兰州大学机构库 >大气科学学院
江淮流域梅雨期气候对全球气候变暖的响应
Alternative TitleResponse of Climate during the Meiyu period over Yangtze-Huai River Valley to Global Warming
吴楚樵
Thesis Advisor刘玉芝
2019-04-20
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Degree Discipline气象学
Keyword梅雨期 江淮流域 全球变暖 模式
Abstract在全球气候变暖背景下,中国江淮流域梅雨期的气候变化更加趋于复杂,为该地区气候预测增加了更多的不确定性因素。因此,研究江淮梅雨期气候对全球变暖的响应,对于认识近年来江淮梅雨的变化趋势、提高气候变化背景下的汛期预报以及制定防灾减灾政策等均有着深远意义。本文利用中国地面气温及降水日值数据集,分析了近几十年来江淮流域梅雨期的气温及降水变化;基于观测数据,评估了国际耦合模式比较计划第五阶段(CMIP5)的模式模拟结果,对未来该地区梅雨期的气候变化进行了预测,并对江淮流域梅雨期气候变化的机理进行了探讨。得到的主要结论如下:(1)观测的江淮流域梅雨期气候对全球变暖的响应随着全球气候变暖,江淮流域梅雨期气候亦发生了相应的变化。气温呈现显著的增加趋势,降水亦发生了相应调整,在较暖年降水偏多,较冷年降水偏少。总体而言,梅雨期气温呈现明显的增加趋势(+0.40°C·(10a)-1),降水亦有相应的增加(+2.06mm·(10a)-1)。就空间分布而言,江淮流域梅雨期气温主要呈现由南向北逐渐降低的空间分布特征,沿长江一带的气温普遍偏高,在江淮流域西部存在低值区。降水总体也呈现由东南向西北逐渐减少的空间分布特征,沿长江一带的降水也普遍偏多。全球变暖后,江淮流域的各站点在梅雨期的平均气温与变暖前相比总体呈一致的上升趋势,且沿长江一带变化幅度更为明显。降水变化与气温类似,除江淮周边地区西北及东南部少数站点的降水呈减少趋势、且减少幅度相对较弱外,沿长江一带的变化幅度较为明显。(2)CMIP5模式模拟江淮流域气候变化的评估及未来预测22个CMIP5模式的集合平均对江淮流域梅雨期气候的平均变化趋势的空间分布模拟效果良好,较好地再现了江淮流域梅雨期气温及降水量的气候态分布特征,使用模式对未来江淮流域的梅雨期气候进行预估具有可行性。在未来全球进一步变暖的背景下,江淮流域梅雨期平均气温升高,降水量也进一步增加。且随着温室气体排放量的增加,降水的空间分布非均匀性也更为明显。两种排放情景下江淮流域的梅雨期气温及降水量相对现代而言都呈明显的上升趋势。其中气温的增强是整体性的,分布较为均匀。RCP8.5情景下多模式集合的气温变化速率(0.45°C·(10a)-1)高于RCP4.5情景(0.23°C·(10a)-1)。至二十一世纪末期,RCP4.5情景下江淮流域梅雨期气温相对现代而言平均增温2.20°C,RCP8.5情景下增温更为显著,达4.30°C。江淮流域梅雨期降水在RCP4.5情景下多模式集合变化速率(0.72mm·(10a)-1)略高于RCP8.5情景(0.51mm·(10a)-1),在RCP8.5情景下降水的空间分布非均匀性高于RCP4.5情景。且随着时间的推移,两种排放情景下降水的空间分布非均匀性都在加剧:江淮流域南部降水减少的同时,北部降水明显增加。(3)江淮流域梅雨期气候变化的机理探讨亚洲夏季风是影响江淮流域夏季降水最主要的环流系统,驱动着南海和孟加拉湾的水汽被输送至江淮流域,对江淮流域梅雨期降水有重要影响。在偏暖年,南亚夏季风减弱,水汽被输送至长江流域,与东亚夏季风输送的水汽在江淮流域汇合,使得江淮流域水汽异常充沛、气候偏湿;反之,水汽匮乏且气候偏干。南亚高压及西风急流的强弱及位置也与江淮流域的梅雨期降水有紧密联系:在偏暖年,当南亚高压增强且副热带西风急流位置偏南、偏强时,江淮流域普遍偏涝;反之,江淮流域普遍偏干。江淮流域的水汽主要由南亚季风的西风气流纬向输送而来,在偏暖年,南亚季风的纬向输送相对较强,该年相对偏湿;反之则偏干。江淮流域梅雨期气候与赤道中东太平洋海温有较显著的正相关关系。在典型的厄尔尼诺影响年,西北太平洋存在异常的反气旋环流,将大量水汽输送至江淮流域;在典型的拉尼娜影响年,北太平洋西部海温的正异常有利于水汽交汇于江淮流域东部,使得该地区夏季降水偏多。利用CMIP5海温均匀增加的模拟结果发现,海温的均匀增加将使江淮流域梅雨期气温整体增加,且增暖趋势由西向东递减;同时,降水亦发生相应增加,降水增加幅度由东向西递减,且年际变化幅度更为显著。这意味着在全球海温升高的情况下,江淮流域梅雨期的极端降水发生频次可能增多。
Other AbstractWith the global warming, the climate over Yangtze-Huai River Valley (YHRV, 110°E–122°E, 28°N–34°N) of China tends to be more complicated, which brings more uncertain factors to the climate prediction during the Meiyu period over YHRV. Studying the response of the Meiyu period climate to global warming has a far-reaching significance for understanding the new trends of climate over YHRV, improving the flood season forecast under the new climate background and formulating disaster prevention and mitigation policies. This paper uses the Chinese surface temperature and precipitation daily dataset to analyze the temperature and precipitation changes during the Meiyu period over YHRV in recent decades, and evaluates the Coupled Model Intercomparison Project Phase 5 (CMIP5) based on the observations. The mechanism of climate change during the Meiyu period in recent decades and the relationship between climate and sea temperature during the Meiyu period over YHRV are analyzed in depth, and the related mechanism of its change is also discussed.The main conclusions obtained are as follows: Response of observed climate during Meiyu period over YHRV to global warming Under the background of global warming, the climate in the Meiyu period over YHRV has also undergone corresponding changes, the temperature has shown a significant increase trend, and the precipitation has also been adjusted accordingly. The precipitation was relatively more in the warm years but less in the cold years. In general, the temperature during the Meiyu period over YHRV in the cold years is low and the precipitation is less. During the warm rainy season, the temperature over YHRV was high and the precipitation has an increase. In terms of spatial distribution, after global warming, the temperature during the Meiyu period over YHRV gradually increases from south to north. The precipitation during the Meiyu period over YHRV generally shows an increasing trend, but only a small reduction in the northern part of the region. Assessment and future forecast of climate change over YHRV simulated by CMIP5 models The ensemble average of 22 CMIP5 models has a good spatial simulation of the average variation trend of the Meiyu period climate over YHRV, which reproduces the climatic distribution characteristics of temperature and precipitation during the Meiyu period over YHRV. It is feasible to estimate the climate of the Meiyu period over YHRV in the future. In the context of further global warming in the future, the average temperature and precipitation during the Meiyu period over YHRV have a further increase, and with the increase in emissions, the spatial heterogeneity of precipitation is also increasing. Under two emission scenarios, the temperature and precipitation during the Meiyu period over YHRV show a significant upward trend comparing with modern times. The increase in temperature is holistic and evenly distributed. The rate of change of the Multi-model Ensemble (0.45°C·(10a)-1) in the RCP8.5 scenario is higher than the RCP4.5 scenario (0.23°C·(10a)-1). By the end of the 21st century, the temperature during the Meiyu period over YHRV under the RCP4.5 scenario has an average temperature increase of 2.20 C relative to modern times. Under the RCP 8.5 scenario, the increase of temperature is more significant, reaching 4.30 °C. The rate of change of the Multi-model Ensemble under the RSP4.5 scenario over YHRV during the Meiyu period (0.72mm·(10a)-1) is slightly higher than RCP8.5 scenario (0.51mm·(10a)-1), and the spatial distribution unevenness of precipitation under the RCP 8.5 scenario is also higher than that under the RCP 4.5 scenario. With the passage of time, the spatial distribution unevenness of the two discharge scenarios is increasing: while the precipitation in the southern part of YHRV is decreasing, the precipitation in the north has a significantly increase. Discussion of climate change mechanism during Meiyu Period over YHRV The Asian summer monsoon is the most important circulation system affecting summer precipitation. The 850hPa wind field transports water vapor from the South China Sea and the Bay of Bengal to YHRV, which is directly related to the precipitation during the Meiyu period over YHRV. In the warm years, the weakened South Asian summer monsoon allows water vapor to be transported to the Yangtze River basin, merges the water vapor of the East Asian summer monsoon over YHRV, which together cause the climate over YHRV region to be wet, and vice versa. The water vapor over YHRV is mainly transported by the westerly flow of the South Asian monsoon. The latitudinal transport of the South Asian monsoon is relatively strong in the warm year, when the climate is humid, and vice versa.There is a significant positive correlation between the Meiyu rainfall over YHRV and SST in the equatorial middle-east Pacific Ocean, in which the extreme situation is reflected in the typical El Niño and La Niña episodes. In the typical El Niño affected years, the positive anomalies of SST in the Indian Ocean are in favor of transporting abundant water vapor to south part of YHRV and further beneficial for the Meiyu rainfall there. However, in the typical La Niña affected years, the positive anomalies of SST in the western north Pacific Ocean are in favor of the Meiyu rainfall over eastern part of YHRV. The simulations by CMIP5 atmosphere-only models show that the uniform increasing of SST in global can drive an uneven distribution in the Meiyu rainfall over YHRV, in which the rainfall is increased over the eastern part (coastal) but decreased over the western part (interior) of YHRV. Therefore, the anomalies of SST in the western north Pacific Ocean indicate more important to the Meiyu rainfall over YHYV, which could provide some clue to the weather forecast in flood season under a warmer climate.
Pages63
URL查看原文
Language中文
Document Type学位论文
Identifierhttp://ir.lzu.edu.cn/handle/262010/338319
Collection大气科学学院
Affiliation大气科学学院
First Author AffilicationCollege of Atmospheric Sciences
Recommended Citation
GB/T 7714
吴楚樵. 江淮流域梅雨期气候对全球气候变暖的响应[D]. 兰州. 兰州大学,2019.
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