摘要:

AbstractMeasurements of the water vapour content of air in the upper troposphere and lower stratosphere are reviewed. They are interpreted to indicate that significant upward movement of air through a pressure level of about 100 mb, by processes of any scale, occurs only in equatorial latitudes, but they leave uncertain the mechanism of the upward transfer. This implies that contaminants emitted into the atmosphere below this level can reach the upper stratosphere only by way of the equatorial tropopause and after passage through precipitating cloud. The minimum hemispheric exchange of mass through this level is about 1017kg per year. The mass balance of several minor atmospheric constituents, naturally or artificially introduced in the surface layers or in the high stratosphere, is shown to be consistent with this minimum mass exchange.

ISSN:0035-9009    

DOI:10.1002/qj.49710644802

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractRecent advances in satellite‐borne microwave radiometry have led to interest in their use for rainfall amount estimation. The potential accuracy of such techniques is investigated in detail, and is estimated to be about ±70% for rainfall rate estimates, even when many wavelengths are used. The effects of the low spatial and temporal resolution of the most recently launched microwave radiometer (on Nimbus 7) are also investigated, using radar‐based computer simulations. The effects are shown to produce r.m.s. errors of ±200, ±310% respectively, yielding a total error of ±370% for independent pr

ISSN:0035-9009    

DOI:10.1002/qj.49710644803

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractAn investigation of the structure of the GATE sub‐cloud layer carried out using turbulence sensors attached to a tethered balloon cable is described. The observations were made at one or two levels up to 400m near the centre of the C‐scale ship array during the final phase of the experiment. The data were used to derive the vertical eddy fluxes of momentum, sensible and latent heat and the spectra and cospectra of the turbulence parameters, all over one‐hour long periods. Surface fluxes were estimated using the bulk aerodynamic formulae.The results were classified according to the convective activity prevailing during each one‐hour period. Marked changes in the vertical flux profiles with increasing convective activity are demonstrated. Spectra and cospectra in conditions of suppressed convection (small cumulus clouds only, no showers) show the increasing importance of larger scale mixing processes as heights increase to about 300m, but above this (near the top of the mixed layer) processes on a smaller scale are found to predominate. On these latter scales there is an upward flux of momentum which is a consequence of rather shallow vertical mixing in a region where wind speed decreases with height: in more disturbed conditions deeper convection, coupled with the reversed vertical gradient of wind, causes an upward momentum transfer on larger

ISSN:0035-9009    

DOI:10.1002/qj.49710644804

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractA two‐dimensional frontogenesis model forced by a barotropic horizontal deformation field has been developed. Turbulent mixing is neglected and the long‐front flow is assumed geostrophic. The horizontal gradients at the surface become infinite after 3–4 days, assuming a deformation rate of 10−5s−1. In reality we expect turbulent mixing to prevent the final collapse to a singularity. The inclination of cross‐front streamlines to isopycnals decreases rapidly below the surface; the horizontal density gradients do not therefore increase rapidly there. However, such flow can effectively increase the horizontal gradients of passive scalars (we consider temperature here) whose isopleths are inclined to the isopycnals. In a typical example the isotherm pattern makes a front appear to be an order of magnitude thinner and to penetrate much deeper than does the isopycnal pattern. The isotherm patterns produced vary markedly with the initial inclination of isopycnals an

ISSN:0035-9009    

DOI:10.1002/qj.49710644805

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractA subsynoptic disturbance, occurring in an outbreak of polar air over northwestern Europe, is studied by using routine observational data. The disturbance showed a characteristic length scale of about 150km, a time scale of 4 hours, caused a surface pressure drop of only 1 mb, but brought up to 20 mm of precipitation in the coastal region of the Netherlands.The observational analysis suggests that the disturbance was a warm‐core system driven by latent heat release and triggered by forced lifting along the coastline, which activated a weak trough filled with potentially unstable ai

ISSN:0035-9009    

DOI:10.1002/qj.49710644806

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractA study of hemispheric data suggests that the splitting of westerly winds by blocking anticyclones is initially due to simple interference between stationary planetary waves with very large amplitudes but normal phases. A simple model is then used to investigate Green's hypothesis that the blocking anticyclone, once formed, can be maintained by baroclinic waves travelling in the split jet. The results are in good agreement with observations, particularly the vertical structure. A resonance seems likely at zonal wavenumber four.

ISSN:0035-9009    

DOI:10.1002/qj.49710644807

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThe dynamics of large‐scale, horizontal roll vortices in the neutral planetary boundary layer are investigated by means of a two‐dimensional numerical model. The rolls are assumed to be two‐dimensional and are calculated explicitly, while small‐scale turbulence is parametrized by a mixing‐length hypothesis. Although buoyancy effects are never negligible in the atmosphere, the assumptions of the turbulence modelling are supported by atmospheric observations of large eddies which are highly elongated in a direction close to that of the geostrophic wind, together with the observed partitioning of turbulence energy between the large eddies and a distinctly smaller scale. The results indicate a strong sensitivity to the roll orientation, and also the presence of a slow variation on the Coriolis

ISSN:0035-9009    

DOI:10.1002/qj.49710644808

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractExperiments have shown that if a supercooled drop is accreted on to a rimer in such a way that it lands on an already frozen smaller droplet then it may develop a protuberance as it freezes, presumably because the heat loss is fairly symmetrical. These protuberances were found in the temperature range –3 to –8°C, and their probability of production reached a maximum at –5 to –6°C of 1 for every 20 drops accreted. The protuberances tended to have a larger aspect ratio and to be longer relative to the drop diameter at lower temperatures. All these effects were found to be independent of speed of collection over the range 1.5 to 3ms−1. Due to the strong parallelism between the conditions required for protuberance production and ice splinter ejection during riming we suggest that the splinters are a result of explosive fragmentation of about 1% of the protuberances formed. This idea is supported by some experiment

ISSN:0035-9009    

DOI:10.1002/qj.49710644809

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49710644811

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49710644801

出版商:John Wiley&Sons, Ltd    

年代:1980

数据来源: WILEY