Coordinated Airborne Studies in the Tropics (CAST)

Neil Harris ,J A Pyle,J R Dorsey,A R Mackenzie,G J Nott,C J Percival,G Vaughan,A D Robinson,R L Jones,Alastair C Lewis ,Richard W Hyde ,James Lee ,Hugo Ricketts ,Bin Ouyang ,Paul H Kaye ,Chris Stopford ,Paul I Palmer ,Andy Vick ,Michael Le Breton ,Martin Gallagher ,Matthew J Ashfold ,Jamie K Minaeian ,Stephen Andrews ,Hartmut Boesch ,Richard Newton ,Adam Vaughan ,Johannes Flemming ,Charles Chemel ,Axel Wellpott ,Lucy J Carpenter ,Plamen Angelov ,Elena Meneguz ,Neil Humpage ,Robyn Butler ,Stéphane Bauguitte ,Michal Filus ,Alistair J Manning

doi:10.1175/bams-d-14-00290.1

Abstract

Abstract The main field activities of the Coordinated Airborne Studies in the Tropics (CAST) campaign took place in the west Pacific during January–February 2014. The field campaign was based in Guam (13.5°N, 144.8°E), using the U.K. Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 atmospheric research aircraft, and was coordinated with the Airborne Tropical Tropopause Experiment (ATTREX) project with an unmanned Global Hawk and the Convective Transport of Active Species in the Tropics (CONTRAST) campaign with a Gulfstream V aircraft. Together, the three aircraft were able to make detailed measurements of atmospheric structure and composition from the ocean surface to 20 km. These measurements are providing new information about the processes influencing halogen and ozone levels in the tropical west Pacific, as well as the importance of trace-gas transport in convection for the upper troposphere and stratosphere. The FAAM aircraft made a total of 25 flights in the region between 1°S and 14°N and 130° and 155°E. It was used to sample at altitudes below 8 km, with much of the time spent in the marine boundary layer. It measured a range of chemical species and sampled extensively within the region of main inflow into the strong west Pacific convection. The CAST team also made ground-based measurements of a number of species (including daily ozonesondes) at the Atmospheric Radiation Measurement Program site on Manus Island, Papua New Guinea (2.1°S, 147.4°E). This article presents an overview of the CAST project, focusing on the design and operation of the west Pacific experiment. It additionally discusses some new developments in CAST, including flights of new instruments on board the Global Hawk in February–March 2015.

Highlights

The Tropical Tropopause Layer (TTL) is the region of the tropical atmosphere between the main convective outflow at ~12-13 km and the base of the stratosphere at 17-18 km and is a very important region for composition-aerosol-climate interactions (Randel and Jensen, 2013)
The majority of this paper describes the CAST measurements in January/February 2014, and the flight planning tools used for the FAAM aircraft and for linking its measurements with those made by the other aircraft
Twelve day backward trajectories were calculated using a mixture of Met Office analyses and forecasts, so that information was available about the possible influence of lower tropospheric air in the regions which could be sampled by the Global Hawk and the GV

Summary

Introduction

The Tropical Tropopause Layer (TTL) is the region of the tropical atmosphere between the main convective outflow at ~12-13 km and the base of the stratosphere at 17-18 km and is a very important region for composition-aerosol-climate interactions (Randel and Jensen, 2013). Large part of the flight planning for the FAAM research aircraft was to ensure a good coverage of the lower troposphere within range from Guam. Twelve day backward trajectories were calculated using a mixture of Met Office analyses and forecasts, so that information was available about the possible influence of lower tropospheric air in the regions which could be sampled by the Global Hawk and the GV.

Results

Conclusion