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Observations & Modelling of the Tropical Tropopause Layer

Programme background

This programme aims to enable UK participation in exciting and high impact unmanned aerial vehicle enabled science, through collaboration with NASA partners in the existing Airborne Tropical Tropopause Experiment (ATTREX) mission.

This initiative follows on from a NERC hosted event in May 2010 to raise UK community awareness of NASA priorities and capability in next generation high altitude platforms, as well as to explore the potential benefits of such platforms for the delivery of NERC science.

This programme forms part of the NERC technologies and climate system themes to:

1. Improve understanding of upper troposphere lower stratosphere processes, including delivering those observations needed to reduce uncertainty in climate models through improved parameterisations, and contributing to wider goals of the NERC climate system theme; and

2. Stimulate technology development to meet the NERC technologies theme challenges associated with next generation platforms, remote sensing instruments, in situ sensors and modelling technology.

This programme will support a collaborative programme of research, with the existing NASA ATTREX mission deploying the Global Hawk UAV and the NERC/Met Office FAAM146 aircraft in combination.

Furthermore, the programme will benefit from a Technology Partnership Scheme with the Science & Technology Facilities Council (STFC), which will provide up to £600k in additional in-kind technology, facilities and expertise.

The joint programme will reduce climate uncertainties associated with upper troposphere and lower stratosphere (UTLS) processes, through a combination of measurements and models. The programme will also support the development of key instrument technologies that will position the UK for future co-design of missions with NASA.

The upper troposphere and lower stratosphere are key atmospheric regions for determining global radiation and energy budgets. Small changes in lower stratospheric water vapour and ozone for example have potential climate impacts that are significant when compared to those of decadal increases in greenhouse gases, and changes in stratospheric humidity and ozone as a result of global change are significant climate feedbacks.

Exchange across the tropopause is dominated by physical processes that occur in tropical regions. The energy at the tropics enables air to loft rapidly via deep convection into the tropical tropopause layer (TTL), a distinct intermediate layer between free troposphere and stratosphere (TTL - typically 13-18 km), from where it may then move more slowly into the lower stratosphere, making this region particularly suitable for investigation.

Improved understanding of the TTL can be subsequently translated in to better parameterisations of water and cirrus processes within climate models and increased confidence in the estimation of TTL effects on radiation and energy budget over long timescales.

This programme will enable the UK to partner with US researchers in an ambitious mission to study TTL composition changes and radiation using Global Hawk aircraft.