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Long-term Average (long-term + average)
Selected AbstractsMesoscale eddies and survival of late stage Pacific sardine (Sardinops sagax) larvaeFISHERIES OCEANOGRAPHY, Issue 1 2001Elizabeth A. Logerwell We examined the distribution of sardine larvae relative to environmental conditions with the purpose of identifying and characterizing habitat that encourages high larval growth and survival, based on the 1983,1998 surveys of the California Cooperative Oceanic Fisheries Investigations (CalCOFI). Long-term averages show that sardine ,survivors' (spatially aggregated larvae , 18 days old) were most abundant offshore, whereas sardine egg density, chlorophyll biomass and zooplankton volume were greatest inshore. In contrast, mesoscale eddies, observed in remotely sensed sea surface temperature imagery, were found only in offshore regions. To further examine the link between eddies , which often result in locally elevated chlorophyll and zooplankton , and sardine survival, we compared the distribution of larvae and eddies survey by survey. Sardine survivors were most abundant offshore in only one-quarter of the research surveys, and when they were most abundant offshore they were associated with eddies. This indicates that the offshore eddy habitat produced exceptionally large numbers of survivors, as evidenced by the disproportionate effect on the long-term average. [source] Skiing Less Often in a Warmer World: Attitudes of Tourists to Climate Change in an Australian Ski ResortGEOGRAPHICAL RESEARCH, Issue 2 2010CATHERINE MARINA PICKERING Abstract Climate change will affect tourism destinations that are dependent on natural resources, such as snow. Currently there is limited research into attitudes, intentions and actual visitation patterns of skiers in response to reduced snow cover. Therefore the awareness of, and attitudes towards, climate change of 351 ski tourists were assessed in the largest ski resort in Australia in 2007, repeating a survey conducted in 1996. Ninety percent of skiers in 2007 would ski less often in Australian resorts if the next five years had low natural snow, up from 75% of skiers surveyed in 1996: 69% would ski less often, 5% would give up and 16% would ski at the same levels but overseas. Nearly all skiers thought that climate change would affect the ski industry (87% compared with 78% in 1996), and that this would occur sooner than in the 1996 survey. Visitation in a poor snow year (2006, +0.85°C average annual temperature, 54% less natural snow) was ,13.6% of the long-term average, indicating poor natural snow resulted in decreased visitation, despite extensive use of snow making. The implications of changes in climate conditions and tourist attitudes for Australian ski resorts are assessed including for snow making and summer tourism. [source] Abiotic constraints on the establishment of Quercus seedlings in grasslandGLOBAL CHANGE BIOLOGY, Issue 2 2003Brett T. Danner Abstract High evaporative demand and periodic drought characterize the growing season in midwestern grasslands relative to deciduous forests of the eastern US, and predicted climatic changes suggest that these climatic extremes may be exacerbated. Despite this less than optimal environment for tree seedling establishment, deciduous trees have expanded into adjacent tallgrass prairie within the last century leading to a dramatic land cover change. In order to determine the role of light and temperature on seedling establishment, we assessed carbon and water relations and aboveground growth of first-year Quercus macrocarpa seedlings exposed to one of three conditions: (1) intact tallgrass prairie communities (control), (2) aboveground herbaceous biomass removed (grass removal), and (3) shade plus biomass removal to reduce light (PFD) to levels typical of the grassland-forest ecotone (shade). In the 2000 growing season, precipitation was 35% below the long-term average, which had a significant negative effect on oak seedling carbon gain at midseason (photosynthesis declined to 10% of maximum rates). However, net photosynthesis and stomatal conductance in the shade treatment was ca. 2.5 and 1.5 times greater, respectively, than in control treatment seedlings during this drought. During this period, leaf and air temperatures in control seedlings were similar whereas leaf temperatures in the shade treatment remained below air temperature. A late-season recovery period, coincident with decreased air temperatures, resulted in increased net photosynthesis for all seedlings. Increased photosynthetic rates and water relations in shaded seedlings compared to seedlings in full sun suggest that, at least in dry years, high light and temperature may negatively impact oak seedling performance. However, high survival rates for all seedlings indicate that Q. macrocarpa seedlings are capable of tolerating both present-day and future climatic extremes. Unless historic fire regimes are restored, forest expansion and land cover change are likely to continue. [source] Impact of climate variability on vegetative cover in the Butana area of SudanAFRICAN JOURNAL OF ECOLOGY, Issue 2009Muna Elhag Abstract Climate variability has an impact on the renewable natural resources. This impact is strong in regions with a delicate balance between climate and ecosystem, like the Sahelian regions. Rainfall is the most important climatic factor influencing livelihoods in Butana, north-eastern part of Sudan. All people and their livestock depend on the amount of rainfall that falls and supports plant growth. Butana area experienced severe drought in 1984, 1990 and 2000. Linear relationships between the long-term rainfall and AVHRR/NDVI data were developed for four separate zones in the Butana area. There is a significant correlation between peak NDVI (beginning of September) and cumulative rainfall for July and August, but weak relationships resulted when annual rainfall and cumulative NDVI were used. This is because the NDVI reached a plateau as the rainfall increased, then it remained constant despite further increases in rainfall. The departure from the long-term average of NDVI for each pixel was calculated using the departure average vegetation method. The area had a high percentage of departure during the drought years and the NDVI recovered during the following year when the rainfall was above the average. It can be noted that the area adjacent to the irrigated scheme showed considerable decrease in NDVI. This may be due to overexploitation by the nomads during the drought year. [source] Weighted Normality-Based Estimator in Correcting Correlation Coefficient Estimation Between Incomplete Nutrient MeasurementsBIOMETRICS, Issue 1 2000C. Y. Wang Summary. Consider the problem of estimating the correlation between two nutrient measurements, such as the percent energy from fat obtained from a food frequency questionnaire (FFQ) and that from repeated food records or 24-hour recalls. Under a classical additive model for repeated food records, it is known that there is an attenuation effect on the correlation estimation if the sample average of repeated food records for each subject is used to estimate the underlying long-term average. This paper considers the case in which the selection probability of a subject for participation in the calibration study, in which repeated food records are measured, depends on the corresponding FFQ value, and the repeated longitudinal measurement errors have an autoregressive structure. This paper investigates a normality-based estimator and compares it with a simple method of moments. Both methods are consistent if the first two moments of nutrient measurements exist. Furthermore, joint estimating equations are applied to estimate the correlation coefficient and related nuisance parameters simultaneously. This approach provides a simple sandwich formula for the covariance estimation of the estimator. Finite sample performance is examined via a simulation study, and the proposed weighted normality-based estimator performs well under various distributional assumptions. The methods are applied to real data from a dietary assessment study. [source] Longitudinal data analysis in pedigree studiesGENETIC EPIDEMIOLOGY, Issue S1 2003W. James Gauderman Abstract Longitudinal family studies provide a valuable resource for investigating genetic and environmental factors that influence long-term averages and changes over time in a complex trait. This paper summarizes 13 contributions to Genetic Analysis Workshop 13, which include a wide range of methods for genetic analysis of longitudinal data in families. The methods can be grouped into two basic approaches: 1) two-step modeling, in which repeated observations are first reduced to one summary statistic per subject (e.g., a mean or slope), after which this statistic is used in a standard genetic analysis, or 2) joint modeling, in which genetic and longitudinal model parameters are estimated simultaneously in a single analysis. In applications to Framingham Heart Study data, contributors collectively reported evidence for genes that affected trait mean on chromosomes 1, 2, 3, 5, 8, 9, 10, 13, and 17, but most did not find genes affecting slope. Applications to simulated data suggested that even for a gene that only affected slope, use of a mean-type statistic could provide greater power than a slope-type statistic for detecting that gene. We report on the results of a small experiment that sheds some light on this apparently paradoxical finding, and indicate how one might form a more powerful test for finding a slope-affecting gene. Several areas for future research are discussed. Genet Epidemiol 25 (Suppl. 1):S18,S28, 2003. © 2003 Wiley-Liss, Inc. [source] The development of a new set of long-term climate averages for the UKINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 8 2005Matthew Perry Abstract Monthly and annual long-term average datasets of 13 climate variables are generated for the periods 1961,90 and 1971,2000 using a consistent analysis method. Values are produced for each station in the Met Office's observing network and for a rectangular grid of points covering the UK at a horizontal spacing of 1 km. The variables covered are mean, maximum, minimum, grass minimum and soil temperature, days of air and ground frost, precipitation, days with rain exceeding 0.2 and 1 mm, sunshine, and days with thunder and snow cover. Gaps in the monthly station data are filled with estimates obtained via regression relationships with a number of well-correlated neighbours, and long-term averages are then calculated for each site. Gridded datasets are created by inverse-distance-weighted interpolation of regression residuals obtained from the station averages. This method does not work well for days of frost, thunder and snow, so an alternative approach is used. This involves first producing a grid of values for each month from the available station data. The gridded long-term average datasets are then obtained by averaging the monthly grids. The errors associated with each stage in the process are assessed, including verification of the gridding stage by leaving out a set of stations. The estimation of missing values allows a dense network of stations to be used, and this, along with the range of independent variables used in the regression, allows detailed and accurate climate datasets and maps to be produced. The datasets have a range of applications, and the maps are freely available through the Met Office Website. © Crown Copyright 2005. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. [source] An in situ estimate of food consumption of five cyprinid species in Lake BalatonJOURNAL OF FISH BIOLOGY, Issue 5 2002A. Specziár Daily rations of five cyprinid species, bream Abramis brama, silver bream Blicca bjoerkna, roach Rutilus rutilus, gibel Carassius auratus gibelio and carp Cyprinus carpio, in Lake Balaton, a large shallow lake, estimated by the Eggers model differed from that of the Elliott , Persson model by only , 4.3 to +7.3% (the differences were insignificant). Daily rations varied within the range of 0.23,0.69 in bream, 0.55,3.61 in silver bream, 0.69,4.65 in roach, 0.38,3.16 in gibel and 0.50,9.74 g dry 100 g wet fish mass,1 day ,1 in carp at temperatures ranging from 8.7,25.8% C. Daily ration was related exponentially with temperature in silver bream, roach, gibel and carp. For bream, a significant relationship was obtained only when a daily ration value was excluded from the analysis. Annual rations were assessed using the relationships between the daily ration estimates from the Elliott,Persson model and water temperature, and the long-term averages of the monthly water temperature data. From these estimates the bream population consumed 104%, silver bream 424%, roach 487%, gibel 363% and carp 913% dry mass of food of its wet biomass annually. [source] | |||||||||||||