The Summer Mesopause Region at Davis, Antarctica 2010 – 2012

Abstract:

In cooperation with the Australian Antarctic Division mesopause temperatures, iron densities and NLC were measured at Davis, 69°S by the mobile Fe-Doppler-Lidar of the IAP. Within 2 years more than 2900 hours of observations have been obtained throughout the season.

We will present quasi-continuous measurements of temperature profiles in the southern hemisphere mesopause region during the transition from winter to summer in 2011/2012. In a period of 120 days around solstice we have performed lidar observations for a total of 736 hours. PMSE was simultaneously observed by the nearby Davis-MST Radar.

The winter/summer transition is identified by a downward shift of the mesopause which occurs on 8 November 2011. Soon after transition, mesopause heights and temperatures are similar to the northern hemisphere (NH) colatitude summer (88 km, 130 K). Around solstice the Mesopause is elevated for several days by 4–5 km and is colder than typical NH temperatures by 10 K. In this period individual profiles show temperatures as low as 100 K. The occurrence of polar mesosphere summer echoes is closely connected to low temperatures. Below 88 to 90 km and in the main summer season of 2011/2012 temperatures at Davis are generally warmer compared to the NH by 5–15 K, whereas temperatures are generally colder above 90 km.

The first NLC observed by the lidar occurred very late in the season close to solstice. Most NLC occurred during a period of comparable warm temperatures and high iron number densities in early January. The late occurrence is in agreement with long term observations by the Davis-Lidar (AAD). The late occurrence is a major difference compared to the co-latitude Andoya, 69° N.