Diverse variations in middle and high latitudes of the Northern Hemisphere spring phenology sensitivity to diurnal temperature during 1982–2015

Abstract Recent studies have revealed that the influence of diurnal temperature on spring phenology is asymmetric, and the faster night‐time warming in the Northern Hemisphere (NH) has a complex impact on spring phenology. Our understanding from the sensitivity of the start of the growing season (SOS) to daytime (S T daytime) and night‐time temperatures (S T ₙight‐time) has urgently needs to be improved. In this study, the SOS sensitivity to diurnal temperature in the middle and high latitudes of the NH (>30°N) from 1982 to 2015 is estimated. The results indicate that although SOS showed stronger sensitivity to daytime than night‐time temperature in most parts of the study areas, the influence of daytime temperature on SOS is decreasing, while the influence of night‐time temperature on SOS is increasing. The variations in S T daytime and S T ₙight‐time along the latitude gradient were significantly correlated with the warming rate of the preseason diurnal temperature (p <. 01). The SOS between 40°N and 70°N was more sensitive to daytime temperature, while S T ₙight‐time was higher than S T daytime at other latitudes due to topography and rapid night‐time warming. On the altitude gradient, the SOS was more sensitive to daytime temperature in areas below 800 and 2, 000–4, 000 m. S T ₙight‐time exceeded S T daytime at other altitudes owing to night‐time warming relief of the severe restrictions on phenological processes and the reduction in frost risk. To reach a comprehensive characterization of the interaction between vegetation and climate systems, the current study suggests more investigation on the response of SOS to diurnal temperature on large scales.