Abstract
Lightning is the most important source of nitric oxide (NO) in the
tropical upper troposphere and controls the formation of tropospheric
ozone (O3). It is associated with deep convective processes and occurs
mostly (∼90%) over tropical continents. The Chemistry of the Atmosphere
Field Experiment in the Pacific (CAFE Pacific) was conducted in early
2024 from Cairns, Australia, taking airborne measurements across the
Australian continent and the surrounding maritime regions. Based on
cloud top properties, lightning data and in situ observations of NO, O3
and carbon monoxide (CO), we show that deep convection occurs over both
Northern Australia and the Indo-Pacific Warm Pool. While we identify
strong lightning activity over Australia, deep convection in the Warm
Pool is not electrified. We conclude that low O3 in the Warm Pool is due
to O3-poor air from the marine boundary layer, which is not replenished
by photochemical production from NO at high altitudes.