摘要:

AbstractA detailed analysis of the variability of Australian district rainfall on seasonal time‐scales over the period 1950–1987 is described. This paper, Part I, describes the dominant spatial modes or patterns of variability. The major analysis tool is rotated principal component analysis (RPCA), used in both the S and T modes. Various criteria are examined to determine the number of components to rotate, including conducting trial rotations and comparison of the resulting patterns with the corresponding one‐point correlation maps. The stability of the chosen solutions is examined by repeating the analysis on various subsets of the data.The S‐mode analysis, which groups districts with similar temporal variation, provides a regionalization of the continent into eight coherent and approximately equally sized regions. The results of this analysis closely resemble those obtained from cluster analysis.The T‐mode analysis clusters seasons with similar large‐scale spatial variations (anomaly patterns). The similarity measure used in the T‐mode analysis is the congruence coefficient, rather than the correlation or covariance. The patterns produced by this analysis consist of continental‐scale anomalies, similar in some respects to the unrotated S‐mode patterns, but more amenable to meteorological interpretation. In particular the first pattern, which accounts for approximately 25 per cent of the total variance consists of anomalies of the same sign over the entire continent centred on south‐east Australia.The relationship between the two modes of representation is also explored. Regression equations are developed to express the spatially complex T‐mode patterns in terms of the localized S‐mode patterns, and alternatively, to partition the variance of each of the S‐mode patterns between the T‐mode components. In Part II the temporal variability and the relationship of these patterns to the Southern Oscillation and other large‐scale circu

ISSN:0899-8418    

DOI:10.1002/joc.3370130102

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractSpectrum analysis of 1197 USA air temperature records yields evidence for two peaks with periods 18.8 ± 1.7 and 10.4 ± 0.5 years. Tests by thet‐statistic show that both are significant at confidence levels of 99.9 per cent, and both account for 23 per cent of total variance in the raw data. They are identified as the luni‐solar 18.6‐year Mnand solar cycle Sc10–11‐year signals in climate, induced by the twelfth largest constituent tide acting on the Earth and a variation of 10 to 11 years in the Sun's luminosity of the order of 0.1 per cent. Amplitude and phase of Mnwavetrains are highly non‐stationary with respect to both time and geography; in particular, abrupt 180° phase changes in wave polarity are often observed. Amplitude and phase of the Scwaves are also highly non‐stationary, with those east of the Rocky Mountains out of phase with waves to the west. These results consolidate and greatly extend and clarify earlier studies of Currie based on far le

ISSN:0899-8418    

DOI:10.1002/joc.3370130103

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractPrincipal component analysis with varimax rotation was used to identify major spatial patterns of New South Wales (eastern Australia) district rainfalls in each season. Four spatial patterns of the principal components of rainfall, each dominant in a subregion of the State, were evident. Plots of correlation coefficients between the amplitudes of the spatial patterns and the Southern Oscillation Index (SOI) revealed temporal instability of the relationships. Results show that the relationships have changed dramatically with time and that they have changed differently from region to region. Over the 55 years (1933–1987) for which data were available, in some regions the correlation coefficients changed from being highly significant, to showing no relationship, in others the reverse was the case, and in some very little change occurred. This meant that over time the spatial pattern of relationships for a given season also changed quite dramatically.These findings have profound implications for studies based on assumptions of stationarity of geophysical phenomena and relationships and suggest there are other, as yet unrecognized, phenomena influencing rainfall in the long‐t

ISSN:0899-8418    

DOI:10.1002/joc.3370130104

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe temporal variability of USA snowfall is investigated for the period 1945–1946 through to 1984–1985 using linear trend and principal components analyses. The results of the linear trend analysis indicate that two regions of the USA evidence significant changes in monthly snowfall over the period. These areas include the Great Lakes/upper mid‐west and high plains regions of the USA. In the Great Lakes/upper mid‐west sector, positive linear trends are found in monthly snowfall totals for the mid‐winter months (December, January, February). For the high plains region, positive linear trends are found for the month of December. Principal components analysis (PCA) is used with seasonal snowfall data in order to better understand the spatial and temporal nature of seasonal snowfall variations across the USA. The PCA isolates six spatially coherent regions in which seasonal snowfall varied similarly over the 40‐year period. Only one of these regions, centred on the Great Lakes and upper mid‐west, displays any long‐term change in seasonal snowfall, a positive trend during the period 1945–1946 through to 1984–1985. These results are discussed in the context of man‐induced and natural

ISSN:0899-8418    

DOI:10.1002/joc.3370130105

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe south‐west of Western Australia is characterized by a ‘Mediterranean’ climate with dominantly winter rainfall. It is the only Australian region where the annual rainfall has significantly decreased during the period 1911–1990. Based on daily rainfall records from 70 stations in the area, high intensity rainfall (which is closely related to flooding, soil erosion, and gully formation) does not show a concurrent decrease. Reasons for this unconformable trend include a greater temporal variability of high intensity rainfall and an increase in the frequency of occurrence of rainfall events at high intensities during the summer. This tends to balance out a decrease during the winter months. While it is unwise to assume that there will be similar trends for average rainfall and high intensity rainfall for a given region, evidence from the instrumental records supports, to some extent, the notion that in a CO2‐warmed world, high intensity rainfall could occur more frequently irrespective of local change to average

ISSN:0899-8418    

DOI:10.1002/joc.3370130106

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractDaily rainfall affinity areas are derived for the island of Mallorca using four years of data, and a 96 × 96 intersite correlation matrix. An initial visual impression of the nature of rainfall organization is afforded by the mapping of correlation links between sites. The Serra de Tramontana form a climatological as well as topographic barrier, producing a marked alignment in spatial rainfall occurrence in that part of the island. Elsewhere ‘core’ sites are identified, about which rainfall correlation is high for distances of up to 15 km. These centre on higher elevation locations in the Serra de Llevant and in the central area, and also the Palma and Campos coastal embayments. Use of rotated principal components and cluster analyses applied to the correlation matrices permits the division of the island into seven major rainfall areas. The uplands of the north‐west and east of the island provide clear units in terms of both exposure and altitude, and their general exposure to prevailing rain‐bearing winds appears important, whilst an urban effect due to Palma and clear sea‐breeze convergence effects near the centre of the island are al

ISSN:0899-8418    

DOI:10.1002/joc.3370130107

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0899-8418    

DOI:10.1002/joc.3370130101

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY