Initial conditions

Sensitivity experiments

Impact of the improved diurnal cycle of convection

Namelist block NAMCUMF, parameter RCAPDCYCL

RCAPDCYCL = 2 (default) activates the diurnal cycle using sub-cloud CAPE,

RCAPDCYCL = 1 diurnal cycle using surface sensible heat flux,

RCAPDCYCL = 0 reverts the code to a setting before the diurnal cycle for convection was

implemented.

Look at the timing of convective and precipitation events.

Optimization factor for the time scale adjustment:

Namelist block NAMCUMF, parameter RTAUA

RTAUA=1. default value (set it to 0.33 and 3.)

The ratio between the actual cloud base mass flux and the unit (initial) cloud base mass flux:

Look at the amplitude of precipitation.

\frac{M_{base}}{M^*_{base}} = \frac{PCAPE - PCAPE_{bl}}{\tau}

Further reading

201404 - Convection - Arkansas U.S

Comments

The forecasting system at ECMWF makes use of "ensembles" of forecasts to account for errors in the initial state. In reality, the forecast depends on the initial state in a much more complex way than just the model resolution or starting date.  At ECMWF many initial states are created for the same starting time by use of "singular vectors" and "ensemble data assimilation" techniques which change the vertical structure of the initial perturbations.

As further reading and an extension of this case study, research how these methods work.

Acknowledgements

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