Meteorology

I

Introduction

Meteorology, study of the earth’s atmosphere and especially the study of weather. A meteorologist is a person who studies the atmosphere. Meteorology is divided into a number of specialized sciences. Physical meteorology deals with the physical aspects of the atmosphere, such as the formation of clouds, rain, thunderstorms, and lightning. Physical meteorology also includes the study of visual events such as mirages, rainbows, and halos. The study of the winds and the laws that govern atmospheric motion is called dynamic meteorology. Synoptic meteorology is the study and analysis of large weather systems that exist for more than one day. Weather forecasting is part of synoptic meteorology. Agricultural meteorology deals with weather and its relationship to crops and vegetation. The study of atmospheric conditions over an area smaller than 1 sq km (0.4 sq mi) is called micrometeorology. Climate describes the average weather of a region. Climatology, a division of meteorology, is the study of a region’s average daily and seasonal weather events over a long period.

II

Physical Characteristics of Air

In order to study, describe, and understand the events that occur within the atmosphere, meteorologists measure the physical characteristics of the air within which these events take place. Meteorologists describe the air primarily in terms of its composition, temperature, pressure, wind speed, wind direction, precipitation, and humidity.

A

Air Composition

The earth’s atmosphere is a mixture of gases, mainly nitrogen (N₂) and oxygen (O₂), that are held to the earth by gravity. Near the earth’s surface, air is composed of about 78 percent nitrogen and about 21 percent oxygen. Small amounts of other gases, such as carbon dioxide (CO₂), argon (Ar), methane (CH₄), nitrous oxide (N₂O), and water vapor (H₂O), are also present. The concentration of the invisible water vapor varies from place to place and from time to time. Near the ground in warm tropical locations, the concentration of water vapor may reach 4 percent, while in polar areas its concentrations may be only a small fraction of a percent. Clouds are comprised of billions of small droplets of condensed water or tiny ice crystals.

B

Air Temperature

Air molecules are in constant motion. The speed of air molecules corresponds to their kinetic energy, which in turn corresponds to the amount of heat energy in the air. Air temperature is a measure of the average speed at which air molecules are moving; high speeds correspond to higher temperatures. The temperature of a substance is measured by a thermometer.

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