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[ Seminar ]
Seminar on Modeling and (Aircraft) Observations of the Tropical Tropopause Layer
Date February 6, 2018 2:00pm ~ (about 1 hour)
Room W601 in Research Institute for Applied Mechanics, Kyushu University (Kasuga, Fukuoka, Japan)
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Title Modeling and (Aircraft) Observations of the Tropical Tropopause Layer
Speaker Dr. Rei Ueyama (NASA Ames Research Center)
Abstract The Tropical Tropopause Layer (TTL), a transition layer in the upper troposphere and the lower stratosphere (~14-18 km) in the tropics, is the main gateway of various tropospheric trace gases and aerosols entering the stratosphere. While the conceptual model of the TTL and its properties are generally well established, detailed mechanisms involving the roles of deep convection, atmospheric waves and cloud microphysical processes remain an active area of research and target of airborne missions.

In this talk, I will first discuss the role of convection on lower stratospheric water vapor and upper tropospheric cirrus cloud occurrence based on an analysis of two sets of complementary transport and cloud microphysical models driven by ERA-Interim meteorological fields. Convective influence is diagnosed using geostationary satellite-derived convective cloud-top altitudes that are adjusted to match the CloudSat, CALIPSO, and CATS measurements. The model results are evaluated by comparison with satellite observations (e.g., Aura MLS, CALIPSO CALIOP).

I will then highlight some results from the NASA POSIDON (Pacific Oxidants, Sulfur, Ice, Dehydration, and cONvection) Experiment which took place in Guam in October 2016 using the NASA WB-57F high altitude research aircraft. The goals of the mission were to:

1. validate satellite observations of low O3 in the western tropical Pacific and evaluate the hypothesis of a corresponding OH minimum in the upper troposphere and its possible impact on very short-lived species and sulfur abundances;

2. investigate the transport and chemistry of sulfur species in the TTL over the convectively active western tropical Pacific;

3. assess the validity of global chemistry transport model projections of sulfur emissions on stratospheric sulfate aerosol; and

4. obtain in situ measurements of the microphysical properties and water content of anvil cirrus clouds detrained from deep convection as well as thin cirrus clouds near the tropopause that regulate the abundance of water vapor entering the stratosphere.

Climate Change Science Section, Center for Oceanic and Atmospheric Research