| 1. |
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| 2. |
- Emmanuel, R, et al.
(författare)
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Influence of urban morphology and sea breeze on hot humid microclimate: the case of Colombo, Sri Lanka
- 2006
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Ingår i: Climate Research. - : Inter-Research Science Center. - 1616-1572 .- 0936-577X. ; 30:3, s. 189-200
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Tidskriftsartikel (refereegranskat)abstract
- Urbanisation leads to increased thermal stress in hot-humid climates due to increased surface and air temperatures and reduced wind speed. We examined the influence of urban morphology and sea breeze on the microclimate of Colombo, Sri Lanka. Air and surface temperatures, humidity and wind speed were measured at 1 rural and 5 urban sites during the warmest season. The urban sites differed in their height to width (H/W) ratio, ground cover and distance to the sea. Intra-urban air temperature differences were greatest during the daytime. A maximum intra-urban difference of 7 K was recorded on clear days. Maximum temperatures tended to decrease with increasing H/W ratio and proximity to the sea. All urban sites experienced a nocturnal urban heat island (UHI) when the sky was clear or partly cloudy. The temperature differences between sunlit and shaded urban surfaces reached 20 K, which shows the importance of shade in urban canyons (reducing long-wave radiation from surfaces). Within the urban areas, the vapour pressure was high (> 30 hPa) and showed little diurnal variation. Wind speeds were low (< 2 m s(-1)) and tended to decrease with increasing H/W ratio. Shading is proposed as the main strategy for lowering air and radiant temperatures; this can be achieved by deeper canyons, covered walkways and shade trees. It is also suggested to open up wind corridors perpendicular to the sea to facilitate deeper sea breeze penetration.
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| 3. |
- Good, P., et al.
(författare)
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Non-linear regional relationships between climate extremes and annual mean temperatures in model projections for 1961-2099 over Europe
- 2006
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Ingår i: Climate Research. - : Inter-Research Science Center. - 1616-1572 .- 0936-577X. ; 31:1, s. 19-34
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Tidskriftsartikel (refereegranskat)abstract
- A simple method is tested for scaling climate-extreme results from high resolution regional climate models (RCMs) to time-periods and emission scenarios for which the RCMs have not been run. The 30 yr mean relationships between indicators of extremes (IoEs) and annual mean daily maximum temperature (T-xa) are investigated. Such relationships from the UK Met Office Hadley Centre RCM HadRM3P, along with temperatures from the global climate model HadCM3, are used to scale IoEs to other time periods and scenarios. This is tested for selected indicators of heat-wave and drought over Europe for the period 1961-2099. Curvature is demonstrated in the relationships between these quantities and T-xa. Such non-linearities are shown to have a large potential effect on how these climate extremes are likely to evolve during the century, as well as their sensitivity to emissions. A broad picture of possible changes in European heat-wave and drought severity is presented. For drought over the Mediterranean and western Europe, a very clear positive curvature in the relationship between drought length and annually averaged temperature is found. (This feature is also common in a brief study of 6 other RCMs.) It suggests a rapid increase in drought length towards the end of the century, and a strong sensitivity to the emission scenario. Extended summer dry spells are projected to become a much more regular feature of western European climates. For European heatwaves, we find a slightly earlier onset of increases in heat-wave severity and a reduced sensitivity to emission scenarios than might be expected from a more straightforward interpretation of the Hadley Centre model results. This is linked with extreme dryness occurring at high summer in all years by the end of the century, but was not evident in the 6 other RCMs studied. Based on these results, suggestions are made for choices of future RCM experiments.
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| 4. |
- Hanssen-Bauer, I., et al.
(författare)
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Statistical downscaling of climate scenarios over Scandinavia
- 2005
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Ingår i: Climate Research. - : Inter-Research Science Center. - 0936-577X .- 1616-1572. ; 29:3, s. 255-268
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Tidskriftsartikel (refereegranskat)abstract
- Studies from recent years involving development and application of statistical downscaling models for Scandinavia (mainly Norway and Sweden) are reviewed. In most of the studies linear techniques were applied. Local temperature and/or precipitation were predictands in a majority of the studies. Large-scale temperature fields, either from 2 m or 850 hPa, were found to be the best predictors for local temperature, while a combination of atmospheric circulation indices and tropospheric humidity information were the best predictors for local precipitation. Statistically downscaled temperature scenarios for Scandinavia differ depending on climate model, emission scenario and downscaling strategy. There are nevertheless several common features in the temperature scenarios. The warming rates during the 21st century are projected to increase with distance from the coast and with latitude. In most of Scandinavia higher warming rates are projected in winter than in summer. For precipitation, the spread between different scenarios is larger than for temperature. A substantial part of the projected precipitation change is connected to projected changes in atmospheric circulation, which differ considerably from one model integration to another. A tendency for increased large-scale humidity over Scandinavia still implies that projections for the 21st century typically indicate increased annual precipitation. This tendency is most significant during winter. In northern Scandinavia the projections tend to show increased precipitation also during summer, but several scenarios show reduced summer precipitation in parts of southern Scandinavia. Comparisons with results from global and regional climate models indicate that both regional modeling and statistical downscaling add value to the results from the global models.
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| 5. |
- Hedenström, Anders, et al.
(författare)
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Migration speed and scheduling of annual events by migrating birds in relation to climate change
- 2007
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Ingår i: Climate Research. - : Inter-Research Science Center. - 1616-1572 .- 0936-577X. ; 35:1-2, s. 79-91
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Tidskriftsartikel (refereegranskat)abstract
- Empirical evidence for changed timing of migration in birds is emerging from both American and Euro-African migration systems. These changes are usually interpreted as a consequence of changes in climate. Responses in timing of migration and breeding may differ among species, and the adaptive significance is not well understood. There is a lack of theoretical understanding about time-shifts in life-history events due to climatic changes. In the present paper, we use 2 separate modelling approaches to investigate the effects of climate change on migration. We first use a simple model of flight speed and foraging to explore which factors may influence migration speed and stopover itinerary. Our second approach derives predictions based on an annual routine model, where behavioural strategies regarding timing of migration, breeding, moult and number of breeding attempts are modelled in an environment comprising 4 locations (breeding and wintering sites and 2 stopover sites). This approach takes account of interrelationships between behaviours and seasons as a step towards realistic modelling of migratory connectivity. Departure from the wintering site is advanced in relation to the advancement of spring if the moult is in summer, but not so for species with a winter moult, while arrival at the breeding site is advanced for both moult scenarios. Timing of breeding and number of successful broods were also affected by spring advancement, while start of moult is relatively unaffected by climate change. These optimal solutions under the modelled set of parameters are discussed with respect to current knowledge of the mechanisms underlying seasonal timing in birds.
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| 6. |
- Jonzén, Niclas, et al.
(författare)
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Bird migration and climate - Introduction
- 2007
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Ingår i: Climate Research. - : Inter-Research Science Center. - 1616-1572 .- 0936-577X. ; 35:1-2, s. 1-3
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 7. |
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| 8. |
- Knudsen, Endre, et al.
(författare)
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Characterizing bird migration phenology using data from standardized monitoring at bird observatories
- 2007
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Ingår i: Climate Research. - : Inter-Research Science Center. - 1616-1572 .- 0936-577X. ; 35:1-2, s. 59-77
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Forskningsöversikt (refereegranskat)abstract
- Long-term data from standardized monitoring programmes at bird observatories are becoming increasingly available. These data are frequently used for detecting changes in the timing of bird migration that may relate to recent climate change. We present an overview of problematic issues in the analysis of these data, and review approaches to and methods for characterizing bird migration phenology and its change over time. Methods are illustrated and briefly compared using autumn data on garden warbler Sylvia borin from a standardized mist-netting programme at Lista bird observatory, southern Norway. Bird migration phenology is usually characterized rather coarsely using a small number of sample statistics such as mean, median and selected quantiles. We present 2 alternative approaches. Smoothing methods describe the within-season pattern in the data at an arbitrary level of detail, while fitting a parametric seasonal distribution curve offers a coarse description of migration phenology relatively robust to sampling effects. Various methods for analyzing linear trends in the timing of bird migration are reviewed and discussed. Exploratory studies using long-term data gathered at bird observatories can yield more detailed insight into the phenomenon of bird migration and how phenologies relate to climate. Methodological advances are needed, particularly in order to better characterize the shape of phenological distributions and separate between sampling effects and 'true' phenology.
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| 9. |
- Linderholm, Hans W., 1968, et al.
(författare)
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Early nineteenth century drought in east central Sweden inferred from dendrochronological and historical archives
- 2005
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Ingår i: Climate Research. - : Inter-Research Science Center. - 0936-577X .- 1616-1572. ; 29:1, s. 63-72
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Tidskriftsartikel (refereegranskat)abstract
- Scots pine tree-ring width data and entries from a farmer's diary were combined to assess early nineteenth century drought in east central Sweden. Tree-ring data were used to reconstruct drought, in the form of the standardized precipitation index (SPI), back to 1750. Daily weather observations in the farmer's diary were translated to temperature and degree of drought for each growing season from 1815 to 1833. During this period, Scots pine growth was constantly below average, and radial growth in 89% of the years between 1806 and 1832 indicated dry summers. Within the same period, severe drought was reported in the diary during several years. Although individual summers have been drier before and after this period, the record suggests that 1806 to 1835 was the longest continuous drought in the last 250 yr, possibly even the last 300 yr. Furthermore, this event seems to have been of regional extent, as indicated by meteorological, historical and tree-ring data from northern and central Europe. The present study showed that a combination of dendrochronological and historical records yields more useful information about past droughts, in terms of impact and long-term context, than one or the other of these sources can provide alone.
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| 10. |
- Saino, Nicola, et al.
(författare)
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Temperature and rainfall anomalies in Africa predict timing of spring migration in trans-Saharan migratory birds
- 2007
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Ingår i: Climate Research. - : Inter-Research Science Center. - 1616-1572 .- 0936-577X. ; 35:1-2, s. 123-134
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Tidskriftsartikel (refereegranskat)abstract
- The long-term advance in the timing of bird spring migration in the Northern Hemisphere is associated with global climate change. The extent to which changes in bird phenology reflect responses to weather conditions in the wintering or breeding areas, or during migration, however, remains to be elucidated. We analyse the relationships between the timing of spring migration of 9 species of trans-Saharan migratory birds across the, Mediterranean, and thermal and precipitation anomalies in the main wintering areas south of the Sahara Desert and in North African stopover areas. Median migration dates were collected on the island of Capri (southern Italy) by standardized mist-netting during 1981 to 2004. High temperatures in sub-Saharan Africa (Sahel and Gulf of Guinea) prior to northward migration (February and March) were associated with advanced migration. Moreover, birds migrated earlier when winter rainfall in North Africa was more abundant. The relationships between relevant meteorological variables and timing of migration were remarkably consistent among species, suggesting a coherent response to the same extrinsic stimuli. All these results were obtained while statistically controlling for the long-term trend towards the earlier timing of spring migration across the Mediterranean that has been documented in previous analyses of the same dataset, a trend that was confirmed by the present analyses. In conclusion, our results suggest that thermal conditions in the wintering quarters, as well as rainfall in North African stopover areas, can influence interannual variation in migration phenology of trans-Saharan migratory birds, although the ecological mechanisms that causally link meteorological conditions to the timing of migration remain a matter of speculation.
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| 11. |
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| 12. |
- Bärring, Lars, et al.
(författare)
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Defining dry/wet spells for point observations, observed area averages, and regional climate model gridboxes in Europe
- 2006
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Ingår i: Climate Research. - 1616-1572. ; 31:1, s. 35-49
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Tidskriftsartikel (refereegranskat)abstract
- A new method for optimising threshold values of dry/wet spells is evaluated. A set of indices is used to find the best threshold giving good correspondence between the frequency of dry/wet spells in Hadley Centre regional model (HadRM3) output, reference observations with predetermined thresholds, and area-averaged observations. The analyses focus on selected model gridboxes in 3 different European climate regimes (Sweden, UK, Italy), where station data are available from several locations. In addition, a pan-European analysis using the European Climate Assessment (ECA) dataset is carried out. Generally, there is good agreement between point observations and the corresponding area average using the common thresholds of 0.1 or 1.0 mm with observational data. Applying the optimal thresholds on the model output is important, as it typically results in substantially better agreement between the simulated and observed series of dry/wet days. The fitted optimal pan-European dry/wet threshold is (1) 0.47 or 0.15 mm, depending on model version, for the observed point data threshold of 0.1 mm, and (2) 1.2 or 0.56 mm, depending on model version, for the threshold of 1.0 mm.
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| 13. |
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| 14. |
- Schlyter, P, et al.
(författare)
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Assessment of the impacts of climate change and weather extremes on boreal forests in northern Europe, focusing on Norway spruce
- 2006
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Ingår i: Climate Research. - 1616-1572. ; 31:1, s. 75-84
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Tidskriftsartikel (refereegranskat)abstract
- The boreal and boreo-nemoral forests in Europe, which occur in northern and northeastern Europe, are dominated by 2 coniferous species, Norway spruce Picea abies (L.) Karst. being economically the most important one. Forestry is of major economic importance in this region. Forestry planning and climate change scenarios are based on similar (long-term) timescales, i.e. between 70 and 120 yr. Within the EU project 'Modelling the Impact of Climate Extremes' (MICE), we have used 'present day' runs (1961-1990) and future scenarios (2070-2100, emission scenarios A2 and B2 from the Special Report on Emissions Scenarios [SRES]) of the HadRM3 regional climate model to study and model direct and indirect effects of changing climate on Norway spruce in Sweden and northern Europe. According to our results, extreme climate events like spring temperature backlashes and summer drought will increase in frequency and duration. In combination with a raised mean temperature, climate extremes will negatively precondition trees (i.e. increase their susceptibility) to secondary damage through pests and pathogens. Decreased forest vitality also makes stands more susceptible to windthrow. Storm damage is discussed based on a 100 yr storm damage record for Sweden. Marginally increased frequencies and windspeeds of storms may cause disproportionate increases in windthrow. Increased economic hazards can be expected from a combination of the increased volumes of wind-thrown timber, and a greater likelihood of additional generations of spruce bark beetle Ips typographus (further encouraged by the increase in fallen timber), as a result of a changing climate with warmer summers.
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| 15. |
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