Tropospheric ozone has an impact on air quality and acts as a greenhouse gas and therefore plays a role in public and environmental health, as well as climate change, linking the two subjects. Establishing processes and trends in tropospheric ozone, in particular in the free troposphere, above the mixed layer and below the stratosphere, is difficult due to a lack of data. Also, ozone soundings using balloon borne samplers are too scarce to capture the relatively high spatial and temporal variability in the troposphere. Contrary to stratospheric ozone, passive satellite observations have limited access to information about tropospheric ozone. However, new sensors on the next generation of satellite measurements shall have better tropospheric sensing capabilities, and shall require validation.
Tropospheric ozone has an impact on air quality and acts as a greenhouse gas and therefore plays a role in public and environmental health, as well as climate change, linking the two subjects. Establishing processes and trends in tropospheric ozone, in particular in the free troposphere, above the mixed layer and below the stratosphere, is difficult due to a lack of direct observational data. Tropospheric ozone is much more variable in space and time than stratospheric ozone due to transport and chemistry. The frequency and accuracy of the observations should ideally be adjusted to account for this elevated variability. In addition, the balloon borne ozone samplers are optimised for stratospheric observations, which implies sub optimal performance in the troposphere. Therefore, other observational techniques are required to fill the need for observations of tropospheric ozone from non-satellite sources that are more routinely operational. Contrary to stratospheric ozone, passive satellite observations have limited access to information about tropospheric ozone as the TOA down view is largely dominated by the much higher stratospheric loadings across the sensitive regions of the E-M spectrum. However, currently planned missions are envisaged to have better tropospheric ozone sensing capabilities. Also, ozone soundings using balloon borne samplers are too scarce to capture the relatively high spatial and temporal variability in the troposphere.
OMPS
Identified benefit | User category/Application area benefitted | Probability of benefit being realised | Impacts |
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Upcoming satellite missions will have improved capabilities for tropospheric ozone. Sub-orbital observation capacity will be used to assess the satellite data quality. |
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| Improved knowledge of tropospheric ozone will reduce uncertainty in radiative transfer (climate) and improve results for chemistry. |
Identified risk | User category/Application area at risk | Probability of risk being realised | Impacts |
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Tropospheric ozone profile data is relatively scarce and limits applicability to range of activities including tropospheric ozone validation from satellites. |
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| Remaining gap in appropriate data sources to optimally use new satellite data and to understand processes in the troposphere related to the linkage between air pollution and climate change. |
An increase in data on tropospheric ozone is expected from various space-borne platforms with increased capabilities, such as OMPS, TES and TROPOMI and the instruments proposed for Sentinel 4 and 5. However, a reinforcement of the ground based observational capacity is also required to validate these space-borne observations and establish high-quality time series. An increase in the number of ozone balloon borne soundings is not likely due to the high costs involved (material and personnel). There is a potential for tropospheric ozone lidars (using the differential absorption lidar technique) to fill this gap. In the US, a network of tropospheric ozone lidars has been established (TOLNET). Similar initiatives could be pursued in Europe, where a latent tropospheric ozone lidar network could be revived. In Europe, such a network might become part of ACTRIS, the European Research Infrastructure which deals with short-lived greenhouse agents. Similar efforts are required in other areas of the globe to enable full characterisation of tropospheric ozone capabilities by future satellite missions.
An increase in data on tropospheric ozone is expected from various space-borne platforms with increased capabilities, such as OMPS, TES and TROPOMI and the instruments proposed for Sentinel 4 and 5. However, a reinforcement of the ground based observational capacity is also required to validate these space borne observations and establish high-quality time series. The issue is relevant to understand the links between air pollution and climate change. Satellite data alone will likely not suffice to fill the gap.
A measure of success is the increase in the number of available tropospheric ozone profiles.