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    New cloud and microphysics parameterisation for use in high-resolution dynamical downscaling: application for summer extreme temperature over Belgium

    Authors
    Hamdi, R.
    , Van de Vyver, H.
    , Termonia, P.
    Discipline
    Earth and related Environmental sciences
    Subject
    dynamical downscaling
    cloud parameterisation
    extreme Temperature
    Generalized Pareto Distribution
    aladin
    Audience
    General Public
    Scientific
    Date
    2012
    Publisher
    IRM
    KMI
    RMI
    Metadata
    Show full item record
    Description
    We explore the use of high-resolution dynamical downscaling as a means to simulate extreme values of summer maximum surface air temperature over Belgium (TMAX). We use the limited area version of the ARPEGE-IFS model, ALADIN. Our approach involves a sequence of daily integrations driven by perfect boundary conditions at the lateral boundaries provided by the ERA40 reanalysis. In this study, three different recent past (1961–1990) simulations are evaluated against different station datasets: (1) 40 km spatial resolution (ALD40), (2) 10 km spatial resolution (ALD10), and (3) 4 km spatial resolution (ALR04) using a new parameterisation of deep convection, and microphysics allowing the use of ALADIN at resolutions ranging from a few tens of kilometers down to less than 4 km. The validation of ALD40 reveals a positive summer bias (2.2 °C), even though the considerable spatial resolution enhancement by a factor of 4, ALD10 reduces slightly the warm biases (1.7 °C). This warm bias on TMAX is strongly correlated with cloud cover representation. Result shows an overestimate of clear-sky occurrences by ALD10 and a developing solar radiation overestimate through the diurnal cycle, with 116 W m−2 maximum overestimate at noon. ALR04 reduces considerably the warm biases (−0.2 °C) which suggests of its ability to simulate weakly forced convective cloud in the summer over Belgium. In addition, the Generalized Pareto Distribution (GPD) of the extreme high temperatures produced by the different simulations has been compared to observations of the same period. ALD40 and ALD10 gave a GPD distribution that did not replicate the observed distribution well and, thus, overestimated the extremes. This study shows that the consistent treatment of deep convection and cloud–radiation interaction when increasing the horizontal resolution is very important when studying extremely high temperatures events. Copyright © 2011 Royal Meteorological Society
    Citation
    Hamdi, R.; , Van de Vyver, H.; , Termonia, P. (2012). New cloud and microphysics parameterisation for use in high-resolution dynamical downscaling: application for summer extreme temperature over Belgium. , Issue International Journal of Climatology Vol. 32, 2051–2065, IRM,
    Identifiers
    uri: https://orfeo.belnet.be/handle/internal/8912
    Type
    Article
    Peer-Review
    Not pertinent
    Language
    eng
    Links
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