PhD studentship topic 1 Aerosol and chemical transport in deep convection Prof G. Vaughan and Prof. M. Gallagher The Tropical Tropopause Layer (TTL) is the region of the tropical atmosphere between 12 and 18 km altitude. Although remote and difficult to get to, this layer is key to the general circulation of the atmosphere: all the air in the stratosphere has to pass through the TTL, and clouds that form in the TTL have a large impact on the planet’s greenhouse effect. To learn more about the composition of the TTL, the School is engaged in a major international research project centred around NASA’s Global Hawk unmanned aircraft. We will be participating in the ATTREX field campaign in the western Pacific in 2014 using the FAAM aircraft and ozonesonde balloons in support of measurements in the TTL by the Global Hawk. Our focus will be on transport of air into the TTL by deep convection. Although deep convective storms occur in many regions of the tropics, their effect on the TTL is not the same everywhere. Experience during a previous campaign of ours in Darwin (Heyes et al, 2009) showed that transport from distant locations of deep convection dominated the composition of the upper TTL over northern Australia, despite widespread deep convection during the monsoon season there. We advanced the hypothesis that in particular source regions (which vary seasonally) there is effective coupling between the lower atmosphere and the TTL so that the composition of the lower atmosphere in these regions determines that of the TTL. One proposed source region is the West Pacific, but without detailed measurements in the region we cannot currently test this hypothesis. In this project the student will use measurements from islands in the West Pacific, together with Global Hawk and FAAM measurements, to test this hypothesis. Initially, the student will use existing measurements to develop the research methods and refine the research questions. They will then participate in the field campaign in winter 2013/14, preparing and launching the ozonesondes and helping to coordinate soundings with the aircraft flights and with other sounding stations. The project will address the following scientific problems: a) how well mixed is the atmosphere over the west Pacific warm pool? In monsoon conditions at Darwin, ozonesonde profiles showed uniform (well-mixed) profiles up to ~ 14 km. Do these extend higher at west Pacific sites? (b) The ozonesonde measurements will be accompanied by high-resolution radiosonde measurements, typically giving temperature and wind information every 10 m in the TTL. This information will provide important information on atmospheric waves. These waves are known to influence the clouds and humidity in the TTL but exactly how, we don’t know. c) By collaboration with the high- resolution modelling work being conducted at the University of Hertfordshire, the mixing processes and the effect of waves in the atmosphere will be investigated using the WRF model. This model is very flexible, particularly with regard to microphysics schemes with which Manchester has extensive experience. The aim of this work is will be to use the measured profiles to test the representation of mixing in the model, and to use the model to investigate the effect of the observed wave structures on humidity profiles in the TTL For further details contact geraint.vaughan@manchester.ac.uk References: W. J. Heyes, G. Vaughan, G. Allen, A. Volz-Thomas, H.-W. Pätz and R. Busen. Composition of the TTL over Darwin: local mixing or long-range transport? Atmos. Chem. Phys. 9, 7725–7736, 2009. P. T. May, J. H. Mather, G. Vaughan, C. Jakob, G. M. McFarquhar, K. N. Bower, and G. G. Mace. The Tropical Warm Pool International Cloud Experiment (TWPICE). Bull. Amer. Meteorol. Soc., 89, 632 - 645, 2008 G. Vaughan, C. Schiller, A. R. MacKenzie, K. Bower, T. Peter, H. Schlager, N. R. P. Harris and P. T. May. Studies in a natural laboratory: High-altitude aircraft measurements around deep tropical convection. Bull. Amer. Meteorol. Soc., 89, 647 – 662, 2008. View publication stats View publication stats