Symbol Glossary
This document provides a centralized glossary of mathematical symbols used throughout the APSIM NG documentation.
To ensure clarity and avoid confusion between similarly named concepts (e.g. Phyllochron and Photoperiod), we adopt a consistent convention of using two-letter symbols wherever possible.
Symbols are grouped by functional categories such as Phenology, Climate, Soil Water, and General Simulation Variables to reflect their use across the APSIM NG framework.
General Conventions
- Symbols are written in italic, e.g. \(TT\)
- Symbols use two-letter abbreviations to distinguish overlapping concepts (e.g. \(Ph\) for phyllochron, \(PP\) for photoperiod)
- Subscripts clarify properties or context, e.g. \(T_{\text{max}}\), \(Ph_{\text{base}}\)
- Greek letters represent parameters or coefficients, e.g. \(\alpha\), \(\beta\), \(\Delta\)
- Units are expressed in SI unless otherwise noted
🌱 Phenology
| Symbol | Name | Units | Description |
|---|---|---|---|
| \(TT\) | Daily Thermal time | °Cd | Daily thermal time accumulated |
| \(Ph\) | Phyllochron | °Cd | Thermal time required for the appearance of successive leaves on the main stem |
| \(HS\) | Haun Stage | - | Number of fully expanded leaves on the main stem (Haun 1973) |
| \(Ph_{\text{base}}\) | Base phyllochron | °Cd | Base phyllochron for most of leaves |
Notes
- Symbols may appear in multiple modules but should retain their meaning consistently.
- This glossary will evolve as APSIM NG continues to grow — contributions welcome.
See Also
References
Haun, J. R. 1973. “Visual Quantification of Wheat Development.” Agronomy Journal 65: 116. https://doi.org/10.2134/agronj1973.00021962006500010035x.