bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of evaporation in semi‐arid regions on the July circulation: A numerical study
Authors: Sud Y. C. , Fennessy M. J. 
Published: February 2007

AbstractIn this study, two 47‐day simulations were made with the general circulation model of the Goddard Laboratory for Atmospheric Sciences starting from the observed initial conditions for 15 June (00Z) 1979 as produced by NMC analysis. In the first simulation, the soil moisture was normally initialized and then allowed to vary by the model generated surface water balance. In the second simulation, the evaporation was prescribed and maintained zero in four chosen semi‐arid regions: the Sahel, the Thar Desert border in the Indian subcontinent, the Great Plains in North America and north‐east Brazil in South America. Elsewhere the soil moisture was calculated as in the first simulation. The two runs were identical in all other respects.The local climatology simulated by the GCM was analysed in the four anomaly regions. The mean July precipitation increased slightly in the Great Plains and Sahel regions, while it increased substantially (∼70 per cent) in the Thar Desert border region. However, in the north‐east Brazil region it decreased slightly. Relative thermal lows were created in each region, along with enhanced rising motion. There was also an increase in the mean monthly diabatic heating in all four regions. An analysis of the vertical structure of the moisture convergence field revealed that there was an increase in the low level moisture convergence in all of the anomaly regions. This compensated for the local moisture deficit created by the lack of evaporation.These results are based on one set of simulations representing the month of July. Further simulations would be required in order to evaluate their statistical significance.
The north‐west Australian cloud band: Climatology, characteristics and factors associated with development
Authors: Tapp R. G. , Barrell S. L. 
Published: February 2007

AbstractThe broad characteristics of the North‐west Australian Cloud Band, frequently observed across the Australian continent, are outlined. The cloud in the Band is most frequently first apparent within approximately 5° latitude and 17° longitude of 12DS 100°E, and may extend from there for several thousand kilometres, typically towards the east‐south‐east. It is found to be most in evidence during the winter months. Various atmospheric features associated with the development of the Cloud Band are discussed.
A system for predicting the onset of the north Australian wet‐season
Authors: Nicholls N. 
Published: February 2007

AbstractAn index is defined for the date of onset of the north Australian wet‐season, based on rainfalls observed at ten stations across tropical Australia. The index is shown to be reasonably representative of wet‐season onset throughout the area of interest. Some suggestion of bimodality is found in the frequency distribution of onset dates. An operationally feasible method for predicting the probability that the wet‐season will commence late is presented, building on earlier published work which has established the feasibility of prediction of seasonal rainfall near the date of onset of the wet. The forecast method uses the linear logistic equation and Darwin pressures observed in months prior to the onset to make predictions. Acceptable forecasts can be issued four months prior to onset. Two examples of the use of the method are provided.
Weather‐type classification by factor analysis in the Thessaloniki area
Authors: Maheras Panagiotis 
Published: February 2007

AbstractIn an attempt to study weather and climatological conditions in the Thessaloniki area during the winter period, a weather‐type classification is proposed according to principles first adopted by Russian authors. The methods of factorial analysis are used for this weather‐type classification. A study of the monthly and yearly frequencies of good, unpleasant, cloudy or overcast weather allows us to better understand the area's ‘atmospheric quality’ affecting man's life in it.
The effect of weather map scale on the results of A synoptic climatology
Authors: Yarnal Brent 
Published: February 2007

AbstractThe results of an objective synoptic climatology of glacier mass balance in south‐western Canada are affected by the scale and degree of generality of the synoptic patterns used. Two scales of 500 mb daily weather maps are compared. Statistical analysis shows little direct relationship between the two scales: the smaller, high wave number patterns vary randomly within the more general flow of the larger circulation patterns. However, further analysis suggests that the smaller synoptic patterns control glacier mass balance in coastal British Columbia. Glacier accumulation in the Canadian Rockies is more closely related to larger‐scale atmospheric flow.
Tendency prediction of precipitation and inundation in July in the Sichuan Basin, China
Authors: Ju‐Ying Chen 
Published: February 2007

AbstractIn July 1981, there occurred a comparatively severe flood and inundation in the Sichuan Basin. Before its occurrence, certain precursory phenomena appeared in the May 500 mb circulation field. The Western Pacific subtropical high apparently strengthened and extended westward, the mid‐latitudinal zonal circulation weakened, whereas the meridional circulation strengthened. At the same time, the astronomical background suggested a rainy period. All these precursory features unanimously indicated the probability of heavy precipitation and a tendency for flooding and inundation in July‐August, but especially in July, in the Basin. In this paper analysis and discussion emphasize the astronomical factors, the circulation factors and the prediction instrumentation which resulted in a successful prediction.
Air temperature variations in Greece. Part 1. Persistence, trend, and fluctuations
Authors: Giles B. D. , Flocas A. A. 
Published: February 2007

AbstractThis paper considers annual and seasonal variations of temperatures at three stations in Greece with at least 80 years of records. The extent and nature of non‐random changes, such as persistence, trend and fluctuations, are investigated. There is statistical evidence of both Markov linear and non‐linear persistence in the data depending on stations and season. The trend analysis showed little of significance, probably because of the time periods chosen. The data were subjected to a ‘lowpass filter’ of a Gaussian type and the series of fluctuations which resulted are discussed. Finally the data for all three stations were combined and filtered in order to show changes that have occurred in the Greek region during the twentieth century.
The Southern Oscillation, sea‐surface‐temperature, and interannual fluctuations in Australian tropical cyclone activity
Authors: Nicholls N. 
Published: February 2007

AbstractThe relationship between interannual variations of the number of tropical cyclones observed in the Australian region during a cyclone season and the Southern Oscillation (SO) has been explored. Strong, significant, stable correlations were found between the SO and cyclone numbers. Years with relatively many tropical cyclones were preceded by high North Australian SST, low east Pacific SST and low Darwin pressure. Such years also tended to be followed by the reverse pattern. The study confirms an earlier suggestion (Nicholls, 1979a) that Australian tropical cyclone activity is predictable some months prior to the start of the cyclone season. The observed correlations may result from feedback between the atmosphere and the ocean.
Rainfall over the southern slopes of the Himalayas and the adjoining plains during ‘breaks’ in the monsoon
Authors: Dhar O. N. , Soman M. K. , Mulye S. S. 
Published: February 2007

AbstractDuring ‘breaks’ in the south‐west (or summer) monsoon there is a general cessation of rainfall activity over most of the Indian area, but this activity increases over the southern slopes of the Himalayas and its adjoining plains. In this study, rainfall distribution during the ‘break’ monsoon situations has been studied, over the southern slopes of the Sikkim, Nepal and Uttar Pradesh Himalayas (i.e. from longitude 78°E to 89°E) and their adjoining plains. Rainfall distributions during the major ‘break’ situations which occurred during the principal monsoon months of July and August of the period from 1957 to 1969 were studied. This study has shown that, on a ‘break’ day, positive percentage departures of rainfall as high as 100 to 300 per cent have occurred at stations located in the outer Himalayas and the adjoining plains of north Bengal, east and central Nepal, Bihar and east Uttar Pradesh. However, the width of this heavy rain‐belt is maximum over the hills and plains of south‐eastern Nepal and the adjoining plains of north Bihar. This study has also shown that on a ‘break’ day there is a decrease of rainfall activity over the Himalayas west of longitude 80°E. Decrease of rainfall also takes place along a narrow belt immediately to the south of the great Himalayan range to the east of longitude 80cE outside Sikkim. Over the adjoining Gangetic plains, an increase in rainfall is noticed even to the south of the Ganga river in Bihar and its neighbourhood. Thus, owing to the increase in rainfall activity during ‘break’ monsoon situations in the catchments of Himalayan rivers located in Sikkim and Nepal, a peculiar situation arises which is responsible for causing floods in the downstream plains which experience almost drought conditions.
A comparative study of hailstorms in Switzerland, Canada and South Africa
Authors: Admirat Pierre , Goyer Guy G. , Wojtiw Lubomir , Carte Ernest A. , Roos Danie , Lozowki Edward P. 
Published: February 2007

AbstractA comparison of 5 to 20 years of qualitative and quantitative observations of hailfalls and hailstorms by three of the most active hail research groups in the world, shows very similar characteristics in a number of aspects of the hail phenomenon. The main similarities are that (a) the frequency of hailstorms decreases with increasing intensity, (b) the characteristics of hailstones (maximum size, number density) and hailswaths (length, surface area, energy) increase with increasing hailstorm intensity (i.e. lifetime, volume), (c) the single and multi‐cellular type storms are most frequent, whereas the supercell is rare, (d) the hail flux is not constant but pulsating, (e) the spatial structure of large hailswath is not uniform but contains ‘hailcores’ and (f) the post embryonic trajectories of common hailstones are often simple and similar.A number of differences are also observed between some of the regions, the main ones being (a) the upper limit of intensity of the more severe storms, (b) the succession and scale of cells in the storm development and (c) the percentage of various embryo types.A major conclusion of this comparative study is that the severe hailstorms, which cause most of the damage, are exceptional and show little similarity in the three regions. For the more requent light and moderate damaging ones, the study suggests that dynamics may be the result of pulsating phenomena.
A reappraisal of rainfall trends in the sahel
Authors: Dennett M. D. , Elston J. , Rodgers J. A. 
Published: February 2007

AbstractTwo rainfall series for the Sahel region of West Africa have been updated to 1983. Annual and monthly series are presented and analysed. Relatively dry conditions have persisted in this region since 1968 due mainly to a decline in rainfall during August, the wettest month. Drought has probably been less severe in this region during the late rather than the early 1970s because of better rainfall early in the season. It is suggested that agricultural planning should be based on rainfall records for the last twenty years.
The separate contributions of line squalls, thunderstorms and the monsoon to the total rainfall in nigeria
Authors: Bayo Omotosho J. 
Published: February 2007

AbstractUsing thunderstorm and rainfall information from five Nigerian stations for a five year period, the separate contributions of line squalls, thunderstorms and ordinary monsoons to the total rainfall and their variations with latitude are investigated. Total and thunderstorm rainfall decreases with increasing latitude but monsoon precipitation decreases exponentially while line squall rainfall is at a maximum around 9°N. Rainfall from thunderstorms shows a single annual peak in July/August at stations north of about 8°N whereas line squall precipitation exhibits a double maximum for all stations south of 12°N. It is also shown that, in the mean, line squalls are the most important rain producing systems, giving 47‐6 per cent of the mean total annual precipitation compared with 39 per cent and 13‐4 per cent from thunderstorms and ordinary monsoon rain, respectively.
A multivariate statistical model for forecasting anomalies of half‐monthly mean surface pressure
Authors: Maryon R. H. , Storey A. M. 
Published: February 2007

AbstractA multivariate statistical model for forecasting anomalies of surface pressure over Europe and the North Atlantic Ocean at medium to long range used routinely in the Synoptic Climatology Branch of the Meteorological Office is described. The model discriminates between broad classes of circulation type using a multivariate predictor space (including areal sea surface temperature anomalies). The forecasts may take categorical or probabilistic form, and the likelihood of the occurrence of categories of circulation index, temperature and rainfall over the U.K. can be produced using Bayesian methods. Emphasis is laid on the difficulties of applying classical statistical analysis to atmospheric fields, as this important aspect of long range forecasting by empirical methods tends to be neglected in the literature.
The northwest african depressions affecting the south balkans
Authors: Prezerakos Nicholas G. 
Published: February 2007

AbstractThis paper deals with the north‐west African or the Atlas depressions, named after the region of their formation. The subject is examined from the synoptic climatology point of view, and is based on mean sea level (M.S.L.) pressure and 500 hectopascal (hPa) heights of the five consecutive years from 1970 to 1974. Attention is drawn to the following topics.1. The positions of the depression centres are determined when they are generated and afterwards. So the numbers of the occurrence of their centres in the subregions into which north‐west Africa is divided and the tracks of these centres are obtained.2. These depressions are divided into four categories. The first category is divided into four subcategories, whereas each of the remaining categories is divided into two subcategories. These categories are based on the 500 hPa flow patterns.3. For each subcategory, mean charts of the 500 hPa height for the first occurrence of its depressions have been prepared. For these mean charts, the relative vorticity advection has been calculated. These charts suggest the region of the first occurrence of the depressions is mostly in a region of positive advection of vorticity.4. The percentage of the number of depressions from each subcategory affecting the weather of Greece can be determined. For each percentage, the mean M.S.L. pressure and 500 hPa height charts showing the time at which these depressions start affecting the weather of Greece are drawn. Thus, the synoptic situations affecting Greece and resulting from the north‐west African depressions are determined.Finally, the rain, wind and temperatures from each north‐west African depression subcategory occurring in Greece and especially in the Athens major region are discussed.
A preliminary analysis of long‐term visibility trends in central scotland
Authors: Lee D. O. 
Published: February 2007

AbstractMedian visibilities are calculated for four sites in central Scotland for summer and winter seasons over the period 1962‐1982. A steady improvement in visibility at all sites has taken place, but especially in winter at the two urban sites. The relative importance of climatological and air pollution influences is uncertain, but the effects of the 1973 oil crisis on summer visibility, through reduced sulphur emissions, appears to be much less evident than in southern England.
Application of a radiative cooling model to daily minimum temperature prediction
Authors: Gandia S. , Melia J. , Segarra D. 
Published: February 2007

AbstractA model of exponential decrease of temperature is applied to the study of night cooling in an agricultural area of citrus orchards located near the Valentian Coast (Spain). A set of annual average parameters which determine that cooling is obtained by using temperature measurements at different levels during two years. These parameters appear to be representative of the thermal behaviour of the area of study.The attainment of such parameters allows a prediction of the minimum temperatures of the area to an accuracy of £1.5 K, knowing the temperature at sunset and some time later.
On the 1983 drought in North‐East Brazil
Authors: Rao V. Brahmananda , Satyamurty P. , De Brito José Ivald O. B. 
Published: February 2007

AbstractExamination of the rainfall data for north‐east (NE) Brazil showed that the drought of 1983 was extensive. In the interior dry region, rainfall during the rainy season of 1983 was less than 40 per cent of the normal. Analysis of the rainfall revealed that the drought of this year was the worst in the past 20 years. Rainfall anomalies over NE Brazil are related to the Southern Oscillation and sea surface temperature (SST) anomalies in the tropical Atlantic Ocean. Variations in the Southern Oscillation index preceded the corresponding rainfall anomalies by about 2 months. Correlation coefficient between the NE Brazil seasonal rainfall and mean monthly SST anomaly in the tropical Atlantic showed a gradual increase from January to March. However, examination of sea surface temperature anomalies in the Atlantic for the first 3 months of 1983 indicated only a weak relationship with rainfall anomalies. This suggests that for the 1983 event east‐west Walker type circulation was more important than the north‐south meridional circulations forced by SST anomalies in the Atlantic.
Variability of climatic boundaries in Israel—Use of modified Budyko‐Lettau aridity index
Authors: Joseph Joachim H. , Ganor Eliezer 
Published: February 2007

AbstractA modified Budyko‐Lettau dryness, ratio, D*, has been used to depict the fluctuation of climatic boundaries in Israel during the period 1963–1973. The analysis is partly based on and partly compared with the available climatic data.The use of D* for the analysis of regional year‐to‐year climatic fluctuations in nature or in numerical climate simulations seems to be warranted.
Some aspects of rainfall associated with cyclonic storms of the Bay of Bengal
Authors: Mooley D. A. , Mohile C. M. 
Published: February 2007

AbstractMean and maximum rainfall associated with cyclonic storms of the Bay of Bengal striking the two sections of the east coast of India are studied by examining the rainfall distributions along the coast on both sides of a point (P) at which the storms struck the coast at a right angle during the period 1877–1980. The distributions are presented for mean and maximum rainfall recorded during the 24 hours of the day of crossing and the previous two days. Extensive rainfall, of wavy pattern to the north of P and intensive rainfall to the south of P are observed. Possible reasons for these are given.Rainfall recorded within 1° on either side of P associated with each storm has been examined from the viewpoint of suitability of a statistical model. The distribution is highly skewed. The gamma distribution, which covers a wide range of skewness, has been tried. It is seen that a gamma probability model shows a good fit to the mean rainfall over this area.Variability of rainfall within a distance of 1° on either side of P is also studied and it is found that variability is more in the southern sector than in the northern sector.
On a relationship for estimating precipitable water vapour aloft from surface humidity over West Africa
Authors: Adedokun J. A. 
Published: February 2007

AbstractA relationship of the form W = αqb(α, b constants) has been established between precipitable water W(cm) aloft and the surface specific humidity, q(g/kg) over West Africa using an analysis of variance (ANOVA) technique on upper air climatological data spanning over a decade.Owing to the difference in the climatological patterns of the precipitable water between the southern and northern zones of the region, no single relationship was found suitable for both zones. Consequently, separate values of α, b have been obtained for each of the Northern and Southern zones; namely for the Northern zone (α, b) = (0.271, 1.039) and for the Southern zone, (α, b) = (6.45 × 10−4, 3.154).Initial tests carried out on the model using daily soundings made over the region during the West African Monsoon Experiment (WAMEX) gave encouraging results as established by use of Kolmogorov‐Smirnov tests. Earlier models, generally of the form: In W = A + Btd (A, B constants and td, dew‐point temperature (°F)) tried on the same basis were found to be rather inadequate over the region.
Minimum temperature surveys based on near‐surface air temperature measurements and airborne thermal scanner data
Authors: Kalma J. D. , Laughlin G. P. , Green A. A. , O'Brien M. T. 
Published: February 2007

AbstractMinimum air temperature measurements and airborne thermal scanner measurements of apparent surface temperature were obtained in a regional frost risk study in gently undulating grazing country in the Southern Tablelands of New South Wales, Australia.The minimum air temperature data obtained at 7 sites on 100 nights have been used to derive a predictive relationship between temperature lapse rate and night‐time wind speed and net radiation loss. An extended network was used on 30 nights using an additional 24 sites. Excellent agreement was observed between the lapse rates collected from both the 7‐station and 31‐station networks on 24 nights.Maps of minimum air temperature across the region have been obtained for selected individual nights using Laplacian smoothing spline functions based on elevation and map co‐ordinates.Thermal scanner data were obtained with an aircraft on two nights and the paper presents detailed comparisons between apparent surface temperature data and minimum air temperatures obtained from the regional maps.These comparisons have made it possible to successfully distinguish between broad topographic controls and the effect of local surface characteristics, especially in the case of high‐resolution thermal scanner data. Such local controls include the effects of trees, surface water and various man‐made features, as well as very local topographic features such as narrow depressions, which are only noticeable from site surveys and detailed aerial photography. It is concluded that thermal imagery is an important aid in understanding spatial distribution patterns of night‐time air temperatures and hence in regional frost risk assessment.
An index method for analysing precipitation surplus or deficit: Preliminary developments
Authors: Sefe F. T. K. 
Published: February 2007

AbstractAn index method for analysing precipitation surplus or deficit is presented. By indexing the surplus or deficit to the long‐term mean annual precipitation, temporal and spatial comparisons are facilitated. Preliminary results indicate that the computed indices are normally distributed and are amenable to the types of frequency and probability analyses normally used in water resources problems. It seems that the computed indices could be used for characterizing the intensity and severity of a precipitation deficit or drought spell.