bluuebunny/crossref_metadata_2025_split huggingface dataset:
some aspects of daily rainfall distribution over India during the south‐west monsoon season
Authors: Soman M. K. , Kumar K. Krishna 
Published: February 2007

AbstractThis paper presents the results of an analysis of the daily rainfall at 365 Indian stations for the 80‐year period, 1901–1980. The rainfall data relate to the south‐west monsoon season June to September (122 days), which accounts for the major part of the annual rainfall over most parts of the country. For each of the stations the rain‐days are arranged in ascending order of rain amount, and the association between the cumulated percentage rain amount (x) and the cumulated percentage number of rain‐days (y), designated as the normalized rainfall curve (NRC), is calculated. It has been shown in an earlier study that x and y are related by the equation x = y exp [— b(100—y)c], where b and c are empirical constants that depend on the coefficient of variation (CV) of the rainfall series. This equation has been utilized to study various parameters of the daily rainfall distribution.The coefficient of variation of the daily rainfall series varies between 100 per cent and 230 per cent at individual stations, with nearly half the number of stations having CV values in the range 130–150 per cent. The number of days of significant rainfall (days with rainfall greater than the mean intensity per rain‐day) constitute about 30 per cent of the total number of rain‐days and account for about 75 per cent of the seasonal rainfall at almost all the stations.
Tropical‐extratropical cloudbands in the Australian region
Authors: Kuhnel Ivan 
Published: February 2007

AbstractThe climatology of the tropical‐extratropical cloudbands (TECBs) in the Australian region is examined, using a subdivision of the cloudband phenomena, according to their convective sources of origin. In addition to previously described parameters (e.g. amplitude of mid‐latitude troughs, cross‐equatorial flow, jet stream), the 1979–1983 TECB activity is analysed with respect to other indices, such as global pressure and sea‐surface temperature, the Southern Oscillation Index (SOI), 40–50‐day oscillation, Hadley cell circulation or cloudiness anomalies. It is shown that during a period marked by a significant decrease in the TECB activity, 5–6 months prior to the lowest value of the SOI, the TECB tends to develop in 40–50‐day intervals, whereas otherwise, its development can be associated with higher frequency (18–21 day) oscillations. Similar fluctuations have also been observed in tropical cloudiness in the TECB area of origin. On a large‐scale, the TECB activity seems to be closely linked to large‐scale pressure fluctuations in the Indian and northern Pacific Oceans.
Volcanic aerosols, El Niñmo and the Southern Oscillation
Authors: Handler Paul , Andsager Karen 
Published: February 2007

AbstractIn this paper some of the questions raised by Nicholls (1988) concerning the relationship of volcanic aerosols to the El NiñMo/Southern Oscillation are examined and answered. Using Monte Carlo techniques, the statistical significance of the composite sea surface temperature (SST) anomalies and the Southern Oscillation Index (SOI) are reexamined both before and after the eruption of a set of low‐latitude volcanic eruptions. Significantly warmer SST and negative SOI anomalies are found in the composites immediately following the eruption period. These significant anomalies after the composite eruption season are found not to depend on the appearance of cooler SST and positive SOI before the key season, a possibility suggested by Nicholls (1989). This result is in agreement with Parker (1988). The volcanic hypothesis states that low‐latitude volcanic aerosols are the immediate and only cause of warmer than normal SST or El NiñMo. This implies that when no low‐latitude aerosol is present the SST should be cooler than normal. Both of these aspects of the volcanic hypothesis are found to be satisfied to a very high level of statistical significance by the observed SST and SOI data.
Temporal and spatial characteristics of annual precipitation over the balkans in the twentieth century
Authors: Maheras Panagiotis , Kolyva‐Machera Fotini 
Published: February 2007

AbstractA study of the annual totals of precipitation is presented for 12 stations in the Balkan area for a period of 92 years (1894–1985) The homogeneity of the precipitation series is examined, and their statistical characteristics are analysed. An abrupt climatic change is found at the station of Belgrad, and a statistically significant trend of annual precipitation is found for various periods for the stations of Kerkyra, Patras, Hvar, and Sarajevo. Persistence is only ascertained for the Belgrad station. The application of principal component analysis has yielded three groups of stations. Group A includes northern and continental stations, group B includes stations of the Ionian and Adriatic Seas, and group C includes the stations of Thessaloniki and Athens. The most important period of fluctuations covers the years 1933–1953, when a humid period is followed by a dry period. The most recent 5‐year period can be described as a very dry one.Finally, comparison between rainfall fluctuations and types of circulation shows that the predominance of meridional circulation over the Balkans results in an increase of precipitation, whilst a zonal circulation results in a decrease of precipitation.
Characteristics of the low‐level temperature inversion along the Alaskan Arctic coast
Authors: Kahl Jonathan D. 
Published: February 2007

AbstractThe climatological characteristics of low‐level tropospheric temperature inversion along the Alaskan Arctic coast are examined from a 10‐year record of surface and upper‐air meteorological data at Barrow and Barter Island, Alaska. The meteorology at the two stations is found to be remarkably similar; surface‐based inversions occur nearly half of the time, but even in the winter months inversions are frequently based up to 200 m above the surface. Median inversion depths range from 250m to 850m, with median temperature differences across the inversion ranging from 2°C to 11°C. In March and April when the inversion is strongest, the lowest levels frequently erode. This indicates that the transient character of the inversion reduces its effectiveness as a barrier to vertical mixing. The inversion depth closely follows the annual cloud‐cover cycle, demonstrating that the development and maintenance of the inversion is a result of complex interactions between radiative forcing, synoptic activity, and sea‐ice dynamics.
Space–time variability of rainfall in April and October–November over East Africa during the period 1932–1983
Authors: Beltrando Gérard 
Published: February 2007

AbstractThe space–time variability of precipitation over East Africa during the two rainy seasons (April and October–November) is investigated using a network of 56 stations for the period 1972–1983 and 32 stations for the period 1932–1983. The analysis relies on a model of two‐mode variance with rotation, which determines homogeneous groups of stations having a common time evolution.During April, three components represent a large part of the variance with their cores (i) near the Zanzibar channel, (ii) the Kenyan‐Tanzanian highlands and eastern Lake Victoria, and (iii) the southern part of the Tanzanian highlands. During the October–November rainy season, rainfall is more homogeneously distributed. The first component takes account of 60 per cent of the variance and encompasses a large part of the domain, except southern inland Tanzanian stations and western and northern Ugandan stations.Spectral analysis of the time series associated with the space component reveals peaks around 5–6 years, which appears to be the major periodicity over East Africa.
Low‐latitude volcanic eruption signal in Indian surface air temperatures
Authors: Hingane L. S. , Kumar K. Rupa , Patil S. D. 
Published: February 2007

AbstractThe effect of major low‐latitude volcanic eruptions on the all‐India mean surface‐air temperature has been studied using data for the period 1899–1985, by using superposed epoch analysis over 36 months before and after the month of eruption. The eruptions are grouped into three categories and their effects on monthly temperatures are presented. In general, there is no evidence of persistent decrease in the mean annual temperature following the eruptions. There is, however, an abrupt and significant surface cooling over India in the first 2 months following northern hemispheric eruptions, with recurrent drops in the next 2–3 years. Southern hemispheric eruptions do not show any effect on the Indian surface temperatures.
On the annual and seasonal patterns of rainfall fluctuations in sub‐saharan West Africa
Authors: Adejuwon J. O. , Balogun E. E. , Adejuwon S. A. 
Published: February 2007

AbstractMonthly rainfall data for 16 stations in Nigeria were collected for the period 1922–1985. From this, the annual, the wet season, the onset, the peak, and the retreat rainfall data were derived. The patterns of fluctuations of rainfall were analysed therefrom. The series were first examined for trends and then for periodic fluctuations. Trend analysis revealed that a majority of the series exhibit negative trends, and in some cases the trends were significant. For all the series analysed, there is the general tendency towards increasing aridity. Spectral analysis indicates prominent periods of between 2‐and 8‐year cycles. Other periodicities observed include 16‐, 18‐, and 21‐year cycles.
Autumn and winter daily precipitation areas in Wales, 1982–1983 to 1986–1987
Authors: Bonell Mike , Sumner Graham 
Published: February 2007

AbstractDaily precipitation data from 121 sites for five autumn‐winter seasons (September to January, 1982–1983 to 1986–1987) have been analysed to determine discrete precipitation areas within Wales, using S‐mode principal components (PCA) and cluster analyses. Using unrotated PCA, much of the variation in daily precipitation is explained by the first five PCs, representing an accumulated variance of 75.7 per cent. The first four PCs appear to relate respectively to: altitude (60.8 per cent of the total variance explained), an exposure effect relative to north or north‐east winds (6.0 per cent), a ‘westerly exposure’ effect (4.2 per cent) and an ‘easterly exposure’ effect (2.9 per cent). The fifth PC, with high scores only over Ynys Mǒn and Gwent, could not be attributed to any particular influence. Oblique rotation produced a better simple structure, enhanced the apparent importance of exposure to wind from the main compass directions, but lessened that of altitude. Three methods of clustering PCs were subsequently tried on the Oblimin solution: centroid, median and Ward. The precipitation areas produced by each were broadly similar, and the boundaries between them often coincided with clear topographic units, influenced by exposure and shelter effects. The Ward technique yielded the areas best defined in terms of topography and exposure, and best satisfied criteria determined by the nature of the data themselves.
A method for classification of wind field patterns and its application to southern California
Authors: Green Mark C. , Myrup Leonard O. , Flocchini Robert G. 
Published: February 2007

AbstractA method for classification of wind field patterns is described. The method forms groups of days having similar wind field patterns, including their diurnal variations. The expansion coefficients of the first eigenvector of an empirical orthogonal function analysis of the vector wind were used to determine if pairs of days are similar. A grouping procedure was then applied to form groups of similar days. Diurnally varying best‐fit wind fields were generated for each group of similar days, or types. The method was applied to southern California each season for a 2‐year period. Averaged mesoscale pressure and specific humidity fields were computed for each wind field pattern. Cause and effect relationships between the pressure, wind, and humidity fields in the complex topographic and meteorological setting are demonstrated.
Continentality: A basic climatic parameter re‐examined
Authors: Driscoll Dennis M. , Fong Juan M. Yee 
Published: February 2007

AbstractContinentality, a basic control of climate, is difficult to quantify in terms of the factors that govern it. As a result, a chief consequence of continentality, annual range of temperature, has been used as a surrogate. Annual range, however, is determined primarily by seasonal variations in radiation receipts, and attempts at constructing continentality indexes have attempted to compensate for this variation by dividing annual range by the sine of the latitude. In so doing it has been assumed that the latitudinal variation of seasonal radiation increases monotonically with latitude. It is shown that this is not the case; thus, indexes of continentality based on this assumption are flawed.A continentality index based not on annual range of temperature, but on residuals from the regression line of annual temperature range on latitude, is formulated. The result is a maximum of continentality in the location suggested by a qualitative look at the factors influencing it. Additional advantages to this approach are specified.
A five‐year climatology of elevated inversions at Hemsby (UK)
Authors: Milionis A. E. , Davies T. D. 
Published: February 2007

AbstractTemperature inversions up to the 500‐mbar level are studied in 50‐mbar depth layers over Hemsby, in eastern England. The inversions are characterized by vertical gradients of temperature, potential temperature, dew point temperature, and depth. An inversion index, which is the product of potential temperature gradient and frequency of occurrence, is used. The zone of maximum activity for elevated inversions is 950–800 mbar, resulting from subsidence within anticyclones. A theoretical explanation of the processes is given. Inversion characteristics are essentially similar for day and night, except in the 1000–950‐mbar layer, where daytime frequency is greater. It is suggested that turbulence‐capping inversions and/or sea‐breeze effects may be the reason. The implications of elevated inversions for air pollution dispersion are discussed.
700‐HPA geopotential height anomalies from a statistical analysis of the French Hemis data set
Authors: And Sylvie Clinet , Martin Serge 
Published: February 2007

AbstractThe low‐frequency time variations of the Northern Hemisphere 700‐hPa heights have been investigated using the French Hemis grid‐point data set and a statistical model based upon an orthogonal rotated principal component analysis. The data consists of 389 10‐day means of geopotential height (from 1970 to 1980) distributed over an octagonal grid of 1977 points, poleward of 20°. The model summarizes the major modes of 700‐hPa height fluctuations; for each mode, it provides the corresponding spatial pattern and the associated time component.Four seasonal analyses have been performed using 10‐day means. The major modes of the spatial anomaly structure are described in detail and are clearly identified for each season. The stability of these modes through the separate seasonal analyses is examined. The robustness of the resulting patterns is analysed through their consistency with results of other studies.
The suburban energy balance: Methodological considerations and results for a mid‐latitude west coast city under winter and spring conditions
Authors: Grimmond C. S. B. 
Published: February 2007

AbstractPrevious measurements of the urban energy balance primarily have been conducted in summertime. This paper reports the first extended set of winter‐spring‐time energy balance measurements for a city. The study was conducted in a suburb of Vancouver, British Columbia, from January to June 1987. It included hourly measurements of net all‐wave radiation, sensible heat flux and the Bowen ratio. The anthropogenic and storage heat fluxes were modelled. A dynamic source area model was employed to ensure the modelled parameters were consistent spatially with the measured turbulent fluxes. The winter‐spring urban energy balances observed in this study are different to those reported for summertime conditions at the same site. The fluxes for the entire period are not symmetrical about solar noon. Hence earlier interpretations possibly should be modified. Apart from this feature the spring season balances are similar to those reported for the summertime in terms of relative importance of individual fluxes. The wintertime energy balance appears to be different to that of spring and summer. The most noticeable feature is the increased importance of the latent heat flux, which on average is the largest output flux in the balance. A secondary, more expected feature, is the increased importance of anthropogenic heat flux as an input in winter.
Synoptic climatology of thermal low‐pressure systems over south‐western north America
Authors: Rowson David R. , Colucci Stephen J. 
Published: February 2007

AbstractAnalyses of closed‐isobar, non‐migratory, thermal low‐pressure frequencies are presented for an 11‐year period, 1974–1984, over the south‐western USA and north‐western Mexico. Average onset and breakdown dates, preferred locations, and the vertical extent of the system are presented. The effect of upper level (500 mbar) flow on the presence of the thermal low and relationships between the system and precipitation in Arizona and western Mexico also are investigated. The analyses suggest a preferred region for the formation and sustenance of the thermal low near the south‐west coast of the USA and the west coast of Mexico. Within this region exist two frequency maxima, centred over the desert regions of the American South‐west and north‐western Mexico and over the plateau highlands of the Sierra Madre Occidental. The system is most prevalent from mid‐June until mid‐September and reaches its maximum vertical extent near 700 mbar in July and early August. This variation may be attributed to the zenithal progression of the sun, although short‐term fluctuations in the strength of the system during the summer period probably are related to changes in cloud cover over the low. Specifically, precipitation in advance of 500‐mbar troughs passing to the north of the system appears to be associated with the weakening of the thermal low, suggesting a negative feedback relationship that deserves further investigation.
Rainfall changes in Africa: 1931–1960 to 1961–1990
Authors: Hulme Mike 
Published: February 2007

AbstractIt remains common for 1941–1970, or even 1931–1960, climatological rainfall normals to be used in applied climate studies in Africa. Often this is due simply to the easier availability of station means or rainfall maps for these periods. Such rainfall statistics, however, are unrepresentative of recent decades, especially the new World Meteorological Organization standard period, 1961–1990. In this paper two independent 30‐year rainfall climatologies for Africa are constructed from 572 quality controlled station time series of monthly rainfall. These climatologies are for the periods 1931–1960 and 1961–1990 and are constructed on a 5° grid. Differences between these two 30‐year periods are determined with respect to mean seasonal rainfall, interannual variability and rainfall seasonality. Latitudinal profiles of mean seasonal rainfall emphasize the dominance of reduced Sahelian rainfall in the rainfall changes occurring over this period. This decline in boreal summer rainfall is shown to be statistically significant using field comparison statistics. Annual time series of regional rainfall anomalies for the Sahel, East Africa and south‐western Africa are constructed; these three time series possess quite different interannual rainfall characteristics. Possible explanations for these observed rainfall changes are discussed with respect to land cover changes, global sea‐surface temperature patterns, and greenhouse gas forcing.
Precipitation events in the south‐east United States of America
Authors: Robinson Peter J. , Henderson Keith G. 
Published: February 2007

AbstractA precipitation event climatology is defined as the frequency distributions of the number, duration, and precipitation amounts of individual rainfall events at an observing station. A preliminary analysis of hourly precipitation records for 27 stations in the south‐east United States of America for the 1958–1987 period indicates that the operational definition of an event is a period of continuously recorded precipitation separated from other such periods by a dry interval of 2 h or more. The choice of the 2‐h separation interval influences the climatological frequency distributions slightly, but maintains a distinction between convective and cyclonic systems. All south‐eastern stations displayed similar results, the average number of events varying from near 30 in autumn to about 40 in summer. Most events lasted less than 3 h and gave less than 0.2 in. of precipitation. The seasonal and spatial variations in results suggest close connections between the event climatology and the atmospheric circulation. Short‐duration storms suggestive of convective activity dominated in all seasons in Florida. To the north the winter maximum in durations and amounts indicated the importance of depression passage, while increased durations in all seasons over the Appalachian mountains reflected a topographic influence. A general region‐wide relationship between the number of events per season, the seasonal total precipitation, and the seasonal number of rain days was obtained, but the results varied greatly from station to station.
Validation of trends in the surface wind field over the Mozambique channel
Authors: Bigg Grant R. 
Published: February 2007

AbstractThe evolution of the atmospheric circulation over the Mozambique Channel over 1950–1987 is examined, using ship and land‐based pressure gradients as consistency checks on the surface wind field over the ocean. It is found that in the austral summer, when the Inter‐Tropical Convergence Zone crosses the region, the winds show little evidence of change. However, in the winter the prevailing southerly winds in the north of the channel show evidence in both pressure records and wind data of a significant strengthening.
18.6‐year luni‐solar nodal and 10–11‐year solar signals in rainfall in India
Authors: Mitra Kumares , Dutta S. N. 
Published: February 2007

AbstractThe 115 year (1871–1985) long, summer monsoonal rainfall data of ten macroregions (m‐r) of India have been subjected to maximum entropy spectral analysis (MESA). The results appear to indicate quasi‐periodic fluctuations in rainfall in eight and six m‐r, presumably corresponding to the 18.6–year luni‐solar nodal and 10–11‐year solar cycles respectively. The solar term in the remaining four m‐r appears to be split up into two components, as a result of spectral analysis. The filtered data, evidencing either or both of the signals in MESA, were then subjected to two band‐pass filters, centred at 19.0 and 10.5 years respectively. The derived rainfall waveforms are found to have some good phase relationships with the 18.6–year nodal and 10–11‐year solar cycles, when relatively free from meteorological disturbances. The luni‐solar rainfall waveforms in m‐r 2, 3 and 7 exhibit the phenomenon of a sudden 180° phase change in the early parts of the data series.