DAVIS WeatherLink for Windows 4.0 - Manual (Page 95)

U S I N G T H E S O F T W A R E
Degree-Days
86
▲ Degree-Day Calculation Method
Choose the method by which degree-days are calculated.
▲ Growing Degree-Day “Cut-Off” Method
The software uses the highest temperature and the lowest temperature
for a given day to calculate the average temperature for that day. Note,
however, that if the low temperature is below the base threshold, the
software uses the base threshold as the low temperature when deter-
mining average temperature for the day. In addition, if the high tem-
perature is above the upper threshold, the software uses the upper
threshold as the high temperature when determining average tempera-
ture. For this method, both thresholds must be entered.
The difference between the average temperature and the base thresh-
old is assumed to be the number of degree-days accumulated on that
day. (For example, if the average of the highest and lowerst tempera-
tures was 24˚ above the base threshold, the software would assume 24
degree-days for the entire day.)
Note: Unless 15 hours worth of records exist in the database for a day (through 3pm),
the software will not calculate degree-days for that day.
▲ High/Low Method
The software uses the highest temperature and the lowest temperature
for a given day to calculate the average temperature for that day. Note,
however, that if the high temperature is above the upper threshold the
software uses the upper threshold as the high temperature when deter-
mining average temperature for the day. (If no upper threshold is
entered, the high temperature will not be “cut off” in this way.) For
this method, the upper threshold need not be entered.
The difference between the average temperature and the base thresh-
old is assumed to be the number of degree-days accumulated on that
day. (For example, if the average of the highest and lowest tempera-
tures was 24˚ above the base threshold, the software would assume 24
degree-days for the entire day.)
Note: Unless 15 hours worth of records exist in the database for a day (through 3pm),
the software will not calculate degree-days for that day.
▲ Integration Method
The software calculates degree-days using the average temperature for
an interval and the interval time. For example, if the average tempera-
ture during a 15 minute interval was 24˚ above the base threshold, the
software would calculate 0.25 degree-days dudring that interval (24˚ *
15 minutes in interval / 1440 minutes per day). The number of degree-
days during each interval are added together to arrive at a degree-day
total. This method calculates degree-day totals more accurately than
the high/low method.