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

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 hourkm/h —Kilometers per hourm/s —Meters per secondft/s —Feet per secondkn —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.ia 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.ia 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")``````