15,001 research outputs found
Multiyear eddy covariance and meteorological dataset from agroforestry and open cropland or grassland in northern Germany
No full textDataset corresponding to the project SIGNAL (Sustainable intensification of agriculture through agroforestry), subproject TP1.2, entitled "CO2, H2O and energy exchange". Christian Markwitz collected and processed the data corresponding to the 1st phase, 2016-2018. Justus van Ramshorst collected and processed the data corresponding to the 2nd phase, 2019-2021. José Ángel Callejas-Rodelas collected and processed the data corresponding to the 3rd phase, 2022-2024. Lukas Siebicke and Alexander Knohl wrote the project proposals and contributed to data analysis and harmonization. Project funded by the German Ministry of Education and Research (BMBF), project BonaRes, module A (first phase: SIGNAL 031A562A, second phase: SIGNAL 031B0510A, third phase: SIGNAL 031B1063A)
Kohlendioxid-, Wasserdampf- und Waermeaustausch eines durch Windwurf gestoerten Waldoekosystems in der west-russischen Taiga
No full textWater vapor 2H and 18O measurements using off-axis integrated cavity output spectroscopy
No full textWe present a detailed assessment of a commercially available water vapor isotope analyzer (WVIA, Los Gatos Research, Inc.) for simultaneous in-situ measurements of 2H and 18O in water vapor. This method, based on off-axis integrated cavity output spectroscopy, 5 is an alternative to the conventional water trap/isotope ratio mass spectrometry (IRMS) techniques. We evaluate the analyzer in terms of precision, memory effects, concentration dependence, temperature sensitivity and long-term stability. A calibration system based on ink jet technology is used to characterize the performance and to calibrate the analyzer. Our results show that the precision at an averaging 10 time of 15 s is 0.16‰ for 2H and 0.08‰ for 18O. The isotope ratios are strongly dependent on the water mixing ratio of the air. Taking into account this concentration dependence as well as the temperature sensitivity of the instrument we obtained a long-term stability of the water isotope measurements of 0.38‰ for 2H and 0.25‰ for 18O. The accuracy of the WVIA was further assessed by comparative measure15 ments using IRMS and a dew point generator indicating a linear response in isotopic composition and H2O concentrations. The WVIA combined with a calibration system provides accurate high resolution water vapor isotope measurements and opens new possibilities for hydrological and ecological applications
Water vapor delta H-2 and delta O-18 measurements using off-axis integrated cavity output spectroscopy
No full textWe present a detailed assessment of a commercially available water vapor isotope analyzer (WVIA, Los Gatos Research, Inc.) for simultaneous in-situ measurements of delta H-2 and delta O-18 in water vapor. This method, based on off-axis integrated cavity output spectroscopy, is an alternative to the conventional water trap/isotope ratio mass spectrometry (IRMS) techniques. We evaluate the analyzer in terms of precision, memory effects, concentration dependence, temperature sensitivity and long-term stability. A calibration system based on a droplet generator is used to characterize the performance and to calibrate the analyzer. Our results show that the precision at an averaging time of 15 s is 0.16 parts per thousand for delta H-2 and 0.08 parts per thousand for delta O-18. The isotope ratios are strongly dependent on the water mixing ratio of the air. Taking into account this concentration dependence as well as the temperature sensitivity of the instrument we obtained a long-term stability of the water isotope measurements of 0.38 parts per thousand for delta H-2 and 0.25 parts per thousand for delta O-18. The accuracy of the WVIA was further assessed by comparative measurements using IRMS and a dew point generator indicating a linear response in isotopic composition and H2O concentrations. The WVIA combined with a calibration system provides accurate high resolution water vapor isotope measurements and opens new possibilities for hydrological and ecological applications.EC [MEXT-CT-2006-042268
Water vapor delta H-2 and delta O-18 measurements using off-axis integrated cavity output spectroscopy
No full textWe present a detailed assessment of a commercially available water vapor isotope analyzer (WVIA, Los Gatos Research, Inc.) for simultaneous in-situ measurements of delta H-2 and delta O-18 in water vapor. This method, based on off-axis integrated cavity output spectroscopy, is an alternative to the conventional water trap/isotope ratio mass spectrometry (IRMS) techniques. We evaluate the analyzer in terms of precision, memory effects, concentration dependence, temperature sensitivity and long-term stability. A calibration system based on a droplet generator is used to characterize the performance and to calibrate the analyzer. Our results show that the precision at an averaging time of 15 s is 0.16 parts per thousand for delta H-2 and 0.08 parts per thousand for delta O-18. The isotope ratios are strongly dependent on the water mixing ratio of the air. Taking into account this concentration dependence as well as the temperature sensitivity of the instrument we obtained a long-term stability of the water isotope measurements of 0.38 parts per thousand for delta H-2 and 0.25 parts per thousand for delta O-18. The accuracy of the WVIA was further assessed by comparative measurements using IRMS and a dew point generator indicating a linear response in isotopic composition and H2O concentrations. The WVIA combined with a calibration system provides accurate high resolution water vapor isotope measurements and opens new possibilities for hydrological and ecological applications.EC [MEXT-CT-2006-042268
Water vapor 2H and 18O measurements using off-axis integrated cavity output spectroscopy
No full textWe present a detailed assessment of a commercially available water vapor isotope analyzer (WVIA, Los Gatos Research, Inc.) for simultaneous in-situ measurements of 2H and 18O in water vapor. This method, based on off-axis integrated cavity output spectroscopy, 5 is an alternative to the conventional water trap/isotope ratio mass spectrometry (IRMS) techniques. We evaluate the analyzer in terms of precision, memory effects, concentration dependence, temperature sensitivity and long-term stability. A calibration system based on ink jet technology is used to characterize the performance and to calibrate the analyzer. Our results show that the precision at an averaging 10 time of 15 s is 0.16‰ for 2H and 0.08‰ for 18O. The isotope ratios are strongly dependent on the water mixing ratio of the air. Taking into account this concentration dependence as well as the temperature sensitivity of the instrument we obtained a long-term stability of the water isotope measurements of 0.38‰ for 2H and 0.25‰ for 18O. The accuracy of the WVIA was further assessed by comparative measure15 ments using IRMS and a dew point generator indicating a linear response in isotopic composition and H2O concentrations. The WVIA combined with a calibration system provides accurate high resolution water vapor isotope measurements and opens new possibilities for hydrological and ecological applications
Partitioning the net CO2 flux of a deciduous forest into respiration and assimilation using stable carbon isotopes
No full textPartitioning net ecosystem CO2 fluxes measured by the eddy covariance technique into their components assimilation and respiration is crucial for predicting future responses and feedbacks of ecosystems to a changing climate. On the basis of an isotopic approach with C-13, we partitioned the daytime net CO2 fluxes of a deciduous forest in central Germany into assimilation and respiration fluxes over a period of 3 weeks. This is the first attempt so far to quantify component fluxes with stable isotopes over the period of 3 weeks, enabling us to investigate the impact of environmental factors on the partitioned fluxes. Large variability in environmental conditions during the 3-week measurement campaign led to strong changes in isotopic disequilibrium between assimilation and respiration, ranging from 1 to 5%. Although this approach is still associated with large uncertainty, we found reasonable patterns in ecosystem respiration and assimilation, and a significant correlation of daytime respiration with soil temperature (R-2 = 0.48). The ratio of respiration to assimilation was highly variable on a day-to-day basis, ranging from 10% to more than 25%. This ratio was mainly controlled by soil temperature (R-2 = 0.61), indicating a strong sensitivity of ecosystem carbon dynamics to temperature changes and higher carbon uptake efficiency during cooler days. [References: 62
Water vapor δ<sup>2</sup>H and δ<sup>18</sup>O measurements using off-axis integrated cavity output spectroscopy
No full textWe present a detailed assessment of a commercially available water vapor
isotope analyzer (WVIA, Los Gatos Research, Inc.) for simultaneous in-situ
measurements of δ2H and δ18O in water vapor. This method, based on off-axis
integrated cavity output spectroscopy, is an alternative to the conventional
water trap/isotope ratio mass spectrometry (IRMS) techniques. We evaluate the
analyzer in terms of precision, memory effects, concentration dependence,
temperature sensitivity and long-term stability. A calibration system based
on a droplet generator is used to characterize the performance and to
calibrate the analyzer. Our results show that the precision at an averaging
time of 15 s is 0.16‰ for δ2H and 0.08‰ for δ18O. The isotope
ratios are strongly dependent on the water mixing ratio of the air. Taking
into account this concentration dependence as well as the temperature
sensitivity of the instrument we obtained a long-term stability of the water
isotope measurements of 0.38‰ for δ2H and 0.25‰ for δ18O. The
accuracy of the WVIA was further assessed by comparative measurements using
IRMS and a dew point generator indicating a linear response in isotopic
composition and H2O concentrations. The WVIA combined with a calibration
system provides accurate high resolution water vapor isotope measurements and
opens new possibilities for hydrological and ecological applications
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