Temperatures, polar mesosphere summer echoes, and noctilucent clouds over Spitsbergen (78°N)
Temperatures, polar mesosphere summer echoes, and noctilucent clouds over Spitsbergen (78°N)
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斯匹次卑尔根岛 (78°N) 上空的气温、极地中间层夏季回声和夜光云
DOI：
10.1029/2003jd004247
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发表时间：
2004
影响因子：
--
通讯作者：
J. Röttger
中科院分区：
文献类型：
--
作者：
F. Lübken;M. Zecha;J. Höffner;J. Röttger
[1]在2001年夏季的中大气观测（ROMA）中，在极帽（78°N）同时测量了温度、极地中间层夏季回波（PMSE）和夜光云（NLC）。从罗姆人运动开始和之前（7月中旬）到8月中旬，几乎一直观察到PMSE，到8月底就消失了。PMSE发生在81至92公里之间，但最大发生率在83至89公里之间（每天高达80%）。PMSE与落球温度、霜点温度（Tf）和饱和度(S)进行了比较。PMSE几乎只发生在过饱和的高度，但反之则不然。PMSE层内的温度可达低于Tf的20-25 K。雷达回波功率与S震级之间没有相关性。在中层顶附近，我们经常发现在确认无PMSE的高度S值显著大于1（高达13000）。这可能表明实际的水汽混合比根据“冻干效应”大大小于我们假设的模型值。所有NLC峰海拔的平均值为83.6 km（变率为±1.1 km），在夏季主要季节发生率为77%。在大多数情况下，PMSE和NLC的下边缘分布在几百米或更短的范围内，这可以用冰粒的快速蒸发来解释。这种密切的一致也表明，在几公里以下的尺度上，冰粒子的水平分布相当均匀。PMSE的季节和高度变化与S >1的时间/高度变化范围很好地吻合，证实了足够低的温度对PMSE的存在至关重要。NLC的变化也与S的季节变化一致，但只覆盖过饱和的较低高度范围，这与NLC和PMSE对颗粒半径的不同敏感性相一致。根据PMSE和NLC的联合观测，推导出中性空气湍流的平均发生率大于~ 50%。斯匹次卑尔根岛的实验结果证实了PMSE和NLC的标准情景，即粒子在中层顶周围开始成核，然后生长和沉积，直到它们到达82公里左右的“温暖”大气区域，在那里它们迅速蒸发。小冰粒可以影响等离子体，导致PMSE，而它们需要生长到半径大于大约20纳米才能被激光雷达看到。
[1] Simultaneous measurements of temperatures, polar mesosphere summer echoes (PMSE), and noctilucent clouds (NLC) took place in the polar cap (78°N) during the Rocketborne Observations in the Middle Atmosphere campaign (ROMA) in summer 2001. PMSE were observed practically permanently from the beginning and prior to the ROMA campaign (mid-July) until mid-August and disappeared by the end of August. PMSE occur between 81 and 92 km but have maximum occurrence rates between 83 and 89 km (up to 80% per day). PMSE are compared with temperatures from falling spheres, with frost point temperatures (Tf), and with degrees of saturation (S) using water vapor mixing ratios from models. PMSE occur nearly exclusively at altitudes with supersaturation, but the reverse is not true. Temperatures within PMSE layers can be up to 20–25 K below Tf. There is no correlation between the radar echo power and the magnitude of S. Around the mesopause we frequently find S values significantly larger than 1 (up to 13000) at altitudes with the confirmed absence of PMSE. This could indicate that the actual water vapor mixing ratio is substantially smaller than our assumed model values in line with the “freeze-drying effect.” The mean of all NLC peak altitudes is 83.6 km (variability: ±1.1 km), and the occurrence rate is 77% in the main summer season. Most of the time the lower edges of PMSE and NLC are colocated within a few hundred meters or less, which can be explained by a rapid evaporation of ice particles. This close agreement also indicates a rather homogeneous horizontal distribution of ice particles at scales below a few kilometers. The seasonal and height variation of PMSE nicely agrees with the time/height range of S > 1 and confirms the overwhelming importance of low enough temperatures for the existence of PMSE. The variation of NLC also agrees with the seasonal variation of S but covers only the lower height range with supersaturation in line with the different sensitivity of NLC and PMSE on particle radius. From the combined observations of PMSE and NLC, mean occurrence rates of neutral air turbulence of larger than ∼50% are deduced. The experimental results at Spitsbergen confirm the standard scenario of PMSE and NLC, namely that particles start to nucleate around the mesopause, and grow and sediment until they reach “warm” atmospheric regions around 82 km where they quickly evaporate. Small ice particles can affect the plasma leading to PMSE, whereas they need to grow to radii larger than approximately 20 nm to be seen by lidar.