青藏高原东北缘深地震测深震相研究与地壳细结构

通过对青藏高原东北缘不同构造单元深地震测深资料震相的综合分析,利用反射率理论地震图方法对实际记录模拟计算,进一步研究东北缘区域内部不同构造单元地壳细结构.结果显示：西秦岭褶皱造山带分隔了南北不同性质的地壳结构,北侧为相对稳定的临夏—兰州新生代盆地、南侧为强烈改造的松潘—甘孜地块;松潘—甘孜地块在青藏高原东北缘的构造演化过程中改造为萎缩的若尔盖高原盆地和盆地边缘褶皱造山两类不同的地壳结构;青藏高原东北缘中下地壳普遍存在以多层高低速相间、低速度结构为主的破碎松弛结构,这种特征在缝合带和造山带尤为明显,显示为地壳形变增厚、流变滑动的重要场所;结合二维速度结构及GPS研究结果,对青藏高原东北缘地壳形变及动力学过程进行了讨论.     

Impact of the Bergeron–Findeisen process on the release of aerosol particles during the evolution of cloud ice

The paper focuses on the redistribution of aerosol particles (APs) during the artificial nucleation and subsequent growth of ice crystals in a supercooled cloud. A significant number of the supercooled cloud droplets during icing periods (seeding agents: C₃H₈, CO₂) did not freeze as was presumed prior to the experiment but instead evaporated. The net mass flux of water vapour from the evaporating droplets to the nucleating ice crystals (Bergeron–Findeisen mechanism) led to the release of residual particles that simultaneously appeared in the interstitial phase. The strong decrease of the droplet residuals confirms the nucleation of ice particles on seeding germs without natural aerosol particles serving as ice nuclei. As the number of residual particles during the seedings did not drop to zero, other processes such as heterogeneous ice nucleation, spontaneous freezing, entrainment of supercooled droplets and diffusion to the created particle-free ice germs must have contributed to the experimental findings. During the icing periods, residual mass concentrations in the condensed phase dropped by a factor of 1.1–6.7, as compared to the unperturbed supercooled cloud. As the Bergeron–Findeisen process also occurs without artificial seeding in the atmosphere, this study demonstrated that the hydrometeors in mixed-phase clouds might be much cleaner than anticipated for the simple freezing process of supercooled droplets in tropospheric mid latitude clouds.     

南亚和东亚热带夏季风强弱不同配置及其对中国夏季降水的影响北大核心

利用NOAA向外长波辐射(OLR)、NCEP/NCAR再分析资料和CN05.1降水资料,研究了南亚和东亚热带夏季风强度年际变化关系,及其强弱不同配置对中国夏季降水的影响。结果表明:南亚和东亚热带夏季风强度变化之间存在同相和反相两种配置,定义的强度同相和反相变化指数可以很好地表征该关系。同相变化模态可能与海温异常时的强El Nino(La Nina)影响有关,其反相变化模态受El Nino(La Nina)以及印度洋海盆一致模的影响,同时西太平洋副热带高压和伊朗高压位置东西偏移和强度变化也影响着不同配置的出现。两者不同配置时,对中国夏季降水的影响不同。当变化呈同相偏强时,夏季中国东部地区降水为“中间少南北多”的雨型。当变化呈反相,东亚热带夏季风偏强南亚夏季风偏弱时,夏季中国东部地区降水为“一致偏少”雨型。