The Köppen
Climate Classification System
Have you ever wondered why one area of the world is a desert, another a grassland, and another a rainforest? Why are there different forests and deserts, and why are there different types of life in each area? The answer is climate.
Climate is the characteristic condition of the atmosphere near the earth's surface at a certain place on earth. It is the long-term weather of that area (at least 30 years). This includes the region's general pattern of weather conditions, seasons and weather extremes like hurricanes, droughts, or rainy periods. Two of the most important factors determining an area's climate are air temperature and precipitation.
World biomes are controlled by climate. The climate of a region will determine what plants will grow there, and what animals will inhabit it. All three components, climate, plants and animals are interwoven to create the fabric of a biome.
Four Basic Climate Zones & Ten Sub-climate zones
Wet-Dry Tropical Climates (Aw)
Some facts about climate
The sun's rays hit the equator at a direct angle between 23 ° N and 23 ° S latitude. Radiation that reaches the atmosphere here is at its most intense.
In all other cases, the rays arrive at an angle to the surface and are less intense. The closer a place is to the poles, the smaller the angle and therefore the less intense the radiation.
Our climate system is based on the location of these hot and cold air-mass regions and the atmospheric circulation created by trade winds and westerlies.
Trade winds north of the equator blow from the northeast. South of the equator, they blow from the southeast. The trade winds of the two hemispheres meet near the equator, causing the air to rise. As the rising air cools, clouds and rain develop. The resulting bands of cloudy and rainy weather near the equator create tropical conditions.
Westerlies blow from the southwest on the Northern Hemisphere and from the northwest in the Southern Hemisphere. Westerlies steer storms from west to east across middle latitudes.
Both westerlies and trade winds blow away from the 30 ° latitude belt. Over large areas centered at 30 ° latitude, surface winds are light. Air slowly descends to replace the air that blows away. Any moisture the air contains evaporates in the intense heat. The tropical deserts, such as the Sahara of Africa and the Sonoran of Mexico, exist under these regions.
SeasonsThe Earth rotates about its axis, which is tilted at 23.5 degrees. This tilt and the sun's radiation result in the Earth's seasons. The sun emits rays that hit the earth's surface at different angles. These rays transmit the highest level of energy when they strike the earth at a right angle (90 °). Temperatures in these areas tend to be the hottest places on earth. Other locations, where the sun's rays hit at lesser angles, tend to be cooler.
As the Earth rotates on it's tilted axis around the sun, different parts of the Earth receive higher and lower levels of radiant energy. This creates the seasons.
A biome is a large geographical area of distinctive plant and animal groups, which are adapted to that particular environment. The climate and geography of a region determines what type of biome can exist in that region. Major biomes include deserts, forests, grasslands, tundra, and several types of aquatic environments. Each biome consists of many ecosystems whose communities have adapted to the small differences in climate and the environment inside the biome.
Köppen Climate Classification System
The Köppen Climate Classification System is the most widely used for classifying the world's climates. Most classification systems used today are based on the one introduced in 1900 by the Russian-German climatologist Wladimir Köppen. Köppen divided the Earth's surface into climatic regions that generally coincided with world patterns of vegetation and soils.
The Köppen system recognizes five major climate types based on the annual and monthly averages of temperature and precipitation. Each type is designated by a capital letter.
A - Moist Tropical Climates are known for their high temperatures year round and for their large amount of year round rain.
B - Dry Climates are characterized by little rain and a huge daily temperature range. Two subgroups, S - semiarid or steppe, and W - arid or desert, are used with the B climates.
C - In Humid Middle Latitude Climates land/water differences play a large part. These climates have warm,dry summers and cool, wet winters.
D - Continental Climates can be found in the interior regions of large land masses. Total precipitation is not very high and seasonal temperatures vary widely.
E - Cold Climates describe this climate type perfectly. These climates are part of areas where permanent ice and tundra are always present. Only about four months of the year have above freezing temperatures.
Further subgroups are designated by a second, lower case letter which distinguish specific seasonal characteristics of temperature and precipitation.
f - Moist with adequate precipitation in all months and no dry season. This letter usually accompanies the A, C, and D climates.
m - Rainforest climate in spite of short, dry season in monsoon type cycle. This letter only applies to A climates.
s - There is a dry season in the summer of the respective hemisphere (high-sun season).
w - There is a dry season in the winter of the respective hemisphere (low-sun season).
To further denote variations in climate, a third letter was added to the code.
a - Hot summers where the warmest month is over 22°C (72°F). These can be found in C and D climates.
b - Warm summer with the warmest month below 22°C (72°F). These can also be found in C and D climates.
c - Cool, short summers with less than four months over 10°C (50°F) in the C and D climates.
d - Very cold winters with the coldest month below -38°C (-36°F) in the D climate only.
h - Dry-hot with a mean annual temperature over 18°C (64°F) in B climates only.
k - Dry-cold with a mean annual temperature under 18°C (64°F) in B climates only.