Reconciling Ozone Trend Differences Between NDACC/WMO Ground-based Stations and Satellite COH with Updated LOTUS Regression Model

Stratospheric ozone recovery is continuously monitored by satellite and multiple ground-based (GB) instruments. Satellite measurements give context to the GB localized measurements, especially when broad zonal averages are examined in addition to station centered overpass data. We focus on sites with both Umkehr and Sonde measurements: Boulder, Colorado (40.0°N, 105.3°W), Haute Provence, France (43.9°N, 5.8°E), Lauder, New Zealand (45.04°S, 169.68°E), and Mauna Loa and Hilo, Hawaii (19.5°N, 155.58°W). We also include Arosa, Switzerland (46.8°N, 9.68°E) with nearby Sondes at Payerne, Switzerland (46.82°N, 6.95°E) and Hohenpeissenberg, Germany (47.80°N, 11.02°E). These datasets are quality assured and homogenized. NOAA’s homogenized satellite record (COH) from SBUV(/2) and OMPS provides ozone vertical profiles in zonal averages and station matched overpass records. The NOAA AC4-funded project supported assessment of trends derived from the several NOAA, NDACC, and WMO/GAW records. We present an updated evaluation of stratospheric ozone profile trends with a focus on 2000–2020. Analyses are performed using the updated version 0.8.0 of the Long-term Ozone Trends and Uncertainties in the Stratosphere (LOTUS) Independent Linear Trend regression model. GB and satellite records over the Northern Hemispheric sites of Arosa, Haute Provence, and subtropical Mauna Loa show positive trends in the mid- to upper- stratosphere (10–1 hPa) with trends peaking at ~3%/decade. GB trends in the upper stratosphere at Boulder (NH) and Lauder (SH) are positive, but not statistically significant, while COH overpass trends show statistically significant positive trends at ~3% per decade. In the lower stratosphere (below 50 hPa), trends are variable (small negative to small positive) and have large uncertainties. Additional dynamical proxies were investigated to reduce uncertainties in stratospheric ozone trends. While COH and GB ozone trends did not change, reduction in trend uncertainties was found in the upper stratosphere and at higher latitudes. The use of a tropopause pressure proxy also reduces uncertainty of Umkehr and Sonde trends below 50 hPa for all GB stations.