寒潮冷堆增强的动力原因

本文利用动力学诊断方法分析了1979年11月一次东亚寒潮过程,证明500毫巴冷中心在南移过程中不断增强是由于寒潮冷空气堆中存在上升运动使空气绝热膨胀冷却所致。文中还从动力学观点解释了寒潮过程中垂直反环流的成因。指出对流层高层(300毫巴)急流核上游(入口区)和下游(出口区)存在相反的铅直环流,上游为正环流,下游为反环流。急流核两侧存在强大的正负切变涡度平流是使急流核上,下游存在性质相反的铅直环流的原因。文中近似计算了这次寒潮过程中槽后偏北急流核两侧空气的12小时二维轨迹,证明槽后偏北急流核左侧强大的正切变涡度中心及其相应的下游正涡度平流引起了寒潮冷空气堆上空质量辐散。因此在寒潮分析和预报时应注意围绕西风槽的急流分布的不均匀性,特别是300毫巴槽后偏北急流中急流核的存在及其活动对预报寒潮冷空气堆的增强是十分重要的。     

正压原始方程套网格试验

本文用“单向”(one—way)方法进行正压原始方程套网格试验。粗、细网格均采用空间分解准拉格朗日格式和由廖洞贤等提出的与此差分格式一致的内边界条件(即方案二)。试验结果表明,用方案二作出的24小时细网格预报,与按半动量格式和粗网格直接给细网格提供内边界条件(即方案一)所得的结果相比,去除了在流出处出现的不稳定,系统的流入、流出也较好。这两种方案再加上Davies“松弛区域”的方法(分别为方案四,方案三),其结果与上述类似,且方案四比方案二还要好些。     

与西太平洋暖池上空对流年际变化相关联的大气环流和海温

诊断分析了热带西太平洋暖池上空对流弱和强的情况下,大气环流和海温所表现出来的差异。本文中西太平洋暖池是指（１１０－１６０°Ｅ,１０－２０°Ｎ）地区,向外射出长波辐射（ＯＬＲ）在该地区具有明显的年际变率。对西太平洋暖池对流弱和强之间大气环流和海温的差别进行了合成分析。首先,利用 ＮＣＥＰ／ ＮＣＡＰ再分析资料和卫星观测的 ＯＬＲ资料进行了分析。之后,利用欧洲中期天气预报中心再分析资料和再分析计算而得的ＯＬＲ资料重复进行了合成分析。合成结果表明由这两套资料所分析得到的结果非常相象。与西太平洋暖池上空弱（强）对流显著对应的大气环流表现为北太平洋副热带高压的西伸（东退）,以及副高西北侧更强（弱）的西风。此外,在局地（即暖池）上空,还显著对应着东（西）风异常和下沉（上升）气流异常。对应于西太平洋暖池对流强弱,最为显著的海温差别（对流弱减去对流强）为印度洋、孟加拉湾和南海的正海温异常。也就是说,西太洋暖池上空的对流与局地海温异常只有微弱的联系,而与其西部的海温异常密切相关。     

鲜水河断裂带的构造大地测量

利用短边GPS点阵、短基线标石阵和精密激光测距 ,在与鲜水河断裂带的断层破裂带垂直的剖面上和构造盆地内进行构造大地测量 ,获得了断层软弱带和断层蠕变带上的最佳形变分布。综合利用相关地学成果和理论 ,揭示了构造形变所隐含的动力学信息 ,识别了断层应变带、塑性流变带和主断面在地面的分布范围。用外围GPS远场联测成果探讨了该断裂带的驱动力机制 ,匡正了其“左旋”运动和现今活动速度的含义。最后 ,评估了该断裂的地震活动趋势     

Earthquakes in the Czech Republic and Surrounding Regions in 1995–1999

In the time span from January 1995 to December 1999 the Czech National Seismological Network (CNSN), consisting of ten permanent digital broadband stations, several local networks and two data centers, detected and recorded 9530 regional natural seismic events, 27 greater than magnitude 2. Most of these events were located by the Czech Seismological Service (CSS), and the most prominent of them were analyzed in detail. A large number of quarry blasts were recorded as well but were not included in the analysis. We provide basic information on the configuration of the CNSN and on the way of routine data processing employed by the CSS in this paper. The over-all regional seismicity monitored by the CNSN in 1995–1999 is briefly reviewed. The main results of observations and evaluation of the local (NW-Bohemia/Vogtland, South Bohemia, Sudeten) and induced (Kladno, Píbram, Upper Silesia, Lubin/Poland) seismic activity within this period are presented in a condensed form. Finally, a summary on macroseismic observations on the territory of the Czech Republic in 1995–1999 is also presented.     

Analysis of the solar low-ℓ p-mode asymmetries using wavelets

It is presently widely accepted that the solar low p modes show asymmetric profiles when their power spectrum is analysed and that the fact of fitting symmetric profiles yields systematic effects in the obtained frequencies which could affect the results of inversions. In this paper the low p-mode profiles are analysed using wavelets to denoise the power spectra of the modes. This denoising method is applied both to artificial data generated by Kosovichev (the Hare and Hound exercise) and to real data obtained with the GOLF instrument. The asymmetries as well as the frequencies obtained are studied in both cases. The results show that although the obtained p-mode profiles present a slightly negative asymmetry, the use of symmetric profiles to fit the power spectra does not introduce any systematic effect in the obtained frequencies.     

箱法在草地温室气体通量野外实验观测中的应用研究

利用静态箱法采样,配以气相色谱仪法分析对草地N2O、CH4和CO2温室气体通量进行了较系统的现场测量,同时对箱体内外温度进行同步观测。在对野外原位观测实验数据进行定量分析的基础上,论证了静态箱法对草原土壤-植被系统的N2O、CH4和CO2通量测量的适用性和科学性,讨论了实验结果的可靠性。     

The 2001 Mesoscale Convective Systems over Iberia and the Balearic Islands

Summary This paper characterizes Mesoscale Convective Systems (MCSs) during 2001 over Iberia and the Balearic Islands and their meteorological settings. Enhanced infrared Meteosat imagery has been used to detect their occurrence over the Western Mediterranean region between June and December 2001 according to satellite-defined criteria based on the MCS physical characteristics. Twelve MCSs have been identified. The results show that the occurrence of 2001 MCSs is limited to the August–October period, with September being the most active period. They tend to develop during the late afternoon or early night, with preferred eastern Iberian coast locations and eastward migrations. A cloud shield area of 50.000 km² is rarely exceeded. When our results are compared with previous studies, it is possible to assert that though 2001 MCS activity was moderate, the convective season was substantially less prolonged than usual, with shorter MCS life cycles and higher average speeds. The average MCS precipitation rate was 3.3 mm·h⁻¹ but a wide range of values varying from scarce precipitation to intense events of 130 mm·24 h⁻¹ (6 September) were collected. The results suggest that, during 2001, MCS rainfall was the principal source of precipitation in the Mediterranean region during the convective season, but its impact varied according to the location. Synoptic analysis based on NCEP/NCAR reanalysis show that several common precursors could be identified over the Western Mediterranean Sea when the 2001 MCSs occurred: a low-level tongue of moist air and precipitable water (PW) exceeding 25 mm through the southern portion of the Western Mediterranean area, low-level zonal warm advection over 2 °C·24 h⁻¹ towards eastern Iberia, a modest 1000–850 hPa equivalent potential temperature (θ_e) difference over 20 °C located close to the eastern Iberian coast, a mid level trough (sometimes a cut-off low) over Northern Africa or Southern Spain and high levels geostrophic vorticity advection exceeding 12·10⁻¹⁰ s⁻² over eastern Iberia and Northern Africa. Finally, the results suggest that synoptic, orographic and a warm-air advection were the most relevant forcing mechanisms during 2001.