bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intracellular proteolytic activity of the haloalkaliphilic archaeon Natronococcus occultus. Effect of starvation
Authors: Seitz Karina Herrera , Studdert Claudia , Sanchez Jorge , de Castro Rosana 
Published: February 2007

AbstractIntracellular proteolytic activity was detected in the haloalkaliphilic archaeon Natronococcus occultus during the stationary phase of cultures grown in complete medium and during carbon and nitrogen starvation. Puromycin prevented the occurrence of proteolytic activity in starved cells, suggesting that de novo synthesis of proteolytic enzymes might be required for protein degradation during starvation. Intracellular proteolytic activity degraded casein and gelatin. It had a temperature optimum of 60 °C in 2 M NaCl and depended on high salt concentration (NaCl or KCl) for activity and stability. Gelatin zymography of cell extracts from stationary phase or starved cells showed a complex pattern of proteolytic bands ranging from ∼ 20 to 120 kDa. All these proteolytic bands were inhibited by PMSF1) and chymostatin. However, they showed differences in stability to temperature and salt concentration.
The start of the rains in West Africa
Authors: Stern R. D. , Dennett M. D. , Garbutt D. J. 
Published: February 2007

AbstractThe start of the rains is defined as the first occurrence of a specified amount of rain within two successive days. The probability distribution of the date of the start of the rains is derived from the rainfall models of Stern (1980a). The probabilities of occurrence of dry spells are used to define an earliest practical starting date. Results are presented for eleven stations on a N‐S transect in West Africa. The variation in starting date with latitude is described. Advantages of the model approach over conventional analyses are discussed.
Correlations between the tropical atlantic trade winds and precipitation in northeastern Brazil
Authors: Chung James C. 
Published: February 2007

AbstractSurface wind and sea surface temperature data for the tropical Atlantic Ocean for the period 1911‐1972 are analysed in relation to the precipitation at Quixeramobim, Ceará in northeastern (NE) Brazil. Stratified correlations between the March‐April‐May Quixeramobim rainfall and the December, January, February, and March values of SST, and u‐ and v‐components of surface wind are presented for the tropical Atlantic. The implications of the correlations are that the months preceding an abnormally dry rainy season in NE Brazil are characterized by a strengthened South Atlantic trade flow and a North Atlantic circulation slightly weaker than normal. Cold SST anomalies are found in the South Atlantic and warm anomalies in the North Atlantic, suggesting a wind‐induced change in surface mixing or in evaporation from the surface. The divergence over the South Atlantic is seen to be stronger and more extensive preceding a dry season, and the equatorial convergence appears to be compressed northward and also strengthened. This northward compression is concluded to be responsible for the lack of rainfall in Ceará.
On the intra‐annual variation in rainfall over the sub‐continent of southern Africa
Authors: Dyer T. G. J. 
Published: February 2007

AbstractThe variation in intra‐annual variance in rainfall over Southern Africa is examined for evidence to support the contention that it has undergone a systematic upward change over the period 1921‐1974. A principal components analysis on the data shows that the time series of intra‐annual variances may be represented by four components. Although each of the four principal component time series possesses an oscillation in the region of the biennial wave, there is little evidence to suggest that the within‐year variation in rainfall is undergoing any type of upward trend.
A study of the influence of surface albedo on July circulation in semi‐arid regions using the glas GCM
Authors: Sud Y. C. , Fennessy M. 
Published: February 2007

AbstractA numerical simulation study of the influence of surface albedo on July circulation in semi‐arid regions, using the general circulation model (GCM) of the Goddard Laboratory of Atmospheric Sciences (GLAS) is presented. The results are based on two 47‐day integrations. In the first integration, called the control run, the surface albedo was normally prescribed, whereas in the second integration, called the anomaly run, the surface albedo was modified in four regions: the Sahel in Africa, the western Great Plains in the United States, the Thar Desert border in the Indian subcontinent, and northeast Brazil in South America. This experiment is similar to that of Charneyet al.(1977); however, it was performed with the GLAS model with vastly different boundary forcings and several changes in the physical parameterizations.Each run was started from observed initial conditions for 15 June 1979, based on NMC analysis. An analysis of the two simulations shows that in the Sahel, and the Thar Desert border regions the current results again show reduced precipitation with increased surface albedo in accordance with Charneyet al.(1977) and Charney (1975). The semi‐arid northeast Brazil region, which had a winter circulation, also conforms with Charney's (1975) hypothesis. However, the Great Plains region was an exception. There the total precipitation in two simulations was unchanged, as was the total cloudiness. In this region, the convective precipitation was reduced somewhat, while the large‐scale precipitation compensated this decrease by approximately the same amount. The lack of albedo impact on precipitation in the Great Plains region could be due to the influence of the Rocky Mountains in generating variations in the large‐scale flow.The purpose of repeating Charney's albedo experiment was to test the sensitivity of his earlier results with the current GLAS GCM which has substantially modified physical parameterizations, particularly the planetary boundary layer (PBL), crucially important for such impact studies. Taking into account that both the GCM and the initial conditions of the atmosphere were different, it is worth noting that this experiment still provides support for Charney's hypothesis (1975) regarding the influence of surface albedo on mean‐monthly climatology in the subtropical desert margin regions.Another important influence noted was the variability of mean monthly simulation in areas far away from the albedo anomaly regions. Because the differences occur in regions of high observed climatological variability, it is necessary to separate the contribution of albedo anomalies as opposed to the model variability. The influence of surface albedo changes to produce large changes in the mean montly circulation elsewhere is very intriguing and needs further investigation.
Protection from cold stress in a Eucalyptus shelterwood
Authors: Nunez M. , Sander D. 
Published: February 2007

AbstractNocturnal measurements of air, temperature and longwave radiation were taken in a Eucalyptus delegatensis shelterwood and in a clearfelled control site. On average the shelterwood exhibited temperatures between 1°C and 2°C warmer. Longwave radiation correlated well with percentage sky view as determined from fish eye lens photographs. The shelterwood seems to decrease the radiation loss by an average figure of 21 per cent on a cloudless night. The Brunt cooling theory is used to relate the air temperature and radiation figures.
Zonal index and circulation change in the north Atlantic area, 1873–1972
Authors: Makrogiannis T. J. , Bloutsos A. A. , Giles B. D. 
Published: February 2007

AbstractMonthly and annual values are calculated of a zonal index based on surface pressure at 35°N and 55°N between 60°W and 10°W. The period under study, 1873‐1972, is divided into three sub‐periods which approximate with three epochs proposed by Lamb (1972). A comparison of our indices with Lamb's results is followed by a discussion of our monthly index, and the rarity of easterly flow in the 100‐year period is noted. The results are subjected to a trend and a power spectrum analysis and the latter indicates a number of periodicities some of which are not easily explicable.
Associations among the tropical pacific wind and sea surface temperature fields and higher latitude circulation
Authors: Harnack Robert P. , Lanzante John R. , Harnack Jeremi 
Published: February 2007

AbstractAn empirical study was conducted examining associations between seasonal trade wind and sea surface temperature (SST) fields in the eastern half of the tropical Pacific Ocean for the period 1949‐1979. In addition, the tropical fields were statistically related to the extratropical circulation of the Northern Hemisphere (i.e. 700 mb heights). This study differs from most prior studies in that the trade wind field was examined primarily in terms of the horizontal trade wind divergence and seasonally stratified lag relationships were computed.Seasonally stratified autocorrelations of empirical orthogonal function (EOF) amplitudes (out to four seasons) indicated significant persistence of EOF1 of SST and divergence until spring‐summer for any initial season; accordingly, spring and summer (summer and autumn) EOF1 for SST (divergence) exhibited the greatest persistence. For divergence some tendency for a reversal of sign was seen from the autumn, winter, or spring seasons to the following autumn, which may imply negative air‐sea feedback mechanisms operating.Seasonally stratified cross correlations betwen the first EOF for SST and divergence indicated a significant contemporaneous relationship. When divergence leads SST, the relationship is significant at short lags (1‐3 seasons) until spring as a target season is reached. The same is true when SST leads divergence except that a significant relationship returns with opposite sign in the subsequent summer and auiumn. Winter SST and divergence, in particular, are well correlated with prior values of the other parameter.When the tropical parameters were related to the extratropical circulation through correlation with gridded 700 mb heights, significant patterns were found only when winter 700 mb heights were the target parameter (i.e. tropical parameter leading winter 700 mb heights). Summer through winter tropical SST and divergence (EOF1) displays a good association with subsequent winter extratropical circulation in the form of an expanded/contracted circumpolar vortex. The relationship between trade wind divergence and subsequent winter circulation is significant using the prior winter (4 season lag), vanishes during spring, and returns with the opposite sign for summer through winter (lags 0‐2). Using either SST or divergence, the observed relationships are stronger at lags 1 and 2 than at lag 0.
Fluctuations in northeast monsoon rainfall of Tamil Nadu
Authors: Dhar O. N. , Rakhecha P. R. , Kulkarni A. K. 
Published: February 2007

AbstractThe average rainfall series of Tamil Nadu for the northeast monsoon months of October to December and the season as a whole were analysed for trends, periodicities and variability using standard statistical methods. The trend analysis showed that there are no long‐term trends of increasing or decreasing rainfall in the individual months or the season as a whole. The power spectrum analysis of rainfall series showed peaks at frequencies corresponding to the time periods of 2 to 2–44 years and 3–66 to 4–40 years.
The use of average annual rainfall to derive estimates of orographic enhancement of frontal rain over England and Wales for different wind directions
Authors: Hill Frank F. 
Published: February 2007

AbstractA field of average annual enhancement, defined as the mean rainfall rate al inland sites minus the mean rate over the coast, has been derived for England and Wales. Past cases of frontal rain associated with low‐level winds from the SW quadrant were analysed so as to determine the typical distribution and intensity of orographic enhancement. It is shown that these results are sensitive to wind speed and, in particular, direction. Comparison of these results suggest relationships between orographic enhancement and average annual enhancement which are used to produce estimates of the distribution of enhancement which may occur with low‐level winds from other directions. These enhancement fields can he combined with radar observations of rain over the sea to produce short‐period forecasts of rainfall intensity when it moves overland.
Distinguishing signal and noise in climatological spectra
Authors: Gray B. M. 
Published: February 2007

AbstractA simple statistical test is proposed for matching the peaks occurring in two spectra, and an application to rainfall data is described. By comparing the spectra of related variables, small peaks in the rainfall spectra are shown lo contain information. However regularities in the occurrence of minima and maxima in climatological spectra can be explained by non‐linearities in the noise portion of the input data.
The dynamic climatology of the beaufort to Laptev sea sector of the polar basin for the summers of 1975 and 1976
Authors: Ledrew Ellsworth F. 
Published: February 2007

AbstractFor the summer months of 1975 and 1976, the total vertical velocity at 850 millibars is computed from a diagnostic atmospheric model as an index of synoptic activity in the Beaufort to Laptev Sea sector of the Polar Basin. The objective is to identify the major modes of synoptic activity in the region and to determine the major formative mechanisms for significant synoptic vortices. This will lead to an understanding of the dynamics involved in the evolution and maintenance of synoptic patterns in the Arctic.Cluster analysis is used to stratify the 850 mb geopotential height data into synoptic modes. The mean 850 mb total vertical velocity field for each cluster is calculated, and indices related to each of the formative mechanisms are related to these individual fields through regression analysis and pattern comparison. These mechanisms are: vorticity and thickness advection, diabatic effects of latent heat release and surface heating, and frictional and orographic influences at the surface. Explanations for the dynamics of the major regional vortices are discussed.
On the correlation between monthly and annual mean temperatures
Authors: Sawyer J. S. 
Published: February 2007

AbstractExcept for winter months, correlation between monthly and annual mean temperatures in Central England is, higher than would be expected if all monthly mean temperatures were uncorrelated. The correlation is increased if decadal means are taken, indicating an association of monthly temperature with some factor persisting over a decade or more. This correlation is not reduced if the association of the monthly mean temperature with the monthly mean pressure field is removed. It is suggested that there must be important factors causing climatic fluctuations in England which are not closely associated with changes in the frequency of synoptic types and which do not operate in winter.
African mean wind changes between sahelian wet and dry periods
Authors: Newell Reginald E. , Kidson John W. 
Published: February 2007

AbstractAfrican free air wind velocity data for wet and dry periods in the Sahel have been analysed objectively by the Cressman scheme and show that the lower troposphere easterly jet over west Africa is stronger in the dry period whereas the analogous easterly jet to the south of the equator exhibits greater vertical shear in the wet period. Two possible explanations, based on modulations of the meridional temperature gradients across the jet, are offered.
A criterion for defining transitional zones between humid continental and mediterranean climates in the region of Greece
Authors: Kotinis‐Zambakas S. R. , Angouridakis Vi. E. , Zambakas J. D. 
Published: February 2007

AbstractThe annual march of the mean monthly number of thunderstorm days at a station shows certain characteristics, depending on the prevailing climate. For example, the main maxima in continental and marine climates occur in summer and in autumn to winter, respectively. A gradation of such an annual march of thunderstorm activity is successfully used in delineating transitional climatic zones in Greece, and it might also be applied to other regions of the earth.
Summer energy budget simulation for A latitudinal transect along the east coast of the Americas
Authors: Terjung Werner H. , O'Rourke Patricia A. 
Published: February 2007

AbstractThe physically‐based model BUDGET combined a solar radiation transmission model and a steady state slope energy budget model. Climatic observations, averaged for 10‐degree latitude bands, were used as input in order to systematically examine the changing energy budget components (net radiation, conduction, sensible, and latent heat flux) occurring at the various slope angles (0 to 90°) and directions (south‐, west‐, and north‐facing). Two contrasting landscapes were examined (barren and grassy) along a latitudinal transect of the east coast of the Americas (northern hemisphere). The response of energy budget components was systematic and orderly on a latitudinal basis. However, a great diversity among energy budgets between different slopes and their orientation at a particular latitude was characteristic and more pronounced in the higher latitudes. These findings were assumed to be general enough to encompass most of the possible contrasts encountered in a real‐world north‐south transect.
The annual and seasonal distribution of fronts over central‐southern Europe and the Mediterranean
Authors: Flocas A. A. 
Published: February 2007

AbstractAn analysis of the frequency of occurrence of fronts over central‐southern Europe and the Mediterranean was carried out based on daily synoptic charts for the nine year period from 1971 to 1979. Tables and charts are presented showing the annual and seasonal frontal frequencies over the area, and the variation of average frequency of fronts with latitude and longitude is demonstrated. The distribution of the frequency of fronts fits in with generally accepted models of hemisphere circulation. An interesting feature is the relative importance of each type of front to the seasonal patterns which emerge. Cold fronts contribute strongly in all seasons with frequencies of approximately 1 in every 10 days in spring, summer and autumn and of 1 each week in winter.
Northern Hemisphere extratropical cyclone activity for four mid‐season months
Authors: Whittaker L. M. , Horn L. H. 
Published: February 2007

AbstractCyclone frequency, cyclogenesis and the primary and secondary tracks followed by extratropical cyclones within the Northern Hemisphere are examined for the four mid‐season months: January, April, July and October. The data for these four months were compiled from several sources for the period 1958–1977. Cyclogenesis was defined as the point of origin of a cyclone provided it maintained a closed isobar for 24 hours. Cyclone frequency was determined from the number of occurrences of an extratropical cyclone passing through a 5° latitude‐longitude grid box. Analyses of the grid values of cyclone frequency reveal relative maxima which define the cyclone tracks. The tracks are partitioned into primary and secondary tracks depending on the size of the relative maxima of cyclone frequency.Cyclogenesis is concentrated in the lee of major mountain ranges and along the east coasts of Asia and North America, with cyclogenesis in coastal North America found nearer the coastline than in the Asian area. A major cyclogenetic region also exists in the Gulf of Genoa‐Northern Italy region of the Mediterranean Sea, but here cyclogenesis is confined to the cooler seasons. As expected the areas of most frequent cyclogenesis shift poleward during the warmer months. Similarly, cyclone frequency exhibits a poleward displacement during the warmer months. It is also noted that whereas winter (January) is characterized by a significantly greater cyclone frequency over the ocean than over land, summer (July) finds the frequency over the continent about as large as over the oceans. Similarly there are significant poleward displacements of cyclone tracks in summer, but the displacement is in no way uniform over the hemisphere. These results can be compared with earlier hemispheric studies of cyclone activity.
On the cause of ‘fram’ type seasonal change in diurnal amplitude of air temperature in polar regions
Authors: Ohmura Atsumu 
Published: February 2007

AbstractThe cause of Fram' type seasonal trend of diurnal amplitude of air temperature is investigated from the viewpoint of the surface energy balance. First, the cause of diurnal amplitude of the surface temperature is examined. Then, the effect of the atmosphere between the surface and the screen‐level on the amplitude of air temperature is evaluated.The data of the energy balance used in this work were collected at the base camp of the Axel Heiberg Island Expedition (79°25′N, 90°45′W, 200 m) in the Queen Elizabeth Islands, N.W.T., Canada. This site shows a typical ‘Fram’ type trend of diurnal amplitude with annual maximum in April, the summer minimum in June and a secondary peak in August.The April maximum is due to extremely slow sublimation and heat conduclion in the subsurface. The decrease in the amplitude during the later dry snow period in May and early June is due to a gradual increase in sublimation which is induced by the temperature increase. During the melt in June, the diurnal amplitude of the surface temperature is effectively reduced owing to the diurnal change of the latent heat of fusion. After the snow melt, the diurnal amplitude of absorbed global radiation is tripled compared with April. The temperature amplitude remains small, however, owing to the rapid increase in the diurnal amplitudes of energy sinks. The cause of the slight recovery of the diurnal temperature amplitude in August is the decrease in the sensible heat flux.Throughout the entire period, the result of the heat exchange is reflected in a larger temperature variation under lower temperature due to the Stefan‐Boltzmann law. This effect contributes to a larger diurnal amplitude in spring.
Autoregressive modelling of the tropical stratospheric quasi‐biennial oscillation
Authors: Koscielny Albert J. , Duchon Claude E. 
Published: February 2007

AbstractAutoregressive time series models are used to make forecasts of stratospheric zonal wind and temperature at Kwajalein Island near the equator in the northern Pacific Ocean. The tropical stratosphere is dominated by the quasi‐biennial oscillation (QBO). Because the QBO has a varying period, an autoregressive model is more appropriate than a mixture of sinusoids. The data for 11 levels are efficiently represented by principal components, and univariate and multivariate autoregression models are fitted to six of the principal components. The autoregressive models are used for estimation of variance density spectra and for forecasting. The multivariate model is found to perform better in both detecting and forecasting the quasi‐biennial oscillation than either univariate models of the principal components or autoregressive models of the data set itself.