降雨预报准确度分析及其在水稻节水灌溉决策中的应用

Analysis of Rainfall Forecast Accuracy and Its Application in Water-saving Irrigation Decision-making for Rice

针对未来降雨存在不确定性的问题,为提高降雨利用率,收集了中央气象台2011年5月31日至10月6日桂林市未来4d降雨预报值及桂林气象站实测降雨数据,分析了各等级降雨预报的准确度及其在水稻灌溉决策中的应用。结果表明,预见期1～4d无雨预报准确率最高,平均可达81.4%,小雨预报为33.7%,中雨以上较低;小雨预报平均空报率为44.1%,中雨预报为81.7%,大雨预报为57.3%;无雨预报平均漏报率为18.6%,小雨预报为22.2%,中雨预报为18.3%,大雨预报为28.6%。当预报为无雨或小雨时,如达到灌溉标准的下限则可直接按计算灌水定额实施灌溉;预报为中雨及以上量级降雨量时,应适当减少灌水定额以降低灌后遇雨形成的灌水浪费,同时需注意避免降雨空报使作物受旱减产。降雨预报具有一定的精度,在进行水稻灌溉决策时应加以利用。

In order to overcome the problem of uncertainty about future rainfall and improve the using efficiency of rainfall, the fore- casted data of National Meteorological Centre about the rainfall of the coming 4 days in Guilin city and the field-measuring data of Guilin Meteorological Centre in the period of May 31 to October 6, 2011, are collected. Also, the accuracy of rainfall forecast is ana- lyzed and its application in irrigation decision-making for rice is discussed. The results show that the average forecast accuracy for no rain is the highest, which reaches 81.4%, for light rain 33. 7% and relatively low for moderate rain and more. The average false a- larm ratio is 44. 1%, 81.7% and 57.3% for light rain, moderate rain and heavy rain, respectively. The average miss alarm ratio is 18. 6%, 22. 2%, 18. 3% and 28. 6% for no rain, light rain, moderate rain and heavy rain, respectively. If the forecast is no rain or light rain and reach the low limit of the irrigation standard, the irrigation can be conducted directly according to the calculating irriga- tion quota. While If the forecast is moderate rain or above, the irrigation quota should he reduced appropriately to cut down the water -waste risk under the condition of rain after irrigation, meanwhile, the yield reduction due to false rainfall alarm should be avoided. The rainfall forecast has a certain degree of accuracy and can be used in irrigation decision-making for rice.