improver.feels_like_temperature module
Module containing feels like temperature calculation plugins
- _calculate_apparent_temperature(temperature, wind_speed, relative_humidity, pressure)[source]
Calculates the apparent temperature from 10 m wind speed, temperature and actual vapour pressure using the linear regression equation for shade described in A Universal Scale of Apparent Temperature, Steadman, 1984, page 1686, table 5.
The method used to determine the original values used for the regression equation takes into account many variables which are detailed in Steadman’s paper.
The paper calculates apparent temperature for wind speeds up to 20 m/s. Here, the apparent temperature regression equation has been used for all wind speeds.
- Parameters:
- Return type:
- Returns:
Apparent temperatures in degrees celsius
References
Steadman, R. (1984). A Universal Scale of Apparent Temperature. Journal of Climate and Applied Meteorology, 23(12), pp.1674-1687
- _calculate_wind_chill(temperature, wind_speed)[source]
Calculates the wind chill from 10 m wind speed and temperature based on the wind chill temperature index from a linear regression equation detailed in THE NEW WIND CHILL EQUIVALENT TEMPERATURE CHART, Osczevski and Bluestein, 2005, table 2.
- Parameters:
- Return type:
- Returns:
Wind chill temperatures in degrees celsius
References
Osczevski, R. and Bluestein, M. (2005). THE NEW WIND CHILL EQUIVALENT TEMPERATURE CHART. Bulletin of the American Meteorological Society, 86(10), pp.1453-1458.
Osczevski, R. and Bluestein, M. (2008). Comments on Inconsistencies in the New Windchill Chart at Low Wind Speeds. Journal of Applied Meteorology and Climatology, 47(10), pp.2737-2738.
Science background: The 2005 Osczevski and Bluestein paper outlines the research and the assumptions made, and the 2008 paper clarifies poorly explained sections of the first paper.
A brief summary of their assumptions are given below: The model aims to determine a worst-case scenario of wind chill. The wind speed “threshold” of 4.8 kph (1.34 m/s) stated in the 2005 papers does not refer to a threshold placed on the input windspeed data, which has no upper limit, but is the walking speed of an average person. This is therefore used as the minimum wind speed in their wind chill computer model, because even where wind speed is zero, a person would still experience wind chill from the act of walking (the model assumes that the person is walking into the wind). Furthermore, the equation is not valid for very low wind speeds and will return wind chill values higher than the air temperature if this lower wind speed limit is not imposed. Even with this limit, the calculated wind chill will be higher than the air temperature when the temperature is above about 11.5C and the wind is 4.8 kph. The model introduces a compensation factor where it assumes that the wind speed at 1.5 m (face level) is 2/3 that measured at 10 m. It also takes into account the thermal resistance of the skin on the human cheek with the assumption that the face is the most exposed area of skin during winter.
The equation outlined in their paper is also not the equation used in their model (which was computationally expensive) but rather it is a linear regression equation which mimics the output of their model where wind speeds are greater than 3kph (0.8m/s) (clarified in the 2008 paper). The assumption being that lower wind speeds are usually not measured or reported accurately anyway.
- _feels_like_temperature(temperature, apparent_temperature, wind_chill)[source]
Calculates feels like temperature from inputs in degrees Celsius using a combination of the wind chill index and Steadman’s apparent temperature equation as follows:
If temperature < 10 degrees C: The feels like temperature is equal to the wind chill.
If temperature > 20 degrees C: The feels like temperature is equal to the apparent temperature.
If 10 <= temperature <= 20 degrees C: A weighting (alpha) is calculated in order to blend between the wind chill and the apparent temperature.
- calculate_feels_like_temperature(temperature, wind_speed, relative_humidity, pressure, model_id_attr=None)[source]
Calculates the feels like temperature using a combination of the wind chill index and Steadman’s apparent temperature equation.
- Parameters:
- Return type:
- Returns:
Cube of feels like temperatures in the same units as the input temperature cube.