Impact of planetary waves and solar proton events on long-term variations of noctilucent clouds II

两半球的极地夏季中层顶区的特点是反复出现被称为夜光云(NLCS)或极地中层云(PMC)的光学薄H2O云。在最近的过去，许多研究小组对NLC进行了深入的研究，主要是因为这些云可能是全球变化的早期指标。然而，所提出的导致NLCS长期变化的机制，即二氧化碳增加辐射冷却导致的负温度趋势和CH4氧化引起的中间层上层H2O的正趋势的有效性尚未得到令人信服的证明。此外，还有其他几个过程和机制可能会在NLCS中引入长期和太阳周期变化。这个项目旨在提高我们对其他几个过程的了解，这些过程可能对非传染性疾病的地理分布及其长期变化产生重大影响，但人们对这些过程的了解很少或根本不了解。这些过程是：(A)NLCS的行星波扰动，(B)太阳高能粒子的预沉，(C)太阳辐照度的短期变化，以及(D)最近发现的影响极地夏季中层顶热条件的半球间耦合过程。这些过程驱动了NLCS的强烈可变性，并将利用一套关于NLCS、中等大气温度和H2O丰度的卫星观测(SBUV、SCIAMACHY/ENVISAT、OSIRIS/ODIN、OMI/AURA)进行研究(MLS/AURA、SABER/TIMED、SCIAMACHY/EVISAT)。与不同的CAWSES和非CAWSES合作伙伴合作，将特别使用太阳质子事件的化学、热和动力学效应的模型模拟，以提高我们对太阳质子事件期间和之后导致NLC耗尽的物理机制的理解。

The polar summer mesopause regions in both hemispheres feature the recurring occurrence of optically thin H2O clouds known as noctilucent clouds (NLCs) or polar mesospheric clouds (PMCs). NLCs were studied intensively by many groups in the recent past, mainly because these clouds are potentially early indicators of global change. However, the validity of the proposed mechanisms leading to long-term changes in NLCs, i.e., a negative temperature trend due to increased radiative cooling by CO2 and a positive trend in upper mesospheric H2O caused by CH4 oxidation was not yet demonstrated convincingly. Moreover, there are several other processes and mechanisms that may introduce long-term and solar cycle variations in NLCs. This project aims at improving our understanding of several of these other processes that may have a significant impact on the geographical distribution of NLCs and their long-term variation, but which are only poorly understood or not understood at all. These processes are (a) planetary wave perturbations of NLCs, (b) pre- cipitation of solar energetic particles, (c) short-term variations in solar irradiance, and (d) recently discovered interhemispheric coupling processes affecting the thermal conditions at the polar summer mesopause. These processes drive the strong variability in NLCs and will be studied using a suite of satellite observations (SBUV, SCIAMACHY/Envisat, OSIRIS/Odin, OMI/Aura) of NLCs, middle atmospheric temperature and H2O abundance (MLS/Aura, SABER/TIMED, SCIAMACHY/Envisat). In collaboration with different CAWSES and non-CAWSES partners model simulations of chemical, thermal and dynamical effects of solar proton events will be used in particular to improve our understanding of the physical mechanisms leading to NLC depletion during and after solar proton events.