The trade winds north of the equator blow from the northeast and the trade winds south of the equator from the southeast. When they meet at the equator, the air rises, and as it rises it cools, forming rain clouds. These rain clouds are the cause of the moist tropical weather – hot and wet – that occurs near to the equator. These places are home to the rainforest biomes.
Westerlies, on the other hand, blow from the southwest in the northern hemisphere, and from the northwest in the southern hemisphere. They move storms across from east to west on the equatorial latitudes.
Both winds blow away from the 30° latitude band. Over these areas, the winds are light. When the air descends, any moisture in it evaporates in the intense heat. That is what causes the hot and dry tropical climate in which the desert and grassland (plains) biomes are found.
The so-called mid-latitude climates are controlled mainly by two different air pockets, as it were. The tropical air that moves from the equator towards the poles, and the polar air moving from the poles towards the equator. Because the two atmospheres are vying for a place to produce their climate, a mid-range climate occurs, known as the dry mid-latitude climate. Within these climates, the main biome to be found is that of grassland.
Moving on, the Mediterranean climate, known for its warm, wet winters and hot, dry summers. The descending air of tropical climates causes very dry, hot spells in the summer, which can last for up to five months. As with the winds within and surrounding the 30° latitude band, as the air descends all the moisture evaporates, meaning that the air is dry, and not moist. However, when the air becomes too dry and static, major storms can occur, that ‘clear’ the air, meaning that the day after the storm, the air is cool and moist, and this is frequently when vegetation flourishes. Biomes found here are generally grasslands, and a biome known as the Chaparral biome. This biome is characterized by grassy plains, rocky mountain faces, small plants with tough, small leaves that retain moisture and animals such as coyotes, toads, alligators and snakes.
Next you have the moist continental climate. This is caused by, again, the fight between the two tropical and polar air fronts. However, because the regions (north Europe, for instance) are closer to the poles, the polar air dominates over the tropical air. This climate is mainly home to the deciduous forest biome.
Lastly, the so-called high-latitude climates. These are found in north Canada, in the Arctic Circle and in north Russia. Because of the polar winds, where the air rises from a very cold surface, and descends on a slightly warmer surface, with the tropical winds that have moisture in them, the summer is mild and dry, and the winters are long, hard and freezing cold. There is relatively little precipitation, and when it falls it falls in the form of ice (hail) or snow. This climate boasts the tundra biome. It is the world’s youngest biome, some 10,000 years old. The ground is permanently frozen, and plays host to plants like heather, gorse and birch trees. Polar bears roam the ice, as do wolves, reindeer and snowshoe rabbits.
Global warming is warming our planet, and in 20 years we could already see a difference in our biomes. If we are not careful, then we could completely tip the earth into an irreversible state of confusion, and it would kill most species that are well adapted to their current situations.
As you can see, there is a clear connection between the air above us, and the ground on which we live. Biome distribution is controlled by our climates, which in turn is controlled by the air that we breathe, and the winds. If there was to be a dramatic change in the way winds blew, or the rate they blew at, or how hot or cold they were, then we would undoubtedly see a significant change in the biomes that surround us.
