利用通用地球系统模式研究陆地干燥度

发布时间：2017-12-27 18:17

本文关键词：利用通用地球系统模式研究陆地干燥度　出处：《兰州大学》2016年博士论文　论文类型：学位论文

【摘要】：基于年际平均降水量和年际平均潜在蒸腾量比值的干燥度指数是定量测量陆地气候干燥程度的科学指标。干燥度指数越小,气候越干燥,比如沙漠地区的干燥度指数接近于零。干燥度指数还可以用来划分干旱半干旱区:小于0.05是极端干旱区,在0.05和0.2之间的是干旱区,0.2-0.5是半干旱区,0.5到0.65之间的则是湿润偏干区。定量的研究干燥度演变及其演变机制对水资源使用、陆地使用管理有重大意义。本论文在前人工作的基础上利用目前最先进的通用地球系统模式The Community Earth System Model(CESM)对比研究了中世纪暖期(950-1250),小冰期(1550-1850),当前(1950-2005)和过去一千年(850-1850)的干燥度指数,定量的分析了人类活动和自然强迫对干燥度的影响。并深入的分析了当前人为排放的二氧化碳,硫酸盐气溶胶和黑碳气溶胶对干燥度指数的影响机制。此外,本论文还评估了气候系统内部变量不确定性,模式结构不确定性以及排放清单不确定性对未来干燥度指数预报的影响。主要的结论如下:(1)由于更高的温度,中世纪暖期相对小冰期,干燥度指数降低了0.34%(相对于850-1850年)。主要是由于降水量的减少,当前时期(1950-2005年)相对于过去一千年的干燥度指数降低了1.4%(相对于850-1850年)。(2)当前排放水平的人为黑碳气溶胶每导致全球表面平均气温上升一度,全球陆地降水量就会减少0.9%,而潜在蒸腾则会增加1.0%,从而导致全球陆地平均干燥度指数降低1.9%。散射性质的人为硫酸盐气溶胶每引起全球表面平均气温下降一度,全球陆地平均降水量就会下降6.7%,同时潜在蒸腾也下降6.3%,从而导致全球陆地平均干燥度指数降低0.4%。(3)利用通用地球系统模式大集合实验(Community Earth System Model Large Ensemble)和国际耦合模式比较计划(The Phase 5 of the Coupled Model Intercomparison Project),我们发现气候系统内部变量导致的不确定性比气候模式结构不确定性导致的不确定性要小。气候气候内部变量对区域尺度的干燥度变化有显著影响。(4)使用标准的高排放目录RCP8.5(Radiative Concentration Pathways 8.5),中等程度的排放目录(RCP4.5)和固定气溶胶排放的排放目录(与RCP8.5相同但气溶胶排放固定在2005年水平),我们发现在RCP8.5场景下,全球陆地干燥度指数在2060-2080年时将会降低6.4%(相对于1985-2005年);而RCP4.5场景下,全球陆地平均干燥度指数会降低3.7%;未来人为气溶胶排放的减少并不显著影响全球陆地平均干燥度指数,但在区域尺度上,人为气溶胶对干燥度指数有重大影响。
[Abstract]:The dryness index based on the average annual average precipitation and the average annual potential transpiration ratio is a scientific index for quantitative measurement of the dry degree of land climate. The smaller the dryness index, the drier the climate, for example, the desiccation index of the desert area is close to zero. The dry degree index can also be used to divide the arid and semi-arid areas: less than 0.05 is the extreme arid area, between 0.05 and 0.2 is the arid area, the 0.2-0.5 is semi-arid area, and the 0.5 to 0.65 is the wet dry area. The quantitative study of the evolution and evolution mechanism of dryness is of great significance to the use of water resources and the management of land use. The general model of earth system is currently the most advanced The Community Earth System Model on the basis of previous work (CESM) a comparative study of the medieval warm period (950-1250), LIA (1550-1850), current (1950-2005) and over the past one thousand years (850-1850) of the aridity index, quantitative analysis of human activities and the natural force influence on the dryness. The influence mechanism of carbon dioxide, sulfate aerosol and black carbon aerosol on the dryness index is analyzed in depth. Besides, the impact of uncertainty of internal variables, uncertainty of mode structure and uncertainty of emission inventory on the prediction of future dry degree index is also evaluated in this paper. The main conclusions are as follows: (1) the dryness index was reduced by 0.34% (relative to 850-1850 years) due to higher temperature and relatively small ice age in the middle ages. Mainly due to the decrease of precipitation, the current period (1950-2005 years) has been reduced by 1.4% (relative to 850-1850 years) compared with the drying index of the past one thousand years. (2) at present, the anthropogenic black carbon aerosols of the current emission level increase once the average surface temperature of the globe rises. The global land precipitation will decrease by 0.9%, while the potential transpiration will increase by 1%, which will lead to a 1.9% reduction in the global dry land index. The anthropogenic sulfate aerosols with scattering properties once decreased the average surface temperature of the globe, and the global average precipitation decreased by 6.7%. Meanwhile, the potential transpiration decreased by 6.3%, resulting in a 0.4% decrease in the global dry land index. (3) using the general earth system model (Community Earth System, a large collection of experimental Model Large Ensemble) and the international comparison project (The Phase 5 of coupled model the Coupled Model Intercomparison Project), we found that the uncertainty of small internal variables caused by climate system uncertainty than climate model structure uncertainty caused by. The internal variables of climate and climate have a significant influence on the variation of the desiccation degree of the regional scale. (4) high emission directory using a standard RCP8.5 (Radiative Concentration Pathways 8.5), moderate (RCP4.5) emissions inventory and fixed aerosol emissions emissions inventory (same as RCP8.5 but the aerosol emissions is fixed on the level in 2005), we found in the RCP8.5 scene, the global land aridity index will decrease in the years 2060-2080 6.4% (relative to 1985-2005); and the RCP4.5 scenario, the global land average aridity index will decrease 3.7%; reduction does not significantly affect the global land average dryness index future anthropogenic aerosol emissions, but on a regional scale, anthropogenic aerosols have a significant impact on the aridity index.
【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P435

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