This study presents an automated meteorological data management system with an AI agent to calculate ETo by applying the standard FAO-56 Penman Monteith (PM) equation. The proposed framework automatically performs meteorological data acquisition, quality control (QC), management, ETo calculation, aggregation, visualization, and statistical evaluation. This study used daily meteorological data from 21 Automated Synoptic Observing System (ASOS) stations in the Nakdong River Basin, Republic of Korea, covering 2011 to 2023, and integration of API-retrieved meteorological data began from 2024 onward. The automated ET₀ results were compared with conventionally calculated PM-based potential evapotranspiration (PET) using RMSE, MAE, PBIAS, and R2. Findings are consistent across all stations, with monthly RMSE mostly less than 0.7 mm (maximum 1.14 mm), MAE less than 0.7 mm, PBIAS in the range -0.465–0.833%, and R2 in the range 0.999–1.000. The results indicate that the automated workflow maintained the physical consistency of ETo estimation and improved reproducibility and applicability. The proposed system may support operational agricultural water management in the Nakdong River Basin.

Abstract
Introduction
Materials and Methods
    1. Study area
    2. Data acquisition and quality checking
    3. Methodology
Results
Discussion
References

• Jihyun Son(Undergraduate Student, Department of Agricultural Engineering, College of Agriculture and Life Sciences, Gyeongsang National University, Jinju, 52828, Korea)
• Muhammad Waqas(Senior Researcher, Department of Agricultural Engineering, College of Agriculture and Life Sciences, Gyeongsang National University, Jinju, 52828, Korea)
• Sang Min Kim(Professor, Department of Agricultural Engineering, College of Agriculture and Life Sciences, Gyeongsang National University, Jinju, 52828, Korea) Corresponding author