G2.10    Tropospheric O3 profile data is limited

Gap detailed description

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 lack of data. Contrary to stratospheric ozone, passive satellite observations have limited access to information about tropospheric ozone. Also, ozone soundings using balloon borne samplers are too scarce to capture the relatively high spatial and temporal variability in the troposphere.

Activities within GAIA-CLIM related to this gap

This gap will not be addressed within GAIA-CLIM. However, ongoing activities in other projects will be monitored and reported on.

Gap remedy(s)

Specific remedy proposed

An increase in data on tropospheric O3 is expected from various space-borne platforms with increased capabilities, such as TES and TROPOMI. However, a reinforcement of the ground based observational capacity is also required to validate the space borne observations and establish high-quality time series. An increase in the number of O3 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 O3 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, which deals with short-lived greenhouse agents.

Measurable outcome of success

A measure of success is the increase in the number of available tropospheric ozone profiles.

Achievable outcomes

Technological viability: low.

Indicative cost estimate: high (>5million).  Installation of new tropospheric ozone lidar systems, or refurbishment in a small network would be a fairly large undertaking.


The issue is relevant to understand the links between air pollution and climate change. Satellite data will likely not suffice to fill the gap.



Gap risks to non-resolution

Identified future risk / impact

Probability of occurrence if gap not remedied

Downstream impacts on ability to deliver high quality services to science / industry / society

Tropospheric O3 profile data is limited and limits applicability to range of activities including tropospheric ozone validation from satellites.


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.


Work package: