Reliability assessment of seasonal frozen soil automatic observer

This study evaluated the reliability of five types of seasonal frozen soil automatic observers (DTD1, DTD2, DTD3, DTD4, and DTD5) using parallel observation data collected from 1,172 meteorological observation stations across 24 provinces (cities, districts) in China from 2020 to 2024. The assessment was based on five key indicators: data integrity rate (with a qualified threshold of 98.00%), data standard deviation (threshold of 2.00 cm), comparable data agreement rate (threshold of 80.00%), comparable data misjudgment mean (threshold of 6.00 cm), and maximum frozen soil depth data correlation (threshold of 0.80). These indicators were used to comprehensively assess the reliability of the equipment. Over the five-year period, each set of equipment progressed through three stages: in the first stage, manual observation is predominant, in the second stage, automatic observation takes precedence, and in the third stage, the system operates independently. Equipment types achieving an independent operation rate exceeding 75% were deemed to meet the reliability standards. By the end of 2024, the independent operation rates for DTD1, DTD2, DTD3, DTD4, and DTD5 were 20.00%, 88.73%, 88.24%, 35.03%, and 23.56%, respectively. Notably, the DTD2 and DTD3 models met the reliability evaluation criteria. These findings provide a robust basis for the selection and deployment of seasonal frozen soil automatic observers in future meteorological observation networks.