Temporal and Spatial Distribution Characteristics of Frost Period in Qaidam Basin from 1961 to 2020
Using daily minimum temperature data from 1961 to 2020 in the Qaidam Basin of Qinghai Province,combined with frost frequency data from 1978 to 2020,this study investigated the spatiotemporal distribution character-istics of frost occurrence in the Qaidam Basin.The results showed that the Qaidam Basin was mainly characterized by late frost,and in the past 60 years,the number of frost free days has shown a fluctuating and prolonged trend,with a climate inclination rate of 4.5 d·(10a)-1.The average frost free period has increased by 14 days;The number of frost days in the Qaidam Basin showed a significant decreasing trend,with a climate inclination rate of-4.6 d·(10a)-1.From the perspective of inter decadal changes,from the 1960s to the 1990s,the number of frost days was longer than the annual average;The mutation test results showed that the frost free period in the Qaidam Basin under-went a sudden change between 1994 and 1995,and the number of frost days underwent a sudden change between 1996 and 1997;In terms of spatial distribution,the late frost in the Qaidam crop planting area had the characteristic of more occurrences in the eastern and northwestern regions,and fewer occurrences in the middle region;The frequency of late frost occurrence in the Qaidam Basin exhibited a certain pattern of periodic oscillation,mainly with a period of 10-17 years;The occurrence of late frost in the Qaidam Basin showed a consistent pattern of more or less occurrences,and there were also significant differences in distribution between the east and west.