<s>
A	O
wind	B-Algorithm
profiler	I-Algorithm
is	O
a	O
type	O
of	O
weather	O
observing	O
equipment	O
that	O
uses	O
radar	B-Application
or	O
sound	O
waves	O
(	O
SODAR	O
)	O
to	O
detect	O
the	O
wind	O
speed	O
and	O
direction	O
at	O
various	O
elevations	O
above	O
the	O
ground	O
.	O
</s>
<s>
Above	O
this	O
level	O
there	O
is	O
inadequate	O
water	O
vapor	O
present	O
to	O
produce	O
a	O
radar	B-Application
"	O
bounce.	O
"	O
</s>
<s>
In	O
a	O
typical	O
implementation	O
,	O
the	O
radar	B-Application
or	O
sodar	O
can	O
sample	O
along	O
each	O
of	O
five	O
beams	O
:	O
one	O
is	O
aimed	O
vertically	O
to	O
measure	O
vertical	O
velocity	O
,	O
and	O
four	O
are	O
tilted	O
off	O
vertical	O
and	O
oriented	O
orthogonal	O
to	O
one	O
another	O
to	O
measure	O
the	O
horizontal	O
components	O
of	O
the	O
air	O
's	O
motion	O
.	O
</s>
<s>
The	O
energy	O
scattered	O
by	O
these	O
eddies	O
and	O
received	O
by	O
the	O
profiler	O
is	O
orders	B-Device
of	I-Device
magnitude	I-Device
smaller	O
than	O
the	O
energy	O
transmitted	O
.	O
</s>
<s>
The	O
radial	O
components	O
measured	O
by	O
the	O
tilted	O
beams	O
are	O
the	O
vector	O
sum	O
of	O
the	O
horizontal	O
motion	O
of	O
the	O
air	O
toward	O
or	O
away	O
from	O
the	O
radar	B-Application
and	O
any	O
vertical	O
motion	O
present	O
in	O
the	O
beam	O
.	O
</s>
<s>
Pulse-Doppler	B-Algorithm
radar	I-Algorithm
wind	B-Algorithm
profilers	I-Algorithm
operate	O
using	O
electromagnetic	O
(	O
EM	O
)	O
signals	O
to	O
remotely	O
sense	O
winds	O
aloft	O
.	O
</s>
<s>
The	O
radar	B-Application
transmits	O
an	O
electromagnetic	O
pulse	O
along	O
each	O
of	O
the	O
antenna	O
's	O
pointing	O
directions	O
.	O
</s>
<s>
A	O
UHF	O
profiler	O
includes	O
subsystems	O
to	O
control	O
the	O
radar	B-Application
's	O
transmitter	O
,	O
receiver	O
,	O
signal	O
processing	O
,	O
and	O
Radio	O
Acoustic	O
Sounding	O
System	O
(	O
RASS	O
)	O
,	O
if	O
provided	O
,	O
as	O
well	O
as	O
data	O
telemetry	O
and	O
remote	O
control	O
.	O
</s>
<s>
The	O
duration	O
of	O
the	O
transmission	O
determines	O
the	O
length	O
of	O
the	O
pulse	O
emitted	O
by	O
the	O
antenna	O
,	O
which	O
in	O
turn	O
corresponds	O
to	O
the	O
volume	O
of	O
air	O
illuminated	O
(	O
in	O
electrical	O
terms	O
)	O
by	O
the	O
radar	B-Application
beam	O
.	O
</s>
<s>
Small	O
amounts	O
of	O
the	O
transmitted	O
energy	O
are	O
scattered	O
back	O
(	O
referred	O
to	O
as	O
backscattering	B-Algorithm
)	O
toward	O
and	O
received	O
by	O
the	O
radar	B-Application
.	O
</s>
<s>
Delays	O
of	O
fixed	O
intervals	O
are	O
built	O
into	O
the	O
data	O
processing	O
system	O
so	O
that	O
the	O
radar	B-Application
receives	O
scattered	O
energy	O
from	O
discrete	O
altitudes	O
,	O
referred	O
to	O
as	O
range	O
gates	O
.	O
</s>
<s>
of	O
the	O
air	O
toward	O
or	O
away	O
from	O
the	O
radar	B-Application
along	O
each	O
beam	O
as	O
a	O
function	O
of	O
altitude	O
.	O
</s>
<s>
The	O
source	O
of	O
the	O
backscattered	B-Algorithm
energy	O
(	O
radar	B-Application
“	O
targets	O
”	O
)	O
is	O
small-scale	O
turbulent	O
fluctuations	O
that	O
induce	O
irregularities	O
in	O
the	O
radio	O
refractive	O
index	O
of	O
the	O
atmosphere	O
.	O
</s>
<s>
The	O
radar	B-Application
is	O
most	O
sensitive	O
to	O
scattering	O
by	O
turbulent	O
eddies	O
whose	O
spatial	O
scale	O
is	O
½	O
the	O
wavelength	O
of	O
the	O
radar	B-Application
,	O
or	O
approximately	O
16	O
centimeters	O
(	O
cm	O
)	O
for	O
a	O
UHF	O
profiler	O
.	O
</s>
<s>
A	O
boundary-layer	O
radar	B-Application
wind	B-Algorithm
profiler	I-Algorithm
can	O
be	O
configured	O
to	O
compute	O
averaged	O
wind	O
profiles	O
for	O
periods	O
ranging	O
from	O
a	O
few	O
minutes	O
to	O
an	O
hour	O
.	O
</s>
<s>
Boundary-layer	O
radar	B-Application
wind	B-Algorithm
profilers	I-Algorithm
are	O
often	O
configured	O
to	O
sample	O
in	O
more	O
than	O
one	O
mode	O
.	O
</s>
<s>
The	O
pulse	B-Algorithm
length	I-Algorithm
determines	O
the	O
depth	O
of	O
the	O
column	O
of	O
air	O
being	O
sampled	O
and	O
thus	O
the	O
vertical	O
resolution	O
of	O
the	O
data	O
.	O
</s>
<s>
In	O
a	O
“	O
high	O
mode	O
,	O
”	O
the	O
pulse	B-Algorithm
length	I-Algorithm
is	O
increased	O
,	O
usually	O
to	O
100	O
m	O
or	O
greater	O
.	O
</s>
<s>
The	O
longer	O
pulse	B-Algorithm
length	I-Algorithm
means	O
that	O
more	O
energy	O
is	O
being	O
transmitted	O
for	O
each	O
sample	O
,	O
which	O
improves	O
the	O
signal-to-noise	O
ratio	O
(	O
SNR	O
)	O
of	O
the	O
data	O
.	O
</s>
<s>
Using	O
a	O
longer	O
pulse	B-Algorithm
length	I-Algorithm
increases	O
the	O
depth	O
of	O
the	O
sample	O
volume	O
and	O
thus	O
decreases	O
the	O
vertical	O
resolution	O
in	O
the	O
data	O
.	O
</s>
<s>
When	O
radar	B-Application
wind	B-Algorithm
profilers	I-Algorithm
are	O
operated	O
in	O
multiple	O
modes	O
,	O
the	O
data	O
are	O
often	O
combined	O
into	O
a	O
single	O
overlapping	O
data	O
set	O
to	O
simplify	O
postprocessing	O
and	O
data	O
validation	O
procedures	O
.	O
</s>
<s>
Radar	B-Application
wind	B-Algorithm
profilers	I-Algorithm
may	O
also	O
have	O
additional	O
uses	O
,	O
for	O
example	O
in	O
a	O
biological	O
context	O
to	O
complement	O
large-scale	O
bird	O
monitoring	O
schemes	O
.	O
</s>
<s>
Alternatively	O
,	O
a	O
wind	B-Algorithm
profiler	I-Algorithm
may	O
use	O
sound	O
waves	O
to	O
measure	O
wind	O
speed	O
at	O
various	O
heights	O
above	O
the	O
ground	O
,	O
and	O
the	O
thermodynamic	O
structure	O
of	O
the	O
lower	O
layer	O
of	O
the	O
atmosphere	O
.	O
</s>
<s>
Each	O
of	O
the	O
individual	O
antennas	O
may	O
use	O
a	O
single	O
transducer	B-Algorithm
focused	O
into	O
a	O
parabolic	O
reflector	O
to	O
form	O
a	O
parabolic	B-Architecture
loudspeaker	I-Architecture
,	O
or	O
an	O
array	O
of	O
speaker	B-Device
drivers	I-Device
and	O
horns	B-Device
(	O
transducers	B-Algorithm
)	O
all	O
transmitting	O
in-phase	O
to	O
form	O
a	O
single	O
beam	O
.	O
</s>
<s>
This	O
is	O
accomplished	O
through	O
a	O
relaxation	O
between	O
pulse	B-Algorithm
length	I-Algorithm
and	O
maximum	O
altitude	O
.	O
</s>
