摘要:

AbstractIn this companion to Part I (Wright, 1988a) of the study on low latitude influences on Victorian rainfall, northern Victorian winter rainfall variability is shown to be dominated by ‘interacting’ (I) fronts, and both parameters are then related to atmospheric circulation anomalies in the Australian region and the Southern Oscillation. The major circulation features accompanying extreme wet and dry winter months in northern Victoria are identified from composited sea level pressure, 500 h Pa height, and 200 h Pa wind fields. Wet winters are characterized by a vigorous subtropical westerly circulation at middle and upper tropospheric levels, a relatively weak subtropical high pressure belt over Australia, and above normal amplitude of the climatological mean long‐wave trough in western Australian longitudes. The intensity and frequency of I frontal systems influencing southeastern Australia is shown to be strongly related to these features, and to cloudiness over the tropical Indian Ocean northwest of Australia, a major source‐region for cloudbands involved in the interactions.In turn, above normal trough amplitude and cloudiness, a weak subtropical high pressure belt, and frequent and relatively well‐developed interactions, are all shown to be characteristic of winters in which the Tahiti‐Darwin Southern Oscillation Index (SOI) is positive. Anomalies tend to be in the opposite sense during negative SOI winters, which feature infrequent, generally poorly developed, interactions, and much lighter rainfall. The dual association of these circulation and cloudiness features with both the SOI and northern Victorian rainfall strongly suggests that I fronts provide the well‐known link between the SOI and northern Victorian rainfall. The current results are discussed in relation to results from other recent studies on synoptic associations with anomalous

ISSN:0196-1748    

DOI:10.1002/joc.3370080602

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractUsing data since 1882 the relationship between summer rainfall over South Africa and the ENSO phenomenon is investigated. A strong association between Warm Events and dry spells, and between Cold Events and wet spells is discussed. The temporal and spatial variability in the relationship is presented. Rainfall during December and March correlates significantly with the previous winter's SOI but rainfall during the mid‐summer months, January and February, shows much weaker correlation. A significant relationship is detected between the summer rainfall and mean monthly geopotentials as well as the 850–500 hPa thermal wind over the central parts of South Africa. Distinctions are made between the dominant rain‐producing systems with regard to these parameters. During January and February, when the SO/rainfall relationship is fairly weak, rainfall develops in a predominantly quasi‐barotropic circulation. On the other hand, during December and March the most significant SO/rainfall correlation coincides with a shift to baroclinic systems. Analysis suggests that a clear signal of the SO can be observed in the phase and amplitude of summertime synoptic‐scale baroclinic systems over the South Afric

ISSN:0196-1748    

DOI:10.1002/joc.3370080603

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractTurkish radiosonde data obtained at the meteorological stations in Istanbul, Ankara, and Izmir have been analysed in order to study the winds between 850 hPa and 300 hPa pressure levels between 1970 and 1984. The monthly mean values of both the zonal (ū) and the meridional (v̄) wind velocity components, their variances, σ2uand σ2v, and the monthly mean values of wind direction, α, were statistically determined. The constancy,Q, of the winds was then computed by taking the ratio of the monthly mean resultant wind speed (V̄t) and the monthly mean scalar wind speed (V̄s). The results were interpreted by taking local wind patterns into conside

ISSN:0196-1748    

DOI:10.1002/joc.3370080604

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe probability distributions of the number of freezing periods per year, their timing and severity are examined at 25 stations in southern and central Florida. The proposed distributions, derived from stochastic crossing theory, provide adequate fits with the exception of three variables at different stations. The estimated parameter values reflect the changing geography of the freeze hazard. The freeze variable that exhibits the greatest variability over the area appears to be the number of periods, while the average severity of freezes and their timings are fairly homogeneous. The theoretical basis of the method permits estimation of the distribution of the dates of first and last freezes and the distribution of the coldest temperature likely to be encountered during any period of interest. The risks of periods of extremely cold temperatures, rarely observed in the historic records, may also be obtained from those at the more commonly encountered level. The technique provides a thorough yet easily interpreted summary of cold‐spell risks at any locatio

ISSN:0196-1748    

DOI:10.1002/joc.3370080605

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThis part of the study expands the modelling of incident solar radiation on Mount Kenya and its glaciers to include the behaviour for sloping as compared to horizontal surfaces. It is concluded that for the purposes of the ongoing climate study the broad‐scale generalizations reached in part 1 of the study for horizontal reference surfaces remain inviolate for sloping reference surfaces. However, significant additional information is brought out by reference to sloping surfaces. Further, differences in absolute radiation magnitudes are significant for realistic situations of cloudiness and shading when modelling short‐term (e.g. monthly) radiation means. In the annual case, these differences are small for glaciers having mean gradients up to 45°; for the one extremely steep glacier with mean slope approaching 60°, these differences are significant. It is anticipated that for higher latitudes the discrepancies between sloping and horizontal reference surfaces in the annual case may well be more substantial. For Mount Kenya, located as it is almost directly under the Equator, it must be concluded that the conventional horizontal reference surface is indeed appropriate for climatic heat and mass budget ana

ISSN:0196-1748    

DOI:10.1002/joc.3370080606

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370080607

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370080601

出版商:John Wiley&Sons, Ltd.    

年代:1988

数据来源: WILEY