Contribution of the Atmospheric Dynamics to the Sporadic Sodium Layer Formation

We report on a sporadic sodium layer (SSL) event observed by our Na fluorescence lidar at Wuhan, China (31°N, 114°E) on March 16, 1999, and we reveal some special behaviour. From careful analysis of various sodium content variations of the layer during the development of this SSL event, it is found that besides the sodium injection mechanism as expected, another mechanism we called the atmospheric dynamics also made a noticeable contribution to this SSL formation. Computer simulations conformed that under the combined action of a suitable sodium injection and a bi-direction vertical wind field, an SSL profile can be reproduced with a pronounced SSL
peak on normal sodium layer as we observed in this event. From these results, it is emphasized that atmospheric dynamics is important for the SSL formation.