This is a 5-year scientific collaboration to investigate vertical transport mechanisms in the upper mesosphere and lower thermosphere (MLT) using a combination of theory, observations, and atmospheric chemical models. The study focuses on the mesopause region, 80-105 km altitude, and employs Na and Fe wind/temperature lidar, meteor radar, and airglow data from two observation sites at Cerro Pachon, Chile, and Table Mountain, CO. The objectives are to quantify wave-induced vertical transport in the mesopause region above these sites, to characterize its effects on the fluxes and vertical distribution of heat, Na, Fe, O, and other key constituents, and to compare the measurements to the eddy diffusion parameterization schemes that are traditionally used to account for vertical transport in atmospheric chemistry models. Specific scientific goals include: 1) To characterize the vertical fluxes of heat, Na (at Cerro Pachon) and Fe (at Table Mountain) throughout the mesopause region and throughout the year, 2) To determine the effective vertical constituent transport velocities associated with advection, turbulent mixing, dynamical transport and Na/Fe chemistry and to characterize their seasonal variations, 3) To quantify the influence of wave-induced transport on the structure and seasonal variations of the mesospheric Na and Fe layers by comparing model predictions with observations, 4) To characterize the effective vertical transport associated with OH Meinel Band, O(1S) green line and O2 Atmospheric Band airglow emissions throughout the year at Cerro Pachon, and 5) Through model calculations to assess the influence of wave-induced transport on the structure and variations of other important mesospheric constituents such as atomic O.
Intellectual Merit: Knowledge of the magnitude and variability of wave-induced vertical transport is important to a wide range of research problems, including general circulation modeling, atmospheric chemistry modeling, thermal balance calculations, and the study of the mesospheric airglow and metal layers. This work will contribute to a much deeper understanding of the key gravity wave transport processes and their relationships to atmospheric chemistry. In addition, this work will significantly enhance our ability to model the constituent structure of the MLT, particularly the meteoric metal and airglow layers.
Broader Impacts: The research has broader implications for atmospheric science because the results can be used to characterize the impact of wave-induced transport on other important constituents in other atmospheric regions, such as stratospheric ozone, which in turn affects the thermal balance of the Earth's atmosphere. Hence, the results of this project may have important applications in global climate modeling. Furthermore, the direct measurements of the vertical fluxes of mesospheric Fe and Na, in combination with modeling, will substantially improve current estimates of the absolute value of the global meteoric input flux, which are highly uncertain. This is important because the meteoric debris that enters the MLT is eventually transported into the lower atmosphere, where it affects the formation of stratospheric aerosols and is ultimately deposited in the oceans, where it contributes to the concentration of key chemical species, such as Fe. Both stratospheric aerosols and oceanic Fe play important roles in Earth's climate. Stratospheric aerosols reflect sunlight, which alters the Earth's radiation budget, while oceanic Fe promotes the growth of phytoplankton, which affects the global carbon cycles, in particular atmospheric CO2.