Skip to main content

Section 9.5 Seasonal variations

Global Circulation Model: Seasonal Variations

  • ITCZ, subtropical highs, and polar front all shift southward in NH winter and northward in NH summer

  • Polar jet stream is displaced further poleward in summer in both hemispheres

  • During summer the positions of the subtropical highs shift poleward

  • Lows associated with the ITCZ shift seasonally as do the lows associated with the polar front

  • Monsoon development (again): connected to seasonal variations in large-scale circulation patterns:

  • ITCZ effectively moves up into Asia, causing shift in the direction of the trade winds around India

Again, all of this is driven by changes in insolation. In general,

  • the Earth loses more energy (longwave) at the equator than at the poles,

  • but gains much more energy (shortwave) at the equator than at the poles

This situation creates an energy imbalance that requires a "poleward" transfer of heat. This heat is transferred by the ocean and the atmosphere.