CAST – sonde activities Geraint Vaughan This is the footer

Motivation ACTIVE project held in Darwin Nov 2005 – Feb 2006, participated in TWP-ICE Aircraft and ozonesonde measurements in and around the anvils of deep convection Evidence found for influence of warm pool on upper TTL ozone concentrations Heyes, W. J., G. Vaughan, G. Allen, A. Volz-Thomas, H.-W. Pätz and R. Busen. Composition of the TTL over Darwin: local mixing or  long-range transport? Atmos. Chem. Phys. 9, 7725–7736, 2009.

‘Biomass burning’ Monsoon + Break Pre-monsoon Pre-monsoon Pre-monsoon Early November Pre-monsoon Pre-monsoon Pre-monsoon Pre-monsoon

Impressions from ozonesonde profiles Very consistent profiles below 5 km most of the time – little variability Much more variability in the TTL In the active monsoon, profiles consistent with mixing up to 14 km. Very low and very high values in TTL during monsoon period. Suggest little coupling between low levels and the upper TTL, even in the monsoon Now examine aircraft measurements in the thunderstorm anvil regions

Egrett measurements in and near a thunderstorm anvil Measurements in cloud lower for CO and higher for ozone for this flight This air (CO ~ 50 ppbv, O3 ~ 45 ppbv) appears to have been lifted from 6 km, not the boundary layer

Variability in and out of cloud For most flights, CO variability in clear air was much less than in the anvils We adopt the hypothesis that the storms do not perturb the TTL on a larger scale If so, the variability in CO, and in the ozonesonde profiles, should correlate with long-range transport. We examine this hypothesis with trajectory calculations.

Back-trajectory analysis based on ozonesonde ascents 10-day back trajectories performed using ECMWF analyses Performed for every ozone sounding (~30) at every 10 hPa between 900 and 200 hPa, and every 5 hPa between 200 and 100 hPa Clustered trajectories were performed to check for consistency initially, with only the central trajectory used thereafter Many of the trajectories ending in the TTL have ascended from low levels in the previous few days

Ozone Concentrations and locations where trajectories ascended through 500 mb

Back-trajectories from Egrett transects out of cloud with CO values

Conclusions Origin of back-trajectories show a consistent and coherent pattern 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 Thus the TTL above Darwin is governed by the wider tropical warm pool region as opposed to transport from the local boundary layer Are these conclusions correct for large MCSs such as those found in the Tropical Warm Pool? Is this how air with very low ozone concentrations reached the TTL?

Nominal Global Hawk flights Guam Chuuk Jan 2014 - Proposed Measurements Dirac (VSLS) SHADOZ Nominal Global Hawk flights

Provision for up to 60 ozonesonde packages Ozonesondes Provision for up to 60 ozonesonde packages Could include hygrometers and/or aerosol sondes (and so fewer launches) Current plans are to launch from Chuuk, site visit next week. Other sites also considered. Possibly augment launches from other sites Exact plans need to be developed with partners Data will be used to investigate transport, vertical coupling and waves.

Lidar will (probably) be deployed at Chuuk during campaign Will enable measurements of cirrus clouds Leosphere ALS300 – 355 nm, dual polarisation Time and height resolution variable SVC likely to be possible only at night