Forecasting monsoon rainfall is difficult because it depends on complex interactions of temperature and moisture throughout the lower atmosphere. Current simple models, which combine moisture and instability into a single number, miss important details.
Researchers used a two-step process called symbolic distillation. First, a neural network, a computer model loosely inspired by the brain, learned which vertical layers matter most for rainfall. Then, symbolic regression searched for simple math formulas that fit the network's insights.
The best equation explained about one and a half times more rainfall variation than the standard method and was about a thousand times simpler than the neural network. It revealed that moisture and instability act as opposing controls, with the heaviest rain when the lower free troposphere is humid.
