A numerical study of the interaction between two simultaneous storms: Goni and Morakot in September 2009

Significant anomalous tracks were observed when the severe tropical storm Goni(0907) and typhoon Morakot(0908) in September 2009 were evaluated in short distances.The relationship between the two is regarded as a case of binary interaction.Based on an MM5 model(fifth-generation mesoscale model of Pennsylvania State University-National Center for Atmospheric Research),in this study a series of sensitivity experiments were designed to determine the binary interaction between them.The sensitivity of the storm characteristics to the binary interaction was demonstrated through modeling experiments with different TC intensities and sizes based on the bogus vortices initialization.Furthermore,the contributions of large-scale environmental flow and the effects of interaction between the motions of the cyclones were distinguished by numerical experiments using only one of the TC vortices.Results from these experiments show that Morakot(0908) had a greater impact on the motion of Goni(0907),whereas Goni(0907) had a relatively limited impact on Morakot(0908).At the upper level,the northeasterly jet flow in the third quadrant of Morakot(0908) enhanced the upper-level divergence of Goni(0907) and had an important role in maintaining and increasing Goni’s(0907) intensity.And at the lower level,Morakot(0908),with strong convergence and ascending airflow,made a stable transport channel of southwesterly warm and wet flow,thus supporting the lower-level water vapor convergence of Goni(0907).Goni(0907),which was located upriver of the southwesterly flow,intercepted part of the water vapor transportation in the southwesterly flow,causing the water vapor convergence to strengthen while the water vapor convergence of Morakot(0908) weakened.     

中国北方陆相沉积5.30Ma磁性地层序列

本文通过中国北方新第三纪晚期典型剖面的磁性地层研究,建立５．３０Ｍａ以来中国北方陆相沉积积磁性地层序列。中国黄土记录了Ｂｒｕｎｈｅｓ正极性带与Ｍａｔｕｙａｍａ负极性带,年龄约２．５０Ｍａ。静乐红土（包括静乐剖面,榆林剖面,蓝田剖面）对应于Ｇａｕｓｓ正极性带与Ｇｉｌｂｅｒｔ负极性带,年龄约２．５０￣５．３０Ｍａ。三门组记录了Ｍａｔｕｙａｍａ负极性带下段,年龄约１．２０￣２．５０Ｍａ。游河组记录了Ｇａ     

地震动持时的研究进展

地震动持时作为表征地震动的三要素之一,其对震害的影响逐渐被人们所认识.然而,在地震动持时的定义方面,目前没有统一且明确的概念,文中给出了广义的地震动总持时和强震持时的定义,研究者们根据各自领域的研究特点选择更适合的持时.持时大致可以分为两个大类:一是绝对持时,即基于加速度绝对值阈值的括号持时;二是相对持时,也就是反映地震动过程强度或能量变化趋势的持时,比如能量控制的相对持时等.持时的定义有很多种,文章简单地回顾了地震动持时的五种定义,同时,细致地分析了五种持时定义所表现的特点,并介绍了持时预测模型的研究成果,最后针对目前应用持时存在的问题提出了几点认识.     

1983年日全食光谱的强度和高度定标

本文详细介绍了1983年日食光谱资料的强度和高度定标方法和结果,并讨论了其精度.对同一波段,用两种不同的绝对定标方法得出的结果基本一致,说明定标是可靠的.文中还给出了二切无缝谱色球底的位置,并计算了该区的温度.     

太阳紫外高分辨观测

对近年来的紫外空间观测仪器（包括在研项目）作了扼要介绍，并对一些关键问题如烃基污染致使仪器灵敏度迅速下降，镜面紫外反射率低下及改进，探测器换代的必要性和困难等作了评述，文中还介绍了目前取得的紫外观测结果对宁静太阳及太阳活动区物理中的一些基本问题如色球和日冕加热，太阳风的加速，色球和过渡区中的物质流以及耀斑触发和能量传输方面所提供的有价值的诊断信息。     

Unusual spectral absorption observed in the 16 August 1989 limb flare

A relative complete set of He I 10830 Å profiles and their coincident slit-jaw Hα images of the large limb flare (2N/X20) of 16 August 1989 were observed by the solar spectrograph at Purple Mountain Observatory. In addition to the unusually broadened spectral profiles observed in the impulsive phase, more than half of the observed He I 10830 Å profiles are characterized by central reversals, which were detected not only in the impulsive phase but also in the late decaying phase. The central-reversed profiles may exist at different heights, ranging from the solar limb to (3–4) × 10⁴ km above. The absorption varies with time and position, with a typical lifetime and size of several minutes and 5–6 arc sec, respectively. Depths of the absorption profiles also change clearly. The absorptions are usually deeper at the loop footpoint near the solar limb and shallower at loop-top. However, the most unusual feature is that all the line-center wavelengths of them show no shift relative to that of the quiet chromosphere near the limb, implying the apparent velocities are zero while the associated emission profiles have different apparent velocities. Theoretical simulations demonstrate that the Doppler widths of the absorptions are in the range of (0.35–0.5)Å and increase with height, and the source functions are (0.11–0.3) times the disk center intensity. However, the absorptions have a relative large range of optical thickness (0.1–1.3) in the I ₃ component of the He I 10830 Å triplet. We have not observed such absorption in other limb flares, including the SB/X2.9 flare of 17 August 1989 that occurred in the same active region as the studied one (NOAA 5629). Our studies show that the absorption could not result from he scattering by the telluric atmosphere or from normal chromospheric absorption. This unique phenomenon may be related to extra intense X-ray flux and caused by diffuse and non uniform materials dissociated from the flare instead of self-absorption of the flare.     

Impulsive Phase He 10830 Spectra of a Large Solar Limb Flare of 16 August 1989*

We obtained simultaneously He i 10830 Å spectra, H filtergrams and microwave data of a large limb flare (2N/X20) in 1989. In this paper we characterize He i 10830 spectra in relation to the impulsive phase. All the He i 10830 spectra, except those of the surge, show blue shift or blue asymmetry. The velocities inferred from the spectra range from a few to 160 km s–1, implying that the horizontal motion is very likely present in the structure of this flare at different heights. The He i 10830 profiles of a flare are relatively broad and cannot be simulated by the Doppler broadening mechanism with a uniform flare model atmosphere. It is most likely that these characteristics are related to rapid and localized heating in the low and middle chromosphere. Comparing the SXR and microwave data with the optical data leads to the following scenario: the corona was already heated to some extent before the flare onset, and in the first 2 minutes of the impulsive phase, heat conduction was the main source or, at least, a competitive source, for chromospheric heating. However, the impulsive event, associated with the unusually broadened He i 10830 line (f>20 Å) and temporally correlated with a microwave burst, is probably caused by electron-beam heating.     

中国西南地区5月降水与阿拉伯海季风关系的年代际变化

本文利用1960～2017年中国西南地区115个台站观测降水资料和日本气象厅发布的55年再分析资料集,研究了中国西南地区5月降水变异的主导模态及其与阿拉伯海季风的关系。结果显示,中国西南地区5月降水的第一主导模态主要表现为全区一致的变异特征;该模态与同期5月阿拉伯海季风强度异常关系密切,但两者的关系在20世纪70年代后期发生了显著的年代际变化。在1960～1976年,阿拉伯海季风异常所引起的低层大气环流和水汽输送异常主要集中在阿拉伯海到孟加拉湾一带;阿拉伯海季风异常所引起的大气环流不能到达中国西南地区,因此它对中国西南地区5月降水的影响偏弱。但在1981～2017年,阿拉伯海季风异常可以导致整个北印度洋到南海地区的大气环流异常,进而引起中国西南地区水汽和垂直运动的变化,最终对该地区5月降水产生显著的影响。进一步的研究显示,阿拉伯海季风与中国西南地区5月降水关系的变化可能与季风自身的年代际变率有关。阿拉伯海季风在20世纪70年代末之前变率偏弱,其引起的环流异常也偏弱;相反在20世纪70年代末之后,其变率增强,它引起的大气环流异常也偏强,可以延伸到中国西南地区,进而影响到西南地区的5月降水。因此,季风变率的强弱可能在季风对西南地区5月降水的影响中起着非常重要的作用。     

Role of natural external forcing factors in modulating the Indian summer monsoon rainfall,the winter North Atlantic Oscillation and their relationship on inter-decadal timescale

We use reconstructed data and multi-centennial integrations performed with the Bergen Climate Model Version 2 to investigate the impact of natural external forcing factors on the Indian summer monsoon (ISM) rainfall, the winter North Atlantic Oscillation (NAO), and the potential relationship between the ISM rainfall and the winter NAO on decadal to inter-decadal timescales. The model simulations include a 600-year control integration (CTL600) and a 600-year integration with time-varied natural external forcing factors from 1400 to 1999 (EXT600). Both reconstructed data and the simulation showed increased ISM rainfall 2–3 years after strong volcanic eruptions. Strong volcanic eruptions decrease the Indian Ocean sea surface temperature (SST), which increases the strength of the southwesterly winds over the Arabian Sea. With negative externally-forced radiative anomaly, the lower stratospheric pole-to-equator winter temperature gradient is enhanced, leading to a positive winter NAO anomaly with a time lag of 1 year. There is no significant correlation between the winter NAO and ISM rainfall in CTL600. However, the ISM rainfall is significantly positively correlated with the winter NAO in EXT600, with the NAO leading by 2–4 years, which is consistent with the NAO–ISM rainfall relationship in the reconstructed data. We suggest that natural external forcing factors regulate the inter-decadal variability of both the winter NAO and the ISM rainfall and thus likely lead to an increased statistical but not causal relationship between them on the inter-decadal timescale over the past centuries.