Reinforcement Learning to Discover a North-East Monsoon Index for Rainfall Prediction in Thailand

TL;DR

This paper introduces a novel reinforcement learning-based method to optimize a regional climate index for improved long-term rainfall prediction in Thailand, demonstrating significant accuracy enhancements in various regions.

Contribution

It presents a new climate index derived from sea surface temperature, optimized via reinforcement learning, to enhance rainfall prediction accuracy in Thailand.

Findings

Optimized index improves rainfall prediction accuracy.

Reduces Root Mean Square Error for 12-month forecasts.

Effective in multiple regional clusters.

Abstract

Accurately predicting long-term rainfall is challenging. Global climate indices, such as the El Ni\~no-Southern Oscillation, are standard input features for machine learning. However, a significant gap persists regarding local-scale indices capable of improving predictive accuracy in specific regions of Thailand. This paper introduces a novel North-East monsoon climate index calculated from sea surface temperature to reflect the climatology of the boreal winter monsoon. To optimise the calculated areas used for this index, a Deep Q-Network reinforcement learning agent explores and selects the most effective rectangles based on their correlation with seasonal rainfall. Rainfall stations were classified into 12 distinct clusters to distinguish rainfall patterns between southern and upper Thailand. Experimental results show that incorporating the optimised index into Long Short-Term Memory models significantly improves long-term monthly rainfall prediction skill in most cluster areas. This approach effectively reduces the Root Mean Square Error for 12-month-ahead forecasts.