WindChill

Summary

Identifies dangerous winter conditions that, depending on exposure times to the elements, can result in frostbite or hypothermia.

Discussion

The formula the function uses to compute wind chill is as follows:

Wind Chill = 35.74 + (0.6215 * T) - (35.75 * WS^0.16) + (0.4275 * T * WS^0.16)

• T = Air Temperature in degrees Fahrenheit
• WS = Wind speed in miles per hour

For more information about how this function works, see the Wind Chill raster function.

The referenced raster dataset for the raster object is temporary. To make it permanent, you can call the raster object's save method.

Syntax

WindChill (temperature_raster, wind_speed_raster, {temperature_units}, {wind_speed_units}, {wind_chill_units})

Parameter	Explanation	Data Type
temperature_raster [temperature_raster,...]	A single-band raster where pixel values represent ambient air temperature.	Raster
wind_speed_raster [wind_speed_raster,...]	A single-band raster where pixel values represent wind speed.	Raster
temperature_units	The unit of measurement associated with the input temperature raster. Available input units are Celsius, Fahrenheit, and Kelvin. (The default value is Fahrenheit)	String
wind_speed_units	Defines the unit of measurement for the wind-speed raster: mph —Miles per hour km/h —Kilometers per hour m/s —Meters per second ft/s —Feet per second kn —Knots (The default value is mph)	String
wind_chill_units	The unit of measurement associated with the output raster. Available output units are Celsius, Fahrenheit, and Kelvin. (The default value is Fahrenheit)	String

Return Value

Data Type	Explanation
Raster	The output raster.

Code sample

WindChill example 1

Calculates wind chill based on the temperature and wind speed from the input raster.

from arcpy.sa import *
out_windchill_raster = WindChill("temperature.tif", "windspeed.tif", "",
                                 "km/h", "Celsius")
out_windchill_raster.save("C:/arcpyExamples/outputs/wind_chill_C.tif")

WindChill example 2

Calculates wind chill based on the temperature and wind speed from the input raster.

# Import system modules
import arcpy
from arcpy.sa import *

# Set the analysis environments
arcpy.env.workspace = "C:/arcpyExamples/data"

# Set the local variables
in_temperature_raster = "temperature.tif"
in_wind_speed_raster  = "windspeed.tif"

# Execute WindChill function
out_windchill_raster = WindChill(in_temperature_raster, in_wind_speed_raster,
                                 "", "knots", "Kelvin")
# Save the output
out_windchill_raster.save("C:/arcpyExamples/outputs/wind_chill_K.tif")