Long-term studies of mesosphere and lower-thermosphere summer length definitions based on mean zonal wind features observed for more than one solar cycle at middle and high latitudes in the Northern Hemisphere ...

• Main Authors: Jaen, Juliana, Renkwitz, Toralf, Chau, Jorge L., He, Maosheng, Hoffmann, Peter, Yamazaki, Yosuke, Jacobi, Christoph, Tsutsumi, Masaki, Matthias, Vivien, Hall, Chris
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Katlenburg, Lindau : Copernicus 2022
• Subjects: Germany; atmospheric dynamics; El Nino-Southern Oscillation; mesosphere; seasonal variation; 550; Norway; Northern Norway
• Online Access: https://dx.doi.org/10.34657/10870; https://oa.tib.eu/renate/handle/123456789/11837

Specular meteor radars (SMRs) and partial reflection radars (PRRs) have been observing mesospheric winds for more than a solar cycle over Germany (g1/4g54g gN) and northern Norway (g1/4g69g gN). This work investigates the mesospheric mean zonal wind and the zonal mean geostrophic zonal wind from the Microwave Limb Sounder (MLS) over these two regions between 2004 and 2020. Our study focuses on the summer when strong planetary waves are absent and the stratospheric and tropospheric conditions are relatively stable. We establish two definitions of the summer length according to the zonal wind reversals: (1) the mesosphere and lower-thermosphere summer length (MLT-SL) using SMR and PRR winds and (2) the mesosphere summer length (M-SL) using the PRR and MLS. Under both definitions, the summer begins around April and ends around middle September. The largest year-to-year variability is found in the summer beginning in both definitions, particularly at high latitudes, possibly due to the influence of the polar ...