基于交叉谱分析的气象干旱与农业干旱滞后响应研究

为解决干旱问题、实现区域的早期干旱预测,该文对山东省区域应用交叉谱方法分析气象干旱与农业干旱之间的联系。首先,选取1982-2014年的NDVI和降水量日数据进行5 d平均,采用Savitzky-Golay滤波对NDVI时间序列重建;其次,根据山东省降水量的时空特征,将1 a划分湿润期和干旱期两个阶段;最后,采用NDVI和降水量的交叉谱分析,分别计算干旱期和湿润期的NDVI-降水量滞后响应时间及植被滞后时间空间分布,并探讨影响NDVI-降水量滞后时间的主要因素。结果表明:山东省降水量时空分布不均,由西北至东南方向逐渐增高,且降水量主要分布在5-9月份,占全年总降水量的78%;湿润期的NDVI与降水量多年平均相关系数(平均值为0.58)大于干旱期(平均值为0.40);干旱期的多年平均滞后时间处于11~15.5 d,湿润期的多年平均滞后时间处于15~21.5 d,湿润期的滞后时间高于干旱期的滞后时间,且山地丘陵的滞后时间长度低于平原区;干旱年,鲁西北平原的NDVI-降水量滞后时间较短,湿润年,鲁南和鲁中山地的NDVI-降水量滞后时间较短,且发现植被响应滞后时间与降水量在年时间序列上存在滞后0.16 a的显著相关性。气象干旱与农业干旱传播时间的研究,在实现对农业干旱短期预报的基础上,反映了不同区域植被的干旱脆弱性,有助于管理者对水资源做出及时、合理的调度。

Research on the Delayed Response of Meteorological Drought and Agricultural Drought based on Cross Spectral Analysis

In order to solve the problem of drought and realize the early drought prediction in Shandong Province,we analyze the relation between meteorological drought and agricultural drought by using cross spectrum method.First,the daily data of NDVI and precipitation from 1982 to 2014 are selected for a five-day average,and the savitzky-Golay filter is used to reconstruct the NDVI time series.Secondly,according to the spatial and temporal characteristics of precipitation in Shandong Province,a year is divided into two stages:wet period and dry period.Finally,cross spectrum analysis of NDVI and precipitation is used to calculate the spatial distribution of NDVI-precipitation lag response time and vegetation lag time respectively in dry and wet periods,and the main factors affecting NDVI-precipitation lag time are discussed.The results show that the precipitation in Shandong Province is not evenly distributed in time and space,and it increases gradually from northwest to southeast.Moreover,the precipitation is mainly distributed from May to September,accounting for 78%of the total annual precipitation.The correlation coefficient between annual average precipitation and NDVI in humid period(mean 0.58)was higher than that in arid period(mean 0.40).The average multi-year lag time in the dry period was 11-15.5 days,and the average multi-year lag time in the wet period was 15-21.5 days.The lag time in the wet period was higher than that in the dry period,and the length of the lag time in the mountainous and hilly areas was lower than that in the plain area.In dry years,the lag time of NDVI-precipitation in the northwest Plain of Shandong is relatively short;in wet years,the lag time of NDVI-precipitation in the south and middle mountains of Shandong is relatively short;moreover,it is found that there is a significant correlation between vegetation response lag time and annual time series of precipitation by 0.16 years.The study on the propagation time of meteorological drought and agricultural drought reflects the drought vulnerability of vegetation in different regions on the basis of realizing the short-term forecast of agricultural drought,which is helpful for managers to make timely and reasonable scheduling of water resources.