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Regional Climate Changes (regional + climate_change)
Selected AbstractsMODELED REGIONAL CLIMATE CHANGE IN THE HYDROLOGIC REGIONS OF CALIFORNIA: A CO2 SENSITIVITY STUDY,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 3 2004Mark A. Snyder ABSTRACT: Using a regional climate model (RegCM2.5), the potential impacts on the climate of California of increasing atmospheric CO2 concentrations were explored from the perspective of the state's 10 hydrologic regions. Relative to preindustrial CO2 conditions (280 ppm), doubled preindustrial CO2 conditions (560 ppm) produced increased temperatures of up to 4°C on an annual average basis and of up to 5°C on a monthly basis. Temperature increases were greatest in the central and northern regions. On a monthly basis, the temperature response was greatest in February, March, and May for nearly all regions. Snow accumulation was significantly decreased in all months and regions, with the greatest reduction occurring in the Sacramento River region. Precipitation results indicate drier winters for all regions, with a large reduction in precipitation from December to April and a smaller decrease from May to November. The result is a wet season that is slightly reduced in length. Findings suggest that the total amount of water in the state will decrease, water needs will increase, and the timing of water availability will be greatly perturbed. [source] Regional Climate Change: Trend Analysis of Temperature and Precipitation Series at Selected Canadian SitesCANADIAN JOURNAL OF AGRICULTURAL ECONOMICS, Issue 1 2000J. Stephen Clark Global climate change does not necessarily imply that temperature or precipitation is increasing at specific locations. The hypothesis of increasing temperature and precipitation trends associated with global climate change is tested using actual annual temperature and precipitation data for nine selected weather stations, spatially distributed across Canada. Vogelsang's (1998) partial sum and Woodward et al's (1997) bootstrap methods are used for testing for trend. Both methods suggest no warming in the Canadian temperature series except for Toronto, Ontario, which had significant increase over time, along with Moncton, New Brunswick, and Indian Head, Saskatchewan, which had marginal increases. There is no evidence of increasing trend in precipitation except for Moncton, New Brunswick, which had a significantly increasing trend. Thus, public policies designed to address the regional effects of climate change need to be adapted for a particular ecological zone, based on knowledge of the climate trends for that region, rather than on general global climate change patterns. Les changements climatiques à l'échelle planétaire ne signifient pas nécessairement que la température et les précipitations sont en augmentation dans des emplacements donnés. Nous avons testé I'hypothèse d'une assoviation de la tendance à la hausse de la température et des précipitations avec les changements climatiques planétaires à partir des données réelles de température et de précipitations obtenues à 9 stations d'observation climatique réparties dans les diverses régions du Canada. Nous utilisons, pour cefaire, la méthode des sommes partielles de Vogelsang (1998) et celle de rééchantillonnage bootstrap de Woodward et al (1997). Les deux méthodes ne révèlent aucun réchauffement de la température dans les séries chronologiques, sauf pour Toronto, en Ontario, où l'on constate une hausse significative en fonction du temps, ainsi que pour Moncton au Nouveau-Brunswick et Indian Head en Saskatchewan qui marquent de très légères augmentations. Rien n'indique une tendance à la hausse des précipitations, sauf à Moncton où se dessine une tendance significative dans ce sens. Les programmes publics destinés à faire face aux effets régionaux du changement climatique doivent donc être adaptés à chaque zone écologique particulière, à partir d"observations faites dans la région même, plutôt que de la configuration du changement climatique à l'échelle planétaire. [source] Soil arthropods as indicators of water stress in Antarctic terrestrial habitats?GLOBAL CHANGE BIOLOGY, Issue 12 2003Peter Convey Abstract Abiotic features of Antarctic terrestrial habitats, particularly low temperatures and limited availability of liquid water, strongly influence the ecophysiology and life histories of resident biota. However, while temperature regimes of a range of land microhabitats are reasonably well characterized, much less is known of patterns of soil water stress, as current technology does not allow measurement at the required scale. An alternative approach is to use the water status of individual organisms as a proxy for habitat water status and to sample over several years from a population to identify seasonal or long-term patterns. This broad generalization for terrestrial invertebrates was tested on arthropods in the maritime Antarctic. We present analyses of a long-term data set of body water content generated by monthly sampling for 8,11 years of seven species of soil arthropods (four species of Acari, two Collembola and one Diptera) on maritime Antarctic Signy Island, South Orkney Islands. In all species, there was considerable within- and between-sample variability. Despite this, clear seasonal patterns were present in five species, particularly the two collembolans and a prostigmatid mite. Analyses of monthly water content trends across the entire study period identified several statistically significant trends of either increase or decrease in body water content, which we interpret in the context of regional climate change. The data further support the separation of the species into two groups as follows: firstly, the soft-bodied Collembola and Prostigmata, with limited cuticular sclerotization, which are sensitive to changes in soil moisture and are potentially rapid sensors of microhabitat water status, secondly, more heavily sclerotized forms such as Cryptostigmata (=Oribatida) and Mesostigmata mites, which are much less sensitive and responsive to short-term fluctuations in soil water availability. The significance of these findings is discussed and it is concluded that annual cycles of water content were driven by temperature, mediated via radiation and precipitation, and constituted reliable indicators of habitat moisture regimes. However, detailed ecophysiological studies are required on particular species before such information can be used to predict over long timescales. [source] Detection of process-related changes in plant patterns at extended spatial scales during early dryland desertificationGLOBAL CHANGE BIOLOGY, Issue 11 2003Jorge Ares Abstract Arid and semiarid shrublands occupy extensive land areas over the world, are susceptible to desertification by anthropic use and can contribute to regional climate change. These prompt the interest to monitor and evaluate these lands adequately in order to detect early stages of degradation. Evaluation topics must refer to biology-relevant characteristics of these systems, while simultaneously satisfying sampling consistency over extended landscape areas. We present an analysis of process-relevant parameters related to changes in the spatial arrangement of the plant canopy of shrublands inferred from high-resolution panchromatic aerial photos and Interferometric Synthetic Aperture Radar imagery. We obtained low-altitude images systematically located along several gradients of land-use intensity in a Patagonian Monte shrubland in Argentina. Images were digitized to spatial resolutions ranging from 0.09 to 0.72 m (pixel size) and the average values and an-isotropic characteristics of the plant canopy patterns were quantified by means of a Fourier metric. We used radar-derived imagery to overlay the panchromatic images on a digital elevation model in order to study the correspondence of potential runoff patterns and the spatial arrangement of plants. We related an-isotropic features of the plant canopy images to the prevailing wind regime. Observed trends were further interpreted on the basis of a spatial-explicit simulation model describing the dynamics of the main functional groups in the plant community. We conclude that early stages of anthropic-driven dryland degradation in the Patagonian Monte can be characterized by the incipient un-coupling of spatial vegetation patterns from those of runoff at a landscape scale, and a progressive coupling to the spatial pattern of the wind regime. The method and metrics we present can be used to quantify early desertification changes in other similar drylands at extended spatial scales. [source] Evaluation of soil saturation, soil chemistry, and early spring soil and air temperatures as risk factors in yellow-cedar declineGLOBAL CHANGE BIOLOGY, Issue 3 2006D. V. D'AMORE Abstract Yellow-cedar (Callitropsis nootkatensis (D. Don) Oerst.) is a valuable tree species that is experiencing a widespread decline and mortality in southeast Alaska. This study evaluated the relative importance of several potential risk factors associated with yellow-cedar decline: soil saturation, soil aluminum (Al) toxicity or calcium (Ca) deficiency, and air and soil temperature. Data were collected from permanent vegetation plots established in two low-elevation coastal forests exhibiting broad ranges of cedar mortality. Measurements of each risk factor were contrasted among classified forest zones to indicate if there were strong links with decline. Hydrology alone is weakly associated with yellow-cedar decline, but could have a predisposing role in the decline by creating exposed conditions because of reduced forest productivity. Yellow-cedar decline is not strongly associated with soil pH and extractable Al and Ca, but there appears to be Ca enrichment of surface soils by feedback from dead yellow-cedar foliage. Air and soil temperature factors are strongly associated with decline. Based on these results, an hypothesis is presented to explain the mechanism of tree injury where exposure-driven tree mortality is initiated in gaps created by soil saturation and then expands in gaps created by the tree-mortality itself. The exposure allows soils to warm in early spring causing premature dehardening in yellow-cedar trees and subsequent freezing injury during cold events. Yellow-cedars growing in the protection of shade or snow are not preconditioned by this warming, and thus not as susceptible to cold injury. Yellow-cedar decline appears to be associated with regional climate changes, but whether the cause of these changes is related to natural or human-induced climate shifts remains uncertain. Management implications, the possible role of climate, and recommended research are discussed. [source] Performance of statistical downscaling models in GCM validation and regional climate change estimates: application for Swedish precipitationINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2001Aristita Busuioc Abstract This study deals with an analysis of the performance of a general circulation model (GCM) (HadCM2) in reproducing the large-scale circulation mechanisms controlling Swedish precipitation variability, and in estimating regional climate changes owing to increased CO2 concentration by using canonical correlation analysis (CCA). Seasonal precipitation amounts at 33 stations in Sweden over the period 1899,1990 are used. The large-scale circulation is represented by sea level pressure (SLP) over the Atlantic,European region. The link between seasonal Swedish precipitation and large-scale SLP variability is strong in all seasons, but especially in winter and autumn. For these two seasons, the link is a consequence of the North Atlantic Oscillation (NAO) pattern. In winter, another important mechanism is related to a cyclonic/anticyclonic structure centred over southern Scandinavia. In the past century, this connection has remained almost unchanged in time for all seasons except spring. The downscaling model that is built on the basis of this link is skilful in all seasons, but especially so in winter and autumn. This observed link is only partially reproduced by the HadCM2 model, while large-scale SLP variability is fairly well reproduced in all seasons. A concept about optimum statistical downscaling models for climate change purposes is proposed. The idea is related to the capability of the statistical downscaling model to reproduce low frequency variability, rather than having the highest skill in terms of explained variance. By using these downscaling models, it was found that grid point and downscaled climate signals are similar (increasing precipitation) in summer and autumn, while in winter, the amplitudes of the two signals are different. In spring, both signals show a slight increase in the northern and southern parts of Sweden. Copyright © 2001 Royal Meteorological Society [source] Persistence of coastal spruce refugia during the Holocene in northern New England, USA, detected by stand-scale pollen stratigraphiesJOURNAL OF ECOLOGY, Issue 2 2002Molly Schauffler Summary 1 Pollen data from wet, forested hollows in five spruce (Picea) stands on the eastern coast of Maine, USA, reveal that spruce has been well-established (spruce pollen > 6%) for at least 5000 years at four of the sites (Isle au Haut, Schoodic Peninsula, and Roque Island). Spruce became dominant in the fifth stand (Blackwoods, Mount Desert Island) only in the last 2000 years. This is in contrast to pollen stratigraphies from two inland forest hollows and from inland lakes that indicate a significant region-wide increase in the abundance of spruce only 1000 years ago. 2 All five coastal pollen stratigraphies suggest that conditions along the east coast of Maine became cooler and moister sometime between 6000 and 5000 years ago. Mid-Holocene changes in vegetation and sediment accumulation correspond with the timing of rapid increases in tidal amplitude and diurnal mixing of cold water in the Gulf of Maine, suggestive that these resulted in increased marine effects on the local climate at a time that was generally warmer than present. 3 Two inland forest-hollow stratigraphies do not show evidence of mid-Holocene cooling. Coastal effects therefore persisted for several thousand years despite regional climate changes. 4 The pollen data suggest that refugia along the coast (and probably in isolated sites inland), may have played a critical role in allowing the rapid regional expansion of spruce around 1000 years ago. The steep increases in the abundance of spruce pollen in all forest-hollow and lake pollen stratigraphies in northern New England at that time corroborate other evidence of a region-wide shift to cooler and moister conditions. 5 Pollen stratigraphies from small forested hollows provide a means to examine local vegetation dynamics and interpret those dynamics in the context of regional signals. [source] | ||||||||||