Wind chill (nws 2001), Wet bulb temperature – Vaisala AWS330 User Manual
Page 277
Appendix B ______________________________________________________ Calculation Formulas
VAISALA ______________________________________________________________________ 275
Wind Chill (NWS 2001)
Wind chill, which is an estimate of the heat loss from an open surface, is
calculated according to the formula updated by NWS in 2001:
16
.
0
16
.
0
486
.
0
95
.
13
62
.
0
13
.
13
WS
T
WS
T
W
A
A
ch
⋅
⋅
+
⋅
−
⋅
+
=
where
W
Ch
=
Wind chill [
°
C]
T
A
=
Air temperature [
°
C]
WS =
Wind
speed
[m/s]
Table 114
Inputs for Wind Chill Calculation
Input Variable
Air temperature (TA)
TAAVG1M; see Table 4 on page 22
Wind speed (WS)
WSAVG2M; see Table 6 on page 24
Wet Bulb Temperature
Wet bulb temperature is calculated iteratively as follows:
First the initial estimate of wet bulb temperature is calculated with the
formula:
6.112
)
(T
P
log
-
17.62
6.112
)
(T
P
log
243.12
T
d
ws
d
ws
wet
⋅
=
Then the wet bulb temperature is iteratively re-calculated as long as
ABS(P
hit
-P
ws
(T
d
))>0.01 with the formula:
P
2
)
(T
P
-
P
-
T
T
der
d
ws
hit
wet
wet
⋅
=
where P
hit
and P
der
are calculated depending on the value of T
wet
:
T
wet
> 0:
)
(
000662
.
0
)
(
wet
A
A
wet
ws
hit
T
T
P
T
P
P
−
⋅
⋅
−
=