bluuebunny/crossref_metadata_2025_split huggingface dataset:
The vertical distribution of atmospheric ozone over Christchurch, New Zealand
Authors: Hutchings J. W. , Farkas Edith 
Published: February 2007

AbstractThe results of a limited series of ozone‐sonde ascents made at Christchurch, New Zealand (latitude 43.5°S) during 1965‐66 with Brewer‐Mast electro‐chemical sondes are discussed. It is found that the vertical distribution of ozone and the pattern of its seasonal variation is similar to that found at Aspendale (southeastern Australia, latitude 38.0°S), but that the Christchurch ozone concentrations are greater at all atmospheric levels. It is further shown that at Christchurch the horizontal transport of ozone by transient eddies is southward at all levels and that the annual average vertically integrated flux is not very different from that observed at a comparable latitude in the Northern Hemisphere. Consideration of the middle latitude ozone budget tends to indicate a coefficient of vertical eddy diffusion in the lower stratosphere of the order of 105 cm2 s−1 for the Southern Hemisphere middle latitudes. Major assumptions involved in this estimate are pointed out.
A note on the log‐linear velocity profile in stable conditions
Authors: Taylor P. A. 
Published: February 2007

AbstractIf we consider a stably stratified (H<0) constant flux layer, 0 <z <zr, within which we know the heat flux, Hi, and have measured only the mean velocity Ur at one height zr we may wish to determine the friction velocity, u*, by assuming a log‐linear velocity profile with a fixed value for the Monin‐Obukhov parameter, a. This approach leads to a cubic equation for u* which may have either two or no real positive roots. A condition for the existence of positive roots is derived and it is conjectured that the larger of the two roots is the one required. This condition leads to an upper bound, In \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{z_r + z_o}}{{z_o}}} \right) $\end{document} / (2α) on z/L for the applicability of a ‘log‐ linear’ velocity profile.
Precipitation growth at a cold front
Authors: Jonas P. R. , Tabony R. C. 
Published: February 2007

AbstractA simple model of the growth of precipitation particles in cloud systems in which the air flow is known has been used to calculate the growth of hail pellets at a cold front. The calculated pellet sizes and densities, and surface rainfall rates, are consistent with observations. It is shown that in the 3 km deep frontal cloud the larger hail pellets were grown during at least two ascents in the strong updraught. The growth of large pellets depends on the airflow being such as to cause two ascents, and small changes in the airflow can prevent the growth of large hail pellets.
Water vapour budget and precipitation over the Arabian Sea during the northern summer
Authors: Saha K. R. , Bavadekar S. N. 
Published: February 2007

AbstractWater vapour budget of the lower troposphere over the Arabian Sea is studied by computing fluxes across the boundary walls of a rectangular volume around the Arabian Sea during September 1963 and June until September 1964. The net flux divergence is used to estimate total precipitation within the volume after taking into account the total estimated evaporation from the surface of the Arabian Sea. Relative magnitudes of net cross‐equatorial flux of water vapour into the volume and evaporation from the surface of the Arabian Sea appear to suggest that on an average the former may be about 30 per cent larger than the latter.
Some experiments in dynamic initialization for a simple primitive equation model
Authors: Temperton C. 
Published: February 2007

AbstractA number of experiments in dynamic initialization are carried out within the framework of a relatively simple primitive equation model. Some previously suggested variants of initialization schemes based on the Euler‐backward timestep are tested and found wanting. A new scheme is proposed, based on averaging the solutions of the primitive equations at time‐levels separated by a small interval. This scheme is tested, with encouraging results.Theoretical considerations and experimental evidence indicate that both mass‐to‐wind and wind‐to‐mass adjustment should be catered for in a dynamic initialization scheme. This facility can easily be incorporated into the scheme proposed here, and tests confirm the advantages of doing so.
Bounds upon the growth rate of errors in quasi‐nondivergent prediction models
Authors: Davies H. C. 
Published: February 2007

AbstractAn upper bound is placed upon the amplification rate of an arbitrary perturbation imposed upon the observed, initial state of a barotropic flow and a two‐level, quasi‐geostrophic baroclinic flow. The implied lower bound to the predictability of the barotropic flow is a function of the mean energy and the mean enstrophy of the initial perturbation, together with certain mean properties of the observed state. Similar results are obtained for the baroclinic flow.Estimates of the doubling time of an initial perturbation of an observed state that is characteristic of largescale atmospheric motion yields values not far removed from those attained in corresponding numerical predictions. Thus the derived bounds may be useful in assessing the growth of errors in quasi‐nondivergent prediction models.
The evolution of droplet spectra and large droplets by condensation in cumulus clouds
Authors: Mason B. J. , Jonas P. R. 
Published: February 2007

AbstractThe paper describes a relatively simple model of a non‐precipitating cumulus cloud that grows by the ascent of successive spherical thermals through the residues of their predecessors, mixing with the surroundings being determined by the relative velocity and the radius of the thermal. The model appears to account for several important features of the cloud structure and the droplet‐size spectrum that are not produced in models of a single parcel or plume. In particular, it produces modest clouds in 30‐40 min in which the vertical velocity, cloud depth and liquid‐water content agree quite well with observations. The computed droplet spectra closely resemble measured spectra and reproduce the bimodal structure observed by Warner. In model maritime clouds containing small concentrations of droplets, the spectra broaden quite rapidly and produce droplets of r = 25 μm by condensation on nuclei of m = 10−11g in concentrations of order 100 m−3 within half an hour, beyond which size they may continue to grow rapidly by coalescence to precipitation size. However, in continental clouds containing droplet concentrations of a higher order, it is difficult to produce a significant number of droplets of even 20μm radius.
A three‐dimensional primitive equation model of cumulonimbus convection
Authors: Miller M. J. , Pearce R. P. 
Published: February 2007

AbstractThe model is described and the results of three integrations presented. Its main novel features are the inclusion of non‐hydrostatic terms in a pressure co‐ordinate system, and the treatment of flow through the lateral boundaries. The results of the integrations, one with an ambient vertical wind shear and two without, indicate that the cloud dynamics is quite sensitive to assumptions made regarding the cloud microphysics, particularly at the stage when the downdraught is produced.
Periodic variations in stratospheric zonal wind from 20 to 65 km, at 80° N to 70° S
Authors: Belmont A. D. , Dartt D. G. , Nastrom G. D. 
Published: February 2007

AbstractTo help understand the observed variability of zonal wind, the amplitude and phase of five component waves are displayed on height‐latitude sections, 20 to 65 km, 80° N to 70° S using rawinsonde and meteorological rocket data for twelve years. Among the new features are the polar semiannual wave in the Southern Hemisphere, matching that in the Northern Hemisphere. The tropic semiannual wave seems displaced south of the Equator. A terannual wave with 20 m s−1 amplitude is possibly related to the square wave properties of the annual insolational heating at high latitudes. Both the annual and terannual waves appear to have minima north of the Equator.
Mean meridional winds estimated from constant level balloon flights in Southern Hemisphere temperate latitudes
Authors: Angell J. K. 
Published: February 2007

AbstractTemporal and longitudinal variations in mean meridional wind are estimated from GHOST and EOLE constant level balloon flights at 100 and 200 mb in south temperate latitudes during the period 1966/72. At these latitudes there is evidence of about a 0.3 m s−1 poleward flow in winter‐spring and equatorward flow in summer‐autumn, with the oscillation at 100 mb preceding that at 200 mb by 1 to 2 months. This annual oscillation may reflect a direct circulation between summer and winter hemispheres. At 200 mb in south temperate latitudes there is also evidence for about a 0.1 m s−1 poleward flow during the west wind phase, and equatorward flow during the east wind phase, of the quasi‐biennial zonal wind oscillation in the low tropical stratosphere. The significance of this relation has not yet been ascertained. The overall mean equatorward drift of 0.04 m s−1 points up the existence of the Ferrel Cell in the long‐term average. A breakdown of the data by longitude shows that the annual variation in zonal‐average meridional wind is due to large seasonal variations in meridional wind over the South Atlantic.
Secular variations of regional rainfall over India
Authors: Parthasarathy B. , Dhar O. N. 
Published: February 2007

AbstractTrends and periodicities in the annual rainfall of 31 meteorological sub‐divisions of India based on data for over 60 years have been examined by various latest techniques like Mann‐Kendall rank method, low‐pass filter and power spectrum analysis. It is seen that the frequency distribution of annual rainfall for the period of 1901 to 1960 is not normally distributed in some sub‐divisions of the country. Positive trend is noticed over central India and the adjoining parts of the peninsula and also over two smaller areas in north‐west and north‐east India. Only over some parts of eastern India there is negative trend. Increase in mean rainfall for 30 years shows a gradient from the west coast to the interior parts of the country with a maximum over the west coast.The spectral analysis of the annual rainfall of these sub‐divisions shows a significant cycle of range 8.5 to 12.0 years which is mainly seen in and around the arid and semi‐arid regions of Rajasthan, some central parts of India and extreme south peninsula. A cycle of 2.0 to 3.5 years is also observed over large parts of the country mainly over north‐west India, central parts of peninsula and some parts of northeast India.
Planetary waves in the winter mesosphere ‐ preliminary analysis of nimbus 6 PMR results
Authors: Hirota I. , Barnett J. J. 
Published: February 2007

AbstractThe temperature field of the northern hemisphere mesosphere during the mid‐winter of 1975/1976 is described by the use of radiance observations made by the Pressure Modulator Radiometer (PMR) on the Nimbus 6 satellite.A month's average of the radiance field indicates that planetary waves of wavenumbers one and two are of significant amplitude in the winter hemisphere up to the highest level observed by the PMR (∼85 km). These waves show a westward tilt of wave axis with height, and the maximum amplitude is observed in the middle mesosphere to the north of the polar‐night westerly jet.Time series analysis of the zonal mean radiance during the period of a minor stratospheric warming in early 1976 indicates that the stratospheric and lower mesospheric temperature increases with time in the higher latitudes to the north of 30°N, associated with the amplification of wavenumber one, while the upper mesospheric temperature decreases with time at all latitudes.A rough estimate is also given of the time change of the mid‐latitude mean zonal wind during the period of the warming.
Water vapour absorption in the 10–12 μm atmospheric window
Authors: Coffey M. T. 
Published: February 2007

AbstractResults are presented from an experimental programme in the atmosphere to determine water vapour absorption in the 10–12μm atmospheric window. Radiation measurements have been made with upward and downward looking multi‐channel radiometers from an aircraft. Midlatitude and tropical conditions have been studied. the wavelength and temperature dependence of the absorption are presented. Possible causes of the absorption are investigated and dimers of the water molecule are concluded to be the responsible absorbing species.
Hailstorms in the Transvaal on 29 November 1972
Authors: Carte A. E. , Mader G. N. , Triegaardt D. O. 
Published: February 2007

AbstractA broad band of non‐frontal storms moved northwards across a dense hail‐reporting network. the precipitation patterns of two isolated storms that produced hailstones > 5cm in diameter were studied in detail. Both storms gave a burst of large hailstones and then declined in severity, and ultimately merged. Radar reflectivity structures showed both to be essentially unicellular but one showed evidence of pulsating growth. Internal structures of several hundred hailstones from these two storms and a third less severe storm were examined. the growth centres of most were found to be rime but a few were concluded to have been frozen drops. the layering of the hailstones, the fallout pattern on the ground and features of the radar echoes all indicated greater complexity of the two severe storms than a single updraught that steadily built up to a maximum speed then faded out. Deuterium contents, reported in a companion paper, were determined for many of the hailstones. Storms on this day showed a spectrum of behaviour; some were organized multicellular complexes.
The relation between the flux ratio and energy ratio in convectively mixed layers
Authors: Manins P. C. , Turner J. S. 
Published: February 2007

AbstractTwo alternative formulations of the problem of entrainment at the top of a convecting surface layer are in current use. One expresses the mixing in terms of the ratio of the buoyancy flux at the top of the convecting layer to that at the ground, and the other (which is the more fundamental) compares the energy used for entrainment with that produced by the destabilizing flux at the ground. Several authors have proposed similar methods of calculating the latter and relating the two ratios, but we believe these authors are in error because of a fallacious assumption about the nature of the mixing in the practically uniform layer. The present note attempts to resolve this difficulty by using a simple model which considers explicitly the separate contributions of the environment and the surface flux to the density of the mixed layer. We suggest that the physically relevant energy ratio is the increase in potential energy due to the redistribution of the initial density profile compared with the potential energy made available by heating from below.
A limited area nested numerical weather prediction model: Formulation and preliminary results
Authors: Gauntlett D. J. , Leslie L. M. , McGregor J. L. , Hincksman D. R. 
Published: February 2007

AbstractA limited area, six‐level, primitive equations numerical weather prediction model has been developed to provide improved 24‐ to 36‐hour forecasts for the Australian region. Important features of the model include semi‐implicit time differencing, and a nesting procedure which enables boundary values to be updated from a hemispheric spectral model. Preliminary results from the model indicate considerable operational potential.
Estimation of outgoing longwave radiation from meteorological variables accessible from numerical models
Authors: Jensenius John S. , Cahir John J. , Panofsky Hans A. 
Published: February 2007

AbstractA regression equation was developed and tested for directly estimating infrared flux density at the top of the atmosphere from variables available in numerical forecast models. The relation was developed in a stepwise procedure which used observed radiant flux density from the NOAA‐3 satellite in the 10.5 to 12.5 μ window as the predictand and predictors derived from the US National Meteorological Center's Limited Fine Meshm model which are believed to have associations with cloudiness and with temperature.The equation was developed from continental data for the winter of 1974/5 and tested on data for February 1976, for which the weather regime was significantly different. By far the best predictor was the Planck function calculated from a temperature which approaches the boundary layer temperature when the 500mb dewpoint depression is large, and an upper tropospheric temperature when it is small. This variable alone accounted for almost 61% of the variance of the predictand in the initial sample. Four additional predictors increased the explained variance to over 67%. The corresponding variance explained in the test sample increased to over 71%. The distribution of mean fluxes at each gridpoint was especially well described. The mean field estimated by the equation explained over 97% of the variance of the mean observed field in the initial sample and almost 95% in the test sample.On a daily basis, predicted fields of radiant flux density appeared to be somewhat smoother than the observed fields, but the regression equation rather accurately predicted the location of relative radiant flux density minima caused by clouds having cold tops.When combined with a similar relation for reflected shortwave radiation, this equation offers a method of estimating the radiation balance at the top of a numerical model atmosphere which allows for cloudiness change without explicit prediction of cloudiness. The present paper illustrates the method for the restricted case of longwave radiation over a continent in winter.
The application of complex demodulation to meteorological satellite data
Authors: Chapman W. A. , McGregor J. 
Published: February 2007

AbstractA method of performing zonal harmonic analyses on near‐polar orbiting satellite data is presented. This method, known as complex demodulation, yields the time variation of the spectral components of global scale meteorological parameters. Experimental data from the selective chopper radiometers on board the Nimbus 4 and 5 weather satellites are examined in order to gain an insight into the temporal behaviour of the stationary and travelling components of stratospheric zonal temperature fields.
Longwave radiation at the ground: III. A radiometer for the ‘representative angle’
Authors: Dalrymple G. J. , Unsworth M. H. 
Published: February 2007

AbstractThe construction of a directional radiometer for measuring longwave radiation from the atmosphere is described. The instrument had a filter of black polyethylene to exclude solar radiation, and the detector was a thermopile. By analysis of the radiation and heat balances of the thermopile, correction terms are derived for (i) the flux density of radiation received by the thermopile from the filter, and (ii) the dependence of instrument sensitivity on temperature. Measurements with the new instrument of the equivalent flux density below cloudless skies at zenith angle 52.5° agree well with measurements of hemispheric flux density derived from simultaneous measurements with a Linke‐Feussner actinometer.
The Hampstead storm: A numerical simulation of a quasi‐stationary cumulonimbus system
Authors: Miller M. J. 
Published: February 2007

AbstractA numerical simulation of the storm which occurred over north London on 14 August 1975 is presented. This storm was notable in giving record rainfall totals for the London area while confining the rainfall to an area of about 100km2 despite lasting three hours. The results of the simulation define a distinctive model of the storm dynamics, featuring an impulsive yet quasi‐stationary system of cumulonimbus which contributed successively to the rainfall over a limited area. Furthermore the simulation emphasizes the dominant role of the downdraught outflow which establishes and sustains the storm through its interaction with the low‐level flow. A mechanism by which the prevailing vector shear maintains the storm is presented. Trajectories computed for the simulated storm show an interlocking updraught/downdraught structure similar to that proposed by Browning (1964).In order to simulate the observed high surface rainfall it was found necessary to model the high fallspeeds associated with hail by a simple modification to the ‘warm’ rain parameterization. The simulated and observed rainfall patterns compare remarkably well.The localization of the storm is considered but the local orography is thought to have no significant influence. Dynamical points arising from the model identify aspects of storm modelling that require further investigation.
Structural and stochastic analysis of a zero‐dimensional climate system
Authors: Fraedrich Klaus 
Published: February 2007

AbstractAn ‘almost trivial’ climate system of geometrical dimension zero is analysed, the complexity of which has been reduced to a minimum. It can be simply described as the globally averaged energy flux balance between infrared emission and solar heat input, expanded by a linear albedo‐temperature feedback. This nonlinear and time‐dependent climate model is formulated as a gradient system of a potential and can be analysed without explicit time integration. It includes many of the results which are also exhibited by one‐dimensional energy balance models. Two equilibrium solutions appear. The stable one is characterized by the interglacial, whereas the unstable equilibrium defines a lower bound for temperature (state variable) changes which the system can absorb. Beyond a threshold of an external parameter combination (fold catastrophe) no equilibria exist so that the system attains a ‘deep freeze’ climate situation. A −2 power law describes the linear response of the (internally stable) system to weather fluctuations.
On the interaction of topography and Ekman boundary layer pumping in a stratified atmosphere
Authors: Mason P. J. , Sykes R. I. 
Published: February 2007

AbstractA simple theory of the interaction of topography and Ekman boundary layer pumping in a stratified atmosphere is presented, together with numerical solutions of the corresponding two‐dimensional Navier‐Stokes equation problem. Numerical results for flow over a two‐dimensional ridge confirm theoretical predictions that stratification enhances momentum coupling and produces a low‐level jet parallel to the ridge.
A numerical advection scheme with small phase speed errors
Authors: Gadd A. J. 
Published: February 2007

AbstractIt is demonstrated that, for linear advection in one space dimension, a simple modification to the well‐known Lax‐Wendroff integration scheme leads to a substantial reduction in phase speed errors. The modification is designed in such a way that no additional restriction is placed on the timestep used in an integration. The improved performance is comparable or superior to that of previously proposed advection schemes, yet it is achieved without recourse to expensive or cumbersome computations.The new scheme is readily extended to two space dimensions and has been used in numerical weather prediction and sea wave modelling in the Meteorological Office. An example is given of an improved numerical forecast of the 500 mb height field which was obtained by applying the new scheme in the operational 10‐level numerical weather prediction model.