Adrian Lock
UK Met. Office
To the casual observer, stratocumulus is a dull grey slab of a cloud
which has an irritating habit of hanging around for days on end doing
nothing more exciting that drizzle in a depressingly persistent way,
especially in England. It is this persistence and significant impact
on the radiation budget, however, that make it of importance both to
climate modeling and weather forecasting.
Numerical modeling of stratocumulus is complicated by the
interaction between strong cloud-top radiative cooling and turbulent
mixing which occurs just beneath a transition, often over just a few
metres, to much warmer and drier air. This talk will describe the
development of the UK Met Office boundary layer scheme, which allows
these processes to interact in a realistic way on the relatively coarse
vertical grids used in NWP, and illustrate its performance with
results from the climate model. Results will also be presented from
vertical column model tests of both the Met Office scheme and the RPN
moist TKE boundary layer scheme for a case of marine stratocumulus.
These illustrate the usefulness of such a simplified environment for
identifying weaknesses in parametrizations and testing solutions.