Program Growing_Degree_Days

!--------------------------------------------------------------------------------------
! Samantha Santeiu
! Meteorology 227
! Assignment #5
! Due Date: 09/28/09
!
! Filename: hw5_SANTEIU.f90
!--------------------------------------------------------------------------------------
!
! This program takes in values for daily minimum and maximum temperatures, calculates 
! the average temperature and number of Growing Degree Days, and outputs those four 
! values to the screen.
! 
! MaxTemp, MinTemp: temperatures entered by the user (degrees Fahrenheit)
! BaseTemp: base temperature used in calculating the Growing Degree Days (degrees Fahrenheit)
! New_MaxTemp, New_MinTemp: reset due to temperature threshholds (degrees Fahrenheit)
! AvgTemp, New_AvgTemp, GDDays: calculated during execution (degrees/days)
! MaxTemp, MinTemp, AvgTemp, GDDays: outputs printed to the screen  (degrees/days)
!
! Inputs: MaxTemp, MinTemp (degrees Fahrenheit)
! Constants: BaseTemp (degrees Fahrenheit)
! Calculated but not displayed: New_MaxTemp, New_MinTemp, New_AvgTemp (degrees Fahrenheit)
! Outputs: MaxTemp,  MinTemp, AvgTemp, GDDays (degrees/days)
!
!--------------------------------------------------------------------------------------

! Declaration statements

IMPLICIT NONE
 REAL :: MaxTemp, MinTemp, New_MaxTemp, New_MinTemp, AvgTemp, New_AvgTemp
 REAL :: GDDays, New_GDDays
 REAL, PARAMETER :: BaseTemp = 50.

! Get inputs for MaxTemp and MinTemp from the user.

PRINT *
PRINT *, "Enter the daily maximum and minimum temperatures in degrees Fahrenheit:"
READ *, MaxTemp, MinTemp

! Determine whether MaxTemp and MinTemp are within the threshhold level (86 to
! 50 degrees).  If the values are not within the threshhold level, set New_MaxTemp 
! and/or New_MinTemp equal to the threshhold values.  If the values are within the
! threshhold, simply set New_MaxTemp equal to the value of MaxTemp and New_MinTemp 
! equal to the value of MinTemp.

IF (MaxTemp > 86) THEN
   New_MaxTemp = 86
 ELSE IF (MaxTemp < 50) THEN
   New_MaxTemp = 50
 ELSE
   New_MaxTemp = MaxTemp
END IF

IF (MinTemp < 50) THEN
   New_MinTemp = 50
 ELSE IF (MinTemp > 86) THEN
   New_MinTemp = 86
 ELSE
   New_MinTemp = MinTemp
END IF

! Calculate the values for the average temperature with the original values (AvgTemp)
! and the average temperature with the reset values (New_AvgTemp). Use the New_AvgTemp 
! to calculate the Growing Degree Days (GDDays).

AvgTemp = (MaxTemp + MinTemp) / 2.0
New_AvgTemp = (New_MaxTemp + New_MinTemp) / 2.0

! Calculate the Growing Degree Days and determine if the value is greater than or
! less than 0. If the GDDays is greater than zero, keep the value; if it is not,
! set the value of GDDays equal to zero.

GDDays = New_AvgTemp - BaseTemp

IF (GDDays > 0) THEN
   GDDays = GDDays
 ELSE
   GDDays = 0.0
END IF

! Print the max and min temperatures, the average temperature, and the growing
! degree days.

PRINT *
PRINT *, "For a maximum temperature ", MaxTemp, "degrees Fahrenheit"
PRINT *, "and a minimum temperature ", MinTemp, "degrees Fahrenheit"
PRINT *, "Average temperature = ", AvgTemp, "degrees Fahrenheit"
PRINT *, "Growing degree days = ", GDDays
PRINT *

! End Program Statement

End Program Growing_Degree_Days