Abstract:In this study,utilizing the Normalized Difference Vegetation Index (NDVI) and meteorological data from 1982 to 2016 in the Qinghai region of China,we adopted a copula function method based on the Markov Chain Monte Carlo approach.Our goal was to explore the relationship between the NDVI and diurnal-nocturnal asymmetric warming during the growing seasons in the alpine climate zone of Qinghai Province from 1982 to 2016.The study results revealed the joint probability distribution and its seasonal differences between the diurnal-nocturnal warming and the NDVI.Initially,the paper presents the trends in seasonal diurnal-nocturnal temperatures and the NDVI over the years in the alpine climate region,followed by an analysis of diurnal-nocturnal temperatures using the copula function method to investigate the statistical characteristics between diurnal-nocturnal warming and the NDVI.It was found that the impact of diurnal-nocturnal warming on NDVI varies significantly from season to season,with the strongest correlation in autumn,followed by summer and spring.This suggests a clear seasonality in the influence of diurnal-nocturnal warming on vegetation growth.There is a specific temperature threshold between diurnal-nocturnal warming and the NDVI;when the diurnal-nocturnal warming is below this threshold,a positive correlation is observed,indicating that appropriate temperature increases promote vegetation growth.However,once this threshold is exceeded,the positive impact of diurnal-nocturnal warming on the NDVI becomes a suppression effect.Additionally,the paper examines the long-term impact of diurnal-nocturnal warming changes on vegetation growth by analyzing the joint probability distribution of diurnal-nocturnal warming and the NDVI during different recurrence periods.The results show that,in lower recurrence periods,the joint probability of diurnal-nocturnal warming with the NDVI is high,indicating more frequent favorable conditions for vegetation growth.Conversely,higher recurrence periods correspond to lower joint probabilities of diurnal-nocturnal warming with the NDVI,suggesting suppressed vegetation growth.This indicates that the relationship between diurnal-nocturnal warming and the NDVI becomes more complex within certain recurrence periods,which may be related to the regional climatic conditions,vegetation types,and other ecological factors.Overall,this study provides a new perspective on exploring the complex relationship between diurnal-nocturnal asymmetric warming and vegetation dynamics within the context of climate change.This is not only crucial for predicting and assessing the potential impact of future climate change on vegetation in alpine regions,but also provides a scientific basis for the management and conservation of these fragile ecosystems.