Quantifying the width of the tropics has important implications for understanding climate variability and the atmospheric response to anthropogenic forcing. Considerable effort has been placed on quantifying the width of the tropics at tropospheric levels, but substantially less effort has been placed on quantifying the width at stratospheric levels. Here we probe tropical width in the stratosphere using chemical tracers, which are accessible by direct measurement. Two new tracer‐based width metrics are developed, denoted here as the “1σ method” and the gradient weighted latitude (GWL) method. We evaluate widths from three tracers, CH₄, N₂O, and SF₆. We demonstrate that unlike previously proposed stratospheric width methods using tracers, these metrics perform consistently throughout the depth of the stratosphere, at all times of year and on coarse temporal data. The GWL tracer‐based widths correlate well with the turnaround latitude and the critical level, where wave dissipation occurs, in the upper and midstratosphere during certain months of the year. In the lower stratosphere, the deseasonalized tracer‐based widths near the tropical tropopause correlate with the deseasonalized tropopause‐height based metrics. We also find that tracer‐tracer width correlations are strongest at pressure levels where their chemical lifetimes are similar. These metrics represent another useful way to estimate stratospheric tropical width and explore any changes under anthropogenic forcing.

中文翻译：

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利用示踪剂浓度估算平流层热带宽度

量化热带的宽度对于理解气候变化和大气对人为强迫的反应具有重要意义。在对流层水平上对热带的宽度进行量化方面已付出了相当大的努力，而对平流层水平上的宽度进行了量化方面的工作却少得多。在这里，我们使用化学示踪剂探测平流层中的热带宽度，可通过直接测量来获得。开发了两个基于示踪剂的新宽度度量，在此称为“1σ方法”和梯度加权纬度（GWL）方法。我们从三个示踪物CH ₄，N ₂ O和SF ₆评估宽度。我们证明，与以前使用示踪剂提出的平流层宽度方法不同，这些度量标准在平流层的整个深度，一年中的所有时间和粗略的时空数据上均能始终如一地执行。在一年中的某些月份中，基于GWL示踪剂的宽度与平流层上层和中层的周转纬度和临界水平（发生波消散）密切相关。在平流层下层，热带对流层顶附近基于季节的示踪剂示踪宽度与基于对流层顶高度的反季节化测度相关。我们还发现，在化学寿命相似的压力水平下，示踪剂与示踪剂的宽度相关性最强。这些度量标准代表了另一种有用的方式来估算平流层的热带宽度并探讨人为强迫下的任何变化。