兰州大学机构库 >大气科学学院
未来30年亚洲季风及海温的情景预估与订正
Alternative TitleProjection and Correction for Asian Monsoon and Sea Surface Temperature in the Next 30 Years under Climate Scenario
杨阳
Thesis Advisor戴新刚
2019-05-06
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Degree Discipline气象学
Keyword亚洲季风 CMIP5 情景预估 降水 水汽输送 偏差订正
Abstract本文利用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)提供的再分析ERA-20C和ERA-Interim数据集中的逐月海温、水平风场、比湿和海平面气压等再分析资料,以及英国东英格利亚大学气候研究所(Climatic Research Unit,CRU)提供的全球陆地格点分析数据集(CRU TS v4.0)中的月降水资料作为参考态,针对参与国际耦合模式比较计划第五阶段(Coupled Model Inter-comparison Project Phase 5,CMIP5)的24个全球气候模式中以上变量的历史模拟和未来排放情景(RCP4.5)下的多模式预估输出数据,首先对2006-2015年全球海温、亚洲的降水和对流层中下层水汽输送预估等的偏差,从时空分布、季节变化等多个方面进行分析,在此基础上利用扣除气候漂移、一元(对数)线性回归、一元年际增量回归、经验正交函数分解(EOF)法和贝叶斯模式平均(Bayesian Model Average method,BMA)法等方法设计了多种订正方案,对RCP4.5情景下2006-2015年全球海温、亚洲的降水和对流层中下层水汽输送预估偏差等进行订正,并通过计算距平相关系数(ACC)、均方根误差(RMSE)和距平同号率(AR)等指标对订正结果进行评估,筛选出相对较好的方法对未来30年(2016-2045年)全球海温、亚洲的降水和对流层中下层水汽输送等多模式预估结果进行统计订正。主要结论总结如下:CMIP5多模式集合能较好地预估2006-2015年全球海表温度的空间分布和季节变化。模式海温在赤道及低纬度中东太平洋和南半球中纬度的预估偏高2K左右,在北太平洋、赤道西太平洋、北大西洋和印度洋预估偏低1-2K,冬季海温预估偏暖甚于夏季。对2006-2015年的模式海温预估检验表明,订正可以有效减小预估偏差,订正后大部分海区海温偏差在±1K以内,预估海温偏高的区域主要集中在赤道及低纬度海洋,尤其是赤道太平洋;而预估偏低的区域位于北太平洋、北大西洋北部和南半球中纬度大部分海区。单一海区评估表明,太平洋和大西洋的RESM和AR优于印度洋。相对于1976-2005年平均,未来30年全球海温普遍升高,北太平洋北部及北大西洋北部增温1K左右,赤道及低纬度海区增温0.5-1K,南半球中纬度普遍增温0.5K左右。RCP4.5情景下,2006-2015年亚洲北部大部分地区模式降水预估偏多60%以上,其中年和暖季降水在印度半岛及中国东南沿海预估偏少50-60%,冷季降水预估普遍偏多。经一元对数回归订正后年降水偏差减少至±20%左右,冷季降水偏差略大于年和暖季。订正后降水距平及距平同号分布,以及降水评估指标统计检验表明,一元对数回归在亚洲北部优于一元年际增量回归,而在亚洲南部则相反。这说明在亚洲中纬度和低纬度,降水序列具有不同的统计性质。据此说明模式降水的回归订正方案具有区域性,在不同区域应该选择相对最优的订正方法。利用区域组合订正法,即在亚洲南部(31°N以南,60°E以东)用一元年际增量回归订正,其余地区用一元对数回归订正,订正后2006-2015年年降水预估场的ACC和AR分别达0.218、59.8%,高于任一线性回归订正结果。相对于1976-2005年平均,组合订正后未来30年(2016-2045年)年和暖季降水在印度半岛、中南半岛及中国西北中部和东南沿海降水偏多10-40%,在青藏高原西南、中国西北北部、西南地区、江南中部及东北地区偏少10-40%,冷季在印度半岛大部、中南半岛、中国西北大部、西南地区、东南沿海及东北地区降水偏少20-40%。考虑地形影响,季风可用对流层中下层水汽输送通量近似表示。虽然CMIP5多模式集合可以较好地再现出亚洲对流层中下层水汽输送的季节特征,但依旧存在明显的偏差。2006-2015年亚洲对流层中下层水汽输送预估在夏季偏弱,而冬季预估偏强。夏季水汽输送主要在阿拉伯海、印度半岛预估偏少120kg/(m·s)左右,在青藏高原附近区域预估偏多100-120kg/(m·s),冬季在印度洋及中国东海及其附近北太平洋预估偏多100-150kg/(m·s)。经扣除气候漂移、一元线性回归和一元年际增量回归订正后水汽输送偏差明显减小,但在某些区域偏差仍然较大,如印度半岛、中南半岛、孟加拉湾及中国沿海等地。从订正结果看,以上三种订正方法的订正结果优于EOF订正法。未来30年对流层中下层水汽输送在亚洲南部增多40kg/(m·s)左右,其余地区普遍增多20kg/(m·s)以内。夏季变化明显带位于印度洋赤道以北的阿拉伯海,印度半岛,中南半岛,中国南海,到东海这一带,冬季变化主要分布在赤道西太平洋、阿拉伯海、日本海及北太平洋。总而言之,对亚洲的降水和季风的预估和订正分析表明,在气候变暖背景下,未来30年亚洲季风格局发生了较明显变化。亚州西部,南亚季风区北部和南端,中南半岛北部和南部,中国大陆南方和西北地区降水趋于减少,未来季风变化可能导致以上等地出现干旱少雨气候,而在印度半岛中部,中南半岛北部,中国三江源到淮河流域一带降水呈现增多趋势,易发生洪涝灾害。值得注意的是,以上气候预估存在一定的不确定性,仅供用户参考。
Other AbstractUsing monthly sea surface temperature(SST), horizontal wind field, specific humidity and sea-level pressure reanalysis data from the ERA-20C and ERA-Interim reanalysis datasets of European Centre for Medium-Range Weather Forecasts(ECMWF), and monthly precipitation data from the Climatic Research Unit(CRU) global land grid analysis datasets(CRU TS v4.0) as the reference state, investigating and correcting the biases of above variables simulation of historical experiments and RCP4.5 emission scenario produced by the 24 global climate models participating in the Coupled Model Inter-comparison Project Phase 5(CMIP5). From the aspects of time and space distribution, seasonal change, the biases of global SST, Asian precipitation and the middle and lower troposphere water vapor transport in 2006-2015 are analyzed. Furthermore, based on these biases a variety of bias correction methods including simple removal of climate drift, simple linear regression(with log-transformed), simple regression with year-to-year increment, the Empirical Orthogonal Function(EOF) method and Bayesian Model Average method(BMA) are used to correct the biases of global SST, Asian precipitation and the middle and lower troposphere water vapor transport in 2006-2015 under RCP4.5 emission scenario. Finally, using anomaly correlation coefficient(ACC), root mean square errors(RMSE) and anomaly rate(AR) as evaluation indicators to evaluate corrected results, and screening out the relatively preferable methods. The global SST, Asian precipitation and middle and lower troposphere water vapor transport are projected by the chosen correction methods in the next 30 years(2016-2045). The main conclusions are as follows:The multi-model ensemble has a capacity of projecting the global SST of spatial distribution and the seasonal variation in 2006-2015. The multi-model ensemble SST is overestimated about 2K over the equatorial and low latitude sea areas of the Middle East Pacific and middle latitude sea areas of the southern hemisphere, while underestimated 1-2K over North Pacific, the western equatorial Pacific, North Atlantic Ocean and the Indian Ocean. In addition, the multi-model ensemble SST is warmer in winter than in summer. The test of multi-model ensemble SST projection in 2006-2015 shows that the correction of can effectively reduce bias, and after the correction the deviation of most sea areas is within 1K. After the correction the overestimated sea areas are mainly distributed in the equatorial and low-latitude, especially the equatorial Pacific, while the underestimated sea areas are distributed in the north of North Pacific and North Atlantic Ocean, and most of the sea areas in the mid-latitude of the southern hemisphere. Statistics of single sea area shows that the RMSE and AR in the Pacific and Atlantic Oceans are larger than those in the Indian Ocean. Compared with the average of 1976-2005, the global SST will generally increase in the next 30 years. In the north of North Pacific and North Atlantic Ocean, SST will increase by about 1K, 0.5-1K in the equatorial and low-latitude sea areas, and about 0.5K in the mid-latitude of the southern hemisphere.Under the RCP4.5 emission scenario, the multi-model ensemble precipitation is overestimated in most parts of northern Asia, and it is overestimated over 60%. The annual and warm season precipitation is underestimated 50-60% in the Indian Peninsula and the southeast of China, and the cold season precipitation is generally overestimated in Asia. The annual precipitation deviation is reduced to about ±20% after the correction by linear regression with log-transformed, and the precipitation deviation in cold season was slightly larger than that in annual and warm season. Corresponding to different regression methods, the anomaly and anomaly same-sign distribution of annual, and test of evaluation indicators show that the simple linear regression with log-transformed is superior to the simple linear regression with year-to-year increment in northern Asia, while it is opposite in southern Asia. It indicates that the precipitation has different statistical properties in the middle and low latitudes of Asia. The regression correction method for model precipitation is regional, it is necessary to chose the optimal correction method in different areas. Using the regional combination regression method, which is using single regression with year-to-year increment in southern Asia(the south of 31 ºN and the east of 60 ºE ), meanwhile using single regression with log-transformed in the rest region of Asia, the precipitation ACC and AR in 2006-2015 is increased to 0.218 and 59.8%respectively, larger than any linear regression correction result. The projected precipitation for 2016-2045 is corrected by using the region combination regression method. The result shows that, compared with the average of 1976-2005, the annual and warm season precipitation will increase by 10-40% in Indian Peninsula, Indo-China Peninsula and the central northwest and southeast of China in the next 30 years, while in the southwest of the Tibet Plateau, the southwest region and the northern of northwest in China, the middle of the region south of the Yangtze River and the northeast of China will decrease by 10-40%.In the cold season, the precipitation will decrease by 20-40% in most of Indo-China Peninsula and Indian Peninsula, most of southwest, southeast and northeast China.Considering the influence of topography, the monsoon can be approximately expressed as the middle and lower troposphere water vapor transport flux. Although the CMIP5 multi-model ensemble can well reproduce the seasonal variation of the middle and lower troposphere water vapor transport of Asia, there is still an obvious bias between simulation and observation. The multi-model ensemble water vapor transport of Asia in the middle and lower troposphere is weaker in summer but stronger in winter in 2006-2015. The water vapor transport is underestimated about 120kg/(m·s) in the Arabian Sea and the Indian Peninsula in summer, but it is overestimated 100-120kg/(m·s) near the Tibet Plateau. In winter, water vapor transport is overestimated 100-150kg/(m·s) in the Indian Ocean, the East China Sea and its nearby North Pacific. Using correction methods including simple removal of climate drift, linear regression and regression with year-to-year increment, the deviation of water vapor transport is reduced, but the large deviation is still occur in some areas, such as India Peninsula, the Indo-China Peninsula, the Bay of Bengal and coastal area of China. The corrected results of the above three correction methods are superior to the EOF method. In the next 30 years, water vapor transport in the middle and lower troposphere will increase by about 40kg/(m·s) in the south of Asia, in other areas it will increase within 20kg/(m·s). The increase of water vapor transport in summer is mainly distributed from the equator to the Arabian Sea, the Indian Peninsula, Indo-China Peninsula, and extending to the East China Sea and the South China Sea. In winter, it is mainly distributed in the Arabian Sea, the equatorial western Pacific and the Sea of Japan and the North Pacific.
       In a word, under the global warming background, the correction and projection analysis of the precipitation and monsoon in Asia indicate that the Asian monsoon will show a significantly change in the next 30 years. In the western of Asia, the north of South Asian monsoon region, the north of Indo-China Peninsula, the south and the northwest of China, the precipitation tends to decrease, future monsoon change may result in arid and rainless in the above places, while the precipitation presents an increasing trend in the middle of the Indian Peninsula, the nouth of the Indo-China Peninsula, the region of resource of Three Rivers and the Huaihe River basin in China, where are apt to flood disaster. It is noteworthy that there is still uncertain in the above climate prediction, which is only for users to reference.
Pages69
URL查看原文
Language中文
Document Type学位论文
Identifierhttp://ir.lzu.edu.cn/handle/262010/338324
Collection大气科学学院
Affiliation大气科学学院
Recommended Citation
GB/T 7714
杨阳. 未来30年亚洲季风及海温的情景预估与订正[D]. 兰州. 兰州大学,2019.
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