今年缘何早出伏？

Core Points - The end of the "Sanfu" period this year is marked as a "short Sanfu," concluding 30 days earlier than the previous years, with an early end by 5 days compared to last year, 1 day compared to the year before, and 6 days compared to the year before that [1] - The "Sanfu" period consists of three phases: the initial phase, the middle phase, and the final phase, with the initial and final phases fixed at 10 days each, while the middle phase can vary between 10 to 20 days [1] - The determination of the duration of "Sanfu" is based on the ancient Chinese calendar system, specifically the "Geng" days following the summer solstice and the first "Geng" day after the beginning of autumn [1][3] - The current "Sanfu" period breaks a 10-year streak of 40-day durations from 2015 to 2024, initiating a new cycle of alternating 30 and 40-day durations from 2025 to 2036 [3] - Weather conditions post "Sanfu" are characterized by a gradual temperature decline, but the "autumn tiger" phenomenon may still persist, indicating a slow transition from summer heat [5]