This project will measure the transport of reactive chemical species into the tropical Tropopause Transition Layer (TTL) over the Western Pacific warm pool region during boreal winter when tropospheric air masses in this region are preferentially transported into the lower stratosphere. The sources, chemical evolution, and transport of trace gases and their degradation products in this region can substantially impact the chemistry of the lower stratosphere but, to date, relatively few measurements have been made and, consequently, our understanding of and ability to predict the associated processes and feedbacks are uncertain. The extremely low ozone concentrations measured with ozonesondes are expected to result in very low levels of OH radicals and, thus, longer lifetimes for reactive gases whose primary sinks are oxidation pathways involving OH. The simultaneous occurrence of deep convection and prolonged lifetime of organic compounds in the TTL can significantly impact the stratospheric halogen budget. Because the chemical and radiative properties of this region are key factors in the mechanisms that link atmospheric composition and climate forcing, the CONTRAST experiment will provide measurements necessary to diagnose, constrain, and improve chemistry-climate models. A suite of gases, particles, and meteorological parameters will be measured in situ from the NSF GV aircraft and interpreted to elucidate the roles of active convection and long-range transport on the vertically resolved chemical composition of the tropical atmosphere particularly in the altitude region that dominates convective outflow (12-14 km). Moreover, CONTRAST will be scheduled and coordinated in collaboration with two other airborne studies planned for the same time and geographic location: The NASA EV1 project ATTREX (Airborne Tropical Tropopause Experiment) and the European CAST (Coordinated Airborne Studies in the Tropics). With complementary instrument payloads, coordinated flights of the GV, the NASA Global Hawk, and the UK Bae146 will provide an unprecedented examination of the full atmospheric column, from surface to >19 km, over the tropical western Pacific Ocean.
The unique suite of benchmark measurements under the auspices of CONTRAST will improve fundamental understanding of convective transport processes in the tropics and our ability to model the role of deep convection in chemistry-climate interactions. The project will train students in atmospheric chemistry who are directly involved in the deployment and subsequent data analysis and modeling activities. Broader education and outreach activities will be developed using web-based tools and media.
project was proposed to study the atmospheric chemistry of the atmosphere over the Western Pacific region during the winter season. During this season, strong convection mixes the atmosphere and transports reactive gases from their sources in the marine boundary layer to high altitudes near the tropical tropopause. In particular, halogen containing gases can have a significant impact on the chemistry of ozone in this altitude region and further into the lower stratosphere. To investigate the full range of altitudes necessary (0 - >18 km) the proposal requested the use of the NCAR GV aircraft, which could reach up to approximately 14.5 km. Collaboration was proposed with the NASA ATTREX mission, with similar chemical objectives to the CONTRAST mission, but with an aircraft that sampled altitudes >14.5 km, up to 19 km. More detailed exploration of the marine boundary layer, where reactive gas emissions originate, was established through a collaboration with a study (CAST) funded from the United Kingdom. Thus, a 3-aircraft mission was outlined to perform the study. The basic objectives of the proposed CONTRAST project were: Characterize the chemical composition at the level of convective outflow over the Western Pacific during the deep convective season Evaluate the budget of organic and inorganic bromine and iodine in the TTL Investigate transport pathways from the oceanic surface to the tropopause using the GV coordinated flights with BAe-146 and Global Hawk The work proposed here was to do more in-depth planning and coordination of the activity for a mission to be conducted from Guam during January/February, 2104. The in-depth planning included more detailed flight plans to address different aspects of the scientific questions, refinement of the instrument payload to make measurements from the GV, discussions of the computer and meteorological forecasting and modeling that would be required to conduct the mission and for post mission analysis, and logistics planning. The actual funding requests to conduct the scientific investigation were submitted to NSF as a result of the planning that was done during this phase of the project. The actual mission was successfully conducted during the planned time, and reports of the results and outcomes of the mission will be found in the reports of the individual CONTRAST investigators supported by NSF.
