Spatial–Temporal Variations in Frost-Free Days During 1961–2023 in Qinghai Province, China

Rational development and utilization of cli mate resources are essential for mitigating frost disasters, particularly in high-altitude regions. This study investigates the spatiotemporal characteristics of frost events in Qinghai Province to improve understanding of frost evolution under climate change. Daily minimum temperature data from 51 meteorological stations from 1961 to 2023 were analyzed to determine the first frost date (FFD), last frost date (LFD), and frost-free period (FFP), along with their trends and influencing factors. Results show that the mean FFD, LFD, and FFP were 5 October, 14 May, and 144 days, respectively. Over the past six decades, LFD advanced, whereas FFD was delayed, leading to a marked extension of FFP, with trends of 2.08, 2.87, and 4.68 days per decade, respectively. These changes became more pronounced after the 1990s. Spatially, lower-altitude regions exhibited later FFD, earlier LFD, and longer FFP, whereas higher-altitude regions showed the opposite pattern. Correlation analysis indicates that frost characteristics are most strongly influenced by altitude, followed by latitude and longitude. Overall, climate warming has shortened the frost season and extended the growing period in Qinghai Province. These findings provide a scientific basis for optimizing agricultural zoning, adjusting cropping systems, and improving climate resilience in cold, high-altitude regions.