Vaisala AWS330 - Wind Chill (NWS 2001); Wet Bulb Temperature

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:
16.016.0
486.095.1362.013.13 WSTWSTW
AAch

where
W
Ch
=
Wind chill [C]
T
A
=
Air temperature [C]
WS = Wind speed [m/s]
Table 112 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
)(TP
log -17.62
6.112
)(TP
log
243.12 T
dws
dws
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:
P2
)(TP - P
- T T
der
dwshit
wetwet


where P
hit
and P
der
are calculated depending on the value of T
wet
:
T
wet
> 0:
)(000662.0)(
wetAAwetwshit
TTPTPP




