摘要:

AbstractZonal means of radiance originating in the stratosphere and measured by the Selective Chopper Radiometer are given for the period November 1970 to November 1971. Results are presented as latitude‐time sections and as monthly means. Equatorial cooling of several degrees was found to be associated with a major warming in the Northern Hemisphere. In the lower stratosphere the annual variation of temperature near the South Pole was approximately twice that near the North Pole, but in the upper stratosphere the variations were almost equal. At the Equator a semi‐annual oscillation of 2.5 K amplitude was present near the stratopause, while there was an annual oscillation of 1.7 K near the tropopause. Global mean temperatures exhibited little variation but the annual component for the upper stratosphere was consistent with the variation of solar heating. The upper stratosphere of the Southern Hemisphere had a pole warmer than midlatitudes during most of the winter, unlike the Northern Hemisphere winter. Height‐latitude sections of retrieved temperature are given for days representative of each s

ISSN:0035-9009    

DOI:10.1002/qj.49710042602

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractBaroclinic instability is examined in an idealized model of the winter stratopause. The upper stratosphere is more stably stratified than the lower mesosphere, and instability can occur when the zonal flow has westerly shear., Using representative parameter values, a maximum doubling time of 2 days is found for a disturbance with zonal wavelength 4000 km and vertical scale 10 km, moving with a velocity within 2ms−1of that of the zonal wind at the stratopause. Newtonian cooling reduces growth‐rates by some 80% of the damping rate, and becomes important for relaxation times of less than 7 d

ISSN:0035-9009    

DOI:10.1002/qj.49710042603

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe formation of small disturbances in cold air outbreaks over the north‐east Atlantic is shown to be due to baroclinic instability. A case study of two such disturbances shows their growth rate, wavelength and phase speed to be very close to the predictions of the baroclinic theory. Surface friction is shown to have a very important effect; strong surface winds enhancing the friction and severely reducing the growth rate. Heating from the sea surface also reduces the growth rate. It is concluded that these lows will develop only when the surface winds are light and where the air flow is not parallel to sea‐surface isotherms, thus explaining their rarity compared to that of cold air outbreaks and providing more discriminating criteria for forecasting their developm

ISSN:0035-9009    

DOI:10.1002/qj.49710042604

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractIntegrations of the shallow water equations on the sphere using the finite element method are performed and compared with published integrations of Doronet al.(1974). Better results are obtained with the finite element method than with a second order finite difference method using four times the number of grid points, in particular the breakdown of a Rossby wave of zonal wavenumber 8 is correctly predicted.

ISSN:0035-9009    

DOI:10.1002/qj.49710042605

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractFollowing a brief discussion of early radiation measurements and the interpretation of the effects of volcanic eruptions in the light of current knowledge of the stratosphere, recent radiation data from USSR, Japan, USA and Australia are examined. Whilst the effects of the Agung eruption are clearly seen on a global scale, the analysis yields no convincing evidence for a recent world‐wide increase in atmospheric turbidity. The need for extreme measurement accuracy is emphasized in the context of long‐term atmospheric monitor

ISSN:0035-9009    

DOI:10.1002/qj.49710042606

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractDuring July 1971, an intensive experimental programme was undertaken in south‐eastern Alberta to measure the turbulence statistics in the planetary boundary layer (PBL), using a 92‐m tower, an array of four smaller towers and an instrumented T‐33 aircraft from the National Aeronautical Establishment of the National Research Council, Ottawa.In this first paper is reported the measurement of the translation velocity of convective plumes, determined by means of an array of towers, at a height of 3.5 m. The direction of plume motion was found to be close to that of the surface wind. The speed of plume motion was found to be close to the wind speed near the top of the surface shear zone; this result is different from previous estimates using different techniques. A dynamic model of the plume was used to show that a translation speed close to the wind speed near the top of the surface shear zone (as observed) allows plumes to exist at a lower thermal instability level than any other possible translation speed.These results mean that Taylor's frozen field hypothesis is not applicable to plume scales since the plumes (although not the air inside them) move at a speed independent of h

ISSN:0035-9009    

DOI:10.1002/qj.49710042607

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe three‐dimensional pattern of Richardson numbers in isentropic co‐ordinates is investigated for a case study of a mid‐tropospheric baroclinic zone for which special three‐hourly radiosonde data are available. Results show that the lowest Richardson number values are found within the baroclinic zone with most values between 0.25 and 1.0.An equation developed by Roach (1970) was used to relate observed versus computed changes ofd/dt(InRi) in isentropic co‐ordinates throughout the baroclinic zone. In general stretching deformation contributed to an increase of InRiin downstream regions of the baroclinic zone whereas the converse was true for shearing deformation in mid‐ and upstream regions of the baroclinic zone. Overall agreement between computed and observed changes ranged from poor outside the baroclinic zone to fair to good within the zone.Air parcels entering the upstream region of the baroclinic zone underwent both frontogenesis and decrease in InRi. The reverse was noted in the downstream region of the baro

ISSN:0035-9009    

DOI:10.1002/qj.49710042608

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractA method is presented for generating a turbulent, three‐dimensional flow field with correct mean flows, Reynolds' stresses, and energies, along with boundary layer structure. The details of the simulation of turbulent plane Poiseuille flow are given as an example. Plane Poiseuille flow was chosen because it is a useful model for many applications, and has available reliable and extensive measurements. All nine of the components of the spectral matrix are included, from actual measurements, along with incompressibility, a sheared mean flow, and measured boundary‐layer structure of the turbulence. The results appear to be realistic, and the statistical structure imposed is adequate for a variety of turbulence studies of three‐dimensional flows, in particular turbulent dispersion. Compared with finite‐difference methods for solving the dynamic flow equations, with comparable resolution, the method presented here requires some two orders of magnitude less storage, and some four orders of magnitude less comput

ISSN:0035-9009    

DOI:10.1002/qj.49710042609

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractAn extensive set of measurements of turbulent fluxes of sensible heat, water vapour and momentum together with mean profiles of temperature, water vapour and wind speed at a ‘non‐ideal’ agricultural site in southern Sweden have been analysed in terms of the Monin‐Obukhov similarity theory. The fluxes of sensible heat,H, and water vapour,E, have been determined with the eddy correlation method, the accuracy ofH+ELvbeingc. Φ 12% according to comparison with net radiation minus ground heat flux. The momentum flux has been determined from low level wind measurements, with a stability dependent ‘skin friction method’.During stationary conditions with winds from ‘undisturbed’ directions (extensive forest areas more than 3 km distant) and unstable stratification, the data for dimensionless wind and temperature gradients, Φmand ϕh, respectively, are well described by the expressions put forward by Busingeret al.(1971), with von Kàrmàn's constant,k= 0.35. The corresponding dimensionless water vapour gradient, Φe, is shown also to follow similarity during these conditions (although exhibiting larger scatter than the two other plots), coinciding with Φhfor strong instability but approaching Φm= 1.35 Φh, at neutrality.For stable stratification the dimensionless profiles do not follow similarity in this study, nor do cases with winds from a 700 m distant forest nor non‐stationary cases, as might be expected.A combined energy balance and gradient approach is shown to give good results not only for the ‘ideal’, unstable case but also for non‐stationary conditions and for conditions with winds from the ‘disturbed’ direction. With temperature and humidity differences measured between 0.5 and 1.14 m above ground and with Φe/Φh= 1.35 there is no systematic difference between measured and calculated fluxes, the accuracy in an individual calculated flux being better than 20%. For the stable case it is shown that the flux of sensible heat can be determined with good accuracy with the flux‐gradient method, using data from the 0.5 ‐ 1.14 m layer. The water vapour flux is obtained with good accuracy as a resi

ISSN:0035-9009    

DOI:10.1002/qj.49710042610

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractIce was grown by accretion on rotating embryos at air temperatures of −6, −12 and −24°C while the liquid water content ranged approximately between 1 and 4 g m−3. The air speed in the wind tunnel and the modal droplet diameter were, respectively, 20 m s−1and 13 μm. Details of the structure of the spongy ice were studied in thin sections after elimination of internal liquid water by centrifuging. Sponginess occurred in radial zones associated with surface protuberances but did not necessarily coincide with the indentations between them. Radial striations and tangential microlayers of some 200 μm thickness were found and point to a complex original ice‐water interface. About half of the spongy specimens were allowed to freeze undisturbed. The subsequent transparent ice contained patches of air bubbles mostly of some 20 μm in diameter showing distinctive arrangements and a log‐normal size distribution. Crystals were elongated in the growth direction while optic axes tended to lie normal to it, 67° being the average value of the angle between the projection of thec‐axis on the plane of the hailstone section and the growth direction. This tendency confirms epitaxial growth during the late

ISSN:0035-9009    

DOI:10.1002/qj.49710042611

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY