bluuebunny/crossref_metadata_2025 huggingface dataset:
Penetrative convection in stably stratified fluids
Authors: Saunders Peter M.
Published: January 2012

The downward convection of discrete masses of heavy fluid, called thermals, in a gravitationally stable environment is studied experimentally. For simplicity the ambient stratification is chosen to have a discontinuous two-layer structure with fluid of uniform density in each layer. When released into the homogeneous upper layer the thermal acquires the circulation of a turbulent ring vortex as reported earlier. For weak stratifications, which are however capable of halting the thermal, this circulation is destroyed in a dramatic fashion during the penetration of the lower layer; restoring buoyancy forces then develop a reversed circulation as the thermal flattens and spreads. For strong stratifications no reversal of the circulation occurs, rather the flattening and spreading of the thermal is associated with a gradual decay of the original circulation.

A dimensional argument is proposed to indicate the parameters which determine the extreme penetration of the thermal into the lower layer: this is confirmed by experiment.

In order to generalize the results to more realistic geophysical cases a mechanistic description of thermal behaviour is put forward. The treatment is shown to rationalize the data for environments with (a) neutral stratification, (b) a discontinuous two-layer structure and (c) constant density gradient. Thermal behaviour in a stratification consisting of (a) surmounted by (c) is then predicted.

Observations made by the author of the penetration of tall cumulus clouds into the sub-tropical stratosphere permit a test of the applicability of this model in one geophysical area. For every 1 km of penetration it is deduced that convective motions have an average vertical intensity of 10 m/sec: this prediction is shown to be in good agreement with the limited observational data.
On truncation errors due to vertical differences in various numerical prediction models
Authors: Wiin-Nielsen A.
Published: January 2012

Some estimates of truncation errors due to vertical finite differences are given. The truncation errors amount to at most 10 % in the phase-speed of the basic mode in a model atmosphere in which the vertical shear of the basic, zonal flow vanishes. An increase of the vertical resolution results in rapidly decreasing truncation errors in this case.

In a model atmosphere, in which the vertical windshear is different from zero, and the static stability parameter is a function of pressure, we find small truncation errors in the initial displacement of the wave, but large errors in the initial amplification.

The initial development of a baroclinic wave is evaluated in three different baroclinic models. The models differ only in the vertical variation of the static stability parameter which is a simple function of pressure in the first model, a constant in the next and zero in the third model. It is shown that the vertical variation of static stability is important for the amplification and the slope of the wave in the vertical direction.

The initial change of the kinetic energy in the models is computed as a function of wave-length. It is shown that the change of kinetic energy is larger in the models where the static stability parameter is constant or zero than in the models where it varies with pressure.

The last section contains some comments on the upper boundary condition. It is shown that the conditions ω = 0 and ϕ < ∞ (ϕ = geopotential) at the upper boundary are equivalent in certain problems.
On the possibility of ice cloud formation at the mesopause
Authors: Hesstvedt Eigil
Published: January 2012

As a contribution to the discussion about the nature of noctilucent clouds some aspects of the ice particle hypothesis are considered. A model of an ice cloud is computed, assuming a temperature profile and wave motions in agreement with observations. Some of the observed characteristics of noctilucent clouds are well reproduced by the model. Similar computations for stratiform clouds show that a diffusion coefficient of the order 107 cm2/sec seems to be required to keep particle sizes within the observed range. It is concluded that the ice particle theory and the cosmic dust theory should be considered as equally important in future studies of noctilucent clouds.
A theoretical analysis of lee wave clouds observed by Tiros I
Authors: Döös Bo R.
Published: January 2012

A Tiros I cloud photograph taken April 18, 1960 over the southern part of South America is examined. The clouds were very regularly orientated in parallel bands on the lee side of the Andes. The cloud pattern is assumed to be quasi-stationary. It seems to be quite clear that the clouds are formed by the waves which are set up in the air flow over the mountain range. The wind direction varied little with height and was almost perpendicular to the mountain. The observed wave length is compared with a theoretically computed value obtained by using a method previously presented by the author (Döös, 1961). The agreement between these values is good. The amplitude of the disturbances produced by the mountain has also been evaluated. For comparison the wave length has also been evaluated by means of the parcel method.
An entraining jet model for cumulo-nimbus updraughts
Authors: Squireas P. , Turner J. S.
Published: January 2012

A model of a cumulo-nimbus updraught is presented, based on a steady-state, turbulent, condensing plume, entraining environmental air according to the simple law that the inflow velocity at any height is proportional to the upward velocity of the plume.

With this model, the shape of the cloud as well as its other properties follow from the dynamics, and cloud development is size-dependent. The virtual temperature excess at cloud base is taken as zero; this seems the only appropriate assumption for a steady-state plume model. The thermodynamical treatment is made with few approximations, and the effect of freezing on the dynamics is included in a simple fashion. Some preliminary calculations result in realistic cloud shapes and reasonable values for the internal properties.
On Atmospheric Energy Conversions Between the Zonal Flow and the Eddies
Authors: Wiin-Nielsen A. , Brown John A. , Drake Margaret
Published: January 2012

Energy transformations between the zonal mean and the eddies have been computed from observed data for a single winter month, January 1962. The available data were the height fields of the 850, 700, 500, 300 and 200 mb surfaces. Our calculations are therefore based on the geostrophic or balanced approximations. The horizontal fields of the streamfunction and the thickness are written as one-dimensional Fourier series, and the energy transformation between the zonal mean and the different longitudinal wave-numbers are evaluated. In order to evaluate the energy transformations in the wave number regime, it is necessary to compute the meridional transports of momentum and heat as a function of the wave number. These results appear therefore as useful by-products of the calculations. The main conclusions which can be made on the basis of the calculations are: The maximum tramport of sensible heat occurs in the middle latitudes and at the lower elevations. More than 50% of the transport of sensible heat is carried out by wave numbers 1 to 4, while the next four wave numbers (5 to 8) transport half this amount. The transport of momentum is toward the north south of about 55° N and toward the south north of this latitude. The maximum northward transport of momentum occurs at 35° N at higher elevations, while the maximum southward transport takes place at 05'N also at higher elevations. About 50% of the northward transport of momentum is carried out by wave numbers 1 to 4 and about 30% by the next four wave numbers (5 to 8). The conversion of zonal available potential energy to eddy available potential energy is found to be positive for almost all wave numbers with a single maximum around the wave numbers 2 and 3. The conversion of eddy kinetic energy to zonal kinetic energy is found to be positive when summed over all wave numbers. The conversion is much smaller than the conversion mentioned in 3. The spectrum is very irregular showing positive conversions for the small wave numbers, but negative conversions for some of the larger wave numbers. The conclusions mentioned above are tentative, since they are baaed on data from a single winter month. Computations for other winter months and for other semons are being planned.
The Global Circulation Features of the Troposphere between the Equator and 40°N, based on a Single Day’s Data: Part 1. The structure of the basic meteorological jields
Authors: Defant Friedrich , Van de Boogaard Henry M. E.
Published: January 2012

The atmospheric circulation during a single day (December 12, 1957) between the equator and latitude 40° N has been investigated. Using the extensive ICY data the fields of the geopotential height and the two horizontal velocity components have been analyzed for ten isobaric levels and the zonal means of these variables computed. The Hadley circulation cell obtained for this single day agrees quite well with previous mean values computed for a month or a season. The results suggest that the mean circulation in tropical latitudes can be obtained with fair accuracy from analysis of a single day or of a period much shorter than those commonly used.
Measurement of small-scale oceanic motions with neutrally-buoyant flloats
Authors: Pochapsky T. E.
Published: January 2012

The movement of water in the ocean waa studied by following 1 3 motions of instrumented neutrally-buoyant floats. Measurements were made at various depths in the Caribbean Sea and in the Atlantic Ocean several hundred miles east of Bermuda. There was a continuous vertical bobbing of the floats, and two floats at nearly the same depth separated at an uneven rate in time. Near the surface, vertical displacements of approximately 3 m took place during periods of 10 to 30 minutes, and movements of approximately 30 m took place over a period of tens of hours. The slow large-amplitude motions were probably forced by semidiurnal tides in the Caribbean. Vertical movements at depths near 1000 m in both operating areas amounted to approximately 10 m over periods of 1 to 2 hours.

Floats at their equilibrium depths do not faithfully follow the movements of the water environment. An approximate solution is derived for the response of a float to an internal wave. It was found that a resonance causes the float movements to exceed the water displacements at the shorter periods whereas the stiffness of the float tends to keep it from moving in deep water where the density gradient is small.
An initial value problem in the theory of baroclinic instability
Authors: Pedlosky Joseph
Published: January 2012

A discussion of the initial value problem for the beroclinic model of Eady is presented. The completeness of the eigen-solutions is discussed. It is shown that a continuous spectrum of waves is required to supplement the normal mode solutions in order to represent the evolution of an arbitrary disturbance, but that the stability properties of the flow are properly described by the normal mode solutions.
The structure of the Ekman layer for geostrophic flows with lateral shear
Authors: Benton George S. , Lipps Frank B. , Tuann Shih-Yu
Published: January 2012

A generalized Ekman flow is obtained for the boundary layer of a semi-infinite, rotating homogeneous fluid with lateral variation in the horizontal velocity components far from the boundary surface. The fields of motion considered include uni-directional motion with lateral shear, symmetric and elongated eddies, and cols. A solution for the first of these cases is obtained to fifth order; for the others, to second order. In all cases the magnitude of the vertical velocities induced by convergence in the boundary layer is greater for systems with negative relative vorticity than for systems with positive relative vorticity. The result differs substantially from first-order theory, for which the magnitude of the vertical velocity is proportional to the relative vorticity. A number of meteorological applications are considered.
On the mean meridional circulation in the presence of a steady state, symmetric, circumpolar vortex
Authors: Gilman Peter A.
Published: January 2012

p>The steady state equations governing the “forced” (in the sense of Kuo, 1956) mean meridional circulation in the presence of a circular vortex are presented, and it is shown that a constraining relation must exist between the sources of heat and momentum (eddy convergences, diabatic heating, and friction) and the parameters of the zonal mean state (zonal vertical wind shear, meridional temperature gradient, absolute vorticity, and static stability).In the case of general heat and momentum forcing, solutions for vertical motion ω are obtained explicitly. These solutions involve integrals along the characteristics of the equations, which are isolines of potential temperature and absolute angular momentum. In the special case of no heat or momentum forcing present, it is shown that a necessary but not sufficient condition for the existence of a “free” mean meridional circulation is that f = Z Ri (called resonance, after Kuo 1956) where Z is the absolute vorticity and Ri is the Richardson number. Equivalently, the characteristics of angular momentum and potential temperature must coincide. It is shown by means of the characteristics that the existence of a region in which the absolute vorticity, measured on an isobaric surface, is negative, may be a sufficient condition. The necessary condition implies that the static stability is also negative in such a region. The conclusion that such free circulations in the atmosphere cannot exist in the mean state agrees with Kuo, but the criterion is somewhat different.In the general forcing case, a possible constraining relationship is derived, and its usefulness considered. Simpler formulae are presented which hold along lines on which one of the components of the meridional circulation vanishes. By considering also the ratio of the components of the meridional circulation along lines on which either the momentum or the heat source functions vanish, a consistency picture between the positioning of the mean meridional cells and the sources and sinks of momentum and heat is developed. In particular, it is shown that lines of vanishing heat or momentum source cannot, in general, be in phase. Such lines must cross at the “center” of each cell (where both components of the circulation are zero). The lines of zero momentum source must slope generally upward toward the equator, in general agreement with observation. For the constraints to be consistent with the observed counter-gradient transport of heat in the lower stratosphere, the lowest layer of cells must extend into the lower stratosphere. Equatorward counter-gradient transport of heat in the troposphere in very low and very high latitudes is also suggested.The implications for observational and numerical model studies of the general circulation are briefly discussed.
Note on the stability of water stratified by both salt and heat
Authors: Walin Gösta
Published: January 2012

The stability of water stratified by both salt and heat is considered. A new criterium complementing the one derived earlier by Stern (1960) is found. It is demonstrated that, contrary to ordinary gravitational convection, convection against a stable density gradient will generally occur on a scale limited by internal parameters and not by the dimensions of the vessel. This limits the transporting capacity of the convection and thus reduces its importance. The characteristic scale that will dominate the instability is derived.
A diagnostic study of tropospheric diabatic heating and the generation of available potential energy
Authors: Brown John A.
Published: January 2012

Calculations of the horizontal distribution of mid-tropospheric diabatic heating have been made through use of the first law of thermodynamics in conjunction with a simplified form of the vorticity equation. Objective analyses of the geopotential heights of the 850 and 500 mb surfaces over a region extending from the pole southward to approximately 15° N were utilized. Calculations of the daily distributions of the heat sources and sinks were obtained for the following months: January 1959, 1962, 1963; April 1961, 1962; July 1961, 1962; and October 1961, 1962. The daily distributions were then averaged within each month, and one of the resulting monthly distributions for each season is presented. Furthermore, the 9 monthly averaged zonal heating profiles are presented together with the latitudinal variation of the heat flux required to maintain these profiles.The zonal and eddy components of the generation of available potential energy were computed from the daily 500–850 mb thickness and heating patterns. The averaged zonal profiles of each component for each of the 9 months is presented. Furthermore, through a linear Fourier analysis method the eddy generation of available potential energy was obtained in the wave-number regime. The average monthly contribution and the standard deviation of the daily values were obtained for each of the 9 months for each harmonic from n = 1 to n = 20.The results of the monthly averaged heating patterns indicate that relatively intense heat sources and sinks exist during the winter months while the least intense ones exist in the summer months. An annual zonal heating maximum of 4×10-3 kj t-1 sec-1 was found near 40° N and intense cooling existed in the high latitudes. All monthly averaged values of the zonal generation of available potential energy were positive with maximum values obtained for the winter months and minimum values obtained for the summer months. Results indicate that for the troposphere the available potential energy is generally destroyed by the eddies in all seasons except summer with the greatest destructions occurring in winter. Also, during winter the long waves, n = 1 to 5, are responsible for the majority of this destruction. The annual average of the zonal generation of available potential energy for the troposphere obtained from the 9 months considered here was + 19×10-4 kj m-2 sec-1 and the corresponding value for the eddy generation was -9×10-4 kj m-2 sec-1.
On the scale analysis of traveling planetary waves
Authors: Deland Raymond J.
Published: January 2012

In a well-known study, BURUER (1958) analyzed the importance of the major terms in the vorticity equation, with particular attention to the planetary waves of greatest scale. He concluded that the vorticity equation becomes simply a “balance equation” equivalent to the geostrophic approximation for the largest-scale waves. The purpose of this note is to show that the vorticity equation does retain some useful predictive and diagnostic properties when applied to planetary waves.
Cellular convection with nonisotropic eddys
Authors: Ray Durga
Published: January 2012

The effect on the critical Rayleigh number and thus the effects on the ratio of cell width to cell height is found due to the consideration of nonisotropic properties of the eddy viscosities and conductivities in atmospheric cellular convection.
Observations of the upper atmosphere by optical radar in Alaska and Sweden during the summer 1964
Authors: Fiocco G. , Grams G.
Published: January 2012

Optical radar observations were carried out at high latitudes simultaneously from two stations at widely separated longitudes. Some measurements related to the optical thickness of noctilucent clouds are reported.
Swedish Meteorological Research 1939–19481
Authors: Ångström Ander
Published: January 2012

U. G. Straitline boring machine from the Canadian Longyear Co. will be used. The
structure of the upper parts of the frozen firn will also be carefully examined in open
shafts. Besides these more specific investigations, the amounts and differents kinds of
accumulation material (direct precipitation and snow drift) will be determined, as well
as the ablation quantity (melting, evaporation, and wind corrosion).
The Behavior of Jet Streams over Eastern North America during January and February
1948
Authors: Phillips Norman A.
Published: January 2012

A graph of the latitude of jet streams at 80° W longitude for a 49-day period in
the winter of 1947–8 shows that the jet stream undergoes changes which appear as
discontinuities on such a graph. Several cases are discussed which illustrate the manner
in which these discontinuities appear. The new jets so formed then appear to experience
a southward displacement before their disappearance. Accompanying the southward
displacement at this longitude is a disappearance of the solenoidal field accompanying
the jet in the lower troposphere, and an increase of the potential temperature in the
center of the jet.
Discussion of the Origin of the Terrestrial and Solar Magnetic Fields
Authors: Alfvén H.
Published: January 2012

The origin of the terrestrial and solar magnetic fields is discussed. An original
meridional field can by hydrodynamic motion get an east-west component. It is pointed
out that this component cannot exceed the order of magnitude of the original field. If
it does, the field becomes unstable and an increase of the meridional component is
caused. The possibility of finding an amplifying mechanism of this type is
considered.
Geostrophic Departures in the Jet Stream
Authors: Starr Victor P.
Published: January 2012

The effect of gradients in the cross-current eddy motions on the geostrophic balance is illustrated by means of an integrated model. It is suggested that gradients of the Reynolds stress associated with such eddy motions in the atmosphere and in the oceans may lead to sensible average geostrophic departures which appear as a normal inertial effect in eddying currents.
Blocking Action in the Middle Troposphere and its Effect upon Regional Climate: I.
An Aerological Study of Blocking Action
Authors: Rex Daniel F.
Published: January 2012

A comparative study of five cases of blocking action in the upper westerlies is
presented with the two-fold objective of obtaining a more complete description of this
phenomenon and of attempting an explanation of its initiation, development and
dissipation in terms of parameters derived from an hydraulic analogue. The effect of
European blocking upon the zonal and meridional circulation indices and the rôle of
blocking in the evolution of hemispheric circulation patterns are discussed. In Part II,
to be published later, the results of a preliminary semi-statistical analysis of
blocking action, together with a description of the regional precipitation and mean
surface-temperature anomalies produced by blocking, are presented. The statistical
results obtained are discussed in relation to recent climatic fluktuations.
On the Influence of the Earth’s Orography on the General Character of the
Westerlies
Authors: Bolin B.
Published: January 2012

The upper westerlies in middle latitudes possess, in the mean, a wave-like
character which has been explained as a result of thermal contrasts between land and
sea. On the other hand, recent theoretical investigations by QUENEY, CHARNEY and
ELIASSEN have shown that an obstacle of the dimensions of the Rocky Mountains generates
a wave pattern downstream whose scale is comparable to the observed mean waves. In the
present paper these theoretical studies are extended, and an attempt is made to discuss,
in a general way, the influence of the northern hemisphere mountains on the character of
the westerlies. Finally the paper points out some of the climatic consequences of the
proposed dynamic-topographic control of the prevailing flow patterns.
Note on the Dynamics of the Antarctic Circumpolar Current
Authors: Munk W. H. , Palmén E.
Published: January 2012

Unlike all other major ocean currents, the Antarctic Circumpolar Current probably does not have sufficient frictional stress applied at its lateral boundaries to balance the wind stress. The balancing stress is probably applied at the bottom, largely where the major submarine ridges lie in the path of the current. The meridional circulation provides a mechanism for extending the current to a large enough depth to make this possible.
Der Mechanismus des meteorologischen Lärmes
Authors: Hinkelmann K.
Published: January 2012

Using a simple atmospheric model, the difference between the solutions of the primitive and the quasi-hydrostatic equations is demonstrated. The results show that the quasi-hydrostatic processes are largely determined by the initial field of pressure wherever the meteorological “noise”-phenomena (in the form of short-period oscillations about a trend of the meteorological elements) depend on the initial field of the non-geostrophic windcomponents. This trend can be computed with sufficient accurracy also by a numerical integration of the primitive equations, which are mathematically simpler to handle than the quasi-hydrostatic equations.

In this case the initial wind fields can be computed from the observed pressure field by using the geostrophic approximation.

To find the trend the results have to be smoothed.
Calculation of the Ionization due to Radioactive Substances in the Ground
Authors: Hultqvist Bengt
Published: January 2012

In earlier calculations it seems not to have been considered that the penetrating radiation from the ground can, independent of the density and composition of the ground, be expressed by the simple formula I = C × S, where S is the proportion of radioactive element in g/g and C is a constant. Formulas for the ionization in the case when the ground is covered with an absorber of greater density than air, or when the radiation travels through air for long distances, are derived. The ionization from various minerals is calculated and is found to agree in magnitude with measured values. Curves, showing the decrease in the ionization as a function of the depth of snow cover, are given for three different values of snow density. The decrease in the dose rate with the altitude above the earth's surface is shown graphically.
Some Remarks on High-speed Automatic Computers and their Use in Meteorology
Authors: Platzman George W.
Published: January 2012

The logical design of an electronic digital computer is described. A simple computation problem is proposed; this is used to illustrate the main steps leading to formulation of a problem for machine computation – the propram and the flow diagram. In conclusion, some general comments are made concerning areas of application of high-speed computers in meteorology.
Influence of Suspended and Dissolved Matter on the Transparency of Sea Water
Authors: Jerlov N. G.
Published: January 2012

The transparency at different levels in the sea as recorded by means of a transparency-meter is compared with the distribution of suspended particles studied with the aid of a Tyndall-meter. A simple procedure is used to distinguish between different components of light extinction and to derive values of the content of the dissolved yellow substance. The distribution of yellow substance is illustrated for the transition area between the Baltic and the Skagerrak and for the outflow of the Gota Älv. It is emphasized that the content of yellow substance may often be considered as a characteristic property of a water mass.
Variability of Summer Temperature in Sweden and its Connection with Changes in the General Circulation
Authors: Wallén C. C.
Published: January 2012

A method of calculating moving standard deviations to give an idea of long-periodic fluctuations in the interannual variability of summer temperature is described and discussed from a statistical point of view. The method was applied to summer temperature records from 15 stations in Sweden and changes in the variability at those stations are treated. In addition the actual variability during the period 1920—39 is determined and compared to the interdiurnal variability of the same period.

In the second part of this investigation are studied frequency fluctuations of different circulation patterns over southern Scandinavia based upon the catalogue of daily weather situations during the period 1881—1950 published by the German Weather Service of the U.S. Zone in 1952. These fluctuations are compared with changes in the summer-temperature and its variability in South Sweden during the same period. It is found that the recent rise of summer temperature has been connected with a definite decrease in frequency of north-meridional situations over Europe and with an increase of south and warm-meridional cases as well as zonal situations. High variability seems to be connected with meridional circulation, low variability with zonal circulation. In a special chapter the fluctuations in variability of the Stockholm summer temperature since 1756 are discussed.
The Adjustment of a Non-balanced Velocity Field towards Geostrophic Equilibrium in a Stratified Fluid
Authors: Bolin Bert
Published: January 2012

The previous work by ROSSBY and CAHN on the adjustment of a non-balanced velocity field towards geostrophic equilibrium has been generalized to incorporate the corresponding process in a stratified but incompressible fluid. It is shown that the character of the process essentially depends upon the width of the current, the velocity profile in the vertical and the vertical density gradient. As long as the vertical density gradient is small the adjustment of the mean motion of the fluid (∫0D0Udz) exactly corresponds to the one described by CAHN. On the other hand vertical variations of the unbalanced motion will set up internal oscillations which have considerable larger (vertical) amplitudes than is found for the adjustment of the mean motion. Furthermore, the speed of propagation of the gravity inertia waves thus generated (cK) is considerably smaller than that of the waves generated during the adjustment of the mean motion (c0). For values of the vertical density gradient as found in the oceans cK < 0.05 c0. In the final state of equilibrium the mean motion of the fluid will be approximately the same as before the adjustment, while a considerable smoothing of the vertical gradients of the velocity field will take place, the more the broader the original current is.
The Interaction between a Mean Flow and Random Disturbances
Authors: Lorenz Edward N.
Published: January 2012

The study of the statistical properties of ensembles of hydrodynamical systems may be called statistical hydrodynamics. It is recommended that statistical hydrodynamics be applied to certain problems which have not previously been looked upon as statistical problems.

Statistical hydrodynamics is applied to the problem of the interaction between a mean flow an a superposed disturbance, in a two-dimensional homogeneous incompressible nonviscous fluid. The ensemble of all disturbances which may individually be superposed upon a given mean flow is assumed to be random, in the sense that it is unaltered if each disturbance is subjected to a change of sign, a translation in space, or a rotation. It is found that, ensemble-average-wise, kinetic energy is transferred from the disturbances to the mean flow if the mean flow is of small variance and coarse detail and the disturbances are on the average of large amplitude and fine detail, while kinetic energy is transferred in the opposite direction if the opposite situation exists.

This result is applied to the problem of the maintenance of kinetic energy in the earth’s atmosphere against the dissipative effect of friction. There is some evidence that both the total kinetic energy and the kinetic energy of the mean flow can be maintained through the addition of new disturbances which form random ensembles, but that they can be maintained more efficiently, and probably are maintained, by the addition of new disturbances with a systematic lack of randomness.
Results of Forecasting with the Barotropic Model on an Electronic Computer (BESK)
Authors: Staff Members
Published: January 2012

A series of twenty-four 24-hour forecasts have been completed using the barotropic model of the atmosphere. The results of these forecasts are better than previous tests with this model have indicated. The average correlation coefficient between computed and observed height changes of the 500 mb surface is 0.77, the error in the forecast height changes is 89 m against an average observed change of IZI m. The errors are mainly due to the following factors:

Erroneous assumptions at the boundary of the forecast area.

Inaccurate analysis of the initial data over the Atlantic.

Inaccuracy in forecasting components of the niotion of a scale only a few times larger than the grid size.

Baroclinic developments.

The computations indicate that the present results may be improved considerably by trying to eliminate errors listed under (1)–(3).
Energy Transformations and Meridional Circulations associated with simple Baroclinic Waves in a two-level, Quasi-geostrophic Model
Authors: Phillips Norman A.
Published: January 2012

The changes in geostrophic kinetic energy predicted by the “2 – ½ dimensional” quasi-geostrophic vorticity equations without friction are shown to be compatible with the mechanical energy equation. The second-order effects on a zonal current due to the presence of very simple unstable baroclinic waves are then analysed, using a two-level model of finite lateral width without friction or heat sources. In addition to the poleward transport of sensible heat and the creation of kinetic energy by these waves, it is shown that they are accompanied in this model by a weak meridional circulation. This circulation consists of an indirect cell in middle latitudes with direct cells to the north and south. The possible importance of this mechanism in providing appropriately distributed sources and sinks of relative zonal momentum (and therefore in prescribing the distribution with latitude of the surface zonal winds) is demonstrated with the aid of Widger's observations of the horizontal momentum transfer by eddies during January 1946. Finally it is shown that about 95 per cent of the perturbation energy in the unstable waves of this type comes from the “potential energy” of the basic current, the small remainder coming from the kinetic energy of that current.
Variations of the Cosmic Ray Intensity During Magnetic Storms
Authors: Brunberg Ernst-Åke , Dattner Adam
Published: January 2012

A simple mechanism has been suggested by H. Alfvén to explain the main features of the variation of cosmic ray intensity during magnetic storms.

Cosmic ray particles are accelerated or retarded in the electric fields of ionized beams, which are sent out from the sun. Particle orbits hitting the earth have been calculated for different momenta and for solar magnetic fields decreasing with distance as r–3, r–2 and r–1. The influence on the particles of beams of different length and breadth has been analyzed.

A beam length of a few times the orbital radius of the earth and particles with momenta in the range 20–40 GeV Z/c give a time variation in cosmic ray intensity similar to the variation measured during a magnetic storm. This requires a solar magnetic field of 10–5 gauss at the earth’s orbit.
A Note on the Integration of the Vorticity Equation for Quasi-Geostrophic Flow
Authors: Thompson Philip D.
Published: January 2012

By the transformation of integrals arising from the solution of the “quasi-geostrophic” equations for barotropic and simple types of baroclinic flow, it is shown that the isobaric height tendency can be expressed in terms of first derivatives of the heights of isobaric surfaces. This demonstrates that the procedure by which the equations are solved must tend to cancel or “average out” the large percentage errors in the geostrophic vorticity advection–i.e. errors in second and third order finite-differences. The height tendency may be computed by a simple graphical procedure, which is carried out directly on analyzed contour charts and which involves a minimum of multiplications.
A Theoretical and Experimental Study of Cellular Convection in Rotating Fluids
Authors: Nakagawa Yoshinari , Frenzen Paul
Published: January 2012

The stabilizing and cell-shape changing influence of a basic rotation upon thermally produced cellular circulations are developed in a first order, perturbation theory. The theoretical possibility of a special “overstable” oscillating mode in certain fluids under the influence of rotation is recognized. In this preliminary report, the theory obtained for ordinary convection is compared to results obtained in laboratory experiments with rotating cylinders of water, and the existence of the overstable oscillating mode is demonstrated experimentally. Several possible applications of the theoretical results to atmospheric convection are developed by means of numerical examples, including models that are consistent with the observed association of deep convection with cyclonic relative vorticity and the distribution of clouds in regularly spaced clear and cloudy areas.
Studies on the General Development of Motion in a Two-Dimensional, Ideal Fluid
Authors: Welander Pierre
Published: January 2012

The purpose of this paper is to discuss qualitatively certain kinds of asymptotic motion in a two-dimensional, ideal fluid by help of methods of statistical mechanics. It is stressed that the final development of such a fluid cannot be adequately described by use of the ordinary equations of motion, but that a “coarse grain” representation should be used. In this representation, the development is characterized by the forming of a single, large vortex accompanied by a certain non-viscous dissipation. The final equilibrium is probably reached almost explosively after a finite time. Some experiments which are carried out seem to support this result. In the earlier stages of development we may expect to have some kind of a quasi-equilibrium motion. It is attempted to find conditions under which such a motion can exist, by studies of a point-vortex model.
Artificial Snowfall from Mountain Clouds
Authors: Ludlam F. H.
Published: January 2012

A tentative theory of provoking snowfall from simple orographic clouds is composed, using simplifying assumptions, and it is shown reasonable to suppose that winter snowfall on Central Swedish mountains might be substantially increased by skillful seeding of supercooled mountain clouds.
The Equatorial Undercurrent in the Light of the Vorticity Equation
Authors: Fofonoff N. P. , Montgomery R. B.
Published: January 2012

The Equatorial Undercurrent, recently observed in the central Pacific Ocean by Cromwell, Montgomery, and Stroup, is a narrow eastward current occupying the lower part of the surface layer at the equator. In the present study the Undercurrent, treated as a permanent feature of the oceanic circulation, is found to be consistent with the conservation of absolute cyclonic vorticity in the equatorward flow comprising one segment of the meridional circulation. The continental barriers permit the formation of the longitudinal pressure-gradient component essential for the existence of the Undercurrent.
A Study of Oceanic Fronts
Authors: Cromwell Townsend , Reid, Jr. Joseph L.
Published: January 2012

Oceanic fronts and frontal layers are defined. Temperature data obtained at two fronts in the equatorial Pacific are presented and a particular circulation, considered basic to the existence of a front, is proposed.

Vertically isothermal warm water overlies the stable frontal layer. This suggests that vertical mixing in the isothermal water maintains the frontal layer in the same way that wind-induced vertical mixing maintains sharp thermoclines.

The data suggest that the depth of vertical mixing is different in the warm and cool water masses adjacent to one of the fronts. It is suggested that the change in vertical mixing regimes contributes to the horizontal gradients of properties across this front.
On the Theory of Sunspots
Authors: Alfvén H.
Published: January 2012

It seems not to be generally recognized that the magnetic energy of sunspots is so large that it is unlikely that it can be supplied by the non-uniform rotation of the sun.
Magneto-hydrodynamic Waves in the Ionosphere and their Application to Giant Pulsations
Authors: Lehnert B.
Published: January 2012

In magneto-hydrodynamics conservation of energy leads to the adiabatic relation, du = pdϱ/ϱ2, between the internal energy u per unit mass, the pressure p, and the density ϱ. The relation is valid for arbitrary amplitudes in a non-dissipative medium. The Hall current modifies the properties of magneto-hydrodynamic waves in an ionized gas. The compressive modes and the Alfvén mode earlier discussed by van de Hulst are shown to be coupled by means of the Hall current. The dissipation of slightly damped waves is expressed in terms of the effective conductivity σ3 = σ1 + σ32/σ1 earlier introduced by Cowling. The theory is applied to magneto-hydrodynamic oscillations in the layers of the ionosphere. The possible periods of the waves are consistent with the periods of “giant pulsations” which have been observed as a type of perturbation in the earth's magnetic field in the auroral zone. The results indicate that magneto-hydrodynamic waves in the E-, F1-, and F2-layers may explain the existence of giant pulsations as well as the occurrence of rapid vibrations in the terrestrial magnetic field.
Optimum Smoothing of Two-Dimensional Fields
Authors: Thompson Philip Duncan
Published: January 2012

The problem of smoothing out nonsystematic errors in a two-dimensional field of measurements has been studied from the standpoint of finding the type of weighted area average for which the RMS difference between the true field and the weighted average of the field of observations is the least. For fields whose space-autocorrelation functions are invariant with rotation and have a simple and rather typical form, the optimum weighting function is a linear combination of Bessel functions, whose rate of decrease away from the origin depends partially on the so-called “signal-to-noise” ratio, but primarily on the ratio of the scales of the true field and error field. A comparison of optimum averaging with the analyst’s subjective process of smoothing indicates that the former is significantly superior in its ability to distinguish between random small-scale fluctuations and minor synoptic features of only slightly greater scale. Finally, the minimum RMS error of linearly smoothed fields is expressed in terms of the statistical properties of the true fields and the observing system itself.
Direction of Faulting in the Deep-Focus Spanish Earthquake of March 29, 1954
Authors: Hodgson J. H. , Cock J. Irma
Published: January 2012

An earthquake of magnitude 7.1 occurred off the south coast of Spain on March 29, 1954. The earthquake was remarkable in that it had a focal depth of about 650 km; no earthquake with focal depth greater than normal is known to have occurred in this area previously.

Using methods already established but here reviewed, the mechanism at the focus is investigated. The method defines two planes, without determining which is the fault. There are thus two possibilities. Under the first possibility the fault is approximately vertical and strikes north-south. The movement is vertical, such that the eastern side of the fault rises with respect to the western side. Under the second possibility the fault is approximately horizontal, and the movement is also horizontal, the material above the focus moving due east (that is, in the sense of the earth's rotation) with respect to the material below the focus.
Solitary Waves in the One- and Two-Fluid Systems
Authors: Long Robert R.
Published: January 2012

A theoretical discussion is given of the solitary wave. Part I is concerned with the wave on a water surface; Part II considers the solitary wave at the interface of two superimposed liquids of different density, bounded above and below by rigid surfaces.

In Part I higher approximations are obtained for the speed of propagation, and limits to the wave speed are derived from the momentum theorem. The results include a correction to the second approximation of Weinstein.

In Part II the first two approximations to the wave speed are derived. The equations of the second approximation yield limits on the wave amplitude.
Wind Action on a Shallow Sea: Some Generalizations of Ekman’s Theory
Authors: Welander Pierre
Published: January 2012

In 1923 Ekman developed a theory for the sea-level changes produced in a deep sea by the action of a steady wind. In the present paper the theory has been extended to a shallow sea, for which the Ekman “depth of frictional influence” d is comparable to the actual depth h. It is pointed out that the wind-stress divergence may be of the same importance as the wind-stress curl in this case.

The theory is furthermore extended to the transient case. It is demonstrated how the velocity profile and the flow can be expressed in terms of the local time-histories of the wind-stress and the surface slope, and a single integro-differential equation is derived for the sea-level elevation. This equation could possibly be used for prediction of meteorologic tides and storm surges.
Bubble Formation and Modification in the Sea and its Meteorological Significance
Authors: Blanchard D. C. , Woodcock A. H.
Published: January 2012

It is believed that the vast majority of the airborne salt nuclei arise from bursting bubbles at the air—sea water interface. Four natural mechanisms for the production of these bubbles have been studied. These are whitecaps, rain, snow and supersaturation of the surface waters of the sea due to spring warming. The bubble spectra from whitecaps and snowflakes have been measured and semi-quantitative and qualitative observations have been made on the bubble spectrum produced by raindrops. No evidence of bubble production by spring warming has been obtained.

All of the measurements show that a majority of the bubbles are < 200 microns diameter and, in the case of bubbles from snowflakes, < 50 microns. In the vicinity of a breaking wave the bubble production rate is about 30 cm−2 sec−1.

Due to the effects of surface tension in increasing the bubble internal pressure all bubbles < 300 microns will go into solution even at sea water air saturations of 102 percent. Bubbles < 20 microns will go into solution at saturations up to 115 percent! The solution time for small bubbles of about 10 microns is about 10 sec and is not markedly affected by the water saturation percentage.

It is concluded that the effects of the rate of solution of bubbles in sea water can, under some conditions, play a significant role in modifying the initial bubble spectrum. This, in turn, should influence the spectrum of airborne nuclei.
On a Special Aspect of the Condensation Process and its Importance in the Treatment of Cloud Particle Growth
Authors: Rooth C.
Published: January 2012

Available data on the rate of exchange of molecules between liquid water and vapour in contact with it are put in relation to atmospheric condensation and evaporation processes. It is shown that this exchange process excerts a quenching action on the rate of growth of small droplets that should contribute to the formation of a broad size spectrum. Surface films may enhance the effect considerably. Experimental data are needed to decide finally the meteorological significance of the effect.
The Use of Dopaminergic and Stimulant Drugs for the Treatment of Depression
Authors: Howland Robert H.
Published: January 2012

The brain reward system consists of extensive neural pathways that mediate reward behavior such as pleasure and motivation. These pathways may be involved in the development of symptoms such as apathy, anhedonia, and cognitive dysfunction seen in patients with major depression. These pathways are served primarily, although not exclusively, by the chemical neurotransmitter dopamine, which has suggested a therapeutic role for drugs that influence dopamine activity. A small number of clinical trials using various dopaminergic and stimulant drugs for the treatment of major depression and bipolar depression have demonstrated some benefit when combined with standard antidepressant drugs. Based on this work, several ongoing trials are investigating the use of the stimulant drug lisdexamfetamine (Vyvanse®) as an adjunctive treatment for depression.