The Forecast For Soil Moisture Based On Soil-water Balance Model In Summer Maize

It is well know that the water resource is very limited in North China,the climate is complex,the frequent occurrence of drought is a serious restraining factors which affcets the economic development and agricultural production.Consequently,more attention is paid to the occurrence and evolution of drought.to analyze the characteristics of regional drought and dry wet cycles.Forecasting soil moisture by weather forecast system is based on soil moisture simulation in the growth stages of maize.Knowning the regional drought developing rules is the main contents of drought-resisting.This article studies on soil moisture simulation and forecast.The research results are listed as follows.（1）The regional drought development law analysis in ZhengzhouThis paper summarizes the drought definition,classification and representative indices.Standardization Precipitation Index（SPI）was selected to analysis the characteristics of drought and dry wet cycles in Zhengzhou.The SPI with different time scales is obtained the following results:1)To analysis drought evolution law in the growth stages of maize.2)The drought and flood has its definite periodicity in Zhengzhou.At present,it is in a dry–wet phase alternate period and vulnerable to drought hazard in Zhengzhou.（2）Soil moisture simulation based on different modelsIn order to study the variation regularity of soil moisture during the growth stages of maize.The soil water balance model was selected to simulate soil moisture transformation.The soil-water balance model needs to be refined baesd on the actual situation of Zhengzhou area.The results are as follows:1)According to the complex calculations of reference crop evapotranspiration（ET₀）in the soil-water balance model,BP network is used for reference crop evapotranspiration,which is similar to the results from P-M formula.2)The soil-water balance model was calculated by BP simulation and the P-M.It shows that the BP simulation gets a smilar result of soil moisture simulation to the P-M.The usage of ET₀ based BP network for the soil moisture simulation will be feasible when the information is incomplete.（3）The soil moisture predictionSoil moisture is an important index for agricultural assessment.It will provide more dependable information if known soil moisture the before drougnt occurs.We find that the characteristics of higher prediction of on rain and light rain of T213 forecasting system based on analyzing of rainfall data availability.Based on the characteristics of higher prediction precision of light drought of T213,the precipitation forecasting information of T213 is used for soil moisture forecasting.Comparing the predicted value with the measured value,the qualified rate was over 90%.In order to provide more dependable information for drought-resisting.the forecasting result is translated into drought grade.It shows that theprediction percnt is high except some prediction of drought grade is too large.