The term “climate” refers to a particular area or region’s long-term weather patterns. Unlike weather, which can vary by the day or even hour, climates tend to remain stable in the short term; however, they can gradually shift over the centuries or millennia. Many factors make up a locale’s climate, but the two simplest factors used to identify climate are average temperature and precipitation.
Certain factors consistently influence the temperature of a particular location over time. Although latitude serves as a general predictor of average temperature -- that is, areas close to the equator tend to be hotter, while areas nearer the poles tend to be colder -- it is not the only influencer. For instance, temperature decreases with increasing elevation, at a rate of 6.5 degrees Celsius (12 degrees Fahrenheit) per kilometer (0.6 miles). This explains why a high peak like Tanzania’s Mount Kilimanjaro, which sits very close to the equator, experiences snow at its summit, while the plains below have a tropical climate. Other elements that factor into a climate’s average temperatures include proximity to large bodies of water, ocean currents, prevailing winds, humidity and amount of vegetation.
Climatologists classify a region’s climate not only by the amount of precipitation but also the type and frequency. Precipitation may fall as rain, snow, sleet or ice pellets. It may be evenly distributed throughout the year, as is the case in a tropical rainforest climate, or it may be significantly heavier during a “rainy season,” such as in parts of India, which experience a monsoon in the summer but dry conditions during winter. Factors influencing the precipitation an area receives are similar to those influencing temperature. They include wind patterns, latitude and proximity to mountains or large water bodies.
Displaying Data with Climographs
Scientists visually summarize a location’s climate using climographs, charts portraying temperature and precipitation, the most important elements of climate. A climograph displays average temperature and average precipitation each month of the year over a one-year period. Essentially, a line graph overlaid on a bar graph, temperature data is shown as a line connecting 12 points, while precipitation is shown by 12 bars.
Koppen Classification System
In the early 20th century, German climatologist Wladimir Köppen developed a system for classifying the world’s climates based on temperature and precipitation, and his system has remained in widespread use ever since. The six major climatic categories within the Koppen system are: tropical, subtropical, arid, temperate or continental, highland and polar. Each main category has various subtypes; for instance, the North American Great Plains fall under the “arid” category, as does the Sahara Desert, but the temperature and precipitation differences between them mean that the Great Plains are classified as having a “steppe” climate, while the Sahara is considered a “low-latitude desert.”
- McDougal-Littell: Exploring Earth -- What Is Climate?
- U.S. Environmental Protection Agency: Climate Change Indicators in the United States
- Rice University: The Atmosphere
- National Geographic Xpeditions: Climographs Key Vocabulary
- University of Texas: Koppen Climate Classification Flow Chart, Troy M. Kimmel
- Massachusetts Studies Project: Using Climographs
- National Geographic Education: Climographs-- Temperature, Precipitation, and the Human Condition
- National Geographic: Climate -- Average Conditions
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