Accuracy assessment of rainfall forecast and analysis on water-saving irrigation strategies during rice growing seasons in South China
LUO Yufeng1,2, MA Zhen1, LYU Xinwei3, GUO Longzhu1, CUI Yuanlai2, XIANG Zhao2
1.State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 2.State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, Hubei 430072, China; 3. School of Software Engineering, University of Science and Technology of China, Hefei, Anhui 230051, China
Abstract:Increasing effective rainfall is one of strategies for saving irrigation water, unfortunately there is an uncertainty in future rainfall, thus accuracy assessment of rainfall forecast is necessary for effective rainfall use. Taking the Guanfu Plain Irrigation District as an example, we collected 7-day lead time rainfall forecast data in three seasons of early and late rice(2012—2015)from the National Meteorological Centre of China, and the observed rainfall data, then analyzed the forecast accuracy by using correct forecast rate, threat score(TS), false alarm rate(FAR), missing alarm rate(MAR)and receiver operating characteristic(ROC)curve. Furthermore, strategies for increasing effective rainfall are proposed based on the accuracy assessment. The results show that the correct forecast percentage of rain/no rain during the rice growing seasons has reached 76.3%, the MAR is lower but the FAR is higher in the early rice season than in the late rice season. The difference in TS for light rain during the early and late rice seasons is not significant; for middle and above rainfalls, however, the TS in the late season is lower than in the early season. The areas under the ROC are greater than 0.5 for all 1-7 days lead time, implying that the correct forecast percentage is higher than the FAR and all the forecasts are positive, thus the correct forecast percentage can be used in irrigation management. The correct forecast percentage is ranged from 80.1% to 88.6% in the re-greening, milk-maturing and yellow-maturing stages of early rice. Thus if a light rain or above is forecasted, then there should be no or less irrigation. The correct forecast percentage is slightly lower and ranged from 64.9% to 77.2% in the early tillering, late tillering, jointing/booting, and heading/flowering stages. Therefore, if a continuous clear day or slight rain is forecasted, then irrigation should be applied according to the crop requirement. However, if a medium or above rainfall in 2-3 days is forecasted, then irrigation amount should be reduced. Although the accuracy in the early rice season is lower than in the late rice season, the forecasted and actual rainfall events are even more in the early rice season, so that the irrigation amount can be decreased if a medium or above rainfall is forecasted. After a decision on irrigation amount is made by taking an account of rain forecast accuracy, not only natural rainfall will be utilized sufficiently but also water wasting can be avoided to achieve the water saving goal.
罗玉峰,, 马震, 吕辛未, 郭龙珠, 崔远来, 向昭. 南方水稻生育期降雨预报准确率评价及节水灌溉策略分析[J]. 排灌机械工程学报, 2016, 34(5): 430-435.
LUO Yufeng,, MA Zhen, LYU Xinwei, GUO Longzhu, CUI Yuanlai, XIANG Zhao. Accuracy assessment of rainfall forecast and analysis on water-saving irrigation strategies during rice growing seasons in South China. Journal of Drainage and Irrigation Machinery Engin, 2016, 34(5): 430-435.
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