bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seasonal and regional 300 hpa heights, 300–1000 hpa thicknesses and associated 300 hPa zonal flow changes in the northern hemisphere between 1976 and 1990
Authors: Weber Gerd Rainer 
Published: February 2007

AbstractUsing monthly 300 hPa height and 300–1000 hPa thickness data published by the synoptic climatology group of the Free University of Berlin, height and associated zonal flow changes were analysed for the period 1976 through to 1990. The 300 hPa heights rose most notably in the tropics, somewhat less in the lower mid‐latitudes, and they were lower in high latitudes. Via the height gradient, an increase in the zonal flow at 300 hPa can be derived for the subtropics and in upper mid‐latitudes. Using correlation analysis, relationships between tropospheric thickness anomalies in the lower latitudes—where the bulk of the most recent tropospheric warming has occurred—and changes in the 300 hPa height field elsewhere are explored. It is found that warm (cold) anomalies in the tropical troposphere are related to 300 hPa gradient increases (decreases) in the subtropics, but to gradient decreases (increases) in mid‐latitudes. Gradient increases in the mid‐latitudes moreover are generally related more closely to high‐latitude cool anomalies than to lower mid‐latitude warm anomalies or low‐latitude cool anomalies.
Orthogonal rotation of complex principal components
Authors: Bloomfield Peter , Davis Jerry M. 
Published: February 2007

AbstractComplex principal components analysis has been shown to be a useful tool for exhibiting propagating features in spatial‐temporal data sets. As in other applications of principal components analysis, rotation may lead to more interpretable components. Real orthogonal matrices have been used elsewhere, in combination with the varimax criterion, to find rotated solutions, but these fail to show invariance to complex scalings of the initial eigenvectors. It is shown that complex orthogonal, or unitary matrices have the desired invariance, and their use is illustrated on two examples, one synthetic and one involving sea‐level pressure data.
Climate anomalies north of 55 °N associated with tropical climate extremes
Authors: Klaßen Joachim , Hense Andreas , Römer Ulrich 
Published: February 2007

AbstractThe relationship between extremes in tropical climate phenomena, e.g. ENSO and Indian summer monsoon, and the lower tropospheric temperature north of 55 °N is examined. For this purpose we carry out a dynamic statistical analysis applied to the data set of monthly mean 500–1000 hPa thickness from January 1949 to December 1991 (German Weather Service (DWD) analyses). To test the null hypothesis of identical horizontal mean distributions of the polar temperature field in irrespective of the sign of extreme tropical episodes a multivariate significance test is performed and the level of recurrence is estimated. In order to improve the signal‐to‐noise ratio, the data are projected onto the eigenmodes of an advection‐diffusion model. Comparing composites of warm versus cold ENSO events, the model indicates a significant difference in the winter lower tropospheric temperature pattern in northern latitudes. This pattern contains a warmer lower troposphere over the northern North American continent in winter, corresponding to other studies. The multivariate analysis further shows that the Indian summer monsoons with deficient rainfall are preceded by a strong cold anomaly in the lower troposphere over the northern Asian continent early in the year, corresponding to the known hypothesis of Asian‐snow—monsoon coupling.
Variance contribution of luni‐solar and solar cycle signals in the St Lawrence and Nile river records
Authors: Curri Robert G. 
Published: February 2007

AbstractSpectrum analysis of the St Lawrence River and three Nile River hydrological records yields evidence for two peaks with periods near 19 and 11 years. For each series the wavetrains of the peaks are obtained by bandpass filters, summed, superimposed on trend‐like components in the raw data, and plotted against the raw data. The contribution of the two waves to total variance in the St Lawrence data is 42 per cent, whereas the mean contribution in the Nile records varies from 20 to 28 per cent. The waves are identified as the 18–6‐year luni‐solar Mn 10–11‐year solar cycle Sc signals in climate, which have also recently been reported in other variables such as precipitation (USA, UK, South Africa, India), tree‐ring chronologies (world‐wide), air temperature and air pressure (world‐wide), height of sea‐level (world‐wide), and sea‐surface temperature, as well as in economic variables such as American crop yield, European fish catches, dates of wine harvest, and other macro‐economic data (Currie, 1988; Currie et al., 1993). The polarity of the 19‐year St Lawrence wave changed phase 180° between epochs 1936–1 and 1954–7 (epochs are dates of maximum in tidal forcing), and this phenomenon is commonly found in the much longer Nile records, as well as in virtually all of the above mentioned climate parameters.
Summer‐season mesoscale cyclones in the bellingshausen‐weddell region of the antarctic and links with the synoptic‐scale environment
Authors: Turner John , Thomas Jeremy P. 
Published: February 2007

AbstractResults are presented from the first investigation into a summer‐season of mesoscale vortex activity in a large sector of the Antarctic coastal region. The study is based on an analysis of 3 months' meteorological satellite imagery collected at the British Research Station ‘Rothera’ on the Antarctic Peninsula. The study revealed the high frequency with which such systems occur, with 162 individual vortices being found during the period December 1983 to February 1984 inclusive. The preferred area for their development was in the latitude band 60–70°S over the marginal ice zone and ice‐free region of the eastern Bellingshausen Sea. A classification scheme for the vortices was developed based on the relationship with the broad‐scale synoptic flow, the sea ice, and the geographical location. The most common type of vortex found was the ‘classic’ polar low, which formed in the southerly flow to the west of synoptic‐scale disturbances. These vortices were very similar to the baroclinic type of polar lows observed south of Iceland during the Northern Hemisphere winter. A third of the vortices in total were found to be mesoscale features associated with synoptic‐scale troughs or the centres of major depressions. Vortices with comma‐shaped cloud signatures occurred about twice as frequently as those with spiraliform cloud. The vast majority of vortices had a diameter of less than 500 km, with very few systems being observed in the range 500–1000 km. Mean anomalies of 500 hPa geopotential height and surface pressure for the occasions when vortices were identified were —5.3 dm and — 0.5 hPa, respectively, indicating the association of these systems with upper air troughs and cold pools. Only 23 of the vortices found were correctly represented on the Meteorological Office analyses and of these 15 were small synoptic disturbances. The ‘polar low’ class of vortex was very poorly represented in the analyses, indicating that the available satellite sounder data could not resolve the systems and that the processes resulting in their formation were not handled well by forecast/data assimilation schemes. Comparison of the mean surface and 500 hPa height fields for this 3‐month period with the long‐term average data show that there were negative anomalies at both levels over the Bellingshausen Sea. The number of vortices over the Bellingshausen Sea in this summer period may have been greater than would be expected in an average year, but activity over the Weddell Sea was probably close to average.
Sunspot numbers as a possible indicator of annual rainfall at Addis Ababa, Ethiopia
Authors: Seleshi Yilma , Demarée G. R. , Delleur J. W. 
Published: February 2007

AbstractThe variability of the Sun's luminosity is thought to have effects on the world climate. This variability is partly measured by the sunspot numbers. In this paper the statistical link between sunspot numbers and Addis Ababa rainfall is established. For this purpose a transfer function plus noise model (TFN) is constructed, with Box‐Cox transformed annual sunspot numbers,Xvas input and annual Addis Ababa monsoon rainfall,Yvas output. This model explains 50·2 per cent of the annual rainfall variability in the period 1900–1990. The time series of the sunspot numbers is simulated by an autoregressive model and then used to provide the input forecasts to the TFN model; it explains 88·9 per cent of the annual sunspot numbers variability.The TFN model is utilized for long‐range annual rainfall forecasts. A check of the forecasting skill of the TFN model is performed by fitting the TFN model to the 1900–1970 data and forecasts are made for 1971–1991. The results show that 14 out of 21 forecasts generally track the observed rainfall. The correlation coefficientCbetween the forecast and observed rainfall is 0·58, whereas for the sunspot numbersCyields 0·87. The pairedt‐test shows that the forecasts and the observed rainfall are statistically similar at the 95 per cent confidence level.A general physical mechanism that may partly explain how the variability of the Sun's luminosity is related to the world climate is suggested. It is proposed that for those regions whose climatic variables exhibit the 11‐year periodicity, the TFN model approach can be used to find a statistical link between the sunspot numbers and the climatic variables. Furthermore if a global pattern in such a link is found, it may be used for exploring the physical mechanisms of Sun‐climate relationships.
Spatial variation of climatic aspects of temperature: Interdiurnal variability and lag
Authors: Driscol Dennis M. , Rice Peter B. , Fong Juan M. Yee 
Published: February 2007

AbstractTwo relatively neglected aspects of climatic temperature variability are mean interdiurnal temperature variability (MITV), and the lag of maximum and minimum temperature behind their respective solstices. After determining the length of record to attain stability for the former, and the dates (of the year) on which temperatures are a maximum and minimum, these parameters are mapped for North America. For MITV there is a general association with continentality and the location of the surface polar front zone; the lag patterns bear only a slight resemblance to continentality.
A Markov chain model for daily precipitation occurrence in South Korea
Authors: Moon Sung‐Euii , Ryoo Sang‐Boom , Kwon Jae‐Gi 
Published: February 2007

AbstractThe Markov chain properties of daily precipitation occurrence, namely, the dependency of the daily precipitation on that of the previous day, are studied based on the daily precipitation data for 30 years (1956–1985) at 14 stations in South Korea. The daily precipitation data at each station were classified into the wet and dry state, and transition probabilities between daily precipitation of two successive days were computed. Then the Markov chain properties and various aspects of daily precipitation occurrence from the Markov chain properties were investigated. The results are as follows: the transition probability of two successive wet days for 30 years at the 14 stations is 0.51, and the statistical tests show that the transitions of daily precipitation occurrence in South Korea can have the Markov chain property and be stationary in time, except at Ullung‐do, Seoul, Kangnung, and Mokpo, but heterogeneous in space. The n‐step Markov chain analysis shows that the ‘memory’ of the daily precipitation occurrences at 14 stations remains about 2–3 days. The weather cycle is 6.59 days.
Fluctuation of sunshine duration in central and South‐Eastern Europe
Authors: Brazdil R. , Flocas A. A. , Sahsamanoglou H. S. 
Published: February 2007

AbstractSunshine duration fluctuation in this century is studied from annual values for 26 stations in central and south‐eastern Europe. Possible sources of inhomogeneity are identified: ageing of the glass ball in the sunshine recorder, changes in instruments, the recording tape and its evaluation, and location of the station, and exposure to air pollution. Long‐term changes of annual sunshine duration are presented using a smoothed Gauss filter and principal component analysis. The main feature of sunshine duration fluctuation in this century is its sharp decrease after a maximum at the end of the 1940s. Principal component 1 shows, with small exceptions, positive loadings for the year and its seasons (for the period of 1931–1985). Principal component 2 divides the region studied into two parts, with positive loadings in the western and northern parts of central Europe and negative loadings over the rest of area analysed. A contradictory situation occurs only in autumn. Statistically significant cycles occur at intervals of about 2.3–2.4 years (western Germany), 3 years (Greece), 3.5–3.7 years (central Europe and Bucharest) and 3.7–4.0 years (Bulgaria). Some of the stations used indicate longer cycles (44–110 years). Comparison of coldest (1901–1920) and warmest (1934–1953) 20–year periods in the Northern Hemisphere shows for the warmest period an important increase in sunshine duration, with the exception of Athens and Bucharest and some other stations in winter. In the warmer period sunshine duration variability is generally higher in spring and winter and less in summer and autumn.
The air temperature in cracow from 1826 to 1990: Persistence, fluctuations and the urban effect
Authors: Kożuchowski Krzysztof , Trepińaska Janina , Wibig Joanna 
Published: February 2007

AbstractMean monthly air temperatures in Cracow for the period 1826–1990 were used. The temperatures of the coldest (Tlow) the warmest (Thigh) periods of the year, and mean annual temperatures (Ta), were calculated. The persistence of temperatures was examined using the correlation coefficients between monthly temperatures in succeeding months. A significant temperature persistence was found for a cold season (December‐March) and also for the summer (July‐August). Long‐term fluctuations were analysed by means of 20‐year and 30‐year running mean values and the positive and negative squared deviations of moving 20‐year subperiods. Two warm stages were found. One at the beginning of the present century, the second at the end of the period analysed. The first warm phase was connected with a decrease in the degree of continentality. Warm phases were also linked with a decrease in the temperature variability.The spectrum and the moving spectrum in 40‐year subperiods of monthly and annual temperature records were calculated. An 8‐year period was found in Tlow, Ta, and in the monthly series of the cold season, and 4‐ and 5‐year periods were found in Thigh and in the monthly series of the warm season.By comparing the temperature in Cracow with that at the neighbouring stations of Wieliczka, Bochnia, and Tarnów, it was found that the difference in annual means increased from −0.3°C at the end of the previous century to 1.0°C in the last two decades. About 0.5°C of this increase occurred in the last 40‐year period of abrupt expansion and industrialization of the city of Cracow.
Land‐surface characterization in greenhouse climate simulations
Authors: Henderson‐Sellers A. , McGuffie K. 
Published: February 2007

AbstractA simplified Holdridge‐type vegetation prediction scheme has been coupled to a version of the NCAR community climate model (CCM1‐Oz) that includes the biosphere‐atmosphere transfer scheme (BATS) and a mixed‐layer ocean. This interactive vegetation climate model has been used to conduct two complementary CO2‐doubling experiments: an instantaneous 2 x CO2 simulation (15 years in total) and a fast, transiently increasing CO2 simulation (45 years in total). There are some differences in the predicted vegetation distributions and areas. However, there is agreement that in a warmed world the vegetation type termed ‘agriculture’ increases in area at the expense of deciduous needle‐leaf trees and short grass; and the tundra extent, already underestimated, decreases further whereas deserts and the deciduous broadleaf tree areas expand. The overall vegetation areas predicted are not particularly sensitive to initialization, although effects of different initialization can be monitored for 1–2 years. On the other hand, when the sensitivity of the modelled climate to the inclusion of some aspects of an interactive biosphere is examined, it is found that annually updated continental characteristics do not disrupt the climate simulation but do modify zonal temperatures and precipitation and increase continental evaporation. The latter intensifies the Hadley circulation, especially in July, and, thus, leads to increased evaporation globally. These results, if corroborated by other similar studies, indicate that simple, post facto application of vegetation diagnostic schemes once climatic equilibrium is achieved may be diagnosing vegetation from an incorrect climatic state.
Can interannual variations in stratospheric ozone be observed in the marine environment?
Authors: Topliss B. J. 
Published: February 2007

AbstractThe possibility of interannual variations in water colour measurements, taken in UK waters, being influenced directly by ultraviolet (UV) light was investigated. Total column ozone was used as the indicator for UV light. A data base of 30–40 years of UK atmospheric and marine monthly data was assembled in order to investigate where in the environment the total column ozone signals may be observed. Principal component analyses were used first to remove regional and then to remove seasonal variations. Statistically significant correlations were obtained between a component of total column ozone, 300 hPa geopotential height, and water colour data. The relations between ozone, stratospheric temperature and wind speed and the 300 hPa geopotential height data were interpreted in terms of atmospheric disturbances modifying the position of the tropopause. No other atmospheric or climatic variable in the data base exhibited these ‘ozone‐weather’ signals, lending support to the hypothesis that this particular ozone signal could have found its way into the marine environment via direct exposure of marine life to UV in the surface layers of the ocean. After examining the data base for all support for and against this hypothesis, however, it was determined that the overall evidence was still ‘circumstantial’. Interannual variations in stratospheric ozone could be linked to variations in water colour data but no exclusive mechanism could be identified from statistical analyses alone.
Trends in wind and sea‐level pressure in the tropical pacific ocean for the period 1950–1979
Authors: Inoue Masamichi , Bigg Grant R. 
Published: February 2007

AbstractThe COADS (Comprehensive Ocean‐Atmosphere Data Set) sea‐level pressure observations over the tropical Pacific Ocean during the period 1950–1979 are examined to check for dynamical consistency between the observed trends in wind‐speed components and the trends in sea‐level pressure pattern. There appears to be some evidence that the South east Pacific High and the equatorial trough in the central Pacific were gaining strength. As a result, trade winds appear to have been gaining strength along the northern flank of the South east Pacific High and in the eastern/central equatorial Pacific. However, there were considerable variations in those trends from decade to decade. The patterns of those decadal changes in sea‐level pressure appear to be dynamically consistent with those of wind tendency. An example of a quantitative consistency check for a region located at 160°W–150°W and 10°S–20°S demonstrates that the observed strengthening trend in zonal wind component in the region appears to be dynamically consistent with the observed air‐pressure field measured by both ships and the nearby island stations. It also demonstrates clearly that the overall magnitudes of change in the two independently measured fields (ship‐observed winds and sea‐level pressure) over the 30‐year period are quantitatively of the right order. These observations at least suggest that the qualitative nature of the observed trends in the trade winds in the Pacific since 1950 is real.
Temperature variations in a tropical‐subtropical environment: Queensland, Australia, 1910–1987
Authors: Lough J. M. 
Published: February 2007

AbstractMinimum daily temperatures have increased significantly and the daily temperature range has decreased significantly in Queensland in both summer and winter over the period 1910–1987. Temperature variations in Queensland, particularly average and minimum temperatures, have largely paralleled those of the Australian region and Southern Hemisphere. Trends in minimum temperatures and the daily temperature range in Queensland cannot be attributed to urban warming. Effects of urban heat islands on temperature are, however, evident in some of the large coastal cities of the State. During the summer wet season, variations of the daily temperature range are controlled largely by variations of daily maximum temperatures. These are, in turn, linked to variations of rainfall, cloud amount and the Southern Oscillation. During the winter dry season, variations of the daily temperature range are controlled largely by variations of daily minimum temperatures. These are, in turn, associated closely with rainfall, cloud amount and sea‐surface temperatures (SSTs) in coastal waters. The recent rise in daily minimum temperatures and decrease in the daily temperature range in Queensland are not unprecedented in the 78‐year record. Variations of rainfall and SSTs in adjacent waters have generally acompanied the temperature changes.
Investigating impacts of anomalous land‐surface conditions on Australian climate with an advanced land‐surface model coupled with the BMRC GCM
Authors: Yang Z.‐L. 
Published: February 2007

AbstractA new and complex land‐surface model, the bare essentials of surface transfer (BEST), has been incorporated into the Australian Bureau of Meteorology Research Centre (BMRC) atmospheric general circulation model (GCM). A series of experiments with anomalous land‐surface conditions using the BEST‐GCM were conducted.Three sets of conditions were used for the winter, two of which were related to the soil moisture conditions. The soil over the entire Australian continent was saturated (hereafter WET) and dried (hereafter DRY) on the first time step of 4 July, and then allowed to evolve normally. In another experiment, values of all the 15 BEST parameters over the continent were set to those at a point in the Great Desert and kept unaltered throughout the integration period (hereafter DESERT). Two additional WET and DRY experiments were carried out for the summer, from 6 January for 60 days.The results of these experiments differ significantly from those conducted with bucket‐type land‐surface parameterization schemes in that:

WET or DRY anomalies evolve differently in specific regions. The geographical distributions of responses are more disorganized, possibly because of the inclusion of vegetation, which may enhance the regional features and the non‐linear treatment of soil moisture content and surface wetness.
Magnitude of responses are larger because of the greater number of feedback mechanisms. For example, when the feedback of soil moisture and surface albedo is allowed, the increase of soil moisture leads to an increase of evaporation. The increase of soil moisture results in a decrease in albedo which in turn leads to an increase of absorbed solar radiation available for evaporation.
Time‐scales of adjustment are different for DRY and WET anomalies. WET anomalies persist much longer, have stronger responses and are more organized than DRY anomalies.
The summer WET or DRY anomalies have larger responses than the corresponding winter anomalies.

These results are physically interpreted and their implication in seasonal precipitation forecasting is discussed.