Written on November 14, 2010 at 2:55 pm by buildwindgenerator

what are the easterly winds that traditionally supplied wind power to sailing ships called?

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1. clark says:

   November 14, 2010 at 2:55 pm

   Trade winds…..
2. Oliver Shaw says:

   November 14, 2010 at 2:55 pm

   Primarily the trade winds, but for those very few (but important) ships navigating in polar waters they would be the polar easterlies.

   Westerlies??? …. you surely can’t be serious; you have just stated yourself that you are asking about easterlies, and westerlies are the exact opposite.

   The Hadley cell is a circulating system which is driven by upwards movement by convection in the tropics (as a result of heating the air), and downwards motion in about latitudes 30 degrees both north and south (the "Horse Latitudes" in the case of the northern hemisphere) as the air cools. Therefore the high altitude air between the two moves towards the poles, and as a result of the Coriolis Effect it is deflected to the right in the northern hemisphere (and to the left in the southern hemisphere), i.e. eastwards in both cases, thus creating the Jetstream. At sea level the air returns towards the Equator, and again is deflected to the right in the northern hemisphere (and to the left in the southern), thus giving rise to the Trade Winds.

   From the phrasing of the question this looks like a piece of school homework; please next time do your own homework rather than asking the online community to do it for you!! An internet search on "Hadley cell" should provide all this information, along with information about the polar cell and the Ferris cell, which give rise respectively to the polar easterlies and the prevailing westerlies.

   Note that the westerlies are very far from constant, merely prevailing, because the Ferris cell is a secondary one, driven only by the friction created by the upward motion of the polar cell in latitudes somewhere around 60 degrees (both north and south) and the downward motion of the Hadley cell in the Horse Latitudes. The air in the Ferris cell moves in the opposite direction from what convection would suggest if you were to consider this cell in isolation. The air moves as it does because we have opposing sets of forces, but the frictional forces are USUALLY stronger than the convective forces within the Ferris cell. Thus the Ferris cell is characterised by turbulence and instability, and this in turn can create undulations in the polar front and these can be the nuclei for the start of depressions, which are characterised by winds rotating around the centre (anticlockwise in the northern hemisphere), and usually by associated frontal systems. Likewise, localised regions of high pressure can arise, characterised by winds rotating clockwise in the northern hemisphere, and normally with no fronts (although I have known occasional exceptions).

   So winds in latitudes about 30 degrees to about 60 degrees (either north or south) CAN come from any direction, and at almost any strength from zero up to storm, but they are more often southwesterly than any other direction; this is what "prevailing" means in this context.

   Note also that westerlies in the southern hemisphere are much stronger and more stable than those in the north, because of the near absence of land at those latitudes in the southern hemisphere. The "roaring forties" are such because with the solitary exception of Cape Horn they meet no land at all as they blow around that band of latitude.
3. Richard C says:

   November 14, 2010 at 2:55 pm

   They are the trade winds…….which was a term used for favorable winds, but not only easterly……..