Troposphere‐stratosphere coupling: Links to North Atlantic weather and climate, including their representation in CMIP5 models
Troposphere‐stratosphere coupling: Links to North Atlantic weather and climate, including their representation in CMIP5 models
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DOI：
10.1002/2013jd021191
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发表时间：
2014-05
期刊：
影响因子：
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通讯作者：
T. Shaw;J. Perlwitz;O. Weiner
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文献类型：
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作者：
T. Shaw;J. Perlwitz;O. Weiner
利用欧洲中期天气预报再分析中心(ERA)中期再分析资料，根据平流层行星尺度波动热通量事件，建立了一个新的对流层-平流层耦合的动力学度量。平流层热通量极值与对流层中的高纬度行星尺度波型和大西洋盆地的纬向风、温度和平均海平面气压异常瞬时相关。这些影响让人想起北大西洋涛动的不同阶段。特别是，平流层中的极端正(负)热通量事件与北大西洋盆地向赤道(极地)急流移动有关。该指标用于评估参与耦合模式对比项目第五阶段(CMIP5)的模式中的对流层-平流层耦合。结果表明，具有退化的平流层极值表示的模式在对流层中相对于ERA-TERTER表现出强烈的偏差。特别是，具有偏向平流层极值的模式显示出偏向的气候学驻波模式和对流层中的大西洋急流位置。此外，这些模式在北大西洋地区的位势高度和纬向风极值方面也显示出偏差。平流层偏差与模型盖子高度有关，但不足以评估对流层的影响。我们的分析表明，平流层热通量的平均偏差也不足以评估对流层-平流层耦合的表示。总体而言，结果表明，在对流层-平流层耦合的多模式评估中，基于平流层热通量极值的度量应该与基于极地涡旋事件的度量结合使用。
A new dynamical metric of troposphere‐stratosphere coupling is established based on extreme stratospheric planetary‐scale wave heat flux events, defined as the 10th and 90th percentiles of the daily high‐latitude averaged heat flux distribution at 50 hPa using European Centre for Medium‐Range Weather Forecasts Re‐Analysis (ERA)‐Interim reanalysis data. The stratospheric heat flux extremes are linked instantaneously to high‐latitude planetary‐scale wave patterns in the troposphere and zonal wind, temperature, and mean sea level pressure anomalies in the Atlantic basin. The impacts are reminiscent of different phases of the North Atlantic Oscillation. In particular, extreme positive (negative) heat flux events in the stratosphere are associated with an equatorward (poleward) jet shift in the North Atlantic basin. The metric is used to evaluate troposphere‐stratosphere coupling in models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). The results show that models with a degraded representation of stratospheric extremes exhibit robust biases in the troposphere relative to ERA‐Interim. In particular, models with biased stratospheric extremes exhibit a biased climatological stationary wave pattern and Atlantic jet stream position in the troposphere. In addition, these models exhibit biases in geopotential height and zonal wind extremes in the North Atlantic region. The stratospheric biases are connected to model lid height, but it is not sufficient for assessing the tropospheric impacts. Our analysis reveals that the mean bias of the stratospheric heat flux is also not sufficient for assessing the representation of troposphere‐stratosphere coupling. Overall, the results suggest that a metric based on stratospheric heat flux extremes should be used in conjunction with metrics based on extreme polar vortex events in multimodel assessments of troposphere‐stratosphere coupling.