IRFP: The Impact of the Double Tropopause on the Composition of the Upper Troposphere and Lower Stratosphere

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The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twelve-month research fellowship by Dr. Tanya R. Peevey to work with Dr. Paul Konopka at Forschungszentrum Jülich in Jülich, Germany.Multiple stable layers, usually called a double tropopause, are seen in the vertical structure of the Earth's atmosphere within the upper troposphere lower stratosphere (UTLS) region. The UTLS is a key region of the Earth's atmosphere since it contains various radiatively important species, e.g. water vapor, ozone and aerosols, which have been perturbed over time due to less long-wave radiation escaping from the Earth surface as other green house gases (GHGs) increase. The double tropopause forms most frequently in the mid-latitudes and has been associated with an exchange of air masses between the UT and LS. Air mass exchange events can change the local radiative balance by adjusting the local temperature profile and the static stability of the region, which in turn can change the structure of the atmosphere and result in a poleward shift the midlatitude storm tracks for example. Evaluating the impact of double tropopause related transport on the distribution and redistribution of radiatively important species in the UTLS region is important for understanding and predicting the Earth's radiation budget and, consequently, climate and climate change.This research project will study the UTLS region of the Earth's atmosphere using a unique combination of satellite observations from the High Resolution Dynamic Limb Sounder (HIRDLS), an instrument on the NASA Aura satellite, and model simulations from the Chemistry Lagrangian Model of the Stratosphere (CLaMS), developed at Forschungszentrum Jülich in Germany. The first objective of this project is to establish where air within the double tropopause originates since it could change the composition of the UTLS and thus Earth's radiative budget. The second objective is to understand the relationship between the double tropopause and tropopause inversion layer (TIL), a relationship recently put forth by other scientists using a dry-atmosphere model. That study found that the double tropopause could not form without the TIL being present. This connection is unexpected since these two atmospheric features have opposite spatial preferences and seasonal cycles, thus observations with high vertical resolution and a model specialized for the UTLS will be used to explore this relationship.Another benefit of this project, in addition to an increased understanding of the UTLS region and Earth's climate, includes the exchange of expertise between the PI and the host institution in Germany. Dr. Peevey will benefit greatly from the exchange by gaining knowledge of lagrangian models and skills in running model simulations.