| 20CR再分析资料在东亚夏季风区的质量评估 |
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| 引用本文： | 宋丰飞,周天军.20CR再分析资料在东亚夏季风区的质量评估[J].大气科学,2012,36(6):1207-1222. |
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| 作者姓名： | 宋丰飞 周天军 |
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| 作者单位： | 1.中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室 (LASG), 北京 100029;中国科学院研究生院, 北京 100049; |
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| 基金项目： | 全球变化国家重大科学研究计划项目2010CB951904;国家自然科学基金重大项目40890054;先导科技专项XDA05110300 |
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| 摘 要： | 本文利用NCEP1和ERA40再分析资料, 并结合观测资料, 对最新公布的一套再分析资料——20CR再分析资料在东亚夏季风区的质量进行了综合评估。本文主要是从气候态、年际变率、年代际变化三个方面, 来评估20CR再分析资料在东亚夏季风区的质量。结果表明, 在气候平均态上, 20CR再分析资料基本合理再现了东亚夏季风区的高低层环流场(包括南亚高压、副热带西风急流、近地层风场)以及经向环流圈特征。但相较于NCEP1和ERA40, 20CR所刻画的南亚高压偏强, 西风急流偏北, 对流层中上层温度系统性偏高。在年际变率方面, 除了NCEP1在1967年之前存在偏差, 使其结果和ERA40、20CR不同之外, 三套再分析资料刻画的东亚夏季风变率在其它时段高度一致。三套资料在以纬向风为基础的东亚夏季风指数上的一致性, 高于以经向风为基础的东亚夏季风指数, 其中以低层纬向风为基础的东亚夏季风指数的一致性最高。20CR再分析资料可以较好地再现与东亚夏季风相联系的地表气温和降水年际变化特征, 其刻画的地表气温正相关中心位置偏西、强度最强, 且在河套平原地区有一个弱的负相关中心, 而其描述的降水在孟加拉湾和长江流域较之另外两套再分析资料更接近观测结果, 在热带地区和海上却反之。在年代际变化方面, 20CR再分析资料未能合理再现东亚夏季风年代际减弱的现象, 这也体现在不能合理再现青藏高原下游年代际变冷和“南涝北旱”降水型上, 这主要是因为20CR再分析资料所刻画的东亚地区对流层中上层年代际变冷信号偏弱所致。而在百年时间尺度上, 20CR再分析资料所刻画的东亚夏季风变化与观测较为一致;20CR再分析资料可以合理再现出东亚夏季风区1920年代前的显著冷期和1990年代之后的迅速增暖期, 但对1920～1950年代相对暖期和1950～1980年代相对冷期的再现能力较差。
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| 关 键 词： | 20CR再分析资料 东亚夏季风 气候态 年际变率 年代际变化 |
| 收稿时间： | 2012/1/13 0:00:00 |
| 修稿时间： | 2012/6/19 0:00:00 |
Reliability of the 20CR Reanalysis Data in Measuring the East Asian Summer Monsoon Variability |
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| SONG Fengfei and ZHOU Tianjun.Reliability of the 20CR Reanalysis Data in Measuring the East Asian Summer Monsoon Variability[J].Chinese Journal of Atmospheric Sciences,2012,36(6):1207-1222. |
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| Authors: | SONG Fengfei and ZHOU Tianjun |
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| Institution: | State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029
;Graduate University of Chinese Academy of Sciences, Beijing 100049
;;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029
;Climate Change Research Center, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | This study evaluates the performance of the recently released 20th Century Reanalysis (20CR) data in describing East Asian summer monsoon (EASM) variability by contrasting the results with NCEP1 and ERA40 reanalysis and instrumental datasets. This analysis focuses on the climatology, interannual variability, and decadal change of the EASM. The results show that the 20CR reanalysis data reasonably depicts the high- and low-level circulation fields, including the South Asian high, subtropical jet, and near surface wind, and the meridional monsoon circulation cell. However, in comparison with NCEP1 and ERA40, 20CR data shows a stronger South Asian high, more northward displacement of the subtropical jet, and systematically warmer air temperature in the mid- and high-troposphere. The three reanalysis datasets are highly consistent in measuring EASM variability with the exception of the period before 1967, during which interannual variability results differ due to biases in NCEP1. The monsoon indices based on zonal wind shows better consistency than those based on meridional wind, and the monsoon index based on low-level zonal wind shows the best consistency among the three datasets. 20CR reasonably reproduces interannual variability of the surface air temperature and precipitation related to the EASM, which has a westward and strongest positive correlation center and a weak negative correlation center near Hetao Plain. In addition, precipitation in the Bay of Bengal and along the Yangtze River valley is represented more accurately in the 20CR dataset than that in the other two reanalysis datasets; however, results are opposite in the tropical regions and the oceans. At the interdecadal time scale, however, the 20CR reanalysis data failed to reproduce decadal weakening of the EASM circulation, which is also reflected in its failure to reproduce the observed southern China flood and northern China draught rainfall pattern and surface cooling trend downstream of the Tibetan Plateau. These results are mainly attributed to the deficiency of 20CR reanalysis data in measuring the upper tropospheric cooling tendency over East Asia. During the past 100 years, 20CR has shown consistency in EASM changes with that of observation; this dataset has reasonably depicted the notable cold period before the 1920s and the rapid warming period after the 1990s but has shown weaker skills in presenting the relatively warm period during the 1920s-1950s and the relative cold period during the 1950s-1980s in the EASM region. |
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| Keywords: | 20CR reanalysis data East Asian summer monsoon climatology interannual variability decadal change |
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