The atmosphere is inextricably linked with human endeavour. There are countless examples: the early loss of ships at sea in fierce storms; fortuitous Trade Winds that aided the crossing of vast oceans; devastating droughts, floods and hurricanes that still take thousands of lives even today; and the reliance on the regular onset of rainy seasons that sets the timing of agriculture – the weather has an enormous impact on us all. It has shaped cultures and is even responsible for key turning points in history, such as the failure of Napoleon’s march into Russia in the grip of winter in the nineteenth century or the mass displacement of farmers in America due to the Dust Bowl drought of the 1930s.
These events and their consequences come about because the atmosphere is constantly changing. It varies on all timescales from the afternoon sunshine that brings us outdoors to the prolonged rains of the tropical monsoons. There are even decades where the weather keeps reverting back to similar behaviour summer after summer or winter after winter, only to change and be followed by years of the opposite. This apparently mysterious behaviour arises because the atmosphere is actually a constantly circulating fluid; trapped in a thin layer at the surface of our rotating Earth it swirls and flows just like the water in your bath tub. Apart from a lack of internal friction, the equations that govern the future behaviour of our weather and climate are almost the same as the equations that apply to the swirling fluid in your morning cup of coffee.
There are just six mathematical equations that encapsulate all of this and they can be written so concisely that they fit onto the back of a postcard. In fact, given their enormous significance, it is surprising they are not printed on T-shirts! These few equations that determine the fate of our weather also stem from well-established, or even old physics: they derive from Newton’s laws of motion, the physics of heat and gases that was uncovered more than a century ago and the fact that air is neither created nor destroyed as it blows around with the wind. Yet despite the fact that we know so well the equations that govern what the future weather will be, they are still shrouded in uncertainty. This is because the problem is not like your school maths exercise where pencil and paper will do, instead the equations are intractable: they simply cannot be solved precisely. Even worse, they show that small changes can eventually give rise to big impacts through ‘chaos’ and the revelation that a seagull flapping its wings can actually result in a hurricane months later fundamentally puts limits on any forecast. This is what makes meteorology so challenging and yet so compelling, and understanding the fluid that is our atmosphere is one of the most active remaining areas of terrestrial physics.
Harnessing the power
of the wind, constantly circulating the planet, is one early example of how the human race propelled itself towards becoming a global society.
Modern advances in understanding and the production of improved forecasts from hours to years ahead are now completely dependent on modern technology. A suite of scientific instruments measures various parameters of the Earth’s atmosphere. Arrays of environmental satellites continuously monitor the behaviour of the atmosphere and oceans and relay their measurements back to Earth: polar orbiters constantly circle the Earth in an almost north-south orbit at 800 kilometres altitude and geostationary satellites are sited 36,000 kilometres above the surface.
These vital observations, along with terrestrial measurements from weather stations, radar, aircraft and weather balloons are automatically incorporated into vast databases that constantly update our changing picture of the global weather. Some of the most powerful computers on the planet are used to pick up this latest information, combine it with computerized representations of the underlying equations and calculate what will happen next. The results are remarkable: the computer models produce virtual simulations of the Earth’s global weather that contain just about everything we see, from jet streams and hurricanes to multi-year climate oscillations between the ocean and atmosphere like El Niño. All of these features emerge spontaneously from the few fundamental equations at the core of the computer models. The results of this daily application of basic science drive everything from the forecast made this evening by your local TV weather forecaster to the century-long projections that affect government policies on climate change.
This book takes you to the edge of our current knowledge. It is written by leading experts in weather forecasting, the physics of the atmosphere and the behaviour of global climate, who bring you their insights after more than 200 years of combined research experience. In the first section, The Elements, the groundwork is done to describe the basic features of our weather with detailed explanations of how many common meteorological phenomena that we all take for granted are actually produced. The Global Atmosphere follows, providing the big picture in which our weather sits, identifying everything from the jet streams that deliver storms across the ocean basins to the return flow in the tropical Trade Winds. The third section, The Sun, explains the science behind the ephemeral optical phenomena that light up our skies and the way our local star determines and profoundly influences the weather and climate on Earth. Weather Watching & Forecasting gives an insight into the machinery that is brought into action every day to make your weather forecast. Section four looks further ahead and asks the question Can We Change the Weather? using examples from historical changes in the ozone layer to future climate change. All of this is put in the context of natural weather fluctuations in Weather Cycles before the final section, Extreme Weather, explains the wilder side of meteorology.
You can open this book at any point or immerse yourself in a complete chapter at a time and also read the fascinating histories of some of the great pioneers in meteorology. However you approach the 50 topics, I urge you to speculate on what is to come. Before the advance of atmospheric science, weather forecasters were ridiculed for their dream of predicting the future, but the ever-increasing accuracy of weather forecasts today is a reality and this makes them an essential tool to society worldwide. Even long-range predictions of the average weather from months to years ahead are now possible and, in some cases, point towards dramatic future events. Some of these forecasts are destined to become ever more critical and they are unfolding right now, as you read this book, when the globe is warmer than ever recorded before.
Basic physics encapsulated
in a few fundamental equations contain the secrets of our future weather and climate, from winter cold snaps to summer heatwaves.
