# MiscEl: Weather and air

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This page is used to calculate some weather, air and wind releated values.

### Functions

 Dew point / %RH Convert between different ways to measure water contents in air Wind chill factor Perceived air temperature Heat index Perceived discomfort in hot air Air at altitude Different average values depending on altitude Air at pressure Different values depending on air pressure Wind turbine power Estimate power from wind turbines

### Input values

 Temperature Actual temperature for calculations %RH Relative humidity in percent (Optional) Dew point Dew point temperature (Optional) Wind speed Actual windspeed Altitude High above sea level Pressure Air pressure Rotor Ø Rotor Ø for wind turbine, used to calculate area of wings

### Output values

 H2O pressure Partial pressure from H2O at specified values H2O saturation pressure Pressure for saturated air at specified temperature %RH Relative humidity in percent Dew point Any surface with a temperature below this value will get wet Water Amount of water in the air Wind chill Based on heat loss from exposed skin Heat loss Heat loss is based on human skin temperature Heat index Combines temperature and relative humidity to estimate heat discomfort Summer simmer index Combines temperature and relative humidity to estimate heat discomfort (Also called SSI) Water boils at Water boils different temperature, depending on air pressure. Air temperature Average temperature at selected altitude Air density Air density at pressure and temperature Power Power in wind, calculated from mowing air mass Rotor area Area of roter, the full area is assumed to be sweept by the wind Area power Power in wind, calculated from mowing air mass in rotor area Theoretically max Theoretically maximum power from wind, this is 59% of the total power (Betz' law) Power, good design Estimated power output for a good designed wind turbine Power, simple design Estimated power output for a simple designed wind turbine

### Hints

 Water changes with temperature, why? Assuming constant pressure, the volume of air will change with temperature Wind chill 2001 Assumes wind speed is measure in 10 meters height and that body is at ground level. Is based on a human face model Wind chill 1939 Based on freezing times of a water bottle Temperature and wind chill Objects will not be cooled below actual temperature, just cooled faster due to wind chill factor

### Other pages

• For other sound in air calculations, use the Sound page.