Jump to content
Problems logging in? ×
Snow?
Local
Radar
Cold?

lorenzo

Forum Team
  • Posts

    4,875
  • Joined

  • Last visited

  • Days Won

    25

Posts posted by lorenzo

  1. While on average the “downward impact” of SSWs is robust, not all SSWs appear to couple down to the surface. Most studies agree that about two thirds (Charlton-Perez et al., 2018; Domeisen, 2019; White et al., 2019) of SSW events are characterized as having a visible downward impact (e.g., persistent negative phase of the NAM or NAO in the lower troposphere and/or the lower stratosphere, (e.g., Domeisen, 2019; Karpechko et al., 2017). One factor affecting the appearance of downward impact is the tropospheric NAM index prior to and at the time of the SSW. If the NAM is already negative, there will be a vertical connection to the negative stratospheric NAM. On the other hand, if the tropospheric NAM is strongly positive prior to the SSW, the appearance of vertical coupling is less likely, at least initially. The same is true for the NAO: if a negative NAO is present at the time of the SSW, the downward coupling is instantaneous but short-lived, while otherwise the negative NAO often appears after the SSW event (Domeisen et al., 2020). The stratosphere is one of several factors influencing the NAM, with most NAM variability being generated within the troposphere (and from surface interactions). The stratospheric influence becomes clear, only statistically, in regressions or in composites of many SSWs. Specifically, the concept of surface amplification of the polar pressure signal (Figure 3) will not be apparent during every SSW, but it becomes clear when averaging over many events. This is because the troposphere is highly variable, and the stratosphere represents a modest influence that is active during the cold season.

    AGUPUBS.ONLINELIBRARY.WILEY.COM

     


    Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4983681
    • Like 1
×
×
  • Create New...