Total Ozone Column Changes over Northeast China: Trends and Variability Analysis

Based on the Multi-Sensor Reanalysis Version 2 (MSR-2) and ERA5 datasets, variations in monthly mean total ozone column (TOC) over Northeast China (40–53°N, 115–135°E) from 2015 to 2024 are analyzed. Local ground-based observations at the regional WMO/GAW Longfengshan Station are also used. The aim is to investigate regional seasonality in TOC pattern and the relationship between TOC and ozone concentration and air temperature in the stratosphere and at the surface. No statistically significant linear trend was found for TOC; however, the annual mean TOC in the study region exceeds the zonal mean TOC by 25 DU (7.4%), and the annual maximum in February and minimum in August are observed one and two months earlier, respectively, than in the Northern Hemisphere mid-latitudes. A climatological decrease in TOC from the northeastern (~415 DU) to southwestern (~330 DU) parts of Northeast China was found. We also found a strong correlation, approaching |r| = 0.8–0.9, between TOC and ozone concentration (positive) and temperature (negative) at the surface. The time series from Longfengshan Station for 2015–2022 closely match the MSR-2 data averaged over Northeast China: the monthly mean difference varies within ±15 DU (±4.2%), validating the reliability of the station data as a representative proxy for regional TOC variability. The role of the Brewer–Dobson circulation, quasi-stationary waves, and the Northeast China cold vortex in the detected patterns and quantitative associations of TOC is discussed. The findings of this work can be applied to analyze the ozone observations, TOC variability, and stratosphere–troposphere coupling in East Asia.