Interannual variability of the spring transition date in the MLT region observed with meteor radar at Obninsk (55°N, 37°E)

Vertical Structure of the Arctic Spring Transition in the Middle Atmosphere

“…On average, the zonal wind reverses between day 78 at 90 km and 83 at 80 km in the MLT in spring (see Figure 7a), which is in agreement with Merzlyakov et al. (2012). There is a slightly downward propagation of the wind reversal between 100 and 80 km within 5 days indicating that radiative as well as dynamical processes play a role.…”

“…Figure 7 shows the composites of the zonal wind in the MLT for the merged Esrange (68°N, 21°E) and Sodankylä (67°N, 26°E) data set for all available years (a) as well as for the different spring transition classes (b-f). On average, the zonal wind reverses between day 78 at 90 km and 83 at 80 km in the MLT in spring (see Figure 7a), which is in agreement with Merzlyakov et al (2012). There is a slightly downward propagation of the wind reversal between 100 and 80 km within 5 days indicating that radiative as well as dynamical processes play a role.…”

“…For the composite analysis of MLT winds, daily mean values of the background winds are used that were smoothed by a 15‐day running mean, similar to Merzlyakov et al. (2012) due to the high variability of this region.…”

“…The merged data set contains continuous wind data since August 1999 resulting in 21 spring transitions and thus, it is now the longest available continuous wind meteor radar observation on the globe. For the composite analysis of MLT winds, daily mean values of the background winds are used that were smoothed by a 15-day running mean, similar to Merzlyakov et al (2012) due to the high variability of this region.…”

“…(2010) investigated the zonal wind reversal in spring 2008 in the mesosphere and lower thermosphere (MLT) which was characterized by an abrupt transition to easterly winds at all heights (70–100 km) simultaneously. At 91 km the average wind reversal occurs at 24th March with a standard deviation of 9 days whereas the year‐to‐year variability of MLT zonal wind reversal correlates with stratospheric polar vortex variability (Aushev et al., 2006; Merzlyakov et al., 2012). Closely related to the wind reversal in the MLT in spring is an enhancement followed subsequently by a strong decrease in atomic oxygen and temperature (G. G. Shepherd et al., 1999; M. G. Shepherd et al., 2002).…”