摘要:

AbstractIt is shown that for all inviscid, adiabatic, quasi‐geostrophic motions in a Boussinesq liquid or in a compressible atmosphere, subject to the usual boundary conditions, the integral over the fluid of the northward eddy flux of potential vorticity vanishes, provided a generalized interpretation of potential vorticity is adopted near rigid horizontal boundaries. For an infinitesimal disturbance in a normal mode to a general zonal flow, the presence of a critical layer within the fluid excludes the existence of stable modes, except in exceptional circumstances. A stable, or slowly growing mode, is associated with a down‐gradient flux of potential vorticity near the critical layer, which does not vanish as the growth rate tends to zero, and can only be balanced by the general growth in the disturba

ISSN:0035-9009    

DOI:10.1002/qj.49709239302

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractThe stability is discussed of an infinitesimal quasi‐geostrophic perturbation to a baroclinic zonal wind which is independent of latitude, in terms of a two‐layer inviscid model with parallel but sloping upper and lower boundaries, so that the northwards gradient of potential vorticity in each layer is equal and opposite, but not a simple multiple of the difference between the basic eastward velocities. A long wavelength cut‐off to the instability is possible, as well as a short wavelength cut‐off. The mechanism for the instability is described qualitatively in terms of the balance between east‐west advection of perturbation potential vorticity, and generation by north‐south motions in the basic gradient, and the reasons for both cut‐offs are clarified. The short wavelength stable modes are described as advected Rossby waves in either the upper or the lower layer.This qualitative description is then extended to apply to the short wavelength cut‐off found by Eady, and to the short wavelength Eady modes, which are always de‐stabilized by a small gradient of potential vorticity in the interior of the fluid, together with the action of

ISSN:0035-9009    

DOI:10.1002/qj.49709239303

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractVertical profiles of the total precipitation in the area scanned by a radar have been obtained for the first time. Profiles in shower situations show that precipitation commonly accumulates at an upper level. In the more severe storms the accumulations persist for an hour or more, descending slowly during this time. There is evidence that the storms dissipate quickly with a marked increase in severity as the accumulation reaches the melting level.Observations have shown that the height at which the accumulation forms steadily increases with the available energy of convection. Theoretical work by East (1957) and Kessler (1961) predicts an accumulation at a height that increases with the updraught speed. A combination of these two approaches has led to relations among the three quantities: energy of convection, updraught speed and height of accumulation. The value of these relations in the analysis of convective storms is demonstrated by using them to interpret the behaviour of a particular severe storm.

ISSN:0035-9009    

DOI:10.1002/qj.49709239304

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractAn analysis of the small‐scale fluctuations in the vertical distribution of ozone calculated from Umkehr observations at Brisbane (27°.5S, 153°.0E) and Aspendale (38°.0S, 145°.1E) shows that these fluctuations extend up to about 30 km in late summer and early autumn and only up to about 24 km in late winter and early spring. Ozone content in the troposphere and lower stratosphere increases with increasing total ozone.Mean meridional distributions of ozone with height have been constructed for the Southern Hemisphere for summer and spring and the results are discussed in relation to the idea of meridional poleward and downward flow of air from the upper part of the tropical troposphere and lower stratosphere. It appears that the changes in the spring amounts of ozone from year to year take place essentially in the 24 to 36 km layer in the middle latitudes of the Southern Hemisphere. Also, above about 25 km, the ozone amount is smaller at 65°S with greater amounts on either side of it. To explain this a transport mechanism above 25 km, consistent with isentropes above that level, is sug

ISSN:0035-9009    

DOI:10.1002/qj.49709239305

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractFronts are considered as aspects of development and it is shown that their characteristics can be deduced without recourse to the traditional concept of air masses. The approach interprets the current practice of synoptic analysis in terms of dynamical theory and, as a corollary, affords the possibility of utilising automatic computational methods for the objective depiction of frontal zones and their associated weather.

ISSN:0035-9009    

DOI:10.1002/qj.49709239306

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractCharacteristics of a large number of hailstones which have fallen in the Pretoria‐Johannesburg area in the past five years have been summarized under the following headings: size distributions, shapes, growth centres, layers and internal structures.Most hailstorms did not produce large hailstones. Only 4 per cent of over 5,000 hail reports were of stones exceeding 3 cm diameter. With increase in size of the largest hailstones, broader size spectra tended to occur and the modal size of hailstones reported as being most common increased. Spheroidal shapes were encountered more often than others in practically all size groups but their relative frequency diminished with size. A high proportion of the hailstones had opaque growth centres. An investigation of layering revealed that many hailstones have more changes of opacity than of crystal structure. Two, three and four crystal layers were often found in medium, large and extra‐large stones. A simple up‐and‐down trajectory can account for the structure of many stones. Slushy ice may form on large hailstones but it is not an essential growt

ISSN:0035-9009    

DOI:10.1002/qj.49709239307

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractVertical exchange coefficients for aerosol material,KA, were determined from measurements of atmospheric turbidity at λ = 0.5 μ following the motion of air flowing over Cincinnati, Ohio. Values of the coefficient for sensible heat,KH, were also obtained at the same time in some instances. Most of the values ofKAwere in the range 0.1 × 105to 10 × 105cm2sec−1with a marked seasonal variation of the average values. No significant variation ofKAwith height (100 to 600 m) was

ISSN:0035-9009    

DOI:10.1002/qj.49709239308

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractVelocity fluctuations in the flight path direction were measured by a single hot‐wire mounted in the wing tip of a light aircraft. Magnetic tape recordings were later analysed by standard means to produce one‐dimensional spectra. These spectra exhibited the (– 5/3) power law behaviour over a range of several decades of wavenumber. Local isotropy was verified in the horizontal plane by flight paths into and perpendicular to the mean

ISSN:0035-9009    

DOI:10.1002/qj.49709239309

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractAn account is given of a numerical experiment in extended period forecasting using analogues selected on the basis of similarity of sequences of daily weather types. The resulting forecasts of weather sequences are significantly better than chance for between 5 and 10 days. This result is probably largely due to persistence.

ISSN:0035-9009    

DOI:10.1002/qj.49709239310

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractMeasurements have been made of the maximum separationXat which charge is transferred by means of a discharge process between two rigid spheres of radiirandRlocated in a uniform external electric fieldE. The experimental relationships betweenX, E, randRare in good agreement with the calculations of Davis (1964). It was observed that for small separations charge transfer occurs even in the presence of weak external fields because the local field between the near surfaces of the spheres is greater than the external field strength by an amount that increases rapidly as their separation decreases.

ISSN:0035-9009    

DOI:10.1002/qj.49709239311

出版商:John Wiley&Sons, Ltd    

年代:1966

数据来源: WILEY