Six years of UARS Microwave Limb Sounder HNO3 observations: Seasonal, interhemispheric, and interannual variations in the lower stratosphere
Six years of UARS Microwave Limb Sounder HNO3 observations: Seasonal, interhemispheric, and interannual variations in the lower stratosphere
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UARS 微波临边探测器 HNO3 六年观测：平流层下部的季节性、半球间和年际变化
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
J. Waters
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作者：
M. Santee;G. Manney;L. Froidevaux;W. Read;J. Waters
根据UARS微波测深仪(MLS)在两个半球进行的6个完整的年周期对气相HNO3的测量，概述了平流层低层HNO3分布的季节、半球间和年际变化。除冬季极地外，在所有纬度带和所考察的所有年份中，465K位温面上的纬向平均HNO3混合比在两个半球内是相当的。除高纬度地区外，年际变化很小，HNO3的总体分布或季节周期没有明显的半球不对称性。尽管南极经历了广泛的严重反硝化作用，但MLS数据表明，反硝化作用并不完全；也就是说，并非所有极地平流层云(PSC)粒子都从平流层下部沉积出来。在中晚冬期间(尽管气温仍然很低，但总体上正在上升)，465K时HNO3的补充最有可能是通过PSC蒸发和持续的弱非绝热下降实现的。尽管PSC活动和反硝化作用的程度和持续时间在南北半球和年际之间存在很大差异，但在北极和南极，HNO3在每个冬季结束时都会恢复到类似的值。在赤道以北65°的纬度上，即使在冬季，两个半球的纬向平均HNO3值几乎是无法区分的。因此，在冬季和早春，严重的反硝化作用在空间和时间上都局限于65°S以北的地区。
We present an overview of the seasonal, interhemispheric, and interannual variations in the distribution of HNO 3 in the lower stratosphere based on measurements of gas-phase HNO 3 made by the UARS Microwave Limb Sounder (MLS) through six complete annual cycles in both hemispheres. Outside of the winter polar regions, zonal-mean HNO 3 mixing ratios on the 465-K potential temperature surface are comparable in the two hemispheres in all latitude bands and in all years examined. Except at high latitudes, interannual variability is minimal, and there is no significant hemispheric asymmetry in the overall HNO 3 distribution or its seasonal cycle. Although the Antarctic experiences widespread severe denitrification, the MLS data indicate that the denitrification is not complete; that is, not all polar stratospheric cloud (PSC) particles sediment out of the lower stratosphere. Replenishment of HNO 3 at 465 K during the mid- to late-winter period (when temperatures, though still low, are generally rising) is most likely achieved through a combination of PSC evaporation and continuing weak diabatic descent. Despite large interhemispheric and interannual differences in the extent and duration of PSC activity and denitrification, HNO 3 recovers to similar values at the end of every winter in both the Arctic and the Antarctic. Zonal-mean HNO 3 values for the two hemispheres are virtually indistinguishable for the latitudes equatorward of 65°, even during the winter months. Thus the effects of severe denitrification are confined in both space and time to the regions poleward of 65°S during the winter and early spring.