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Search: WFRF:(Ammann Christof) > (2020-2022)

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1.
  • Lembrechts, Jonas J., et al. (author)
  • Global maps of soil temperature
  • 2022
  • In: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 28:9, s. 3110-3144
  • Journal article (peer-reviewed)abstract
    • Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0–5 and 5–15cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean=3.0±2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6±2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (−0.7±2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications.
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2.
  • Rinne, Janne, et al. (author)
  • Alternative Turbulent Trace Gas Flux Measurement Methods
  • 2021
  • In: Springer Handbook of Atmospheric Measurements. - Cham : Springer International Publishing. - 2522-8706 .- 2522-8692. - 9783030521714 - 9783030521707 ; , s. 1505-1530
  • Book chapter (peer-reviewed)abstract
    • The eddy-covariance (EC) method is the most direct micrometeorological approach to measure the surface–atmosphere trace gases under turbulent conditions. The measurement of trace gas fluxes by eddy covariance requires fast-response instruments (higher than 1 Hz) to measure the turbulent fluctuations of vertical wind velocity and trace gas mixing ratio. For many trace gas species, such fast response analyzers are either not available or do not meet the required precision, long-term stability, and ease of operation under field conditions.Thus, a range of alternative flux measurement techniques have been developed to relax the requirement for fast response time and precision of analysis of the targeted trace gases. These alternative trace gas flux measurement methods are based on surface layer gradients, eddy accumulation, and disjunct eddy-covariance approaches. Of these, the two latter are presented in this chapter. In addition, the surface layer renewal approach,which can be used to understand turbulent exchange processes, and the nocturnal boundary layer Keeling plot approach for determination of the isotopic composition of emitted gases under stable conditions are also described.
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