Local verses Long-range Transport ACTIVE Meeting 21/05/09

Ozone Evolution Biomass BurningPre-monsoon Monsoon Monsoon Break

Ozone & CO Evolution

Back Trajectories 10-day back trajectories performed using ECMWF operational data from the trajectory server at the BADC Clustered trajectories were performed to check for consistency initally, with only the central trajectory used thereafter Performed for every ozone sounding (~30) at every 10 hPa between 900 and 200 hPa, and every 5 hPa between 200 and 100 hPa

Back Trajectories e.g.

Back Trajectories Now focus on the TTL region ( hPa): Many of the trajectories reaching the TTL show uplift from low-level We now look at the location these trajectories experience rapid uplift, choosing an arbitrary level of 500 hPa for where these trajectories cross.

Ozone Concentrations

Number of trajectories each represents

Number of days before passing 500 hPa surface

Advected trajectories

Back Trajectories Similar analysis performed for CO: Average background (out-of-cloud) CO concentrations taken for each transect (not vast change in concentration along transect out-of- cloud), and trajectories performed from aircraft location every 30 s. Clustered trajectories not required as consistency could be checked against neighbouring trajectories

CO Concentrations

Conclusions Origin of back-trajectoies show a consistent and coherent pattern which accounts for the variation in both ozone (from sondes) and CO (from aircraft) In general elevated ozone and CO can be attributed to sources over Indonesia, with reduced concentrations observed from the remote maritime Pacific Further supported by those trajectories advected over the course of the ten-days, which follow a similar pattern Thus the TTL above Darwin is governed by the wider tropical warm pool region as opposed to transport from the local boundary layer

Conclusions Occasionally very low ozone was observed above Darwin and tracked to the remote Pacific. Ozone is not destroyed photochemically in the very dry tropical UT, so good evidence for widespread vertical mixing elsewhere, and advected into Darwin

OVERALL “The composition of the TTL is ultimately determined by vertical mixing in certain hot spot regions of the tropics, with advection from these regions dominating the composition elsewhere” Conclusions