statistics

seasonal cycle

The regular annual variation in a climate variable, often removed to study other signals.
140 related articles

Description

The seasonal cycle refers to the regular, repeating pattern of change in a climate variable—such as temperature, precipitation, or wind—that occurs over the course of a year. This cycle is driven primarily by the tilt of Earth's axis and its orbit around the Sun, leading to variations in solar radiation received at different latitudes and times of year. In climate science, the seasonal cycle is often considered a baseline signal that must be understood and removed to reveal other, less obvious variations, such as those due to El Niño, volcanic eruptions, or long-term climate change.

History

The recognition of seasonal patterns in weather dates back to ancient civilizations, but the systematic removal of the seasonal cycle in climate analysis became standard practice in the 20th century with the advent of statistical climatology.

How it works

The seasonal cycle is typically modeled as a periodic function with a period of one year, often represented by a sum of sine and cosine terms (a Fourier series). By fitting this model to observed data, scientists can estimate the average seasonal pattern for a given location and variable. Subtracting this fitted cycle from the raw data yields anomalies, which highlight deviations from the expected seasonal behavior and are used to study climate variability and change.

In practice

Seasonal cycle removal is essential in climate monitoring, seasonal forecasting, and the detection of climate change signals, as it allows scientists to isolate non-seasonal trends and events.

Fun fact

The seasonal cycle in atmospheric carbon dioxide is so pronounced that it creates a noticeable 'breathing' pattern in global CO2 measurements, with levels dropping in the Northern Hemisphere summer as plants absorb CO2.

Concept graph →

Related articles · 140

Stellar2026-08-112 minarXiv:2608.10819express
Solar Wind: Why Protons and Alpha Particles Heat Differently
The solar wind is a continuous stream of charged particles flowing from the Sun. It has two main components: protons (hydrogen nuclei) and alpha particles (helium nuclei, four times heavier).
Stellar2026-08-111 minarXiv:2608.11438express
The Solar Wind Changes Its Character
The solar wind is a stream of charged particles constantly blown off the Sun's surface, filling the entire solar system. It's not like a steady breeze: it has eddies, gusts, and calm patches. Scientists call this turbulence.
Stellar2026-08-092 minarXiv:2608.08470express
Rain on the Sun: Why It Falls Both Ways
In the solar corona, it rains from time to time — only not water, but plasma. The hot gas cools, clumps into blobs, and rushes downward along magnetic loops, like drops running down invisible gutters.
Stellar2026-07-223 minarXiv:2607.19730
Solar Heat Pump: Why the Equator Spins Faster Than the Poles
27 days at the equator, 32 at the poles. Five days' difference, and over a year, the equator gains almost a week. A gas ball 1,4 million kilometers in diameter spins like a layered top: each layer moves at its own speed.
Where in the Atmosphere Do the Traces of Our Emissions Hide?
A translator in a conference hall tries to convey the speaker's words, but the hall is noisy: someone coughs, chairs creak, and the street outside is loud. If the speaker lowers their voice, the translator still keeps translating, but their voice drowns in the noise.
Geophysics2026-06-242 minarXiv:2606.26042express
Magnetic Portrait of Earth's Core
Earth's magnetic field is like an invisible shield that protects us from cosmic radiation. But if you look closely at its long-term averaged pattern, you'll notice that this shield isn't perfectly smooth: it has its own "seams" and "patches." New research using computer simulations of the geodynamo shows that…
Seasonal Climate Is Predictable Beyond Chaos
Two pendulums suspended from a single invisible spring swing in a shared air current. One always lags the other by exactly half a period: when the first swings left, the second is already returning from the right. By watching the first, you can tell where the second will be half a period later.
Are Tropical Cyclones Intensifying? It's Not Just the Atlantic
In 1991, Mount Pinatubo erupted with such force that it blanketed the planet in a thin veil of ash and gases for years. That veil, like a blanket on a hot night, trapped heat and cooled the ocean surface, causing tropical sea surface temperatures to dip. This event marks the start of a detective story about why some oceans are spawning ever more ferocious hurricanes while others remain calm.
An Entropic Clamp for El Niño
Every winter, the tropical Pacific Ocean seems to replay the same script: sea surface temperatures off the coast of Peru rise, trade winds weaken, and a wave of droughts and floods spreads across the planet. This is El Niño, and its peak almost always falls in December. Why winter in particular?
The Ocean Conveyor on the Brink
In the Atlantic, a giant invisible conveyor operates: warm surface waters flow north, cool, sink, and return south. This circulation, AMOC, carries heat, making Europe noticeably milder than Canada at the same latitudes. But the conveyor isn't eternal: if diluted by fresh water from melting Greenland ice, the engine stalls.
Stellar2026-05-262 minarXiv:2605.27057express
Space Weather by the Seasons
The Sun doesn't burn steadily: it erupts in series. Like a campfire that dies down and then suddenly throws out showers of sparks, these "fiery seasons" last from six months to a year and a half, and during them the star shows an unusually high number of sunspots.
MOSAIC: How to Extract Meaning from the Noise of Scientific Data
In a hall with a hundred instruments, a symphony is playing, but the conductor is hidden behind a screen. The scientist hears only the notes played by the instruments and wants to understand who sets the rhythm. Scientific data resembles such an orchestra: we record instrument readings but do not see the hidden mechanisms that drive them.
General Relativity2026-04-272 minarXiv:2604.24867express
Stellar Tuning: Why Gravity Suddenly Changes Its Character
If you drop an ice cube into a glass of water, it will float until it melts. But if you cool the water slowly, at some point it all freezes at once: that's a first-order phase transition: abrupt, with a clear boundary.
Stellar2026-04-151 minarXiv:2604.13585express
Sunspots as a Mirror of the Sun's Interior
Magnetic fields on the surface of the Sun appear as dark spots and bright faculae. But they are born deep inside, where flows of hot gas act like a giant dynamo. The question is whether sunspots on the surface can predict what will happen inside the star years from now. The authors applied a mathematical theorem similar to the rule linking the area of a shape to its boundary.
Climate Waves: How Solar Cycles Echo in Brazil's Rainfall
The Sun pulses in a slow rhythm, and that rhythm can be heard in the rains over Brazil. Sunspots on the solar disk thicken and thin roughly every eleven years, and along with them, pressure in the Pacific Ocean shifts, sea surface temperatures change, and then rainfall amounts in the northeast of the country follow suit.
The Dance of Two Pendulums: Why the Monsoon Can Be Predicted 18 Months Ahead
Two pendulums hang on the same wall, swinging out of sync, but suddenly they move as one, only with an 18-month delay. One pendulum is the Indian monsoon, the seasonal wind that brings rain to South Asian farmland. The other is the deep water of the tropical oceans, which slowly accumulates heat and remembers it for years.
The Climate Has Become Worse at Shedding Heat
Imagine a radiator in a room: it heats up, but if its surface is clogged with dust, heat escapes less efficiently. Something similar is happening to our planet. Earth receives energy from the Sun and must radiate the excess back into space, otherwise temperatures rise. Scientists call this ability to shed excess heat radiative feedback.
El Niño 2026: Two Barometers, One Forecast
Two barometers hang on the wall. One reads clear, the other says partly cloudy. Which weather do you trust? That is roughly the question facing a group of climate scientists when two independent methods predicted different futures for the Pacific Ocean in 2026.
A Student Who Learned Physics from a Textbook
A student learned physics from a textbook and is taking an exam. The first two problems are solved brilliantly, but on the third, they err on something not covered in the book. That is roughly what the hybrid atmospheric model NeuralGCM faced when run through three levels of testing: cyclones, El Niño, and anomalous warming.
Exoplanets2026-02-102 minarXiv:2602.10369express
The Fourth Spring of Climate
A planet's climate is like an old spring mattress: press down on one edge, the springs compress; let go, they rebound and put everything back. Earth has three such springs, working as a team. Carbon dioxide weathers out of rocks, clouds reflect sunlight, and ice caps bounce heat back into space. Together, they keep the planet from boiling or freezing.
Earth Can Heat Itself Up
Glaciers don't just darken from soot. Their surfaces host tiny algae that, as temperatures rise, bloom and turn the ice dark. Dark ice absorbs more sunlight, melts faster, and further warms the planet. It's like how a black t-shirt in the sun gets hotter than a white one. The second player in overheating is forests.
Exoplanets2026-01-121 minarXiv:2601.07159express
The Climate Swings of Ancient Mars
For a long time, the climate of ancient Mars remained a mystery: the beds of dried-up rivers spoke of water, but models couldn't explain how it got there — after all, 4 billion years ago the Sun shone 30% dimmer. New research shows that the planet swayed, as if on a swing, between long glaciations and short wet epochs.
q-fin.PR2025-12-272 minarXiv:2512.22660
Climate in the Price of a Bond: How Machine Learning Predicts Catastrophe Bond Coupons
In 1992, Hurricane Andrew tore through Florida, leaving insurers with $$15.5 billion in losses. Many companies went bankrupt, and the market devised a way to shift disaster risk onto investors: catastrophe bonds. These securities pay generous coupons as long as a specified disaster does not occur, such as a hurricane of a certain strength or an earthquake in a particular region.
Climate Rewires Teleconnections
A warm ocean off the coast of Peru can make winter in Moscow unusually mild. Climate scientists call these invisible threads that link weather in distant corners of the planet teleconnections. For a long time, they were thought of as something like permanent wiring: the signal sources may pulse, but the wires themselves lie still.
Storm in the Climate Labyrinth
Every day, about 40,000 thunderstorms flash across the planet. In that moment, the atmosphere resembles an orchestra without sheet music: warm air rises like a bow stroke, winds aloft carry the melody, and lightning punctuates the finale. But who conducts this orchestra?
Twin Winds: How Rotation and Divergence Drive El Niño
Two conductors stand before one orchestra. One waves the baton quickly, setting the tempo every few bars. The second is almost motionless, but his slow breathing changes the overall sound throughout the symphony. So it is in the tropical Pacific: one part of the wind governs the fast oscillations of El Niño, the other governs decadal climate shifts.
Warm Ocean, Few Hurricanes: The 2025 Season as an Orchestra Without a Conductor
The orchestra assembled, the instruments were tuned, but there was barely any music: that's what the 2025 Atlantic hurricane season looked like. The ocean was the fifth warmest on record, and a weak La Niña usually adds strength to storms. But instead of a continuous concert, we got isolated thunderous chords: three Category 5 hurricanes, with silence in between. Why was the orchestra silent?
Climate as an Orchestra Without a Conductor: Rhythms Over Trends
The climate of the United States is not a straight line creeping upward. It is an orchestra without a conductor, where every violin and every drum plays its own part, and together they create an intricate pattern of warm and cold, wet and dry years.
Climate Norms Under Pressure from Trends
A camera on a tripod shoots the same landscape for decades. If you don't touch the lens, the images get hazy: the landscape changes, but the focus stays put. That's roughly how climate norms work. According to World Meteorological Organization rules, they are calculated as the average over the last 30 years.
Quantum Physics2025-11-061 minarXiv:2511.04028express
Heat in Reverse: When Hot Freezes from Cold
Water always flows downhill, and heat from hot to cold. That's what энтропия dictates. But the quantum world finds loopholes. Physicists made light particles interact with hot and cold environments in an uncertain sequence — like a flipped coin that hasn't landed yet.
A Switchback Pendulum: How Seasons Drive El Niño
Imagine a pendulum that is pushed in time with the seasons: harder in winter, softer in summer. But this pendulum has a quirk: a switch that operates with a delay. When the pendulum passes through zero, the switch clicks and changes the direction of the push. That is exactly how the simplified El Niño model built by mathematicians works.
Ocean Seesaw: The Hidden Heat Exchange in the South China Sea
In summer, the South China Sea can show a strange pattern: the water in the north warms while the south cools at the same time. A year later, it's the opposite. This isn't random; it's a steady seesaw that the ocean rocks every summer.
Rain Relay: How Rare Runners Shape South American Weather
An invisible relay race runs through Earth's tropics: a wave of heavy rain and winds, which meteorologists call the Madden–Julian Oscillation, travels eastward at about five meters per second. Most runners tire quickly, but rare marathoners carry the torch all the way across the Pacific.
A Bridge Between Typhoon and Current: How El Niño Is Born
The tropical Pacific Ocean lives in two rhythms. The first is fast: a wave of thunderstorms born over the Indian Ocean races eastward and dies out off the coast of the Americas within a month or two. The second is slow: every few years, the ocean surface warms enough to alter weather across the entire planet. That is El Niño. Between these rhythms lies a bridge, and building it took climatologists decades.
Thermometer in the Red: Heat and Rain in Jalisco in 2024
In May 2024, thermometers in Jalisco seemed to go haywire: on May 10, one station recorded 38.4°C, nearly matching the historical maximum from 1994. The heat was so intense that even agave plants, accustomed to scorching conditions, slowed their growth. And the rains, which usually arrive in June, were delayed, leaving farmers nervously glancing at the sky.
The Entropy of Climate Swings
You can sit on a seesaw and pump your legs, or you can just tip from one side to the other. The Pacific Ocean does both. Every few years, warm water off the coast of Peru gives way to cooler water, and rainfall patterns, winds, and entire ecosystems across half the planet reshuffle. These shifts are called El Niño and La Niña, together known as ENSO: Earth's climate seesaw.
A Digital Twin of the Atmosphere: How a Neural Network Speeds Up Climate Modeling by 350 Times
A translator at a high-stakes negotiation doesn't just render words quickly; they make sure the meaning doesn't get lost. CAMulator does the same: it takes the complex climate model CAM6 and translates it into the language of a neural network that runs hundreds of times faster, without losing the physical essence.
El Niño: Fading Out or Self-Sustaining?
The Pacific Ocean breathes. Every few years, its warm western "lung" exhales eastward, and from Peru to Indonesia, rains, droughts, and hurricanes shift. This breath is called El Niño–Southern Oscillation, or ENSO.
The Pacific Ocean Sends a Signal: No El Niño in 2025
The Pacific Ocean is a giant network of nerve endings that warns of an impending attack a year in advance. In 2023–2024, El Niño, the warm phase of the Pacific climate oscillation, pushed global temperatures to record highs. Now, two independent methods, like two doctors examining the same symptoms, agree: no new attack in 2025.