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Help understanding this model image

Discussion in 'News, Help & Support' started by tractor girl, Jan 22, 2018.

  1. tractor girl

    tractor girl Member

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    [​IMG]

    I've looked at this image for a bit and am having trouble with the concept. Can anyone help with what this graphic is depicting, or maybe give an "anatomy" of the graphic?
     
  2. Shawn

    Shawn Staff Member Administrator Moderator Site Developer

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    @Webberweather53 , please help with this one because I know others are also curious.
     
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  3. Shawn

    Shawn Staff Member Administrator Moderator Site Developer

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    I do know these waves have very big impacts on the weather into the continental usa; and eric uses them extensively.
     
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  4. Webberweather53

    Webberweather53 Meteorologist

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    Ok, essentially what this diagram is showing is a time-longitude plot of 200 hpa velocity potential anomalies. Time is on the y axis and longitude (in degrees east) is on the x axis. Hovmoller diagrams like this are useful for tracking wave propagation in real-time, with Rossby waves in the tropics moving from west to east (diagonally from top right to bottom left) on the diagram and phenomena such as Kelvin Waves and MJO events moving from east to west (diagonally from top left to bottom right.) Since you know the distance between each longitudinal point on the earth for a particular latitude, diagrams like these are also useful for monitoring the speed of these waves which can be useful in deciphering whether you're dealing with a faster moving convectively coupled kelvin wave or MJO wave for example. The variable plotted here is known as velocity potential, and its provided the upper troposphere (~200 hPa). Velocity potential essentially measures the irrotational (purely divergent) part of the flow which serves as a proxy for deep cumulonimbus towers in the tropics. If we measured divergence we wouldn't necessarily be measuring the same thing or purely upper level divergence from these areas of deep convection because some of the observed flow response associated w/ upper level divergence receives some contribution from the coriolis effect (even though the coriolis effect is small near the equator & in the tropics).
     
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  5. whamby

    whamby politicians discussing climate change Member

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    I still don't get it.
     
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