bluuebunny/crossref_metadata_2025_split huggingface dataset:
A synoptic climatological analysis of rainfall variability in south‐eastern Australia
Authors: Whetton P. H. 
Published: February 2007

AbstractMonthly rainfall data for the state of Victoria in south‐eastern Australia were analyzed using principal component analysis and Varimax orthogonal rotation, with the intention of revealing typical patterns of rainfall variability. Two data sets were used: a spatially detailed set for 1970–1980, and a less spatially detailed set for 1905–1980. The first five rotated principal component patterns (RPCPs) produced from the two data sets showed the same structure. These five RPCPs each dominated rainfall over a particular sub‐region of the study region, and the climatic regionalization that this suggested appeared to be one strongly determined by topography.The anomalies of Australian region mean monthly mean sea‐level (MSL) pressure associated with these five RPCPs of rainfall were determined using correlational techniques. Of the five main RPCPs of rainfall, the pattern based in the south‐west of the state showed the strongest relationship with monthly pressure anomalies, and was associated with the occurrence of onshore westerly winds. The results for the rainfall pattern based in northern Victoria were perhaps the most interesting. Rainfall in this region was related to the occurrence of anomalous northerly winds through southeastern Australia, although through the cooler months of the year these winds accompanied a low pressure anomaly centred over central Australia, whereas in the warmer months they were associated with a high pressure anomaly centred to the south‐east of the continent. This northern rainfall pattern also showed some month to month persistence, and a distinct correlation with the Southern Oscillation.
Use of cross correlations in the search for teleconnections
Authors: Katz Richard W. 
Published: February 2007

AbstractThe search for teleconnections usually involves the calculation of sample cross correlation functions for pairs of atmospheric/oceanic time series. Properties of the theoretical cross correlation function are derived by means of analytical techniques, and properties of the sample cross correlation function are obtained by means of simulations. In particular, the effect of autocorrelation of the individual time series is to ‘smear out’ any contemporaneous cross correlation that might be present, producing nonzero cross correlations at nonzero lags. To combat this problem, the advantages of ‘prewhitening’ before computing cross correlations are demonstrated. Moreover, the operation of smoothing individual time series has the effect of inflating the values of the cross correlation coefficients at nonzero lags. Finally, the behaviour of running cross correlation coefficients is somewhat counterintuitive, making this technique potentially very misleading for detecting changes in relationships over time. For illustrative purposes, these calculations are also performed for Darwin and Tahiti time series of monthly sea level pressure.
Periodic 18.6‐year and cyclic 10 to 11 year signals in northeastern United States precipitation data
Authors: Currie Robert G. , O'Brien Douglas P. 
Published: February 2007

AbstractEvidence for a narrow band‐limited signal with period near 18.6‐years is found in 126 out of 136 yearly total precipitation records, and in 1531 out of 1668 monthly records in the northeastern United States. From 1840 to near the end of the 19th century, rainfall minima in the wavetrain are highly correlated with tidal maxima of the 18.6‐year luni‐solar tide, the twelfth largest tidal constituent in Newton's theory; the wavetrain then switched phase by 180° and for most of the 20th century rainfall maxima are correlated with tidal maxima at 1917.5, 1936.1, 1954.7, and 1973.3. This bistable phenomenon of atmospheric science was discovered by Currie (1983) in a study of tree‐rings from the Patagonian Andes, and O'Brien and Currie (1988) have suggested a dynamical explanation in terms of mathematical physics. In terms of yearly rainfall, the mean percentage amplitude modulation of the wave was near ±6% until 1940 after which it began to increase rapidly, reaching ±10% in the 1960s and 1970s. These results provide a rational explanation for the severe water shortage crisis that occurred at tidal minimum 1964.0 (Namias, 1966; 1967), and reoccurred 19 years later. In addition, a smaller band‐limited term with period 10 to 11‐years is found in a little more than half of the records.
The onset of the southwest monsoon over Kerala: 1901–1980
Authors: Ananthakrishnan R. , Soman M. K. 
Published: February 2007

AbstractUtilising daily mean rainfall from dense rain gauge networks, the dates of onset of the southwest monsoon over south and north Kerala have been derived on the basis of objective criteria for the years 1901 to 1980. These dates have been compared with the onset dates as per records of the India Meteorological Department. Statistics of the onset dates are presented. The mean onset date for south Kerala is found to be 30 May and for north Kerala 1 June with a standard deviation of about 9 days in both cases. The sharp increase in rainfall that heralds the onset of the monsoon is highlighted by superposed epoch analysis. The prevailing notion that rainfall from pre‐monsoon thunderstorms progressively increases and merges with the monsoon rainfall is shown to be not valid.
Comparison of satellite and surface cloud cover observations and cloud cover regions over Europe
Authors: Róth Renata 
Published: February 2007

AbstractA five year data set of satellite cloud cover observations and a thirty year data set of surface cloud cover observations were compared over Europe. There is good agreement between the general characteristics of these two cloud climatologies. Differences between monthly means (January, April, July and October) of the two data sets were formed in 5° × 5° grid cells. These differences, regarding all grid points and months are less than half of one tenth of sky cover in 46 per cent of all cases.The defining parameters (a and b) of the Beta distribution were calculated also for the months of January, April, July and October representing the four seasons. On the basis of a and b values, different cloud cover regions were determined over Europe and these were characterized by averaged curves of the Beta probability density functions. These regions correspond well to distinct areas of geographical environments, as well as to the regimes of the general circulation. Thus, the character of cloud conditions within these regions can be expressed in a numerical way by means of a and b parameters.
Principal component analysis of precipitation in the Adriatic‐Pannonian area of Yugoslavia
Authors: Pandžić Krešo 
Published: February 2007

AbstractUsing the principal component method, some characteristics of the precipitation pattern are established for an area from the Adriatic Sea to the Pannonian lowland (territory of Croatia). The data of monthly precipitation amounts for the 20‐year period (1961–1980) from 108 meteorological stations are used. The first four principal components (PCs), which describe 79‐4 per cent of the total precipitation field variance, are considered. It is shown, graphically and numerically, that the first PC is related to the frequency of cyclones on van Beber's paths IVb, Vb and Vc, the second one is related to their frequency on the paths Vd, Vd1 and Ve, the third to the anticyclonic and non‐gradient weather type and the fourth one is related to the frequency of cold fronts crossing Yugoslavian territory. Using the loadings of the PCs, four homogeneous precipitation sectors are determined and compared to those obtained by Koppen's scheme. Finally, some details of the annual pattern of precipitation for these sectors are discussed.
Potential wind erosion in Australia: A continental perspective
Authors: Kalma J. D. , Speight J. G. , Wasson R. J. 
Published: February 2007

AbstractSeasonal and annual patterns of potential wind erosion in Australia are mapped. Potential erosion is estimated by applying Fryberger's sand drift potential concept to 3 p.m. wind data from 732 stations. Contour maps for January, April, July and October show monthly total drift potential, resultant drift potential, and drift directionality. Stream line maps show resultant drift direction. Annual resultant drift potential and drift direction are also mapped.Monthly total drift potential is maximal in October and minimal in April. Highest values occur on the coast, in the Nullarbor Plain, and in Tasmania; lowest values are scattered across the northern inland. Monthly resultant drift potential is similarly distributed. Monthly drift directionality is higher in the north.Monthly drift direction stream lines mainly express the general circulation of the atmosphere. Some local disturbances occur over ranges; others have cyclonic form. Annual resultant drift potential stream lines are broadly confluent and have anticyclonic curvature.These maps of potential wind erosion, linked to measures of erodibility, provide a basis for studying wind erosion hazard in Australia.
Daily rainfall over Northern Australia: Deviations from the world pattern
Authors: Jackson I. J. 
Published: February 2007

AbstractIn an earlier paper examining relationships between monthly rainfall, raindays and mean daily rainfall intensity in the tropics, two Australian stations showed a consistent pattern of deviations from the worldwide regression equations. Using data from some 50 stations, this present paper demonstrates that this pattern applies generally over northern Australia. Rainfall is much more concentrated, with fewer raindays and higher mean daily intensities, than would be predicted from monthly totals and the worldwide tropical regressions. This marked concentration will have varied implications for hydrology, soil erosion and agriculture. The importance of tropical cyclones and other closed low pressure systems over northern Australia provides a reasonable explanation of the deviations, with support from some other tropical regions. However, a simple distinction between tropical cyclonic and non‐cyclonic areas is inadequate to explain patterns on a worldwide basis.
Relationship of the Indian monsoon rainfall to the northern hemispheric 700 MB height tendency
Authors: Mooley D. A. , Paolino D. A. 
Published: February 2007

AbstractIn this study, the fields of northern hemispheric 700 mb height tendency from January to April and from March to April are examined for the period 1950–1984 in relation to Indian monsoon (June to September) rainfall. The height tendency from January to April at three locations (near Pacific high and near Siberian high at sea level, and over southwest U.S.A) and from March to April at one location (about 50° of longitude west of sea level Aleutian low) are found to be significantly related to the Indian monsoon rainfall. These four variables are generally not inter‐related amongst themselves, and are not significantly related to the April 500 mb ridge, the tendency of the Southern Oscillation Index (SOI), and the eastern equatorial Pacific sea surface temperature tendency from DJF to MAM season.The best amongst the height tendency variables is the height tendency from January to April near sea level Pacific high. This variable is not as good as the tendency of SOI; however, when used in conjunction with April 500 mb ridge and the tendency of SOI, it makes a highly significant contribution to the explained variance and improves the forecasts for independent years as judged by different measures of assessment. This height tendency thus makes a useful additional predictor for the Indian monsoon rainfall.The mechanism of the influence of the development of the Pacific high on the Indian monsoon rainfall is not clear. It is, however, possible that the linkage between the development of the Pacific high and the Indian monsoon rainfall is through linkage of the Pacific high with the development of the summer season trough of low pressure over the Indian sub‐continent. This, however, needs to be investigated.
On the reality of climatic changes in wind over the Pacific
Authors: Wright P. B. 
Published: February 2007

AbstractIt is important to be aware of systematic errors when using data from ship observations to infer climatic changes. The development of our understanding of systematic errors in sea and air temperatures and cloudiness is reviewed. Many reasons for suspecting similar errors in wind data are noted. Wind data for the tropical Pacific for 1920–1979 are then analysed. Trends to stronger trade winds in both the north and south Pacific, and also large anomalies in the winds in these areas during the Second World War, are found in the data. Quantitative comparisons are made with the associated pressure gradients, and qualitative comparisons with rainfall at Pacific island stations. These series provide no support for the suggestion that the wind changes were real.
Arctic cloudiness in spring from satellite imagery: Some comments
Authors: Curry Judith A. 
Published: February 2007

AbstractThe April cloud amounts recently presented by Barry et al. (1987) were significantly larger than expected. It was suggested that this discrepancy was caused by the obscuration of surface features by Arctic haze, which is believed by Barry et al. to consist of pollution aerosol transported from middle latitudes. The present note suggests that a significant portion of the surface obscuration that occurs in April is due to small ice crystals that form in the lower troposphere of high latitudes before the summer warming begins. These ice crystals appear to be a major feature of the Arctic heat regime, and should be included in cloud statistics.
Weather types at Brisbane, Queensland: An example of the use of principal components and cluster analysis
Authors: Stone Roger C. 
Published: February 2007

AbstractPrincipal components analysis was conducted on 15 years data of surface weather observations at Brisbane, Queensland. Component scores from each year's analysis were grouped using an hierarchical clustering method. Each of the 10,920 observations used in the study was able to be placed into a distinctive class so that the weather in Brisbane from 1967 to 1981 may now be described in terms of nine broad weather complexes, or weather yatypes’, and 63 hybrid types at a finer level of refinement. The nine broad weather types uniquely describe variation in Brisbane's climate during the period studied and hint at an ability to identify important variations in controlling mechanisms—in this case the subtropical ridge.
The influence of general circulation patterns on humid and dry years in the cuyo andean region of argentina
Authors: Minetti Juan L. , Sierra Eduardo M. 
Published: February 2007

AbstractDue to the population growth in the agricultural areas under irrigation in Cuyo (West Central Argentina), the consequences of fluctuations in cordillerean river regimes, whose snowfalls provide water for irrigation, have begun to be felt acutely in recent years.Hemispheric and regional circulation patterns associated with two extreme hydrological (drought and excess) situations in Cuyo were investigated, searching for links between both scales.Important anomalies of hemispheric and regional occurrences have been observed when droughts and floods occur at the regional scale (upper level of the mountain range central Andes and Chilean Mediterranean zone).Precipitation fluctuations show a direct or inverse association with other South American Regions (Uruguay and Islas Orcadas del Sur) and also an important teleconnection between phenomena of extratropical latitudes.The anomalous monthly average pressure fields (regional scale) are generated by an increase (20 to 30 per cent over the normal frequency) of a few persistent synoptic models, and by a westerly wave with ridge or trough over Islas Orcadas del Sur (South Orkneys Is.) or towards the west of Juan Fernández.
Global‐scale sea‐surface temperature anomalies and rainfall characteristics in northern Nigeria
Authors: Adedoyin J. A. 
Published: February 2007

AbstractComposite rainfall data over the 35‐year period 1951–1985 from seven Nigerian synoptic stations, all around latitude 12°N, have been used to examine the correlation, or otherwise, between global‐scale sea‐surface temperature (SST) anomalies and rainfall characteristics on the fringe of the Sahel. Results show that SST anomalies of the Indian, North Atlantic and South Atlantic Oceans are correlated with total rainfall and number of rain days while the anomalies of the tropical East Pacific may have influence on rainfall intensity at the beginning of the rainy season. It is indicated that Pacific El Niño events may affect the frequency of occurrence of the main rain‐producing mechanism in the Sahel; namely, squall lines. Extraordinary warmings in the South Atlantic are also shown to cause considerable shortfalls in expected mean monthly distribution of rainfall, especially in August, the main rainy month in the Sahel.
The spatial and temporal patterns of the East African seasonal rainfall derived from principal component analysis
Authors: Ogallo L. J. 
Published: February 2007

AbstractIn this study, rotated principal component analysis (RPCA) was used to study the spatial and temporal characteristics of seasonal rainfall over East Africa during the period 1922–1983. The RPCA solutions were derived from both spatial and temporal correlation matrices. The spatial correlation matrices described intercorrelation between pairs of stations, while the temporal matrices gave correlations between pairs of map patterns.Results obtained with the spatial correlation matrices indicated seasonal shifts in the patterns of the dominant RPCA modes which closely resembled the seasonal migration patterns of the rainfall belts induced by the Inter Tropical Convergence Zone (ITCZ). The influence of the large water bodies, especially Lake Victoria and the Indian Ocean, were however, outstanding throughout the year. Twenty‐six homogeneous regional groups were delineated from the spatial characteristics of the dominant eigenvectors.Solutions based on the temporal correlation matrices clustered together some of the wet and dry episodes. Some of the map patterns clustered together could be associated significantly with the El‐Niño/Southern Oscillation events.
The dust storms of Mexico City
Authors: Jauregui Ernesto 
Published: February 2007

AbstractDust storms represent an important environmental problem affecting the comfort and health of one of the largest urban agglomerations in the tropical world. Data for dust events of varied intensities have been used in order to describe the seasonal and annual variation of dust storms in Mexico City.The maximum frequency of dust events occurs in March at the end of a three‐month period characterized by monthly rainfall amounts of about 13 mm.The frequency of intense (visibility less than 1 km) dust storms has markedly declined (to 0.6 year−1 for the period 1981–1987), apparently as a result of repasturing of Lake Texcoco's dry bed. However, dust activity of low magnitude as observed from Tacubaya has considerably increased in the Mexico Basin, apparently as a result of both accelerated deforestation and urbanization as well as a decrease in precipitation in recent years at the dust source. In spite of the low frequency of intense/moderate dust events, dustfall deposition rates observed near the dust sources are comparable to those measured elsewhere in arid environments.
Summer snowfalls over the mount Olympus area
Authors: Sahsamanoglou H. S. 
Published: February 2007

AbstractThe present paper is a study of summer snowfalls over the Mount Olympus range (altitude > 2500 m) in northern Greece. This occurs about three times every summer and is, of course, linked to the atmospheric circulation over Europe. At least two days before snowfall, a deep trough, reaching almost to the northern end of the western Mediterranean, causes a strong southward invasion of cold air. This cold air‐mass movement results in cyclogenesis near northern Italy. A depression is formed which moves to the east, causing bad weather over northern Greece and a snowfall over the higher part of Mount Olympus. The freezing of air masses over the mountain area is so strong that the dry‐bulb freezing level found at 640 hPa two days before snowfall, reaches 710 hPa immediately after snowfall.
Diurnally varying regional climatic simulations
Authors: Hunt B. G. , Gordon H. B. 
Published: February 2007

AbstractA detailed analysis has been made of the atmospheric variability at a number of specific geographical points as simulated with a global general circulation model. The objective of this study was to assess the model's performance as regards diurnal and interdiurnal variability, but more importantly to identify critical features which should be monitored in climatic‐change experiments. Since the model contains a number of physical processes, including cloud forecasting, three independent rain‐producing mechanisms, a very responsive surface‐hydrology formulation, sea‐ice determination, etc., complex interactions among the various climatic components can occur. Results are presented for a number of longitudinal points at three selected latitudes, representative of summer, winter, and tropical conditions. One of the clearest features of the model output was the very marked longitudinal asymmetry in atmospheric forcing arising from land‐sea contrast. The vital role of the soil moisture, which depends critically on its model formulation, in determining whether this forcing is due to latent or sensible heating over the land is also demonstrated.The unique diurnal variations which were simulated at individual geographical points suggest that systematic distortions must occur in most near‐surface processes in non‐diurnal models. The extreme sensitivity of the convective mechanisms and the consequent impact on rainfall is noted, together with its implications for experiments involving climatic change. Finally, the interdiurnal variability of the model is illustrated by a number of examples, one of which highlights the potential misrepresentation of air‐sea exchanges in models employing fixed sea‐surface temperatures.
Sahel drought: Meteorological or agricultural?
Authors: Agnew C. T. 
Published: February 2007

AbstractMeteorological definitions of drought are deemed to reveal little of the effects of water deficiencies upon the inhabitants of arid regions. An agricultural definition of drought is obtained using a water‐balance model of the moisture available to millet (Pennisetum typhoides).The model accepts inputs of rainfall, potential evapotranspiration, and crop development for 5‐day periods. Values for field capacity, wilting point, bulk density, crop coefficients, and rooting depth are obtained, and changes in soil moisture, actual evapotranspiration, and drainage are computed. The resulting seasonal millet moisture deficits are mapped for ‘millet drought’ in Niger from 1967 to 1978. These maps indicate that for traditional areas of millet cultivation, ‘millet drought’ was a rare event during the 1970s, but was common and widespread in the more northerly, marginal lands.