根据冰川地貌和地形特征、岩性、冰川沉积物的风化程度以及OSL测年结果,认为长白山地区发育两期冰川作用,即末次冰盛期和晚冰期,测年结果分别为20.0±2.1ka和11.3±1.2ka。根据平衡线（ELA）处6~8月多年平均气温（T）和年降水量（P）的关系,计算长白山现代理论雪线高度为3380±100m。通过积累区面积比率AAR（accumulation-arearatio）、冰川末端到山顶高度TSAM（the terminal to summit altitudinal）,冰川末端至分水岭平均高度Hofer（the terminal to average elevation of the catchment area）、末端至冰斗后壁比率THAR（toe-to headwall altitude ratios）、冰斗底部高程CF（cirque-floor altitudes method）、侧碛堤最大高度法MELM（maximum elevation of lateral moraines）等方法计算该区末次冰盛期雪线高度为2250~2383m,平均值2320±20m。考虑到末次冰盛期后地壳上升20m,当时雪线的实际高度为2300±20m,冰盛期的雪线降低值为1080±100m。晚冰期北坡和西坡的雪线高度分别为2490m和2440m,平均值2465m,考虑新构造运动后的雪线实际高度2454m,降低值926±100m。长白山新构造运动（LGM上升约20m,晚冰期上升约11m）在末次冰盛期以来对冰川发育的影响不明显。
气候变化是近年来全球变化研究关注的热点内容,尤其是气候异常给人类带来的灾难性损失,是山区发生灾害地貌的主导外因。对长白山松江水文站阶地剖面的粒度参数和孢粉进行分析,结合AMS14C测年数据并与历史记录相校验,重建该区的气候环境演化特点与河流沉积物的相变过程。结果显示,研究区自千年来经历了3次明显的气候波动,即800—686 a B.P.气候凉湿;686—428 a B.P.气候暖干;428 a B.P.—至今气候以凉湿为主,但有明显向温暖偏干方向发展的趋势,与近几年全球变暖相一致。剖面沉积结构显示,在几百年时间内发生三期河床波动,与气候的快速转变存在明显的对应关系,加强上游河流的水土保持工作并注意对两岸采石与就地取沙的管理。
Rainfall forecasting is becoming more and more significant and precipitation anomalies would lead to droughts and floods disasters.However,because of the complexity and non-stationary of rainfall data,it is difficult to forecast.In this paper,a novel hybrid model to forecast rainfall is developed by incorporating singular spectrum analysis (SSA) and dragonfly algorithm (DA) into support vector regression (SVR) method.Firstly,SSA is used for extracting the trend components of the hydrological data.Then,SVR is utilized to deal with the volatility and irregularity of the precipitation series.Finally,the parameter of SVR is optimized by DA.The proposed SSA-DA-SVR method is used to forecast the monthly precipitation for Songbai,Panshui,Lanma and Jiulongchi stations.To validate the efficiency of the method,four compared models,DA-SVR,SSA-GWO-SVR,SSA-PSO-SVR and SSA-CS-SVR are established.The result shows that the proposed method has the best performance among all five models,and its prediction has high precision and accuracy.
