Friday, November 18, 2011

Kelvin vs. Madden and Julian

An active day here in Addu. In the previous post I showed what the radars looked like in the morning. Here's what they look like at 430pm local time:
(note much of the difference on the left sides of the images are due to blockage of the SMART-R beam by trees and the cab of the truck on which it's mounted).
It seems that we've lost our connection to the Meteosat satellite this afternoon, but here's the latest image we have, at 730 UTC (1230 pm local time):
What's the source of all this action? It doesn't seem to be the MJO arriving in the Indian ocean, yet. Here's a Hovmoeller plot of low-level zonal (east-west) wind, averaged 15S-15N (thanks Matt Wheeler). It shows that by this metric - an average over a very broad, 30 degree wide band centered on the equator - the MJO westerlies are still in the east Pacific, while here in the Indian ocean we are in easterlies associated with the continuing suppressed phase.
However, we do have westerlies over a narrow latitude belt just south of the equator, over all longitudes from Africa to Addu atoll. Here's a map of low-level wind and relative humidity, taken from a very short-term forecast made by a model run in France. Look at the arrows pointing to the right at around 5S on the left half of the image. Maybe these westerlies are associated with an atmospheric Kelvin wave...? My choice to show the French model rather than one of the others is in honor of the French crew who have just arrived here on Gan, ahead of their aircraft, the Falcon. It will be flying out of here to study cloud physics, doing what we call "ground validation" for the Megha-Tropiques satellite mission, which launched successfully a few months ago.


  1. Hey Adam,

    I think you're right about the Kelvin wave. You can see it pretty well here on Carl Schreck's webpage:

    See the green contours impinging onto the DYNAMO domain (shown by the vertical dashed lines).

  2. Michelle, yes it was Matt Wheeler who pointed this out to me earlier today (I should have said in the post).