ISSN:0035-9009    

DOI:10.1002/qj.49710042302

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractSynoptic and meso‐scale precipitation and airflow patterns in the occluding depression which passed over England and Wales on 8‐9 March 1967 are analysed. Large‐scale circulations are illustrated in terms of airflow relative to the synoptic system within the framework of surfaces of constant wet‐bulb potential temperature (θw). Meso‐scale precipitation and airflow configurations are inferred from a sequence of over 120 large‐scale maps of 13‐min precipitation amounts. There was no obvious ‘conveyor belt’ in the occluding depression, but the upward relative flow coincided closely with large rain areas of the warm front and the depression centre. Subsidence at the cold front and within the warm sector inhibited precipitation growth in those parts of the depression.Large (200 times; 50 km) and small (50 times; 50 km) meso‐scale rain areas were found in the depression. The latter resulted from clusters of generator cells, which formed in an area where potential instability was released by large‐scale upward motion. The clusters moved with the winds at about 550 mb. The large meso‐scale rain area lay at a small angle to the surface warm front and lasted for about three hours. Its size, location, and orientation were due to the movements of three small meso‐scale systems within the relative flow at their generator level. The location and intensity of a small meso‐scale rain area on the eastern flanks of the Pennines, together with the associated rainshadow to the west of the upland, were analysed with the aid of a modified lee‐wave equation. Other small meso‐scale precipitation areas were due to airflow over sub‐synoptic deformations in the θwsurfaces. All types fit into a two‐tier scaling of mes

ISSN:0035-9009    

DOI:10.1002/qj.49710042303

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe paper describes a relatively simple model of a non‐precipitating cumulus cloud that grows by the ascent of successive spherical thermals through the residues of their predecessors, mixing with the surroundings being determined by the relative velocity and the radius of the thermal. The model appears to account for several important features of the cloud structure and the droplet‐size spectrum that are not produced in models of a single parcel or plume. In particular, it produces modest clouds in 30‐40 min in which the vertical velocity, cloud depth and liquid‐water content agree quite well with observations. The computed droplet spectra closely resemble measured spectra and reproduce the bimodal structure observed by Warner. In model maritime clouds containing small concentrations of droplets, the spectra broaden quite rapidly and produce droplets ofr= 25 μm by condensation on nuclei ofm= 10−11g in concentrations of order 100 m−3within half an hour, beyond which size they may continue to grow rapidly by coalescence to precipitation size. However, in continental clouds containing droplet concentrations of a higher order, it is difficult to produce a significant number of droplets of even

ISSN:0035-9009    

DOI:10.1002/qj.49710042304

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe existence, statistical significance, and possible causes of stratospheric temperature anomalies observed at the 100 mb level in the Australasian region in 1963 and 1966 are discussed with reference to the so‐called quasi‐biennial oscillation, volcanic dust, and the general circulation. This discussion is facilitated by the use of the observed correlation between stratospheric temperatures and the mean latitude of the surface high pressure belt, in order to increase the sensitivity of a statistical test for anomalous temperatu

ISSN:0035-9009    

DOI:10.1002/qj.49710042305

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractExperiments conducted over a flat uniform ploughed field indicate that the small convective plumes commonly observed in the surface layer travel as an entity with horizontal speeds proportional to the friction velocity,u. This proportionality, in turn, implies a direct relationship between the inferred height of the plume base and roughness length. For these experiments, the height of the plume base averaged 1.2 m.

ISSN:0035-9009    

DOI:10.1002/qj.49710042306

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe turbulent transfer processes near the surface were investigated through time domain statistical analyses of the fluctuations of horizontal and vertical wind and temperature. The joint probability density functions for (w,u) and (w,T) and the probability densities, flux‐angle distributions and fluctuation‐magnitude‐and‐duration distributions forwuandwTwere computed. The results showed that the transfer mechanisms for momentum and heat fluxes were different and these differences increased with instability. The effects of buoyancy are to lead to highly efficient heat transfers but to very inefficient momentum transfers. Forz/L= −0.5 large amounts of momentum are transferred both up and down by large fluctuations inwubut the net transfer is relatively small and usually downward. The heat transfer process, on the other hand, is more uniform in time and the large fluctuations ofwTare just about a

ISSN:0035-9009    

DOI:10.1002/qj.49710042307

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractAn analytic formula is derived which describes approximately the scattering of electromagnetic waves in a haze. This formula is compared, and found to agree well, with the exact results from Mie Theory that is available in the literature. The formula is used to arrive at a simple, non‐redundant but complete parameterization of the aerosol mode

ISSN:0035-9009    

DOI:10.1002/qj.49710042308

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractSome models of steady planetary‐scale disturbances forced in the winter stratosphere by tropospheric pressure perturbations are presented for zonal flows with both vertical and meridional shear. The resulting structure of these disturbances is realistic. In particular, they are confined in the horizontal to regions of strong westerly wind, and do not exhibit a deficient vertical penetration, results in contrast with some earlier studies. Examples are included in which amplitudes are insensitive to the presence of either a strong New tonian cooling or singular‐line absorption.The time‐dependent behaviour of stratospheric planetary waves is examined for a zonal wind with uniform vertical shear. Analytical solutions emphasize the importance of a low‐level conversion of zonal available potential energy in amplifying a disturbance forced at the tropopause. When allowance is made for the meridional structure of the stratospheric jet, a reasonable agreement is obtained between theory and observation, in particular with respect to perturbation geopotential heights observed in sudden w

ISSN:0035-9009    

DOI:10.1002/qj.49710042309

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractFrom ship‐borne radiosonde and radar wind observations during the Atlantic Trade Wind Experiment 1969 (ATEX) the relation between actual and geostrophic wind in the subcloud layer is determined. The frictional force and the divergence of vertical transport of momentum between the sea surface and 500‐m height are computed by the ageostrophic method.Along the surface wind direction, balance between pressure gradient and frictional force is closely established. Perpendicular to the surface wind the expected balance of pressure gradient and Coriolis force is not obtained but a substantial frictional force results from this component.The boundary condition that the stress vanishes at the lowest wind maximum leads to an underestimation of surface stress by about 35 per cent. It is suggested that convective transport of momentum must take place in the subcloud la

ISSN:0035-9009    

DOI:10.1002/qj.49710042310

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49710042311

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY