Atmospheric Chemistry and Physics 

The purpose of the special issue (SI) is the collection of relevant contributions on the detection, analysis, and prediction of long-term changes and trends of trace gases and physical parameters of the atmosphere from the upper troposphere up into the ionosphere as presented at the TRENDS2022 workshop (11th International Workshop on Long-Term Changes and Trends in the Atmosphere). The SI will be open for contributions to the TRENDS2022 conference and co-located SPARC LOTUS and SPARC ATC working group meetings, as well as for other publications directly related to the scope of the SI.

The Tibetan Plateau is referred to as the third pole of the world and is representative of background region of the Earth’s atmosphere. Atmospheric photochemistry, in conjunction with the unique circulation pattern of Asian Monsoon outflow and prevailing westerly wind, leads to, as of yet, unidentified implications for climate change, the oxidative capacity of the atmosphere, local air quality, and health effects on local residents and visitors.

For a better scientific understanding of the background atmospheric chemistry and its impacts on climate change, air quality, and human health, multiple international campaigns, referred to as the @Tibet field campaigns, have been conducted since 2019 under the umbrella of the second Tibetan Plateau Scientific Expedition and Research Program (STEP). As supported by the major research plan of the National Natural Science Foundation of China (NSFC) entitled fundamental researches on the formation and response mechanism of air pollution complex, the research conducted in the Tibetan Plateau and eastern China was underpinned by a number of instrument developments required to meet the specific demands of exploring air pollution and fundamental atmospheric photochemistry. This AMT–ACP joint special issue is therefore designed to intensively discuss data from @Tibet field campaigns and instrument development progress.

Geostationary Environment Monitoring Spectrometer (GEMS) is the first instrument to observe air quality from a geostationary Earth orbit (GEO) successfully launched on 19 February 2020 and in initial operation after in-orbit tests (IOTs). GEMS provides hourly air quality information on both aerosols and gases at unprecedented spatial resolution of 7 km × 8 km. GEMS is a scanning UV–visible spectrometer measuring the hyperspectral spectrum in the ultraviolet and visible, which allows for the observation of key atmospheric constituents including O₃, NO₂, CO, SO₂, CH₂O, CHOCHO, aerosols, clouds, and UV indices. The mission opened a new era of air quality monitoring from space and will be joined by NASA’s TEMPO and ESA’s Sentinel-4 to form the GEO Air Quality Constellation in ~3 years to cover the most polluted region in the Northern Hemisphere. In this ACP–AMT special issue, the first results will be presented including instruments, IOT results, initial products, algorithm, calibration, validation from the recent GMAP field campaign, applications in modelling, etc.

Atmospheric ozone is one of the most important trace gases in the Earth's atmosphere due to its multiple roles: filtering harmful levels of ultraviolet (UV) solar radiation and shortwave absorption, being a greenhouse gas in the Earth's climate system, and being a powerful oxidant in the troposphere. Also, surface level ozone produces harmful effects on human health, ecosystems, and agricultural production. The latest findings and emerging research on ozone-related topics were presented at the 2021 Quadrennial Ozone Symposium (QOS) held online on October 3–9 2021. This special issue covers studies presented at the QOS and other relevant studies that are broadly related to the following subject areas:

1. stratospheric ozone science;
2. tropospheric ozone science;
3. ozone-depleting substances sources, sinks, and budget;
4. ozone, climate, and meteorology;
5. ozone monitoring and measurement techniques;
6. environmental and human health effects of atmospheric ozone and UV radiation.

This issue is open to all submissions within its scope.

Clouds over the ocean and their radiative properties are partially influenced by the biology, biogeochemistry and physics of the surface ocean. For example, the production of sea spray via bubble bursting associated with breaking waves can be influenced by biogenic material present in surface seawater, and biogenic material carried in sea spray aerosol can also influence ice-nucleating properties in air overlying the ocean. Furthermore, phytoplankton produce a range of compounds, including gases and particles, which when emitted to the atmosphere participate in the atmospheric chemistry. Our recent ship campaign Sea2Cloud had a primary focus of investigating the link between marine particle emissions and the biogeochemical properties of the seawater in subantarctic and subtropical waters, examining new particle formation processes and the relationship between surface ocean biogeochemistry and sea spray aerosol in dedicated ship-borne experiments. In parallel, ambient air aerosol, gas and cloud properties were measured along the ship track, which will allow for testing of these relationships in modelling exercises. Along with the ship campaign, longer-term measurements of aerosol properties were monitored at the Baring Head GAW research station (NZ) as well as continuously ongoing onboard the R/V Marion Dufresne over the years 2021–2022. These measurements will be used for the inspection of the representativeness of the ship campaign's process-orientated results. The Sea2Cloud project is running from July 2018 to July 2023, with potential additional laboratory and ship-borne measurements in the Southern Ocean by January 2023.