The convective transport of active species in the tropics (Contrast) experiment

Airborne observations over the tropical western Pacific (TWP) warm pool characterize the role of tropical convection in linking oceanic processes to ozone chemistry in the upper troposphere and lower stratosphere. The CONTRAST (convective transport of active species in the tropics)experiment succeeded in obtaining a large suite of trace-gas measurements, together with dynamical and microphysical variables, under a wide range of conditions over the TWP. The intensive sampling of actinic flux, ozone, water vapor, and other active species will allow constrained photochemical calculation of hydroxyl radical over the TWP, which will lead to a better understanding of the processes that control atmospheric oxidation capacity in the tropical western Pacific. The flights successfully sampled air masses in convective updraft and outflow both near and downstream of active convection. The data will enable individual case studies and statistical quantification of the impact of convection and convective transport on the vertical distribution of a wide range of compounds with different photochemical lifetimes. Finally, CONTRAST data provided the first intensive in situ observations of ozone in the TTL(tropical tropopause layer) over the oceanic warm pool. The measurements filled an important data gap by coordinating in situ measurements with collocated ozonesonde profiles, which resulted in a new understanding of ozonesonde uncertainty and quantified the low-ozone level over the TWP TTL. CONTRAST also led to the discovery of a bimodal ozone distribution in the free troposphere between 3 and 9 km over the TWP.