Showing papers in "Tellus A in 1964"

Stable isotopes in precipitation

Abstract: In chapter 2 the isotopic fractionation of water in some simple condensation-evaporation processes are considered quantitatively on the basis of the fractionation factors given in section 1.2. The condensation temperature is an important parameter, which has got some glaciological applications. The temperature effect (the δ's decreasing with temperature) together with varying evaporation and exchange appear in the “amount effect” as high δ's in sparse rain. The relative deuterium-oxygen-18 fractionation is not quite simple. If the relative deviations from the standard water (S.M.O.W.) are called δ D and δ 18 , the best linear approximation is δ D = 8 δ 18 . Chapter 3 gives some qualitative considerations on non-equilibrium (fast) processes. Kinetic effects have heavy bearings upon the effective fractionation factors. Such effects have only been demonstrated clearly in evaporation processes, but may also influence condensation processes. The quantity d = δ D −8 δ 18 is used as an index for non-equilibrium conditions. The stable isotope data from the world wide I.A.E.A.-W.M.O. precipitation survey are discussed in chapter 4. The unweighted mean annual composition of rain at tropical island stations fits the line δ D = 4.6 δ 18 indicating a first stage equilibrium condensation from vapour evaporated in a non-equilibrium process. Regional characteristics appear in the weighted means. The Northern hemisphere continental stations, except African and Near East, fit the line δ D = 8.0 δ 18 + 10 as far as the weighted means are concerned (δ D = 8.1 δ 18 + 11 for the unweighted) corresponding to an equilibrium Rayleigh condensation from vapour, evaporated in a non-equilibrium process from S.M.O.W. The departure from equilibrium vapour seems even higher in the rest of the investigated part of the world. At most stations the δ D and varies linearily with δ 18 with a slope close to 8, only at two stations higher than 8, at several lower than 8 (mainly connected with relatively dry climates). Considerable variations in the isotopic composition of monthly precipitation occur at most stations. At low latitudes the amount effect accounts for the variations, whereas seasonal variation at high latitudes is ascribed to the temperature effect. Tokyo is an example of a mid latitude station influenced by both effects. Some possible hydrological applications are outlined in chapter 5. DOI: 10.1111/j.2153-3490.1964.tb00181.x

The parameters of atmospheric turbidity

Abstract: The methods for evaluating the atmospheric turbidity parameters, introduced by the present author in 1929–30, are subjected to a critical examination. A method first suggested by M. Herovanu (1959) is here simplified and expanded, and used for deriving the named parameters in adherence to a procedure described by the present author in a previous paper in this journal (1961). The procedure is applied to the pyrheliometric observations at Potsdam in 1932–36, published by Hoelper (1939) A comparison between the frequency distribution of the coefficient of wave-length dependence α at the high level station Davos and the low level station Potsdam gives results which are discussed in detail. In all the figures of the present paper, where the turbidity coefficients occur, they are multiplied by 10 3 . DOI: 10.1111/j.2153-3490.1964.tb00144.x

The problem of deducing the climate from the governing equations

Abstract: The climate of a system is identified with the set of long-term statistical properties. Methods of deducing the climate from the equations which govern the system are enumerated. These methods are illustrated by choosing a first-order quadratic difference equation in one variable as a governing equation. The equation contains a single parameter. Particular attention is given to the climatic mean of the single variable. Analytic methods yield the climate in some cases where the system varies periodically, but generally fail when the system varies nonperiodically. Numerical integration yields a value of the climatic mean for any individual value of the parameter. Additional analytic reasoning is needed to determine the nature of the climatic mean as a function of the parameter. The progression from steady-state to periodic to nonperiodic behavior, as the parameter increases, is compared to the progression from steady-state to periodic to irregular flow in the rotating-basin experiments, as the rate of rotation increases. DOI: 10.1111/j.2153-3490.1964.tb00136.x

Cloud structure and distributions over the tropical Pacific Ocean

Abstract: During the summer of 1957 photographic cloud reconnaissance was carried out over the tropical Pacific Ocean, in order to observe tropical convection far from land influences, to relate the distribution of convective clouds to synoptic weather patterns and to analyze structure and street orientation of the cumuli. While all results, excepting photographic measurements, are qualitative, the following conclusions were obtained: 1. Areas with enhanced and with suppressed convection largely were determined by the synoptic situation, especially in the high troposphere. 2. Qualitatively, intensity of convection over large areas, say 10 5 km 2 , could be deduced from application of the baroclinic vorticity theorem to high- and low-tropospheric flow. 3. Precipitation virtually was restricted to areas with synoptic build-up of the moist layer. Little, if any, precipitation fell from cumuli outside such zones, although maximum cloud height exceeded 10,000 feet frequently. 4. For the most part, cumuli were aligned in streets. Trade wind clouds were lined up along the wind in the lower moist layer, where wind and shear have the same orientation. Orientation of cloud rows at large angles to the low-level wind also was observed with lesser frequency, mainly when tall clouds extended into a mid-tropospheric layer with marked shear deviating from the wind direction. DOI: 10.1111/j.2153-3490.1964.tb00167.x

Seasonal persistence and recurrence of European blocking during 1958-1960

Abstract: Blocking activity was especially frequent and persistent over Northern Europe during all seasons from late 1958 through 1959 and 1960. Some effects of the blocking on seasonal precipitation are discussed. The initiation and persistent recurrence of the blocking is studied with the help of various mean seasonal charts, particularly those for mid-tropospheric levels. It is suggested that the physical causes of the blocks lie in complex feed-back phenomena between the atmosphere, the North Atlantic sea surface and the Scandinavian Peninsula (particularly its lack of cold-season snow). The latter two factors appear to serve as conservative links in a feed-back chain, thus providing restorative forcing elements on the general circulation over the area. Some precursory signs of such long period blocking are suggested by an analysis of the wintertime meridional flow prevailing between southern Greenland and southern Scandinavia. DOI: 10.1111/j.2153-3490.1964.tb00176.x

An experimental study on atmospheric diffusion

Abstract: A method has been devised by which atmospheric diffusion can be studied over a few kilometres range with rather good precision at only moderate expense. The method which is based on smoke puff photography is especially well suited for thermally stable conditions. It is possible to study the effect of both the low frequency part and the high frequency part of the Lagrangian spectrum of turbulence on the diffusion. More than 100 complete experiments have been performed at two places in Sweden at three different levels of release. The vertical standard deviation of matter is found to be a function of the following stability parameter: ( ∂ θ ∂ z)/u 2 f , where ∂ θ ∂z is the local vertical gradient of potential temperature, and u z f is “the free wind”, that is the wind just above the friction layer. A comprehensive formula, or rather a system of formulae, for the variation of the vertical standard deviation (sampling time about one hour) with distance from the source, stability and height above the ground of the point of release, has been developed. The formulae are believed to have a very general application, the only site parameter being necessary to know is the roughness length, z 0 . The formulae have been successfully tested against results from various tracer experiments described in the literature. The variance of the horizontal distribution of matter for one hour sampling time is found to be the sum of two parts: one which is independent of stability and one which is dependent on stability in much the same way as is the vertical variance. The distribution of matter from a ground level release is described by new formulae. The result is in good agreement with experimental and theoretical evidence in the literature. DOI: 10.1111/j.2153-3490.1964.tb00162.x

An initial value problem in the theory of baroclinic instability

Abstract: A discussion of the initial value problem for the baroclinic 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. DOI: 10.1111/j.2153-3490.1964.tb00137.x

Note on the stability of water stratified by both salt and heat

Abstract: 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. DOI: 10.1111/j.2153-3490.1964.tb00175.x

A diagnostic study of tropospheric diabatic heating and the generation of available potential energy

Abstract: 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 times 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 times 10 −4 kj m −2 sec −1 and the corresponding value for the eddy generation was −9 times 10 −4 kj m −2 sec −1 . DOI: 10.1111/j.2153-3490.1964.tb00174.x

Travelling Planetary Waves

Abstract: The oscillation of longitudinal position of the very long atmospheric waves, of wave-number 1, 2, and 3 has been described by KUBOTA and IIDA (1954), ELIASEN (1958), and others. In this note the motions of these waves are further examined, the data being Fourier zonal harmonics of the 500 mb height at latitudes 40", 50 ", and 60" N for the period October 1, 1951, to March 31, 1952. In the following, the phase-angle represents displacement west of Greenwich, so that it decreases for a progressive, easterly moving wave. DOI: 10.1111/j.2153-3490.1964.tb00166.x

On the energetics of the mean and eddy circulations in the lower stratosphere

Abstract: A hemispheric network of radiosonde stations is used in order to study the energetics of the lower stratosphere during the IGY period July 1957 through June 1958. For a hemispheric polar cap with 30 and 100 mb as top and bottom boundaries the balance equations of zonal and eddy kinetic energy, and zonal and eddy available potential energy are considered in detail. The eddies appear to build up the kinetic energy of the zonal flow at the expense of the eddy kinetic energy during all seasons. The eddies lose also eddy potential energy to the mean zonal distribution, in agreement with the abnormal upslope direction of the eddy heat transport. Thus, no source of energy for the eddy motions appears to be present in situ and the eddies must be forced by the circulation in the adjacent layers, probably by the tropospheric motions. The energy-cycle in the lower stratosphere is in many respects different from the one usually found in the troposphere, where, as is well known, eddy kinetic energy is destroyed by friction and the energy source is found in the creation of zonal available potential energy by radiation and the subsequent baroclinic processes. For the 100-30 mb layer the necessary kinetic energy is supplied by interaction at the top and/or bottom boundaries, while ultimately the energy is destroyed in the form of zonal available potential energy by radiation. DOI: 10.1111/j.2153-3490.1964.tb00169.x

An exact integral of complete spectral equations for unsteady one-dimensional flow

Abstract: Finite-amplitude, one-dimensional, isothermal flow of a perfect gas is considered. When the flow is organized initially as a “linear” sound wave, it is equivalent to the solution of an “advection equation”. The flow that evolves in this way from an initial state is analyzed by means of a Fourier series in space, with time-dependent coefficients. These coefficients can be determined exactly when the initial velocity is a pure sinusoid. The result is such that the Fourier series in space is a Kapteyn series in time. The series is valid up to the time of shock formation. Throughout this interval the lowest harmonics inferred from severely truncated spectral equations are in good agreement with the exact solution. However, the spectral representation becomes very inefficient as the discontinuous state is approached. DOI: 10.1111/j.2153-3490.1964.tb00179.x

Sampling of noctilucent cloud particles

Abstract: Sampling of noctilucent cloud particles by means of sounding rockets has been successfully carried out from northern Sweden in the Summer of 1962 Two successful flights were achieved, one in the presence of noctilucent clouds and one when no such clouds could be visually observed from the ground or from aircraft The collecting surfaces were exposed between the altitudes of approximately 75 and 98 kilometers during ascent only The particle concentration in a vertical column through the noctilucent cloud display is found to be greater than 8 times 10 10 particles per square meter which is at least one thousand times greater than in the case when no clouds were observed The integral size distribution of the cloud particles is of the form N = Ad − p where 3 < p < 4 A significant fraction of the collected cloud particles had a volatile coating prior to collection The particles were analyzed by electron diffraction, neutron activation, and electron beam microprobe techniques Electron-beam microprobe analysis has given evidence for iron particles with high nickel content Calcium films were used as indicators of moisture associated with the collected particles Study of the exposed and unexposed films flown in the sampling experiments has revealed evidence for moisture Laboratory simulation of a ring- or halo-patterns found in the electron microscopic examination of the noctilucent cloud particles has been attempted This was done by impacting ice-coated nickel particles on collecting surfaces similar to those used in the sampling experiment Ring patterns similar to those observed on the rocket sampling surfaces have been produced The primary conclusions are that the cloud particles are probably of extraterrestrial origin and that a significant fraction appears to have been coated with terrestrial ice Plans for future experiments are briefly outlined DOI: 101111/j2153-34901964tb00146x

Low frequency oscillations trapped near the equator

Abstract: Two simple models illustrate the physical mechanism behind the trapping within a narrow band near the equator of low frequency, infinitesimal oscillations for which the motion is independent of longitude. A thin layer of liquid confined between two rotating spherical shells is in the first case homogeneous, in the second case stably stratified. In the equatorial ocean, one such oscillation would have a period of about ten days and be confined between 6° N and 6° S. DOI: 10.1111/j.2153-3490.1964.tb00159.x

Further studies of energy exchange between the zonal flow and the eddies

Abstract: The present study describes the results of calculations of transports of sensible heat and momentum and of exchanges of available potential energy and kinetic energy between the zonal flow and the eddies in the wave number regime. The study is based on five levels of data for the months of April, July, October 1962 and January 1963, while only two levels of data (850 and 500 mb) were available for the months of January 1959 and April, July, October 1961. The heat and momentum transport calculations in the wave number regime show that a very large fraction of the total heat and momentum transport is carried out by the very long waves during winter while a smaller percentage of the total heat and momentum transport is accounted for by these waves during the remaining part of the year. The exchange from zonal to eddy available potential energy shows a marked variation during the year with maxima during the winter and minima during the summer. The spectral distributions are such that we find a maximum for wave numbers 2 or 3 during the winter. This maximum disappears during summer, when we find the maximum at much smaller wave lengths. This energy exchange is positive in all months thus far investigated not only for the total conversion but also for the individual wave numbers. The interchange from eddy to zonal kinetic energy has a different behavior. It differs from the annual variation of the potential energy exchanges in that we find the maximum value during fall. The spectra are very irregular with no clearly defined maxima and minima. This energy exchange is positive for all months investigated so far except for January 1963, but the average values are always much smaller than the average exchanges between the two forms of available potential energy. It is demonstrated that a very large fraction of the total (negative) interchange during January 1963 is accounted for by wave number 3. The results of our calculations are compared with those of other investigators showing fair qualitative agreement. DOI: 10.1111/j.2153-3490.1964.tb00158.x

Further statistics on the exchange of kinetic energy between harmonic components of the atmospheric flow

Abstract: The transfers of kinetic energy between harmonic components of the 500 mb geostrophic flow over the Northern Hemisphere have been measured for an ensemble of daily maps covering a nine-year period, based on a truncation at zonal wave number, n = 15. The results show (1) that, in the mean, all waves ( n = 1–15) transfer their energy to the zonally-averaged motion ( n = 0) and, of more physical significance, the aggregate of all waves in the group n = 2–15 transfer energy to support the asymmetric polar vortex comprised of wave numbers zero and one, and (2) that, among the waves themselves, waves of n = 2 and 5–10 are sources of kinetic energy and all the rest are sinks. The energy source at n = 2 seems to be a significant new result indicating a strong forced conversion of energy on the scale of the major continents and oceans. Seasonal variations are discussed. DOI: 10.1111/j.2153-3490.1964.tb00180.x

The angle of windrows in the ocean

Abstract: Direct observations of the angle of windrows in the ocean with respect to the direction of the wind within a few feet of the surface show that there is a systematic deflection of the row orientation to the right of the wind direction. The average angle of the data is 13 degrees with a standard error of estimate of 2.0 degrees. Observations were obtained from small boats or by measurements from aerial photographs of the angle between the wind and windrows as indicated by smoke flares and material in the water. This systematic angle and earlier measurements of row spacing as a function of wind speed are interpreted as evidence that the Langmuir circulations in the ocean are produced by shear-flow instability in the Ekman boundary layer. DOI: 10.1111/j.2153-3490.1964.tb00173.x

A note on the adjustment towards geostrophic equilibrium in a simple fluid system

Abstract: A simple fluid system is used to study numerically how the atmosphere reaches a geostrophic equilibrium from a non-geostrophic initial state. Most of the previous studies on atmospheric adjustment have emphasized the initial and final states. Furthermore, they have usually considered motions smaller or larger than the radius of deformation . This study explores the adjustment process for scales both greater and smaller than the radius of deformation . The role of gravity-inertial waves in the adjustment process is clearly shown by the numerical results and by an accompanying theoretical discussion. Finally, some speculation of the implications of atmospheric adjustment towards the problem of providing initial data (termed initialization) for primitve equation numerical weather prediction models is discussed. DOI: 10.1111/j.2153-3490.1964.tb00189.x

Auroral morphology, I. The location of the auroral zone

Abstract: An analysis of aurora distribution in the northern and southern hemispheres has been made according to results of photo-observations for aurorae. The auroral zone is of an oval form, approaching the geomagnetic pole (φ ∼ 78°) at day hours and withdrawing from the pole (φ ∼ 68°) at night hours. The location of auroral zones in the northern and southern hemispheres at day and night hours are given. DOI: 10.1111/j.2153-3490.1964.tb00163.x

Electron microscope studies of noctilucent cloud particles

Abstract: Details of the sample preparation and handling techniques of the electron microscope samples for the noctilucent cloud sampling experiment are given. Typical electron micrographs and distribution functions are shown. Most of the noctilucent cloud particles appear to be extraterrestrial in origin. Approximately 10% of the total number of particles collected had a volatile coating which is believed to be ice. DOI: 10.1111/j.2153-3490.1964.tb00148.x

Convective instability in a two-layer fluid heated uniformly from above

Abstract: A fluid in which the dynamic and thermodynamic coefficients (μ, α, χ, c p etc.) vary vertically may become unstable when it is heated uniformly from above, assuming that the basic stratification is gravitationally stable and that the thermal expansion coefficient is positive. This “anti-convection” is studied in the special case of a fluid composed by two semi-infinite layers, each of which has constant coefficients. In the theory the Boussinesq approximation is used for each layer separately, and the interface is assumed to be plane. These assumptions seem justified in the present problem. Instability is favoured when the thermal expansion coefficient and the conductivity are large in one of the layers and small in the other layer. A necessary condition for instability is that the ratio μ 1 α 1 C p2 /μ 2 α 2 C p1 is larger than 9 (or smaller than 1/9), where μ is the dynamic viscosity, α the thermal expansion coefficient, and cp the specific heat per unit mass. When this condition is fulfilled instability will occur for sufficiently large values of the ratio ? 1 /? 2 (small values, respectively), where ? is the thermometric conductivity. The convection cells are confined to a region next to the interface. Small cells have comparable width and height, while larger cells are flattened in proportion to the 1/6 power of the Rayleigh number. Because of counteracting non-linear effects the convective motion cannot grow very large, the vertical velocities can at most be of order ?/ D , where D is the scale of the cell. It is suggested that cells with Rayleigh numbers of order unity dominate the picture in finite amplitude situations. The driving energy comes from a region next to the boundary in the fluid layer having the larger thermal expansion and conductivity. Any motion started in the other layer creates thermal perturbations that are conducted into this region inducing a reversed circulation. When the thermal expansion coefficient is large this reversed circulation becomes strong. Through the frictional coupling it can directly amplify the primary motion and an instability develops. It should be possible to observe the instability in a laboratory experiment. A mercurywater system seems suitable for this purpose. The theoretical analysis shows that instability occurs when heating is applied at temperatures below 18°C. Geophysical and astrophysical applications seem possible. As example, the instability may appear at the interface between the atmosphere and the sea. An air-water system is stable under laboratory conditions, but in nature the existing eddy friction and conduction change the conditions considerably, and such as to favour the occurrence of the instability. DOI: 10.1111/j.2153-3490.1964.tb00171.x

Planetary waves in a symmetrical polar basin

Abstract: The problem of low frequency zonal vorticity waves in a symmetric polar basin is formulated in a plane projection tangent to the sphere at the pole. Eigensolutions are found when only first order curvature effects are retained in the plane of projection. Comparison with the results of Longuet-Higgins (1964b) shows that such an approximation provides a reliable analogue, applicable to the polar regions, of the mid-latitude beta-plane. DOI: 10.1111/j.2153-3490.1964.tb00185.x

Atmospheric stratification revealed by twilight scattering

Abstract: The uses and limitations of the twilight method of detecting aerosol layers are discussed and an experimental modification capable of checking the reliability of the results is described. The data from several sequences of measurements are shown to give average distributions of stratospheric aerosols in good agreement with those determined by direct sampling. The stratification revealed by the experiments is very variable. Simultaneous observations at different latitudes show that the aerosol distributions often have the same form over distances of 300 km, but that the degree of similarity decreases rapidly with increasing separations. There are preferred heights for layers showing intense scattering, which on the average, slope upwards towards the equator. Some features show a surprisingly high degree of persistence in time and some curious changes in apparent height. DOI: 10.1111/j.2153-3490.1964.tb00145.x

Auroral morphology, II. Auroral and geomagnetic disturbances

Abstract: Data from visual observations at middle latitudes give information on the southern boundary of aurora appearance in zenith. Comparison of the aurora zone location with the linear current in the ionosphere and with the magnetic disturbance is made. Current orientation in the ionosphere and the aurora arc direction are considered. DOI: 10.1111/j.2153-3490.1964.tb00164.x

The viscous boundary layer at the free surface of a rotating baroclinic fluid

Abstract: The properties of the viscous boundary layer at the free surface of a rotating baroclinic fluid are analyzed and compared with those of the well-known Ekman boundary layer at a rigid surface. Although the ageostrophic components of the flow in the free surface boundary layer are weaker than in the Ekman layer, there are problems of practical interest in which their effects are not negligible. DOI: 10.1111/j.2153-3490.1964.tb00188.x

The concentration of ammonia and nitrate in rain water over Israel in relation to environmental factors

Abstract: Ammonia in monthly composite rain water samples from seven stations in Israel shows marked dependence of concentration on soil temperature. The mean concentration during the cool winter months is 0.17 e.p.m. NH + 4 , while in spring it rises to at least four times higher. Release of pedogenic ammonia from calcareous soils, which becomes accelerated at the beginning of the warm spring, is considered to be the major source of the ammonia. Losses from fertilization with ammonium containing fertilizers may be a contributing factor. Nitrate concentration is less variable and averages 0.04 e.p.m. NO − 3 during the winter months. Total seasonal washout by rain ranged from about 4 to over 20 kg NH 4 -N per hectare depending on precipitation or on the average 40 g NH4-N per hectare for each mm rain. DOI: 10.1111/j.2153-3490.1964.tb00161.x

The structure of the Ekman layer for geostrophic flows with lateral shear

Abstract: 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. DOI: 10.1111/j.2153-3490.1964.tb00160.x

Composition analysis of particles from noctilucent clouds

Abstract: Composition analysis has been performed on particles collected from noctilucent clouds by a rocket sounding experiment in northern Sweden during August 1962. Electron diffraction, neutron activation, and electron beam microprobe techniques were applied to give information about chemical composition and possible crystal structure of the particles. Results obtained to date are presented in this paper which also discusses the applicability of the above methods to small particle analysis. DOI: 10.1111/j.2153-3490.1964.tb00149.x

Techniques for rocket sampling of noctilucent cloud particles

Abstract: Particle sampling experiments utilizing sounding rockets were conducted in northern Sweden during August of 1962. Two successful flights were achieved, one in the presence of noctilucent clouds and one when no such clouds could be visually observed from the ground or from aircraft. The collecting surfaces were exposed between the altitudes of approximately 75 and 98 kilometers during ascent only. The instrumentation and performance of the rockets is discussed. DOI: 10.1111/j.2153-3490.1964.tb00147.x

An overlooked aspect of the baroclinic stability problem

Abstract: The behavior of small disturbances of a stratified heavy fluid in nonuniform rotation is well known to be a complex subject, even if additional physical complications such as compressibility, non-plane boundaries, and irreversible effects are ignored. But because of its relevance to atmospheric motions, the subject has been studied extensively and a considerable literature exists. All such studies known to the writer have however involved assumptions beyond those of the type mentioned above. DOI: 10.1111/j.2153-3490.1964.tb00165.x