An annual cycle refers to a set of changes or events that uniformly, or consistently, take place at the same time of year. In

biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...

, the annual cycle for plants and animals details behavioral and chemical changes that take place as the seasons advance. In business, a

business cycle Business cycles are intervals of expansion followed by recession in economic activity. These changes have implications for the welfare of the broad population as well as for private institutions. Typically business cycles are measured by examin ...

refers to the way modelling and analysis is applied to the periodic development and marketing of new products and services. In

religion Religion is usually defined as a social- cultural system of designated behaviors and practices, morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, or organizations, that generally relates humanity to supernatural, ...

, the annual cycle refers to the various celebrations or memorials that occur in the same sequence from year to year. For example, in

Christianity Christianity is an Abrahamic monotheistic religion based on the life and teachings of Jesus of Nazareth. It is the world's largest and most widespread religion with roughly 2.38 billion followers representing one-third of the global pop ...

the liturgical year is an annual cycle, which for some Christian denominations is composed of the ''temporal cycle'' that tracks the events in the life of

Christ Jesus, likely from he, יֵשׁוּעַ, translit=Yēšūaʿ, label=Hebrew/Aramaic ( AD 30 or 33), also referred to as Jesus Christ or Jesus of Nazareth (among other names and titles), was a first-century Jewish preacher and religious ...

, and the ''sanctoral cycle'' which tracks the various saint's days. Some Christian churches only observe the ''temporal cycle''.Flesher, Pau
"Christian Time and Worship"
''Exploring Religions'' University of Wyoming In

climatology Climatology (from Greek , ''klima'', "place, zone"; and , ''-logia'') or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 years. This modern field of study ...

, an annual cycle is the part of a measured quantity's fluctuation that is attributed to Earth's changing position in

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

over the course of the year. Such quantities might be influenced directly (e.g. incoming

solar radiation Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre ( ...

at a point at the surface) or indirectly (e.g. stratospheric

westerlies The westerlies, anti-trades, or prevailing westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the high-pressure areas in the horse latitudes and trend t ...

and

easterlies The trade winds or easterlies are the permanent east-to-west prevailing winds that flow in the Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisph ...

over the winter and summer hemispheres, respectively) by orbital position. Mathematically, the climatological annual cycle is commonly estimated from observational data or model output by taking the average of all Januaries, all Februaries, and so forth. If the observational record is long enough and conditions are stationary (i.e. there is no significant long-term trend), a meaningful annual cycle will result that can be used to calculate an anomaly time series.

Notes

Earth sciences {{climate-stub