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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Structure of the mesospheric Na layer at 40 deg N latitude: Seasonal and diurnal variations
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Structure of the mesospheric Na layer at 40 deg N latitude: Seasonal and diurnal variations

机译：北纬40度的中层Na层的结构：季节性和昼夜变化

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摘要

Lidar observations obtained throughout the diurnal and annual cycles at Urbana, Illinois (40 deg N, 88 deg W), are used to examine the structure of mesospheric Na between 76 and 108 km. The Na layer is strongly influenced by seasonal and diurnal variations in solar illumination and by seasonal variations of mesospheric temperatures. Although there is little evidence of direct tidal perturbations in Na density, 24 hour oscillations dominate the diurnal variations. Na abundance and densities above 90 km are controlled by photoionization and charge exchange reactions during the day and recombination at night. The abundance is maximum at sunrise, and the peak-to-peak diurnal variation averages more than 30%. Below 85 km, density variations are controlled by photochemistry which interrupts the conversion of Na to the bicarbonate reservoir, and by warmer temperatures which enhance the liberation of Na from the reservoir. In this region the peak-to-peak diurnal Na variations can exceed 200%. The combined effects of photoionization above 90 km and photochemistry below 85 km induce a strong 24 hour oscillation in the layer centroid height. The peak-to-peak variation exceeds 1 km. The lowest centroid height is at local noon when Na densities below 85 km are maximum and photoionization above 90 km is strongest. The seasonal variations in Na densities and abundance are influenced primarily by changes in mesopause region temperatures which are coldest during midsummer. Below 95 km, reactions leading to the bicarbonate sink and the liberation of Na from this reservoir dominate Na chemistry. These reactions and their temperature dependencies are responsible for the large annual variation in Na abundance (2.3 * 10~9 to 5.3 * 10~9 cm~(-2)). The measured correlation between Na abundance and the layer weighted temperature is + 0.89. The ratio of the abundance to temperature variations is 1.9 * 10~8 cm~(-2) k~(-1). The seasonal Na density and temperature perturbations are well-correlated (+ 0.6 to + 0.9) below 98 km and negatively correlated above (- 0.2 to - 0.5).
机译：在伊利诺伊州厄班纳（40度北，西纬88度）的整个昼夜和年度周期获得的激光雷达观测数据被用于检查76至108 km之间的中层钠的结构。 Na层受到太阳照度的季节性和昼夜变化以及中层温度的季节性变化的强烈影响。尽管几乎没有直接的潮汐显示Na浓度扰动，但24小时的振荡主导了昼夜变化。 Na的丰度和90 km以上的密度受白天的光电离和电荷交换反应以及晚上的重组控制。日出时丰度最大，峰峰值日平均变化超过30％。在85公里以下，密度变化受到光化学的控制，光化学阻止了Na向碳酸氢盐储层的转化，而温度升高则促使Na从储层中释放出来。在该区域，峰钠峰值日变化可以超过200％。高于90 km的光电离和低于85 km的光化学的综合作用会在层质心高度产生强烈的24小时振荡。峰峰值变化超过1 km。最低的质心高度是在当地正午时，Na密度低于85 km时最大，而90 km以上的光电离最强。 Na密度和丰度的季节性变化主要受中暑区域温度变化的影响，该温度在仲夏期间最冷。在95 km以下，导致碳酸氢盐下沉和从该储层中释放出Na的反应主导着Na的化学反应。这些反应及其温度依赖性是造成Na丰度年变化较大的原因（2.3 * 10〜9至5.3 * 10〜9 cm〜（-2））。 Na丰度与层加权温度之间的相关系数为+ 0.89。丰度与温度变化之比为1.9 * 10〜8 cm〜（-2）k〜（-1）。在98 km以下，季节性的Na浓度和温度扰动具有良好的相关性（+ 0.6至+ 0.9），而在98 km以下的季节中，其Na相关性呈负相关（-0.2至-0.5）。

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