东亚大槽和西伯利亚高压的季节内变率对冬季东亚气温的影响
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国家自然科学基金资助项目 (42088101)


Impacts of intra-seasonal variability of the East Asian trough and the Siberian high on East Asian temperatures in the northern winter
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    摘要:

    基于气候态定义了西伯利亚高压指数(SH index)、东亚大槽指数(ET index)和高低压系统间的东亚经向风指数(V index),使用回归分析探究西伯利亚高压和东亚大槽在季节内尺度上对东亚地区冬季温度的影响机理,构建线性模型对冬季华南地区季节内尺度温度进行延伸期预报。结果表明:西伯利亚高压和东亚大槽系统变化中最显著的是季节内尺度信号;季节内尺度SH index和ET index对V index的贡献分别为82.6% 和42.2%;3个指数的回归模态在对流层中层对应西北-东南向低频罗斯贝波列缓慢东南传播,低层水汽、近地面层环流、降水及2 m温度场配置良好,当西伯利亚高压深厚或东亚大槽发展时,经向风关键区北风强盛,有利于冬季高纬度地区干冷空气向东亚输送;V index对华南地区冬季季节内尺度2 m气温的有效预报时效达25 d。

    Abstract:

    Both the Siberian high and the East Asian trough play crucial roles in the East Asian winter climate system.Changes in the strength and position of the Siberian high can lead to the movement of cold or warm air masses over the East Asian continent,while variations in the East Asian trough can influence circulation patterns in the western Pacific.These combined effects can alter temperature and precipitation distributions in East Asia during the winter,significantly impacting the winter climate.This study defines the Siberian High (SH) index,the East Asian Trough (ET) index,and a Meridional Wind (V index) index between the high and low-pressure systems based on climatological characteristics.The relationships between these indices are explored using power spectrum analysis and linear regressions.The study investigates the significant periods of variability and the impact mechanisms of the Siberian high and East Asian trough on winter temperatures in East Asia.Additionally,a simple linear regression model is constructed using a non-filtering method and cross-validation for extended-range forecasts of intra-seasonal temperatures in southern China during the winter.The main conclusions are as follows:The most significant periods of the SH and ET indices occur on intra-seasonal timescales,accounting for 60% of the total standard deviation.Power spectrum analysis results show that the energy peaks of the SH and ET indices are concentrated in the 10—50-day period,while the V index is more concentrated in the 10—40-day period.On the intra-seasonal timescales,the correlation coefficients between the SH/ET indices and the V index are 0.69 and -0.73,respectively (through a 99% confidence test).The reconstructed meridional wind fields related to the SH/ET indices are used to calculate the ratio of the standard deviation compared to the actual meridional wind field.Quantitative results show that the contributions of the intra-seasonal SH and ET indices to the V index are 82.6% and 42.2%,respectively.Lead-lag regression analysis for the SH,ET,and V indices shows similar regression patterns,with slow eastward propagation of northwest-southeast distributing wave trains in the 500 hPa geopotential height field,consistent configurations of the low-level 850 hPa moisture,near-surface 925 hPa circulations,precipitation,and 2 m temperature fields.The three indices all correspond to a northwest-southeast-oriented low-frequency Rossby wave train in the middle and higher troposphere,which propagates eastward or southeastward.The upper-level circulation fields are well linked to low-level water vapor,precipitation,and surface air temperature fields.When the Siberian high deepens or the East Asian trough develops,northerly winds are enhanced over the key East Asian region,facilitating the transport of dry and cold air from high latitudes in Siberia to East Asia,resulting in dry and cold weather conditions.Based on comprehensive regression results,the V index and the intra-seasonal component of 2 m temperature during winter in southern China are selected as the predictors and predictands.A linear regression model is built for extended-range forecasting,and the forecast performance is evaluated by calculating the time correlation coefficient and standardized root mean square error.Cross-validation and independent forecast experiments indicate that reliable forecasts of the intra-seasonal 2 m temperature in the region with a lead time of 25 days can be achieved.

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李天明,丁柳丹,2024.东亚大槽和西伯利亚高压的季节内变率对冬季东亚气温的影响[J].大气科学学报,47(2):184-200. LI Tim, DING Liudan,2024. Impacts of intra-seasonal variability of the East Asian trough and the Siberian high on East Asian temperatures in the northern winter[J]. Trans Atmos Sci,47(2):184-200. DOI:10.13878/j. cnki. dqkxxb.20240117011

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  • 收稿日期:2024-01-17
  • 最后修改日期:2024-02-15
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  • 在线发布日期: 2024-05-22
  • 出版日期: 2024-03-28

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