration where only three basic ingredients of typical heavy‐precipitation situations have been retained: (1) a uniform and stationary southerly flow far upstream from the Alps, which drives (2) a conditionally unstable atmosphere towards (3) the real topography of the Alps and the surrounding secondary mountains. Attention is given to small‐scale mechanisms of rainfall over the Po Plain and the Alpine slopes. These are linked with two orographically induced low‐level wind jets: the easterly barrier‐wind jet along the southern flank of the Alps and a south‐easterly jet formed over the sea along the south‐western flank of the Apennines and continuing over land up to the Alps. The specific role of the secondary relief upstream from the Alps in inducing or influencing these low‐level flow features, and also in triggering organized convection, is studied by means of experiments on the sensitivity to topography. The idealized configuration also allows the advantages of a convection‐resolving model for modelling precipitation distributions at the Alpine valley scale to be considered. Copyright © 2007 Royal Meteorological Society
Dynamical equivalence and the departure‐point equation in semi‐Lagrangian numerical models
Authors: White A. A. 
Published: July 2003

AbstractThe kinematics and Newtonian dynamics of a continuous fluid may be presented in a number of ways. Given the kinematic relation between velocity and position, the dynamics may be formulated in terms of momentum or in terms of angular momentum and the scalar product of velocity and position. It is also possible to carry out the formulation in terms of momentum, angular momentum and the scalar product of velocity and position, in which case the kinematic relation becomes a deducible property. The three formulations are dynamically equivalent in the sense that the flow evolution is demonstrably the same in each. It seems desirable to build this elementary symmetry into discrete models. Two‐time‐level, semi‐Lagrangian models are considered here, with emphasis on the departure‐point equation (from which trajectory origins at the earlier time‐level are determined). Once a rule has been chosen for the approximation of trajectory time‐averages of vector and scalar products, dynamical equivalence implies a particular form of the departure‐point equation. One such rule delivers a doubly‐implicit equation that is a simple time‐centred discretization of the kinematic relation. A second rule leads to a form that differs only slightly from the singly‐implicit equation of Gospodinov and co‐workers. It is noted that dynamical equivalence relates to the consistency and non‐ambiguity of results rather than to their accuracy. © Crown copyright, 2003. Royal Meteorological Society
Benefits of increased resolution in the ECMWF ensemble system and comparison with poor‐man's ensembles
Authors: Buizza R. , Richardson D. S. , Palmer T. N. 
Published: July 2003

AbstractIn November 2000 the resolution of the forecast model in the operational European Centre for Medium‐Range Weather Forecasts Ensemble Prediction System was increased from a 120 km truncation scale (EPS) to an 80 km truncation scale (High‐resolution EPS or HEPS). The HEPS performance is compared with that of EPS and with different flavours of poor‐man's ensembles. Average results based on Brier skill scores and the potential economic value of probabilistic predictions for 57 winter and 30 summer cases indicate that the new HEPS system is about 12 hours more skilful than the old EPS. Averages over 39 winter cases indicate that HEPS forecasts perform better than five‐centre ensemble forecasts. Results also show that if forecasts are transformed into parametrized Gaussian distribution functions centred on the bias‐corrected ensemble mean and with re‐scaled standard deviation, HEPS‐based parametrized forecasts outperform all other configurations. Diagnostics based on parametrized forecast probabilities indicate that the different impact on the probabilistic or deterministic forecast skill is related to the fact that HEPS better represents the daily variation in the uncertainty of the atmosphere, and is not simply a reflection of improved mean bias or of a better level of spread. Copyright © 2003 Royal Meteorological Society
The evolution of subgrid‐scale humidity fluctuations in the presence of homogeneous cooling
Authors: Stiller Olaf , Gregory David 
Published: July 2003

AbstractThe evolution of the moisture field is studied for the situation where clouds are formed through homogeneous cooling. Large‐eddy simulations (LES) which include only the most intrinsic physical mechanisms show that the moisture distribution may change considerably even for this idealized case. The reason is a circulation driven by the latent heat which is released inhomogeneously due to the inhomogeneity (fluctuations) of the moisture field. This circulation in turn affects the moisture field through two mechanisms: (i) turbulent mixing and (ii) vertical advection. The parameters which govern the relative strengths of these mechanisms are expressed as characteristic length‐scales related to the humidity and moist‐static‐energy field. The LES results demonstrate the usefulness of this framework. They also exhibit an interesting (square root) relationship between the height of vertical displacements and the corresponding length‐scale obtained from adiabatic theory (i.e. neglecting mixing processes). A simplified mathematical model for the mixing is presented which links this behaviour to a possible self similarity of the mixing efficiency of moist static energy. Some implications for cloud parametrizations are discussed. © Crown copyright, 2003. Royal Meteorological Society
Fetus‐in‐fetu form of monozygotic twinning with retroperitoneal teratoma
Authors: Gilbert‐Barness Enid , Opitz John M. , Debich‐Spicer Diane , Mueller Thomas , Arnold Sonya R. , Quintero Reuben 
Published: June 2003

AbstractOne of the commonest defects of blastogenesis is monozygotic twinning resulting in separate or conjoint twins, the latter including a category of internal, “endoparasitic,” or fetus‐in‐fetu twins. We report the third known instance of endoparasitic twinning associated with a benign teratoma at age 1. The host, twin, and teratoma were monozygotic by DNA analysis. © 2003 Wiley‐Liss, Inc.
Leonardi R, Caltabiano M, Lo Muzio L, Gorlin RJ, Bucci P, Pannone G, Canfora M, Sorge G. 2002. Bilateral hyperplasia of the mandibular coronoid processes in patients with nevoid basal cell carcinoma syndrome: an undescribed sign. Am J Med Genet 110:400–403
Authors: Leonardi Rosalia , Caltabiano Mario , Lo Muzio Lorenzo , Gorlin Robert J. , Bucci Paolo , Pannone Giuseppe , Canfora Massimo , Sorge Giuseppe 
Published: June 2003

AbstractThe original article to which this Erratum refers was published in Am J Med Genet 110:400–403.