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dc.contributor.authorJaen, Juliana
dc.contributor.authorRenkwitz, Toralf
dc.contributor.authorChau, Jorge L.
dc.contributor.authorHe, Maosheng
dc.contributor.authorHoffmann, Peter
dc.contributor.authorYamazaki, Yosuke
dc.contributor.authorJacobi, Christoph
dc.contributor.authorTsutsumi, Masaki
dc.contributor.authorMatthias, Vivien
dc.contributor.authorHall, Chris
dc.date.accessioned2022-09-05T07:27:24Z
dc.date.available2022-09-05T07:27:24Z
dc.date.issued2022-01-20
dc.description.abstractSpecular meteor radars (SMRs) and partial reflection radars (PRRs) have been observing mesospheric winds for more than a solar cycle over Germany (∼ 54◦ N) and northern Norway (∼ 69◦ N). 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 (MLTSL) 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 vortex. At high latitudes, the year 2004 has a longer summer length compared to the mean value for MLT-SL as well as 2012 for both definitions. The M-SL exhibits an increasing trend over the years, while MLT-SL does not have a well-defined trend. We explore a possible influence of solar activity as well as large-scale atmospheric influences (e.g., quasi-biennial oscillation (QBO), El Niño–Southern Oscillation (ENSO), major sudden stratospheric warming events). We complement our work with an extended time series of 31 years at middle latitudes using only PRR winds. In this case, the summer length shows a breakpoint, suggesting a non-uniform trend, and periods similar to those known for ENSO and QBO.en_US
dc.identifier.citationJaen, Renkwitz, Chau, He, Hoffmann, Yamazaki, Jacobi, Tsutsumi, Matthias, Hall. 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. Annales Geophysicae. 2022;40(1):23-35en_US
dc.identifier.cristinIDFRIDAID 2023848
dc.identifier.doi10.5194/angeo-40-23-2022
dc.identifier.issn0992-7689
dc.identifier.issn1432-0576
dc.identifier.urihttps://hdl.handle.net/10037/26608
dc.language.isoengen_US
dc.publisherCopernicus Publicationsen_US
dc.relation.journalAnnales Geophysicae
dc.rights.accessRightsopenAccessen_US
dc.rights.holderCopyright 2022 The Author(s)en_US
dc.titleLong-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 Hemisphereen_US
dc.type.versionpublishedVersionen_US
dc.typeJournal articleen_US
dc.typeTidsskriftartikkelen_US
dc.typePeer revieweden_US


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