Appendix B ______________________________________________________ Calculation FormulasVAISALA ______________________________________________________________________ 275Wind Chill (NWS 2001)Wind chill, which is an estimate of the heat loss from an open surface, iscalculated according to the formula updated by NWS in 2001:16.016.0 486.095.1362.013.13 WSTWSTW AAch whereWCh = Wind chill [C]TA = Air temperature [C]WS = Wind speed [m/s]Table 112 Inputs for Wind Chill CalculationInput VariableAir temperature (TA) TAAVG1M; see Table 4 on page 22Wind speed (WS) WSAVG2M; see Table 6 on page 24Wet Bulb TemperatureWet bulb temperature is calculated iteratively as follows:First the initial estimate of wet bulb temperature is calculated with theformula:6.112)(TPlog-17.626.112)(TPlog243.12T dwsdwswetThen the wet bulb temperature is iteratively re-calculated as long asABS(Phit-Pws (Td ))>0.01 with the formula:P2)(TP-P-TT derdwshitwetwetwhere Phit and Pder are calculated depending on the value of Twet :Twet > 0:)(000662.0)( wetAAwetwshit TTPTPP
