Precession Affects the Timing and Duration of Summer and Rainy Season in East Asia

East Asia, a densely populated economic center, is profoundly influenced by the seasonality of temperature and precipitation, which is vital for its agriculture and ecosystem. Geological records, such as speleothems and lake sediments, reveal that precession influences orbital climate variabilities in this region. However, they often fail to capture seasonal-scale variations. Here, by reconstructing a full precession cycle using the Alfred Wegener Institute Earth System Model (AWI-ESM), we examine how precession impacts the seasonality of temperature and precipitation in the East Asia. Our simulations illustrate that precession changes the timing and duration of summer and rainy season in this region. Specifically, under high eccentricity, the summer can vary in duration by up to 57 days, with the onset and termination varies by up to 48 and 52 days, respectively. Similarly, the duration of the rainy season can vary by up to 21 days, with the onset and termination date shift by up to 31 days and 35 days separately. Further analysis reveals that precession controls these changes by reshaping the timing of perihelion, which modulates surface temperature and the position of the subtropical high system. These findings emphasize the critical role of changing seasonality of temperature and precipitation in refining paleoclimate interpretations, offering insights into precession-driven climate dynamics in subtropical regions and providing a theoretical basis for future climate projections.