The nature of mesopause jumps as simulated with the nudged KMCM model

Mesopause jumps are a phenomenon that is only observed in the southern summer MLT region. The mesopause is lifted by several kilometers within a few days and then later returns to its original altitude accompanied by strong cooling. Lidar and radar measurements indicate that these jumps are the result of a late breakdown of the polar jet, which occurs frequently in the southern hemisphere. Although the basic mechanism is known, no successful simulations of such mesopause jumps have yet been performed.

In my talk, I will present a case study using the Kühlungsborn Mechanistic general Circulation Model (KMCM) in which nudging is applied. I will compare measurements of the austral summers 2010/11, 2011/12 and 2012/13 obtained with lidars and radars over the Davis station in Antarctica at 69°S with simulations performed with the KMCM. Mesopause jumps were detected in the first two summers, while no jump occurred in the last summer.

In general, our simulations show that the KMCM with nudging is able to reproduce mesopause jumps. In November and December, the simulations agree quite well with the observations, and we can better understand the role of gravity waves in the mechanism of mesopause jumps. In January and February, however, the simulations seem to be too active, as the agreement with the observations is less good.