摘要:

Abstract(a) The movements of the atmosphere are on such a scale as to produce much coherence between the pressures on successive days. Persistence is especially marked in high values of pressure, which usually last for a week or thereabout, and will appear on a graph as surges.(b) Two surgesmdays apart will make a considerable contribution to the computed amplitude of a wave whose period ismdays; and a third surge or hollow at an appropriate time may further increase it. Thus mere coherence produces an appreciable amount of periodicity.(c) The existence of coherence in pressure series makes the ordinary Schuster criterion for “reality” inapplicable. A test suitable for harmonic analysis follows from a previous paper by the author, but one adapted for correlograms is much needed.(d) The amount of periodicity to be expected in a coherent random series may be examined theoretically or experimentally. It does not differ appreciably from that found in actual pressure series. Hence if a wave system appears there is no special ground for expecting the continuation which is necessary as the basis of a weather forecast. During a stretch of 144 days there was no evidence that a periodicity of, say,pdays observed over a stretch of 3pdays had any appreciable tendency to persist over another 3pdays.(e) Surges and hollows also tend to make points of positive or negative symmetry, and experiments with coherent random series produce as much symmetry as we find in actual pressure series. Thus the symmetry that is observed, like the periodicity, is due to ordinary atmospheric conditions; and even when the symmetry is strongly marked continuity cannot be relied upon to justify predict

ISSN:0035-9009    

DOI:10.1002/qj.49707231402

出版商:John Wiley&Sons, Ltd    

年代:1946

数据来源: WILEY

摘要:

AbstractIt is suggested that a reason for the association between anticyclonic vorticity and subsidence lies in the divergence produced by the frictional forces when a strong horizontal wind shear is present. In particular the region just to the south of a strong westerly upper wind (northern latitudes) is favourable for subsidence.A case in which such conditions remained steady for five days has been examined quantitatively, and it is found that a subsidence velocity of a few centimetres per second is accounted for by assuming an isentropic turbulent interchange coefficient (K) of 5 × 109cms2/sec. This is the value found by Rossby and independently by Grimminger in investigation of other phenomena on a similar scale.The frictional divergence depends on the third space derivative of velocity across the current, and so can only be obtained when the velocity field is mapped in very exact detail. Scope for practical application of this theory in synoptic work is therefore limited

ISSN:0035-9009    

DOI:10.1002/qj.49707231403

出版商:John Wiley&Sons, Ltd    

年代:1946

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49707231404

出版商:John Wiley&Sons, Ltd    

年代:1946

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49707231405

出版商:John Wiley&Sons, Ltd    

年代:1946

数据来源: WILEY

摘要:

AbstractRegeneration of shallow secondaries, stationary near Cyprus for some time, is brought about by the approach of a stream of polar air from eastern Europe, or Asia Minor. The process is quite marked and common, and represents the main mechanism underlying the development of deep depressions in the eastern Mediterranean in winter.Successive cold fronts become traceable on the charts, and shallow thundery depressions, which travel with the general circulation round the main barometric minimum, sometimes develop in the polar air over Egypt; but the system of isobars and fronts is not Norwegian, and while the low can be regarded as orographic in origin, the associated weather is generally analogous to squall phenomena rather than to the development of a depression, and can be treated on the lines suggested by Margules.These regenerated lows are usually accompanied by the occurence of a strong south‐east current over Iraq. This phenomenon has, however, been regarded as a topographical effect; the current being mainly induced to flow parallel to the general run of the plateau of Iran under the effect of convergence into the Cyprus Iows.The present work also endeavours to show that the known seasonal features of the Mediterranean, which are associated directly with the southward extension from summer to winter of the zone of barometric depressions and accompanying westerly winds over the Atlantic and Europe, and with the formation in summer of the great continental low of Asia, are also influenced, at least in the eastern areas, by the Sudan low in the transitional seasons, and by the Siberian anticyclone in winte

ISSN:0035-9009    

DOI:10.1002/qj.49707231406

出版商:John Wiley&Sons, Ltd    

年代:1946

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49707231407

出版商:John Wiley&Sons, Ltd    

年代:1946

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49707231408

出版商:John Wiley&Sons, Ltd    

年代:1946

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49707231409

出版商:John Wiley&Sons, Ltd    

年代:1946

数据来源: WILEY

摘要:

AbstractThis note discusses the theoretical aspects of the errors in measuring curvature due(a)to taking streamlines as trajectories(b)to taking isobars as streamlines(c)to combining these errors by taking isobars as trajectories.It is shown that, in addition to a scale factor error associated with movement of the isobaric and streamline systems (this has already been noted by other writers), there are errors associated with(i)The difluence of the isobars and streamlines(ii)The rate of distortion of the systems(iii)The angle between isobar and wind.By choosing the right place in the isobar and streamline fields some or all of these errors may be avoided. Otherwise any one of them may be significant.

ISSN:0035-9009    

DOI:10.1002/qj.49707231410

出版商:John Wiley&Sons, Ltd    

年代:1946

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49707231411

出版商:John Wiley&Sons, Ltd    

年代:1946

数据来源: WILEY