Comparative analysis of the cold surge characteristics over China before and after 2000北大核心CSCD

Based on the daily minimum temperature data in China from 1961 to 2018, using n-order polynomial fitting, sliding t-test, empirical Orthogonal Function analysis, Morlet wavelet transform and other methods, this paper reveals the temporal and spatial distribution characteristics of the number of cold surge (CS) day, CS frequency and CS intensity by time and region. The results are as follows. On a national level, the number of CS day, CS frequency, and CS intensity decreased from 1962 to 2000. Specifically, the trend of every element of CS has changed from a previous decrease trend to an increase trend, and the inflection point was around 2000. The CS activity occurred more frequently, became more strengthen, and last for longer time after 2000. There are obvious spatial differences in the number of CS days, CS frequency, CS intensity and their changing trends in China. The number of CS days and CS frequency reach the maximum value in northeast China and northern Inner Mongolia. Meanwhile, the CS intensity value is low in the southeast China and high in the northwest China, with the exception of southern Xinjiang. The changes in the number of CS day and the CS frequency are mainly manifested as the “Northeast, Southwest Reverse Pattern”, the CS intensity is mainly manifested as the “Uniform Change Pattern”. The number of CS day, CS frequency, and CS intensity did not change significantly after, but a significant transition point was detected in 1980. On a regional scale, from 1962 to 2018, the number of CS day, frequency and intensity of cold surge in all regions showed a decreasing trend, while they increased after 2000. In the northern and northeastern of China, mean of three elements of cold surge increased after 2000. The transition year was different in different regions. The transition year of three elements of cold surge in Northeast China were the earliest. Mean value of the number of CS day, CS frequency, and CS intensity have an oscillation period of 3~5 years in total China and all regions. In addition, the periodic oscillations of the number of CS day and CS frequency in all regions are basically the consistent. © 2022 Science Press (China).

Comparative analysis of the cold surge characteristics over China before and after 2000

Based on the daily minimum temperature data in China from 1961 to 2018， using n-order polynomial fitting， sliding t-test， empirical Orthogonal Function analysis， Morlet wavelet transform and other methods， this paper reveals the temporal and spatial distribution characteristics of the number of cold surge （CS） day， CS frequency and CS intensity by time and region. The results are as follows. On a national level， the number of CS day， CS frequency， and CS intensity decreased from 1962 to 2000. Specifically， the trend of every element of CS has changed from a previous decrease trend to an increase trend， and the inflection point was around 2000. The CS activity occurred more frequently， became more strengthen， and last for longer time after 2000. There are obvious spatial differences in the number of CS days， CS frequency， CS intensity and their changing trends in China. The number of CS days and CS frequency reach the maximum value in northeast China and northern Inner Mongolia. Meanwhile， the CS intensity value is low in the southeast China and high in the northwest China， with the exception of southern Xinjiang. The changes in the number of CS day and the CS frequency are mainly manifested as the “Northeast， Southwest Reverse Pattern”， the CS intensity is mainly manifested as the “Uniform Change Pattern”. The number of CS day， CS frequency， and CS intensity did not change significantly after， but a significant transition point was detected in 1980. On a regional scale， from 1962 to 2018， the number of CS day， frequency and intensity of cold surge in all regions showed a decreasing trend， while they increased after 2000. In the northern and northeastern of China， mean of three elements of cold surge increased after 2000. The transition year was different in different regions. The transition year of three elements of cold surge in Northeast China were the earliest. Mean value of the number of CS day， CS frequency， and CS intensity have an oscillation period of 3~5 years in total China and all regions. In addition， the periodic oscillations of the number of CS day and CS frequency in all regions are basically the consistent.