Earth Science - Seasonal Changes

- Cause of Seasonal Changes Due to the Earth's axis being tilted at 23.5 degrees while revolving around the sun, the sun's altitude changes. As the solar energy received increases and decreases accordingly, seasonal changes occur. - Definition of Meteorological Seasons (Based on Korea Meteorological Administration) Spring: The first day the average temperature exceeds 5°C Summer: The first day the average temperature exceeds 20°C Autumn: The first day the average temperature drops below 20°C Winter: The first day the average temperature drops below 5°C However, even if the temperature reaches 5°C or 20°C, they don't immediately announce a seasonal change. Instead, they use a 9-day moving average, meaning they announce the seasonal change based on the first day the threshold is reached using 9 days of weather data. The reason for using a 9-day moving average is to remove errors caused by temporary temperature fluctuations. Temperature standards vary by country. For example, China uses 10°C and 22°C as their standards. They also use a 5-day moving average. So, the conclusion is that autumn hasn't arrived in South Korea yet, except for high-altitude areas.