UNIT 6—LESSON 2
Describe the climatic elements of
temperature, precipitation, and wind.
OUTLINE Temperature Precipitation Wind CLIMATIC ELEMENTS The weather elements that are used to describe
The weather elements that are used to describeclimate are also the elements that determine the type of climate for a region. This lesson presents a brief explanation of the importance of these elements. The climatic elements of temperature, precipitation, and wind are not the only parameters included in a climatology package; however, they are the most significant elements used to express the climate of a region.
Learning Objective: Describe the climaticelements of temperature, precipitation, and wind.
Temperature is undoubtedly the most im-portant climatic element. The temperature of an area is dependent upon latitude or the distribu-tion of incoming and outgoing radiation the nature of the surface (land or water); the altitude; and the prevailing winds. The air temperature normally used in climatology is that recorded at the surface. Moisture, or the lack of moisture, modifies temperature. The more moisture in a region, the smaller the temperature range, and the drier the region, the greater the temperature range. Moisture is also influenced by temperature. Warmer air can hold more moisture than can cooler air, resulting in increased evaporation and a higher probability of clouds and precipitation. Moisture, when coupled with condensation and evaporation, is an extremely important climatic element. It ultimately determines the type of climate for a specific region.
Precipitation is the second most importantclimatic element. In most studies, precipitation is defined as water reaching Earth’s surface by falling either in a liquid or a solid state. The most significant forms are rain and snow. Precipitation has a wide range of variability over the Earth’s surface. Because of this variability, a longer series of observations is generally required to establish a mean or an average. Two stations may have the same amount of annual precipitation, but it could occur in different months or on different days during these months, or the inten-sity could vary. Therefore, it often becomes necessary to include such factors as average number of days with precipitation and average amount per day. Precipitation is expressed in most studies in the United States in inches, but throughout the rest of the world, millimeters are normally used.
Since precipitation amounts are directlyassociated with amount and type of clouds, cloud cover must also be considered with precipitation. Cloud climatology also includes such phenomena as fog and thunderstorms.
Wind is the climatic element that trans- ports heat and moisture into a region. The climate of an area is often determined by the properties of temperature and moisture that are found upstream of that region. Climatologists are mostly interested in wind with regard to its direction, speed, and gustiness. Wind is therefore usually discussed in terms of prevailing direction, average speeds, and max-imum gusts. Some climatological studies use resultant wind, which is the vectorial average of all wind directions and speeds for a given level, at a specific place, and for a given period.