bluuebunny/crossref_metadata_2025_split huggingface dataset:
Principal component analysis of the Lamb Catalogue of Daily Weather Types: Part 2, seasonal frequencies and update to 1987
Authors: Briffa K. R. , Jones P. D. , Kelly P. M. 
Published: February 2007

AbstractPrincipal component analysis is applied to seasonal weather‐type frequencies from the Lamb Catalogue of Daily Weather Types for the British Isles. Four combinations of the major weather types are identified, which represent around 70 per cent of the variance of the data set. Long‐term trends in the seasonal principal component time series are described and relationships with temperature and precipitation are identified.It is shown that a pronounced change in the character of the synoptic circulation over the British Isles has occurred in recent decades. A decline in the frequency of westerly weather types has been compensated for by an increase in the frequency of pure cyclonic and anticyclonic types and, dependent on season, directional types. This development suggests greater variability in the atmospheric circulation and related climatic parameters. The westerly decline has not been as marked in autumn. In this season, though, there has been a notable shift towards greater southerliness at the expense of northerly weather types.
Climatological contingency probabilities of clouds
Authors: Goodman A. H. , Henderson‐Sellers A. , McGuffie K. 
Published: February 2007

AbstractThe ideas surrounding contingency co‐occurrence probabilities of cloud types are discussed with respect to two types of probability: firstly, that given a lower level cloud (L) there is also an upper level cloud (U), P(L ⇒ U), and secondly the probability that given an upper cloud layer there is a lower cloud layer, P(U ⇒ L). Particular emphasis is placed on the fact that analyses to date have considered the frequency of observation of co‐occurrence, not, the potentially more useful, coexistence probability. From four separate months of global surface observations the P(L ⇒ U) was calculated as a function of lower level cloud amount on a global, regional, and individual station basis for (i) stratiform and altiform and (ii) stratiform and cirriform cloud type combinations. Global patterns of P(L ⇒ U) behaviour are somewhat similar to regional patterns produced by previous work and are, on occasions, reproducible on a regional scale and, in some instances, by individual stations. Values of P(L ⇒ U) involving lower level overcasts are required in the calculation of the P(U ⇒ L) term, thus rendering climatological estimates of P(U ⇒ L) susceptible to biasing if an inappropriate value of P(L ⇒ U) for L = overcast is chosen. To demonstrate this effect, monthly global climatologies of P(U ⇒ L) were generated for several combinations of upper and lower cloud types using (i) an assumed mean value for the overcast case and (ii) a modification to the previously assumed overcast P(L ⇒ U) values, as suggested here. Comparison of these climatologies revealed differences, widely spread across the globe, of mostly within ± 10 per cent according to cloud type, but with a few larger changes in excess of 30 per cent.
Climatic classification for queensland using multivariate statistical techniques
Authors: Puvaneswaran Manickam 
Published: February 2007

AbstractAn array of 28 climatic variables for 113 stations in Queensland, Australia, is subjected to factor analysis and cluster analysis. The factor analytical approach elucidated three major factors, a humidity factor, a temperature factor, and a rainfall factor, from the matrix. Spatial variation of factor scores was described and linear equations were compiled using the factor loadings that are significant. By grouping these factor scores with the aid of a distance‐grouping technique, Queensland was classified into three major homogeneous climatic regions. A further 12 subclimatic regions have also been identified. These regions were compared with Koppen's classification scheme.
Drought over Zimbabwe in a regional and global context
Authors: Matarira Caxton H. 
Published: February 2007

AbstractThis study attempts to identify meteorological conditions that lead to dry and wet episodes over Zimbabwe. Correlation analyses are carried out between the Southern Oscillation Index and rainfall over south‐eastern central Africa. The results show significant correlation between the Southern Oscillation (SO) and seasonal rainfall over the region. The results also indicate that the SO signal is stronger over the south‐east of Zimbabwe and along the coastal areas of Mozambique. El NiñTo events seem to be associated with below normal rainfall over Zimbabwe, while cold events, which are the opposite extreme of the SO, are accompanied by above average rainfall.Three‐month seasonal (December–February) deviations of 1000–mbar temperature, surface pressure, and the 500‐mbar geopotential height from the long‐term mean are analysed during wet and drought years. The anomaly pressure gradient force is directed towards the subcontinent during wet periods and towards the ocean area during dry episodes. A similar pattern is observed at the 500‐mbar level.A comparison of wet and dry seasons in relation to the temperature anomaly field points to an association between warmer 1000‐mbar surface temperatures around the African subcontinent and above normal seasonal rainfall. Correlation analysis shows that a high incidence of tropical cyclones in the Mozambique Channel is associated with below normal rainfall over Zimbabwe.
Regionality and periodicity observed in rainfall variations of the baiu season over Japan
Authors: Murata Akihiko 
Published: February 2007

AbstractThe regionality of rainfall variations of the Baiu, a rainy season over Japan, is investigated with special reference to periodicity. Using the Varimax rotated principal component analysis (PCA), Japan is divided into eight regions based on natural‐logarithm‐transformed rainfall data of June. In order to find significant rainfall variations from a sequence of rainfall data in each region, non‐rotated PCA is applied to the rainfall data for each region. Its first component score is defined as the rainfall variation index (RVI). Four regions show statistically significant periodicities of 10, 8, 4, or 2·2 years in rainfall variations. In addition, the rainfall variations reveal a similarity in the general shapes of spectral density for each region. The temporal variations of each periodicity show non‐stationary changes. This feature is especially distinct for periodicities at 4 and 2·2 years. From the results of squared coherence, it is pointed out that these periodicities are closely related to variations of the North Pacific High and the Okhotsk High. In the discussion, the validity of the regional division proposed in the present study is confirmed in comparison with other studies. Seasonal representativity of monthly rainfall variations is also discussed.
Historical evidence for Southern Oscillation‐southern African rainfall relationships
Authors: Lindesay J. A. , Vogel C. H. 
Published: February 2007

AbstractSummer rainfall over the central area of southern Africa is known to be modulated with the phase changes of the Southern Oscillation such that rainfall is above normal during high‐phase (cold event) and below normal during low‐phase (warm event) summers. This relationship holds for the period 1935–1986; the temporal stability of Southern Oscillation–southern African rainfall associations on longer time‐scales has not been tested. A documentary‐derived rainfall chronology has been developed for the southern parts of the summer rainfall area for the 100‐year period 1820–1920, enabling the extension of the rainfall record backward some 60 years before reliable meteorological records are available for the region. Comparison of the documentary series with both early Southern Oscillation chronologies and earliest southern African rainfall records suggests that the nature of the relationship between summer rainfall over the subcontinent and the Southern Oscillation has remained essentially unaltered since at least 1820.
An ice‐cover climatology for lake erie and lake superior for the winter seasons 1897–1898 to 1982–1983
Authors: Assel Aymond A. 
Published: February 2007

AbstractObservations of mid‐lake Great Lakes ice cover are sparse prior to the decade of the 1960s. In an effort to provide an historical perspective of mid‐lake ice cover back to the turn of the century, daily average ice cover for Lakes Erie and Superior over 86 winters (1897–1898 to 1982–1983) was reconstructed using empirical‐statistical ice‐cover models developed in an earlier study. Long term average maximal monthly ice cover occurs in February and is 68 per cent for Lake Erie and 40 per cent for Lake Superior. Mid‐lake ice formation occurs about 1 month earlier on both lakes during severe winters. Average maximal monthly ice cover during severe and during mild winters is 95 per cent and 14 per cent for Lake Erie, 87 per cent and 17 per cent for Lake Superior. Severe winters are associated with lower 700‐mbar heights over the eastern USA compared with mild ice‐cover winters. Analysis of total winter ice cover indicates three ice cover regimes: (i) a high ice‐cover regime from the late 1890s to early 1920s; (ii) a low ice‐cover regime from the early 1920s to late 1950s; and (iii) a high ice‐cover regime from the late 1950s to the early 1980s. Ice‐cover climatologies developed during the 1960s and 1970s are not representative of ice covers in the low ice‐cover regime of the 1920s to late 1950s. Spectral analysis of the reconstructed total winter ice cover suggests interannual variations in ice cycles that correspond with the 2–3‐year interannual variation in atmospheric variables known as the quasi‐biennial oscillation.
Dust storms in the Canadian Prairies
Authors: Wheaton E. E. , Chakravarti A. K. 
Published: February 2007

AbstractAlthough dust storms are quite frequent in the Canadian Prairies, no scientific studies of the nature of dust storms of this area exist, to the authors' knowledge. This work is a preliminary step in depicting temporal and spatial variations of dust storms in the Canadian Prairies. Dust storms occur at least once to as often as five times per year, on average, in the agricultural prairies. This frequency indicates the risk of occurrence of the various impacts of dust storms, such as serious soil erosion. Dust storm frequencies exhibit a pronounced peak in the spring and a weak secondary peak in August. The spatial pattern of dust storms indicates a low risk of occurrence in the northern agricultural prairies and the highest risk in the south central prairies. Knowledge of these patterns in space and time should facilitate the control or avoidance of such impacts of dust storms as wind erosion of soils, crop damage, air pollution, and general environmental degradation. Studies should be carried out to further investigate the relationships of climatic factors with dust storms as well as their linkages with other environmental aspects.
Spatial patterns of drought frequency and duration in the contiguous USA based on multiple drought event definitions
Authors: Soulé Peter T. 
Published: February 2007

AbstractThis study examines patterns of drought frequency and duration in the contiguous USA based on multiple definitions of drought events. Patterns are examined using data from the three Palmer indices: monthly moisture anomaly index (ZINX), drought severity index (PDSI), and hydrologic drought index (PHDI). The data span a 94‐year period and are spatially aggregated to the climatic division level. The stimulus for this study is the lack of systematic examination of the possibility of varying spatial patterns of drought frequency and duration among the drought types represented by these indices.Isoline maps of mean drought frequency indicate that the index used to define a drought has a major impact on the spatial patterns. Patterns identified using the monthly moisture anomaly index are nearly inverse of those for the drought severity and hydrologic drought indices. Patterns of drought duration also vary among the indices, although previous findings of greater drought persistence in the interior regions of the USA were upheld by all three indices. Results also indicate that varying the parameters (intensity, minimum duration) of an index‐specific drought event definition has a minor impact only on the spatial patterns.
Studies of surface energy balance of sloping terrain
Authors: Oliver H. R. 
Published: February 2007

AbstractMeasurements of radiation and soil energy balance components were made for a complete solar season on a south and north facing slope on the edge of the Chilterns, England.The contrasts between the two slopes are illustrated on both the diurnal and seasonal time‐scale. It is shown that a consistent relationship exists between daily solar and net radiation totals for the slopes throughout the year but that soil heat flux cannot be modelled easily. Further, it is shown that it is possible to derive a simple model of solar radiation on to a slope from measurements made on the horizontal.Combining these conclusions points the way towards simple routine calculation of slope radiation balances for use in energy and evaporation models over undulating terrain.
Rainfall characteristics of Mainland Europe's most southerly stations
Authors: Wheeler Dennis , Martin‐Vide Javier 
Published: February 2007

AbstractThe rainfall in the far south of Spain is well represented by the records of Tarifa and Gibraltar, the latter being of unusual length. The complex interplay of locational and climatological elements singles out the region's climate as one of particular interest. Cyclic patterns in the record are examined, revealing evidence of periodicities of different frequencies.
Australian rainfall trends during the twentieth century
Authors: Nicholls Neville , Lavery Beth 
Published: February 2007

AbstractA set of high‐quality rainfall records is used to examine rainfall trends over Australia during the twentieth century. The 191 stations used have been selected by an exhaustive search of documentation regarding instrumentation, observational practices, site relocations, and exposure. Statistical tests of the reliability of observing practices also have been applied in the selection process, as well as tests to detect inhomogeneities. The data set used is the most reliable available for monitoring rainfall trends during the twentieth century. The data have been clustered objectively into groups exhibiting similar variations in annual rainfall. A subset of 10 stations (one for each cluster) suitable for long‐term monitoring of rainfall trends is selected. The trends in annual, winter, and summer rainfall are exhibited. The study confirms trends noted in earlier studies. Summer rainfall over much of eastern Australia increased abruptly around 1950. In the south‐west of the continent most stations recorded a smoother trend to lower winter rainfall, although there is a small area with increased rainfall. The identification of these trends in this study indicates that they are not the result of unreliable observations or to doubtful compositing of stations into groups. These trends have now continued for some decades after their initial observation. It is possible, however, that the twentieth century trends simply reflect a return to conditions of the late nineteenth century, rather than a trend that could be unambiguously attributed to an enhanced ‘greenhouse effect’.
Contrasting meteorological structure of intra‐seasonal wet and dry spells in Zimbabwe
Authors: Matarira Caxton H. , Jury Mark R. 
Published: February 2007

AbstractThe meteorological structure of contrasting wet and dry spells in Zimbabwe, south‐east Africa is studied using European Centre for Medium Range Weather Forecasts composites. Diagnostic examination of composite synoptic‐scale features indicates that lower northerly and upper easterly flow is enhanced during wet spells, corresponding with a tropical low over Zambia and an anticyclone off the south‐east coast of Africa, respectively. Dry spells exhibit an increase in mid‐latitude cyclones off the south‐west coast of Africa and tropical cyclones near Madagascar. Mid‐tropospheric troughs are located over the east and west coasts of Africa near 25°S and serve to increase anticyclonic vorticity over Zimbabwe in dry spells. Specific humidity fields reveal that the maximum shifts southward 5° and eastward 10° in the wet spells. Cyclonic vorticity and low geopotential heights occur on two or three days in the wet spell, coincident with intense cumulus convection and high rain rates. The eddy covariances of zonal wind and specific humidity are dominated by westward (eastward) fluxes in wet (dry) spells; while poleward moisture fluxes contributed by transient eddies are largest over the south Mozambique Channel (south‐east Atlantic) in wet (dry) spells. The eddy fluxes are shifted 15–20° longitude eastward in the wet spells. The relative contribution of thermodynamic and kinematic inputs are evaluated in the mean flows and transient eddies for contrasting wet and dry spells. Much of the difference between wet and dry spells is explained by the mean flow, while the transient flux in the mid‐latitudes assumes a subordinate role.
Spatial and subseasonal patterns of the long‐term trends of Indian summer monsoon rainfall
Authors: Kumar K. Rupa , Pant G. B. , Parthasarathy B. , Sontakke N. A. 
Published: February 2007

AbstractLong‐term changes in the Indian monsoon rainfall on regional and local scales have important social and economic consequences. To present a comprehensive picture of such changes, the monthly rainfall data at 306 stations, well spread over India, have been analysed over 114 years (1871–1984), for long‐term trends. The trends are quantified by linear trend for monthly as well as seasonal rainfall for each station. Some broad contiguous areas showing statistically significant trends have been identified. Areas of increasing trend in the monsoon seasonal rainfall are found along the west coast, north Andhra Pradesh and north‐west India, and those of decreasing trend over east Madhya Pradesh and adjoining areas, north‐east India and parts of Gujarat and Kerala.The subseasonal patterns indicate that the excess or deficiency of the monsoon rainfall is more frequently realized in the later half of the season. Monsoon rainfall tends to be more concentrated in August, over the west coast and central India.
A new daily central England temperature series, 1772–1991
Authors: Parker D. E. , Legg T. P. , Folland C. K. 
Published: February 2007

AbstractIn 1974 Manley produced a time series of monthly average temperatures representative of central England for 1659–1973. The present paper describes how a series of homogenized daily values representative of the same region has been formed. This series starts in 1772, and is consistent with Manley's monthly average values. Between 1772 and 1876 the daily series is based on a sequence of single stations whose variance has been reduced to counter the artificial increase that results from sampling single locations. For subsequent years, the series has been produced from combinations of as few stations as can reliably represent central England in the manner defined by Manley. We have used the daily series to update Manley's published monthly series in a consistent way.We have evaluated recent urban warming influences at the chosen stations by comparison with nearby rural stations, and have corrected the series from 1974 onwards. The corrections do not (yet) exceed 0.1°C.We present all the monthly data from 1974, along with averages and standard deviations for 1961–1990. We also show sequences of daily central England temperature for sample years. All the daily data are available on request.
A coherence between the QBO and the amplitude of the Mauna Loa atmospheric transmission annual cycle
Authors: Dutton Ellsworth G. 
Published: February 2007

AbstractThe transmission of direct solar radiation through the atmosphere above Mauna Loa, Hawaii, is shown to have a quasi‐biennial cyclic component that is coherent with the well‐known tropical stratospheric quasi‐biennial oscillation (QBO). The QBO‐related signal in the 32‐year transmission record is manifested as an oscillation in the amplitude of the annual cycle. The transmission annual cycle is known to be caused by seasonal transport of Asian continental dust to and over the island of Hawaii. Variations in water vapour and ozone are eliminated as possible influences in the transmission‐QBO relationship, leaving aerosols as the source of the oscillation. The ultimate cause for the quasi‐biennial signal in the transmission record is unknown. Small but cyclic modifications to the tropospheric energy budget occur as a result of the transmission variations. The magnitude of the energy budget variations are less than those typically expected to have a significant climatic impact.
Relationship between QBOs of stratospheric winds, ENSO variability and other atmospheric parameters
Authors: Kane R. P. 
Published: February 2007

AbstractThe 50‐mbar tropical zonal wind has a predominent quasi‐biennial oscillation (QBO) mode of an average period of ca. 28 months, with variation in the range 21–33 months and amplitudes varying within ± 20 per cent. For the Southern Oscillation, Tahiti minus Darwin (T‐D), sea‐surface temperature (SST) and equatorial rainfall indices, QBO is not the strongest mode. Periods of 3.6 and ca. 6 years are stronger. The QBO modes for these and other parameters (e.g. surface winds and winds in upper and lower troposphere and stratospheric winter temperature at the North Pole) are very irregular, with amplitudes, phases, and sometimes even period having large changes with time. It seems that these have little relationship with the 50‐mbar zonal wind QBO and may have altogether different origins.
Establishment of a data bank from records of climatic disasters and anomalies in ancient Chinese documents
Authors: Fang Jin‐Qi 
Published: February 2007

AbstractOn the basis of a survey of the existing literature on unique ancient Chinese documents, a data bank of climatic calamities and anomalies during historical times for 68 regions of China has been established in numerical code. The stored climatic disaster and anomaly patterns include flood, drought, plagues of locust, hail, famine, unusually cold and warm spells, and harvests. In addition, records of floods and low water levels of the Yellow River and its major tributaries were stored under a special title. This paper provides an introduction to the data and data bank.
GCM simulation of the Sahel 1984 drought with alternative specifications of observed SST
Authors: Druyan Leonard M. , Hastenrath Stefan 
Published: February 2007

AbstractTwo climate simulations using the NASA/Goddard Institute for Space Studies coarse‐resolution GCM are compared in order to investigate the sensitivity of modelled summer precipitation over West Africa to the specification of observed sea‐surface temperatures (SST). Both experiments used analyses of observed SST for the boreal spring and summer of 1984, but one was derived from NOAA publications while the second came from COADS archives. Values of the NOAA SST for the tropical Atlantic were somewhat higher during June–August, leading to larger modelled evaporation rates and a model hindcast of heavy precipitation over West Africa in August, contrary to observational evidence. By comparison, dry conditions were simulated using COADS SST. The results highlight the importance of quality observations of SST and they demonstrate how sensitive the GCM is to these data.