Do More Frequent Temperature Inversions Aggravate Haze Pollution in China?

By using twice daily high-resolution radiosonde observations, here we assessed spatiotemporal variability of temperature inversion (TI) and its impact on PM_2.5 pollution levels in China from 2014 to 2020. It was found that both surface-based inversion (SBI) and elevated inversion (EI) became increasingly frequent across China, at a rate of 1.42% a⁻¹ (1.15% a⁻¹) and 2.82% a⁻¹ (3.23% a⁻¹) at 0800 (2000) Beijing time (BJT), respectively. However, the intensity of SBI and EI at 0800 (2000) BJT decreased at −0.17 (−0.43) and −0.07 (−0.05) °C 100m⁻¹ decade⁻¹, making annual mean PM_2.5 increment induced by TI dip by 52.5% (73.2%) for the whole study period. Still positive TI induced PM_2.5 increments demonstrate an offsetting effect between TI and emission control on haze pollution, underscoring the importance of fully considering TI contribution when assessing the emission control effect on haze reduction.