干旱指标在典型草原的适用性分析

从天气、土壤、植被等角度筛选出5个在内蒙古典型草原区使用较多的干旱指标,按照其计算方法和干旱等级标准,计算了多个站点1981-2010年间生长季(4-9月)旬尺度的干旱情况,依据干旱资料验证各指标的准确性,最终确定指标适用的时空尺度。基于单站点指标的适用性分析结果,对应用较好的指标进一步做区域干旱评价的一致性分析。结果表明:在单站点的春秋季,土壤相对湿度指标最好用,降水距平百分率指标可以作为补充,但该指标在呼盟境内的鄂温克春季不可用;夏季以降水距平百分率和草地旱情指数两个指标对干旱的评价最好,但是由于草地旱情指数计算所需因子较多且复杂,在实际业务应用中应首选降水距平百分率。对降水距平百分率和相对蒸降差指标在典型草原干旱评价的一致性进一步做了分析,发现对干旱的评价存在明显的区域性。通过分区研究,在呼伦贝尔温凉半干旱牧业区降水距平百分率在夏秋季优用于相对蒸降差指标,锡林郭勒温凉半干旱牧业区对春夏季的干旱评价应优先使用降水距平百分率指标。

Applicability of drought indices for typical steppe

From the perspective of the weather,soil and vegetation,we selected five drought indices of the typical steppe of Inner Mongolia,in accordance with its calculation methods and standards,calculated the drought conditions of ten days unit of the multiple stations in growth season(4-9month) during 1981-2010,and according to the drought information verified the accuracy of each index,determined applicable drought indices in the spatial and temporal scales.Based on the results of single station application,we did further analysis on the consistency of the regional drought evaluation.The results show that in a single site in spring and autumn,relative soil moisture index is preferably used,the percentage of precipitation anomalies(Pa) be used as a supplement,but the index is unavailable in the territory of Hulunbeier league Ewenki spring.In summer,two indicators of Pa and the grass drought index are the best.However,the grass drought index is more complex factor,Pa should be preferred in the practical applications.We made further analysis about the consistency of the typical grassland drought assessment on Pa and the relative evaporation and precipitation difference,and found that drought evaluation appeared obvious regional characters.Through regional studies,it was showed in the summer and autumn Pa is prior to the relative evaporation and precipitation difference in the Hulunbeier warm and cool semi-arid pastoral areas,and also should be used the preference in the spring and summer in Xilin Gol warm and cool semi-arid pastoral areas.