Climate Change In The Major Grain Producing Counties Of Henan Province And Its Impact On Reference Crop Evapotranspiration

Reference crop evapotranspiration(ET₀)is a key factor for calculating crop water requirements and an important measure of regional water and energy balance.Studying the changing characteristics of ET₀ in the main grain production areas in Henan Province under the background of climate change is conducive to scientifically and rationally formulating irrigation quotas,guiding agricultural planting and management,and studying the impact of climate change and air pollution on ET₀ has an important role in ensuring food security in my country Important scientific significance.In this paper,the major grain producing counties of Henan province is divided into humid areas and semi-humid areas according to the average precipitation over many years.The meteorological data of 20 meteorological stations 40a(1978?2017)in the study area were used to analyze the temporal and spatial variation characteristics of various meteorological elements and ET₀ in the main grain producing areas of Henan Province and the influence of meteorological elements on ET₀,and online two-way coupling of WRF-Chem was used to study the influence of aerosol on ET₀.The main conclusions drawn are as follows:The daily average precipitation and average temperature in the major grain producing counties of Henan province showed an upward trend in the whole 40 years,while the daily temperature range,average wind speed,average pressure,sunshine hours and relative humidity all showed a downward trend;average daily precipitation The average air temperature and relative humidity all have the characteristics of high in the south and low in the north,while the daily temperature range,average air pressure and sunshine hours show the distribution characteristics of high in the north and low in the south.In addition,the average wind speed is in the north and south.The upper distribution is relatively uniform and the east-west distribution shows the difference of east-high and west-low.The Penman-Monteith method was used to estimate the daily average ET₀ of various weather stations in the major grain producing counties of Henan province,and the temporal and spatial characteristics of ET₀ were analyzed.ET₀ showed a"single-peak"change during the year,and the seasonal changes of ET₀ in humid and semi-humid areas were summer>spring>autumn>winter.The average annual ET₀ of the two regions had abrupt changes during the 1980s and 1990s;the decline of ET₀ in summer was the most obvious.Partial correlation analysis method and relative contribution rate analysis method are used to clarify the influence of various meteorological elements on ET₀.The partial correlation between all meteorological elements and ET₀has reached a very significant level(P<0.01);the partial correlation coefficients of various meteorological elements and ET₀ are different at different sites,and the average temperature,sunshine hours and average wind speed are all positive for ET₀ The average air pressure,daily temperature range,relative humidity and precipitation are all negatively regulated for ET₀.The WRF-Chem model was used to simulate aerosols and main meteorological elements in the major grain producing counties of Henan province,and the influence of aerosols on regional meteorological elements and ET₀ was analyzed qualitatively and quantitatively.The WRF-Chem model well simulates the changes of various meteorological elements in the main grain producing areas of Henan Province from May to July 2016.The degree of aerosol's influence on ET₀ is closely related to the aerosol concentration;the degree of aerosol's influence on ET₀ There are differences among regions;during the study period,the obvious changes in wind speed and relative humidity made ET_0-A play a leading role in the ET₀ changes at most stations in the main grain producing areas of Henan Province.This study divides the study into humid and semi-humid areas according to the average precipitation over many years,which is more conducive to comparative analysis.The online two-way coupling of WRF-Chem experiment is adopted to study the influence of aerosols and meteorological elements on regional ET₀ from a new perspective.It provides new ideas for the study of agricultural meteorology,especially the field of evapotranspiration.