| The frequent occurrence of extreme weather events and the turbulence of the international situation have led to the instability of global food production,and the food security problem is facing unprecedented pressure.In order to improve the food supply rate and ensure food security,cultivated land protection has become the most important task in China’s land resource management.The implementation of the strategy of "storing grain in the land and technology" requires more extensive attention to the regional influencing factors of cultivated land.The productivity of cultivated land is determined by the combination of water and heat,and climate is one of the most important natural factors affecting the use of cultivated land.The impact of snow cover in Eurasia on China’s climate has been systematically recognized,while the research on the impact of snow cover in eastern Eurasia(Siberia)on the climate in Northeast China is relatively scarce.Northeast China is the main grain producing area in China and one of the most sensitive regions to global climate change.Drought,flood and low temperature disasters are the main meteorological disasters affecting grain production in Northeast China.The frequent occurrence of extreme weather events also increases the instability of the Northeast cultivated land use system.If we can forecast and monitor the soil moisture and temperature in Northeast China in advance,and seize the favorable opportunity to carry out spring cultivation and spring sowing and spring planting,It can effectively alleviate the drought,reduce the impact of low temperature disasters,increase grain output and ensure grain production and income.Aiming at the problem of regional climate change caused by land use and land cover change under the background of global warming,this paper takes the Northeast China,which is the most sensitive to global warming in the middle latitude of China,as the research area,and comprehensively uses a variety of data to study the correlation between the snow cover area in Siberia in spring and the climate and crop growth in Northeast China;The correlation between spring snow water equivalent in Siberia and temperature in Northeast China is analyzed;A mesoscale numerical model WRF is used to simulate the effect of spring snow water equivalent change in Siberia on the temperature in Northeast China.The main conclusions of this paper include the following points:(1)In different growing periods,the snow cover area in Siberia has different effects on the maximum and minimum temperatures in different regions of Northeast China.At the beginning of the growing season(May and June),there is a significant negative correlation between the minimum air temperature in the north of Northeast China and the snow cover area in Siberia in spring.In the peak growing season(July and August),the highest temperature in almost the whole northeast region is significantly negatively correlated with the snow cover area of Siberia,while for the lowest temperature,only the northern northeast region is significantly negatively correlated with the snow cover area of Siberia.In the early growing season,for the Northeast ecosystem,the minimum temperature is negatively correlated with the snow cover area in Siberia in spring,while in the peak growing season,both the maximum temperature and the minimum temperature are negatively correlated with the snow cover area in Siberia in spring.The significant negative correlation between the minimum temperature at the beginning of the growing season and the snow cover area in Siberia in spring is of great significance for the spring preparation,cultivation and farmland management in Northeast China.(2)In different climatic regions and growing periods,the snow cover area in Siberia in spring has different effects on the precipitation in Northeast China.In the Northeast Songnen Plain,the main grain producing area in Northeast China,the precipitation from May to June is negatively correlated with the snow cover area in Siberia in spring.In the peak growing season,the precipitation in Northeast China except the north of Daxing’an Mountains is positively correlated with the snow cover area in Siberia in spring,that is,the larger the snow cover area in Siberia in spring,the greater the precipitation in Northeast China from July to August.For the Northeast farmland system,in the early growing season,the precipitation is negatively correlated with the snow cover area in Siberia in spring.In the peak growing season,the precipitation shows the opposite response and is positively correlated with the snow cover area in Siberia in spring.(3)At the beginning of the growing season,the normalized vegetation index(NDVI)in the north of Northeast China was negatively correlated with the snow cover area in Siberia in spring.In the peak growing season,the NDVI of most areas in Northeast China is negatively correlated with the snow cover area in Siberia in spring,and the NDVI of farmland ecosystem in Northeast China is also negatively correlated with the snow cover area in Siberia in spring.The change of snow cover area in Siberia in spring is an important driving factor affecting crop growth by changing the climate in Northeast China.(4)At the beginning of the growing season,the stations with significant correlation between the northeast region and Siberia as a whole,Chita Prefecture and the Republic of Buryat in spring are mainly located in the middle of the northeast,29 stations in the main grain producing areas in the Northeast are selected.The conclusions of the correlation analysis can serve these main grain producing areas,including Siping City,Songyuan City,Baicheng City,Changchun City,Harbin City Daqing City,Suihua City,Heihe City and Qiqihar City have a coverage of 65 cities and counties.Using the correlation between the spring snow water equivalent of Chita Prefecture and the Republic of Buryat and the temperature of 29 meteorological stations in the main grain producing areas to predict the temperature can effectively reduce the workload of calculation,more efficiently and quickly predict the trend of the temperature in the early growing season in these main grain producing areas,and serve the spring farming production.(5)The optimized parameterization scheme is selected,the era5 data with high accuracy is used as the climate field data,and the WRF model(v4.2)is used to simulate the impact of snow water equivalent change in the selected study area of Siberia on the temperature in Northeast China.Under the control experiment scenario,WRF can accurately simulate the spatial distribution of the temperature in Northeast China from March to August.The distribution of the highest and lowest temperature stations is consistent with the actual situation.The accuracy verification results show that the disparity between the simulated temperature and the measured station temperature in each month from March to August is very small.The comparison results of control experiment and sensitivity experiment show that when the snow water equivalent in the study area increases,the simulated temperature difference of almost all meteorological stations in Northeast China is positive in March and April,which is consistent with the correlation analysis results of measured stations.In May and June,the simulated temperature difference of most meteorological stations in the middle and west of the northeast is consistent with the correlation analysis results of the measured stations.When WRF simulates the effect of snow water equivalent change on Northeast air temperature in the selected study area,the effect of spring air temperature simulation is better than that in summer.The method of simulating temperature using the WRF model in this paper can serve the spring ploughing production in Northeast China. |
