摘要:

AbstractThe annual and semiannual waves in zonal mean temperature in the mesosphere are analysed using data from the Nimbus 6 pressure modulator radiometer (PMR). The observation that the annual temperature cycle in the extratropical upper mesosphere has almost exactly opposite phase to the solar cycle and explains over 90% of the total variance suggests that the mechanism which maintains the temperature structure is very closely linked with the annual solar cycle. The occurrence of a peak in the semiannual oscillation around 64° latitude in the southern hemisphere contrasts with an amplitude maximum nearer to the pole in the northern hemisphere, reflecting the different characteristics of sudden warmings between the hemispheres which are the cause of this wave. In the upper mesosphere the semiannual wave has similar phase at all latitudes. This gives rise to a pronounced semiannual wave in the global mean temperature of the upper mesosphere

ISSN:0035-9009    

DOI:10.1002/qj.49710544502

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractObservations of atmospheric flow over a change in surface roughness are reported. Both wind speed and turbulence characteristics were measured. Although the observation site departed from the ideal assumed in roughness change models, it was found that the predictions of ‘second‐order closure’ models are consistent with the observed

ISSN:0035-9009    

DOI:10.1002/qj.49710544503

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractIt is suggested that the polar low is basically a thermal instability phenomenon much akin to a small tropical cyclone. A quasi‐geostrophic model is employed in order to find small‐scale unstable CISK‐forced disturbances in a barotropic basic flow with a vertical structure similar to that actually observed during a polar air outbreak. Case studies of some polar low developments in some ways support a convective hypothesis according to which the polar low is driven by latent heat released in convection c

ISSN:0035-9009    

DOI:10.1002/qj.49710544504

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractAn analytic solution, inpcoordinates, of the dynamical equations of a mature hurricane system is used to determine thepdependence of eddy viscosity coefficients for an assumed quasi‐stationary and axisymmetric phase. The solution is based on: (i) eddy viscosity coefficientsK1andK2, describing respectively horizontal and vertical transfers of momentum, expressed as general functions ofp; and (ii) the premise that the radial variation of the magnitudes of the tangential and radial components of velocity are of similar form. This leads to an integral equation for the tangential velocity. Explicit expressions forK1andK2are finally obtained by choosing power law forms, in thepvariable, which lead to good agreement of the tangential velocity solution with observed distributions. By using this (inverse) method of calculatingK1andK2, the whole eddy system, ranging from eddies created by the very strong velocity shear close to the sea surface to those connected with violent cloud convection, is described by continuous mathematical functions. The associated temperature and condensation heating distributions are then calculated from the hydrostatic relation and the thermodynamic equation. To complete the model an integral water vapour flux condition relates the sea surface temperature to prescribed humidity conditions at the outer boundary of the mode

ISSN:0035-9009    

DOI:10.1002/qj.49710544505

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractA 5‐level global model is described in which finite element methods are used to describe the variations of fields in the horizontal. Three versions of the model are used: two use velocity components as dependent variables but differ in horizontal resolution; the third uses stream function and velocity potential. The results show that the finite element models are competitive with existing finite difference models but proper comparison is difficult because of the large effect of certain special features of the models, for instance the treatment of the poles. The change in dependent variable has a much greater impact on the results than a change in resolution with no change in formulatio

ISSN:0035-9009    

DOI:10.1002/qj.49710544506

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe diffuse irradiance of slopes relative to the diffuse irradiance of a horizontal surface is calculated by integrating the mean radiance distributions of cloudless skies in Britain for a wide range of solar elevations, azimuths and slope angles. There is reasonable agreement with measurements reported from a number of stations; discrepancies are probably due to errors in measurements and to the influence of aerosol on the radiance distributions. A simple model of the diffuse irradiance of slopes, which takes account of circumsolar radiation, is proposed, and agrees well with integrated values of irradiance.

ISSN:0035-9009    

DOI:10.1002/qj.49710544507

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThis paper describes a high resolution radiative transfer scheme which calculates infrared fluxes and heating rates in a cloudy atmosphere. It is intended as a research tool for use in studies of the role of radiation in the physics of fog and layer cloud. The spectrum is split into five bands and allowance is made for molecular absorption by the water vapour 6.3 μm band and the rotation band beyond 20 μm, the 15 μm carbon dioxide band, the 9.6 μm ozone band, and the continuum absorption by water vapour in the 10 μm atmospheric window. The strong absorption by cloud water droplets is calculated directly from the droplet size distribution function. The scheme has been run with a model stratocumulus cloud included, using data based on tethered balloon observations at Cardington. A large cooling rate of 8.7 K per hour is shown to exist at the cloud

ISSN:0035-9009    

DOI:10.1002/qj.49710544508

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractA one‐dimensional cloud model with a variable radius has been developed. The model is capable of being tuned to give internal cloud properties (such as liquid water content) that are in reasonable agreement with field observations. Unlike many other one‐dimensional cloud models, the cloud base rises only slowly over the lifetime of the cloud. The model is compared with two other types of one‐dimensional model: a steady‐state model and an Eulerian time‐depend

ISSN:0035-9009    

DOI:10.1002/qj.49710544509

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractA non‐hydrostatic mesoscale model formulated by Tapp and White has been extended to include the effects of orography and the variation of the large‐scale meteorological situation. Other changes to the model, particularly in the parametrization of boundary layer turbulence, are described and its application as a forecasting tool is illustrated by an extensive study of one situat

ISSN:0035-9009    

DOI:10.1002/qj.49710544510

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractA classification of satellite cloud vortices compiled for the southern hemisphere by Streten and Troup is used to provide an inventory of the incidence of various stages in the life‐cycle of depressions as a function of latitude. These figures are then allied with estimated meridional transient eddy fluxes of both heat and momentum to assess the varying effectiveness of the systems during their life‐cycles as mechanisms of meridional transport, in comparison with the net contribution from other transient systems (travelling long waves and temporal variations in stationary waves). The developing stage of the cloud vortex is shown to be associated with a strong poleward heat flux, decreasing with the age of the system, with only a small (poleward) contribution from other transient mechanisms. For momentum, the developing stage is associated with a moderate poleward flux and the mature stage with relatively little net flux, while strong equatorward transport occurs during the decaying stage. A major poleward momentum flux is attributed to other transient mechanisms, particularly in the upper troposphere. The results are consistent with the hypothesis that the occurrence at preferred latitudes of different stages in the life‐cycle of systems is a major factor controlling the latitude profile of meridional transient eddy flux. A postulated meridional eddy flux distribution within a frame of influence for a mid‐latitude disturbance during its life‐cycle, when related to the broad‐scale zonal current, can account for salient features in the observed global distribution of meridional eddy fluxes of both heat and momentum. An indirect toroidal circulation is inferred when such a system interacts with the mean zonal current, and other synoptic implications ar

ISSN:0035-9009    

DOI:10.1002/qj.49710544511

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY