Co-ordinated Airborne Studies in the Tropics - CAST
1 January 2014 - 28 February 2014
Lead Scientist: Geraint Vaughan
CAST (Co-ordinated Airborne Studies in the Tropics) was a research project funded by the UK’s Natural Environment Research Council with the aim of collaborating with NASA in exploiting the Global Hawk unmanned aircraft. The project had two parts: development of instruments to fly on the Global Hawk and participation in a field campaign conducted in the West Pacific in January/February 2014 to study the Tropical Tropopause layer (TTL). The field campaign was based mainly in Guam and had three components: the ATTREX project organized by NASA and based around the Global Hawk, the NCAR-led CONTRAST campaign based around the Gulfstream V (HIAPER) aircraft, and CAST with the UK’s BAe146 research aircraft. Together, the three aircraft were able to make detailed measurements of atmospheric structure and composition from the ocean surface to 20 km.
The aircraft gave us very detailed snapshots of the atmosphere, but to tie the results together we also needed some ground-based measurements. Ozonesondes, flown with radiosondes, measuring vertical profiles of ozone and meteorological variables from the ground the 30 km, and acted as a bridge between the different aircraft observations. We flew ozonesondes daily for the month of February from the ARM site on Manus Island in New Guinea, and also made continuous measurements of ozone, CH4, CO, CO2, H2O and halogenated hydrocarbons at the ground station during the same period. This allowed us to address the main scientific aim of CAST: to determine how the deep convection and very low ozone concentrations in the tropical warm pool region permit short-lived halogenated compounds to be transported from the surface to the tropical tropopause layer, from where they can enter the stratosphere and play a part in ozone destruction.
Vaughan G. 2016. Co-ordinated Airborne Studies in the Tropics (CAST) Field Campaign Report. Ed. by Robert Stafford, DOE ARM Climate Research Facility. DOE/SC-ARM-15-036.
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