<s>
Direct	B-Algorithm
insolation	I-Algorithm
is	O
the	O
insolation	O
measured	O
at	O
a	O
given	O
location	O
on	O
Earth	O
with	O
a	O
surface	O
element	O
perpendicular	O
to	O
the	O
Sun	O
's	O
rays	O
,	O
excluding	O
diffuse	O
insolation	O
(	O
the	O
solar	O
radiation	O
that	O
is	O
scattered	O
or	O
reflected	O
by	O
atmospheric	O
components	O
in	O
the	O
sky	O
)	O
.	O
</s>
<s>
Direct	B-Algorithm
insolation	I-Algorithm
is	O
equal	O
to	O
the	O
solar	O
irradiance	O
above	O
the	O
atmosphere	O
minus	O
the	O
atmospheric	O
losses	O
due	O
to	O
absorption	O
and	O
scattering	O
.	O
</s>
<s>
A	O
simple	O
formula	O
gives	O
the	O
approximate	O
level	O
of	O
direct	B-Algorithm
insolation	I-Algorithm
when	O
there	O
are	O
no	O
clouds	O
:	O
</s>
<s>
For	O
practical	O
purposes	O
,	O
a	O
time-average	O
of	O
the	O
direct	B-Algorithm
insolation	I-Algorithm
over	O
the	O
course	O
of	O
the	O
year	O
is	O
commonly	O
used	O
.	O
</s>
<s>
Direct	B-Algorithm
insolation	I-Algorithm
is	O
measured	O
in	O
(	O
W/m2	O
)	O
or	O
kilowatt-hours	O
per	O
square	O
meter	O
per	O
day	O
(	O
kW·	O
h/	O
( m2·day	O
)	O
)	O
.	O
</s>
