G1.15

G1.15 Northern Hemisphere bias in NDACC and PANDORA network sites distribution

Gap detailed description

NDACC and PANDORA total column O₃ observation sites are concentrated in Europe and the US. There is definitely a strong bias towards Northern Hemisphere mid-latitudes and a lack of measurements in Asia, the tropics and Southern latitudes. (Note also that NDACC stations often include a variety of instruments measuring total column ozone such as UV/visible spectroscopy, MAX-DOAS, Brewer, Dobson, LIDAR, ozonesonde, FTIR).

The lack of coverage in space and time limits the potential of the networks for e.g. latitudinal dependencies and global trend studies, climate change detection, satellite validation and long-term assessment of ECVs such as O₃. This gap is partially addressed within GAIA-CLIM.

Activities within GAIA-CLIM related to this gap

This will be addressed but only in terms of the development of strategies and suggestions for network extensions, not in terms of implementation.

Gap remedy(s)

One potential remedy is foreseen and explained in more detail below.

Remedy

Specific remedy proposed

Develop strategies for network extension, and long-term preservation of data and measurement capabilities based on an in-depth study of the capabilities of the existing sites as well as a literature study on what distribution patterns would be most desirable (e.g. Kreher et al., 2015).

Measurable outcome of success

A measure for success would be that the suggested strategies and recommendations are picked up by any of the networks and will provide them with useful support for their specific network development strategies. 

Achievable outcomes

Technological / organizational viability: medium

Indicative cost estimate: low (<1 million)

Relevance

An important requirement for an observational network to provide a global picture of e.g. O₃ trends is that the measurement sites are strategically placed and sample a sufficiently diverse range of regimes. Most of the current measurement sites, however, are located close to populated areas and with around 90% of the global population living in the Northern Hemisphere, measurement sites clearly favour the Northern Hemisphere. As a result, such a distribution of sites is unlikely to be representative of the global climate and hence the need exists to provide a range of methods to determine the optimal location of sites and to advice on network extension taking into account the different nature of each of the networks of relevance.  

Timebound

It will take the approximately 1 year to develop and apply the suggested strategic remedy. 

Gap risks to non-resolution