PO Box 221876, Hollywood, FL 33022 (866) MCP-BOOK (toll-free) • www.masoncrest.com

Copyright © 2023 by Mason Crest, an imprint of National Highlights, Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, taping, or any information storage and retrieval system, without permission in writing from the publisher. Printed in the United States of America First printing 9 8 7 6 5 4 3 2 1 Series ISBN: 978-1-4222-4560-6 Hardcover ISBN: 978-1-4222-4565-1 ebook ISBN: 978-1-4222-7252-7 Cataloging-in-Publication Data on file with the Library of Congress Developed and Produced by National Highlights, Inc. Editor: Jacqueline Havelka - Inform Scientific Cover and Interior Design by Torque Advertising+Design Layout: Priceless Digital Media, LLC Publisher’s Note: Websites listed in this book were active at the time of publication. The publisher is not responsible for websites that have changed their address or discontinued operation since the date of publication. The publisher reviews and updates the websites each time the book is reprinted.

You may gain access to certain third-party content (“Third-Party Sites”) by scanning and using the QR Codes that appear in this publication (the “QR Codes”). We do not operate or control in any respect any information, products, or services on such Third-Party Sites linked to by us via the QR Codes included in this publication, and we assume no responsibility for any materials you may access using the QR Codes. Your use of the QR Codes may be subject to terms, limitations, or restrictions set forth in the applicable terms of use or otherwise established by the owners of the Third-Party Sites. Our linking to such Third-Party Sites via the QR Codes does not imply an endorsement or sponsorship of such Third-Party Sites or the information, products, or services offered on or through the Third-Party Sites, nor does it imply an endorsement or sponsorship of this publication by the owners of such Third-Party Sites.

K E Y I C O N S T O L O O K F O R : Words to Understand: These words with their easy-to-understand definitions will increase the reader’s understanding of the text while building vocabulary skills. Sidebars: This boxed material within the main text allows readers to build knowledge, gain insights, explore possibilities, and broaden their perspectives by weaving together additional information to provide realistic and holistic perspectives. Educational Videos: Readers can view videos by scanning our QR codes, providing them with additional educational content to supplement the text. Examples include news coverage, moments in history, speeches, iconic sports moments, and much more! Series Glossary of Key Terms. .........................................72 Further Reading and Internet Resources..........................74 Organizations to Contact................................................76 Index . ..........................................................................77 Author’s Biography and Photo Credits. ............................80 Text-Dependent Questions: These questions send the reader back to the text for more careful attention to the evidence presented there. Research Projects: Readers are pointed toward areas of further inquiry connected to each chapter. Suggestions are provided for projects that encourage deeper research and analysis. Series Glossary of Key Terms: This back-of-the-book glossary contains terminology used throughout this series. Words found here increase the reader’s ability to read and comprehend higher-level books and articles in this field. Chapter 1: The Fundamentals of Weather.......................... 7 Chapter 2: How Temperature Affects Weather...................23 Chapter 3: How Atmospheric Pressure Affects Weather. ....31 Chapter 4: How Clouds Affect Weather.............................49 Chapter 5: How Humidity and Precipitation Affect Weather...............................................61


atmosphere: the thin layer of air that surrounds planet Earth climate: the average weather in a particular region over a long period of time inverse relationship: a relationship between two variables whereby an increase in one causes a decrease in the other



Throughout history, people have both worshipped and feared the weather for its tremendous power. Weather has a role in culture, economies and even in how people interpret the concept of time. Weather is such an integral part of the daily routine that most people forget how truly powerful of a force weather actually is. People have an extremely close relationship with weather, although it is probably not something most think about each day. Chances are, you check the weather quite often. If you play sports, have an outdoor school activity, or are planning an outing with your family, you likely check the weather on TV or on your smartphone. What is the forecast? Will it rain? Will it snow? Will it be really hot? The weather determines quite a bit about how we live our lives. A rainy day may cause a change of plans from a sunny picnic to staying indoors to watch a movie. We often decide what we will do and what we will wear—all based on the weather. In fact, the weather can even influence how we feel, and extreme weather like a tornado or monsoon can change a person’s life forever.


The Earth experiences many temperature extremes. Depending on where you live, the weather determines how you live your daily life.

Lots of people check the daily forecast, and we are all affected by weather, but do we truly understand what weather really is? Weather actually refers to temporary atmospheric conditions surrounding the planet Earth. Weather is constantly changing—hour to hour, day to day, and year to year. Components of Weather Weather breaks down into six fundamental components that are all linked together: • temperature • atmospheric pressure • wind • humidity • precipitation • cloud cover


The New Weather: What is Weather?

Temperature: Temperature is a measure of the heat in the atmosphere . It can be hot or cold and is measured in Fahrenheit (the main system used in the United States) or Celsius (used by most other parts of the world and by scientists). Temperature is relative and ever changing. Weather is warmest near the earth’s equator and coldest at the North and South Poles. Atmospheric pressure: Atmospheric pressure refers to the weight that the earth’s atmosphere is exerting. When you tune into the weather forecasters on television, they often talk about high-pressure and low-pressure systems. High-pressure systems usually clear out the skies and bring cooler temperatures, while low pressure systems generally bring rainfall and warmer conditions. Atmospheric pressure is measured in units called “millibars of mercury.” At sea level, atmospheric pressure is standardized to one “atmosphere” or about 1,013 millibars of mercury. A low-pressure systemmeasures 995 millibars, while a high-pressure one measures about 1,030 millibars. Atmospheric pressure and altitude have an inverse relationship; at high altitudes, atmospheric pressure is much lower. For example, at the top of Mount Kilimanjaro, the atmospheric pressure is just 40 percent of the pressure at sea level. Mount Kilimanjaro is a dormant volcano in Tanzania and the highest mountain in Africa at 19,341 feet (5,895 meters) high. Wind: What is wind? Certainly, it is the movement of air, but how does wind form? When there are differences in temperature and atmospheric pressure, wind forms. Wind develops in areas of high atmospheric pressure and blows to areas of low pressure. The upper atmosphere contains strong winds called “jet streams,” bands of very strong air that encircle the earth several miles above. These strong, fast winds occur five to nine miles above the earth and can reach 275 miles per hour. Jet streams push weather systems around the earth. Humidity and precipitation: Humidity is a measure of the amount of water vapor in the air. What is water vapor? Water becomes vapor in the atmosphere. In its gaseous state, vapor helps


The Fundamentals of Weather

Wind is more than just air movement. Winds form when temperature differences occur. The upper atmosphere contains strong winds called jet streams.


The New Weather: What is Weather?

clouds, rain, and snow form. Weather forecasters use the term “relative humidity,” referring to the percentage of water that air can hold at any given temperature. At 100 percent, air is saturated and cannot hold any additional water vapor. Any excess water above 100 percent becomes rain. Warm air can hold more moisture than cold air, which is why places near the equator are much more humid. For example, Singapore experiences year-round humidity because the air is highly saturated with water from the nearby Indian Ocean. Cloud cover: There are several kinds of clouds, and not all produce rain. Cirrus clouds are wispy and usually indicate mild weather. Nimbostratus clouds produce steady rain, while cumulonimbus thunderhead clouds are known for producing heavy rains, thunderstorms, and even tornadoes. Clouds affect how much sunlight can reach earth. On very cloudy days, clouds prevent more of the sun’s radiation from reaching the earth, which explains why cloudy days are often cooler than clear, cloudless days. Cloud cover at night acts like a blanket to keep the earth’s surface warm. Weather and Climate Based on these six components, you can see that weather is ever changing and ever moving. Weather is a temporary condition in the atmosphere influenced by these six components. Weather is different in your part of the world from how it is in another part of the world at any given time, but weather where you are will eventually affect the weather thousands of miles away. For example, a hurricane that makes landfall in Florida can eventually bring heavy rain and wind to the entire east coast of the United States. Regions of the world tend to have the same weather over time. On the Texas Gulf Coast, summers are always hot and humid. In Siberia, winters are extremely cold and harsh. Over many years, certain regions of the world are characterized by certain conditions. The average weather in a particular region is called climate . What is your hometown like?


The Fundamentals of Weather

Cirrus clouds like this usually indicate mild weather conditions. When cirrus clouds are present, temperature and pressure is generally stable and there is little to no wind.

“Climate” refers to the average weather over time in a particular region. Weather can change hour to hour, but climate change may take hundreds or even thousands of years. For example, the Sahara Desert that we know today is a dry, sandy desert—the largest desert in the world—located in northern Africa. Thousands of years ago, the Sahara had frequent rain and was lush and green—very different from today. Both weather and climate can change. Weather changes rapidly, perhaps even from one day to the next, but climate change can take hundreds or even thousands of years to take effect.


The New Weather: What is Weather?

Why Weather Is Important Weather is important. In our daily lives, weather dictates what we will do—or not do—on any given day. However, it is important in ways that we might not readily think about. One way to think of weather is that it is ever changing to keep the earth in balance. Weather is the planet’s way of redistributing heat on its surface. The sun shines on the earth’s surface and creates heat on land and in the oceans. That heat causes the oceans’ surface waters to

Weather can change in an hour, but climate change takes hundreds or even thousands of years. Climates can vary widely depending on what part of the world you live in.


The Fundamentals of Weather


Weather has affected how humans have evolved. Scientists at the Smithsonian Institution say that key human adaptations have evolved because of environmental instability. Survival of the fittest includes the survival of those humans and other species who were most adaptable to the changing surroundings. Humans who migrated survived. Species that could not relocate to a more favorable habitat became extinct. Some scientists believe that upright walking or toolmaking might not have occurred if humans had not moved to drier habitats like grasslands. evaporate. The heat, and thus the evaporation, are greatest near the equator, so heat is carried in cloud water vapor and released during large hurricanes and thunderstorms. Therefore, weather also controls how rainwater is distributed across the earth. Some areas of the planet regularly flood, while others have major droughts that affect crops, animals, and humans. Weather has both negative and positive implications, but if we think about weather over many thousands of years, it has played a major role regarding where humans live. Weather has also greatly determined how various cultures have developed, and it has influenced how humans have migrated over the planet we call home. Weather greatly affects the daily lives of people around the world. Weather is a set of conditions on specific days at specific places. It can cause farmers to bring crops in early, or affect a school’s decision to stay open or closed due to icy weather. Weather affects lifestyles and cultures. The weather of a particular


The New Weather: What is Weather?

region determines how people stay warm or cool, and ultimately determines how people survive. Weather determines the types of clothing people wear and the types of transportation they use. Weather controls the land and the oceans. Bigger waves appear during storms, and more sand is carried away from beaches. Storm waters carry dirty runoff from streets into rivers, and this impacts the amount of bacteria in the ocean. The Weather-Food Connection Weather affects what we eat. It also determines the natural resources like water and trees in a particular area, as well as what crops and foods can be grown. Weather absolutely affects food production because weather impacts the health of humans, plants and animals. Weather limits the types of crops that can be grown in

Take this crash course to learn the difference between weather and climate.


The Fundamentals of Weather

Weather affects the crops that can be grown in certain areas of the world. Growing seasons are much longer in certain parts of the world, so more crops can be yielded.


The New Weather: What is Weather?

Made with FlippingBook Learn more on our blog