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Hi all, Now that winter is approaching, the stratospheric polar vortex is starting to take shape again. This also marks the time when the interest in stratospheric meteorology starts to increase again, due to its coupling with the weather in the troposphere etc. While looking at the stratospheric charts of the ECMWF from the Freie Universitat Berlin (or FU berlin in short), I came across a chart (heat flux charts) which I was so far unable to interpret. The type chart is given below: Heat flux wave 1 forecast of ECMWF, 12 UTC November 8 run, T+240. The chart is coincident with Wave 1 activity, which is expected to be present at the top of the stratosphere at around 70 N (zonal average). http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwfzm_ha1_f240.gif From what I could guess so far, I would say that the chart shows the covariance of horizontal, meridional wind with temperature. Assuming that the meridional wind is postive toward the pole, my guess would be that positive (orange) colours indicate transport of positive temperature anomalies toward the pole (in other words: a positive heat flux from lower to higher latitudes). This would in turn bring warm air from the midlatitudes toward the pole (in the chart above). Below is a representation of how this would look like at 1 hPa pressure level at the same timeframe: Geopotentials 1 hPa level, ECMWF, 12 UTC November 8 run, T+240. The black circle shows the line of 70 N around the pole. The arrows indicate temperature fluxes (if done properly). A possible interpretation would be that the heat flux in the first chart indicate a flux of warm air entering the vortex from one side (since it is only prevalent in 1 wave). This would then be from the Eurasian side (the arrow with a box around it), since the temperature gradient would be the most sharp at that area. My question is: is the way of reading the charts given above correct? Does the heat flux chart presented in the first image indeed represent the transport of heat poleward and vice versa? And is the way of application to the final chart also correct? Many thanks in advance for taking the time to answer these rather technical questions! Regards, Vorticity. *Edited to change thread tag.