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Chapter 5. Convection
IFS documentation Front Page
Chapter 1. Overview
Chapter 2. Radiation
Chapter 3. Turbulent diffusion and interactions with the surface
Chapter 4. Subgrid-scale orographic drag
Chapter 5. Convection
Chapter 6. Clouds and large-scale precipitation
Chapter 7. Land suface parametrization
Chapter 8. Methane oxidation
Chapter 9. Climatological data
REFERENCES
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5.5 Sub-cloud layer
The first level at which convective mass, momentum and thermodynamic fluxes are estimated is cloud base. To represent the effects of convective updraughts on the sub-cloud layer a simple scaling of cloud base fluxes is applied in which they decrease to zero at the surface through the sub-cloud layer.
Care must be taken to ensure that fluxes of liquid water are zero below cloud base. Through the cloud base level an interpolation of fluxes liquid water static energy and total water content is used to estimate fluxes of dry static energy and water vapour mixing ratio in the level immediately below cloud base;
|
(5.27) |
where
refers to the value of 
at the level
immediately below cloud base. 
is given by
|
(5.28) |
and
is the surface pressure.For deep and shallow convection
is set to 1 (implying a linear decrease
in the flux with pressure below cloud base) while for mid-level convection
is equal to 2 (implying a quadratic reduction
in flux below cloud base).For the remainder of the sub-cloud layer, fluxes at level `B+1' are reduced to zero at the surface using
recomputed
as
|
(5.29) |
where
is the pressure at level 
of the model.
The cloud-mass and momentum fluxes in the sub-cloud layer are treated in a similar manner.
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05.04.2002 |
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