ModelId:

DegreeDays1

SimileVersion:

4.0

The development rate of plants and invertebrate animals often depends on amount of heat received while the ambient temperature is between minimum and maximum thresholds.

The number of degree-days is a commonly used statistic related to the development of plants and invertebrates. Degree-days, DD, is given by:

DD = ∫ Tt.dt

- T is temperature in degrees Celsius (could be Fahrenheit)
- t is time in days.

degree-days is then ^{o}C days or ^{o}F days.

Equations:

Compartment DegreeDays : Degree days

Initial value = 0

Rate of change = + dDt on dt

Comments:

Also called temperature sum or less accurately "heat sum".

Flow dDt on dt : Rate of accumation of degree-days (degC)

dDt on dt = max(T_m-T_thresh,0)

Where:

T_m=../Environment/T_m

Variable Sdevelopment : State of development

Sdevelopment = min(DegreeDays/DDreq,1)

Comments:

Value = 0 to 1

Equations in Environment

Variable T_m : Mean daily temperature

Results:

Weblinks:

University of California Integrated Pest Management Program [1] [1] http://www.ipm.ucdavis.edu/WEATHER/ddconcepts.html