| This paper takes Northeast China as the research area,based on the data of China snow depth long-term sequence data and ERA-Interim soil moisture,and uses Matlab as a platform to analyze the influence of maximum snow depth and accumulated snow depth on soil moisture in spring.Concluded as follow:(1)The surface soil moisture in Northeast China changed in the same period in March,April,and spring,and the soil moisture showed a significant decrease(P<0.01).That is,in the past 30 years,the surface soil in Northeast China was extremely dry,and the drying rate was At 0.020%/a,the surface soil moisture in May showed no significant decrease(P>0.05),and the reduction rate was 0.012%/a,indicating that the surface soil moisture drying trend in Northeast China was not obvious in May.And showing obvious characteristics of interannual variation,the rate of soil moisture reduction in the 80-year representative layer is-0.448%/a,which increased in the 1990 s and 00 s,with rates of 0.001%/a and 0.003%/a,respectively.The surface soil moisture was the fastest in the 1980 s.By the 1990 s,the drying rate gradually slowed down.In the 00 s,the soil moisture drying rate accelerated again.From the spatial distribution point of view,the spatial distribution of surface soil moisture in the northeastern region from 1980 to 2012 is generally characterized by low in the central and western regions and high in other regions.Among them,the soil moisture in Daxing'anling area,Xiaoxing'anling area,Changbai Mountain area and Sanjiang Plain area is high,and the soil moisture in Songnen Plain and Liaohe Plain is low.From the perspective of spatial change,the Songnen Plain and Xiaoxing'anling areas showed a significant drying trend,passing the significance test of 0.05.The soil moisture shows the characteristics of high forest land and low cultivated land.This is because forest land is mostly distributed in high altitude areas,and the cultivated land is mostly distributed in the lower elevation plains.The low altitude is relatively high,the evaporation capacity is strong,and the soil moisture evaporates relatively quickly,resulting in relatively low soil moisture and high altitude.(2)The changes of soil moisture in the middle layer of Northeast China were consistent in March,April and spring,all showed a significant downward trend(P<0.05),and the decline rates were 0.035%/a,0.027% and 0.023%/a.It indicated thatthe middle layer soil in the northeastern region was significantly dry in March,April and spring.The soil moisture in the middle layer did not decrease significantly in May(P>0.05),and the reduction rate was 0.0007%/a,indicating that the soil moisture in the middle layer of spring in May was changed.The dry trend is not obvious and is consistent with the change in surface soil moisture.And there are obvious characteristics of interannual variation.From the interannual variation in spring,the rate of soil moisture reduction in the 80-year representative layer is 0.032%/a,and the reduction rates in the 1990 s and 00 s are 0.007%/a and 0.077%/a,respectively.In the northeastern part of the spring,the soil moisture in the middle layer was fast in the1980 s.By the 1990 s,the drying rate gradually slowed down.In the 00 s,the soil moisture drying rate accelerated again,and the drying rate in the 1980 s was consistent with the surface layer change.From the perspective of spatial distribution,the spatial distribution is consistent with the surface soil moisture,and the overall characteristics are low in the Midwest and high in other regions.The high soil moisture content areas are Daxinganling area,Xiaoxing'anling area,Changbai Mountain area and Sanjiang Plain area.The low soil moisture area is Songnen Plain and Liaohe Plain.(3)There is no significant decrease in the maximum snow cover depth change in the northeast region in the past 35 years.It has not passed the 0.05 probability level test.The maximum snow depth is 14.556 cm,which is higher than the average for 16 years.The other 17 years are in Below the average.The overall spatial variation is characterized by the distribution of the east to the west and the north to the south.Among them,the maximum snow depth in the Songnen Plain and Liaohe Plain is low,and the maximum snow depth in the Daxinganling,Xiaoxing'anling and Changbai Mountains areas is high.(4)From 1980 to 2012,the accumulated snow depth in the northeastern region showed no significant downward trend,and did not pass the 0.05 probability level test.The maximum snow depth is 1297.172 cm,a total of 17 years higher than the average,and the other 16 years are below the average.Compared with 1980,the accumulated snow accumulation in 2012 decreased by 355.677 cm,indicating that the annual average snow depth in Northeast China has changed greatly and is unstable over the past 30 years.The overall spatial variation is consistent with the characteristics of the western and central parts of the Northeast,that is,the accumulated snow depth is low.The accumulated snow depth in the Daxinganling and Xiaoxing'anling areas is high,and the accumulated snow depth in the Songnen Plain and Liaohe Plain is low and maximum.The snow is consistent.(5)The time correlation between the maximum snow depth in Northeast China and the surface soil and mid-level soil moisture in the period from 1980 to 2012.There is a significant positive correlation between the two,that is,the greater the maximum snow depth,the greater the surface soil and middle soil moisture in spring.The soil is damp.There was no significant negative correlation between the maximum snow depth and the spring surface soil moisture during the 1980 s and 1990 s.After entering the 21 st century,there was a significant positive correlation between the two,with a correlation coefficient of 0.513.80 s and 00 s There was no significant negative correlation between the maximum snow depth and the mid-level soil moisture during the spring period,and there was a significant positive correlation between the two during the 1990 s.(6)Among the spatial correlations between surface soil moisture and maximum snow depth in spring in Northeast China,the area with positive correlation has a large proportion of the northeast area,and the surface soil moisture in the northeastern central part and Daxinganling area is positively correlated with the maximum snow depth.Larger,with the increase of the maximum depth of snow,the surface soil moisture gradually increases;the area with negative correlation between the two accounts for a small area in the northeast,mainly in the Songnen Plain and Sanjiang Plain,with a negative correlation.With the increase in the depth of the maximum snow depth,the surface soil moisture gradually decreases.Among the spring soil moisture and maximum snow depth in Northeast China,there is a significant positive correlation between the central part of Northeast China,the majority of Heilongjiang Province and the Daxinganling area.The Songnen Plain area has a negative correlation,ie with the largest As the depth of snow increases,the soil moisture in the middle layer gradually decreases,and the change in surface soil moisture is more significant.(7)The correlation between the accumulated snow depth in Northeast China and the surface soil and mid-level soil moisture in the period from 1980 to 2012.There is a positive correlation between the two in terms of time,that is,the greater the accumulated snow depth,the greater the soil moisture in the surface layer in spring,the more soil wet.The accumulated snow depth and the spring surface and middle soil moisture have positive correlations during the various periods,indicating that with theincrease of accumulated snow depth,the surface soil and middle soil moisture in spring becomes larger,that is,the soil becomes wet,especially after entering the 21 st century.The cumulative snow depth is significantly positively correlated with the spring surface soil moisture.(8)The relationship between accumulated snow depth and surface soil moisture is positively correlated with the central part of Daxing'anling,the Liaoyuan area at the junction of Jilin and Liaoning,Chaoyang City and Tieling in Liaoning Province,and the negative correlation between the Sanjiang Plain,Changbai Mountain and northern Songnen Plain.Sexual space characteristics.The surface soil moisture in March was related to the accumulated snow depth.Only the central part of Xiaoxing'anling passed the 0.05 significant test,which was positively correlated with the central part of Xiaoxing'anling and negatively correlated with the Sanjiang Plain and Changbai Mountain.The correlation in April was the same as that in March,and both were positively correlated with the central part of Xiaoxing'anling.However,the overall correlation between surface soil moisture and maximum snow depth decreased.The positive correlation in May accounted for a large proportion,and there was a positive correlation between the northeastern part of the Northeast,the Xiaoxing'anling central area,and the Songnen Plain area.That is,the soil moisture gradually increased with the increase of accumulated snow volume;the Changbai Mountain area and the Liaoheping principle showed a negative correlation..(9)The relationship between accumulated snow depth and middle soil moisture is not significant,which is positively correlated with the central part of Daxing'anling,the Liaoyuan area at the junction of Jilin and Liaoning,Chaoyang City and Tieling in Liaoning Province,and the negative in Sanjiang Plain,Changbai Mountain and northern Songnen Plain.Correlation spatial characteristics of correlations.In mid-March,the soil moisture in the middle layer was negatively correlated with the accumulated snow depth,but it was not significant.In April,the correlation between soil moisture and accumulated snow depth in the middle layer was only positively correlated with the Liaoyuan area at the junction of Liaoning and Liaoning,Jinzhou and Chaoyang in Liaoning Province.Both the plain and the Sanjiang Plain are negatively correlated.Among the correlations between soil moisture and accumulated snow depth,the positive correlation accounted for less.Compared with the surface soil moisture in the same period,the soil moisture in the middle layer showed a significant drying trend,and the overall drying trend was obvious. |
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