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Notes:
The first tool treated here is the degree-day model, which is the most common format used for representing the development, or phenology, of organisms that are dependent upon temperature for development. In the upper left figure, notice that temperatures vary as an approximate sine-wave over 2 days time in this case. The shaded areas above a lower threshold, and perhaps below an optional upper threshold, represent an index of development for organisms that depend on temperatures in this range. We use geometric approximations, such as the triangle calculations shown here, to compute and track this index of development.