Apparent Temperature


Abstract: 
This document details the code format used for daily values of maximum
and minimum apparent temperature from first-order observation stations
in the U.S.A.
Apparent temperature (AT), invented in the late 1970s, was designed to 
measure thermal sensation in indoor conditions, but was extended in the 
early 1980s to include the effect of sun and wind. The AT used here is 
based on a mathematical model of an adult, walking outdoors, in the shade 
(Steadman 1984). The AT is defined as; the temperature, at the reference 
humidity level, producing the same amount of discomfort as that experienced 
under the current ambient temperature and humidity.
			AT = -1.3 + 0.92T + 2.2e
Where T is the ambient temperature in degrees Celsius and e is the vapor 
pressure in kPa.
Hourly weather observations from first-order stations include ambient 
temperature, dew point temperature and atmospheric pressure. The latter 
two variables can be used to calculate water vapor pressure.

Steadman, R.G. 1984, A Universal Scale of Apparent Temperature, J. App. Met, 
23, 12, pp 1674


Format:
               Element                      Width         Position      
 001  RECORD TYPE (= DLY)                     3            001-003    
 002  STATION ID                              8            004-011    
 003  METEOROLOGICAL ELEMENT TYPE             4            012-015  
 004  MET. ELEMENT MEASUREMENT UNITS CODE     2            016-017
 005  YEAR
 006  MONTH                                   4            018-021    
 007  FILLER (= XXXX)                         4            024-027 
 008  NUMBER OF DATA PORTIONS THAT FOLLOW     3            028-030 
Variable length portion
 009  DAY OF MONTH                            2            031-032   
 010  HOUR OF OBSERVATION                     2            033-034 
 011  SIGN OF METEOROLOGICAL ELEMENT VALUE    1            035    
 012  VALUE OF METEOROLOGICAL ELEMENT         5            036-040 
 013  BLANK				      1            041       
 014  QUALITY CONTROL FLAG 2                  1            042  
Repeat data groups for each day of month as elements 9 - 14

                                                                     
001	Record type (always DLY)
002	Station ID. Five digit WBAN station ID prefixed with '000'
003	Meteorological element type:
          ETMX indicates apparent (effective) temperature maximum
          ETMN indicates apparent (effective) temperature minimum
004	Element measurement units:
	          'F '(whole degrees Fahrenheit)
005	Year
006	Month
007	Filler
008	Number of data portions to follow (usually number of days in the month)

The following elements are repeated for each data portion
009	Day of month
010	Local Standard Time hour of maximum or minimum apparent temperature 
        value (99 if missing)
011	Sign of maximum or minimum AT value
012	Maximum or minimum AT value (99999 if missing)
013	Blank
014	Quality Control flag (either '9' for missing or '0' for good)