YD
Y. Dufournet
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4 records found
1
Journal article
(2017)
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Lukas Pfitzenmaier, Yann Dufournet, Christine M.H. Unal, Herman W.J. Russchenberg
The interaction of ice crystals with supercooled liquid droplets in mixed-phase clouds leads to an enhanced growth of ice particles. However, such processes are still not clearly understood although they are important processes for precipitation formation in midlatitudes. To better understand how ice particles grow within such clouds, changes in the microphysical parameters of a particle population falling through the cloud have to be analyzed. The Transportable Atmospheric Radar (TARA) can retrieve the full 3D Doppler velocity vector based on a unique three-beam configuration. Using the derived wind information, a new fall streak retrieval technique is proposed so that microphysical changes along those streaks can be studied. The method is based on Doppler measurements only. The shown examples measured during the Analysis of the Composition of Clouds with Extended Polarization Techniques (ACCEPT) campaign demonstrate that the retrieval is able to capture the fall streaks within different cloud systems. These fall streaks can be used to study changes in a single particle population from its generation (at cloud top) until its disintegration. In this study fall streaks are analyzed using radar moments or Doppler spectra. Synergetic measurements with other instruments during ACCEPT allow the detection of liquid layers within the clouds. The estimated microphysical information is used here to get a better understanding of the influence of supercooled liquid layers on ice crystal growth. This technique offers a new perspective for cloud microphysical studies.
...
The interaction of ice crystals with supercooled liquid droplets in mixed-phase clouds leads to an enhanced growth of ice particles. However, such processes are still not clearly understood although they are important processes for precipitation formation in midlatitudes. To better understand how ice particles grow within such clouds, changes in the microphysical parameters of a particle population falling through the cloud have to be analyzed. The Transportable Atmospheric Radar (TARA) can retrieve the full 3D Doppler velocity vector based on a unique three-beam configuration. Using the derived wind information, a new fall streak retrieval technique is proposed so that microphysical changes along those streaks can be studied. The method is based on Doppler measurements only. The shown examples measured during the Analysis of the Composition of Clouds with Extended Polarization Techniques (ACCEPT) campaign demonstrate that the retrieval is able to capture the fall streaks within different cloud systems. These fall streaks can be used to study changes in a single particle population from its generation (at cloud top) until its disintegration. In this study fall streaks are analyzed using radar moments or Doppler spectra. Synergetic measurements with other instruments during ACCEPT allow the detection of liquid layers within the clouds. The estimated microphysical information is used here to get a better understanding of the influence of supercooled liquid layers on ice crystal growth. This technique offers a new perspective for cloud microphysical studies.
Evidence of ice crystal growth within mixed phase clouds along fall streaks
A radar observation case study
Abstract
(2016)
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Lukas Pfitzenmaier, Yann Dufournet, Christine Unal, Herman Russchenberg, Vaugha Phillips
Mixed phase clouds contain both ice particles and super-cooled cloud water droplets in the same volume of air. Currently, one of the main challenges is to observe and understand how ice particles grow by interacting with liquid water within the mixed-phase clouds. In the mid latitudes this process is one of the most efficient processes for precipitation formation. The case study presented here is based on observations obtained with the Transportable Atmospheric RAdar (TARA), S-band precipitation radar profiler, from Delft University of Technology during the Analysis of the Composition of mixed-phase Clouds with Extended Polarization Techniques campaign (ACCEPT) at Cabauw The Netherlands, autumn 2014. The high temporal (3 seconds) and spatial resolutions (21 m) as well as the Doppler and polarimetric capabilities of TARA are used to estimate size and shape information of the measured hydrometeors. In addition, the unique 3 beam configuration of TARA provides 3-D dynamical information within the cloud system. Based on the dynamical information it is possible to retrieve the fall steak signatures of falling ice particles within radar measurements. Those signatures allow to follow particle population from their generation (at cloud top) to their disintegration. So this technique offers a new perspective for cloud microphysical evolution studies. Using retrieved profiles of radar moments and spectral information along the fall streaks, microphysical information are estimated leading to a better understanding of the influence of super-cooled liquid layer on ice crystals growth under ambient conditions. A synergetic setup of instruments during the ACCEPT campaign was used to liquid layers within the cloud system. So several type of ice crystal growth processes could be detected and will be presented and discussed.
...
Mixed phase clouds contain both ice particles and super-cooled cloud water droplets in the same volume of air. Currently, one of the main challenges is to observe and understand how ice particles grow by interacting with liquid water within the mixed-phase clouds. In the mid latitudes this process is one of the most efficient processes for precipitation formation. The case study presented here is based on observations obtained with the Transportable Atmospheric RAdar (TARA), S-band precipitation radar profiler, from Delft University of Technology during the Analysis of the Composition of mixed-phase Clouds with Extended Polarization Techniques campaign (ACCEPT) at Cabauw The Netherlands, autumn 2014. The high temporal (3 seconds) and spatial resolutions (21 m) as well as the Doppler and polarimetric capabilities of TARA are used to estimate size and shape information of the measured hydrometeors. In addition, the unique 3 beam configuration of TARA provides 3-D dynamical information within the cloud system. Based on the dynamical information it is possible to retrieve the fall steak signatures of falling ice particles within radar measurements. Those signatures allow to follow particle population from their generation (at cloud top) to their disintegration. So this technique offers a new perspective for cloud microphysical evolution studies. Using retrieved profiles of radar moments and spectral information along the fall streaks, microphysical information are estimated leading to a better understanding of the influence of super-cooled liquid layer on ice crystals growth under ambient conditions. A synergetic setup of instruments during the ACCEPT campaign was used to liquid layers within the cloud system. So several type of ice crystal growth processes could be detected and will be presented and discussed.
Abstract
(2016)
-
Lukas Pfitzenmaier, Yann Dufournet, Christine Unal, Herman Russchenberg, Vaugha Phillips
Within mixed-phase clouds the interaction of ice crystals with super-cooled liquid water leads to an enhanced growth of the ice particles. The growth of ice particles from mixed-phase interactions is an important process for precipitation formation in the mid-latitudes. However, such a process is still not clearly understood, nowerdays. To understand the ice particle growth within these clouds the microphysical changes of a single particle population falling through the cloud have to be analysed. Using the 3 beam configuration of the Transportable Atmospheric Radar (TARA) we retrieve the full 3-D Doppler velocity vector. This retrieved dynamical information is used to retrieve the path of a single particle population through the measured cloud system – the so called fall streak – so that microphysical changes along those path can be studied. A way to study changes in ice particle microphysics is to analyse radar Doppler spectra. Microphysical changes along the path of a population of ice particles through a mixed-phase cloud can be correlated to changes in the retrieved radar spectrograms. The instrumental synergy setup during the ACCEPT campaign (Analysis of the Composition of Clouds with Extended Polarization Techniques campaign), fall 2014, Cabauw the Netherlands, allows to detect liquid water layers within mixed-phase clouds. Therefore, identified changes within the retrieved spectrograms can be linked to the presence of super-cooled liquid layers. In this work we will explain the backtracking methodology and its use for the interpretation of velocity spectra. The application of this new methodology for ice particle growth process studies within mixed-phase clouds will be discussed.
...
Within mixed-phase clouds the interaction of ice crystals with super-cooled liquid water leads to an enhanced growth of the ice particles. The growth of ice particles from mixed-phase interactions is an important process for precipitation formation in the mid-latitudes. However, such a process is still not clearly understood, nowerdays. To understand the ice particle growth within these clouds the microphysical changes of a single particle population falling through the cloud have to be analysed. Using the 3 beam configuration of the Transportable Atmospheric Radar (TARA) we retrieve the full 3-D Doppler velocity vector. This retrieved dynamical information is used to retrieve the path of a single particle population through the measured cloud system – the so called fall streak – so that microphysical changes along those path can be studied. A way to study changes in ice particle microphysics is to analyse radar Doppler spectra. Microphysical changes along the path of a population of ice particles through a mixed-phase cloud can be correlated to changes in the retrieved radar spectrograms. The instrumental synergy setup during the ACCEPT campaign (Analysis of the Composition of Clouds with Extended Polarization Techniques campaign), fall 2014, Cabauw the Netherlands, allows to detect liquid water layers within mixed-phase clouds. Therefore, identified changes within the retrieved spectrograms can be linked to the presence of super-cooled liquid layers. In this work we will explain the backtracking methodology and its use for the interpretation of velocity spectra. The application of this new methodology for ice particle growth process studies within mixed-phase clouds will be discussed.