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Matthey-De-L'Endroit, Renaud

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Matthey-De-L'Endroit, Renaud
Affiliation principale
Fonction
Ancien.ne collaborateur.trice
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https://libra.unine.ch/handle/123456789/491

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  • Publication
    Accès libre
    Frequency of Boundary-Layer-Top Fluctuations in Convective and Stable Conditions Using Laser Remote Sensing
    (2010)
    Martucci, Giovanni
    ;
    Matthey-De-L'Endroit, Renaud 
    ;
    Mitev, Valentin
    ;
    Richner, Hans
    The planetary boundary-layer (PBL) height is determined with high temporal and altitude resolution from lidar backscatter profiles. Then, the frequencies of daytime thermal updrafts and downdrafts and of nighttime gravity waves are obtained applying a fast Fourier transform on the temporal fluctuation of the PBL height. The principal frequency components of each spectrum are related to the dominant processes occurring at the daytime and nighttime PBL top. Two groups of cases are selected for the study: one group combines daytime cases, measured in weak horizontal wind conditions and dominated by convection. The cases show higher updraft and downdraft frequencies for the shallow, convective boundary layer and lower frequencies for a deep PBL. For cases characterized by strong horizontal winds, the frequencies directly depend on the wind speed. The temporal variation of the PBL height is determined also in the likely presence of lee waves. For nighttime cases, the main frequency components in the spectra do not show a real correlation with the nocturnal PBL height. Altitude fluctuations of the top of the nocturnal boundary layer are observed even though the boundary layer is statically stable. These oscillations are associated with the wind shear effect and with buoyancy waves at the PBL top.
  • Publication
    Accès libre
    Comparison between Backscatter Lidar and Radiosonde Measurements of the Diurnal and Nocturnal Stratification in the Lower Troposphere
    (2007)
    Martucci, Giovanni
    ;
    Matthey-De-L'Endroit, Renaud 
    ;
    Mitev, Valentin
    ;
    Richner, Hans
    A collection of boundary layer heights has been derived from measurements performed by a ground-based backscatter lidar in Neuchâtel, Switzerland (47.000°N, 6.967°E, 485 m ASL). A dataset of 98 cases have been collected during 2 yr. From these data, 61 are noon and 37 are midnight cases. The following two different schemes were used to retrieve the mixed layer depth and the height of the residual layer from the measurements: the gradient and variance methods. The obtained values were compared with those derived from the potential temperature profiles as computed from radiosonde data. For nocturnal cases, the height of the first aerosol layer above the residual layer was also compared to the corresponding potential temperature value. Correlation coefficients between lidar and radiosonde in both convective and stable conditions are between 0.88 and 0.97.