Lightning-produced NO x over Brazil during TROCCINOX: airborne measurements in tropical and subtropical thunderstorms and the importance of mesoscale convective systems

摘要: Abstract. During the TROCCINOX field experiments in February–March 2004 and February 2005, airborne situ measurements of NO, NOy, CO, O3 mixing ratios J(NO2) photolysis rate were carried out anvil outflow thunderstorms over southern Brazil. Both tropical subtropical investigated, depending on location South Atlantic convergence zone. Tropical air masses discriminated from ones according to higher equivalent potential temperature (Θe) lower mid troposphere, CO ratio wind velocity upper troposphere within Bolivian High (north jet stream). thunderstorm penetrations, typically at 20–40 km horizontal scales, NOx distinctly enhanced absolute varied between 0.2–1.6 nmol mol−1 average. This enhancement was mainly attributed production by lightning partly due upward transport NOx-richer boundary layer. In addition, occasionally enhanced, indicating For first time, composition a large, long-lived mesoscale convective system (MCS) advected northern Argentina Uruguay investigated more detail. Over scale about 400 km, NOx, significantly these range 0.6–1.1, 110–140 60–70 mol−1, respectively. Analyses trace gas correlations Lagrangian particle dispersion model indicate that polluted masses, probably Buenos Aires urban area biomass burning regions, uplifted MCS. Ozone aged MCS outflow, photochemical entrainment O3-rich – stratosphere region. The transported north, ascended circulated, driven Amazon basin. observed case, remained continent did not contribute ozone maximum.