# HeatIndex

## Zusammenfassung

Calculates apparent temperature based on ambient temperature and relative humidity. The apparent temperature is often described as how hot it feels to the human body.

## Diskussion

The formula that the Heat Index function uses to compute heat index is as follows:

``````Heat Index = ( -42.379 + (2.04901523 * T) + (10.14333127 * R)
- (0.22475541 * TR) - (6.83783e-3 * TT) - (5.481717e-2 * RR)
+ (1.22874e-3 * TTR) + (8.5282e-4 * TRR) - (1.99e-6 * TTRR) )``````

where:

• T = Air temperature
• R = Relative humidity

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

## Syntax

`HeatIndex (temperature_raster, relative_humidity_raster, {temperature_unit}, {heat_index_unit})`
 Parameter Erläuterung Datentyp temperature_raster Ein Einzelband-Raster, in dem Pixelwerte die Umgebungslufttemperatur darstellen. Raster relative_humidity_raster A single-band raster where pixel values represent relative humidity as a percentage value between 0 and 100. Raster temperature_unit Die mit dem Eingabe-Temperatur-Raster verknüpfte Maßeinheit. Die verfügbaren Eingabeeinheiten lauten Celsius, Fahrenheit und Kelvin.(Der Standardwert ist Fahrenheit) String heat_index_unit Die mit dem Ausgabe-Raster verknüpfte Maßeinheit. Die verfügbaren Ausgabeeinheiten lauten Celsius, Fahrenheit und Kelvin.(Der Standardwert ist Fahrenheit) String
Rückgabewert
 Datentyp Erläuterung Raster The output raster.

## Codebeispiel

HeatIndex example 1

This example calculates the heat index based on ambient temperature and relative humidity from the input raster.

``````from arcpy.ia import *
out_heatindex_raster = HeatIndex("temperature", "relative_humidity", "Celsius", "Kelvin")
out_heatindex_raster.save("C:/arcpyExamples/outputs/heat_index_K.tif")``````
HeatIndex example 2

This example calculates the heat index based on ambient temperature and relative humidity 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_relative_humidity_raster  = "relativehumid.tif"

# Execute the HeatIndex function
out_heat_index_raster = HeatIndex(in_temperature_raster, in_relative_humidity_raster, "", "Celsius")

# Save the output
out_heat_index_raster.save("C:/arcpyExamples/outputs/heat_index_C.tif")``````