重庆大气降水中氢氧同位素变化及与ENSO事件的响应机制探究

发布时间：2018-07-12 08:21

本文选题：δ~(18)O + 大气降水　；参考：《西南大学》2017年硕士论文

【摘要】：目前全球气候与环境变化及其应对措施已经逐渐变为全球瞩目的重大社会问题,联合国政府间的气候变化专委会第五次评价(IPCC-AR5)第一工作组报告指出,全球气候系统变暖已经毋庸置疑,在北半球地区的过去1400年中,最近30年的气温可能达到最暖。在气候变暖影响下,大气环流背景正出现一系列耦合性变化,同时体现在气候系统的变化还有:温室气体排放增多、温度升高、积雪融化、海平面上升、全球水体循环变化、极端气候事件和极端冷暖事件增多等方面,均已深刻危及人类生存和发展。厄尔尼诺-南方涛动现象(ENSO)是影响赤道地区气候环境年际变化的主导因素,并且对全球气候及环境变化具有重要的影响。作为记录和重建古气候变化的重要示踪信息——稳定同位素信息,具有携带信息体种类丰富、受噪音干扰小、对气候和环境变化响应敏感等特点而受到众多学者的广泛关注。通过不同尺度现代大气降水数据的持续监测,解译区域降水同位素变化特征,追踪水汽来源及响应大尺度环流变化,可以完善全球及区域尺度大气降水稳定同位素信息库。更好地为全球气候环境变化背景下,人类生存与社会发展过程中如何应对极端气候事件的影响提供科学的理论基础和决策依据,为水文学和古气候学领域研究和发展奠定了实践基础。本研究以重庆市西南大学为监测点,以降水中稳定氢氧同位素为主要监测对象,对研究区大气场降水进行了15个月(2015年4月~2016年9月)的现代指标连续监测,并于实验室分析测试大气降水中稳定氢氧同位素信息数据,并结合中国气象台(China Meteorological Observatory)北碚气象站相关气象数据和美国国家海洋和大气管理局NOAA(National Oceanic and Atmosphereic Administration)提供的NCEP(National Centers for Environmental Prediction)/NCAR(National Center for Atmospheric Research)逐日全球再分析数据资料,分析了氧同位素季节变化特征和环境效应及大尺度大气环流特征,并对重庆地区场降水中氢氧同位素响应ENSO事件的机制进行了初步论证和探讨。结合现代大气场降水监测数据,探讨研究区大气场降水中δ~(18)O变化特征响应大气环流的气候意义。研究发现,重庆降水中δ~(18)O值的变化范围是-13.11‰~1.81‰,δD值变化范围是-96.31‰~28.70‰,δ~(18)O、δD、d-excess值季节性变化显著,夏低冬高。研究时段,重庆地区大气降水线方程为δD=8.25δ~(18)O+12.23,(R2=0.98,n=129),斜率和截距与全球大气降水线差别不大。根据夏季风活动将降水样品细分为夏半年组和冬半年组,得出夏半年δ~(18)O-δD的线性方程为:δD=8.28δ~(18)O+12.15,(R2=0.98,n=99)和冬半年δ~(18)O-δD的相关关系:δD=7.28δ~(18)O+10.05,(R2=0.90,n=30),探讨季节尺度下水汽来源差异对斜率和截距的影响。又依据降水量(P)的大小将样品细分4组后分别分析线性回归方程,得到的斜率和截距基本上随着降水量的增加而升高,斜率从7.99(P≤5)增至8.65(10P≤25),相应的截距从10.57升至16.16,可能主要是由于降水量多与少导致的云下二次蒸发程度不同,从而引起的同位素不平衡分馏差异。通过降水中稳定同位素与研究区气象要素线性相关关系分析,全年降水中δ~(18)O与降水量呈现出微弱的反相关关系:δ~(18)O=-0.06P-4.19,(R2=0.12,n=129,P0.001);δ~(18)O与温度相关性较弱并且为负相关:δ~(18)O=-0.28T+1.12,(R2=0.08,n=129,P0.001),季节尺度分别回归得到夏半年和冬半年降水量效应和温度效应也不十分显著,可能是大气环流运动在某种程度上掩盖了季风区的温度和降水量效应。通过计算水汽通量和水汽通量散度模拟矢量水汽输送场,分析大尺度环流模式中ENSO事件联系下,热带辐合带ITCZ对夏半年降水中δ~(18)O变化的可能影响,根据研究区2015年和2016年夏半年大气降水中δ~(18)O的相似变化特征,可把夏半年分为五个阶段分析,第一阶段:五月和六月初,δ~(18)O维持较高值;第二阶段:δ~(18)O值开始逐渐下降,一般在六月中旬;第三阶段:δ~(18)O值是夏半年的最低值,并且持续偏低;第四阶段:自八月末开始,δ~(18)O值开始呈攀高趋势,出现第二次峰值;第五阶段,δ~(18)O值开始下降,并呈波动偏低状态。分析发现,对比水汽矢量输送场及降水中δ~(18)O值特征性的变化,与ITCZ对流活动的位置在南海和低纬度西太平洋、孟加拉湾等地变化以及强度变化密切相关。运用逐月风场资料模拟矢量风场,结合HYSPLIT轨迹模型,结果表明,夏半年水汽来源是低纬度的阿拉伯海、孟加拉湾和南海,使得夏季降水中稳定同位素值偏低;冬半年水汽来源是蒙古-西伯利亚高原以及局地水分循环,降水中δ~(18)O呈现高值。研究区降水中δ~(18)O变化显著响应于2015/2016ENSO时期,2015年El Ni?o事件夏半年降水中δ~(18)O降水加权平均值为-7.05‰,2016年La Ni?a事件夏半年降水中δ~(18)O为-6.29‰,2015年降水加权平均值显著偏负。根据夏季风影响期间阶段对比,第3~5阶段为El Ni?o和La Ni?a事件特征显著时期,2015年和2016年降水中δ~(18)O分别是-9.00‰和-6.88‰。2015年5~9月为El Ni?o盛期,同时,El Ni?o事件影响下2015夏半年的d平均值为13.4‰,显著高于2014年和2016年同期平均值。结果表明研究区在El Ni?o时期及其衰减期,2015年夏半年样品统计降水量10~(18).8mm,且来自近源的水汽比例高,使得降水同位素值偏负;在La Ni?a时期,2016年夏半年样品数据总降水量646mm,加之来自远源的水汽比例高,降水同位素值较高,研究区大气降水稳定同位素变化特征记录了此次ENSO事件的转换。
[Abstract]:At present, global climate and environmental changes and their responses have gradually become a major social problem worldwide. The United Nations Intergovernmental Panel on climate change fifth assessment (IPCC-AR5) first working group report pointed out that global warming has no doubt, in the northern hemisphere in the past 1400, the temperature of the last 30 years Under the influence of climate warming, there is a series of coupling changes in the atmospheric circulation background, as well as the changes in the climate system, as well as the increase in greenhouse gas emissions, the increase of temperature, the melting of the snow, the rise of the sea level, the change of the global water cycle, the increase of extreme climate events and the increase of extreme cold and warm events. The El Nino Southern Oscillation (ENSO) is the dominant factor affecting the climate and environment changes in the equatorial region, and has an important influence on the global climate and environmental changes. As an important tracer information for recording and rebuilding the paleoclimate change, the stable isotope information has a rich variety of information. Rich, less noisy and sensitive to climate and environmental changes, many scholars have received extensive attention. Through continuous monitoring of modern atmospheric precipitation data of different scales, the characteristics of precipitation isotopes, tracing water sources and responding to large scale circulation changes, can improve the global and regional atmospheric precipitation. Stable isotopic information base provides a scientific basis and decision basis for how to cope with the influence of extreme climate events in the process of human survival and social development in the context of global climate and environment change, and lays a solid foundation for the research and development of hydrology and paleoclimatology. The research is based on the Southwestern University in Chongqing. Taking the stable hydrogen and oxygen isotopes in the precipitation as the main monitoring object, the precipitation of the large gas field in the study area was continuously monitored for 15 months (April 2015 ~2016 September), and the stable hydrogen and oxygen isotopic data in the atmospheric precipitation were analyzed and tested in the laboratory, and the China Meteorological Observatory (China Meteorological Observatory) Beibei was combined in the laboratory. The weather station related meteorological data and the daily global reanalysis data of the NCEP (National Centers for Environmental Prediction) provided by the National Oceanic and Atmospheric Administration of the National Oceanic and Atmospheric Administration of NOAA (National Centers for Environmental Prediction) analyzed the seasonal variations in oxygen isotopes. A preliminary demonstration and discussion of the mechanism of hydrogen and oxygen isotopes responding to ENSO events in the field precipitation in Chongqing area is preliminarily demonstrated and discussed. The climatic significance of the variation of delta ~ (18) O variation in the precipitation of the study area is discussed in the light of the precipitation monitoring data of the modern large gas field. The variation range of the value of delta ~ (18) O in water is -13.11 per 1000 ~1.81 per 1000. The variation range of delta D value is -96.31 per 1000 ~28.70 per 1000, delta ~ (18) O, Delta D, and d-excess seasonal variation is significant, and the summer low winter is high. The atmospheric water line equation in Chongqing area is delta D=8.25 delta ~ (18) O+12.23, (R2), and the slope and intercept are not different from the global water line. The precipitation samples are subdivided into summer half year group and winter half year group, and the linear equation of delta ~ (18) O- Delta D in summer half year is: Delta D=8.28 delta ~ (18) O+12.15, (R2=0.98, n=99) and winter half year ~ (18) O- Delta D: Delta D=7.28 Delta ~ (18) O+10.05, (R2=0.90, n=30), and the influence of the difference of the water vapor source difference on the slope and intercept of the seasonal scale. According to the size of the precipitation (P), the sample is divided into 4 groups to analyze the linear regression equation, and the slope and intercept are basically increased with the increase of precipitation, the slope is increased from 7.99 (P < 5) to 8.65 (10P < 25), and the corresponding intercept from 10.57 to 16.16. It may be mainly due to the two evaporation degrees below the cloud caused by precipitation and less. According to the linear correlation between the stable isotopes in the precipitation and the meteorological elements in the study area, the analysis of the linear correlation between the stable isotopes in the precipitation and the meteorological elements in the study area shows that delta ~ (18) O has a weak inverse correlation with precipitation in the annual precipitation: Delta ~ (18) O=-0.06P-4.19, (R2=0.12, n=129, P0.001); delta ~ (18) O and temperature correlation are weak and negative correlation: Delta ~ (18) ) O=-0.28T+1.12, (R2=0.08, n=129, P0.001), the precipitation effect and temperature effect of summer half and winter half of the seasonal scale are not very significant. It is possible that the atmospheric circulation movement can cover up the temperature and precipitation effect in the monsoon region to some extent. Field, the possible influence of the tropical convergence zone ITCZ on the change of delta ~ (18) O in summer half year precipitation in the large scale circulation model is analyzed. According to the similar change characteristics of delta ~ (18) O in the atmospheric precipitation in the summer half year of 2015 and 2016 in the study area, the summer half year can be divided into five stages analysis, the first stage is that the delta ~ (18) O is maintained in May and early June. High value; the second stage: Delta ~ (18) O value begins to decline gradually, usually in mid June; the third stage: the value of delta ~ (18) O is the lowest in summer half year, and continues to be low; from the end of eight, the value of delta ~ (18) O begins to climb, appear second peak value; the fifth stage, delta ~ (18) O value begins to decline, and is on the low state. Analysis hair. At present, the characteristics of the delta ~ (18) O value of the water vapor vector transport field and the precipitation are closely related to the change of the ITCZ convective activity in the South China Sea and the Western Pacific, the West Pacific, the bay of Bengal and the intensity change. The vector wind field is simulated by the monthly wind field data and the HYSPLIT trajectory model is combined. The results show that the water vapor source in the summer half year is low. The Arabia sea, the bay of Bengal and the South China Sea in the latitudes make the stable isotopic values in summer precipitation low; the water vapor source is Mongolia Siberia plateau and the local water cycle in winter half year, and the precipitation of delta ~ (18) O presents high value. The change of delta ~ (18) O in precipitation in the study area is significantly responsive to the 2015/2016ENSO period, and in the summer half year precipitation of the El Ni o event in 2015. The weighted mean value of precipitation in delta ~ (18) O is -7.05 per 1000, and in the summer half year of the 2016 La Ni? A event, the delta ~ (18) O is -6.29 per 1000, and the weighted average of the precipitation in 2015 is significantly negative. According to the phase comparison of the summer monsoon period, the 3~5 stage is a significant period of El Ni? O and La 2016 events. In 2015 and 2016, delta ~ (18) is respectively per thousand and per thousand. The 5~9 month of.2015 is El Ni? O, and the D average value of the El Ni o event is 13.4 per thousand, which is significantly higher than that of 2014 and 2016. The result shows that the study area is in El Ni? O period and its attenuation period, the statistical precipitation of the samples in the summer half of 2015 (18), and the high ratio of water vapor from the near source, makes the precipitation isotopes In the period of La Ni? A, the total precipitation of the sample data in the summer half of 2016 was 646mm, and the ratio of water vapor from far source was high and the isotopic value of precipitation was high. The characteristics of stable isotopes of atmospheric precipitation in the study area recorded the transformation of the ENSO event.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P426.612;P732

【参考文献】