The Experts below are selected from a list of 132 Experts worldwide ranked by ideXlab platform

Oliver Schlenczek - One of the best experts on this subject based on the ideXlab platform.

  • the origins of ice crystals measured in mixed phase clouds at the high alpine site jungfraujoch
    Atmospheric Chemistry and Physics, 2015
    Co-Authors: Gary Lloyd, T W Choularton, K N Bower, M W Gallagher, Paul Connolly, Michael Flynn, Robert Farrington, Jonathan Crosier, Oliver Schlenczek
    Abstract:

    Abstract. During the winter of 2013 and 2014 measurements of cloud microphysical properties over a 5-week period at the high-alpine site Jungfraujoch, Switzerland, were carried out as part of the Cloud Aerosol Characterisation Experiments (CLACE) and the Ice Nucleation Process Investigation and Quantification project (INUPIAQ). Measurements of aerosol properties at a second, lower site, Schilthorn, Switzerland, were used as input for a primary ice nucleation scheme to predict ice nuclei concentrations at Jungfraujoch. Frequent, rapid transitions in the ice and liquid properties of the clouds at Jungfraujoch were identified that led to large fluctuations in ice mass fractions over temporal scales of seconds to hours. During the measurement period we observed high concentrations of ice particles that exceeded 1000 L−1 at temperatures around −15 °C, verified by multiple instruments. These concentrations could not be explained using the usual primary ice nucleation schemes, which predicted ice nucleus concentrations several orders of magnitude smaller than the peak ice crystal number concentrations. Secondary ice production through the Hallett–Mossop process as a possible explanation was ruled out, as the cloud was rarely within the active temperature range for this process. It is shown that other mechanisms of secondary ice particle production cannot explain the highest ice particle concentrations. We describe four possible mechanisms that could lead to high cloud ice concentrations generated from the snow-covered surfaces surrounding the measurement site. Of these we show that Hoar Frost crystals generated at the cloud enveloped snow surface could be the most important source of cloud ice concentrations. Blowing snow was also observed to make significant contributions at higher wind speeds when ice crystal concentrations were

Thomas Putz - One of the best experts on this subject based on the ideXlab platform.

  • determining dew and Hoar Frost formation for a low mountain range and alpine grassland site by weighable lysimeter
    Journal of Hydrology, 2018
    Co-Authors: Jannis Groh, Veronika Slawitsch, Markus Herndl, Alexander Graf, Harry Vereecken, Thomas Putz
    Abstract:

    Abstract Non-rainfall events like dew or Hoar Frost formation are often neglected in the water budget, because either assumed to be too small or their determination requires time consuming and difficult measurements. These events supply in many dryland ecosystems a substantial amount of water, but their role for northern humid ecosystems is largely unknown. There is a general need to quantify the ecological relevance for ecosystems of the water amount from dew and Hoar Frost formation. Weighable precision lysimeters were used to determine dew and Hoar Frost formation for a low mountain range and alpine grassland site for the hydrological years 2013–2015. Together dew and Hoar Frost formation ranged on a yearly basis between 42.1 and 67.7 mm, which corresponds to 4.2–6% of the total annual amount of precipitation. In drier months dew and Hoar Frost contributed up to 16.1% of total monthly precipitation amount. In winter months dew and Hoar Frost formation contributed up to 38% to the total monthly precipitation amount. Our investigation suggests, that dew and Hoar Frost formation are of ecological importance during droughts as well as cold periods. The amounts and seasonal patterns of dew and Hoar Frost formation could be predicted relatively well, based on standard meteorological variables with the Penman-Monteith equation. However, our results also showed, that the surface energy balance model from Penman-Monteith underestimated the amount of dew and Hoar Frost during colder periods and specific meteorological site conditions (i.e. high wind speeds at night). The mean underestimation between calculated and measured dew and Hoar Frost on a yearly scale were 63.2% and 16.6% at Rollesbroich and Gumpenstein, respectively. Dew and Hoar Frost formation contributes substantially to the water budgets of a low mountain range and alpine grassland.

  • Lysimeters in Vadose Zone Research
    'Soil Science Society of America', 2018
    Co-Authors: Thomas Putz, Johann Fank, Markus Flury
    Abstract:

    Lysimeters are methodological experimental tools to study the water and matter fluxes in the vadose zone, as well as the environmental fate of chemicals. Lysimeters are available in various types. The most sophisticated lysimeters are filled monolithically, are equipped with a pressure-controlled lower boundary, and are weighable, allowing the measurement of hydraulic fluxes, i.e., rainfall, drainage, evapotranspiration, dew, and Hoar Frost with high precision. This special section of reports on current lysimeter research

Gary Lloyd - One of the best experts on this subject based on the ideXlab platform.

  • the origins of ice crystals measured in mixed phase clouds at the high alpine site jungfraujoch
    Atmospheric Chemistry and Physics, 2015
    Co-Authors: Gary Lloyd, T W Choularton, K N Bower, M W Gallagher, Paul Connolly, Michael Flynn, Robert Farrington, Jonathan Crosier, Oliver Schlenczek
    Abstract:

    Abstract. During the winter of 2013 and 2014 measurements of cloud microphysical properties over a 5-week period at the high-alpine site Jungfraujoch, Switzerland, were carried out as part of the Cloud Aerosol Characterisation Experiments (CLACE) and the Ice Nucleation Process Investigation and Quantification project (INUPIAQ). Measurements of aerosol properties at a second, lower site, Schilthorn, Switzerland, were used as input for a primary ice nucleation scheme to predict ice nuclei concentrations at Jungfraujoch. Frequent, rapid transitions in the ice and liquid properties of the clouds at Jungfraujoch were identified that led to large fluctuations in ice mass fractions over temporal scales of seconds to hours. During the measurement period we observed high concentrations of ice particles that exceeded 1000 L−1 at temperatures around −15 °C, verified by multiple instruments. These concentrations could not be explained using the usual primary ice nucleation schemes, which predicted ice nucleus concentrations several orders of magnitude smaller than the peak ice crystal number concentrations. Secondary ice production through the Hallett–Mossop process as a possible explanation was ruled out, as the cloud was rarely within the active temperature range for this process. It is shown that other mechanisms of secondary ice particle production cannot explain the highest ice particle concentrations. We describe four possible mechanisms that could lead to high cloud ice concentrations generated from the snow-covered surfaces surrounding the measurement site. Of these we show that Hoar Frost crystals generated at the cloud enveloped snow surface could be the most important source of cloud ice concentrations. Blowing snow was also observed to make significant contributions at higher wind speeds when ice crystal concentrations were

Jannis Groh - One of the best experts on this subject based on the ideXlab platform.

  • determining dew and Hoar Frost formation for a low mountain range and alpine grassland site by weighable lysimeter
    Journal of Hydrology, 2018
    Co-Authors: Jannis Groh, Veronika Slawitsch, Markus Herndl, Alexander Graf, Harry Vereecken, Thomas Putz
    Abstract:

    Abstract Non-rainfall events like dew or Hoar Frost formation are often neglected in the water budget, because either assumed to be too small or their determination requires time consuming and difficult measurements. These events supply in many dryland ecosystems a substantial amount of water, but their role for northern humid ecosystems is largely unknown. There is a general need to quantify the ecological relevance for ecosystems of the water amount from dew and Hoar Frost formation. Weighable precision lysimeters were used to determine dew and Hoar Frost formation for a low mountain range and alpine grassland site for the hydrological years 2013–2015. Together dew and Hoar Frost formation ranged on a yearly basis between 42.1 and 67.7 mm, which corresponds to 4.2–6% of the total annual amount of precipitation. In drier months dew and Hoar Frost contributed up to 16.1% of total monthly precipitation amount. In winter months dew and Hoar Frost formation contributed up to 38% to the total monthly precipitation amount. Our investigation suggests, that dew and Hoar Frost formation are of ecological importance during droughts as well as cold periods. The amounts and seasonal patterns of dew and Hoar Frost formation could be predicted relatively well, based on standard meteorological variables with the Penman-Monteith equation. However, our results also showed, that the surface energy balance model from Penman-Monteith underestimated the amount of dew and Hoar Frost during colder periods and specific meteorological site conditions (i.e. high wind speeds at night). The mean underestimation between calculated and measured dew and Hoar Frost on a yearly scale were 63.2% and 16.6% at Rollesbroich and Gumpenstein, respectively. Dew and Hoar Frost formation contributes substantially to the water budgets of a low mountain range and alpine grassland.

Jonathan Crosier - One of the best experts on this subject based on the ideXlab platform.

  • the origins of ice crystals measured in mixed phase clouds at the high alpine site jungfraujoch
    Atmospheric Chemistry and Physics, 2015
    Co-Authors: Gary Lloyd, T W Choularton, K N Bower, M W Gallagher, Paul Connolly, Michael Flynn, Robert Farrington, Jonathan Crosier, Oliver Schlenczek
    Abstract:

    Abstract. During the winter of 2013 and 2014 measurements of cloud microphysical properties over a 5-week period at the high-alpine site Jungfraujoch, Switzerland, were carried out as part of the Cloud Aerosol Characterisation Experiments (CLACE) and the Ice Nucleation Process Investigation and Quantification project (INUPIAQ). Measurements of aerosol properties at a second, lower site, Schilthorn, Switzerland, were used as input for a primary ice nucleation scheme to predict ice nuclei concentrations at Jungfraujoch. Frequent, rapid transitions in the ice and liquid properties of the clouds at Jungfraujoch were identified that led to large fluctuations in ice mass fractions over temporal scales of seconds to hours. During the measurement period we observed high concentrations of ice particles that exceeded 1000 L−1 at temperatures around −15 °C, verified by multiple instruments. These concentrations could not be explained using the usual primary ice nucleation schemes, which predicted ice nucleus concentrations several orders of magnitude smaller than the peak ice crystal number concentrations. Secondary ice production through the Hallett–Mossop process as a possible explanation was ruled out, as the cloud was rarely within the active temperature range for this process. It is shown that other mechanisms of secondary ice particle production cannot explain the highest ice particle concentrations. We describe four possible mechanisms that could lead to high cloud ice concentrations generated from the snow-covered surfaces surrounding the measurement site. Of these we show that Hoar Frost crystals generated at the cloud enveloped snow surface could be the most important source of cloud ice concentrations. Blowing snow was also observed to make significant contributions at higher wind speeds when ice crystal concentrations were