conversions.py - a set of functions to convert pywws native units (Centigrade, mm, m/s, hPa) to other popular units
Functions
apparent_temp(temp, rh, wind) | Compute apparent temperature (real feel), using formula from |
cadhumidex(temp, humidity) | Calculate Humidity Index as per Canadian Weather Standards |
dew_point(temp, hum) | Compute dew point, using formula from http://en.wikipedia.org/wiki/Dew_point. |
illuminance_wm2(lux) | Approximate conversion of illuminance in lux to solar radiation in W/m2 |
pressure_inhg(hPa) | Convert pressure from hectopascals/millibar to inches of mercury |
pressure_trend_text(trend) | Convert pressure trend to a string, as used by the UK met office. |
rain_inch(mm) | Convert rainfall from millimetres to inches |
temp_f(c) | Convert temperature from Celsius to Fahrenheit |
usaheatindex(temp, humidity, dew) | Calculate Heat Index as per USA National Weather Service Standards |
wind_bft(ms) | Convert wind from metres per second to Beaufort scale |
wind_chill(temp, wind) | Compute wind chill, using formula from |
wind_kmph(ms) | Convert wind from metres per second to kilometres per hour |
wind_kn(ms) | Convert wind from metres per second to knots |
wind_mph(ms) | Convert wind from metres per second to miles per hour |
winddir_degrees(pts) | Convert wind direction from 0..15 to degrees |
winddir_text(pts) | Convert wind direction from 0..15 to compass point text |
Approximate conversion of illuminance in lux to solar radiation in W/m2
Convert pressure from hectopascals/millibar to inches of mercury
Convert pressure trend to a string, as used by the UK met office.
Compute average wind direction (in degrees) for a slice of data.
The wind speed and direction of each data item is converted to a vector before averaging, so the result reflects the dominant wind direction during the time period covered by the data.
Setting the decay parameter converts the filter from a simple averager to one where the most recent sample carries the highest weight, and earlier samples have a lower weight according to how long ago they were.
This process is an approximation of “exponential smoothing”. See Wikipedia for a detailed discussion.
The parameter decay corresponds to the value (1 - alpha) in the Wikipedia description. Because the weather data being smoothed may not be at regular intervals this parameter is the decay over 5 minutes. Weather data at other intervals will have its weight scaled accordingly.
Note: | The return value is in degrees, not the 0..15 range used elsewhere in pywws. |
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Parameters: |
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Return type: | float |
Convert wind direction from 0..15 to compass point text
Compute dew point, using formula from http://en.wikipedia.org/wiki/Dew_point.
Calculate Humidity Index as per Canadian Weather Standards
Calculate Heat Index as per USA National Weather Service Standards
See http://en.wikipedia.org/wiki/Heat_index, formula 1. The formula is not valid for T < 26.7C, Dew Point < 12C, or RH < 40%
Compute wind chill, using formula from http://en.wikipedia.org/wiki/wind_chill
Compute apparent temperature (real feel), using formula from http://www.bom.gov.au/info/thermal_stress/
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