Unveiling High‐Resolution CH ₄ Profiles Over Southeast China: Novel Insights From AirCore Balloon Observations

Abstract Vertical profiles of methane (CH 4 ) are essential for validating satellite observations and quantifying regional sources and sinks. This study presents the first two high‐resolution CH 4 profiles (0–25 km) over southeastern China, an economically developed region, using AirCore measurements. The profiles exhibited distinct variations: CH 4 increased from 25 to 15 km, remained stable (15–6 km), decreased sharply (6–3 km), then rose toward the surface (∼600 ppb range). While trends align with observations in northwest China, concentrations were higher. Wind patterns and balloon trajectories influenced the profiles, with long‐range air mass transport from coastal megacities elevating upper‐atmosphere CH 4 . Comparisons with TCCON, TROPOMI, and GOSAT‐2 revealed 26–39 ppb discrepancies in column‐averaged CH 4 , exposing resolution limitations and retrieval uncertainties. Pronounced day‐to‐day variability highlight influence from meteorological conditions and regional transport. These findings emphasize the need for higher spatiotemporal resolution monitoring to improve CH 4 assessments and climate modeling.