The influence of PMCs on water vapor and drivers behind PMC variability from SOFIE observations
The influence of PMCs on water vapor and drivers behind PMC variability from SOFIE observations
复制标题
DOI：
10.1016/j.jastp.2015.07.010
复制
发表时间：
2015-09
影响因子：
1.9
通讯作者：
M. Hervig;D. Siskind;S. Bailey;J. Russell
中科院分区：
文献类型：
--
作者：
M. Hervig;D. Siskind;S. Bailey;J. Russell
太阳掩星冰实验（SOFIE）的观测数据被用来量化极地中间层云（PMC）和它们的环境之间的关系。由于冰的生长脱水被认为是最大的平均冰质量密度峰值以上的高度为1.8公里，和H2O的增强由于升华是最大的PMC层的底部附近。脱水层和水化层含有相似量的H2O，尽管比在冰层中发现的要少，这一差异可能是由于对流输送。由于PMCs改变周围的水蒸气，PMC-H2O的关系可能是误导性的，建议处理这个问题。PMCs对水汽和温度的依赖性被量化，解释了冰对水汽的影响。该方法检查了年际变化，并考虑了太阳反向散射紫外线（SBUV）仪器检测到的PMCs子集，这些仪器的灵敏度低于SOFIE。在北方的结果表明，PMC的变化主要是由温度，但温度和水汽的组合提供了最好的解释的意见。在南半球，PMC的变化主要归因于温度，水汽起次要作用。SBUV PMC的子集被发现是三分之一的敏感性变化的温度作为整个PMC人口观察SOFIE。最后，提出了一种方法，它允许温度和水汽异常估计从各种PMC数据集，如SBUV。使用最近报道的64-74°N纬度的SBUV PMC趋势和本研究的结果表明，冷却趋势为-0.27 ±0.14 K十年-1，水汽增加+0.66 0. 34%十年-1（均在80-84 km处）。这种冷却趋势与基于类似纬度中层大气观测的报告一致。由于甲烷的增加，水蒸气的增加低于预期，尽管这种差异可能与PMC高度光解引起的H2O损失一致。
Observations from the Solar Occultation For Ice Experiment (SOFIE) are used to quantify relationships between polar mesospheric clouds (PMC) and their environment. Dehydration due to ice growth is found to be greatest ∼1.8 km above the height of peak ice mass density on average, and H2O enhancement due to sublimation is greatest near the bottom of the PMC layer. The dehydration and hydration layers contain a similar amount of H2O, although less than is found in ice layers, a difference that may be due to meridional transport. Because PMCs modify the surrounding water vapor, PMC–H2O relationships can be misleading and recommendations are made for dealing with this issue. The dependence of PMCs on water vapor and temperature was quantified, accounting for the effects of ice on water vapor. The approach examined inter-annual variations and considered the subset of PMCs detected by the Solar Backscatter Ultraviolet (SBUV) instruments, which are less sensitive than SOFIE. Results in the Northern Hemisphere indicate that PMC variations are dominated by temperature, but that a combination of temperature and water vapor provides the best explanation of the observations. In the Southern Hemisphere PMC variability is attributed primarily to temperature, with water vapor playing a minor role. The subset of SBUV PMCs are found to be one third as sensitive to changing temperature as the entire PMC population observed by SOFIE. Finally, an approach is presented which allows temperature and water vapor anomalies to be estimated from various PMC data sets such as SBUV. Using recently reported SBUV PMC trends at 64–74°N latitude with the results of this study indicates a cooling trend of −0.27±0.14 K decade−1and a water vapor increase of +0.66±0.34% decade−1(both at 80–84 km). This cooling trend agrees with reports based on observations in the middle atmosphere at similar latitudes. The water vapor increase is lower than expected due to increasing methane, although this difference may be consistent with H2O loss due to photolysis at PMC altitudes.