Proceedings - C-SRNWP Project

Cycle Date Model change and impact
U4.03 11 Oct 2005 UM version upgraded to UM6.1
Targeted moisture diffusion instead of horizontal
moisture diffusion. (change reversed in cycle U4.04)
Empirically adjusted cloud fraction introduced - removes
negative cloud bias.
Convection upgrade to 4A - improves precipitation
Microphysics upgrade to 3D & revised autoconversion
coefficients: reduces excessive light precipitation.
Change in orography blending weights: Improve
consistency of orography in LBC rim area.
U4.04 13 Dec 2005 Introduce 3D-Var and an Analysis Correction scheme
for cloud and precipitation
4 main runs at 03, 09, 15 and 21 UTC
Introduce gravity wave drag
Replace targeted diffusion with horizontal diffusion
Add water loading term as the specific humidity based
dynamics does not consider the weight of precipitation
products in the density.
U4.05 14 Mar 2006 Mixing ratio replaces specific humidity in dynamics
Include anthropogenic urban heat source
U4.06 14 Jun 2006 Extension of domain to cover Shetlands
Correction of MOPS cloud height
U4.07 26 Sep 2006 Two small changes to the assimilation of radar data by
Latent Heat Nudging (LHN):
1) The scale for horizontal filtering of temperature
increments reduced from 21km to 6km.
2) The derivation of increments from sections of the
model profile below cloud base, where evaporation is
taking place is removed.
The northward extension of the model domain allows a better representation of showers
around Scotland in a northerly airstream as shown in Figure 7.
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