Comparison Of Reference Evapotranspiration Forecasting Based On Numerical Weather Forecast And Public Weather Forecast

Accurate estimation of crop water demand(ET)is the basis for reasonable irrigation scheduling and saving agricultural water and reference evapotranspiration(ET₀)is the basis for calculating ET;therefore,accurate prediction of ET₀ is of great significance for water conservation.Since ET₀ is only affected by meteorological conditions,ET₀ forecasting based on weather forecast has become the main means of forecasting ET₀.The weather forecast is divided into numerical weather forecast and public weather forecast.The former data is difficult to acquire and the data processing is complicated,while the more meteorological elements and gridding data not only meets the formula calculation requirements,but also facilitates promotion on the surface;the latter is the opposite.In China,most of the domestic ET₀ forecasting are based on public weather forecast,and the ET₀ forecasting based on numerical weather forecast has not been reported basically yet.Considering the advantages of numerical weather forecast and the emergence of mature numerical weather forecast products in China,this paper attempts to use it for ET₀ forecasting in China,so as to explore the application of numerical weather forecast and public weather forecast in different climate regions and seasons in China and to guide irrigation work.In this paper,we selected 31 meteorological stations distributed in four major climate zones in China.ET₀ forecasting based on numerical weather forecast and public weather forecast are explored(ET_0N,ET_0P).The forecasting accuracy of ET_0N and ET_0P is compared to explore the spatial applicability and seasonal applicability of two weather forecasts in ET₀forecasting.The main conclusions are as follows:(1)In general,the forecasting accuracy of net radiation and wind speed of numerical weather forecast is higher than that of public weather forecast.The forecasting accuracy of the lowest temperature and highest temperature of numerical weather forecast is lower than that of public weather forecast.The forecasting accuracy of water vapor pressure deficit of the two weather forecasts is almost the same.The forecasting accuracy of the meteorological elements of the two weather forecasts in each climate zone is as follows:For the lowest temperature,the forecasting accuracy of the numerical weather forecast is lower than that of the public weather forecast in all four climatic zones.For the highest temperature,the forecasting accuracy of the numerical weather forecast is lower than that of the public weather forecast except for the temperate monsoon climate zone,but the highest temperature of numerical weather forecast is recommended in the high latitudes of the temperate continental climate zone(?43°N)and northeastern region in the temperate monsoon climate zone.For the net radiation,the forecasting accuracy of numerical weather forecast is higher than that of the public weather forecast except for the subtropical monsoon climate zone.For the wind speed,the forecasting accuracy of numerical weather forecast is higher than that of the public weather forecast in all four climate zones.However,in the plateau mountain climate zone,the forecasting stability of the former is lower than that of the latter.For the water vapor pressure deficit,the forecasting accuracy of numerical weather forecast is lower than that of the public weather forecast in the subtropical monsoon climate zone,and there is no difference between the forecasting accuracy of two weather forecasts in other climate zones.(2)On the whole,ET_0N is recommended in the plateau mountain climate zone and the temperate continental climate zone,and ET_0P is recommended in the temperate monsoon climate zone and the subtropical monsoon climate zone.The plateau mountain climate zone and the temperate continental climate zone mainly consist the Inner Mongolia,Xinjiang,Tibet,Qinghai and Gansu.These five provinces are large in area,while there are relatively few public weather forecast sites.ET_0P is not suitable for space promotion.However,the numerical weather forecast can solve this problem due to its high gridded data form and recommendation in these provinces.The forecasting accuracy of ET_0N is in increasing order of plateau mountain climate zone,temperate monsoon climate zone,temperate continental climate zone and subtropical monsoon climate zone.The forecasting accuracy of ET_0P is in increasing order of plateau mountain climate zone,temperate monsoon climate zone,subtropical monsoon climate zone and temperate continental climate zone.These orders are consistent with the accuracy of forecasted net radiation,indicating that net radiation dominating ET₀ forecasting.(3)For the plateau mountain climate zone,the forecasted ET₀ using numerical weather forecast is suitable for autumn and winter,and the use of public weather forecast and numerical weather forecast is according to specific needs in spring and summer(public weather forecast is suggested when ET₀ forecasting is applied in specific sites while numerical weather forecast is suggested when ET₀ is being promoted into space).For the temperate continental climate zone,the forecasted ET₀ using the public weather forecast is suitable for summer,and forecasted ET₀ using the numerical weather forecast is suitable for autumn and winter.However,the use of public weather forecast and numerical weather forecast is according to specific needs in spring.For the temperate monsoon climate zone,the forecasted ET₀ using public weather forecast is suitable for spring and summer,and forecasted ET₀using the numerical weather forecast is suitable for autumn and winter.For the subtropical monsoon climate zone,the forecasted ET₀ using the public weather forecast is selected for spring,summer and winter,and the use of public weather forecast and numerical weather forecast is according to specific needs in autumn.