bluuebunny/crossref_metadata_2025_split huggingface dataset:
Topographical and coastal influence on spatial precipitation patterns in Tunisia
Authors: Berndtsson Ronny 
Published: February 2007

AbstractThe spatial properties of the correlation structure based on daily rainfall data from 67 stations throughout Tunisia over a 5‐year period are examined. The correlation structure is generally markedly anisotropic as influenced by topography and the coast. These two factors seem to influence the correlation pattern differently during different months. The mean areas within the 0.7 correlation isoline for all subgroups vary from about 1000 km2 in the early autumn to about 7000 km2 in the winter months.
Application of a climate departure index to the study of freeze dates and growing season length in the south‐eastern United States
Authors: Suckling Philip W. 
Published: February 2007

AbstractA climate departure index (CDI) is utilized to study the variability of last spring‐freeze dates, first autumn‐freeze dates, and growing season length in the south‐eastern United States for the period 1911–1986. The CDI is useful for determining how ‘normal’ or ‘unusual’ a particular year is compared to the long‐term situation for the region under consideration. This study shows that when distinct long‐term climatic trends exist for the climatic element under study, the CDI should be calculated using residuals from a trend line rather than simply comparing individual yearly values to the long‐term average.With respect to last spring‐freeze and first autumn‐freeze dates and growing season length in south‐eastern United States, the CDI analysis illustrates that a period of rather ‘normal’ conditions occurred during the late 1950s to early 1970s. Slightly higher CDI values for the 1980s, which implies a greater occurrence of extreme events (i.e. greater climatic variability), is not unprecedented given the high CDI values earlier in the century. The decade of the 1940s especially experienced a greater frequency of unusual last spring‐freeze dates and first‐autumn‐freeze dates (either extra early or late) as well as larger variations in growing season length.
Spatial and temporal variations in Australo‐Indonesian region cloudiness
Authors: Kuhnel Ivan 
Published: February 2007

AbstractSpatial and temporal variations in cloudiness of the Australo‐Indonesian region are examined with the help of a newly created cloudiness data set, based on GMS‐IR imagery. As represented by the first Varimax rotated principal component pattern of the Australo‐Indonesian region cloudiness, the band of tropical cloudiness is dominated by a clearly defined eastward cluster propagation, as well as a more complicated 40–50‐day oscillation pattern. Details of these phenomena are discussed.
Surface humidity and precipitable water vapour linkage over west and central Africa: Further clarification and evaluation of existing models
Authors: Adedokun J. A. 
Published: February 2007

AbstractIn the light of currently available upper air data for West Africa, an intensive examination is carried out on the linkage between surface humidity and precipitable water vapour, W, over the region, with a view to validating existing empirical models as well as identifying seasonal variability in their applicability.For this objective, calculations of precipitable water vapour using available monthly mean upper air data from 13 stations in West and Central Africa (for the period 1971–1984) have been carried out and a comparison made with results from empirical models using the Kolmogorov‐Smirnov test.While overall fair agreement was obtained between actual and estimated values of W, using the power law relationship of Adedokun, it was found that the model performed better during the rainy season than during the Harmattan. Ojo's InW‐td(td, dew‐point temperature) linear model, however, performs better during the Harmattan than the rainy season.The location of the Inter Tropical Discontinuity (ITD) relative to the various stations and ocean‐atmosphere interaction effects pose as controls to the regime of application of these surface humidity based models. An update of the regression base period used may be necessary for better performance.
Tropical‐extratropical cloudband climatology based on satellite data
Authors: Kuhnel Ivan 
Published: February 2007

AbstractA global tropical‐extratropical cloudband (TECB) climatology, using a clear definition of TECBs, and based on NOAA IR satellite imagery for the period 1979–1983, is presented. It is shown that on a global scale we can distinguish between 14 different TECBs, seven of them in each hemisphere. The cross‐correlations of the TECB frequency anomalies with tropical pressure and sea‐surface temperature anomalies indicate that the activity of these phenomena can respond strongly to tropical forcing from different parts of the world. Whereas only 10 TECBs show a significant response in their activity to the Southern Oscillation, the frequency anomalies of all 14 TECBs correlate significantly with other pressure anomaly indices.
A satellite‐derived climatology of polar‐low evolution in the North Pacific
Authors: Yarnal Brent , Henderson Keith G. 
Published: February 2007

AbstractA climatology of polar‐low evolution for seven low‐sun seasons (November to March) in the North Pacific is presented. The data were collected by the subjective interpretation of Defense Meteorological Satellite Program (DMSP) infra‐red imagery, using a cloud vortex classification scheme designed especially for use with medium to high resolution imagery. For the study period, about two‐thirds of all polar lows that formed over the North Pacific evolved to a higher stage. Approximately one‐half of those (one‐third of the total) passed through all stages of development from cyclogenesis to decay. The more common form of cyclogenetic polar low in the North Pacific, the comma cloud, continued to develop two‐thirds of the time, while the less common spiraliform only evolved to a higher stage of development in two‐fifths of the cases. Those polar lows that formed in certain key areas were likely to evolve to a higher stage, while other specific locations discouraged continued development. No readily discernible difference between gross size and cloud characteristics of evolving and non‐evolving polar lows was present in the satellite data, suggesting that additional data are needed to forecast correctly which will develop into mature cyclones.
Regionalization of thunderstorm rainfall in the contiguous United States
Authors: Easterling David R. 
Published: February 2007

AbstractThe amount of precipitation recorded during individual thunderstorms was determined at 220 stations in the contiguous United States of America for a 30‐year period. The probability distribution of thunderstorm rainfall amounts at each station during each season was summarized by use of the incomplete gamma distribution. The incomplete gamma distribution is completely described by two parameters, which were used in a clustering routine to determine whether regionalizing tendencies exist in the probability distributions. Large‐scale regions were found when the results of the clustering were mapped. In general, these regions corresponded well with the areas of dominance of many of the proposed mechanisms for thunderstorm development.
Hawaiian drought and the Southern Oscillation
Authors: Chu Pao‐Shin 
Published: February 2007

AbstractLong‐term rainfall records at key locations on the Hawaiian Islands and the Southern Oscillation Index (SOI) are examined to reveal the impact of large‐scale atmospheric circulation on Hawaiian rainfall. By compositing six major drought winters, it is found that they were preceded by a persistently low phase of the Southern Oscillation starting from March of the preceding year. Correlation analysis indicates that the spring SOI is not significantly correlated to rainfall in the subsequent seasons. In contrast, changes of the SOI in summer lead corresponding changes of rainfall by two to three seasons. Similarly, changes of the SOI in autumn lead changes of rainfall by one to two seasons. These results are also confirmed by scatter diagrams. Although a large negative SOI anomaly in summer or autumn can be regarded as a precursor to a drought for the following winter or spring, the inverse relation, namely, a positive SOI anomaly leading abundant rainfall does not necessarily follow. As an empirical rule, a value for the summer SOI of −2 or below, or a value for the autumn SOI of −1 or below, or both, indicate the occurrence of a dry winter.During drought episodes, Hawaii was located under an area of strong subsidence, and synoptic systems that normally produce winter and spring rainfall in the Hawaiian Islands were retarded. An anomalously cold sea‐surface temperature in the north‐central Pacific may also further enhance and prolong the dryness by reducing the rate of evaporation from the sea surface and by stabilizing the overlying air.Individual forecasts carried out for recent years reveal that severe drought during an El Niño/Southern Oscillation (ENSO) winter could be predicted two seasons in advance using simple regression models. For the non‐ENSO drought winter, forecasting ability degrades somewhat. Overall, by means of a cross‐validation technique, antecedent conditions of the large‐scale pressure see‐saw are useful predictors for Hawaiian winter rainfall anomalies, particularly when an ENSO‐like phenomenon has started to develop.
Preliminary measurements of net radiation and evaporation over bare soil and fallow bushland in the Sahel
Authors: Wallace J. S. , Gash J. H. C. , Icrisat M. V. K. Sivakumar 
Published: February 2007

AbstractNet radiation and evaporation are compared over two contrasting land surfaces, fallow bushland and bare soil, in Niger, West Africa. Data are presented for 6 days, before and after a large rainstorm (39 mm), which illustrate how evaporation from the bush vegetation changed little in comparison with the larger change in evaporation observed over the bare soil. Net radiation over the bush vegetation was 20 per cent greater than that over the dry bare soil, but only 12 per cent greater than that over wet bare soil. These differences are consistent with the expected difference in albedo and surface temperature of the two surfaces.
Satellite climatology of ‘polar lows’ and broadscale climatic associations for the Southern Hemisphere
Authors: Carleton Andrew M. , Carpenter Duane A. 
Published: February 2007

AbstractA climatology of polar air cloud vortices (so‐called ‘polar lows’) is derived for the Southern Hemisphere using sets of medium resolution (5–4 km) DMSP (Defense Meteorological Satellite Program) imagery. The climatology is for the winter season (June through to September) and covers the 7–year period 1977–1983. Both comma cloud and spiraliform polar air signature types are considered, as identified in recent satellite studies for the Northern Hemisphere. The comma clouds dominate over a wide range of ocean latitudes, whereas the spiraliform systems occur less frequently (about 1:10 for the hemisphere), and show maximum frequencies in sea ice latitudes around mid‐winter (about 1:3).Within‐season variations in the locations of maximum occurrence of polar air systems are consistent with the large‐scale changes in the longwaves associated with the semi‐annual oscillation of surface pressures. Interannual variations in polar low occurrence for the seven winters appear connected, at least in part, with changes in the amplitude of sea‐level pressure (SLP) wavenumber one. When the seasonal cycle is amplified, as in the year of a ‘warm’ ENSO (El Nino/Southern Oscillation) event (e.g. 1982), large numbers of polar lows are observed south‐east of Australia and around New Zealand. This contrasts with the situation for year (−1) of a warm event (e.g. 1981), when the annual cycle of the trough is suppressed. At that time, reduced frequencies of cold air outbreaks in the New Zealand area are accompanied by fewer polar lows.On a seasonally averaged basis, and in most winters, there is a positive relationship between the regional extent of the Antarctic sea ice, the longitudes of preferred occurrence of cold air outbreaks and the incidence of polar lows. This effect may be enhanced just downstream of areas of strongest oceanic heat loss to the atmosphere.
A quasi‐biennial oscillation in the intensity of the intra‐seasonal oscillation
Authors: Kuma Ken‐Ichi 
Published: February 2007

AbstractThe interannual and annual variations in the intra‐seasonal oscillation (ISO) are examined using upper air radiosonde data at Singapore. Spectral analysis of the zonal wind using the maximum entropy method (MEM) was made for each season, starting from the autumn of 1960 through to 1985. It is shown that the strongest signal of the ISO occurs during the Northern Hemisphere winter, while the weakest occurs in the Northern Hemisphere summer.The main finding of this study is a quasi‐biennial oscillation (QBO) in the intensity of the ISO. The cross‐spectral analyses indicate that the intensity of the ISO at 150 mbar is well correlated for a time‐scale of 2–3 years with the stratospheric QBO as well as with the strength of the zonal wind and the static stability of the upper troposphere.These results suggest that the stratospheric QBO may act as a trigger for the tropospheric QBO. The physical interpretation of this interaction requires further work, especially in the field of numerical modelling.
Four‐dimensional empirical orthogonal analysis of climate variables
Authors: Weare Bryan C. 
Published: February 2007

AbstractAn empirical orthogonal analysis method for analysing four‐dimensional geophysical data is derived. The potential utility of this method is illustrated in a sample analysis of the latent heating rates generated by the UCLA atmospheric general circulation climate model. In this example the four dominant eigenfunctions, which explain more than 64% of the total variance, are illustrated. The results show vertical structures, spatial patterns, and time variations that are consistent with a previous diagnosis of the UCLA model heating rates and observed climatology. Possible limitations of this methodology are discussed.
Caribbean tropical storm activity over the past four centuries
Authors: Reading Alison J. 
Published: February 2007

AbstractThis paper examines the frequency and distribution of tropical cyclones and hurricanes throughout the Caribbean using data derived from written accounts, chronologies, and published charts. Problems of incomplete and inaccurate data are overcome by conducting two levels of analysis; a 5° grid square analysis for modern charted data (after 1871) and a subregional analysis for data stretching back to the late fifteenth century. Significant variations in favoured tracks and levels of cyclone activity are identified for the charted and pre‐charted period. High levels of cyclone activity are suggested for the whole or part of the Caribbean during the 1770s to 1780s, 1810s and 1930s to 1950s while troughs in activity are noted around the 1650s, 1740s, 1860s and during the early twentieth century. A noticeable drift eastward in favoured tracks is reported from the mid‐twentieth century onwards, while data available so far this decade suggests a strong midlatitude (15–25 °N) preference by cyclones and hurricanes.
Lengths of very warm and very cold spells at Edgbaston
Authors: Jolliffe I. T. 
Published: February 2007

AbstractIn a recent paper, Hamilton examined the distribution of very warm spells and very cold spells at Edgbaston, Birmingham, during the period 1920–1979. The present paper takes the analysis of these data further by modelling them with a simple statistical distribution, namely the geometric distribution. It is shown that this distribution provides a good fit to the lengths of both warm and cold spells, although there is clear seasonal variation in the mean of the distribution.
THERMAL PATTERNS OF PACIFIC SOUTH AMERICA ASSOCIATED WITH EL NIÑTO/SOUTHERN OSCILLATION
Authors: Walsh Kevin J. , Cerveny Randall S. 
Published: February 2007

AbstractThis study quantifies the magnitude of temperature anomalies associated with extremes of the Southern Oscillation (SO) for 12 long‐record stations and five shorter‐record stations along the west coast of South America. Analysis of t‐tests indicates that nine stations north of 35°S have a strong inverse relationship between their mean annual temperature and the sign of the Tahiti–Darwin Southern Oscillation Index (SOI). Significant inverse relationships are determined between the phase of the Southern Oscillation and (i) summer temperatures (five stations), (ii) autumn temperatures (eight stations), (iii) winter temperatures (eight stations), and (iv) spring temperatures (four stations) for the region north of 35°S. In particular, the northern mid‐latitude stations (18°S–33°S) along the‐west coast of South America show a pronounced seasonal pattern in temperature differences between extremes in the SO. The summer temperature increases associated with negative SOI values may be due to warm air advection from the equatorial regions. The increase in winter temperatures may be caused by warm air advection from the mid‐latitudes associated with greater zonal flow caused by weakening of the South Pacific subtropical high. Stations south of 35°S display little temperature contrast between extremes of the SO.
The Greek heatwaves of 1987 and 1988
Authors: Giles Brian D , Balafoutis Christos J 
Published: February 2007

AbstractHeatwaves, which occurred in both July 1987 and July 1988 in Greece, are considered from the point of view of human discomfort. Hourly values of dry bulb temperature and relative humidity at Thessaloniki, Larissa, and Athens were used to define various limits of discomfort defined by Terjung, Herrington, Thom, and Tromp. On both occasions the heatwave was most severe in Thessaloniki, although both Greek and British press reports concentrated on morbidity and mortality in Athens. Finally, the synoptic situation at the time of each episode is briefly described.
Changes in the surface temperature of the dead sea and its heat storage
Authors: Stanhill G. 
Published: February 2007

AbstractTwenty‐seven thermal survey cruises made over 4 years, and 1 year of remotely sensed surface temperatures were used to examine areal, diurnal, seasonal and interannual changes in the temperature of the Dead Sea and in its heat storage.The satellite data, corrected for a cold bias attributed to the anomalous depth and turbidity of the Dead Sea's atmosphere, indicate a very small areal variation in sea‐surface temperature (SST), typically less than 0·3°C over two‐thirds of the sea surface. The maximum value measured, 4·5°C, was at night in mid‐winter. Below‐surface temperatures showed much larger areal variations caused by the shallower thermocline in the north of the sea. This variability was the reason for the large number of measurements required to assess accurately seasonal changes in heat storage.Diurnal variations in SST were at their maximum, 3°C, in May, and at their minimum, 0·3°C, in December. During the summer, diurnal differences were clearly evident at a depth of 5 m, with some evidence that a layer twice as deep could be affected.Seasonal variation in SST was not symmetrical. From mid‐March to early July, surface temperature increased uniformly at 0·10°C day−1, between mid‐September and mid‐November the cooling rate, 0·13°C day−1, was also constant. In January and February, and July and August, SST was almost constant, with day‐to‐day changes less than 0·01°C. The seasonal amplitude in SST was 11·5°C at the surface, 9·6°C at 25 m depth, halved at 35 m, and was reduced to one‐tenth, 1·4°C, at 50 and 75 m.No significant interannual changes in surface temperature were found since the mid‐winter rise of 3·4°C that occurred 30 years ago. During the last decade the maximum seasonal depth of the thermocline has progressively deepened to 30 m. and below this depth an increase in the temperature of the deeper waters is evident. Possible sources of this heating are discussed.Seasonal changes in the heat storage were in phase with those in the surface temperature, with maximum values of 9·1 MJ m−2 day−1 in June and –8·7 MJ m−2 day −1 in December. The heat budget (intra‐annual range) of the Dead Sea. 1.16 GJ m2, is one of the highest reported in the literature, although less than that expected from its depth and radiation balance. The sea's heat content increased by an average of 224 MJ m−2 year−1 during the 4 years of this study; the large year‐to‐year variation in this heating was negatively correlated with the fall in sea level.
A theoretically derived distribution for annual rainfall totals
Authors: Revfeim K. J. A. 
Published: February 2007

AbstractRainfall occurs as synoptic events, and in many climates annual totals are made up of a moderate to large number of events of varying amounts. Assumption of an underlying Poisson process of event occurrence leads to a simple statistical density, in terms of physically meaningful parameters, for the fourth root of annual totals. Analysis of data for four locations gives estimates of event‐recurrence rates in agreement with the number of rain‐days in the local climates.
Basis for prediction of the sharp reversal of climate from autumn to winter 1988–1989
Authors: Namias Jerome 
Published: February 2007

AbstractA major reversal in the pattern of temperature anomalies occurred over the contiguous United States of America between autumn of 1988 and winter 1988–1989, a climatic break which reflected a change in phase of the prevailing midtropospheric wind pattern over much of the Western Hemisphere. This transformation is described and attributed to forcing by remote and persistent circulations acting in concert with seasonal forcing. Practically all conventional forecast tools, especially those involving local persistence and climatic contingencies, failed to predict the break. However, the instability of autumn's and November's flow pattern was indicated by: (i) conserving the standardized November height anomalies into winter; (ii) testing the stability of this new hypothetical pattern with the help of statistically derived teleconnections; (iii) applying a modified mean barotropic model to the hypothetical chart; and (iv) extrapolating the winter pattern from trends of circulation within the autumn months. Making use of all this material, a forecast was made for winter at the end of November that turned out highly successful despite the failure of persistence between seasons.