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Latitude and climate

Introduction

Many factors influence the climate of a region. The most important factor is latitude because different latitudes receive different amounts of solar radiation.

Maximum land surface temperature Latitude

Courtesy of Jesse Allen and Robert Simmon/NASA, using MODIS data, Source earthobservatory.nasa. gov/IOTD/ view.php?id=77779

  • The Equator receives the most solar radiation. Days are equally long year-round and the Sun is just about directly overhead at midday.

  • The polar regions receive the least solar radiation. The night lasts six months during the winter. Even in summer, the Sun never rises very high in the sky. Sunlight filters through a thick wedge of atmosphere, making the sunlight much less intense. The high albedo, because of ice and snow, reflects a good portion of the Sun’s light.

It’s easy to see the difference in temperature at different latitudes in the Figure above.

But temperature is not completely correlated with latitude. There are many exceptions.

For example, notice that the western portion of South America has relatively low temperatures due to the Andes Mountains. The Rocky Mountains in the United States also have lower temperatures due to high altitudes. Western Europe is warmer than it should be due to the Gulf Stream.

Summary

  • The amount of solar radiation received by the planet is greatest at the Equator and lessens toward the poles.

  • At the poles the Sun never rises very high in the sky and sunlight filters through a thick wedge of atmosphere.

  • Latitude is not the only factor that determines the temperature of a region, as can be seen in the striped map above.

Review

* Why do the poles receive so much less solar radiation than the Equator considering that it’s light for six months at the poles?

* Why is latitude considered the most important factor in determining temperature?

* Look at a map of geological features and look at the temperature map to try to determine why some of the exceptions exist. What’s the relatively cool blob north of India?

This introduction from CK-12 Earth Science online textbook, on the FlexBook textbook authoring platform, CK-12 Earth Science online textbook

The midnight sun

This is a natural phenomenon that occurs in the local summer months, in places north of the Arctic Circle or south of the Antarctic Circle: in it, the sun remains visible at the local midnight.

Around the summer solstice (approximately 21 June in the north and 22 December in the south) the sun is visible for the full 24 hours, given fair weather.

The number of days per year with potential midnight sun increases the farther towards either pole one goes. Although approximately defined by the polar circles, in practice the midnight sun can be seen as much as 90 km outside the polar circle.

There are no permanent economically autonomous human settlements south of the Antarctic Circle, only research stations. Thus the countries whose populations experience it are limited to those crossed by the Arctic Circle: Canada (Yukon, Northwest Territories, and Nunavut), Greenland, Iceland, Finland, Norway, Russia, Sweden, and the United States (Alaska).

A quarter of Finland’s territory lies north of the Arctic Circle and at the country’s northernmost point the sun does not set at all for 60 days during summer. In Svalbard, Norway, the northernmost inhabited region of Europe, there is no sunset from approximately 19 April to 23 August.

The opposite phenomenon, polar night, occurs in winter when the sun stays below the horizon throughout the day.

  • “Midnight sun.” Wikipedia, The Free Encyclopedia.  1 Oct. 2015

Arctic summer Sun doesn't set gif

 

Learning Standards

tba

 

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