COSMO implementations at CNMCA: tests with different dinamycal options. Lucio TORRISI Italian Met. Service CNMCA – Pratica di Mare (Rome) firstname.lastname@example.org. Overview. COSMO implementations at CNMCA New reference atmosphere impact 7km RK/LF comparison RKold (previous to 4.9) RK4.9
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Italian Met. Service CNMCA – Pratica di Mare (Rome)
CNMCA NWP System dinamycal options
Zaengl (2008) implemented in COSMO model a new reference atmosphere based on a temperature profile which starts with a prescribed sea-level temperature and exponentially approaches an isothermal stratosphere. In this way there is no limitation on vertical extent of model domain.
New reference atmosphere dinamycal options
Pressure bias problem (1) dinamycal options
1) RK/LF core - Objective verification showed a difference in MSLP bias behaviour between 7km RK (red line) and LF (green line)runs.
MSLP bias difference increases with forecast time. RK runs have a larger bias, typically positive, leading to a worse RMSE.
7km LF: MSLP bias dinamycal options
7km LF/RKold: MSLP bias dinamycal options
7km RK4.9/LF comparison dinamycal options
In COSMO 4.9 a more accurate discretization of the metric terms was introduced by G. Zaengl.
7km LF/RK: MSLP bias dinamycal options
Vertical advection in COSMO
2.8km RK4.9 IVA/EVA compar. dinamycal options
Thank you for your attention! dinamycal options
Pressure bias problem (2) dinamycal options
2) Domain size - Objective verification showed a difference in MSLP bias behaviour in 7km RK (and LF) runs having a different domain size (smaller one - red line, larger one -green line).
The larger domain, the greater MSLP bias
Pressure bias problem (3) dinamycal options
3) Model formulation - Objective verification showed a difference in MSLP bias behaviour between 14km COSMO LF/RK (blue line) and HRM (red line) runs.
HRM is the DWD regional hydrostatic model (LF time integration scheme) used in the CNMCA assimilation systems (3D-Var PSAS and LETKF).
MSLP bias difference increases with forecast time (COSMO larger positive bias)