Co-ordinated Airborne Studies in the Tropics (CAST)

The unique research capability of the Global Hawk, with ultra-long flights possible in the upper troposphere and lower stratosphere, provides a major new opportunity to advance atmospheric science. In response to the NERC/STFC/NASA collaborative initiative, we have assembled an experienced UK team that proposes to execute a research programme covering fundamental science and technology development, which, by working with the Global Hawk, will radically enhance our future research capabilities.

The Tropical Tropopause Layer (TTL) is a crucial region for chemistry/climate interactions. Building on work we have already done in this area, we will collaborate with NASA's ATTREX programme to study the TTL over the Pacific Ocean and South East Asia, with new measurements and analysis. We will address fundamental questions related to atmospheric composition, radiation and transport. The TTL controls the transport of water vapour, the crucial radiative gas, into the stratosphere; we will advance understanding of the role of sub-visible cirrus in water vapour processes. The TTL is also the main route by which very short-lived halogen species, which represent a large uncertainty in future stratospheric ozone evolution, enter the stratosphere. We will improve knowledge of the budgets of these gases and of their chemical transformation and transport through the TTL, including the role of convective transport into the TTL and the subsequent routes for transport from the TTL to the lower stratosphere. Improving representation of these processes in global chemistry/climate models is a key aim.

In order to study these processes, The FAAM BAe-146 will be deployed in Guam in Jan/Feb 2014. It will fly coordinated flights with the Global Hawk which will making measurements in the same period in the TTL over the West Pacific. Detailed involvement in all phases of the collaborative missions with ATTREX will enhance the UK potential for future research using the Global Hawk, including advanced capability in mission planning and methodologies for complex, real-time data analysis. The aircraft measurements will be interpreted in conjunction with ground-based and balloon-based measurements of very short-lived halogen species and ozone, using a complementary group of regional high resolution models, global composition models and a global cirrus model.

We will develop and test two new instruments and new software for the payload/mission-scientist interface, which are ideally suited for the capabilities of the Global Hawk. One new instrument will allow quantification in the TTL of the important physical properties of sub- and super-micron sized particles, allowing new information about clouds and radiation. We will develop a new short-wave IR spectrometer to measure greenhouse (CO2, CH4, and H2O) and other (CO) gases in the lower atmosphere by remote sensing, taking advantage of the very long flights in the upper troposphere and lower stratosphere. Both instruments will be flight-tested in CAST.

Policy makers, atmospheric scientists and the general public makers will be among the long term beneficiaries of this research. The work relates to two major policy questions; the control of halogenated substances, regulated under the Montreal Protocol, and climate change, the topic of the Kyoto Protocol. Our science will inform the international assessment processes and will be of direct interest to government departments, chiefly DECC and DEFRA.

The general public has a keen interest in global change, in general, and ozone depletion, in particular. It remains extremely important to engage with the public, to provide latest scientific evidence related to these issues, to counter the increasing levels of misinformation being propagated. We will engage with these various groups in a number if ways: through formal and informal meetings, through the peer-reviewed literature and through our web pages. Nearly all PIs give popular lectures on environmental change issues at e.g. schools and will continue to do so. We also often speak to the media.

There is a large number of people in science, the private sector and government who are interested in understanding the capabilities that can be developed for atmospheric observation from UAVs as well as what the potential uses are. CAST will inform and engage with this community in order to share the experience from CAST and to learn from the experience of others. This has the potential to develop a real UK presence in the field of UAV use and research.

CAST will provide career development for PhD students and PDRAs through involving them in the planning and implementation of field campaigns and presentations of results at project meetings, international conferences and in the peer-reviewed literature. In addition all people involved in CAST will learn about the planning and uses for UAVs.