Chemical definition of the mesospheric polar vortex
Chemical definition of the mesospheric polar vortex
复制标题
中层极涡的化学定义
DOI：
10.1002/2015jd023488
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
R. Collins
中科院分区：
文献类型：
--
作者：
V. Harvey;C. Randall;R. Collins
我们提出了一个简单的化学定义来区分中间层极涡的边缘。由于这种涡旋定义不依赖于风场，因此在风观测稀疏且再分析风不可靠的中间层中很有用。化学定义对使中层涡旋识别复杂化的双急流也不敏感。该算法是基于一氧化碳（CO）的水平梯度，并反映了广泛使用的涡边缘定义在平流层的基础上的位涡（PV）梯度。在这里，该方法被用来确定在10年（2004-2014年）的微波临边探测器数据记录的中间层的北极涡旋。涡的大小和形状的比较CO和PV方法重叠在平流层上部。在NH 2008-2009年冬季的一个案例研究，展示了在个别日子的CO梯度方法的保真度，并强调双射流的方法，以确定极涡的影响。我们建议从平流层中基于PV或流函数的涡旋定义过渡到使用0.1 hPa（~60 km）以上的CO梯度定义。CO梯度方法确定了80 km处的高CO相干区域，该区域在北极冬季99.8%的时间内仅限于中高纬度。利用CO梯度方法识别极涡，在最可疑的大气区域增加了约20公里的可靠涡旋信息（从60公里到80公里）。
We present a simple chemical definition to demark the edge of the mesospheric polar vortices. Because this vortex definition does not rely on the wind field, it is useful in the mesosphere where wind observations are sparse and reanalysis winds are unreliable. The chemical definition is also insensitive to double jets that complicate vortex identification in the mesosphere. The algorithm is based on horizontal gradients of carbon monoxide (CO) and mirrors the widely used vortex edge definition in the stratosphere based on potential vorticity (PV) gradients. Here the approach is used to identify the Arctic vortex in the mesosphere during a 10 year (2004–2014) record of Microwave Limb Sounder data. Vortex size and shape comparisons are made where the CO and PV methods overlap in the upper stratosphere. A case study is presented during the NH 2008–2009 winter that demonstrates the fidelity of the CO gradient method on individual days and emphasizes the impact of double jets on methods to identify the polar vortex. We recommend transitioning from a PV or stream function‐based vortex definition in the stratosphere to using a CO gradient definition above 0.1 hPa (~60 km). The CO gradient method identifies a coherent region of high CO at 80 km that is confined to mid‐to‐high latitudes 99.8% of the time during Arctic winter. Taking advantage of the CO gradient method to identify the polar vortex adds ~20 km of reliable vortex information (from 60 to 80 km) in a region of the atmosphere where reanalyses are most suspect.