有无El Niño影响下热带北大西洋春季增暖的差异及可能成因

叶洋波; 余锦华

doi:10.16032/j.issn.1004-4965.2021.012

有无El Niño影响下热带北大西洋春季增暖的差异及可能成因

doi: 10.16032/j.issn.1004-4965.2021.012

叶洋波,
余锦华^,

南京信息工程大学气象灾害教育部重点实验室/气象灾害预报预警与评估协同创新中心，江苏南京 210044

基金项目: 国家自然科学基金（41575083、41730961）资助

详细信息

通讯作者:
余锦华，女，安徽省人，教授，博士研究生导师，主要从事热带气旋、极端天气气候等方面的研究。E-mail: jhyu@nuist.edu.cn

中图分类号: P732
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- 被引次数: 0
出版历程
- 收稿日期: 2020-06-15
- 修回日期: 2020-11-28
- 刊出日期: 2021-02-01

INFLUENCE OF EL NIÑO ON SPRING WARMING IN THE NORTHERN TROPICAL ATLANTIC AND POSSIBLE CAUSES OF THE INFLUENCE

YE Yang-bo,
YU Jin-hua^,

Key Laboratory of Meteorological Disaster of Ministry of Education / Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing 210044, China

摘要

摘要: 热带北大西洋(Northern Tropical Atlantic，NTA)海温异常(sea surface temperature anomaly，SSTA)对美洲乃至全球的气候变率有着重要影响。利用再分析资料对NTA的暖SSTA进行诊断，分析有、无El Niño影响下春季增暖的差异以及可能的成因。结果表明，与El Niño有关的情形中关键区(5~25 °N，10~60 °W)平均春季SSTA为0.55 ℃，无El Niño情形是0.37 ℃；前者与冬季的显著正偏差出现在NTA，后者主要发生在NTA的东侧，且正偏差的数值较小。El Niño激发的热带外Rossby波活动通过加强北大西洋涛动(North Atlantic Oscillation，NAO)负位相，引起El Niño峰值后NTA海域显著的西风异常，暖Kelvin波加热NTA对流层大气，增强其容纳水汽的能力，减小海-气界面的垂直湿度梯度，两者共同作用使海表蒸发减弱，在NTA春季呈现显著暖SSTA。与El Niño无关的情形中，NTA SSTA的变化主要受热带海-气反馈过程的调制，其与热带外NAO的季节内振荡有关，NAO的季节平均负位相较弱，异常西风值较小，同时海-气垂直湿度梯度异常增大，使春季NTA的增暖较弱。
- NTA /
- 春季SSTA /
- El Niño /
- 遥相关 /
- NAO
Abstract: Sea surface temperature anomaly (SSTA) in the Northern Tropical Atlantic (NTA) has important effects on climate variation in the Americas and the world at large. Reanalysis data are used to diagnose warm NTA SSTA, and the difference in spring warming with or without the influence of El Niño and the possible causes of the difference are analyzed. The results show that the average spring SSTA related to El Niño reaches 0.55℃in the key area (5°N~25°N, 10°W~60°W), while the one without the influence of El Niño only reaches 0.37℃; the significant positive deviation between the former and winter occurs in the NTA, while the latter occurs mainly on the east side of the NTA, and the value of the positive deviation is relatively small. The El Niño-induced anomalous activity flux of Rossby wave outside the tropics leads to significant westerly anomalies in the NTA by strengthening the negative NAO phase after the mature phase of El Niño. The warm Kelvin wave heats the troposphere over the NTA, enhancing its ability to hold water vapor and reducing the vertical humidity gradient at the sea-air interface. Under the combined impact of them two, the evaporation in sea surface decreases, leading to warm SSTA in spring in the NTA. When there is no influence of El Niño, the variation of NTA SSTA is mainly modulated by the tropical sea-air feedback process and related to the intra-seasonal oscillation of NAO outside the tropics. The seasonal mean negative phase of NAO is relatively weak, and thus the anomalous westerly wind is small, while the vertical humidity gradient at the sea-air interface increases, leading to weaker NTA warming.
- NTA /
- spring SSTA /
- El Niño /
- teleconnection /
- NAO

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图 1 北大西洋春季SST标准差分布图

方框表示关键区(10~60 °W，5~25 °N)。

下载: 全尺寸图片幻灯片

图 2 情形1下(a，c)、情形2下(b，d)NTA春季合成SSTA及SSTA_MAM ₍₁₎- SSTA_DJF _(0-1)分布(填色，单位：℃)

点区表明通过0.05显著性检验，蓝色方框表示关键区(10~60 °W, 5~25 °N)。

下载: 全尺寸图片幻灯片

图 3 情形1下、情形2下合成混合层海温异常变率(实线，单位：10^-2 ℃/月)与动力项和热力项之和(虚线)导致的变率(a，d)；短波辐射(虚线)、长波辐射(点线)、潜热通量(粗实线)及感热通量项(细实线)导致的变率(b，e)；纬向(实线)，经向(虚线)与垂直平流(点线)导致的变率(c，f)

月份(1)表示NTA春季异常增暖年的月份，月份(0)则表示前一年的月份。

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图 4 两种情形下海温变率峰值时各项贡献(单位：℃/月)

灰色代表情形1在2月的情况，黑色代表情形2在1月的情况。

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图 5 情形1下、情形2下1—3月(1)合成10 m风场异常(箭头，单位：m/s)及海表饱和比湿与大气2 m处实际比湿差值的异常分布(等值线，单位：g/kg) (a，c)；2—4月(1)合成潜热通量异常(等值线，单位：W/m²) (b，d)

通过0.05显著性检验区域填色，风矢量通过0.05显著性检验者标红，b、d中潜热通量异常向上为正，向下为负。

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图 6 两种情形下合成标准化NAO指数与关键区SSTA(单位：℃)演变曲线

实线表示情形1，虚线表示情形2，黑色为NAO指数，灰色为SSTA。

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图 7 情形1(a)与情形2(b)下1—3月合成海平面气压异常(填色，单位：hPa)和10 m风异常(箭头，单位：m/s)

点区表示通过0.05显著性检验，风矢量仅给出通过0.05显著性检验者。

下载: 全尺寸图片幻灯片

图 8 情形1(a)与情形2(b)下1—3月(1)合成500 hPa位势高度异常(填色，单位：gpm)与温度异常(等值线，单位：℃)

点区表示通过0.05显著性检验。

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图 9 情形1(a)与情形2(b)下1—3月(1)合成降水异常(填色，单位：mm/day)与500 hPa T-N波活动通量异常(箭头，单位：m²/s²)

矢量仅给出通过0.05显著性检验者。

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表 1 NTA春季海温暖事件分类结果

暖事件类型	年份
El Niño衰减年暖事件(情形1)	1983 1987 1988 1998 2005 2010
Niño暖事件(情形2)	1980 1981 1996 1997 2013

下载: 导出CSV

表 2 关键区SSTA(单位：℃)与标准化NAO指数的滞后与超前相关系数

时间间隔/月		-3	-2	-1	0	1	2	3
滞后与超前相关系数	情形1	0.044	0.010	-0.086	-0.302	-0.486	-0.476	-0.415
滞后与超前相关系数	情形2	0.160	0.341	0.083	-0.307	-0.509	-0.331	-0.225

下载: 导出CSV

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