bluuebunny/crossref_metadata_2025_split huggingface dataset:
A case study of low level country breeze and inversion heights in the Johannesburg area
Authors: Goldreich Yair , Surridge Anthony D. 
Published: February 2007

AbstractPrevious studies within a shallow valley east of the city centre of Johannesburg (South Africa) revealed the presence of some anomalies in the mesoscale, winter, nocturnal climate regime. Among them: the valley was relatively warmer during inversion nights; more than one thermal belt was discerned and valley winds dominated the early hours of the mornings. A tethered balloon and a mobile acoustic sounder were used to monitor temperature, wind and humidity profiles in the valley and vicinity, whilst ground mobile units measured temperature. Observations revealed a three layer wind system in which an elevated country breeze is sandwiched between the katabatic flow near the ground and the gradient wind aloft. The double thermal belts observed on the valley's slopes are probably due to the oscillation of the country breeze (the lower) and the meso‐scale valley inversion top (the upper one). The inversion top over the ridge lines is probably caused by the regional nocturnal inversion or an elevated inversion eroded by the urban heat island plume.
Stratospheric aerosols and sea‐surface temperatures
Authors: Parker D. E. 
Published: February 2007

AbstractSuperposed‐epoch analyses show statistically significant warming and cooling of the East Tropical Pacific Ocean a few seasons after major low‐latitude and high‐latitude volcanic eruptions respectively, confirming the results of Handler (1986a). The statistical significance of the results is confirmed by a Monte Carlo sampling technique which takes account of pre‐eruption changes in the oceanic temperatures, and the results are only slightly sensitive to the selection of eruptions. Occasional sequences of extreme temperatures in the random samples underline the need for numerical modelling studies to complement the statistical investigations.
Low latitude volcanic eruptions and the El Niño‐Southern Oscillation
Authors: Nicholls Neville 
Published: February 2007

AbstractAn apparent association between low latitude volcanic eruptions and the El Niño‐Southern Oscillation (ENSO), has been examined using a superposed epoch composite analysis of Darwin monthly mean pressure, an index of ENSO. Ten eruptions have been included in the analysis. In the composite, the date of eruption tends to be preceded by lower than average pressure at Darwin, and followed by above average pressure. A strong linear upward trend in the composite pressure anomaly starts well before the date of eruptions and continues for several months after the eruption. The analysis suggests that ENSO events are not caused by low latitude volcanic eruptions, since significant anomalies in Darwin pressure, and an upward trend in the anomalies, are observed well before the date of eruption. Low latitude eruptions tend to be preceded by the start of the sequence of events which leads to ENSO.
Development processes for five depression systems within the Polar Basin
Authors: Ledrew Ellsworth F. 
Published: February 2007

AbstractFive synoptic sequences in the Polar Basin are studied on a day by day basis. A diagnostic model is used to illustrate the relative roles of the dynamic properties of the advected air flow in comparison to mechanisms related to the characteristics of the underlying surface. It is found that the properties of the advected air flow are the major contribution to the vertical circulation associated with synoptic evolution and are a necessary condition. Latent heat release may also be a significant mechanism which supports the proposal by others that a CISK type process may contribute to further development in the Arctic. The surface sensible heat flux is not a necessary process and it may at times oppose the vertical circulation when warm air is advected into the region of development within the circulation of the depression. The surface frictional effect is a minor contribution within the central Polar Basin but is a significant process in systems migrating along the Asiatic coastline.A feedback linkage between synoptic evolution and intensification of the baroclinicity is proposed in the Greenland region for a cold low type of vortex. A cold pool, apparently created by intense radiative cooling over Greenland, was identified in early July. There was significant advective convergence associated with the thermal gradients which contributed to synoptic development as the depression migrated around this pool. It appears that the intensification of the potential temperature gradient with the advection maintained the baroclinicity, despite warm air advection into the centre of the pool. This is an interesting feature which requires further study and confirmation.
Changes in precipitation conditions in the western mediterranean over the last century
Authors: Maheras Panagiotis 
Published: February 2007

AbstractA study of precipitation variations over the western Mediterranean is given, for a period of 95 years (1891 to 1985), based on the use of Principal Component Analysis. The curves for the scores are traced and then analyzed for annual as well as seasonal precipitation. Two principal moist periods are found (1901 to 1921 and 1930 to 1941) and two principal dry periods (1922 to 1929 and 1942 to 1954). A comparison of variations in precipitation and zonal indices (ZIa) indicates that with a meridional circulation dominating over the western Mediterranean, we have an increase in precipitation; with a zonal circulation dominating we have a decrease in precipitation.
Variability of mean monthly temperatures and semi‐annual precipitation totals in Europe in relation to hemispheric circulation patterns
Authors: Kozuchowski K. , Marciniak K. 
Published: February 2007

AbstractThe influence of general hemispheric circulation on European temperature and precipitation was investigated. Data from the period 1901–1976 were utilized: the monthly frequencies of occurrence of W, E, C circulation pattern types according to the Wangenheim‐Girs classification, monthly values of pressure differences between 35° an 65°N (zonal index), mean temperatures of January and July at 30 stations in both the warm season (May‐October) and the cold season (November‐April) and semi‐annual precipitation totals for 21 stations in Europe. The correlation coefficients between the circulation characteristics and climate elements indicated above in Europe were calculated.Maps of these correlation coefficients have been produced, with the areas of their statistical significance. The results show that variability of temperature, and also partly of precipitation in Europe are significantly correlated with changes of circulation pattern types. January temperature also depends on the zonal index.If it is assumed that in future, until the end of this century, an increase of W type frequency and a decrease of C circulation pattern types will take place—it may be expected that temperature and precipitation will undergo appropriate changes in certain parts of Europe. Northern and some central areas of Europe are likely to change from continental to oceanic climate as regards temperature; precipitation is likely to increase in northern Europe.
The synoptic climatology of ablation on a New Zealand glacier
Authors: Hay J. E. , Fitzharris B. B. 
Published: February 2007

AbstractLocal scale ablation and energy budget measurements are reported for the Ivory glacier in the Southern Alps of New Zealand over 53 days during two consecutive summer periods. Ablation averaged 38 mm day−1, but varied from less than 10 mm day−1 to over 70 mm day−1. Radiation supplied 52% of the energy for glacier melt, with the convective fluxes contributing most of the remainder. The results are related to large scale synoptic weather patterns over the southwest Pacific region. Different synoptic situations generate distinctive energy budgets, with radiation important during southerly circulation patterns and the convective fluxes relatively more important with northerly circulation patterns. These findings are discussed in the context of the retreat of New Zealand glaciers this century and possible circulation changes.
Storm rainfall on the Njemps flats, baringo district, Kenya
Authors: Rowntree K. M. 
Published: February 2007

AbstractAnnual, seasonal and storm rainfall characteristics are analysed for the Njemps Flats, a semi‐arid area near Lake Baringo in the Kenya Rift Valley. Storm rainfall is analysed in terms of intensity, timing, duration and total storm depth. Storms characteristically occur in the early evening, with one storm of around 2 h making up the daily rainfall totals. High intensity rainfall seldom persists longer than 30 min. The maximum 30 min intensity recorded was 80 mm/h, the maximum 60 min intensity was 75 mm/h. An analysis of annual and monthly recurrence intervals of storm depth indicate that for a 1 in 10 year recurrence interval, June, July and April suffer the heaviest falls, whereas for a 1 in 2 year recurrence interval the months with the heaviest storms become August, July and April. The significance of this to erosion potential and runoff harvesting are discussed.
An index of sea ice variations in the Nordic seas
Authors: Sear C. B. 
Published: February 2007

AbstractTwentieth century sea ice data from the Nordic Seas (the Atlantic Sector of the Arctic) are examined using a simple index of variations in sea ice extent. The index measures overall sea ice extent variations in the Nordic Seas between 1901 and 1977. Variations in the marginal ice zone during the melt season are shown to reflect regional air temperature changes. Reduction of the index data using principal component analysis highlights sub‐regional heterogeneity in melt season sea ice extent variations. An important spatial pattern of variation is one in which sea ice extent in the Barents Sea varies out of phase with that in the central Greenland Sea. This alternating pattern has a quasi‐periodicity of around three years. Time series analyses of other sea ice records indicate significant quasi‐periodicities in the region of between 3 and 4 years and 2.5 years. Three years may be a key time scale of variation in the Atlantic Sector of the Arctic seasonal sea ice zone.
Reginalization of daily rainfall in Kenya by means of common factor analysis
Authors: Bärring Lars 
Published: February 2007

AbstractDaily rainfall data from 73 stations distributed throughout Kenya were subjected to maximum likelihood factor analysis. Data for the period January 1971 to December 1985 were used. A brief analysis of data quality and representativity and the problem of missing data are included. The data were transformed by natural logarithms. Scree and LEV plots together with the Kendall/North criterion for eigenvalue separation indicated break points at 5, 11 and 15 factors. The 11‐factor model was judged as being the most parsimonious, for both statistical and climatological reasons. It explained 38 per cent of the total variance.The general features of the regionalization are found to be reasonably consistent with other studies. The major regions (the coast, the Highlands, the Lake Victoria area, and the dry northern/eastern areas) appear in this regionalization but are divided into several subregions. It can be concluded that this subdivision is partly linked to physiographical regions and orographic influence. In addition, possible links to regional circulation patterns are discussed.
Climatic changes in and around the Rajasthan desert during the 20th century
Authors: Pant G. B. , Hingane L. S. 
Published: February 2007

AbstractRainfall and temperature data during the period 1901–1982 are studied for the northwest Indian region consisting of the meteorological subdivisions of Punjab, Haryana, west Rajasthan, east Rajasthan and west Madhya Pradesh. The results indicate a decreasing trend in the mean annual surface air temperature, which is mainly contributed by the south‐west monsoon season (June through September), The mean annual and south‐west monsoon season rainfall series over most parts of the region indicate a conspicuous increasing trend. The increasing trend is significantly marked for the subdivisions constituting the peripheral areas of the Rajasthan desert. These trends in rainfall and temperature are examined in relation to the changing land use pattern of the region due to extensive irrigation. Earlier findings of Winstanley (1973) reporting a decreasing trend in rainfall are found to be unacceptable due to the unrealistic assumptions of his study.
El Niño and its effect on precipitation in Arizona and Western New Mexico
Authors: Andrade Edward R. , Sellers William D. 
Published: February 2007

AbstractThis paper focuses primarily on the effect of El Niño on seasonal and annual precipitation at 26 locations in Arizona and western New Mexico for an 86‐year period from 1900 to 1985. Following Rasmusson (1984), each year is classified as either a non‐El Niño year (51) or an El Niño year (35), with the El Niños designated as being very weak (4), weak (8), moderate (12), or strong (11). Using the Mann‐Whitney U‐test for the 19 stations in Arizona, we find that, in the spring (March‐May) and in the autumn (September‐November), there is a positive relationship between precipitation in Arizona and both moderate and strong El Niños.These results are verified by correlating seasonal and annual precipitation for the complete 26‐station network with the pressure difference between Tahiti and Darwin. Plausible physical explanations for these results are given.
The low latitude influence on winter rainfall in Victoria, south‐eastern Australia—I. Climatological aspects
Authors: Wright W. J. 
Published: February 2007

AbstractA synoptic mechanism is proposed for a long‐known, but synoptically little‐studied, tropical influence on northern Victorian rainfall during the winter half‐year, based on results from a 12 winter (June‐September) climatology covering the period 1971–82. It is shown that heavy precipitation events in northern Victoria commonly result from ‘interactions’ between cloud masses originating at low latitudes within the Australian region, and high amplitude frontal troughs moving within the midlatitude westerly flow. Most of the precipitation falls ahead of surface cold fronts, within moist northerly airstreams. The low latitude cloud masses involved may originate in several ways, but most commonly take the form of so‐called ‘northwest cloudbands’ originating over the tropical Indian Ocean northwest of Australia.‘Interacting’ frontal systems contribute some 50 per cent of northern Victoria's winter precipitation, but the presence of a relatively modest topographical barrier across the centre of the State substantially reduces their contribution to total rainfall in southern and southeastern Victoria. A distinction is made between these ‘interacting’ (or I) fronts, and ‘non‐interacting’ (NI) fronts: although I fronts occur less frequently than NI fronts, they produce considerably heavier rainfall. Analysis of the moisture content of prefrontal airmasses reveals that the airmasses ahead of I fronts are generally much moister than those ahead of NI fronts, and that the heavier I frontal rainfall is largely attributable to this moisture. An investigation is also made of moisture‐rainfall relationships for cold lows, also a significant source of precipitation throughout Victoria.
Seasonal forecasting of the Kenya coast short rains, 1901–84
Authors: Farmer Graham 
Published: February 2007

AbstractA rainfall anomaly time series for the Short Rains (September to December) on the Kenyan Coast (KCS) is derived for the period 1901–84. On the year‐to‐year time scale a high degree of association can be seen between high/low extremes of a Southern Oscillation Index and negative/positive anomalies in the KCS series.The SOI‐rainfall relationship is investigated seasonally with KCS lagging the SOI series by one, two and three seasons. A decay of the correlation with increasing lag can be seen. When the time series is divided into 1901–42 and 1943–84 the relationships are stronger in the more recent period. Some forecasting skill does seem possible using the June to August (JJA) SOI to predict the September‐December rains. While the 1901–42 period shows a skill not much improved from using a simple climatological forecast, the 1943–84 period shows a much stronger relationship. Possible reasons are discussed for the disparity between the two time periods, also evident in results from others parts of Africa and Asia. There may well have been a change in some underlying climate mechanism between the early decades of this century and the more recent decades.
Seasonal frequency variations in the 40–50 day oscillation
Authors: Gray B. M. 
Published: February 2007

AbstractThe effect of local sea surface temperature changes on frequency shifts in the 40–50 day oscillation is examined using seasonal means. Data were stratified into ENSO (El Niño‐Southern Oscillation) and non‐ENSO years and a significant difference found. In non‐ENSO years, a seasonal shift was noted at some sites. Seasonal frequency means were described qualitatively in terms of sea surface temperatures and changes in zonal circulation cells.
Homogenized long‐period Southern Oscillation indices
Authors: Wright Peter B. 
Published: February 2007

AbstractMany research workers require indices of the Southern Oscillation that are continuous for a long period, homogeneous and easily updated. This paper aims to provide such indices. The method used is to compare indices based on sea‐surface temperature (SST), rainfall and pressure, and thereby to make some corrections to improve homogeneity. To fill data gaps, substitutions are proposed based on regressions between indices over 1950–1979. Tabulations are presented of the recommended long‐period indices: SST monthly 1872–1985; rainfall monthly 1893–1983; and pressure seasonal 1851–1984. The most extreme years according to the two monthly indices are listed.
Advances in the study of sub‐saharan drought
Authors: Druyan Leonard M. 
Published: February 2007

AbstractThe scientific community has responded to the protracted sub‐Saharan drought with a variety of research projects and publications. Related research has dealt with the spatial or temporal analysis of rainfall anomalies, the local or distant atmospheric circulation characteristics that precede or accompany the anomalies, or the influence via teleconnections of remote sea‐surface temperature (SST) anomalies on Sahel precipitation. General circulation models (GCM) have been profitably utilized to test several hypotheses related to sub‐Saharan drought, including the impact of changed albedo, surface roughness, surface evapotranspiration, and SST. This article reviews a selection of the relevant literature and offers an integrated discussion of research results. Conclusions indicate that certain ocean‐atmosphere climate systems combine to deprive the sub‐Sahara of the moisture required for copious monsoon rains during some drought years, while during others, atmospheric dynamics over North Africa limit the number or intensity of the wave disturbances that initiate the moist convection associated with much of that region's summertime rainfall.
The control by atmospheric pressure patterns of sulphate concentrations in precipitation at Eskdalemuir, Scotland
Authors: Farmer G. , Davies T. D. , Barthelmie R. J. , Kelly P. M. , Brimblecombe P. 
Published: February 2007

AbstractIt is shown that, on a monthly basis, certain sea‐level atmospheric pressure patterns can be identified which are conducive to, or mitigate against, high excess sulphate concentrations in precipitation at Eskdalemuir, Scotland. This is not simply a consequence of the amount of precipitation influencing the concentration. The differences in the pressure patterns for months grouped into ‘high’ and ‘low’ excess sulphate concentration reflect the relative importance‐of transport from pollutant source regions and from regions with relatively small source strengths. It is the intensity of the pressure gradients over Europe and the Atlantic, combined with the position of the meridional axis of the Iceland Low/Azores High couplet, which appears to influence the monthly excess sulphate concentration in precipitation. The existence of these relationships on a monthly time‐scale points towards a climatic control on acidic deposition, and introduces the possible role of climatic change.
A study of climatic variability in Nigeria based on the onset, retreat, and length of the rainy season
Authors: Olaniran O. J. , Sumner G. N. 
Published: February 2007

AbstractThe long‐term variability of rainfall conditions in Nigeria in terms of the onset, retreat, and length of the rainy season has been analysed, using pentad data for the period 1919–1985. Data were grouped into four areas, arranged in a south‐north transect; the Coastal, Guinea‐Savanna, Midland and Sahelian Zones. The series for retreat of rainfall showed evidence for quasi‐triennial and quasi‐6‐year oscillations, while that for rainy season length displayed quasi‐biennial and quasi‐triennial oscillations. No consistent spectral peaks emerged for changes in the date of onset of the rainy season. There is spatial coherence in variation in the date of the retreat of rainfall over the whole country, whilst for the date of onset of the season spatial coherence is limited to southern Nigeria (Coastal and Guinea‐Savanna Zones). Northern Nigeria (Midland and Sahelian Zones) and southern Nigeria (Coastal and Guinea‐Savanna) emerge as distinct areas in terms of spatial coherence in the variation of the length of the rainy season. There is also evidence for a secular change in the date of the retreat of rainfall for the whole country during the period 1939–1985, and in the date of onset of rainfall for southern Nigeria for 1968–1985.
Classification of the climate of England and Wales based on agroclimatic data
Authors: White E. J. , Perry A. H. 
Published: February 2007

AbstractClassifications of the climate of England and Wales, based on agroclimatic data from L. P. Smith, are described. A principal component analysis was carried out on these data in order to simplify them by removing inessentials. This showed that most variation in the variables was associated with maximum soil moisture deficit in summer and effective transpiration, both important for plant response. Six methods of cluster analysis were then used, two of which, further neighbour and minimum variance, were selected for comparison. The groups into which areas were classified are discussed in terms of the two climatological variables. The resulting classification was compared with others in the literature.
Principal components of the surface wind field in the United States: A comparison of analyses based upon wind velocity, direction, and speed
Authors: Klink Katherine , Willmott Cort J. 
Published: February 2007

AbstractThree statistical summaries of the 1975 surface wind field in the United States are computed using principal components analysis (PCA). Separate analyses of wind velocity and direction are made with vector‐based PCA, and the scalar (zonal and meridional) components of wind are described using a scalar‐based PCA. Comparisons indicate that results of the three PCAs are not equivalent. Vector PCA yields the most physically comprehensive components because the velocity observations are not decomposed into direction and speed, or into zonal and meridional coordinatesa priori.Directional and scalar‐based PCAs appear similar but since they only summarize one coordinate of velocity at a time, they represent incomplete descriptions of the wind field. Vector‐based PCA then is the most appropriate of the three for investigating wind fields or other vector‐valued data sets.