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Clear Seasonality (clear + seasonality)
Selected AbstractsConcentrations and partitioning of polychlorinated biphenyls in the surface waters of the southern Baltic Sea,seasonal effectsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2006Kilian E.C. Smith Abstract In the marine environment, the partitioning of hydrophobic organic contaminants, such as polychlorinated biphenyls (PCBs), between the dissolved and suspended matter phases in the water column plays a fundamental role in determining contaminant fate (e.g., air,water exchange or food-chain uptake). Despite the pronounced seasonality in physical, chemical, and biological conditions in temperate marine ecosystems, little is known about the seasonality in organic contaminant partitioning behavior. Surface water from the western Baltic Sea was sampled regularly during an 18-month period between February 2003 and July 2004. The concentrations of seven PCB congeners were determined in the dissolved and particulate organic carbon (POC) phases. An inverse relationship was found between KPOC (i.e., the ratio between the POC-normalized PCB concentration [pg/kg POC] and the dissolved concentration [pg/L]) and temperature. The decrease in the water temperature of 20°C between summer and winter resulted in an increase in KPOC by a factor of approximately five. The POC-normalized PCB concentrations were higher in winter than in summer by a factor of 9 to 20. This reflected the higher KPOC and somewhat greater PCB concentrations in the dissolved phase, and it could have consequences for bioaccumulation of these chemicals in aquatic food webs. The results demonstrate a clear seasonality in contaminant partitioning in the temperate marine environment that should be accounted for when interpreting field data or modeling contaminant fate. [source] Seasonal and inter-annual variability of the moisture sources for Alpine precipitation during 1995,2002INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2010Harald Sodemann Abstract This study presents a first quantitative climatology of the moisture sources for precipitation in the European Alps, covering a 7-year period from January 1995 to August 2002. Using a Lagrangian moisture source diagnostic and data from the ERA-40: European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis, the contribution of the following moisture sources to annual mean precipitation has been diagnosed: North Atlantic ocean 39.6%, Mediterranean 23.3%, North Sea and Baltic Sea 16.6%, and European land surface 20.8%. However, strong seasonal variability of the influence of various moisture sources is evident. Most notably, moisture transport to the Alps changes from an oceanic mode characterised by dominantly North Atlantic moisture sources during winter to a continental mode during summer with a marked contribution from Central European land areas. The method identifies inter-annual variability with respect to the location of the moisture sources in the North Atlantic, and the importance of precipitation recycling during summer. Despite the smoothed Alpine orography in the ERA-40 model, the Alps act as an effective barrier for meridional moisture transport, leading to distinct mean moisture source locations at their northern and southern slopes. The Northern Alps are predominantly influenced by the North Atlantic ocean and Central European land sources with a clear seasonality and limited monthly variability. In contrast, the Southern Alps receive a large fraction of precipitation from the Mediterranean with considerable month-to-month variability. Possible implications of these differences for precipitation extremes and stable isotopes in precipitation are discussed. Copyright © 2009 Royal Meteorological Society [source] Stable water isotope simulation in different reservoirs of Manaus, Brazil, by Community Land Model incorporating stable isotopic effectINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2009Xin-Ping Zhang Abstract The daily and monthly variations of stable water isotopes in different reservoirs at Manaus, Brazil, are simulated and inter-compared in an equilibrium year, using the Community Land Model (CLM) involving the stable isotopic effects as a diagnostic tool for an in-depth understanding of the hydrometeorological processes. On the daily scale, the ,18O in precipitation, vapour and surface runoff have clear seasonality, with marked negative correlations with the corresponding water amount. However, the ,18O in surface dew displays marked positive correlation with dew amount. On the diurnal time scale, the ,18O in precipitation displays an unclear diurnal variation and an unmarked correlation with the precipitation amount. However, the ,18O in vapour keeps consistency with specific humidity. On the monthly time scale, the ,18O in precipitation and surface runoff displays distinct bimodal seasonality, with two maxima in January and in July, and two minima in April and in October; Vapor displays a similar bimodal pattern, two maxima appear in January and August, and two minima in April and November. The amount effect simulated on the monthly time scale has consistency with the actual survey result at the Manaus station, from 1965 to 1990, set up by International Atomic Energy Agency (IAEA)/World Meteorological Organization (WMO). In addition, the slope (7.49) and the intercept (6.25) of the simulated meteoric water line (MWL) are all smaller than those of the actual mean MWL. However, compared with the annual MWL, the simulated MWL lies within the variation range of actual MWLs. Copyright © 2008 Royal Meteorological Society [source] Identification, measurement and interpretation of tree rings in woody species from mediterranean climatesBIOLOGICAL REVIEWS, Issue 1 2003PAOLO CHERUBINI ABSTRACT We review the literature dealing with mediterranean climate, vegetation, phenology and ecophysiology relevant to the understanding of tree-ring formation in mediterranean regions. Tree rings have been used extensively in temperate regions to reconstruct responses of forests to past environmental changes. In mediterranean regions, studies of tree rings are scarce, despite their potential for understanding and predicting the effects of global change on important ecological processes such as desertification. In mediterranean regions, due to the great spatio-temporal variability of mediterranean environmental conditions, tree rings are sometimes not formed. Often, clear seasonality is lacking, and vegetation activity is not always associated with regular dormancy periods. We present examples of tree-ring morphology of five species (Arbutus unedo, Fraxinus ornus, Quercus cerris, Q. ilex, Q. pubescens) sampled in Tuscany, Italy, focusing on the difficulties we encountered during the dating. We present an interpretation of anomalies found in the wood structure and, more generally, of cambial activity in such environments. Furthermore, we propose a classification of tree-ring formation in mediterranean environments. Mediterranean tree rings can be dated and used for dendrochronological purposes, but great care should be taken in selecting sampling sites, species and sample trees. [source] Species-Specific Growth Responses to Climate Variations in Understory Trees of a Central African Rain ForestBIOTROPICA, Issue 4 2010Camille Couralet ABSTRACT Basic knowledge of the relationships between tree growth and environmental variables is crucial for understanding forest dynamics and predicting vegetation responses to climate variations. Trees growing in tropical areas with a clear seasonality in rainfall often form annual growth rings. In the understory, however, tree growth is supposed to be mainly affected by interference for access to light and other resources. In the semi-deciduous Mayombe forest of the Democratic Republic of Congo, the evergreen species Aidia ochroleuca, Corynanthe paniculata and Xylopia wilwerthii dominate the understory. We studied their wood to determine whether they form annual growth rings in response to changing climate conditions. Distinct growth rings were proved to be annual and triggered by a common external factor for the three species. Species-specific site chronologies were thus constructed from the cross-dated individual growth-ring series. Correlation analysis with climatic variables revealed that annual radial stem growth is positively related to precipitation during the rainy season but at different months. The growth was found to associate with precipitation during the early rainy season for Aidia but at the end of the rainy season for Corynanthe and Xylopia. Our results suggest that a dendrochronological approach allows the understanding of climate,growth relationships in tropical forests, not only for canopy trees but also for evergreen understory species and thus arguably for the whole tree community. Global climate change influences climatic seasonality in tropical forest areas, which is likely to result in differential responses across species with a possible effect on forest composition over time. Abstract in French is available at http://www.blackwell-synergy.com/loi/btp [source] Seasonal variation and meteotropism in suicide: clinical relevance of findings and implications for researchACTA NEUROPSYCHIATRICA, Issue 1 2002A. Preti Seasonal asymmetry in yearly suicide occurrence is a long-observed phenomenon in psychiatric, suicidological and sociological research, and the effects of seasonal factors on suicidal behaviour have been the focus of a number of earlier studies. Taking into account limitations of data and methods, these studies have in general favoured interpretations based on psychosocial factors. Recent studies have challenged the widely held notion that seasonal effects on suicide are not influenced by age, gender or the circumstances of the act. The suicides committed with violent methods have been shown to follow clearer seasonal patterns than suicides by less violent methods, and differences have been found between male and female cycles of occurrence. The seasonal occurrence of suicides has also been found to differ significantly between the young and the elderly. The use of inappropriate statistics or age- and gender-biased samples may have hidden a seasonal component in some previous studies on attempted suicide. The absence of seasonality in earlier studies on attempted suicide was interpreted as depending upon the minor relevance of psychiatric and biological factors in non-fatal self-harm. However, recent studies have reported clear seasonality in attempted suicide samples, with older people showing greater seasonal effect. Recent literature after 1985 on seasonal variation and weather or climate influence in attempted and completed suicide is reviewed. Suggestions for research and the development of more effective preventative strategies are offered. [source] | ||||||||||