Abstract

Lightning is estimated to produce around 10% of global annual NOx emissions. While not the largest NOx source, lightning has particular importance because it emits directly into the free troposphere instead of at the surface. As a result, it is a key control on ozone production in the tropical upper troposphere. As a natural emissions source, lightning also has the potential to vary with climate change if its meteorological drivers are affected.

The parametrisation of lightning in most climate-chemistry models uses cloud top height as a proxy. This approach is known to contain large errors but there are few robust alternatives. I will present the development of an alternative parametrisation using upward ice flux which is more closely linked to thunderstorm charging theory. Comparisons are made between our ice flux-based parametrisation and existing parametrisations. The upward ice flux approach is then implemented in the climate-chemistry model, UKCA . UKCA is used to explore the differences in tropospheric ozone chemistry between the cloud top height approach versus the upward ice flux approach.