Presentation on theme: "Calculating Degree Days Ashley Font National Science Foundation Graduate STEM Fellow in K-12 Education Sugar Creek Watershed K-12 Education Program The."— Presentation transcript:
Calculating Degree Days Ashley Font National Science Foundation Graduate STEM Fellow in K-12 Education Sugar Creek Watershed K-12 Education Program The Ohio State University-Ohio Agricultural Research and Development Center
The Degree Day FIRST OF ALL! Degree DAY is not a literal DAY It is just CALLED a Degree DAY
The Degree Day Unit of Heat Average amount of heat in degrees that have occurred in a single day 1 Degree Day results when the Average daily temperature is 1 degree above the lower threshold EX: Average 51 degrees, threshold is 50 degrees… 51-50= 1 dd
What is a lower threshold? Just means the lowest temperature that something can grow at. Some insects cannot develop until the temperature is 50°F Any lower, and the bug stops growing! Therefore, 50°F would be that bug’s threshold
Why do we use it? Monitoring these values of heat can help us predict pest activity Since insects are cold blooded, daily temperatures have A LOT to do with their development Temperature can be more precise than just using calendar dates.
Calculations Use the daily maximum temperature and the daily minimum temperature Get an Average for the day Subtract a lower threshold (we use 50F unless otherwise instructed)
The Formula (Max. Daily Temp. + Min. Daily Temp.) __ Lower 2 Threshold
Examples (pg 2) #1 June 1st, 2008 MAX: 74.1°F MIN: 50.2°F Lower Threshold: 50°F Calculation (74.1 + 50.2 ) - 50 = 12.15 2 So, on June 1st, 12.15 Degree Days have accumulated
Examples cont. (pg 2) # 2 When the minimum daily temperature is BELOW the lower threshold, REPLACE the Minimum Daily Temp in the formula with the THRESHOLD.** May 28th,2008 MAX: 66.5°F MIN: 38.6°F LT: 50°F ( 66.5 + 50 ) - 50 = 8.25 2
Examples cont. (pg 2) #3 ** There are not NEGATIVE degree days. If the formula results in a negative, it is ZERO degree days… meaning no heat accumulated on this day January 1 st Max:41.6 Min:19.0 LT: 50°F (41.6 + 50) - 50 = -4.2 2 So, ZERO DD. No development occurred this day.
Cumulative Degree Day Just adding up each day’s DD units to get the total for multiple days Usually start adding at January 1 st. This can help us predict what day of the year something will occur by following how much heat is accumulated each day.