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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Vegetation phenology, the study of the timing and length of the terrestrial growing season and its connection to climate, is increasingly important in integrated Earth system science. Phenological variability is an excellent barometer of short- and long-term climatic variability, strongly influences surface meteorology, and may influence the carbon cycle. Here, using the 1895–1993 Vegetation/Ecosystem Modelling and Analysis dataset and the Biome-BGC terrestrial ecosystem model, we investigated the relationship between phenological metrics and annual net ecosystem exchange (NEE) of carbon. For the 1167 deciduous broad leaf forest pixels, we found that NEE was extremely weakly related to canopy duration (days from leaf appearance to complete leaf fall). Longer canopy duration, did, however, sequester more carbon if warm season precipitation was above average. Carbon uptake period (number of days with net CO2 uptake from the atmosphere), which integrates the influence of all ecosystem states and processes, was strongly related to NEE. Results from the Harvard Forest eddy-covariance site supported our findings. Such dramatically different results from two definitions of ‘growing season length’ highlight the potential for confusion among the many disciplines engaged in phenological research.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Global change biology 11 (2005), S. 0 
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The phenological state of vegetation significantly affects exchanges of heat, mass, and momentum between the Earth's surface and the atmosphere. Although current patterns can be estimated from satellites, we lack the ability to predict future trends in response to climate change. We searched the literature for a common set of variables that might be combined into an index to quantify the greenness of vegetation throughout the year. We selected as variables: daylength (photoperiod), evaporative demand (vapor pressure deficit), and suboptimal (minimum) temperatures. For each variable we set threshold limits, within which the relative phenological performance of the vegetation was assumed to vary from inactive (0) to unconstrained (1). A combined Growing Season Index (GSI) was derived as the product of the three indices. Ten-day mean GSI values for nine widely dispersed ecosystems showed good agreement (r〉0.8) with the satellite-derived Normalized Difference Vegetation Index (NDVI). We also tested the model at a temperate deciduous forest by comparing model estimates with average field observations of leaf flush and leaf coloration. The mean absolute error of predictions at this site was 3 days for average leaf flush dates and 2 days for leaf coloration dates. Finally, we used this model to produce a global map that distinguishes major differences in regional phenological controls. The model appears sufficiently robust to reconstruct historical variation as well as to forecast future phenological responses to changing climatic conditions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bradford, West Yorkshire : Emerald
    Management of environmental quality 14 (2003), S. 99-107 
    ISSN: 1477-7835
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Economics
    Notes: In the last 50 years, the Mediterranean Basin has experienced a doubling of its population. This demographic growth has been the cause of extensive land use changes that have undermined the ecological stability of large portions of its fragile ecosystems. The population of the Mediterranean countries is expected to grow by another 20 percent in the next 25 years, further increasing the pressure on the natural resources. In this paper, we present a methodology combining photosynthetic activity and human settlements both derived from satellite data for monitoring the effects of human settlements on the environment. We found photosynthesis decreasing as one moves from rural to urban settings in the north and increasing in the south Mediterranean countries. Regional scale assessments using this approach may help policy makers in designing appropriate measures to combat further environmental degradation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Climatic change 31 (1995), S. 395-413 
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Land cover is a crucial, spatially and temporally varying component of global carbon and climate systems. Therefore accurate estimation and monitoring of land cover changes is important in global change research. Although, land cover has dramatically changed over the last few centuries, until now there has been no consistent way of quantifying the changes globally. In this study we used long-term climate, soils data along with coarse resolution satellite observations to quantify the magnitude and spatial extent of global land cover changes due to anthropogenic processes. Differences between potential leaf area index, derived from climate-soil-leaf area equilibrium and actual leaf area index obtained from satellite data were used to estimate changes in land cover. Forest clearing for agriculture and irrigated farming in arid and semi-arid lands are found to be two major sources of climatically important land cover changes. Satellite derived Spectral Vegetation indices (SV I) and surface temperatures (T s) show strong impact of land cover changes on climatic processes. Irrigated agriculture in dry areas increased energy absorption and evapotranspiration (ET) compared to natural vegetation. On the other hand, forest clearing for crops decreased energy absorption andET. A land cover classification and monitoring system is proposed using satellite derivedSV I andT s that simultaneously characterize energy absorption and exchange processes. This completely remote sensing based approach is useful for monitoring land cover changes as well as their impacts on climate. Monitoring the spatio-temporal dynamics of land cover is possible with current operational satellites, and could be substantially improved with the Earth Observing System (EOS) era satellite sensors.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The projected response of coniferous forests to a climatic change scenario of doubled atmospheric CO2, air temperature of +4 °C, and +10% precipitation was studied using a computer simulation model of forest ecosystem processes. A topographically complex forested region of Montana was simulated to study regional climate change induced forest responses. In general, increases of 10–20% in LAI, and 20–30% in evapotranspiration (ET) and photosynthesis (PSN) were projected. Snowpack duration decreased by 19–69 days depending on location, and growing season length increased proportionally. However, hydrologic outflow, primarily fed by snowmelt in this region, was projected to decrease by as much as 30%, which could virtually dry up rivers and irrigation water in the future. To understand the simulated forest responses, and explore the extent to which these results might apply continentally, seasonal hydrologic partitioning between outflow and ET, PSN, respiration, and net primary production (NPP) were simulated for two contrasting climates of Jacksonville, Florida (hot, wet) and Missoula, Montana (cold, dry). Three forest responses were studied sequentially from; climate change alone, addition of CO2 induced tree physiological responses of-30% stomatal conductance and +30% photosynthetic rates, and finally with a reequilibration of forest leaf area index (LAI), derived by a hydrologic equilibrium theory. NPP was projected to increase 88%, and ET 10%, in Missoula, MT, yet dcrease 5% and 16% respectively for Jacksonville, FL, emphasizing the contrasting forest responses possible with future climatic change.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 1997-11-01
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 7
    Publication Date: 1987-06-01
    Description: A model for calculating daily microclimate conditions in mountainous terrain is presented. Maximum–minimum daily air temperatures, precipitation, and dew point are extrapolated from valley stations to adjacent mountain slopes, after making elevation- and aspect-related corrections. The model (MT-CLIM) produces estimates of daily incoming shortwave radiation, air temperature, humidity and vapor pressure deficit, and precipitation for any mountain study site. MT-CLIM was tested against measured meteorological data on six study sites consisting of three north–south slope pairs in western Montana. Correlations between predicted and observed daily conditions on the six study sites for the period April–November 1983 were air temperature, R2 = 0.88–0.92 with standard errors
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 8
    Publication Date: 2015-12-30
    Print ISSN: 0256-1530
    Electronic ISSN: 1861-9533
    Topics: Geosciences , Physics
    Published by Springer
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  • 9
    Publication Date: 2020-04-17
    Description: GeoNEX is a collaborative project led by scientists from NASA, NOAA, and many other institutes around the world to generate Earth monitoring products using data streams from the latest Geostationary (GEO) sensors including the GOES-16/17 Advanced Baseline Imager (ABI), the Himawari-8/9 Advanced Himawari Imager (AHI), and more. An accurate and consistent product of the Top-Of-Atmosphere (TOA) reflectance and brightness temperature is the starting point in the scientific processing pipeline and has significant influences on the downstream products. This paper describes the main steps and the algorithms in generating the GeoNEX TOA products, starting from the conversion of digital numbers to physical quantities with the latest radiometric calibration information. We implement algorithms to detect and remove residual georegistration uncertainties automatically in both GOES and Himawari L1bdata, adjust the data for topographic relief, estimate the pixelwise data-acquisition time, and accurately calculate the solar illumination angles for each pixel in the domain at every time step. Finally, we reproject the TOA products to a globally tiled common grid in geographic coordinates in order to facilitate intercomparisons and/or synergies between the GeoNEX products and existing Earth observation datasets from polar-orbiting satellites.
    Electronic ISSN: 2072-4292
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 10
    Publication Date: 2019-11-21
    Print ISSN: 2150-704X
    Electronic ISSN: 2150-7058
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Published by Taylor & Francis
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