Skip to main content

Section 9.2 Observed circulation patterns

NOAA Jetstream:

Global Circulation Model: Observation

  • tropical trade winds converging in Intertropical convergence zone (ICTZ) (region of the doldrums)

  • midlatitude westerlies encounter the polar easterlies along the polar front

Idealized zonal pressure belts:

  • The equatorial low is an intertropical convergence zone (ITCZ).

  • Subtropical highs (STH) are high-pressure zones in the belts about 20°–35° latitude on either side of the equator.

  • Polar highs near the Earth’s poles are where the polar easterlies originate.


  • seasonal reversal of winds; generally driven by pressure differences.

  • The Asian monsoon, which affects India and its surrounding areas, China, Korea, and Japan.

  • The North American monsoon occurs in the southwestern U.S. and northwestern Mexico: this monsoon is driven by the extreme temperatures, which generate a low-pressure center over Arizona and results in a circulation pattern that brings moist air from the Gulf of California and from the Gulf of Mexico, to a lesser degree.

Cloud and Precipitation patterns also show clear trends related to planetary circulation