UNIT 4

Weather and Climate

What is always around us, affects all life on this planet, and has the ability to get you out of school? It’s the weather! Weather is the culmination of all phenomena happening in the atmosphere (thin layer of gases surrounding the earth’s surface) at a given time. This means that to measure weather, several factors must be looked at, all occurring at once. This is not to be confused with climate, which is a measure of the average atmospheric conditions during an extended period of time. Observing both weather and climate are crucial in understanding, predicting, and preparing for changes within our Earth’s cycles and systems.

TOPIC 4A : Watching Our Weather

Weather affects ecosystems as well as the everyday lives of humans. Human activities such as recreation, construction, travel and others are dependent upon weather conditions. For scientists to predict future weather events, they must analyze many factors that include temperature, wind, and precipitation.

Temperature is a measurement of heat. In meteorology, the study of weather, the temperature of the air is typically measured because changes in temperature often lead to air movement and storms. There are several scales for measuring temperature, including Fahrenheit and Celsius (the most universally used in everyday instances).

Wind is the flow of air. Air flows when it is heated by the sun and begins to rise (because warm air rises). Wind speed is often noted because it can be a factor in severe weather. Wind direction is of importance because it indicates the direction a weather system is coming from.

Visible, floating masses of water droplets or ice crystals in the atmosphere are known as clouds. There are several classifications of clouds that are grouped in two separate categories: layered (stratus clouds) and convective (cumulus clouds).

Precipitation occurs when water molecules are deposited onto the earth’s surface. There are a number of types of precipitation, including rain, snow, hail and fog. Rain occurs when water condenses into water droplets which then fall from the clouds. If the water vapor freezes instead of forming water droplets, it is called snow. When water droplets freeze within the cloud and are blown in a cycle through the upper and lower portion of that cloud, forming layers, hail is formed. Once hail is too heavy to be blown throughout the cloud any longer, it falls to the earth. Fog does not exist as an individual drop or crystal, but is instead simply a cloud that makes contact with the ground.

TOPIC 4B: Climate Clues

All living things on this planet are subject to the climatic conditions of their environment such as the extremes in temperature and the amount of rainfall. Over time, plants and animals have evolved adaptations specific to surviving in their habitat. During the cold winter months, many animals must escape the low temperatures by burrowing deep into the ground, hibernating, growing thicker coats, or even migrating to warmer locations. Plants have adapted other means to withstand cold temperatures. Deciduous trees lose their leaves and slow down their metabolism in order to go into dormancy during the winter. They use very little energy when the tree is making no new food, only surviving off of the energy they have already stored.

The climate of an area is determined by multiple factors, including the rotation of the Earth around the sun, the angle that sunlight hits the Earth’s surface, and the prevailing wind and water currents. The United States has predictable weather phenomena that help to shape its varied climates. The jet stream is a high altitude air current that flows from the west to the east and can dip lower into the South depending on global conditions. The gulf stream is a warm water surface current that flows from the tip of Florida along the eastern coastline and out into the Atlantic Ocean. A front is a boundary between two air masses of different densities, one being made of warm air and the other cold air. They are important to study because storms often arise from them. During the summer months, hurricanes can often arise that can cause extensive damage along the Atlantic and Gulf coasts. El Niño/La Niña is a weather phenomena that occurs within the Pacific Ocean bringing warm waters to the western coastline causing droughts in the Pacific Northwest and floods in the Southwest.