Seasonal Methane Concentration Variations Related to Rice Cultivation in China

Methane is an important greenhouse gas, and rice cultivation is a major anthropogenic source of methane emissions. Traditional ground-based observations of methane are limited by spatial coverage and temporal continuity, hindering effective capturing of the dynamic process of agricultural activities. Satellite observations provide a new perspective for precisely analyzing the temporal and spatial evolution of methane concentration. The TROPOspheric Monitoring Instrument (TROPOMI), as a new type of sensor mounted on the Sentinel-5P satellite, has a high spatial resolution of 5.5 km×7 km and possesses near real-time observation capabilities. In this study, we apply seasonal and trend decomposition using Loess to extract seasonal and long-term trend components, and then use K-means clustering to analyze the spatiotemporal variations of methane concentrations in China from 2018 to 2022. Furthermore, we categorize the seasonal variations of methane concentration in China into four modes and comprehensively explore the interconnections between these modes and rice cultivation (planting density and patterns). The results indicate that the spatial distribution of methane concentration in China aligns well with the main rice production areas and generally decreases from the southeast coast to the northwest inland regions, with methane concentration increasing year on year from 2018 to 2022. The four-year average increase of methane in most provinces is above 0.6%. In addition, the study identifies the four main seasonal modes (i.e., single-peak, double-peak, triple-peak, and multi-peak), and unconvers their relationship with rice planting density and planting patterns in different regions for the first time, reflecting that regional rice planting is a determinant of the seasonal variation characteristics of methane.