Polar stratospheric clouds and the Antarctic ozone hole
Polar stratospheric clouds and the Antarctic ozone hole
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DOI：
10.1029/jd093id07p08423
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发表时间：
1988-07
影响因子：
--
通讯作者：
L. Poole;M. McCormick
中科院分区：
文献类型：
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作者：
L. Poole;M. McCormick
提出了极地平流层云(PSCS)形成和发展的理论模型。假设这一过程分为三个阶段：(1)远高于霜点的过冷H_2SO_4-H_2O平流层气溶胶液滴的“先驱”阶段；(2)在接近霜点但高于霜点的温度下通过HNO_3·3H_2O共沉积形成PSC粒子的中间(第一类)阶段；(3)在霜点以下温度下纯水冰和HNO_3·3H_2O的最后(第二类)沉积阶段。计算的光学背向散射与温度的关系与在北极两次机载激光雷达实验中观测到的值吻合得很好，除了在30mbar气压水平上的小系统误差，这可能是由于温度场描述得不好所致。额外的理论计算解决了南极洲形成PSC的问题。这些结果表明，在70mbar高度(接近17公里)，大约80%和30%的可用HNO_3和H_2O水蒸气在189K附近的相对较大的(4-μm半径)PSC粒子中被隔离，比估计的当地霜点低约2K。如此大的粒子将以大约2公里wk−1的速度下落，这表明PSC可能会在平流层重新分配这些痕量气体，或者可能通过向对流层沉积将它们完全清除。
A theoretical model is presented for the formation and growth of polar stratospheric clouds (PSCs). The process is assumed to occur in three stages: (1) a “precursor” stage of supercooled H2SO4-H2O stratospheric aerosol droplets at temperatures well above the frost point; (2) an intermediate (type I) stage of PSC particle formation by codeposition of HNO3 · 3H2O at temperatures near, but above the frost point; (3) a final (type II) stage of deposition of pure water ice and HNO3 · 3H2O at temperatures below the frost point. The calculated temperature dependence of optical backscattering agrees well with values observed during two Arctic airborne lidar experiments except for small systematic errors at the 30-mbar pressure level which may be due to poor characterization of the temperature field. Additional theoretical calculations address the issue of PSC formation in Antarctica. These results show that at the 70-mbar level (near 17 km), about 80% and 30% of the respective HNO3 and H2O vapor available may be sequestered in relatively large (4-μm radius) PSC particles at a temperature near 189 K, some 2 K below the estimated local frost point. Such large particles would fall at a rate of about 2 km wk−1, suggesting that PSCs may act to redistribute these trace gases in the stratosphere or perhaps remove them altogether by sedimentation to the troposphere.