冰雷达探测数据处理方法研究——以南极冰盖Dome A地区的数据处理为例

提出了冰雷达数据处理的流程,详细论述了冰雷达数据处理中常规修正的关键技术：静态校正、增益控制、带通滤波以及偏移处理等。以中国第24次南极科学考察（CHINARE 24）所获取的Dome A 地区30 km×30 km范围冰雷达原始数据处理作为实例,提取得到了该区域冰盖内部等时层埋深以及冰盖的冰厚数据。通过插值展现了冰盖等时层以及冰岩界面的三维空间形态。结合该区域ICESat冰盖表面高程数据,构建出了Dome A地区涵盖冰盖表面、冰盖等时层以及冰岩界面形态特征的三维模型。     

Historical record of metal accumulation and lead source in the southeastern coastal region of Korea

Concentrations of heavy metals and Pb isotopes were measured in the 1-M HCl leaching fraction of core sediments spanning the last 400 years. This sedimentary record of pollution history in metal concentrations shows a good correlation with the increases in industrialization, urbanization, and energy consumption since 1901s. Notably, the Pb concentration and the ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios were constant before the 1910s (16.7 μg/g, 0.844, and 2.098, respectively), whereas they increased steadily up to 21.9 μg/g, 0.848, and 2.101 after the 1910s. The correlations between Pb isotope ratios (²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb) showed different linear regression trends for core sediments before and after the 1910s, indicating differences in Pb sources. Our interpretation suggests that the source of anthropogenic Pb in Korean coastal region and the Yellow Sea shelf was presumed to be Chinese coals or ores, which have also played a major role as sources of atmospheric particulate Pb.     

天文成像数值仿真的相位屏模拟方法

通过利用Monte—Carlo方法对湍流相位屏模拟进行验证和分析。给出加入次谐低频补偿相位屏与直接谱反演相位屏的对比结果,并分析了在考虑内外尺度时次谐低频补偿方法的有效性。此外,给出了基于天文观测的多相位屏的湍流分层模型。在此基础上对天文成像进行数值仿真,并给出了仿真结果。     

2008年初武汉冰雪天气过程特征分析

利用实况观测资料和NCEP再分析资料对2008年初武汉市4次冰雪天气过程特征进行分析。结果表明：700—850 hPa的逆温与850 hPa以下层次的冷垫是该区降雪发生与维持的有利条件,700 hPa切变线偏在850 hPa切变线北方,风的垂直切变表明大气具有明显的斜压性,较高层次强大的西南气流在较低层次冷垫上输送大量暖湿空气。本区18日20时—19日20时暴雪发生时有较强的上升运动和较大的西南水汽输送与水汽辐合,最大西南水汽输送与水汽辐合的层次比一般暴雨过程要高,高层惯性不稳定、中层对流不稳定等都是暴雪发生的有利条件。     

Observing Forbush decreases in cloud atShetland

Meteorological measurements from Lerwick Observatory, Shetland (60°09′N, 1°08′W), are compared with short-term changes in Climax neutron counter cosmic ray measurements. For transient neutron count reductions of 10–12%, broken cloud becomes at least 10% more frequent on the neutron minimum day, above expectations from sampling. This suggests a rapid timescale (～1 day) cloud response to cosmic ray changes. However, larger or smaller neutron count reductions do not coincide with cloud responses exceeding sampling effects. Larger events are too rare to provide a robust signal above the sampling noise. Smaller events are too weak to be observed above the natural variability.     

Mass loss from “Hot Jupiters”—Implications for CoRoT discoveries, Part II: Long time thermal atmospheric evaporation modeling

We investigate the efficiency of the atmospheric mass loss due to hydrodynamic blow-off over the lifetime of the exoplanet HD209458b by studying numerically its hydrogen wind for host star X-ray and EUV (XUV) fluxes between 1 and 100 times that of the present Sun. We apply a time-dependent numerical algorithm which is able to solve the system of hydrodynamic equations straight through the transonic point of the flow including Roche lobe effects. The mass loss rates are calculated as functions of the absorbed energy in the thermosphere. Depending on the heating efficiency for a hydrogen-rich thermosphere the maximum temperature obtained in our study at 1.5R_pl by neglecting IR cooling is about 5000-10,000 K for heating efficiencies of 10% and 60%, respectively. We find that the upper atmosphere of HD209458b experiences hydrodynamic blow-off even at such low temperatures if one does not neglect gravitational effects caused by the proximity of the planet to its Roche lobe boundary. Depending on the heating efficiency, we find from the solution of the hydrodynamic equations of mass, momentum, and energy balance that energy-limited mass loss rate estimations overestimate the realistic mass loss rate at present time for HD209458b by several times. Using the maximum heating efficiency for hydrogen-rich atmospheres of 60% we find that HD209458b may experience an atmospheric mass loss rate at present time of about . The mass loss rate evolves to higher values for higher XUV fluxes expected during the early period of the planet's host star evolution, reaching values of several times . The integrated mass loss is found to be between 1.8% and 4.4% of the present mass of HD209458b. We found that the influence of the stellar tidal forces on atmospheric loss (the Roche lobe effect) is not significant at 0.045 AU. For a similar exoplanet, but at closer orbital distances , the combined effect of the Roche lobe and the high XUV radiation result in much higher thermal loss rates of about and even more for early stages. This leads to a total loss over 4 Gyr of 27.5% of the planetary mass.     

Effect of charging of aerosols in the lower atmosphere of Mars during the dust storm of 2001

Aerosols are very important in the Martian climate system. Aerosols get charged by the attachment of ions in the atmosphere. Charging of aerosols reduces the conductivity of the atmosphere as the very mobile ions are lost during the ion-aerosol attachment. During a dust storm the dust opacity increases and more ion-aerosol attachment process occurs and consequently conductivity reduces further. It was found that with the background aerosols (dust opacity ∼0.2), the conductivity close to the surface of Mars was reduced by a factor of 5, but during the dust storm (opacity ∼5) of 2001 the conductivity decreased by about 2 orders of magnitude.     

EUV resonance fluorescence of the c′4→X (0,v″) and b′→X (1,v″) transitions of N2

Extreme ultraviolet (EUV) resonance fluorescence of the (0,v″) bands of the c′₄¹Σ_u⁺→X¹Σ_g⁺ and the (1,v″) bands of the b′ ¹Σ_u⁺→X¹Σ_g⁺ transitions of N₂ has been observed by photon excitation of N₂ in the vicinity of 95.8 nm. The integrated fluorescence intensities of the c′₄→X (0,v″) emission become saturated at N₂ pressures higher than ∼0.16 mTorr. The emission features in the spectral region between 105 and 130 nm become progressively significant as the N₂ pressure is increased. The (1,v″) progression for v″ up to 11 of the b′→X transition and two progressions of the Lyman-Birge-Hopfield (LBH) system have been identified. The multiple scattering processes apparently cause significant reduction in the c′₄→X (0,0) emission rates. The present results may be useful in the explanation of the weak c′₄→X (0,0) fluorescence as well as the significant c′₄→X (0,v″) features in the dayglow of the Earth observed by the Far Ultraviolet Spectroscopic Explorer.     

中国大陆下扬子及邻区地壳结构基本特征:深地震测深研究综述

系统回顾了20世纪70年代以来在中国大陆下扬子及其邻区开展的深地震测深工程,总结了相关宽角反射/折射地震资料的波组特征及地壳结构的基本特征。下扬子及邻区深地震测深资料普遍具有较清晰的初至震波Pg、上地壳底界面反射波P1、中地壳底界面反射波P3、莫霍界面反射波Pm及上地幔顶部首波Pn,震相连续,易追踪对比。受浅表沉积盖层或基岩等的影响,Pg波常出现局部延迟滞后或走时超前现象。尤其是大别造山带个别炮点的反射能量较弱或同相轴扭曲、波形紊乱等,均与地壳内界面和莫霍面的深度突变或破碎有关。该区域地壳结构大致分为上、中、下3层,但视资料情况中地壳和下地壳又可进一步划分为2个亚层。华北地台和扬子地台地壳厚度30~36km,莫霍界面形态变化较缓,存在局部隆起,下地壳平均速度6.7±0.3km/s。但大别造山带下方地壳厚度32~41km,莫霍界面下凹且出现4~7km垂向错断,下地壳平均速度6.8±0.2km/s。     

Embedding complex hydrology in the regional climate system – Dynamic coupling across different modelling domains

To improve our understanding of the impacts of feedback between the atmosphere and the terrestrial water cycle including groundwater and to improve the integration of water resource management modelling for climate adaption we have developed a dynamically coupled climate–hydrological modelling system. The OpenMI modelling interface is used to couple a comprehensive hydrological modelling system, MIKE SHE running on personal computers, and a regional climate modelling system, HIRHAM running on a high performance computing platform. The coupled model enables two-way interaction between the atmosphere and the groundwater via the land surface and can represent the lateral movement of water in both the surface and subsurface and their interactions, not normally accounted for in climate models. Meso-scale processes are important for climate in general and rainfall in particular. Hydrological impacts are assessed at the catchment scale, the most important scale for water management. Feedback between groundwater, the land surface and the atmosphere occurs across a range of scales. Recognising this, the coupling was developed to allow dynamic exchange of water and energy at the catchment scale embedded within a larger meso-scale modelling domain. We present the coupling methodology used and describe the challenges in representing the exchanges between models and across scales. The coupled model is applied to one-way and two-way coupled simulations for a managed groundwater-dominated catchment, the Skjern River, Denmark. These coupled model simulations are evaluated against field observations and then compared with uncoupled climate and hydrological model simulations. Exploratory simulations show significant differences, particularly in the summer for precipitation and evapotranspiration the coupled model including groundwater and the RCM where groundwater is neglected. However, the resulting differences in the net precipitation and the catchment runoff in this groundwater dominated catchment were small. The need for further decadal scale simulations to understand the differences and insensitivity is highlighted.