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- The seasonal year is the time between successive recurrences of a seasonal event such as the flooding of a river, the migration of a species of bird, or the flowering of a species of plant. The need for farmers to predict seasonal events led to the development of calendars. However, the variability from year to year of seasonal events (due to climate change or just random variation) makes the seasonal year very hard to measure. This means that calendars are based on astronomical years (which are regular enough to be easily measured) as surrogates for the seasonal year. For example, the ancient Egyptians used the heliacal rising of Sirius to predict the flooding of the Nile. A study of temperature records over the past 300 years suggests that the seasonal year is governed by the anomalistic year rather than the tropical year.This suggestion is surprising because the seasons have been thought to be governed by the tilt of the Earth's axis (see Effect of sun angle on climate). The two types of years differ by a mere 4 days over 300 years, so Thompson's result may not be significant. However, the result is not unreasonable. The seasons can be considered to be an oscillating system driven by two inputs with slightly different frequencies: the total input of energy from the sun varies with the anomalistic year, while the distribution of this energy between the hemispheres varies with the tropical year. In other physical situations, oscillating systems driven by two similar frequencies can latch onto either one. One point that must be considered is that the oscillation arising from the tilt of the axis is much greater than that arising from the distance of the sun. (en)
- 季節年是一個季節性事件重複出現的時間間隔，例如河水的氾濫、特定某種鳥類的遷徙、或某種植物的花成長。 因為預測季節性事件農民的需要導致日曆的發展，但是一年又一年的季節事件由於年的變異性（氣候變化或是隨機的變化）導致季節年的長度很難量度，這意味著日曆是基於天文年（它的規則性很容易測量）作為季節年的代理項。例如，古埃及人使用天狼星的來預測尼羅河的氾濫。 對過去300年溫度記錄的研究，認為季節年受到近點年的支配，而不是回歸年。 這項建議令人驚訝的是因為一向都認為季節受到地球自轉軸的傾斜支配（參見太陽角度對氣候的影響）。這兩種型態的年每300年只有4天的差異，所以湯普森的結果可能並不重要，但是，這樣的結果並非不合理的。季節可以被視為兩個稍有不同的頻率，被輸入振盪系統的輸出結果：輸入的總能量來自太陽，隨著近點年變化；但是能量在兩個半球的分配隨著回歸年變化。在其它的物理情況下，由兩個相似的頻率驅動的振盪系統可以鎖定在其中任何一個的頻率上。必須考慮的一點是，軸對太陽的傾斜所導致的影響必須大於太陽距離變化所導致的影響。 (zh)
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- 季節年是一個季節性事件重複出現的時間間隔，例如河水的氾濫、特定某種鳥類的遷徙、或某種植物的花成長。 因為預測季節性事件農民的需要導致日曆的發展，但是一年又一年的季節事件由於年的變異性（氣候變化或是隨機的變化）導致季節年的長度很難量度，這意味著日曆是基於天文年（它的規則性很容易測量）作為季節年的代理項。例如，古埃及人使用天狼星的來預測尼羅河的氾濫。 對過去300年溫度記錄的研究，認為季節年受到近點年的支配，而不是回歸年。 這項建議令人驚訝的是因為一向都認為季節受到地球自轉軸的傾斜支配（參見太陽角度對氣候的影響）。這兩種型態的年每300年只有4天的差異，所以湯普森的結果可能並不重要，但是，這樣的結果並非不合理的。季節可以被視為兩個稍有不同的頻率，被輸入振盪系統的輸出結果：輸入的總能量來自太陽，隨著近點年變化；但是能量在兩個半球的分配隨著回歸年變化。在其它的物理情況下，由兩個相似的頻率驅動的振盪系統可以鎖定在其中任何一個的頻率上。必須考慮的一點是，軸對太陽的傾斜所導致的影響必須大於太陽距離變化所導致的影響。 (zh)
- The seasonal year is the time between successive recurrences of a seasonal event such as the flooding of a river, the migration of a species of bird, or the flowering of a species of plant. The need for farmers to predict seasonal events led to the development of calendars. However, the variability from year to year of seasonal events (due to climate change or just random variation) makes the seasonal year very hard to measure. This means that calendars are based on astronomical years (which are regular enough to be easily measured) as surrogates for the seasonal year. For example, the ancient Egyptians used the heliacal rising of Sirius to predict the flooding of the Nile. (en)
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- Seasonal year (en)
- 季節年 (zh)
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