Co-ordinated Airborne Studies in the Tropics - CAST

Lead Research Organisation: University of Cambridge
Department Name: Chemistry


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 make 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.

As well as addressing the specifics of this call, CAST addresses the central vision of the Technology theme: "to engage scientists, technologists, computer specialists and engineers working both within the NERC community and outside it, identifying that in many cases it will only be through developing new partnerships that the most challenging innovations in technology can be enabled" ( CAST brings new technology expertise in machine learning into the NERC community and strengthens the links between NERC scientists and the technology groups at Hertfordshire and the Astronomy Technology Centre.

Planned Impact

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.


10 25 50
Description CAST has progressed well with a successful aircraft campaign in Guam and a ground-based deployment in Manus, Papua New Guinea in Jan/Feb 2014. This campaign also involved the NASA Global Hawk and the NSF Gulfstream V research aircraft. Close collaboration was achieved during and after the campaign as evidenced by coordinated flights, two joint science meetings, and many joint, published publications including three high profile, overview papers in BAMS describing the 3 campaigns.

In addition two new instruments have been developed. These were successfully flown on the Global Hawk in early 2015 and the results are currently being worked up. One is being developed into a UK small satellite project, and the other is being used on other platforms.

The main results to date reveal the extensive existence of air affected by biomass burning across the Pacific, and detailed information about how short-lived compounds are lofted into the Tropical Tropopause Layer.
Exploitation Route There are no direct, non-academic uses resulting from this project. Important, indirect benefits include improved weather forecasts through improved knowledge of strong convection; better understanding of the role of the tropics in radiation (through clouds) and trace gas distributions; and a new instrument to infer greenhouse gas emissions over large geographic areas. Known exploitation routes include published research papers, preparation of results for use in international assessments, promotion of the scienctific results and techniques in the non-specialist arena, including an assessment of the utility of UAVs in research. Other routes will become clearer once the findings become clear.
Sectors Environment

Description The findings have been used in the WMO/UNEP Scientific Assessment of Ozone Depletion in 2014 and 2018 and now in 2022. They have been used to understand halocarbon budgets in the Tropical Tropopause Layer will inform climate models about the impact of tropical convection on the upper atmosphere, including how natural and anthropogenic emissions are transported.
First Year Of Impact 2014
Sector Environment
Impact Types Policy & public services

Description Appointed review editor for Chapter on Policy Implications in the 2018 WMO/UNEP Scientific Assessment of Ozone Depletion
Geographic Reach Multiple continents/international 
Policy Influence Type Participation in a guidance/advisory committee
Description Airborne Holographic Imaging Probe
Amount £106,020 (GBP)
Funding ID NE/T009144/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 09/2019 
End 03/2020
Description Atmospheric Composition and Radiative forcing changes due to UN International Ship Emissions regulations (ACRUISE)
Amount £363,917 (GBP)
Funding ID NE/S004467/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 02/2019 
End 02/2023
Description CLouds and Aerosol Radiative Impacts and Forcing: Year 2016 (CLARIFY-2016)
Amount £605,765 (GBP)
Funding ID NE/L013584/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 01/2016 
End 12/2020
Description Characterisation and Modelling of Climatically Relevant Primary Biogenic Ice Nuclei in the BEACHON Southern Rocky Mountain Project
Amount £244,499 (GBP)
Funding ID NE/H019049/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 03/2011 
End 09/2013
Description Demonstration of an Aircraft System for Real-Time Discrimination & Reporting of Dust, Volcanic Ash, Ice and Super-cooled Water Particles.
Amount £142,070 (GBP)
Funding ID NE/I023058/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 10/2011 
End 08/2014
Description Collaboration with ECMWF 
Organisation European Centre for Medium Range Weather Forecasting ECMWF
Country United Kingdom 
Sector Public 
PI Contribution ECMWF will be external partners to this project providing meteorological information for flight planning during the field campaign and being involved in studies of trace gases in strong convection.
Start Year 2012
Description Collaboration with NASA ATTREX 
Organisation National Aeronautics and Space Administration (NASA)
Department NASA Dryden Flight Research Centre
Country United States 
Sector Public 
PI Contribution We have worked closely with NASA ATTREX to lay good foundations for the joint aircraft campaign in Jan/Feb 2013. The activities have included the ATTREX PI attending the CAST kick-off meeting, joint attendence at a workshop to discuss the science and planning for the campaigns, and a visit to learn about the NASA Global Hawk operations and flight planning during the second phase of ATTREX. NERC have signed one Agreement with NASA covering all CAST-ATTREX activities and as a second specifically about the direct UK in the Global Hawk is close to signing.
Collaborator Contribution NASA provided the Global Hawk
Impact Good coordination of flights. Joint science team meeting held in Boulder, CO in October 2014.
Start Year 2012
Description Collaboration with NSF CONTRAST 
Organisation National Science Foundation (NSF)
Country United States 
Sector Public 
PI Contribution Measurements from the ground to 20 km were made from Guam in the West Pacific in Jan/Feb 2014 as part of a NERC/NASA/NSF three aircraft collaboration looking at the impact of convection on the tropical UTLS. The NERC BAe-146 made low level measurements. Ground-based and sonde measurements were made in Manus (PNG) in the same period.
Collaborator Contribution NSF supported the deployment of their HIAPER atmospheric research aircraft in the joint deployment in Guam with the NERC BAe-146 and the NASA Global Hawk.
Impact All flights performed with good coordination between campaigns. Science team meeting held in Boulder CO in October 2014
Start Year 2013
Company Name Droplet Measurement Technologies LLC 
Description Droplet Measurement Technologies is a major manufacturer, developer of instruments for monitoring black carbon, bioaerosols, cloud droplets, or other aerosols. 
Year Established 2004 
Impact As a result of work with University Hertfordshire DMT funded a Tier 3 Aerosol CDT PhD studentship at Manchester
Description Exhibit at Royal Society Summer Exhibition 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact We hopefully enthised lots of people of all ages about atmospheric science. It left us absolutely knackered. Great experience.

Nothing direct.
Year(s) Of Engagement Activity 2014
Description Open day in Guam 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Many inhabitants of Guam visited the airport to see our two research aircraft and to see what we were doing, learn why and see how the planes and instruments worked. This open day was supplemented by work in the local media and in schools.

n/a - just generally increased interest
Year(s) Of Engagement Activity 2014