WEATHR.for

************************************************************************
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*     SUBROUTINE WEATHR - Reads daily weather data from file
************************************************************************
*
*     LIST OF VARIABLES
*
*     DATE = date of weather record (YYDDD)
*     DYN  = dynamic control variable
*     PAR  = photosynthetically active radiation (MJ/m2/d)
*     RAIN = daily rainfall (mm)
*     SRAD = daily solar radiation (MJ/m2/d)
*     TMAX = daily maximum temperature (Celsius)
*     TMIN = daily minimum temperature (Celsius)
*
***********************************************************************
      SUBROUTINE WEATHR(SRAD,TMAX,TMIN,RAIN,PAR,DYN)

!-----------------------------------------------------------------------  
      IMPLICIT NONE 

      REAL SRAD,TMAX,TMIN,RAIN,PAR
      INTEGER DATE
      CHARACTER*5 DYN

!************************************************************************
!************************************************************************
!     INITIALIZATION
!************************************************************************
      IF (INDEX(DYN,'INIT') .NE. 0) THEN
!************************************************************************
        OPEN (4,FILE='WEATHER.INP',STATUS='UNKNOWN')  
      
!************************************************************************
!************************************************************************
!     RATE CALCULATIONS
!************************************************************************
      ELSEIF (INDEX(DYN,'RATE') .NE. 0) THEN
!************************************************************************
C     Loop to compute data for one year. Climatic data of the year 1987,
C     for Gainesville, Florida, were used as verification of the module.

        READ(4,20) DATE,SRAD,TMAX,TMIN,RAIN,PAR
   20   FORMAT(I5,2X,F4.1,2X,F4.1,2X,F4.1,F6.1,14X,F4.1)
      
        PAR = 0.5 *  SRAD   ! Par is defined as 50% of SRAD

!************************************************************************
!************************************************************************
      ELSEIF (INDEX(DYN,'CLOSE') .NE. 0) THEN
!************************************************************************
        CLOSE(4) 

!************************************************************************
!************************************************************************
!     End of dynamic 'IF' construct
!************************************************************************
      ENDIF
!************************************************************************
      RETURN
      END SUBROUTINE WEATHR
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