若尔盖盆地兴措湖沉积记录揭示的近代气候与环境

依据湖泊沉积记录进行古气候环境要素定量的是过去全球变化研究的重要内容,本文通过若尔盖盆地兴措湖近代湖泊沉积特征、沉积物总有机碳及其同位素指标分析,并与器测气象资料进行比较,对兴措湖泊近代湖泊沉积物中有机碳及其同位素指标所代表的气候环境信息进行了定量研究,在此基础上,建立了兴措湖沉积物总有机碳及其同位素记录与对应的降水和气温间的函数关系,为定量恢复该区长尺度历史时期古气候环境特征提供了基础。     

Effects of plate and slab viscosities on the geoid

The effects of plate rheology (strong plate interiors and weak plate margins) and stiff subducted lithosphere (slabs) on the geoid and plate motions, considered jointly, are examined with three-dimensional spherical models of mantle flow. Buoyancy forces are based on the internal distribution of subducted lithosphere estimated from the last 160 Ma of subduction history. While the ratio of the lower mantle/upper mantle viscosity has a strong effect on the long-wavelength geoid, as has been shown before, we find that plate rheology is also significant and that its inclusion yields a better geoid model while simultaneously reproducing basic features of observed plate motion. Slab viscosity can strongly affect the geoid, depending on whether a slab is coupled to the surface. In particular, deep, high-viscosity slabs beneath the northern Pacific that are disconnected from the surface as a result of subduction history produce significant long-wavelength geoid highs that differ from the observation. This suggests that slabs in the lower mantle may be not as stiff as predicted from a simple thermally activated rheology, if the slab model is accurate.     

鲁中地区分类强对流天气环境参量特征分析

将山东中部地区16 a暖季(4-9月)106次伴随瞬时风力不低于8级的强对流个例划分为雷暴大风、冰雹雷暴大风和强降水混合型等3种类型,利用常规探空资料和地面观测资料,通过箱须图的形式分别讨论3种类型对应的一系列关键环境参数的分布特征和预报阈值。进一步,又将上述106次个例中的特强对流个例,包括产生25 m/s以上瞬时大风的特强雷暴大风个例、产生不小于20 mm直径冰雹的特强冰雹个例以及50 mm/h或以上强度的特强短时强降水个例提取出来构成一个子集,讨论其关键环境参数分布特征和预报阈值,并与全部对流个例的相应关键环境参数进行比较。最后,对鲁中地区强对流系统的触发机制进行了简要阐述和讨论。结果表明:(1)雷暴大风型、冰雹雷暴大风型和强降水混合型对应的850和500 hPa温差的最低阈值为25℃; 3种类型对应的地面露点最低阈值分别为13、16和24℃; 相应的大气可降水量最低阈值分别为20、24和32 mm; 相应对流有效位能的最低阈值分别为300、900和1300 J/kg; 相应的0-6 km风垂直切变最低阈值分别为12.0、12.5和8.0 m/s。(2)通过地面露点、大气可降水量以及暖云层厚度等关键参数的分布特征可以将上述3种类型的前两种与第3种类型即强降水混合型进行一定程度的区分,但要通过各个关键参数的分布特征区分前两种强对流天气是困难的。(3)对于伴随冰雹的强对流天气,适宜的融化层高度为3.0-3.9 km; (4)特强雷暴大风、特强冰雹和特强短时强降水等3种特强对流类型与全部强对流个例的3种类型相比,其条件不稳定度明显增大,体现为850和500 hPa温差的增大、水汽条件有所加强、对流有效位能明显增大,3种类型特强对流天气对应的对流有效位能最低阈值分别为1000、1100和2000 J/kg; 相应的0-6 km风垂直切变最低阈值分别为16、12和11 m/s,即特强雷暴大风型和特强短时强降水型的风垂直切变阈值明显增大。上述工作构成了山东中部伴随雷暴大风的强对流天气短时预报的一个基础,结合各类强对流天气发生的气候概率,可以通过决策树或模糊逻辑方法制作成适合于地、市气象台的分类强对流天气短时预报系统。      

激光雷达与微波辐射计联合观测大气边界层高度变化

为了研究苏州地区大气边界层结构的日变化及季节特征,利用2014年1—7月期间大气颗粒物激光雷达对苏州上空大气气溶胶进行了连续观测。选定2014年1月15日、3月16日、5月7日与7月22日全天的消光系数探测数据,通过优化后的梯度法得到了该地区的大气边界层高度,分析了其日变化特征,并分析了边界层高度与地表的温湿变化之间的相关性。结果表明除1月15日外,边界层的变化与地表温度存在明显的正相关,而与地表的相对湿度存在负相关。同时,对站点微波辐射计观测得到的温湿廓线与边界层内消光系数廓线进行了联合研究。研究结果表明,微波辐射计湿度垂直廓线与激光雷达消光系数廓线探测得到的边界层具有良好的一致性。     

Synergistic Effects of Nitrogen Amendments and Ethylene on Atmospheric Methane Uptake under a Temperate Old-growth Forest

An increase in atmospheric nitrogen (N) deposition can promote soil acidification, which may increase the release of ethylene (C2H4) under forest floors. Unfortunately, knowledge of whether increasing N deposition and C2H4 releases have synergistic effects on soil methane (CH4) uptake is limited and certainly deserves to be examined. We conducted some field measurements and laboratory experiments to examine this issue. The addition of (NH4)2SO4 or NH4Cl at a rate of 45 kg N ha-1 yr-1 reduced the soil CH4 uptake under a temperate old-growth forest in northeast China, and there were synergistic effects of N amendments in the presence of C2H4 concentrations equal to atmospheric CH4 concentration on the soil CH4 uptake, particularly in the NH4Cl-treated plots. Effective concentrations of added C2H4 on the soil CH4 uptake were smaller in NH+4 -treated plots than in KNO3-treated plots. The concentration of ca 0.3 μl C2H4 L-1 in the headspace gases reduced by 20% soil atmospheric CH4 uptake in the NH4Cl-treated plots, and this concentration was easily produced in temperate forest topsoils under short-term anoxic conditions. Together with short-term stimulating effects of N amendments and soil acidification on C2H4 production from forest soils, our observations suggest that knowledge of synergistic effects of NH+4 , rather than NO3- , amendments and C2H4 on the in situ soil CH4 uptake is critical for understanding the role of atmospheric N deposition and cycling of C2H4 under forest floors in reducing global atmospheric CH4 uptake by forests. Synergistic functions of NH4+ -N deposition and C2H4 release due to soil acidification in reducing atmospheric CH4 uptake by forests are discussed.     

低高度角双频非差数据的周跳探测方法研究

针对低高度角双频非差数据测量噪声大、周跳探测容易出现误判和漏判的情况,本文基于电离层残差组合和MW组合进行了周跳探测算法的改进。在电离层残差法的周跳探测中,引入了时间窗口方法,利用周跳检测量的误差分布合理确定判定阈值的大小;在宽巷周跳的探测中,对MW组合方法中的判定条件进行了改进,采用加权递推平滑和时间窗口相结合的方法进行宽巷模糊度的精确估计和精度评价。经IGS站观测数据验证,改进算法取得了较好的周跳探测效果。     

海洋碳汇高分辨率检测技术综述和展望

为助推我国碳中和目标的实现以及提升我国在海洋碳汇领域的国际话语权,文章以海洋碳汇机制为切入点,系统梳理高分辨率生物和化学检测技术及其扩展应用。研究结果表明:海洋惰性溶解有机碳库对于海洋增汇具有重要意义,这对溶解有机碳汇资源高分辨率检测技术提出新的要求;目前具有“指纹特征”的高分辨率检测技术主要包括流式细胞和功能基因芯片生物检测技术以及光谱和质谱化学检测技术,此外结合稳定碳同位素标记技术实现生物溯源和化学检测的链接,均具有重要应用前景。     

A New Indicator for Global Food Security Assessment:Harvested Area Rather Than Cropland Area

Cropland area has long been used as a key indicator of food security.However,grain yield is not solely controlled by the area of the cropland.Therefore,we propo...     

鲁西地区金伯利岩的磁异常特征及物探方法有效性浅析

金伯利岩是金刚石的成矿母岩之一。鲁西地区目前已发现3条金伯利岩带,探明金刚石储量1 060万ct。搜集以往针对鲁西地区金伯利岩所做的大量磁测工作资料,对鲁西地区金伯利岩的磁异常特征进行总结,并对物探寻找金伯利岩有效性进行简要分析,认为在鲁西寻找金伯利岩,尤其是寻找隐伏的金伯利岩,需在了解地质背景的基础上,采用磁法、电法相结合,并结合已知金伯利岩的地球物理特征,综合分析验证。     

基于遥感影像的卫星颤振探测分析的关键技术与实现

姿态颤振是高分辨率卫星普遍存在的复杂现象,随着卫星的复杂性和敏捷性的提高,故其对成像质量的影响机制和相应的探测与补偿方法,成为高分辨率卫星对地观测研究的关键问题。本文介绍了基于遥感影像的卫星颤振探测原理和关键技术,利用传感器的构造特点,通过不同波段的多光谱影像,以及不同视角的全色立体影像间的密集匹配精确量测和获取影像视差差异值,反演卫星姿态颤振的规律和特性,从而对规律性的颤振现象进行建模和补偿。鉴于上述理论,在Visual C++的平台下,研制了卫星颤振探测分析系统,设计了以计算机性能优化的图像分块并行算法。测试结果表明,该软件能有效探测出0.1像元偏移的卫星姿态颤振,并可对规律性颤振进行建模和补偿,有较好的稳定性和并行效率。其已成功应用于资源三号卫星地面应用系统,并可扩展于其他卫星系统的颤振探测分析。