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段亚楠, 刘伯奇. 2023. 不同再分析资料南海夏季风爆发的气候特征和年际变率[J]. 大气科学, 48(X): 1−14. DOI: 10.3878/j.issn.1006-9895.2210.22079
引用本文: 段亚楠, 刘伯奇. 2023. 不同再分析资料南海夏季风爆发的气候特征和年际变率[J]. 大气科学, 48(X): 1−14. DOI: 10.3878/j.issn.1006-9895.2210.22079
DUAN Yanan, LIU Boqi. 2023. Climatological Features and Interannual Variability of the South China Sea Summer Monsoon Onset for Different Reanalysis Datasets [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 48(X): 1−14. DOI: 10.3878/j.issn.1006-9895.2210.22079
Citation: DUAN Yanan, LIU Boqi. 2023. Climatological Features and Interannual Variability of the South China Sea Summer Monsoon Onset for Different Reanalysis Datasets [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 48(X): 1−14. DOI: 10.3878/j.issn.1006-9895.2210.22079

不同再分析资料南海夏季风爆发的气候特征和年际变率

Climatological Features and Interannual Variability of the South China Sea Summer Monsoon Onset for Different Reanalysis Datasets

  • 摘要: 南海夏季风爆发标志着东亚夏季风的全面建立,其对我国主汛期雨带分布具有重要指示意义。本文对比了日本气象厅JRA-55、欧洲中期数值预报中心ERA5、中国气象局CRA-40和美国国家环境预测中心NCEP1四套再分析资料中南海夏季风爆发的气候特征和年际变率。结果表明,在四套再分析资料中,南海夏季风爆发期间大气环流和降水场突变的气候特征基本一致,但CRA-40资料的高空暖中心和降水均明显强于JRA-55、ERA5和NCEP1资料。同时,本文分别采用850 hPa纬向西风(U850)盛行、对流层中上部平均经向温度梯度(MTG)反转和南海地区对流建立来定义南海夏季风爆发时间。基于不同的定义指标,四套再分析资料所确定的南海夏季风爆发时间在大多数年份一致,表现为高、低空环流的调整伴随着南海季风对流的建立,环流和降水场完全耦合,且U850定义指标对资料的敏感度高于MTG定义指标。但在个别年份,三种指标所确定的南海夏季风爆发时间差异明显,这时高、低空环流和降水场的耦合关系不明确。当U850、MTG和OLR所定义南海夏季风爆发时间的年际变率一致时,4~5月海温异常场呈现典型的ENSO型分布特征,说明这些年份南海夏季风爆发可能受热带海—气相互作用影响,其中5月孟加拉湾的海温异常可能是ENSO影响南海夏季风爆发时间的关键。而当三种定义方式所得南海夏季风爆发时间的年际变率不一致时,最明显的海温异常信号出现在北太平洋加州沿岸,说明中纬度海—气相互作用对南海夏季风爆发时间也存在潜在调制作用。

     

    Abstract: The onset of SCSSM (South China Sea summer monsoon) marks the comprehensive establishment of the East Asian summer monsoon, which is crucial for the rainy season in China. This study compares the climatological features and interannual variability of the SCSSM onset between the JRA-55, ERA5, CRA-40, and NCEP1 reanalysis datasets. Results show that atmospheric circulation and precipitation evolution are consistent among these datasets. Notably, the upper-tropospheric warm center and precipitation for the CRA-40 data are the greatest. The present study uses prevailing zonal westerly wind at 850 hPa (U850), the inversion of the mean MTG (meridian temperature gradient) in the middle and upper troposphere, and the establishment of convection in the SCS to define the SCSSM onset date. Based on different indicators, this date with the four reanalysis datasets is consistent in most years in which the circulation is completely coupled with convection. In these years, convection is established over the SCS while the upper- and lower-level circulations are adjusting. However, in individual years, the SCSSM onset date defined by the three indicators is very different because the coupling between the upper- and lower-level circulations is indefinite. When the interannual variability of the onset date defined by U850, MTG, and OLR is consistent, the SST anomaly field from April to May presents a typical ENSO-type distribution, indicating that in these years, tropical sea–air interaction is critical for the SCSSM onset. The SST anomaly in the Bay of Bengal in May is perhaps the critical factor because of which ENSO influences the SCSSM onset. When the interannual variability is inconsistent, the most apparent SST anomaly occurs along the California coast of the North Pacific, indicating that midlatitude sea–air interaction may modulate the SCSSM.

     

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