hi all I don't anything about Mac code But do think it would be posable to do a THWS index he is some info
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THSW INDEX
Parameters Used: Temperature, Humidity, Solar Radiation, Wind Speed, Latitude & Longitude, Time and Date
What is it: Like Heat Index, the THSW Index uses humidity and temperature to calculate an apparent temperature. In addition, THSW incorporates the heating effects of solar radiation and the cooling effects of wind (like wind chill) on our perception of temperature.
Formula: The formula was developed by Steadman (1979). The following describes the series of
formulas used to determine the THSW or Temperature-Humidity-Sun-Wind Index. Thus, this index indicates the level of thermal comfort including the effects of all these values.
This Index is calculated by adding a series of successive terms. Each term represents one of the three parameters: (Humidity, Sun & Wind). The humidity term serves as the base from which increments for sun and wind effects are added.
The Vantage Pro calculation is an improvement over the THSW Index in the Health EnviroMonitor because the Health system:
only calculates THSW Index when air temperature is at or above 68F.
assumes the sky is clear.
assumes the elevation is sea level.
HUMIDITY FACTOR
The first term is humidity. This term is determined in the same manner as the Heat Index. This term serves as a base number to which increments of wind and sun are added to come up with the final THSW Index temperature.
WIND FACTOR
The second term is wind. Depending upon your version of firmware or software, this term is determined in part by a lookup table (for temperatures above 50F) and in part by the wind chill calculation, or uses an integrated table that is used both for calculation of this term and for wind chill. With this in mind, the followingcriterion apply with WeatherLink version 5.6 or later:
At 0 mph, this term is equal to zero.
For temperatures at or above 68F and wind speeds above 40 mph, the wind speed is set to 40 mph. For later versions, there is no upper limit on wind speed.
For temperatures at or above 130F, this term is set equal to zero. For later versions of this algorithm: WeatherLink uses 144F as the threshold. This is based on a best-fit regression of the Steadman 1979 wind table. The differences are reflective of the higher resolution used in the WeatherLink software.
For temperatures below 50F the wind chill result is used (calculate the wind chill increment using the difference between the air temperature and wind chill)
The resulting value is the wind term, which will be added to the humidity term and subsequently the sun term as indicated below.
SUN FACTOR
The third term is sun. This term, Qg, is actually a combination of four terms (direct incoming solar, indirect incoming solar, terrestrial, and sky radiation). The term depends upon wind speed to determine how strong an effect it is. The value is limited to between −20 and +130 W/m2.
REFERENCES
Steadman, R.G., 1979: The Assessment of Sultriness, Part II: Effects of Wind, Extra Radiation and Barometric Pressure on Apparent Temperature. Journal of Applied Meteorology, July 1979.
"Media Guide to NWS Products and Services", National Weather Service Forecast Office, Monterey, CA, 1995.
Quayle, R.G. and Steadman, R.G., 1998: The Steadman Wind Chill: An Improvement over Present Scales. Weather and Forecasting, December 1998
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