CEDAR: Ground-Based Optical Imaging of Sporadic Sodium Clouds Near the Summer Mesopause, Using Resonantly Scattered Sunlight

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The investigators will develop a new method to obtain two-dimensional images of sporadic clouds of mesospheric sodium. These images will be constructed by combining data from a sodium lidar and an optical spectrometer obtained during arctic summer months. The project involves minor modifications to existing instruments at Poker Flat, Alaska, and the development of analysis and calibration software to perform the two-dimensional imaging with high reliability. The mesopause region hosts persistent layers of neutral and ionized metallic atoms that are replenished by the ablation of meteors. These metal layers can be used as tracers of the thermal, chemical, and dynamical conditions near the mesopause. Although the altitude distribution of these layers have been studied using various techniques, the horizontal structure of the layers remains unknown. This investigation aims to observe the two-dimensional structure of metallic layers using the sun to illuminate sodium atoms, and sensitive instrumentation to detect the scattered sunlight. The simultaneous lidar measurements will provide information about the altitude distribution of the layers. Various models have shown that the temperature structure in the mesopause may be a sensitive indicator of global change. Understanding the distribution of sporadic layers in the mesosphere is important in studying processes that heat and cool the middle atmosphere.