What is the significance of seasonality with respect to the latitudinal radiation imbalance

As the season changes into winter, the net radiation becomes negative across much of the Northern Hemisphere and positive in the Southern Hemisphere. The pattern reverses on the March equinox. Averaged over the year, there is a net energy surplus at the equator and a net energy deficit at the poles. This equator-versus-pole energy imbalance is the fundamental driver of atmospheric and oceanic circulation.

EO Explorer. Snow Cover. Cloud Fraction. Show All Maps. Net Primary Productivity. Net Radiation. Sea Surface Temperature. Sea Surface Temperature Anomaly. Total Rainfall. Water Vapor. In winter, some polar latitudes receive no light at all black. Total energy received ranges from 0 during polar winter to about 50 during polar summer megajoules per square meter per day.

Even though illumination increases at the poles in the summer, bright white snow and sea ice reflect a significant portion of the incoming light, reducing the potential solar heating. The amount of sunlight the Earth absorbs depends on the reflectivness of the atmosphere and the ground surface.

This satellite map shows the amount of solar radiation watts per square meter reflected during September Along the equator, clouds reflected a large proportion of sunlight, while the pale sands of the Sahara caused the high reflectivness in North Africa. Neither pole is receiving much incoming sunlight at this time of year, so they reflect little energy even though both are ice-covered. The differences in reflectivness albedo and solar illumination at different latitudes lead to net heating imbalances throughout the Earth system.

At any place on Earth, the net heating is the difference between the amount of incoming sunlight and the amount heat radiated by the Earth back to space for more on this energy exchange see Page 4.

In the tropics there is a net energy surplus because the amount of sunlight absorbed is larger than the amount of heat radiated.

In the polar regions, however, there is an annual energy deficit because the amount of heat radiated to space is larger than the amount of absorbed sunlight. This map of net radiation incoming sunlight minus reflected light and outgoing heat shows global energy imbalances in September , the month of an equinox.

Areas around the equator absorbed about watts per square meter more on average orange and red than they reflected or radiated. Mid-latitudes were roughly in balance.