In an attempt to get to grips with this winters’ character, I started summarizing/analysing the NCEP/NCAR decadal means for the NH I have collected since September.
Out of SLP, 1000Mb temp ea. I chose the 500Mb samples, assuming they were most significant for the general pattern. With that, I transferred some features to CAD, scaling them to my Polar basic layer.
I marked the axes of the Rossby wave ridges and troughs. I turned the areas with positive and negative height anomaly into measurable polygons.
The result looks like this:
The dotted areas present positive height anomaly during 16 decades. Mind, I didn’t include areas without relevance for the Boreal/Arctic zone (+45dN).
This is the counterpart; negative height anomaly of the 500Mb pressure boundary.
What does this illustrate? I feel some embarrassment to think I just showed the total anomaly presented by NCEP/NCAR to be correct. A lot of work, just to find data reliable.
But, in the process, I’ve learned some interesting facts.
(1) There was never a negative anomaly over Greenland and Davis Strait.
(2) Negative anomalies occurred most often near Mongolia, the Bay of Biscay and over the Keewatin region (Canadese Nunavut)
(3) The ‘crack-site’ Beaufort Sea was usually on the leeward side of the positive anomaly; mean winds had a strong SE component, enhanced by the Keewatin negative anomalies
(4) It looks like the mean didn’t feature a classic pattern for a ‘Beaufort Gyre’ under cold lower tropospheric high pressure and a persistent vortex high up
(5) In line with (4), steering patterns were much more elongated (compared to a climatic vortex winter), catching up out of the Pacific and Atlantic with a strong anticyclonic tendency
(6) The Kara-Barentsz Seas, consequentially, endured a tendency for NE winds, cooling theregion
(7) Indeed, Greenland was the main pivot in the circulation
This ‘Medusa head’ represents the decadal position of the axes of 72 ridges and 91 troughs between 1 October and 10 March.
In the chaos, I marked three patterns that stand out. It looks like ridges stall preferredly over the Eastern Pacific as well as the Eastern Atlantic. Troughs had an exclusive card for the Hudson/Great Plains region, contributing to the Keewatin negative 500 Mb height anomaly. To lesser extent, that counted for the East Asian region too (cold Manchuria…).