干旱气象

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干旱区荒漠草原过渡带快速变化的陆面过程特征观测分析

杨扬1左洪超2王丽娟1杨启东3杨彦龙2   

  1. 1.中国气象局兰州干旱气象研究所,甘肃省(中国气象局)干旱气候变化与减灾重点实验室,甘肃兰州730020;2.兰州大学大气科学学院,甘肃兰州730000; 3.云南大学大气科学系,云南昆明650091
  • 出版日期:2015-06-30 发布日期:2015-06-30
  • 作者简介:杨扬(1988-),女,甘肃民乐人,硕士,主要从事大气物理学与大气环境研究. E-mail: yangmeng07.happy@163.com
  • 基金资助:

    兰州干旱气象研究所科研启动项目(KYS2014SSKY01)资助

Transient Change Characteristics of Land Surface Process over Desert-steppe Transitional Zone in Arid Regions

YANG Yang1ZUO Hongchao2, WANG Lijuan1,YANG Qidong3, YANG Yanlong2   

  1. 1.Gansu Key Laboratory of Arid Climatic Change and Reducing Disaster of CMA,Institute of Arid Meteorology, China Meteorological Administration, Lanzhou730020,China;2.College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China;3.Department of Atmospheric Science, Yunnan University, Kunming 650091, China
  • Online:2015-06-30 Published:2015-06-30

摘要:

干旱区荒漠草原过渡带下垫面受降水影响而变化,在短期内由沙漠转化为草地,因而其陆面过程特征快速变化十分显著,可能对区域天气或气候造成一定影响。本文利用2012年7~9月在腾格里沙漠南缘的荒漠草原过渡带开展的 “微气象蒸发观测实验” 的观测资料,通过分析强降水前后土壤温度、含水量、辐射及湍流通量,研究快速变化的陆面过程特征。结果表明:40 cm以上的浅层土壤温度在降水后降低,随着降水辐射效应的消失,土壤温度升高;而深层的土壤温度变化较小。土壤含水量对降水有明显的响应, 20 cm以上的浅层土壤含水量迅速增大,而后缓慢减小;30、40 cm的土壤含水量先增大后迅速下降。7、8月的净辐射变化不大,在-50~450 W·m-2间变化。降水发生后,反射辐射和地表长波辐射较干旱荒漠有所降低,2~3 d后又恢复到干旱荒漠的量级。地表反照率在降水后先降后升,荒漠草地的地表反照率日均值较大,与地表含水量、太阳高度角及植被生长参数密切相关。感热和潜热在降水前后变化显著,潜热增大而后减小,感热减小而后增大,干旱荒漠地表能量传输以感热通量为主,强降水发生后,潜热通量占主导地位,而后由于蒸散发使土壤含水量减小,潜热的主导地位逐渐被感热代替。

关键词: 荒漠草原过渡带, 快速变化, 陆面过程

Abstract:

The underlying surface of the desert-steppe transitional zone in arid areas can change from desert into meadow in short time because of precipitation, and the transient change of land-surface process characteristics is very significant, which may cause some impact on regional weather or climate. In this paper, based on the observed data of “Microclimate and Evaporation Experiment” carried through in the desert-steppe transitional zone in the southern edge of the Tengger Desert from July to September of 2012, the soil temperature, water content, surface albedo and energy fluxes were analyzed to study the transient change feature of land surface process. The results show that soil temperature of shallow soil layers above 40 cm decreased after  precipitation firstly, then it increased with the disappearance of radiation effects of precipitation, while soil temperature of 80 and 120 cm changed little. Soil water content responded to rainfall obviously, soil water content of shallow soil layers above 20 cm increased rapidly, then decreased slowly, and soil water content of 30, 40 cm decreased rapidly after the increase. The net radiation varied from -50 W·m-2 to 450 W·m-2, which had a little change in July and August. After precipitation, the upward shortwave and longwave radiation decreased  compared to those in the arid desert, and in two or three days, they returned to the magnitude of the arid desert. Surface albedo firstly decreased and then increased after rainfall. Albedo was higher over desert meadow surface, and it was closely associated with surface water content, sun elevation angle and vegetation growth parameters. The sensible and latent heat flux had significant change after precipitation, latent heat flux increased firstly and then decreased, while sensible heat flux decreased firstly and then increased. Over the dry desert surface, the sensible heat flux was dominant, but after rainfall, the latent heat flux was dominant after rainfall, then the dominance of latent heat flux was gradually replaced by sensible heat flux because of evapotranspiration and reduced soil water content.

Key words: desert-steppe transitional zone, transient change, land surface process

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