bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimating continental and terrestrial precipitation averages from rain‐gauge networks
Authors: Willmott Cort J. , Robeson Scott M. , Feddema Johannes J. 
Published: February 2007

AbstractInfluences of varying rain‐gauge networks on continental and terrestrial precipitation averages (derived from data observed on those networks) are evaluated. Unsystematically and systematically designed station networks are considered, the latter being represented by the NCAR World Monthly Surface Station Climatology, which contains hand‐picked but time‐varying networks that date back to the 1800s. Biases arising from spatially uneven and temporally variable precipitation‐observing networks can be significant.For all the continents, except South America, sparse rain‐gauge networks produce overestimates of continental mean precipitation. Mean precipitation for South America, in contrast, is underestimated substantially by low densities of observing stations. Sampling errors tend to be large in areas of high precipitation and in regions with strong spatial precipitation gradients (e.g. in the Sahel). These patterns occur whether the station network has been selected systematically (as in the NCAR network) or unsystematically.Systematic sampling of mean precipitation (at the NCAR station locations), however, suggests that many yearly NCAR station networks are adequate for estimating continental average precipitation. As early as 1890, NCAR networks for Australia resolve continental average precipitation accurately. Not until 1960, however, do NCAR networks for South America begin to resolve continental mean precipitation adequately. Regional and continental NCAR network errors also tend to cancel one another, often giving accurate yearly estimates of terrestrial mean precipitation.
Validation of tropical ocean‐atmosphere heat fluxes‐from marine data against a satellite‐based method
Authors: Michael K. J. , Nunez M. , Meyers G. 
Published: February 2007

AbstractOcean‐atmosphere heat fluxes were calculated from marine weather reports over a mesoscale region of the Coral Sea near Townsville, Australia. These heat fluxes were compared, as 5‐week averages, with a set of heat fluxes derived over the same region from a combination of satellite and surface data. These satellite‐ and surface‐derived fluxes were calibrated and validated against accurate, independent surface heat fluxes, as described in a previous paper.Significant differences were noted between the two sets of heat fluxes. The discrepancies in the net solar radiation are attributed to insufficient marine weather reports and/or improper cloud parameterization in the formulae applied to the marine data. Some large differences were observed in the outgoing turbulent heat fluxes, and these were traced to higher water‐air specific humidity gradients in the marine data. These two discrepancies cancel so that the long‐term (45 week) averages of the total ocean‐atmosphere heat flux, at 52 W m−2 for the satellite‐based technique and 34 W m−2 for the shipboard method, differ by only 18 W m−2.On the basis of these systematic differences it was concluded that the heat fluxes derived from satellite and surface data in this study were superior in quality and reliability to heat fluxes calculated from marine weather reports. Further studies are required to test this result in other locations.
Prediction of the interannual variations of tropical cyclone movement over regions of the western north pacific
Authors: Chan Johnny C. L. 
Published: February 2007

AbstractThe interannual variability of tropical cyclone (TC) movement has been found to be rather significant in certain regions of the western North Pacific. Westward and northwestward moving TCs are found to occur mostly at low latitudes and have the largest interannual variations in the region just east of the Philippines and over the northern part of the South China Sea. The area east of the Ryukyu Islands and south of Japan is identified as having the largest interannual variation of northward moving TCs.Correlations are made between the annual number of occurrences of TCs in these prescribed regions and the principal components of the monthly mean 850‐ and 500‐hPa zonal wind patterns over the western North Pacific (for the months of November of the previous year to April of the current year). Westward‐moving cyclones are found to correlate well with the 850‐hPa zonal wind patterns in January and March. Using the principal components associated with these patterns, prediction equations are then developed using the total (dependent) sample and the jackknife method (simulating an independent sample). The predictions made with both the dependent and “independent” samples are found to be very good.For north‐westward moving cyclones, no prediction equation is developed because principal components of the 850‐ and 500‐hPa zonal winds found to be significant can explain less than 30 per cent only of the total variance. However, the February 500‐hPa zonal winds correlate well with northward‐moving cyclones in the region east of the Ryukyu Islands and south of Japan. Predictions made using the principal components associated with this flow pattern for both the dependent and “independent” samples give rather good results.Because all the predictors are between January and March, they can be used operationally to predict the annual number of occurrences of TCs in the predefined regions. As TCs in these regions are likely either to move into the South China Sea or affect Japan, these results should prove useful in the seasonal prediction of TC occurrence in these latter areas.
The effects of EL NIñO‐southern oscillation on precipitation in san josé, costa rica
Authors: Waylen Peter R. , Quesada Marvin E. , Caviedes César N. 
Published: February 2007

AbstractThe effects of interannual variations in El Niño‐Southern Oscillation (ENSO) upon annual, seasonal and monthly precipitation totals of San José, Costa Rica, over the period 1882–1987 are analysed using both a Southern Oscillation index (SOI) and a classification of El Niño and anti‐El Niño years. The analyses confirm the posited regional positive relationship between annual precipitation and the SOI and suggest that estimates of the probabilities of annual rainfall could be made successfully by using a mixed probability distribution that incorporates changes in both the mean and variance of precipitation under each of the three classes of El Niño activity. Strong seasonality is identified in the effects of ENSO, particularly in the months of July, August, and October, whereas the month of September seems unaffected. Monthly lead lag analyses imply that there may also be a reversal of the nature of association between the SOI and precipitation in the following year.
Climatic‐scale vegetation—cloud interactions during drought using satellite data
Authors: Carleton Andrew M. , Travis David , Arnold David , Brinegar Richard , Jelinski Dennis E. , Easterling David R. 
Published: February 2007

AbstractLand‐surface‐atmosphere interactions for the 1988 summer drought in the Mid‐west USA are studied at climatic scales (104 km2; >5 days) using polar orbiter satellite radiance information on vegetation activity and cloud conditions. The emphasis is on documenting the occurrences of ‘organized’ land‐cover types and cumulus convection, and evaluating their mutual associations. For purpose of comparison, similar analyses are performed for the more moisture sufficient (non‐drought) summer of 1987. The satellite retrievals and analysis methods are calibrated using station meteorological data on precipitation and surface moisture, and also land‐cover maps.In early summer (June) 1988, Mid‐west USA land surfaces were generally highly stressed (high shortwave reflectance, high surface temperatures), particularly for the Corn Belt. Moreover, the spatial variation of the land‐cover signal was greater than in June 1987, and also when compared with later that summer (August 1988). Statistical analysis suggests a significant role for the land surface conditions of early summer in the spatial patterns of deep convection over the remainder of the season. This involves generally higher (lower) frequencies of convective cloud days for surfaces having a high relative density of forest vegetation (crops). Because broadly similar results are obtained for the summer of 1987, the possibility exists that the vegetation‐convective‐cloud interaction may be a feature of Mid‐west USA summer climate.The diurnal dependence of cloud‐forming processes for agricultural and natural vegetation regions is assessed using GOES cloud imagery at high temporal resolution for a “typical” convective day in early summer 1988. Associations with station radiosonde data support the hypothesis that spatial differences in land cover influence the generation and timing of convective cloudiness for the Mid‐west region.
Measurements of albedo variation over natural vegetation in the sahel
Authors: Allen S. J. , Wallace J. S. , Gash J. H. C. , Sivakumar M. V. K. 
Published: February 2007

AbstractThis paper reports ground‐based measurements of albedo at two different sites in south‐western Niger: agricultural fallow at the ICRISAT Sahelian Center (ISC), Sadoré, and a type of open natural forest (tiger‐bush), 6 km south‐west of ISC. The vegetative cover at each site consisted of two clearly defined components, for which separate measurements were made. The four different component surfaces spanned the entire range of plant cover density normally occurring in the southern Sahel, ranging from zero (bare soil) to a dense, closed canopy of woody shrubs. Continuous automated observations of albedo were made over a period of 15 months, from July 1989 to September 1990, including both wet and dry seasons. The data are analysed on hourly, monthly, and annual time‐scales in order to demonstrate how albedo varies in response to the density of plant cover, soil‐surface moisture content, solar zenith angle, and the proportion of diffuse light in the incoming solar radiation. Large annual variation in monthly mean albedo was observed at both sites (increases from the wet to dry season of 0.065 and 0.057 for the fallow and tiger‐bush, respectively). At the fallow site the annual variation in albedo resulted mainly from the wet to dry season cycle of leaf growth and loss. At the tiger‐bush site the primary cause of annual variation in albedo was the frequent wetting of the extensive bare soil component that occurred during the rainy season. The significance of these results for global climate modelling is assessed briefly.
Long‐range prediction of hawaiian winter rainfall using canonical correlation analysis
Authors: Chu Pao‐Shin , He Yuxiang 
Published: February 2007

AbstractHawaiian rainfall is teleconnected to short‐term climate variability in the Pacific Ocean. The summer Southern Oscillation Index (SOI) and summer sea‐level pressure (SLP) over the North Pacific are used as predictors, and the following winter rainfall indices from three islands of Hawaii are used as predictands. To consolidate the large data array of the SLP field prior to prediction experiments, lagged correlation and empirical orthogonal function analyses are used.Canonical correlation analysis has been used for predicting Hawaiian winter rainfall. Among many schemes tested, predictions. Cross‐validation techniques have also been used to estimate the “overall” forecast skill of various schemes, and the results are consistent with those from prediction experiments. Winter rainfall in Hawaii can be predicted with a good degree of success two seasons in advance using the summer SOI and the first four eigenmodes of summer SLP over the North Pacific as predictors.
Linkage between eurasian winter snow cover and regional chinese summer rainfall
Authors: Yang Song , Xu Lizhang 
Published: February 2007

AbstractAn inverse relationship has been documented by previous studies between antecedent Eurasian winter snow cover (EWSC) and all‐India summer monsoon rainfall. Because both China and India are strongly influenced by the Asian monsoon system, it may be reasonable to ask whether a similar relationship exists between the EWSC and summer rainfall over China. This study seeks an answer to this question.Only a weak interannual relationship is found between the EWSC and summer rainfall over China as a whole. This weak EWSC‐rainfall linkage occurs only when the averaged rainfall over the entire country is used. By dividing the country into several geographical regions based on observed features in the interannual variability of rainfall, we find much stronger regional rainfall‐EWSC relationships. A strong in‐phase EWSC‐rainfall relationship is found in southern and northern China, whereas an inverse EWSC‐rainfall relationship appears in the western, central, and north‐eastern parts of China. Thus, EWSC may be a useful predictor for regional Chinese summer rainfall, but not for rainfall over the country as a whole.
Mesoclimatology of winter temperature and precipitation in the po valley of northern italy
Authors: Cacciamani Carlo , Nanni Sandro , Tibaldi Stefano 
Published: February 2007

AbstractAn attempt is made to characterize the mesoscale climatological structures of the daily maximum and minimum temperature anomalies (with respect to monthly climatology) and total daily precipitation of the Emilia Romagna region of northern Italy (essentially the Po Valley) by means of multivariate statistical analysis techniques. Firstly, a definition of homogeneous seasons is attempted, based on the analysis of the month‐to‐month variability of the temporal variance of the parameters, derived from 24 years of daily data (1961–1984). This definition is then adjusted following a monthly empirical orthogonal functions (EOF) analysis of the spatial structures of variability of the same fields. Having defined “seasons” in this way, attention is concentrated on the cold season, an “sextended winter” ranging from October‐November to March‐April. Empirical orthogonal functions of both temperature anomalies and precipitation parameters are then recomputed for this extended season. Separate cluster analyses of the low‐dimensionality subspaces defined by the first three EOF coefficients (the principal components, PC) of the two parameters reveals the existence of winter weather ‘regimes’. Projections of these ‘regimes’ on geopotential height‐fields analyses in the middle (500 hPa) and low (mean sea‐level pressure) troposphere are qualitatively consistent with synoptic knowledge of the typical ‘weather types’ (grosswetterlagen) of the Mediterranean area. A comparison between the cluster analyses of temperature and precipitation shows that mutually compatible thermal and pluviometric regimes can be defined, providing a unified description of the space‐time mesoscale variability of the observed parameters.
Spatial and temporal characteristics of maximum dry spells in Southern Norway
Authors: Perzyna Gregor 
Published: February 2007

AbstractThe paper deals with the spatial and temporal characteristics of summer maximum dry spells in south‐east Norway, and the influence they exert on river low flows. The analysis was conducted at two spatial scales: at a catchment scale of the order of tenths of kilometres, and at a regional scale of the order of hundreds of kilometres. At both scales, the spatial persistence of maximum dry spells differs distinctly between summer seasons. During ‘wet seasons’ the short dry spells are temporally spread, show no spatial trend, and drought conditions are suppressed. During ‘dry seasons’, the spatial timing of maximum dry spells tends to be uniform over the whole study area. At the catchment scale, however, prolonged, single‐season dry spells can be disturbed by convective rainfall events. The long‐term, statistical parameters of maximum dry‐spell periods showed stable and uniform spatial distribution over the study area. The mean of maximum dry‐spell periods and the coefficient of variation have been mapped regionally. The regional values of the parameters can be used as climatic input to stochastic low‐flow‐prediction models. It was shown that for Norwegian conditions the distribution function of maximum dry spells followed the extreme value type 1 distribution.
Urban albedo derived from direct measurements and landsat 4 TM satellite data
Authors: Soler M. R. , Ruiz C. 
Published: February 2007

AbstractThe main aim of this study is to examine the effect of urban structure on the albedo value. The urban area chosen for this study was Barcelona. On the basis of measurements made in July 1989, and without consideration of the urban structure, the albedo values of various urban structures was determined.Simultaneously, from analysis of Landsat 4 TM images, thus taking account of the urban effect, a method for the calculation of albedo was developed. These results are compared.
CLimatological characteristics of very low humidity in Northern Crete due to Downslope southerly winds
Authors: Prezerakos N. G. 
Published: February 2007

AbstractIn this paper an attempt is made to study the climatological characteristics of very low relative humidity (below or equal to 10 per cent) in northern Crete, especially at Heraklio, by utilizing data from a 34‐year period (1956–1989). Specifically, after selecting the very low humidity days based on a previously determined definition and the synoptic situation with which they are associated, the following aspects were examined: (i) the interannual and monthly variation, (ii) the mean duration of very low humidity occurrence on each day at Heraklio and its monthly frequency, (iii) the mean values of the meteorological elements (temperature, wind, wind gusts, pressure, total and low‐cloud amounts, and visibility) for the time of synoptic observations reporting very low humidity at Heraklio and for the corresponding times of the day gust before it for both Heraklio and Tibaki, that is, on the northern and southern coasts of Crete. Also by comparing Heraklio's and Tibaki's mean values of the meteorological elements it was possible to determine the contribution of the Cretan relief characteristics to the very low humidity occurrence at Heraklio.
Moisture condition in the South‐Eastern USA and teleconnection patterns
Authors: Yin Zhi‐Yong 
Published: February 2007

AbstractThe purpose of this study is to investigate the relationship between the moisture condition and teleconnection patterns including the Pacific‐North American (PNA) pattern, North Atlantic Oscillation (NAO), and the El Niño‐Southern Oscillation (ENSO). The February and August Palmer's Drought Severity Index (PDSI) was used to represent the moisture condition of the cold and warm seasons in the south‐eastern USA. The teleconnection patterns were represented by the indices of PNAI, NAOI, and SOI. Composite maps for extreme values of the teleconnection indices revealed that spatial variation in the moisture condition is associated with different phases of the teleconnection patterns. Correlation analysis indicated that the PNA, NAO, and ENSO are related mostly to the subregional moisture conditions. Principal component analysis defined subregions of homogeneous moisture regimes. Then regression analysis was performed on the scores of the principal components of the February and August PDSI, using the teleconnection indices as the independent variables. The area with its cold‐season moisture condition best explained by the teleconnection patterns is central and south Florida. The teleconnection indices also explained significant portions of the variation in the cold‐season moisture condition of Mississippi and Tennessee. The teleconnection patterns in the previous autumn probably can be used to predict the moisture condition in the following winter. Compared with the cold season, the summer teleconnection patterns are less strongly related to the warm‐season moisture condition. Nevertheless, the relationships between the moisture condition and the teleconnection patterns are significant statistically. In addition, the teleconnection patterns in the previous spring offered some explanations to the spatial patterns in the warm‐season moisture condition in the region.
Solar‐irradiance variations and regional precipitation fluctuations in the Western USA
Authors: Perr Charles A. 
Published: February 2007

AbstractChanges in total solar irradiance can be linked to changes in regional precipitation. A possible mechanism responsible for this linkage begins with the absorption of varying amounts of solar energy by the tropical oceans, which creates ocean temperature anomalies. These anomalies are then transported by major ocean currents to locations where the stored energy is released into the atmosphere, thereby altering atmospheric pressure and moisture patterns, which can ultimately affect regional precipitation.Correlation coefficients between annual differences in empirically modelled solar‐irradiance variations and annual State‐divisional precipitation in the USA for the period 1950–1988 were computed with lag times of 0 to 7 years. The most significant correlations occur in the Pacific North‐west, with a lag time of 4 years, which is approximately equal to the travel time of water within the Pacific gyre from the western tropical Pacific Ocean to the Gulf of Alaska. Precipitation in the Desert South‐west correlates significantly with solar irradiance lagged 3 and 5 years, which suggests a link with ocean‐water temperature anomalies transported by the Equatorial Counter Current as well as the North Pacific gyre. With the correlations obtained, droughts coincide with periods of negative irradiance differences (dry high‐pressure development), and wet periods coincide with periods of positive differences (moist low‐pressure development).
Sensitivity analysis of extreme precipitation events
Authors: Katz Richard W. , Acero Juan Garrido 
Published: February 2007

AbstractA sensitivity analysis of the frequency of extreme precipitation events is performed. Extreme events in the form of total precipitation (e.g. over a month or season) exceeding a relatively large threshold (i.e. extremely wet conditions) or falling below a relatively small threshold (i.e. extremely dry conditions) are treated. To allow for the positive skewness of the distribution of total precipitation, a power transformation to normality is used. The relative sensitivities of extreme precipitation events to the median and to the scale parameter of this distribution are examined. It is shown that these relative sensitivities are both generally greater the more extreme the event. Moreover, the relative sensitivity to the scale is greater than that corresponding to the median for extreme wet events, whereas the opposite is true for extreme dry events. These theoretical results are illustrated through use of a network of precipitation observations in Spain.
Minimum sample size for synoptic weather type classification. Application to winter period data recorded on the catalan coast (North‐East Spain)
Authors: Lana X. , Fern Mills G. Ández 
Published: February 2007

AbstractCharacteristics of weather types obtained from a Davis and Kalkstein classification process can depend on a variety of factors. One of them is the number of components retained after principal component analysis (PCA) of the original data. The classification algorithm itself and the number of elements to be classified also play important roles in the final results. The main objective of the present paper is to describe a methodology leading to a deduction of the minimum sample size that must be considered in order to obtain a reliable synoptic weather type classification. Some rules related to the number of factors to be retained after a PCA and the optimal number of groups of our classification procedure are discussed. Finally, the main features of the winter weather types obtained from Barcelona Airport data are briefly presented.