Noctilucent Clouds (NLC) and Mesospheric Summer Echoes (MSE) are ice-related phenomena that occur occasionally in the mid-latitude summer mesopause region and more frequently in the polar regions. We observe both phenomena above our site at Kühlungsborn (Germany, 54.1°N, 11.8°E) by lidar and radar since 1997 and 1998, respectively. The NLC season 2019 turned out to be record-breaking with respect to different parameters. We observed the brightest NLC (backscatter coefficient at 532 nm of ${\beta }_{\text{max}}\approx 54\cdot {10}^{-10}{m}^{-1}s{r}^{-1}$ ), the longest continuous NLC ($~$11 h) and the largest occurrence rates in June ($~$20%). The seasonally averaged NLC height was found 600 m lower in altitude in 2019 compared to our long-term record. Consistent with the NLC data, radar observations of MSE showed unusually long-lasting echoes and a higher occurrence rate in June 2019. In contrast to our initial expectations, this increase of ice abundance in 2019 was not related to a generally stronger advection from higher latitudes. Mean winds observed by a nearby meteor radar were essentially weaker than in previous years, even though the winds were still typically southward during NLC. Instead, we found unusually low mean temperatures below 83 km altitude (and down to 75 km) being the main reason for these extraordinary observations. Furthermore, water vapor concentrations were slightly enhanced in June 2019. Low temperatures and enhanced water vapor may be caused by stronger upwelling in the upper mesosphere. However, there is no vertical wind data available. Low solar activity was also a factor that promoted these good NLC conditions. Overall, we judge this a singular event and not as an indicator for climate change. Temperature data in the mesopause region and below are taken from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on NASA's Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellite as well as Earth Observing System (EOS) Microwave Limb Sounder (MLS) onboard NASA's Aura satellite.

夜光云（NLC）和中层夏季回声（MSE）是与冰有关的现象，偶尔发生在中纬度夏季中段更年期地区，更经常出现在极地地区。自1997年和1998年以来，我们分别通过激光雷达和雷达观测到了位于库伦斯博恩（德国，54.1°N，11.8°E）站点上方的两种现象。事实证明，2019年NLC赛季在不同参数方面打破了纪录。我们观察到最亮的NLC（在532 nm处的背向散射系数${\beta }_{\text{最大限度}}\approx 54\cdot {10}^{-10}{米}^{--\mathrm{1个}}s{\mathrm{[R}}^{--\mathrm{1个}}$ ），最长的连续NLC（$〜$11 h），而六月份的发生率最高（$〜$20％）。与我们的长期记录相比，2019年的季节性平均NLC高度低600 m。与NLC数据一致，MSE的雷达观测显示异常长久的回波和2019年6月的较高发生率。与我们最初的预期相反，2019年冰量的增加与较高纬度对流对流的普遍增强无关。尽管在NLC期间通常仍偏南，但附近的流星雷达观测到的平均风基本上比前几年弱。取而代之的是，我们发现平均气温低于83 km（低于75 km）的异常低是造成这些异常观测的主要原因。此外，2019年6月水蒸气浓度略有增加。较低的温度和水蒸气的增加可能是由上层中层上层较强的上升流造成的。但是，没有可用的垂直风数据。太阳活动强度低也是促进这些良好的NLC条件的因素。总体而言，我们认为这是一个单一事件，而不是气候变化的指标。中途停泊区及以下的温度数据取自NASA热球电离层中层能动动力学（TIMED）卫星上的宽带发射辐射测量（SABER）以及NASA上的地球观测系统（EOS）微波探空仪（MLS）光环卫星。我们认为这是单个事件，而不是气候变化的指标。中途停泊区及以下的温度数据取自NASA热球电离层中层能动动力学（TIMED）卫星上的宽带发射辐射测量（SABER）以及NASA上的地球观测系统（EOS）微波探空仪（MLS）光环卫星。我们认为这是单个事件，而不是气候变化的指标。中途停泊区及以下的温度数据取自NASA热球电离层中层能动动力学（TIMED）卫星上的宽带发射辐射测量（SABER）以及NASA上的地球观测系统（EOS）微波探空仪（MLS）光环卫星。