The rising temperatures of today’s climate are being linked to extreme weather, droughts, floods and intense storms, and global food and water supplies are coming under severe stress. While the current changes are unprecedented in their rapidity, climate variations in the past have had devastating consequences. What can we learn from them? [TM252 or search for … Continue reading The Decline of the Mayans: a Warning Signal for Us
Tag: Geophysics
Earth’s Digital Twins can help us to avert Disaster
Imagine another Earth, just like ours, but running a year ahead. Observing it, we could foretell events over the coming weeks or months, and take action to avoid catastrophes. There is no such planet! Even if there were, conditions there would diverge rapidly from ours, so it would provide no guidance on our future. But … Continue reading Earth’s Digital Twins can help us to avert Disaster
Margules’ Tendency Equation and Richardson’s Forecast
During World War One, long before the invention of computers, the English Quaker mathematician Lewis Fry Richardson devised a method of solving the equations and made a test forecast by hand. The forecast was a complete failure: Richardson calculated that the pressure at a particular point would rise by 145 hPa in 6 hours. This … Continue reading Margules’ Tendency Equation and Richardson’s Forecast
Broken Symmetry and Atmospheric Waves, 2
Part II: Stationary Mountains and Travelling Waves Atmospheric flow over mountains can generate large-scale waves that propagate upwards. Although the mountains are stationary(!), the waves may have a component that propagates towards the west. In this post, we look at a simple model that explains this curious asymmetry. Earth's Rotation and Symmetry Breaking If the … Continue reading Broken Symmetry and Atmospheric Waves, 2
Broken Symmetry and Atmospheric Waves, 1
Part I: Vertically propagating Waves and the Stratospheric Window Symmetry is a powerful organising principle in physics. It is a central concept in both classical and quantum mechanics and has a key role in the standard model. When symmetry is violated, interesting things happen. The book Shattered Symmetry by Pieter Thyssen and Arnout Ceulemans discusses … Continue reading Broken Symmetry and Atmospheric Waves, 1
Weather Warnings in Glorious Technicolor
Severe weather affects us all and we need to know when to take action to protect ourselves and our property. We have become familiar with the colourful spectrum of warnings issued by Met Éireann. For several years, Met Éireann has issued warnings of extreme weather. These depend on the severity of the meteorological event and … Continue reading Weather Warnings in Glorious Technicolor
Dropping Pebbles down a Mine-shaft
If you drop a pebble down a mine-shaft, it will not fall vertically, but will be deflected slightly to the East by the Coriolis force, an effect of the Earth's rotation. We can solve the equations to calculate the amount of deflection; for a ten-second drop, the pebble falls about 500 metres (air resistance is … Continue reading Dropping Pebbles down a Mine-shaft
Buffon’s Noodle and the Mathematics of Hillwalking
In addition to some beautiful photos and maps and descriptions of upland challenges in Ireland and abroad, the November issue of The Summit, the Mountain Views Quarterly Newsletter for hikers and hillwalkers, describes a method to find the length of a walk based on ideas originating with the French naturalist and mathematician George-Louis Leclerc, Comte … Continue reading Buffon’s Noodle and the Mathematics of Hillwalking
Earth System Models simulate the changing climate
The climate is changing, and we need to know what changes to expect and how soon to expect them. Earth system models, which simulate all relevant components of the Earth system, are the primary means of anticipating future changes of our climate [TM219 or search for “thatsmaths” at irishtimes.com]. A Holistic View Over the past century, our … Continue reading Earth System Models simulate the changing climate
Changing Views on the Age of the Earth
In 1650, the Earth was 4654 years old. In 1864 it was 100 million years old. In 1897, the upper limit was revised to 40 million years. Currently, we believe the age to be about 4.5 billion years. What will be the best guess in the year 2050? [TM217 or search for “thatsmaths” at irishtimes.com]. Ussher's Chronology … Continue reading Changing Views on the Age of the Earth
Simple Models of Atmospheric Vortices
Atmospheric circulation systems have a wide variety of structures and there is no single mechanistic model that describes all their characteristics. However, we can construct simple kinematic models that capture some primary aspects of the flow. For simplicity, we will concentrate on idealized extra-tropical depressions. We will not consider hurricanes and tropical storms in any … Continue reading Simple Models of Atmospheric Vortices
Seeing beyond the Horizon
From a hilltop, the horizon lies below the horizontal level at an angle called the “dip”. Around AD 1020, the brilliant Persian scholar al-Biruni used a measurement of the dip, from a mountain of known height, to get an accurate estimate of the size of the Earth. It is claimed that his estimate was within … Continue reading Seeing beyond the Horizon
Was Space Weather the cause of the Titanic Disaster?
Space weather, first studied in the 1950's, has grown in importance with recent technological advances. It concerns the influence on the Earth's magnetic field and upper atmosphere of events on the Sun. Such disturbances can enhance the solar wind, which interacts with the magnetosphere, with grave consequences for navigation. Space weather affects the satellites of … Continue reading Was Space Weather the cause of the Titanic Disaster?
We are living at the bottom of an ocean
Anyone who lives by the sea is familiar with the regular ebb and flow of the tides. But we all live at the bottom of an ocean of air. The atmosphere, like the ocean, is a fluid envelop surrounding the Earth, and is subject to the influence of the Sun and Moon. While sea tides … Continue reading We are living at the bottom of an ocean
Ireland’s Mapping Grid in Harmony with GPS
The earthly globe is spherical; more precisely, it is an oblate spheroid, like a ball slightly flattened at the poles. More precisely still, it is a triaxial ellipsoid that closely approximates a “geoid”, a surface of constant gravitational potential [TM199 or search for “thatsmaths” at irishtimes.com]. Mapping the Globe Positions on the globe are given by … Continue reading Ireland’s Mapping Grid in Harmony with GPS
Weather Forecasts get Better and Better
Weather forecasts are getting better. Fifty years ago, predictions beyond one day ahead were of dubious utility. Now, forecasts out to a week ahead are generally reliable [TM198 or search for “thatsmaths” at irishtimes.com]. Careful measurements of forecast accuracy have shown that the range for a fixed level of skill has been increasing by one day every … Continue reading Weather Forecasts get Better and Better
A Ring of Water Shows the Earth’s Spin
Around 1913, while still an undergraduate, American physicist Arthur Compton described an experiment to demonstrate the rotation of the Earth using a simple laboratory apparatus. Compton (1892--1962) won the Nobel Prize in Physics in 1927 for his work on scattering of EM radiation. This phenomenon, now called the Compton effect, confirmed the particle nature of … Continue reading A Ring of Water Shows the Earth’s Spin
Spin-off Effects of the Turning Earth
On the rotating Earth, a moving object deviates from a straight line, being deflected to the right in the northern hemisphere and to the left in the southern hemisphere. The deflecting force is named after a nineteenth century French engineer, Gaspard-Gustave de Coriolis [TM164 or search for “thatsmaths” at irishtimes.com]. Coriolis was interested in the dynamics of machines, … Continue reading Spin-off Effects of the Turning Earth
Joseph Fourier and the Greenhouse Effect
Jean-Baptiste Joseph Fourier, French mathematician and physicist, was born in Auxerre 251 years ago today. He is best known for the mathematical techniques that he developed in his analytical theory of heat transfer. Over the past two centuries, his methods have evolved into a major subject, harmonic analysis, with widespread applications in number theory, signal … Continue reading Joseph Fourier and the Greenhouse Effect
From a Wide Wake to the Width of the World
The finite angular width of a ship's turbulent wake at the horizon enables the Earth's radius to be estimated. By ignoring evidence, Flat-Earthers remain secure in their delusions. The rest of us benefit greatly from accurate geodesy. Satellite communications, GPS navigation, large-scale surveying and cartography all require precise knowledge of the shape and form of the … Continue reading From a Wide Wake to the Width of the World
A Zero-Order Front
Sharp gradients known as fronts form in the atmosphere when variations in the wind field bring warm and cold air into close proximity. Much of our interesting weather is associated with the fronts that form in extratropical depressions. Below, we describe a simple mechanistic model of frontogenesis, the process by which fronts are formed. Life-cycle … Continue reading A Zero-Order Front
The Miraculous Spiral on Booterstown Strand
We all know what a spiral looks like. Or do we? Ask your friends to describe one and they will probably trace out the form of a winding staircase. But that is actually a helix, a curve in three-dimensional space. A spiral is confined to a plane – it is a flat curve. In general … Continue reading The Miraculous Spiral on Booterstown Strand
Tides: a Tug-of-War between Earth, Moon and Sun
All who set a sail, cast a hook or take a dip have a keen interest in the water level, and the regular ebb and flow of the tides. At most places the tidal variations are semi-diurnal, with high and low water twice each day [see TM144, or search for “thatsmaths” at irishtimes.com]. Equilibrium Tides In the … Continue reading Tides: a Tug-of-War between Earth, Moon and Sun
Trigonometric Comfort Blankets on Hilltops
On a glorious sunny June day we reached the summit of Céidín, south of the Glen of Imall, to find a triangulation station or trig pillar. These concrete pillars are found on many prominent peaks throughout Ireland, and were erected to aid in surveying the country [see TM142, or search for “thatsmaths” at irishtimes.com]. The pillars are about … Continue reading Trigonometric Comfort Blankets on Hilltops
Waves Packed in Envelopes
In this article we take a look at group velocity and at the extraction of the envelope of a wave packet using the ideas of the Hilbert transform. Interference of two waves A single sinusoidal wave is infinite in extent and periodic in space and time. When waves interact, the dynamics are more interesting. The … Continue reading Waves Packed in Envelopes
Geodesics on the Spheroidal Earth-II
Geodesy is the study of the shape and size of the Earth, and of variations in its gravitational field. The Earth was originally believed to be flat, but many clues, such as the manner in which ships appear and disappear at the horizon, and the changed perspective from an elevated vantage point, as well as … Continue reading Geodesics on the Spheroidal Earth-II
Geodesics on the Spheroidal Earth – I
Both Quito in Ecuador and Singapore are on the Equator. One can fly due eastward from Singapore and reach Quito in due course. However, this is not the shortest route. The equatorial trans-Pacific route from Singapore to Quito is not a geodesic on Earth! Why not? The General Equation for Geodesics Open a typical text … Continue reading Geodesics on the Spheroidal Earth – I
Staying Put or Going with the Flow
The atmospheric temperature at a fixed spot may change in two ways. First, heat sources or sinks may increase or decrease the thermal energy; for example, sunshine may warm the air or radiation at night may cool it. Second, warmer or cooler air may be transported to the spot by the air flow in a … Continue reading Staying Put or Going with the Flow
Energy Cascades in Van Gogh’s Starry Night
"Big whirls have little whirls that feed on their velocity, And little whirls have lesser whirls, and so on to viscosity." We are all familiar with the measurement of speed, the distance travelled in a given time. Allowing for the direction as well as the magnitude of movement, we get velocity, a vector quantity. In … Continue reading Energy Cascades in Van Gogh’s Starry Night
Inertial Oscillations and Phugoid Flight
The English aviation pioneer Frederick Lanchester (1868--1946) introduced many important contributions to aerodynamics. He analysed the motion of an aircraft under various consitions of lift and drag. He introduced the term ``phugoid'' to describe aircraft motion in which the aircraft alternately climbs and descends, varying about straight and level flight. This is one of the … Continue reading Inertial Oscillations and Phugoid Flight
The Water is Rising Fast
Seventy percent of the Earth is covered by water and three quarters of the world's great cities are on the coast. Ever-rising sea levels pose a real threat to more than a billion people living beside the sea. As the climate warms, this is becoming a greater threat every year [TM113 or search for “thatsmaths” … Continue reading The Water is Rising Fast
Mercator’s Marvellous Map
Try to wrap a football in aluminium foil and you will discover that you have to crumple up the foil to make it fit snugly to the ball. In the same way, it is impossible to represent the curved surface of the Earth on a flat plane without some distortion. [See this week’s That’s Maths … Continue reading Mercator’s Marvellous Map
The Hodograph
The Hodograph is a vector diagram showing how velocity changes with position or time. It was made popular by William Rowan Hamilton who, in 1847, gave an account of it in the Proceedings of the Royal Irish Academy. Hodographs are valuable in fluid dynamics, astronomy and meteorology. The idea of a hodograph is very simple. … Continue reading The Hodograph
Mode-S: Aircraft Data improves Weather Forecasts
A simple application of vectors yields valuable new wind observations for weather forecasting [see this week’s That’s Maths column (TM065) or search for “thatsmaths” at irishtimes.com]. It has often happened that an instrument designed for one purpose has proved invaluable for another. Galileo observed the regular swinging of a pendulum. Christiaan Huygens derived a mathematical … Continue reading Mode-S: Aircraft Data improves Weather Forecasts
Falling Bodies [1]: Sky-diving
Aristotle was clear: heavy bodies fall faster than light ones. He arrived at this conclusion by pure reasoning, without experiment. Today we insist on a physical demonstration before such a conclusion is accepted. Galileo tested Aristotle's theory: he dropped bodies of different weights simultaneously from the Leaning Tower of Pisa and found that, to a … Continue reading Falling Bodies [1]: Sky-diving
El Niño likely this Winter
This week’s That’s Maths column in The Irish Times (TM056 or search for “thatsmaths” at irishtimes.com) is about El Niño and the ENSO phenomenon. In 1997-98, abnormally high ocean temperatures off South America caused a collapse of the anchovy fisheries. Anchovies are a vital link in the food-chain and shortages can bring great hardship. Weather … Continue reading El Niño likely this Winter
Gauss’s Great Triangle and the Shape of Space
In the 1820s Carl Friedrich Gauss carried out a surveying experiment to measure the sum of the three angles of a large triangle. Euclidean geometry tells us that this sum is always 180º or two right angles. But Gauss himself had discovered other geometries, which he called non-Euclidean. In these, the three angles of a … Continue reading Gauss’s Great Triangle and the Shape of Space
Breaking Weather Records
In arithmetic series, like 1 + 2 + 3 + 4 + 5 + … , each term differs from the previous one by a fixed amount. There is a formula for calculating the sum of the first N terms. For geometric series, like 3 + 6 + 12 + 24 + … , each … Continue reading Breaking Weather Records
Simulating the Future Climate
The Earth's climate is changing, and the consequences may be very grave. This week, That’s Maths in The Irish Times ( TM040 ) is about computer models for simulating and predicting the future climate. Liffey Bursts its Banks: St. Stephen's Green Flooded Again The above is an improbable but not entirely impossible future headline. Sea … Continue reading Simulating the Future Climate
Interesting Bores
This week’s That’s Maths column in the Irish Times ( TM036 ) is about bores. But don't be put off: they are very interesting. According to the old adage, water finds its own level. But this is true only in static situations. In more dynamic circumstances where the water is moving rapidly, there can be … Continue reading Interesting Bores
A Hole through the Earth
“I wonder if I shall fall right through the earth”, thought Alice as she fell down the rabbit hole, “and come out in the antipathies”. In addition to the author of the “Alice” books, Lewis Carroll – in real life the mathematician Charles L. Dodgson – many famous thinkers have asked what would happen if … Continue reading A Hole through the Earth
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