<s>
TOMCAT/SLIMCAT	B-Application
is	O
an	O
off-line	O
chemical	O
transport	O
model	O
(	O
CTM	O
)	O
,	O
which	O
models	O
the	O
time-dependent	O
distribution	O
of	O
chemical	O
species	O
in	O
the	O
troposphere	O
and	O
stratosphere	O
.	O
</s>
<s>
The	O
original	O
model	O
code	O
,	O
called	O
the	O
Toulouse	O
Off-line	O
Model	O
of	O
Chemistry	O
And	O
Transport	O
(	O
TOMCAT	B-Application
)	O
,	O
was	O
written	O
by	O
Martyn	O
Chipperfield	O
at	O
Météo	O
France	O
.	O
</s>
<s>
"	O
Off-line	O
"	O
in	O
this	O
sense	O
describes	O
the	O
fact	O
that	O
although	O
the	O
meteorological	O
data	O
(	O
wind	O
components	O
and	O
other	O
fields	O
)	O
which	O
are	O
used	O
as	O
input	O
to	O
the	O
CTM	O
typically	O
derive	O
from	O
a	O
general	B-Application
circulation	I-Application
model	I-Application
(	O
GCM	O
)	O
,	O
the	O
CTM	O
is	O
run	O
as	O
a	O
separate	O
program	O
outside	O
of	O
a	O
GCM	O
;	O
this	O
is	O
as	O
distinct	O
from	O
a	O
chemistry	O
simulation	O
scheme	O
which	O
runs	O
within	O
a	O
GCM	O
,	O
in	O
which	O
the	O
simulated	O
chemical	O
distributions	O
,	O
e.g.	O
</s>
<s>
A	O
version	O
called	O
the	O
Single	O
Layer	O
Isentropic	O
Model	O
of	O
Chemistry	O
And	O
Transport	O
(	O
SLIMCAT	B-Application
)	O
was	O
developed	O
in	O
1995	O
.	O
</s>
<s>
This	O
used	O
a	O
level	O
of	O
constant	O
potential	O
temperature	O
(	O
or	O
equivalently	O
,	O
of	O
constant	O
specific	O
entropy	B-Algorithm
,	O
hence	O
isentropic	O
)	O
,	O
exploiting	O
the	O
fact	O
that	O
due	O
to	O
approximate	O
conservation	O
of	O
energy	O
,	O
atmospheric	O
motions	O
are	O
approximately	O
adiabatic	O
and	O
hence	O
air	O
parcels	O
remain	O
on	O
isentropic	O
levels	O
on	O
short	O
timescales	O
.	O
</s>
<s>
A	O
diabatic	O
heating	O
scheme	O
was	O
later	O
added	O
,	O
to	O
allow	O
for	O
multiple	O
isentropic	O
levels	O
with	O
transport	O
between	O
them	O
on	O
longer	O
timescales	O
,	O
although	O
the	O
name	O
"	O
SLIMCAT	B-Application
"	O
has	O
remained	O
despite	O
the	O
multiple	O
levels	O
.	O
</s>
<s>
The	O
two	O
programs	O
are	O
now	O
maintained	O
as	O
a	O
single	O
code	O
base	O
,	O
which	O
runs	O
in	O
Fortran	B-Application
,	O
and	O
has	O
been	O
parallelised	O
.	O
</s>
<s>
TOMCAT	B-Application
has	O
been	O
further	O
extended	O
to	O
include	O
a	O
detailed	O
treatment	O
of	O
aerosol	O
.	O
</s>
<s>
The	O
primary	O
purpose	O
of	O
TOMCAT/GLOMAP	O
is	O
to	O
simulate	O
aerosol	O
radiative	B-Algorithm
forcing	I-Algorithm
and	O
the	O
impact	O
of	O
aerosol	O
on	O
climate	O
.	O
</s>
