[Eoas-seminar] Seminar by Dr. Jean-François on Monday, Sep. 17, 3:30 PM, Love 353

eoas-seminar at lists.fsu.edu eoas-seminar at lists.fsu.edu
Wed Sep 12 20:14:17 EDT 2018


Hi All,


The following is an MET seminar announcement:


Speaker:     Dr. Guérémy Jean-François

Time:           3:30 PM, Monday, Sep. 17

Location:     Love 353


Title:     A continuous and prognostic convection scheme based on buoyancy, PCMT. Formulation, and one to three-dimensional evaluation and sensitivity


Abstract:

A new and consistent convection scheme (PCMT: Prognostic Condensates Microphysics and
Transport, implemented in Météo-France large-scale models) providing a continuous and prognostic
treatment of this atmospheric process, is described. The main concept ensuring the consistency of
the whole system is the buoyancy, key element of any vertical motion. The buoyancy constitutes the
forcing term of the convective vertical velocity, which is then used to define the triggering
condition, the mass flux, and the rates of entrainment-detrainment. The buoyancy is also used in its
vertically integrated form (CAPE) to determine the closure condition. The continuous treatment of
convection, from dry thermals to deep precipitating convection, is achieved with the help of a
continuous formulation of the entrainment-detrainment rates (depending on the convective vertical
velocity) and of the CAPE relaxation time (depending on the convective over-turning time). The
convective tendencies are directly expressed in terms of condensation and transport. Finally, the
convective vertical velocity and condensates are fully prognostic, the latter being treated using the
same microphysics scheme as for the resolved condensates but considering the convective
environment.
A Single Column Model (SCM) validation of this scheme is shown, allowing detailed comparisons
with observed and explicitly simulated data. Five cases covering the convective spectrum are
considered: over ocean, deep precipitating convection (TOGA), sensitivity to environmental
moisture from non precipitating shallow convection to deep precipitating convection (idealized
case), trade wind shallow convection (BOMEX) and diurnal cycle of strato-cumulus (FIRE),
together with an entire continental diurnal cycle of convection (ARM). The three former cases are
used to define the optimal scheme parameters, considering among them the maximum turbulent
entrainment and the solid auto-conversion rates as the basis of two sensitivity experiments carried
out all along the evaluation assessment; the two latter cases are studied to perform a first evaluation.
Then, a 3D LAM evaluation sensitivity study is presented considering a West African AMMA case
with both observations and a CRM simulation using the same initial and lateral conditions as for the
parameterized one. Finally, a global evaluation and sensitivity (entrainment and precipitation
efficiency) is shown in coupled climate mode, considering mean climate, intraseasonal variability
(diurnal cycle, distribution of daily precipitation and outgoing long-wave radiation intraseasonal
variability) and interannual variability.

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