How to most effectively expand the global surface ozone observing network

Abstract

Abstract. Surface ozone observations with modern instrumentation have been made around the world for more than 40 years. Some of these observations have been made as oneoff activities with short-term, specific science objectives and some have been made as part of wider networks which have provided a foundational infrastructure of data collection, calibration, quality control, and dissemination. These observations provide a fundamental underpinning to our understanding of tropospheric chemistry, air quality policy, atmospherebiosphere interactions, etc. Sofen et al. (2016) brought together eight of these networks to provide a single data set of surface ozone observations. We investigate how representative this combined data set is of global surface ozone using the output from a global atmospheric chemistry model. We estimate that on an area basis, 25 % of the globe is observed (34 % land, 21 % ocean). Whereas Europe and North America have almost complete coverage, other continents, Africa, South America, Australia, and Asia (12-17 %) show significant gaps. Antarctica is surprisingly well observed (78 %). Little monitoring occurs over the oceans, with the tropical and southern oceans particularly poorly represented. The surface ozone over key biomes such as tropical forests and savanna is almost completely unmonitored. A chemical cluster analysis suggests that a significant number of observations are made of polluted air masses, but cleaner air masses whether over the land or ocean (especially again in the tropics) are significantly under-observed. The current network is unlikely to see the impact of the El Niño-Southern Oscillation (ENSO) but may be capable of detecting other planetaryscale signals. Model assessment and validation activities are hampered by a lack of observations in regions where the models differ substantially, as is the ability to monitor likely changes in surface ozone over the next century.Using our methodology we are able to suggest new sites which would help to close the gap in our ability to measure global surface ozone. An additional 20 surface ozone monitoring sites (a 20 % increase in the World Meteorological Organization Global Atmosphere Watch (WMO GAW) ozone sites or a 1 % increase in the total background network) located on 10 islands and in 10 continental regions would almost double the area observed. The cost of this addition to the network is small compared to other expenditure on atmospheric composition research infrastructure and would provide a significant long-term benefit to our understanding of the composition of the atmosphere, information which will also be available for consideration by air quality control managers and policy makers.

A review of atmospheric chemistry observations at mountain sites

“…The second is located in a high-altitude basin known as the Altiplano, Bolivia (Rose et al 2015). Sofen et al (2016) indicated that the current monitoring network of surface O 3 (including low-altitude stations) is insufficient for measurements in key regions (China, India, Amazon, Africa, tropical oceans, and Southern Ocean) and suggested the establishment of 20 possible sites (10 island and 10 continental). A strategy should be implemented to facilitate observations of key species in areas in which few observatories are located.…”

Tropospheric Ozone Assessment Report: Assessment of global-scale model performance for global and regional ozone distributions, variability, and trends

“…In situ and satellite observations provide a substantial amount of information on the present day tropospheric ozone distribution and its variability and trends over the recent past (Tarasick et al, 2017, hereinafter referred to as TOAR-Observations; Gaudel et al, 2017, hereinafter referred to as TOAR-Climate), but there are important gaps in our knowledge (Cooper et al, 2014). Many regions of the world, including remote oceans and continental areas like Africa, South America, the Middle East, and India, remain under-sampled leading to incomplete knowledge of the horizontal, vertical and temporal distribution of ozone (Oltmans et al, 2013;Cooper et al, 2014;Lin et al, 2015a;Sofen et al, 2016a). Furthermore, observational estimates of the preindustrial ozone burden are highly uncertain (TOAR-Observations) making it difficult to accurately quantify the preindustrial to present day ozone changes and the resulting radiative forcing on climate and air quality impacts.…”

“…One issue of representativeness relates to the fact that the atmosphere is not completely sampled (Sofen et al, 2016a(Sofen et al, , 2016bTOAR-Observations), meaning that there are important locations and times where there are no constraints for the model (e.g., a globally sparse distribution of monitoring stations, coarse vertical data from satellites, poor constraints on pre-industrial ozone). Given the incomplete sampling, the primary issue for representativeness where we have observations relates to the fact that the spatial and temporal resolutions of global models are necessarily coarse.…”

Tropospheric Ozone Assessment Report: Database and metrics data of global surface ozone observations

“…Prior attempts to summarize the global distribution of tropospheric ozone and its trends (e.g. Cooper et al, 2014;Sofen et al, 2016a) were limited to readily accessible data from large networks maintained by the World Meteorological Organisation, and North American, and European institutions, which introduced substantial geographical bias in the analyses. In the framework of TOAR the most comprehensive database possible of global surface ozone observations has been established at Forschungszentrum Jülich in Germany.…”