bluuebunny/crossref_metadata_2025_split huggingface dataset:
A mean motion model of the general circulation
Authors: Williams G. P. , Davies D. R. 
Published: February 2007

AbstractEquations are constructed to represent quasi‐stationary mean flow of momentum and heat on a spherical earth, averaged over a long period of time such as a year and over latitude circles. The crucial shearing Reynolds stress associated with meridional transfer of zonal velocity is assumed to depend linearly on a product of the earth's angular velocity, Ω, and the meridional gradient of mean temperature; the shearing stresses associated with vertical transfer of zonal velocity and of meridional velocity are assumed to depend linearly on the vertical gradients of zonal and of meridional mean velocities respectively, and the mean eddy transfer of heat along a meridian is assumed to depend linearly on the mean meridional temperature gradient. All proportionality coefficients are taken to be independent of latitude. Two forms are assumed for the non‐adiabatic atmospheric heat source function, Q, used in the thermodynamic equation. In the first case Q is assumed known (from analyses of observations) as a function of height and latitude. In the second case, Q incorporates a heating term which is partly controlled by the model itself and represents some of the characteristics of sensible and latent heat transfer. A solution of the basic equations is obtained in both cases in the form of double expansions in powers of two parameters, one depending on Ω and the other on ΔT, the mean annual temperature difference between equator and pole. The solution is evaluated using Fourier techniques.The series expansions are found to be reasonably convergent for realistic values of the various parameters involved, three terms only being required in the ΔT expansion and five terms at most in the Ω expansion, but extensive numerical evaluation by digital computer is involved: the region considered is bounded by the tropopause and lies between the equator and 70° latitude. The computed zonal velocity has the characteristic east‐west variation with latitude and a broad band maximum of 19 m sec−1 and the meridional velocity the characteristic tricellular structure. A poleward eddy angular momentum flux and polar inversion are predicted.The results, through verification of the postulates, add support to the Rossby view of the general circulation in which the cyclonic‐scale eddies act to release potential energy of the atmosphere to supply their own kinetic energy and form the mean zonal kinetic energy. They further indicate the value of the reconstructed ‘austausch’ approach for this problem.
Local interactions between the sea and the air at monthly and annual time scales
Authors: Kraus E. B. , Morrison R. E. 
Published: February 2007

AbstractA statistical analysis of wind, air, dew‐point and sea‐temperature records from all nine weather ships in the North Atlantic shows local variations between years which are highly significant when compared with variations within months. The fluctuations show a consistent pattern with a scale of more than 500 miles in the atmosphere and a persistence over several months. The horizontal extent of sea‐surface temperature anomalies appears to be somewhat smaller, but they tend to last longer than air‐temperature anomalies.Short‐period variations in the flux of latent and sensible heat are due predominantly to atmospheric variations, particularly in winter. The effect of sea‐surface temperature anomalies is somewhat greater in summer, though it becomes significant only on the annual time scale.
The falling motions of loaded cylinders and discs simulating snow crystals
Authors: Jayaweera K. O. L. F. , Mason B. J. 
Published: February 2007

AbstractThe clustering, by wake capture, of thin cylinders and discs as they fall through a viscous liquid has been studied, and the relevance of the observations to the aggregation of snow crystals is discussed. The influence of captured cloud droplets on the orientation and falling motion of columnar and plate‐like snow crystals is inferred from the behaviour, in a viscous liquid, of solid cylinders and discs loaded with small spheres and from the motion in air of loaded discs of thin tissue paper. The orientation in the atmosphere of composite ice crystals in the form of columns with end plates may be inferred from the behaviour of cylinders capped by thin discs in a viscous liquid. These observations on the falling speed, orientation and aerodynamic stability of snow crystals are pertinent to their aggregation into snowflakes, their accretion of cloud droplets and dust particles, and to the optical effects they produce in the atmosphere.
The estimation of vertical diffusion over medium distances of travel
Authors: Thompson N. 
Published: February 2007

AbstractExperiments have been carried out in which the vertical diffusion of a tracer has been measured after several kilometres travel. Simultaneous measurements of atmospheric turbulence provided an opportunity to use the treatment described by Thompson (1965) to estimate the ratio of the Lagrangian and Eulerian scales of turbulence. The scale ratio was again found to increase with an increase in stability, with a variation in magnitude from near unity in unstable conditions to around 15 in moderate stabilities.
Thermal conduction and viscosity and the choice of the upper‐level boundary condition in the theory of atmospheric oscillations
Authors: Giwa F. B. A. 
Published: February 2007

AbstractViscosity and thermal conduction are included in the current tidal oscillation theory. The solution in which the energy density remains finite as height increases is treated. For all equivalent depths for which the tide is oscillatory in the vertical direction, this solution is a wave whose energy propagates upwards, thus suggesting that the choice of ‘energy propagation upwards’ as the upper‐level boundary condition is consistent with the effect of damping at these levels. Similar work by Pekeris is discussed.
On Antarctic pressure variations
Authors: Loewe F. 
Published: February 2007

AbstractThe numerous stations which operated in Antarctica during the International Geophysical Year allow a more detailed study of the local distribution and of the displacements of pressure variations. From six‐hourly pressure data the times of occurrence of identifiable extremes have been determined. They are mostly later at the more westerly stations. For 15 months and seven stations, cross‐correlations of six‐hourly pressure values have been calculated for lags of multiples of six hours between 60 and — 60 hours. The correlations are in most cases highest for pressures at the eastern before the western station. The same result is found if six‐hourly and twenty‐four hourly pressure changes at different stations are correlated instead of the pressures themselves. No correlations of the same size occur if between Little America and Wilkes pressures and pressure changes at a station are correlated with later ones at a more easterly location. The existence and importance of Simpson's ‘antarctic pressure waves’ is thus confirmed.
Day and night measurements of ozone in the Southern Hemisphere
Authors: Kulkarni R. N. 
Published: February 2007

AbstractMeasurements of ozone using Dobson spectrophotometers at night on the moon in low and middle latitudes of the Southern Hemisphere and calculated by the ‘AD’ method did not show any significant difference between day and night. However, the ozone amounts calculated using individual wavelength pairs, without applying the haze correction, usually showed an increase in ozone at night, implying that the apparent increase in ozone was due to an increase in large particle scattering at night.In middle latitudes, at Aspendale, Hay and Hobart, observations at night on the B (λλ 3088/3291) pair of wavelengths showed an apparent decrease of ozone at night. At Darwin, in low latitudes, there was no difference between day and night ozone when calculated on the B pair of wavelengths. This implies that greater radiation is received at the Earth's surface on about λ 3088, in middle latitudes. This enhanced radiation is tentatively attributed to the emission from the Herzberg band of molecular oxygen and to (terrestrial) OH emission at λ 3088, at night in middle latitudes. The latitudinal observations and their interpretations are consistent with existing knowledge regarding these emissions.The absorption coefficients of ozone as calculated from Southern Hemisphere atmospheric measurements at these wavelengths and at these places differ from those obtained by Vigroux, but are consistent with those obtained by Dobson and Ramanathan in the Northern Hemisphere.
Models of cloud‐topped mixed layers under a strong inversion
Authors: Lilly D. K. 
Published: February 2007

AbstractTheoretical models are constructed with the aim of relating, explaining and predicting features of a radiatively active turbulent cloud layer over the sea and under a strong subsidence inversion. Both dry aerosol clouds (no phase change) and wet clouds (with a phase change and latent heat exchanges) are considered. For the wet cloud case an important element of the theory is the requirement that the wet‐bulb potential temperature must increase upwards in the inversion. For both cases entrainment of the upper warm air is hypothesized to lie between upper and lower limits determined from the turbulent energy budget. The dry cloud case is solved for both steady state and transient results, with only the transient behaviour depending on the entrainment hypothesis. Only steady state solutions are presented for the more complex wet cloud case and these differ somewhat for the maximum and minimum entrainment limits. Observational data from Oakland, California are used for comparison with those steady state solutions, with results indicating the essential validity of the approach. Detailed comparisons, especially for determination of the most correct entrainment rate, are hampered both by inadequate measurement of the inversion properties and by uncertainties in the net radiation flux leaving the cloud top. Computations of the latter suggest that several presently used radiation models are still in serious disagreement, at least for application to downward flux under an inversion. It is suggested that the present theory provides a partial explanation of the origin of the trade wind inversion.
Radiative modification of selected vertical temperature distributions
Authors: Staley D. O. , Jurica G. M. 
Published: February 2007

AbstractRadiative cooling rates at closely spaced vertical intervals were determined by the Brooks method applied to several types of soundings. Other cooling processes were neglected, and a new temperature distribution at a later time was determined by forward integration of the cooling rate. By repeating the procedure, temperature distributions were obtained at two‐hour intervals up to 24 hours.The initial temperature distributions included: (a) a relatively moist inversion in the middle troposphere, (b) relatively dry inversions in lower and middle troposphere, within which moisture decreased rapidly upwards, (c) a relatively dry inversion in the upper troposphere, and (d) a smooth temperature distribution having a large moisture inversion. The distribution of cooling rates tended to wipe out the inversion with high moisture throughout (case (a)), and extremes of cooling decreased substantially over the 24‐hr period. In the vicinity of the relatively dry inversions in lower and middle troposphere (case (b)), cooling rates were relatively constant over the 24‐hr period, and so distributed as to maintain the inversion and substantially increase the hydrostatic stability in the lower part of the inversion. Radiative destabilization was noted after a few hours below the bases of the lower two dry inversions (case (b)) and just above the top of the moisture inversion in case (d).The distributions of radiative cooling in the vicinity of a dry frontal zone are consistent with the orientation of isentropes with respect to the frontal zone in vertical cross‐section. Potential vorticity, because of its proportionality to hydrostatic stability, must undergo substantial changes in the vicinity of dry frontal zones.
Tropical cloudiness and rainfall related to pressure and tidal variations
Authors: Brier G. W. , Simpson Joanne 
Published: February 2007

AbstractA definitive statistical relationship is established between tropical cloudiness and rainfall and the semidiurnal solar (S2) atmospheric tide, as manifested in the semi‐diurnal surface pressure variation. Pressure and weather data are used from Batavia (seventy years) and Wake Island (twelve years). TheS2tidal effect is shown to enhance cloudiness and rain near sunrise and sunset, and to suppress them shortly after midday and midnight. The analysis is based on (a) the fact that theS2amplitude varies by 15–20 per cent between months and by more than 100 per cent from day to day and (b) the amplitude of theS2wave as computed from the pressure data at a station is closely related to the 5–6 hourly pressure changes during the periods around 4–5 a.m. to 10 a.m., from 10 a.m. to 4 p.m., etc. The crux of the analysis is the demonstration that days with large 5–6 hourly pressure changes during these periods have large cloudiness changes (in the sense described above) during these same periods relative to days with small 5–6 hourly pressure changes.Possible mechanistic connections betweenS2pressure tendencies and cloud properties are examined. The varying convergence‐divergence field is suggested as the main link. It is shown how the concentration of active cloud updraughts in the Tropics can permit cloudiness to be extremely sensitive to small divergence fields.Finally, large‐scale simultaneous pressure changes over the Pacific Ocean area are shown and related to cloudiness changes. A need for re‐examination of the nature and origins of tropical disturbances is shown to exist, using the concept that possible small (terrestrial or extra‐terrestrial) triggers may set off significant changes in weather both locally and on the synoptic and global scales.
A note on the contributions of mean and eddy terms to the momentum and heat balances of the troposphere and lower stratosphere
Authors: Murgatroyd R. J. 
Published: February 2007

AbstractThe space‐time averaged zonal wind equation has been used in a two dimensional model to infer the mean meridional circulation of the Northern Hemisphere upper troposphere and lower stratosphere at the solstices. A three cell system is found with maximum meridional speed of 120 cm sec−1 in winter and 40 cm sec−1 in summer and vertical speeds of 0.3 cm sec−1 in winter and 0.1 cm sec−1 in summer. The lower stratosphere circulation shows a continuation of the tropospheric cells with speeds decreasing with height.Using these results together with estimates of the eddy convergence terms and the ‘diabatic’ contributions based on values obtained from the literature the component terms in the zonal momentum and heat budgets are listed. In the former, in agreement with other workers, the main balance is between the convergence of the horizontal eddy flux and the mean meridional flow (Coriolis torque) terms. In the latter the balance is principally between the ‘diabatic’ term, the (subsidence) term due to the mean vertical flow and both the horizontal and vertical eddy heat flux convergence terms.The limitations of the data on which the calculations are based are emphasized and estimations of the consequent uncertainties in the results are obtained by repeating the computations with different input data. In particular no measurements are available of the term due to the convergence of the vertical eddy flux of momentum. Most authors have assumed it to be zero but calculations have also been made here using values based on results given by Smagorinsky, Manabe and Holloway (1965) for their 9‐level general circulation model experiments.
Charge distribution in thunderstorm clouds
Authors: Ogawa T. , Brook M. 
Published: February 2007

AbstractThe negative charge involved in lightning flashes to ground is found to be distributed in a manner strongly dependent upon the direction of movement of the storm, and does not, in general, constitute a nearly vertical column as proposed by Malan and Schonland. Based on a study of electric field‐changes measured at two stations 10 km apart involving 539 return strokes from 84 flashes in 10 storms, we conclude that the horizontal component of the in‐cloud channel on the average exceeds the vertical component, and points in the direction of storm motion.An analysis is given of the five methods of Malan and Schonland, on the basis of which we suggest that significant horizontal components are also compatible with their observations of a vertical column, and that the ‘nearly vertical’ aspect of the charge distribution has been over‐emphasized.
Precipitation‐induced mesoscale wind perturbations in the melting layer
Authors: Atlas D. , Tatehira R. , Srivastava R. C. , Marker W. , Carbone R. E. 
Published: February 2007

AbstractDoppler radar observations during widespread frontal precipitation in England on 20 February 1967 show significant perturbations of the wind in and near the melting layer. The analysis suggests the following hypotheses: (i) Mesoscale oscillations of the wind near the melting layer are produced by pressure perturbations due to horizontal variations in cooling by melting snow associated with the precipitation pattern. A simple theoretical analysis of the effect is presented. In simple patterns, the perturbed wind has a maximum on the low pressure side of the rainfall. The perturbations propagate with the velocity of the precipitation generators and their magnitude increases with the precipitation rate. This hypothesis is in accord with the finding that the oscillation in the tangential wind across hurricane rain bands is generally a maximum on the low pressure side of the bands. (ii) Smaller scale wind perturbations were also observed in the melting layer with scale of a few kilometers comparable to those reported by Harrold and Browning (1967). However, unlike their observations, these perturbations did not appear to move with the melting layer winds. A tentative suggestion is made that these may represent wave motions.
A ground‐based instrument for the continuous measurement of charges on cloud particles
Authors: Latham J. , Smith M. H. 
Published: February 2007

AbstractAn instrument has been devised which will measure continuously the charge and dimensions of individual ice crystals or water droplets within clouds at ground level. If its collection efficiency for cloud particles were established it could then also be used to determine particle‐size distributions and volume charge densities inside clouds.A collimated beam of particles passes through a transverse electric field before impinging on a moving belt of 35 mm film coated with Formvar which has been softened immediately prior to exposure to the beam. Each particle is deflected by an amount proportional to its charge‐to‐mass ratio. The dimensions, type and charge of each collected particle can therefore be determined by subsequent analysis of the replicas using a stop‐motion projector allied to a data recording system. If required, the dimensions of selected particles can be determined more precisely using an electron scanning microscope. The minimum detectable charge on a droplet of radius r cm and terminal velocity V cm s−1 is given approximately by qmin ∼ 5 × 10−2 r3 V2 e.s.u.
Measurements of eddy‐fluxes over the sea from an off‐shore oil rig
Authors: Hicks B. B. , Dyer A. J. 
Published: February 2007

AbstractTwo eddy correlation instruments (Fluxatrons) and associated anemometers were installed on the Marlin natural gas platform, which stands in Bass Strait about 60 m deep and 40 km off the Victorian coast (lat. 38° 14′S, long. 148° 13′E). The sensing heads were mounted 5 m above the sea surface on a boom extending from the rig. At this height the rig did not appear to affect the wind flow.The measured Reynolds stresses give an average value of 0.0011 ± 0.0001 for the drag coefficient referred to the 10 m wind speed (31 half hour observations over the wind speed range 2–10 m s−1). Below about 5 m s−1 the drag coefficient is not significantly different from that of an aerodynamically smooth surface. Above this speed, it increases with velocity, reaching about 0.0015 at 10 m s−1.The measured sensible heat‐fluxes are small, showing that evaporation dominates sensible heat in the sea‐air energy budget. There is no reason to dispute the bulk aerodynamic approach, in which the heat‐flux is written as H = p cp d ua Δθa. The data do not allow an accurate estimate of the transfer coefficient, d, which is found here to be 0.0014 (±25 per cent), insignificantly different from the value found for the case of evaporation from inland lakes.Heat budget considerations imply that about 60 per cent of the day‐time net radiation was used to heat the water body.The success of the experiment suggests the feasibility of using oil rigs as platforms for further air‐sea interaction studies. The stability of such platforms, even at very high wind speeds, is particularly attractive.
Fluxes of momentum and mass from 2 km to 28 km at Laverton, Victoria, during the serial sounding experiment, Spring 1966
Authors: Brook R. R. 
Published: February 2007

AbstractThe Laverton Serial Sounding Experiment provided a comprehensive sounding of the atmosphere over a period of one month in the southern Spring of 1966. These data have been analysed to determine the variations of fluxes of mass and horizontal momentum at heights from 2 to 28 km, and the contributions to these fluxes by the mean flow and transient eddies. The co‐spectrum functions of the fluxes were evaluated to obtain contributions to them by eddies of different sizes. The partitioning of the Reynolds stresses (momentum fluxes) by various frequencies is examined for the existence of a ‘spectral gap’ and it is concluded that no definite gap exists in the frequency range examined. A strong quasi‐diurnal mass flux is found in the lower troposphere.
On the development of extratropical cyclones
Authors: Petterssen S. , Smebye S. J. 
Published: February 2007

AbstractCertain synoptic aspects of cyclone development in the lower troposphere are reviewed and two types identified. Type A comprises the well‐known amplifying frontal wave, which is known to produce kinetic energy through a reduction of the baroclinicity within its own domain. Type B is found to be initiated through a finite disturbance in the upper troposphere, and its intensification is accompanied by an augmentation of the baroclinicity and import of kinetic energy, mainly from the jet‐stream region. The energy structures of two storms are described, one being a plain type B case, and, the other representing a type B development modified through the presence of strong fronts. The dissipation of kinetic energy in the surface air is computed and found to constitute an effective brake on cyclone development.