Research On Reference Crop Evapotranspiration Prediction In Shaanxi Province Based On Temporal And Spatial Features And Integrated Learning

The research reference crop evapotranspiration ET0 can estimate the agricultural water demand of regional crops,and provide guidance for the implementation of water-saving irrigation projects and irrigation decision-making in the study area,and then rational and effective management and allocation of regional water resources.This study was based on the daily meteorological data of 32 meteorological stations in Shaanxi Province from 1990 to 2019,and then calculates the standard value of ET0 according to the FAO 56 PM formula,explores the meteorological factors and the temporal and spatial evolution of ET0,and carries out the cycle of ET0 Analyze;clarify the response of ET0 to climate change;at the same time,in order to make high-precision prediction of ET0 in the case of incomplete meteorological data,use different combinations of meteorological elements as input parameters to build an ELM integrated model based on different activation functions(DAF-ELM model)Perform predictive simulation on ET0 and screen the optimal predictive model.conclusion as below:(1)In addition to the average temperature in Shaanxi Province,the average wind speed,sunshine hours and relative humidity all show a decreasing trend.In addition to wind speed,the average temperature,sunshine hours and relative humidity showed a "high summer and low winter" trend during the year,and the wind speed was the highest in spring.The average temperature and relative humidity are high in the south and low in the north,and the wind speed and sunshine hours are gradually increasing from south to north.(2)The multi-year average ET0 in Shaanxi Province is 969 mm,showing an upward trend.The ET0 in southern Shaanxi and Central Shaanxi shows a decreasing trend,while the ET0 in northern Shaanxi shows an increase;the seasonal and cyclical changes of ET0 in all regions are consistent,and both show a decreasing trend.The rule is summer>spring>autumn>winter;the main period scale is about 28 years;the ET0 of Shaanxi Province is generally low in the south and high in the north.(3)Except for the negative correlation between relative humidity and ET0,other meteorological factors are positively correlated with ET0;average temperature and sunshine hours are the main influencing factors of ET0 in Shaanxi Province;average temperature,sunshine hours,and relative humidity sensitivity coefficients all show south The distribution characteristics of high north and low.(4)The DAF-ELM integrated model proposed in this study can well reflect the complex nonlinear mathematical relationship between meteorological factors and ET0,and the simulation performance is better;the DAF-ELM8 model based on the highest and lowest temperature has high simulation performance Based on the Hargreaves model;the simulation performance of the DAF-ELM5 model based on the highest and lowest temperature and radiation is significantly better than the Irmark-Allen model and the Makkink model.The DAF-ELM5 model based on the highest and lowest temperature and radiation can be used as the ET0 prediction simulation model of Shaanxi Province in the absence of meteorological data.The DAF-ELM5 model based on the highest and lowest temperature and radiation can be selected with high accuracy and greater portability.