NTRODUCTION hances are the weather affects you every day It affects whether you wear shorts or a winter coat whether you can enjoy a picnic or ski trip and sometimes if you can even get to school You may try to insulate yourself from it with air conditioning and heaters but ultimately there is no escaping it Sometimes weather affects not just the quality of life but also life itself Flash floods lightning hurricanes and blizzards can all cause danger and even death Prolonged heat waves or cold snaps can also be fatal to people and the crops they rely on It's no wonder that since ancient times sailors farmers and others have been eager to understand the weather Weather is a snapshot of what the atmosphere the air that surrounds Earth is doing in a given place at a given time Look out the window Is it sunny Cloudy Snowing That s weather It is short term as opposed to the long term atmospheric conditions known as climate To understand what weather is imagine the atmosphere as a vast invisible ocean full of currents and swirling eddies These constant movements of air create the weather The most important factor driving atmospheric movements is radiation from the Sun The Sun heats the atmosphere unevenly A IIIIIIIIIIIIII
INTRODUCTION A satellite image taken on Sept 2 2008 shows storm systems left to right Gustav Hanna Ike and Josephine Getty Images Pet S
INVESTIGATING EARTH's WEATHER giving rise to warm and cold air masses with characteristic levels of temperature and moisture As the air masses move they influ ence the weather of the places they pass over Maritime tropical air masses for example form over tropical waters and typically pro duce heavy rain when they move over land At weather fronts the boundaries between air masses the air is unstable and storms are common Severe thunderstorms ice storms and tornadoes all typically form where air masses meet Sometimes the storms are violent In the flat plains of the Midwest for instance there are no mountain ranges to keep air masses from clashing and in spring and summer these collisions often spawn severe thunderstorms and sometimes dan gerous tornadoes In fact this region is often called Tornado Alley In this volume you will learn how these powerful storms develop You will also learn how the science of weather prediction has changed over the years The earliest forecasts were based only on careful observation The invention of the thermometer and the barometer in the 17th century provided the first accurate measure ments of temperature and air pressure Today scientists have much more sophisticated
INTRODUCTION tools for detecting and forecasting weather patterns Doppler radar for instance can measure wind speeds by observing micro waves reflected off raindrops And satellites circle Earth gathering images that are fed into powerful computers and turned into maps Such information is shared by the 180 member nations of the World Meteorological Organization And yet as much as weather forecasting has improved in recent years it is still diffi cult to predict daily weather accurately more than about a week in advance The unpre dictability and power of this awesome force of nature shows why weather continues to be as fascinating to modern people as it was to the sailors and farmers of ancient
