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Climatic System (climatic + system)
Selected AbstractsEuropean snow cover extent variability and associations with atmospheric forcingsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2010Gina R. Henderson Abstract Snow cover in Europe represents an important component of the region's climatic system. Variability in snow cover extent can have major implications on factors such as low-level atmospheric temperatures, soil temperatures, soil moisture, stream discharge, and energy allocation involved in the warming and melting of the snowpack. The majority of studies investigating Northern Hemisphere snow cover identify European snow cover extent as a portion of the Eurasian record, possibly masking complexities of this subset. This study explores the variability of European snow cover extent from 1967,2007, with the region in question including the area of Europe extending eastward to the Ural Mountains (60°E). Using the 89 × 89 gridded National Oceanic and Atmospheric Administration (NOAA) Northern Hemisphere weekly satellite snow cover product, area estimates of seasonal snow cover were calculated, and their relationship to gridded temperature, precipitation, and sea-level pressure data analysed. The spatial variability of snow cover extent was also explored using geographical information systems (GIS). The combined results from both surface temperature and precipitation analyses point towards snow cover extent in Europe being primarily temperature dependent. Atmospheric variables associated with extremes in snow cover extent were investigated. Large (small) European snow extent is associated with negative (positive) 850 hPa zonal wind anomalies, negative (positive) European 1000,500 hPa thickness anomalies, and generally positive (negative) Northern European precipitation anomalies. Sea-level pressure and 500 hPa results indicate strong associations between large (small) snow cover seasons and the negative (positive) phase of the North Atlantic Oscillation. Copyright © 2009 Royal Meteorological Society [source] The stationarity of global mean climateINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2004B. G. Hunt Abstract The observed climate exhibits noticeable fluctuations on a range of temporal and spatial scales. Major fluctuations are often attributed to ,external' influences, such as volcanic eruptions or solar perturbations, which obscure climatic fluctuations associated with natural climatic variability generated by internal processes within the climatic system. Although it is difficult to isolate the role of natural climatic variability within the observed climatic system, coupled global climatic models permit such a discrimination to be made in appropriately designed simulations. Thus, the CSIRO coupled global climatic model has been used to determined some basic characteristics of annually averaged global mean climate within a multi-millennial climatic simulation. Some examination of observed climate is also presented. A stationary climatic state was simulated for periods of up to 10 000 years using the CSIRO model, with equilibrium usually being maintained to within 1,2% for all climatic variables investigated. The means by which such stationarity is maintained is analysed and the necessity for rapid negative feedback mechanisms is emphasized. The role of topographically induced climatic features is also discussed. Finally, the implications of the present, presumably greenhouse-related, global warming are considered in the context of the present results. Copyright © 2004 Royal Meteorological Society [source] Pollen-based biome reconstructions for Colombia at 3000, 6000, 9000, 12 000, 15 000 and 18 000 14C yr ago: Late Quaternary tropical vegetation dynamicsJOURNAL OF QUATERNARY SCIENCE, Issue 2 2002Robert Marchant Abstract Colombian biomes are reconstructed at 45 sites from the modern period extending to the Last Glacial Maximum (LGM). The basis for our reconstruction is pollen data assigned to plant functional types and biomes at six 3000-yr intervals. A reconstruction of modern biomes is used to check the treatment of the modern pollen data set against a map of potential vegetation. This allows the biomes reconstructed at past periods to be assessed relative to the modern situation. This process also provides a check on the a priori assignment of pollen taxa to plant functional types and biomes. For the majority of the sites, the pollen data accurately reflect the potential vegetation, even though much of the original vegetation has been transformed by agricultural practices. At 18 000 14C yr BP, a generally cool and dry environment is reflected in biome, assignments of cold mixed forests, cool evergreen forests and cool grassland,shrub; the latter extending to lower altitudes than presently recorded. This signal is strongly recorded at 15 000 and 12 000 14C yr BP, the vegetation at these times also reflecting a relatively cool and dry environment. At 9000 14C yr BP there is a shift to biomes thought to result from slightly cooler environmental conditions. This trend is reversed by 6000 14C yr BP; most sites, within a range of different environmental settings, recording a shift to more xeric biome types. There is an expansion of steppe and cool mixed-forest biomes, replacing tropical dry forest and cool grassland,shrub biomes, respectively. These changes in biome assignments from the modern situation can be interpreted as a biotic response to mid-Holocene climatic aridity. At 3000 14C yr BP the shift is mainly to biomes characteristic of slightly more mesic environmental conditions. There are a number of sites that do not change biome assignment relative to the modern reconstruction, although the affinities that these sites have to a specific biome do change. These ,anomalies' are interpreted on a site-by-site basis. Spatially constant, but differential response of the vegetation to climatic shifts are related to changes in moisture sources and the importance of edaphic controls on the vegetation. The Late Quaternary reconstruction of large-scale vegetation dynamics in Colombia allows an understanding of the environmental controls on these to be developed. In particular, shifts in the character of the main climatic systems that influence Colombian vegetation are described. Copyright © 2002 John Wiley & Sons, Ltd. [source] Evaluating land use/land cover changes and fragmentation in the Camili forest planning unit of northeastern Turkey from 1972 to 2005LAND DEGRADATION AND DEVELOPMENT, Issue 4 2007F. Sivrikaya Abstract Changes in land use/land cover have important consequences on the management of natural resources including soil and water quality, global climatic systems and biodiversity. This study analysed the spatial and temporal pattern of land use/land cover change in the Camili forest planning unit that includes the Camili Biosphere Reserve Area within the Caucasian hotspot, in the northeast corner of Turkey. To assess the patterns during a 33-year period, the necessary data were obtained from forest stand maps and evaluated with Geographic Information Systems and FRAGSTATS. Results showed that the total forested areas increased from 19,946·5,ha (78·6% of the study area) in 1972 to 20,797·3,ha (81·9 per cent) in 2005 with a slight net increase of 851,ha. Softwood cover types (411·8,ha) completely transitioned to other cover types over 33-year period. In terms of spatial configuration, the total number of forest fragments increased from 172 to 608, and mean size of forest patch (MPS) decreased from 147·7,ha to 41·8,ha during the period. Nearly 84 per cent of the patches in 1972 and 93 per cent of them in 2005 generally seem to concentrate into 0,100,ha patch size class, indicating more fragmented landscape over time that might create a risk for the maintenance of biodiversity of the area. There were apparent trends in the temporal structure of forest landscape, some of which may issue from mismanagement of the area, social conflict, and illegal utilization of forest resources due to ineffective forest protection measurements. The study revealed that it is important to understand both spatial and temporal changes of land use/land cover and their effects on landscape pattern to disclose the implications for land use planning and management. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||