GRAPES模式不同云物理方案对短期气候模拟的影响

在胡志晋、刘奇俊云物理方案的基础上，研制了GRAPES模式的云降水显式方案。用不同云物理方案开展了短期气候（月尺度）过程的模拟试验，并与地面观测资料和NECP再分析资料进行了对比分析。模拟的结果表明，耦合了云降水显式方案的GRAPES模式较好地模拟出了中国地区降水、温度、云量、长短波辐射的特点和分布规律。气候模拟中冰相过程和暖云过程模拟的降水、温度、云量和辐射差异较大，不同相态的水凝物及其分布对辐射特征有较大的影响，混合相云物理方案的模拟结果与实况更为吻合，应使用混合相云物理方案进行短期气候的模拟。     

Matlab在北京飞机增雨航迹分析中的应用

飞机航迹分析是飞机云物理和大气环境探测中进行飞行探测资料整合中的一项重要工作,在GPS航迹资料分析中,资料的不连续和经纬度数据进制换算是飞机探测作业分析中常遏的问题。根据北京2004年增蓄型飞机人工增雨探测作业试验期间GPS航迹数据特点,通过Matlab分析讨论其中的问题,利用Matlab良好的矩阵运算功能,对航迹经纬度数据进行换算,并根据航迹记录时间的连续性特点,提出了对不恰当、丢失和重复数据的判断分析方法。分析使用表明,在飞机探测作业航迹分析中,Matlab可以很方便地进行数据分析处理,并能将结果进行多维可视化显示。     

河西走廊盛夏一次强沙尘暴天气综合分析

利用常规气象观测资料和NCEP／NCAR月平均再分析资料,对2003年7月20日甘肃河西走廊一次历史上少见的区域性夏季沙尘暴天气进行了分析。研究发现：高空小槽、切变线、热低压是引发夏季沙尘暴的主要天气系统。夏季沙尘暴发生过程中,各测站出现了气压跃升、风速猛增、气温下降、湿度增加等现象,但变化幅度小于春季。夏季沙尘暴云图特征表现为中小尺度云团,TBB≤-35℃的云团在一定程度上能够反映沙尘暴天气的变化。诊断分析表明,沙尘暴爆发前散度场呈低层辐合高层辐散状态,沙尘暴发生在最大垂直速度出现以后,同时水平螺旋度对夏季沙尘暴预报有较好的指示意义,螺旋度正值越大,沙尘暴越强。     

焦作市4-9月短期降水精细化预报系统

在降水时空变化研究的基础上,完成辖区降水区划;用计算机识别T213风场中槽线、切变线等影响系统,并按其相对于预报站方位,确定对其影响强度指数,组合预报因子,建立判别方程,制作分县0～12小时、12～24小时降水分级预报。经检验,系统对降水落区有较强预报能力。     

和田市近40年蒸发量的变化特征

利用和田市气象站1961-2000年20cm口径蒸发量资料，对蒸发量的年、季、月变化趋势、年代际变化特征、突变和周期等气候变化作了较全面分析。结果表明：40年来各季、月蒸发量呈现不同程度的上升趋势，年蒸发量以48．52mm／10a的倾向率增多，偏多趋势主要表现在春季、秋季，其中5月份蒸发量偏多趋势最明显。年蒸发量在20世纪60年代为相对偏少期，80年代为相对偏多期。采用累积距平曲线和标准Morlet小波方法对年总蒸发量进行突变检验和周期分析表明，年蒸发量在1978年发生一次突变，蒸发量变化具有4～6年、11年和22年左右的年周期变化。     

两种垂直累积液态含水量产品的应用对比分析

结合雷达体扫工作模式以及风暴单体垂直结构分布,利用CINRAD气象产品软件包提供的基于单体和格点的VIL产品,对滨州SC雷达监测到的几例强对流风暴单体个例进行分析发现,两种VIL产品的变化趋势基本与风暴变化同步,对灾害性天气发生的预警具有较好的指示意义;一般情况下,基于单体的VIL数值大于基于格点的VIL数值,尤其是发展成熟、孤立的强风暴单体表现更加明显,可以作为判断风暴单体强度的定性指标;对于多单体风暴,由于风暴质心识别等因素会造成VIL数值误差增大,而雷达体扫模式的限制可能造成VIL数值失真。     

高低空急流在闽西北大暴雨过程中的作用及数值模拟

本文对2002年6月14~18日福建西北部地区的连续暴雨~大暴雨过程的诊断及模拟分析表明,在有利的环流背景条件下,高空急流的加强和动量下传,促使低空急流的建立和维持;低空急流的加强则提供了有利暴雨产生的高温高湿的大气条件;高低空急流的适宜配置,产生了动力场的耦合作用,为大暴雨的发生、发展提供了动力条件。     

Acidities of confined water in interlayer space of clay minerals

The acid chemistry of confined waters in smectite interlayers have been investigated with first principles molecular dynamics (FPMD) simulations. Aiming at a systematic picture, we establish the model systems to take account of the three possible controlling factors: layer charge densities (0 e, 0.5 e and 1.0 e per cell), layer charge locations (tetrahedral and octahedral) and interlayer counterions (Na⁺ and Mg²⁺). For all models, the interlayer structures are characterized in detail. Na⁺ and Mg²⁺ show significantly different hydration characteristics: Mg²⁺ forms a rigid octahedral hydration shell and resides around the midplane, whereas Na⁺ binds to a basal oxygen atom and forms a very flexible hydration shell, which consists of five waters on average and shows very fast water exchanges. The method of constraint is employed to enforce the water dissociation reactions and the thermodynamic integration approach is used to derive the free-energy values and the acidity constants. Based on the simulations, the following points have been gained. (1) The layer charge is found to be the direct origin of water acidity enhancement in smectites because the neutral pore almost does not have influences on water dissociations but all charged pores do. (2) With a moderate charge density of 0.5 e per cell, the interlayer water shows a pKa value around 11.5. While increasing layer charge density to 1.0 e, no obvious difference is found for the free water molecules. Since 1.0 e is at the upper limit of smectites’ layer charge, it is proposed that the calculated acidity of free water in octahedrally substituted Mg²⁺-smectite, 11.3, can be taken as the lower limit of acidities of free waters. (3) In octahedrally and tetrahedrally substituted models, the bound waters of Mg²⁺ show very low pKa values: 10.1 vs 10.4. This evidences that smectites can also promote the dissociations of the coordinated waters of metal cations. The comparison between the two Mg²⁺-smectites reveals that different layer charge locations do not lead to obvious differences for bound and free water acidities.     

Late Jurassic-Early Cretaceous Northern Qaidam Basin, NW China: Implications for the earliest Cretaceous intracontinental tectonism

Formation of Mesozoic western China, which was dominated by tectonic amalgamation along its southern margin and associated intracontinental tectonisms, holds a key for interpreting the succedent Cenozoic evolution. This paper presents new data including lithology, sedimentary facies, stratigraphic contact, seismic interpretation and paleo-structures within the Upper Jurassic-Lower Cretaceous strata in the northern Qaidam Basin, NW China. These data all account for a contractional tectonic deformation in the earliest Cretaceous. The South Qilian Shan, according to the sedimentary features and provenance analysis, reactivated and exhumated during the deformation, controlling the deposition of the Lower Cretaceous sequences. A simplified model for the Late Jurassic-Early Cretaceous paleogeography and tectonics of the northern Qaidam Basin is accordingly proposed. The results also support a ∼25° clockwise rotation of the Qaidam Basin since the Early Cretaceous and a more accurate Mesozoic evolution process for the basin. This earliest Cretaceous deformation, associated with the reactivation of the South Qilian Shan at the time, are part of the intracontinental tectonisms in central Asia during the Mesozoic, and probably driven by both the closure of the Mongol-Okhostk Ocean to the north and the collision of the Lhasa and the Qiangtang blocks to the south.     

Mercury fluxes from air/surface interfaces in paddy field and dry land

In order to provide insight into the characteristics of Hg exchange in soil/water-air surface from cropland (including paddy field and dry land), Hg fluxes were measured in Chengjiang. Mercury fluxes were measured using the dynamic flux chamber method, coupled with a Lumex® multifunctional Hg analyzer RA-915⁺ (Lumex Ltd., Russia). The Hg fluxes from paddy field and dry land were alternatively measured every 30 min. Data were collected for 24-48 h once per month for 5 months. Mercury fluxes in both fields were synchronously measured under the same conditions to compare Hg emissions between paddy field and dry land over diurnal and seasonal periods and find out what factors affect Hg emission on each surface. These results indicated that air Hg concentrations at the monitoring site was double the value observed at the global background sites in Europe and North America. The Hg release fluxes were 46.5 ± 22.8 ng m⁻² h⁻¹ in the warm season, 15.5 ± 18.8 ng m⁻² h⁻¹ in the cold season for dry land, and 23.8 ± 15.6 ng m⁻² h⁻¹ in the warm season, 6.3 ± 11.9 ng m⁻² h⁻¹ in the cold season for paddy field. Solar radiation is important in the emission of Hg over both sites. Hg exchange at the soil/air and water/air interfaces showed temporal variations. The amount of Hg emission from dry land was higher than that from the paddy field, and the emission in daytime was higher than that at night. Moreover, Hg emissions from land covered by crops, was lower than that for bare land.