A quarter-century of satellite polar mesospheric cloud observations
A quarter-century of satellite polar mesospheric cloud observations
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DOI：
10.1016/j.jastp.2005.08.003
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发表时间：
2006
影响因子：
1.9
通讯作者：
M. DeLand;E. Shettle;G. Thomas;J. Olivero
中科院分区：
文献类型：
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作者：
M. DeLand;E. Shettle;G. Thomas;J. Olivero
极地中层云（PMC）的卫星观测是非常有价值的，因为它们通常有每日的覆盖范围来描述季节变化，每个季节都有足够的探测来提供良好的统计数据，物理分析的定量信息，以及两个半球的覆盖范围来评估全球行为。紫外线连续光谱测量提供了有关颗粒尺寸分布的信息。一个典型的PMC季节在夏至前约20天开始，在80°纬度，发生频率迅速上升到80- 90%，并保持在该水平，直到夏至后50-60天。出现的频率和亮度都与纬度有关，在两极观察到更高的值。PMC通常在82- 83公里的高度观察到，在每个季节的开始和结束时都有更高的高度。还观察到行为的半球差异。北方半球的PMC始终比南半球的云更频繁和更明亮。云的高度通常与云的亮度呈反相关。卫星提供的扩展PMC数据集的可用性提供了评估过去几十年PMC长期变化的机会。对这些冗长的数据集的分析表明，在过去两个太阳活动周期中，季节平均PMC参数（发生频率和亮度）与太阳紫外线活动之间存在明显的反相关性，与模型预测一致。在几个数据集中，太阳活动周期和PMC响应之间存在101年的时滞（太阳变化导致PMC响应）。原因不明。多元回归分析还表明，发生频率和亮度都长期增加，尽管对增加的幅度尚未达成共识。这些结果进行了比较，在合理的源机制，如中层水汽和温度的并发变化的信息。
Satellite observations of polar mesospheric clouds (PMCs) are extremely valuable because they typically have daily coverage to characterize seasonal variations, sufficient detections for each season to give good statistics, quantitative information for physical analysis, and coverage of both hemispheres to evaluate global behavior. Continuous spectral measurements in the ultraviolet provide information about particle size distributions. A typical PMC season begins approximately 20 days before summer solstice at 80° latitude, rises rapidly in occurrence frequency to 80–90%, and remains at that level until 50–60 days after solstice. Both occurrence frequency and brightness are latitude dependent, with higher values observed toward the poles. PMCs are normally observed at altitudes of 82–83km, with higher altitudes at the start and end of each season. Hemispheric differences in behavior are also observed. Northern Hemisphere PMCs are consistently both more frequent and brighter than Southern Hemisphere clouds. Cloud height is generally anti-correlated with cloud brightness. The availability of extended PMC data sets from satellites provides the opportunity to evaluate long-term PMC variations over the past few decades. Analysis of these lengthy data sets shows a clear anti-correlation between seasonally averaged PMC parameters (occurrence frequency and brightness) and solar UV activity over the past two solar cycles, in agreement with model predictions. A time lag of ∼1 year between the solar cycle and the PMC response is present in several data sets (solar variation leads PMC response). The cause is unknown. Multiple regression analysis also indicates long-term increases in both occurrence frequency and brightness, although there is not yet a consensus on the magnitude of the increase. These results are compared with information about concurrent variations in plausible source mechanisms such as mesospheric water vapor and temperature.