MiscEl: Weather and air

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


Dew point / %RHConvert between different ways to measure water contents in air
Wind chill factorPerceived air temperature
Heat indexPerceived discomfort in hot air
Air at altitudeDifferent average values depending on altitude
Air at pressureDifferent values depending on air pressure
Wind turbine powerEstimate power from wind turbines

Input values

TemperatureActual temperature for calculations
%RHRelative humidity in percent (Optional)
Dew pointDew point temperature (Optional)
Wind speedActual windspeed
AltitudeHigh above sea level
PressureAir pressure
Rotor Rotor for wind turbine, used to calculate area of wings

Output values

H2O pressurePartial pressure from H2O at specified values
H2O saturation pressurePressure for saturated air at specified temperature
%RHRelative humidity in percent
Dew pointAny surface with a temperature below this value will get wet
WaterAmount of water in the air
Wind chillBased on heat loss from exposed skin
Heat lossHeat loss is based on human skin temperature
Heat indexCombines temperature and relative humidity to estimate heat discomfort
Summer simmer indexCombines temperature and relative humidity to estimate heat discomfort (Also called SSI)
Water boils atWater boils different temperature, depending on air pressure.
Air temperatureAverage temperature at selected altitude
Air densityAir density at pressure and temperature
PowerPower in wind, calculated from mowing air mass
Rotor areaArea of roter, the full area is assumed to be sweept by the wind
Area powerPower in wind, calculated from mowing air mass in rotor area
Theoretically maxTheoretically maximum power from wind, this is 59% of the total power (Betz' law)
Power, good designEstimated power output for a good designed wind turbine
Power, simple designEstimated power output for a simple designed wind turbine


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

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