It can appear in documentation for the Community Land Model , where variables like TG represent ground temperature.
Knowing the will help me provide the exact technical details or summary you need! Boston Harbor Navigation Channel Improvement Project - DTIC tg1.txt
To give you the most helpful text, could you tell me ? For example: Is it part of a programming assignment or script? Did you find it in a scientific dataset or research paper? It can appear in documentation for the Community