<s>
Downscaling	B-Application
is	O
any	O
procedure	O
to	O
infer	O
high-resolution	O
information	O
from	O
low-resolution	O
variables	O
.	O
</s>
<s>
This	O
technique	O
is	O
based	O
on	O
dynamical	O
or	O
statistical	O
approaches	O
commonly	O
used	O
in	O
several	O
disciplines	O
,	O
especially	O
meteorology	O
,	O
climatology	O
and	O
remote	B-Application
sensing	I-Application
.	O
</s>
<s>
The	O
term	O
downscaling	B-Application
usually	O
refers	O
to	O
an	O
increase	O
in	O
spatial	O
resolution	O
,	O
but	O
it	O
is	O
often	O
also	O
used	O
for	O
temporal	O
resolution.This	O
is	O
not	O
to	O
be	O
confused	O
with	O
image	O
downscaling	B-Application
which	O
is	O
a	O
process	O
of	O
reducing	O
an	O
image	O
from	O
a	O
higher	O
resolution	O
to	O
a	O
lower	O
resolution	O
.	O
</s>
<s>
Global	B-Application
Climate	I-Application
Models	I-Application
(	O
GCMs	O
)	O
used	O
for	O
climate	O
studies	O
and	O
climate	O
projections	O
are	O
typically	O
run	O
at	O
spatial	O
resolutions	O
of	O
the	O
order	O
of	O
150	O
to	O
200km	O
and	O
are	O
limited	O
in	O
their	O
ability	O
to	O
resolve	O
important	O
sub-grid	O
scale	O
features	O
such	O
as	O
convection	O
clouds	O
and	O
topography	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
GCM	B-Application
based	O
projections	O
may	O
not	O
be	O
robust	O
for	O
local	O
impact	O
studies	O
.	O
</s>
<s>
To	O
overcome	O
this	O
problem	O
,	O
downscaling	B-Application
methods	O
are	O
developed	O
to	O
obtain	O
local-scale	O
weather	O
and	O
climate	O
,	O
particularly	O
at	O
the	O
surface	O
level	O
,	O
from	O
regional-scale	O
atmospheric	O
variables	O
that	O
are	O
provided	O
by	O
GCMs	O
.	O
</s>
<s>
Two	O
main	O
forms	O
of	O
downscaling	B-Application
technique	O
exist	O
.	O
</s>
<s>
One	O
form	O
is	O
dynamical	B-Application
downscaling	I-Application
,	O
where	O
output	O
from	O
the	O
GCM	B-Application
is	O
used	O
to	O
drive	O
a	O
regional	O
,	O
numerical	O
model	O
in	O
higher	O
spatial	O
resolution	O
,	O
which	O
therefore	O
is	O
able	O
to	O
simulate	O
local	O
conditions	O
in	O
greater	O
detail	O
.	O
</s>
<s>
The	O
other	O
form	O
is	O
statistical	B-Application
downscaling	I-Application
,	O
where	O
a	O
statistical	O
relationship	O
is	O
established	O
from	O
observations	O
between	O
large	O
scale	O
variables	O
,	O
like	O
atmospheric	O
surface	O
pressure	O
,	O
and	O
a	O
local	O
variable	O
,	O
like	O
the	O
wind	O
speed	O
at	O
a	O
particular	O
site	O
.	O
</s>
<s>
The	O
relationship	O
is	O
then	O
subsequently	O
used	O
on	O
the	O
GCM	B-Application
data	O
to	O
obtain	O
the	O
local	O
variables	O
from	O
the	O
GCM	B-Application
output	O
.	O
</s>
<s>
Wilby	O
and	O
Wigley	O
placed	O
meteorological	O
downscaling	B-Application
techniques	O
into	O
four	O
categories	O
:	O
regression	O
methods	O
,	O
weather	O
pattern-based	O
approaches	O
,	O
stochastic	O
weather	O
generators	O
,	O
which	O
are	O
all	O
statistical	B-Application
downscaling	I-Application
methods	O
,	O
and	O
limited-area	O
modeling	O
(	O
which	O
corresponds	O
to	O
dynamical	B-Application
downscaling	I-Application
methods	O
)	O
.	O
</s>
<s>
Additionally	O
,	O
a	O
semi-mechanistic	O
downscaling	B-Application
approach	O
can	O
be	O
applied	O
as	O
for	O
example	O
used	O
for	O
the	O
CHELSA	O
data	O
of	O
downscaled	O
model	O
output	O
.	O
</s>
<s>
In	O
this	O
example	O
,	O
the	O
temperature	O
algorithm	O
is	O
based	O
on	O
statistical	B-Application
downscaling	I-Application
and	O
the	O
precipitation	O
algorithm	O
incorporates	O
orographic	O
predictors	O
with	O
a	O
subsequent	O
bias	O
correction	O
.	O
</s>
<s>
The	O
Coordinated	O
Regional	O
Downscaling	B-Application
Experiment	O
(	O
CORDEX	O
)	O
was	O
initiated	O
in	O
2009	O
with	O
the	O
objective	O
of	O
providing	O
a	O
framework	O
for	O
the	O
evaluation	O
and	O
comparison	O
of	O
downscaling	B-Application
model	O
performance	O
,	O
as	O
well	O
as	O
define	O
a	O
set	O
of	O
experiments	O
to	O
produce	O
climate	O
projections	O
for	O
use	O
in	O
impact	O
and	O
adaptation	O
studies	O
.	O
</s>
<s>
CORDEX	O
climate	O
change	O
experiments	O
are	O
driven	O
by	O
the	O
WCRP	O
CMIP5	O
GCM	B-Application
outputs	O
.	O
</s>
<s>
CORDEX	O
defined	O
14	O
downscaling	B-Application
regions	O
or	O
domains	O
.	O
</s>
