Near the equator there is a band of relatively low pressure -- the equatorial low. At both poles there is a cell of relatively high pressure -- polar highs.
At latitudes of about 30o, in both hemispheres, there are cells of high pressure -- subtropical highs. These cells tend to lie over oceans with the cellular character more pronounced in the northern hemisphere. Their position varies seasonally, roughly north to south, over a region that remains the same from year to year. Their location my vary more widely over longer periods.
Two subtropical highs are significant for North America. The Pacific High is centered in the Pacific Ocean at roughly longitude 135o moving between latitude 40o in summer to 30o in winter. The Bermuda High is centered in the Atlantic Ocean at roughly 30o latitude moving east-west from 20o longitude in winter to 40o in summer.
At latitudes of about 60o, in both hemispheres, there is a region of low pressure -- subpolar lows. In the northern hemisphere, this region is cellular with the cells lying over oceans; in the southern it is a band.
Two subpolar lows are significant for North America. In winter, the center the Iceland Low is situated between the southern coast of Greenland and Iceland; the Aleutian Low over the the Aleutian Islands. In summer, both are rather diffuse.
The subpolar lows are separated from the subtropical highs by the polar front. The subtropical highs from each hemisphere are separated by the intertropical convergence.
