Origin of extreme ozone minima at middle to high
Origin of extreme ozone minima at middle to high
复制标题
中高臭氧极低值的起源
DOI：
10.1029/2001jd900093
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发表时间：
2001
影响因子：
5.2
通讯作者：
E. O. Hulbert
中科院分区：
文献类型：
--
作者：
M. Fromm;E. O. Hulbert
极端臭氧最低值表示臭氧柱量在某些选定的绝对水平以下的局部和短暂（几天）的减少。虽然这种极小值在中高纬度北方已知主要是动态的起源，一个剩余的问题是，是否异质的化学品损失过程也可能大大有助于其形成。一个恰当的例子是1999年11月30日出现的165个多布森单位（DU）最低值，当时最低值位置30 hPa附近的温度低于I型极地平流层云（PSC）形成的阈值。对极地臭氧和气溶胶测量III数据在事件发生前后的时间进行的检查表明，PSC确实存在于观察到臭氧最小值的附近。然而，存档的数据显示，类似的极端最低值167 DU，其特征与1999年11月30日的最低值相当，发生在1985年10月30日，当时没有PSC。71个极端臭氧极小值的振幅在215 DU以下的合奏表现出近线性关系的臭氧最小偏差从纬向平均值和相应的30百帕温度偏差。这种关系是由分析传输模型预测的，该模型假设垂直运动（即，上升流）是造成臭氧最小值的原因。1999年11月30日和1985年10月30日的事件中，30百帕附近的温度偏差异常大，这意味着这些事件异常快速的向上传输。所有71个极小值发生在偏离纬向平均330 K位涡是负的区域，这意味着它们的形成由准水平运输的额外贡献。还确定了极端臭氧极小值事件期间气柱臭氧减少的时间尺度，发现其速度至少比已知化学品损失过程的预期速度快20倍。因此，这些数据与一般极端臭氧极小值的纯粹动力学起源，特别是1999年11月30日的事件最为一致。如先前的工作所示，基本的动力学过程包括热带对流层上部臭氧贫乏空气的等熵输送和对流层上部反气旋扰动上方的快速上涌（由极向Rossby波破碎事件引起）的组合。
Extreme ozone minima represent localized and temporally brief (several days) reductions in column ozone amounts below some chosen absolute level. Although such minima at middle to high northern latitudes are known to be primarily dynamical in origin, a remaining issue is whether heterogeneous chemical loss processes may also contribute significantly to their formation. A case in point is the record low 165 Dobson units (DU) minimum occurring on November 30, 1999, when temperatures near 30 hPa at the location of the minimum were lower than the threshold for the formation of type I polar stratospheric clouds (PSC). An examination of Polar Ozone and Aerosol Measurement III data for times surrounding the event shows that PSCs were indeed present in the vicinity where the ozone minimum was observed. However, archived data show that a similar extreme minimum of 167 DU with characteristics comparable to those of the November 30, 1999, minimum occurred on October 30, 1985, when no PSCs were present. An ensemble of 71 extreme ozone minima with amplitudes under 215 DU exhibit a nearly linear relationship between ozone minimum deviations from the zonal mean and corresponding 30-hPa temperature deviations. Such a relationship is predicted by analytic transport models which assume that vertical motions (i.e., upwelling) are responsible for the ozone minima. Temperature deviations near 30-hPa were unusually large for both the November 30, 1999, and the October 30, 1985, events, implying unusually rapid upward transport for these events. All 71 minima occur in regions where deviations from the zonal mean of 330 K potential vorticity are negative, implying an additional contribution to their formation by quasi-horizontal transport. The timescale for column ozone reductions during extreme ozone minima events is also determined and found to be at least 20 times more rapid than expected from known chemical loss processes. The data are therefore most consistent with a purely dynamical origin for extreme ozone minima in general and the November 30, 1999, event in particular. As was shown by earlier work, the basic dynamical process involves a combination of isentropic transport of ozone-poor air from the tropical upper troposphere and rapid upwelling over upper tropospheric anticyclonic disturbances resulting from poleward Rossby wave breaking events.