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Title: Photochemistry on the bottom side of the mesospheric Na layer

Abstract. Lidar observations of the mesospheric Na layer have revealed considerablediurnal variations, particularly on the bottom side of the layer, where morethan an order-of-magnitude increase in Na density has been observed below 80 kmafter sunrise. In this paper, multi-year Na lidar observations areutilized over a full diurnal cycle at Utah State University (USU) (41.8 N,111.8 W) and a global atmospheric model of Na with 0.5 kmvertical resolution in the mesosphere and lower thermosphere (WACCM-Na) to explorethe dramatic changes of Na density on the bottom side of the layer. Photolysis of the principal reservoir NaHCO3 is shown to beprimarily responsible for the increase in Na after sunrise, amplified by theincreased rate of reaction of NaHCO3 with atomic H, which is mainlyproduced from the photolysis of H2O and the reaction of OH withO3. This finding is further supported by Na lidar observation at USUduring the solar eclipse (>96 % totality) event on 21 August 2017, when a decrease and recovery of the Na density on thebottom side of the layer were observed. Lastly, the model simulation showsthat the Fe density below around 80 km increases more strongly and earlierthan observed Na changes during sunrise because of the considerably fasterphotolysis rate of its major reservoir of FeOH.

 
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Award ID(s):
1734333
NSF-PAR ID:
10109464
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
Atmospheric Chemistry and Physics
Volume:
19
Issue:
6
ISSN:
1680-7324
Page Range / eLocation ID:
3769 to 3777
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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