Observations of ozone production in a dissipating tropical convective cell during TC4

Abstract

From 13 July–9 August 2007, 25 ozonesondes were launched from Las Tablas, Panama as part of the Tropical Composition, Cloud, and Climate Coupling (TC4) mission. On 5 August, a strong convective cell formed in the Gulf of Panama. World Wide Lightning Location Network (WWLLN) data indicated 563 flashes (09:00–17:00 UTC) in the Gulf. NO₂ data from the Ozone Monitoring Instrument (OMI) show enhancements, suggesting lightning production of NOx. At 15:05 UTC, an ozonesonde ascended into the southern edge of the now dissipating convective cell as it moved west across the Azuero Peninsula. The balloon oscillated from 2.5–5.1 km five times (15:12–17:00 UTC), providing a unique examination of ozone (O₃) photochemistry on the edge of a convective cell. Ozone increased at a rate of ~1.6–4.6 ppbv/hr between the first and last ascent, resulting cell wide in an increase of ~(2.1–2.5) × 10⁶ moles of O₃. This estimate agrees to within a factor of two of our estimates of photochemical lightning O₃ production from the WWLLN flashes, from the radar-inferred lightning flash data, and from the OMI NO₂ data (~1.2, ~1.0, and ~1.7 × 10⁶ moles, respectively), though all estimates have large uncertainties. Examination of DC-8 in situ and lidar O₃ data gathered around the Gulf that day suggests 70–97% of the O₃ change occurred in 2.5–5.1 km layer. A photochemical box model initialized with nearby TC4 aircraft trace gas data suggests these O₃ production rates are possible with our present understanding of photochemistry.