高 原 气 象 42 卷 170 图6 中国13个干旱分区代表站干湿转换自相关系数信号检测及结果对比 ML为10年; MT为3个月; LT为1个月 Fig. 6 Detection of dry-wet transition auto-correlation coefficient signals of 13 representative stations in China. ML is 10 years; MT is 3 months and LT is 1 month