Degree-Days for IPM

Description: Results of MGDD model for corn planted at 10-day intervals at Richmond (Chimborazo), VA. The developmental stage of corn can be estimated from the accumulated MGDDs (y-axis). Here, temperatures are in celsius, so corn would reach silking (R1) stage at approximately 500 MGDDs.  another example

The graph shown above is for Chimborazo, Virginia, the site of many Civil War battles that led to the capture of the confederate capital of Richmond, VA. This should not be confused with Chimborazo, Ecuador, the most distant place from the center of the Earth when standing on the surface of the planet. 
The GIS-based degree-day calculator is a tool for calculating the accumulating heat units using various methods. The DD calculator interface allows for user-specified parameters (biofix, base temperature, cutoff, cutoff method, interpolation method). The calculator developed using Visual Basic and  ESRI ArcObjects. The spatiotemporal output illustrates how degree-days might accumulate for a population of english grain aphids. There are a number of limitations to this model. 

[Climate - Weather - Soils ]

Selected Resources:

  1. Modeling shadows using NED and solar position
  2. Weather visualization using Unidata's IDV
  3. Data processing (Reed Nessler's 2003 Project Results)
  4. Virginia climate graphs
  5. Virginia climate - ArcIMS site (under construction) Derived from PRISM
  6. Virginia STATSGO 


  1. Interpolation of daily temperature surfaces from on-line weather data (Sforza)
  2. Degree-Day Mapping for IPM (Sforza) March 24, 2003





  1. IPM Weather Data and Degree-Days. Oregon Sate University
  2. Klopfer, Scott. 1997. Insolation, Precipitation, and Moisture Maps for a Virginia Geographic Information System. Master's Thesis.
  3. NCDC Climate Data On-Line.
  4. Sharov, A. Quantitative Population Ecology. Dept. of Entomology, Virginia Tech,
    Blacksburg, USA.

Other Links:

  1. Virginia State Climatology Office
  2. UC Degree Days and Phenology Models
  3. Oregon State Spatial Climate Analysis Center. PRISM climate mapping.
  4. NOAA Climate Prediction Center.
  5. Unidata - a diverse community of education and research institutions vested in the common goal of sharing data, tools to access the data, software tools to use and visualize the data, and resources.
  6. Middle-Atlantic Regional Earth Science Applications Center (RESAC)
  7. Phenology links at
  8. Center for Climatic Research - U. of Delaware