Study On Spatiotemporal Dynamics Of Snow Cover In The Amur River Basin Based On MODIS

Snow cover,as one of the important types of land cover.plays an important role in the feedback and regulation of the local hydrological cycle and ecological environment.Under the background of global warming,the study of the spatiotemporal dynamics of snow cover has become one of the hot topics in the cryosphere research.MODIS snow products,with the advantages of spatial resolution of about 500 meters,high temporal resolution and good production team,have become an important data source for the study of large-scale snow cover.Therefore,in this study,the MODIS daily snow cover datasets(i.e.MOD10A1 \ MYD10A1)in 2002-2016 were selected as the data source,and the Amur River Basin was taken as the study area.Firstly,we improved the original cloud removal algorithm and developed a continuous six-step cloud removal algorithm.Secondly,a daily cloudless snow cover data set in the Amur River Basin was produced with our methods.Thirdly,some snow accumulation parameters including snow cover rate(SCR),snow cover days(SCD),snow accumulation parameters(SCS)and snow melting end days(SCM)were extracted based on the data set to analyze the temporal and spatial dynamics of snow cover in the Amur River Basin.Finally,we combined the meteorological data to explore the correlation between the SCS and SCD with climate factors.Our result would provide an effective reference for climate change research,disaster prevention,and social and economic development in the Amur River Basin.The main conclusions of this paper are as follows:1)Based on our improved continuous six-step cloud removal algorithm,the daily cloudless snow cover data set reaches an overall accuracy of more than 90%,and the snow classification has an accuracy of more than 82%,and the F value is more than 83%.The overall accuracy of cloud pixel reclassification is 89.39%,the snow classification accuracy is 83.27%,and the land classification accuracy is 95.51%.2)The yearly distribution characteristic of snow cover in the Amur River Basin had a "single peak".Within a year,the highest snow cover rate occurred in January,accounting for about 85% of the basin area,and the lowest was in July,accounting for about 5%.The yearly distribution of snow cover also showed a significant seasonal difference and the annual average snow cover rate showed a slight increasing trend during 14 years.Seasonally,the snow cover rate in spring was no obvious increase or decrease,however,it can be found a slight increase in summer and winter,a slight decrease in autumn.On the other hand,the months with higher interannual volatility of snow cover were March and April in spring,November in autumn,December and February in winter3)The spatial distribution of SCD in Amur River Basin had the characteristics of "high in the east and south,meanwhile low in the middle and north" which had a significant positive correlation with its latitude.Furthermore,the SCD also had better correlation with its elevation in the same latitude.We also found that the areas of SCD with high-value(> 180d)and low-value(<60d)all showed decreasing trend,while the area of SCD with value between 91 d and 150 d showed slight increasing trend.For the whole watershed,the area with increasing snow cover days was more than that with decreasing trend.The areas with higher elevation showed a decreasing trend,while the area with lower altitudes showed an increasing trend.4)The SCS in the Amur River Basin started from October and lasted until January of the next year.The SCM started from the beginning of March and lasts to summer.It is closely related to elevation and latitude with an obviously spatial heterogeneity.And the SCS and the SCM also showed strongly interannual volatility with no obvious linear trend.5)Abnormal changes of snow cover were closely related to the climate in study area.Seasonally,the SCR in spring had a significant negative correlation with different temperature indicators(P <0.01),and no obvious correlation with precipitation.The SCR in summer and winter had a significant positive correlation with precipitation(P <0.01),and the snow cover in autumn only had negative correlation with the maximum temperature(P <0.05).The correlations of the snow cover in different months were also inconsistent to different climatic factors.In spatial,the areas with significantly positive correlation between SCD and precipitation was 11.8%,and negative correlation areas between SCD and average temperature was 38%.Overall,the temperature has a more prominent influence on snow cover in the Amur River Basin.