夜光云季起始时间的长期变化特征及其影响因素OA

Polar Mesospheric Clouds(PMCs),as ice crystal clouds formed in the middle and upper at-mosphere(approximately 83 km high),have a seasonal onset that serves as an important parameter for studying the coupling processes between thermodynamics and dynamics in the polar mesosphere.Based on multi-source observational data from 1979 to 2023,the long-term evolution characteristics of the on-set of PMCs in both hemispheres are systematically analyzed,and their correlations with the reversal time of stratospheric zonal mean wind and solar activity are examined.Results show that there are sig-nificant differences in the onset of PMCs between the two hemispheres:the interannual variation(with a standard deviation of 22 d)in the southern hemisphere is about twice that in the northern hemisphere(11 d),which may be related to differences in thermal and dynamic processes such as inter-hemispheric circulation modes and the intensity of gravity wave activity.In the southern hemisphere,the onset of PMCs season exhibits a very strong positive correlation with the reversal time of the stratospheric zonal mean wind,while in the northern hemisphere,although a negative correlation is observed,the approxi-mately 60-day difference does not directly indicate a causal relationship between the two.The regula-tion of the onset by solar activity(Lyman-α radiation)also shows hemispheric asymmetry.In the north-ern hemisphere,there was a certain negative correlation with solar activity before 2011 that later wea-kened due to changes in the stratospheric dynamic background,whereas the southern hemisphere exhi-bited only a weak response.This indicates that both solar radiation effects and dynamic processes may jointly contribute.In addition,the discrepancies among multi-source data suggest that differences in de-tection systems and data types can introduce uncertainties in studies of the long-term variation charac-teristics of PMCs.