Passive Microwave Remote Sensing Of Lake Ice Phenology Monitoring And Comparative Analysis

Lake ice phenology is a term used to describe the seasonal circulation of lake ice cover and is an indicator of climate change.Passive microwave data can be used in long-term monitoring of lake ice phenology,but the survey found that there is a lack of rules for discriminant of lake ice phenology based on passive microwaves,which makes the regional contrast of lake ice phenology based on passive microwave monitoring lacking.In this paper,the passive microwave data is used as the remote sensing data source,and the Nearest Neighbor is used to obtain the brightness and temperature information of the lake sampling point.Through the MODIS normalized snow index product(NDSI)is used for lake ice identification and cloud removal processing,the time series of lake ice extent and coverage data are obtained.Then the obtained passive microwave brightness information of the lake is compared with the lake ice coverage ratio data obtained by MODIS.At the same time,combined with the temperature and fractional snow cover data,a set of lake ice phenological discriminant rules based on passive microwave remote sensing data is developed.The rules are divided into four categories,which can be applied to the discriminant of lakes and lakes ice phenology in different regions.The comparison between the lake ice phenology obtained by this discriminant rule and the optical monitoring results and ground observation results shows that the passive microwave monitoring results are highly consistent with MODIS and ground monitoring results,but there are also differences.That is,for the start of freezing parameters,the results monitored by passive microwaves are consistent with the MODIS monitoring results,but are slightly earlier than the ground observation;for the completely frozen parameters,the passive microwave and MODIS monitoring results are later than the ground observation,and the passive microwave monitoring results are slightly earlier than MODIS;for the beginning of melting parameters,ground observations are later than passive microwave and MODIS monitoring results;for complete melting parameters,ground observations results are consistent with passive microwaves,but ground observations results are later than MODIS.On this basis,the lake ice phenological parameters of 91 lakes(sampling points)in the three regions of Northern Europe,Qinghai-Tibet Plateau and Mongolian Plateau were obtained and the variation characteristics of lake ice phenology in the three regions were compared and analyzed.The results show that the lake ice phenology of the Northern Europe varies with latitude,while in the Tibetan Plateau and Mongolian Plateau,the lake ice phenology presents spatial agglomeration.The lake ice cover duration of the three regions showed a trend of shortening;the freezing parameters showed a trend of delay and the complete melting parameters are in an early trend.However,40% of the lakes ice in the Tibetan Plateau showed an extended trend.Through correlation analysis of the driving factors affecting the variation of lake ice phenology in the Tibetan Plateau shows that the lake mineralization has little effect on parameters of the lake ice phenology,while the lake water volume is negatively correlated with the lake ice cover duration;the lake water volume is positively correlated with the start freezing date,and the lake water volume was not significantly correlated with the full melting date.The altitude of the lake is positively correlated with the duration of lake ice cover,negatively correlated with the date of start freezing date,and positively correlated with complete melting.Although these three factors are still unable to effectively answer the reasons for the extension of lake ice cover time on the Tibetan Plateau,they provide more ideas for the analysis of lake ice phenology.