Spatiotemporal patterns of temperature inversions and impacts on surface PM 2.5 across China

Abstract. Temperature inversions (TIs) strongly regulate the accumulation and dispersion of air pollutants, yet their nationwide impacts on surface PM2.5 remain poorly quantified. Here we integrate high-resolution L-band radiosonde profiles with PM2.5 monitoring data from 2016–2021 to characterize the frequency, strength, thickness, and diurnal variability of TIs – including surface-based inversions (SBIs) and elevated inversions (EIs) – across mainland China. We show that TIs are pervasive, occurring on average 52 % of days, with mean strength of 2.1 °C and thickness of 214 m, and are more common at 08:00 than 20:00 Beijing Time (BJT). Distinct regional patterns emerge: SBIs dominate in northern China, whereas EIs prevail in eastern China. Overall, SBIs are 1.3 °C stronger than EIs. TIs intensify seasonal pollution, with 76 % of PM2.5 episodes coinciding with inversion events. SBI strength correlates positively with PM2.5 concentrations nationwide, while EI parameters show negative associations in eastern and southern regions. These findings reveal the spatiotemporal dynamics of TIs, establish quantitative links to surface pollution, and highlight regionally divergent mechanisms, providing critical insight for air-quality forecasting and targeted emission control.