<s>
Parameterization	O
in	O
a	O
weather	B-Application
or	O
climate	B-Application
model	I-Application
is	O
a	O
method	O
of	O
replacing	O
processes	O
that	O
are	O
too	O
small-scale	O
or	O
complex	O
to	O
be	O
physically	O
represented	O
in	O
the	O
model	O
by	O
a	O
simplified	O
process	O
.	O
</s>
<s>
Weather	B-Application
and	O
climate	B-Application
model	I-Application
gridboxes	O
have	O
sides	O
of	O
between	O
and	O
.	O
</s>
<s>
Weather	B-Application
models	O
that	O
have	O
gridboxes	O
with	O
sides	O
between	O
and	O
can	O
explicitly	O
represent	O
convective	O
clouds	O
,	O
although	O
they	O
still	O
need	O
to	O
parameterize	O
cloud	O
microphysics	O
.	O
</s>
<s>
Rather	O
than	O
assuming	O
that	O
clouds	O
form	O
at	O
100%	O
relative	O
humidity	O
,	O
the	O
cloud	B-Application
fraction	I-Application
can	O
be	O
related	O
to	O
a	O
critical	O
relative	O
humidity	O
of	O
70%	O
for	O
stratus-type	O
clouds	O
,	O
and	O
at	O
or	O
above	O
80%	O
for	O
cumuliform	O
clouds	O
,	O
reflecting	O
the	O
sub	O
grid	O
scale	O
variation	O
that	O
would	O
occur	O
in	O
the	O
real	O
world	O
.	O
</s>
<s>
Most	O
climate	B-Application
models	I-Application
,	O
such	O
as	O
those	O
run	O
as	O
part	O
of	O
CMIP	B-Application
experiments	O
,	O
are	O
run	O
at	O
a	O
resolution	O
of	O
1-1/4	O
°	O
in	O
the	O
ocean	O
,	O
and	O
can	O
therefore	O
not	O
resolve	O
baroclinic	O
eddies	O
across	O
large	O
parts	O
of	O
the	O
ocean	O
,	O
particularly	O
at	O
the	O
poles	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
the	O
effects	O
of	O
eddies	O
are	O
parameterised	O
in	O
climate	B-Application
models	I-Application
,	O
such	O
as	O
through	O
the	O
widely-used	O
Gent-McWilliams	O
(	O
GM	O
)	O
parameterisation	O
which	O
represents	O
the	O
isopycnal-flattening	O
effects	O
of	O
eddies	O
as	O
a	O
diffusivity	O
.	O
</s>
<s>
The	O
process	O
of	O
determining	O
the	O
exact	O
values	O
of	O
the	O
parameters	O
in	O
a	O
parameterization	O
is	O
called	O
calibration	B-General_Concept
,	O
or	O
sometimes	O
less	O
precise	O
,	O
tuning	O
.	O
</s>
<s>
Calibration	B-General_Concept
is	O
a	O
difficult	O
process	O
,	O
and	O
different	O
strategies	O
are	O
used	O
to	O
do	O
it	O
.	O
</s>
