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绿洲防护林缓减冰雹灾害的动力学机制

刘明虎1,张建平1,苏智1,高君亮1,赵英铭1,马迎宾1,满达2,陆占东2,王志刚1*   

  1. 1内蒙古磴口荒漠生态系统国家定位观测研究站/中国林业科学研究院沙漠林业实验中心, 内蒙古磴口 015200;2内蒙古磴口县气象局, 内蒙古磴口 015200)
  • 出版日期:2019-09-10 发布日期:2019-09-10

The kinetic mechanism of oasis shelter forest in mitigating hail disaster.

LIU Ming-hu1, ZHANG Jian-ping1, SU Zhi1, GAO Jun-liang1, ZHAO Ying-ming1, MA Ying-bin1, MAN Da2, LU Zhan-dong2, WANG Zhi-gang1*   

  1. (1National Research Station of Inner Mongolia Dengkou Desert Ecosystem/Experimental Center of Desert Forestry, Chinese Academy of Forestry, Dengkou 015200, Inner Mongolia, China; 2Weather Bureau of Dengkou County, Dengkou 015200, Inner Mongolia, China).
  • Online:2019-09-10 Published:2019-09-10

摘要: 对2016年6月13日内蒙古磴口县发生的冰雹灾害进行了实地调查,旨在从动力学机制上解释防护林的减雹机理。选取典型样地林网内、外农作物雹灾后保存率和产量进行调查,反映林网缓减雹灾的作用;利用建筑物直立外墙保温层破损随高度的变化估计雹块下落到地面附近(H=0~40 m)水平速度的变化规律;利用不同高度沙尘水平通量仪顶盖破损程度差异估计雹块下落到地面附近(H=0.5~50 m)竖直速度的变化规律。结果表明:林网内、外玉米灾后植株保存率分别为87%、24%。雹块近地面水平速度和竖直速度均随高度降低而减小,与风速廓线形态和下沉气流在近地面的截止趋势一致。防护林缓减雹灾作用的动力学机理是:防护林与雹块间存在以空气为介质的动力作用,林带阻碍近地面气流运动,遏制近地面含雹气流的下沉和辐散,雹块进入林网低风速区后接受比无林区更大的空气阻力,竖直和水平速度均显著降低,致灾能力降低。本研究为防护林的营建与减灾效益评估提供了科学依据。

关键词: 半干旱区, 茎流, 降雨, 蒸腾, 土壤含水量

Abstract: We conducted an onthespot investigation on the occurrence of hail disaster in Dengkou County, Inner Mongolia on June 13, 2016, to uncover the protection and kinetic mechanism of the desert oasis farmland shelterbelt system against hail disasters. We selected typical plots to survey yield and survival rate of crops inside and outside shelterbelt network after hail disaster. We estimated the variation of the horizontal speed of hail falling near the ground (H=0-40 m), based on the damage degree of the external wall of buildings in different height. We estimated the variation of the vertical speed of hail falling near the ground (H=0.5-50 m), based on the damage degree of the roof in dust level flux analyzer in different heights. The results showed that the survival rate of corn outside and inside the shelterbelt network plots were 24% and 87% respectively. The horizontal and vertical speed of hail decreased with decreasing height, which was consistent with the declining trend of wind speed profile and subsidence flow near the ground. The kinetic mechanism of mitigating hail disaster of shelter forest is that there is a strong kinetic effect of air which serves as a medium between the oasis shelter forest and the hail. The wind break belt is strongly resistant to the nearsurface airflow movement, which curbs the sinking and divergence of the hail airflow. After entering the low wind speed zone of the shelterbelt network, the hail blocks receive greater air resistance than those in the forestless zone, and the vertical and horizontal speed are significantly lower than that outside the shelterbelt network area, thus the ability of hail disaster is apparently reduced. Our results provide scientific basis for shelter forest construction and the assessment of their disaster reduction benefit.

Key words: semi-aridarea, sap flow, precipitation regime, transpiration, soil water content.