Geography

The hydrologic cycle, or water cycle, moves water from land and ocean to the atmosphere. Water from the oceans and land surfaces evaporates, changing state from liquid to vapor and entering the atmosphere. Total evaporation is about six times greater over oceans than land because oceans cover most of the …

Blistering summer heat waves can be deadly, with the elderly and the ill at greatest risk. However, in such weather, even healthy young people need to be careful, especially when it is both hot and humid. High humidity slows the evaporation of perspiration from our bodies, reducing its cooling effect. …

Surface type (urban or rural), elevation, latitude, daily and annual insolation cycles, and location (maritime or continental) all can influence air temperatures. Now let’s put all these factors together and see how they affect world air temperature patterns. First, we need a quick explanation of air temperature maps. Figure shows …

Images of the Earth from space show that about half of our planet is blanketed in clouds. Clouds play a complicated role in temperature—both cooling and warming the Earth and atmosphere. In this chapter, we will look at one of the most familiar roles of clouds: producing precipitation. Clouds are …

In general, the air is cooler at higher altitudes. Most incoming solar radiation passes through the atmosphere and is absorbed by the Earth’s surface. The atmosphere is then warmed at the surface by latent and sensible heat flows. So it makes sense that, in general, air farther from the Earth’s …

On a hot day, rural environments will feel cooler than urban environments. In rural areas, water is taken up by plant roots; it then moves to the leaves and evaporates from leaf pores in a process called transpiration. This process cools leaf surfaces, which in turn cool nearby air. Evaporation …

This chapter focuses on air temperature —that is, the temperature of the air as observed at 1.2 m (4 ft) above the ground surface. Air temperature conditions many aspects of human life, from the clothing we wear to the fuel costs we pay. Air tem-perature and air tempera-ture cycles also …

Global Time There’s an old Canadian joke that goes, “Repent! The world will end at midnight!—or, 12:30 a.m. in Newfoundland.” It’s humorous because independent-minded Newfoundlanders use a time zone that is a half hour ahead of the other Canadian maritime provinces. It highlights the fact that one single instant across …

The Geographic Grid  It is impossible to lay a flat sheet of paper over a sphere without creasing, folding, or cutting it—as you know if you have tried to gift-wrap a ball. This simple fact has caused mapmakers problems for centuries. Because the Earth’s surface is curved, we cannot divide …

The Shape of the Earth  As we all learn early in school, the Earth’s shape is very close to a sphere. Pictures taken from space by astronauts and by orbiting satellites also show us that the Earth is a ball rotating in space.   Today it seems almost nonsensical that …