Boreal temperature variability inferred from maximum latewood density and tree-ring width data, Wrangell Mountain region, Alaska

Variations in both width and density of annual rings from a network of tree chronologies were used to develop high-resolution proxies to extend the climate record in the Wrangell Mountain region of Alaska. We developed a warm-season (July–September) temperature reconstruction that spans A.D. 1593–1992 based on the first eigenvector from principal component analysis of six maximum latewood density (MXD) chronologies. The climate/tree-growth model accounts for 51% of the temperature variance from 1958 to 1992 and shows cold in the late 1600s–early 1700s followed by a warmer period, cooling in the late 1700s–early 1800s, and warming in the 20th century. The 20th century is the warmest of the past four centuries. Several severely cold warm-seasons coincide with major volcanic eruptions. The first eigenvector from a ring-width (RW) network, based on nine chronologies from the Wrangell Mountain region (A.D. 1550–1970), is correlated positively with both reconstructed and recorded Northern Hemisphere temperatures. RW shows a temporal history similar to that of MXD by increased growth (warmer) and decreased growth (cooler) intervals and trends. After around 1970 the RW series show a decrease in growth, while station data show continued warming, which may be related to increasing moisture stress or other factors. Both the temperature history based on MXD and the growth trends from the RW series are consistent with well-dated glacier fluctuations in the Wrangell Mountains and some of the temperature variations also correspond to variations in solar activity.     

南通地区暴雪的天气条件对比分析

通过对20世纪50年代以来南通地区的四次暴雪过程的分析，试从环流形势的配置、强度及物理量场特征上，找出具有共性的暴雪的指标，以供预报参考。     

Geoid determination using adapted reference field, seismic Moho depths and variable density contrast

 The traditional remove-restore technique for geoid computation suffers from two main drawbacks. The first is the assumption of an isostatic hypothesis to compute the compensation masses. The second is the double consideration of the effect of the topographic–isostatic masses within the data window through removing the reference field and the terrain reduction process. To overcome the first disadvantage, the seismic Moho depths, representing, more or less, the actual compensating masses, have been used with variable density anomalies computed by employing the topographic–isostatic mass balance principle. In order to avoid the double consideration of the effect of the topographic–isostatic masses within the data window, the effect of these masses for the used fixed data window, in terms of potential coefficients, has been subtracted from the reference field, yielding an adapted reference field. This adapted reference field has been used for the remove–restore technique. The necessary harmonic analysis of the topographic–isostatic potential using seismic Moho depths with variable density anomalies is given. A wide comparison among geoids computed by the adapted reference field with both the Airy–Heiskanen isostatic model and seismic Moho depths with variable density anomaly and a geoid computed by the traditional remove–restore technique is made. The results show that using seismic Moho depths with variable density anomaly along with the adapted reference field gives the best relative geoid accuracy compared to the GPS/levelling geoid. Received: 3 October 2001 / Accepted: 20 September 2002 Correspondence to: H.A. Abd-Elmotaal     

南京"2003.2.10"寒潮降温降雨(雪)天气过程初步分析

对2003年2月10日至11日发生在南京的一次寒潮降温降雨(雪)的主要影响系统，如阻塞高压、高空槽、横槽、中低层暖式切变线、地面冷锋以及地面暖低压倒槽等进行了描述和分析，并对某些物理量进行了分析。分析得出：这次寒潮降温降雨(雪)天气是在高空500hPa乌拉尔山阻塞高压崩溃、巴尔喀什湖至准噶尔盆地的横槽转竖，冷空气从西北路径东移南下，中低层冷槽与暖式切变线接合以及地面冷锋切入暖低压倒槽等天气系统的作用下发生的，并归纳出此类天气预报的指示系统，对于做好寒潮天气预报具有指导作用。     

一次降雪过程的中尺度模式(MM5)站点预报试验

本文利用中尺度数值预报模式(MM5)进行业务预报试验。对2002年12月6日前后一次降水过程进行应用分析，重点对阳泉市站点预报进行对比检验，得出该模式在站点有无降雪、降雪量级及降雪起报、结束时间等方面具有重要参考价值的结论，对于进一步开发降水预报精细产品有重要意义。     

正常椭球内部场的内蕴几何与密度分布

将重力场内蕴几何结构的研究引入到正常椭球内部场的研究中，深入探讨了内蕴几何量及其与内部物理量之间的关系，并据此建立了弱平衡条件下的基本微分方程，进而给出确定椭球内部内蕴几何量与场源密度分布的方法。研究表明，平衡形状理论中的Ｗａｖｒｅ公式和Ｃｌａｉｒａｕｔ方程可由内蕴几何与内部物理量之间的关系导出，它们是在平衡假设下取椭球近似的结果。     

青藏高原冬季积雪异常对东,南亚夏季风影响的初步数值模拟研究

利用一个耦合了简化的简单生物圈模式的大气环流谱模式（ＳＳｉＢ－ＧＣＭ），初步探讨了青藏高原冬季积雪异常对东、南亚夏季季风环流和降水的影响及其机理。结果表明，高原地区积雪增加将使随后地夏季东、南来季风明显减弱，主要表现为东、南亚季风区降水减少，索马里急流、印度季风的印度西南气流弱弱。另外，还提出欧亚大陆雪盖与整个高原雪盖和高原东部雪盖对东、南亚夏季风影响的敏感问题。与欧亚大陆雪盖相比，高原雪盖是影响     

青藏高原及其邻区岩石层三维密度结构

搜集了青藏高原及其邻近区域的S波速度三维层析成像结果和2万多个实测重力点资料，将重力资料进行各种改正并网格化为30′×30′的布格重力异常．首先采用密度差与S波速度差之间的经验关系式，建立青藏地区岩石层密度的初始模型，再利用布格重力异常进行阻尼最小二乘法反演，得到青藏地区岩石层三维密度分布结果．反演结果表明：（1）青藏高原岩石层密度分布不仅在纵向上不均匀，而且在横向存在明显的不均匀．在深度10－70km范围内，高原整体呈低密度特性，在50－70km深度范围内低密度特征更加突出，与周缘地区存在0，1g／cm³的密度差．而在90－110km深度范围内，高原岩石层地幔显示密度高．（2）岩层密度分布与大地构造有明显相关的分区性，显示出青藏块体、巴颜喀拉块体、塔里木块体和印度块体．     

人工增雪对冬麦冻害的影响

自１９７８年以来，在新疆北部沿天山一带对冬季层状云飞机播撒碘化银、干冰等冷云催化剂进行人工增雪作业，对１８个非播云年和１７个播云年的冬麦冻害做了对比，在播云期内冬小麦年平均冻害面积减少８０％以上。对３个主要因素（麦种改良、冬季气温升高和人工增雪）进行了分析，结果表明，人工播云是一个主要的因素。     

气球携带碘化银焰弹技术研究

主要介绍在北京地区开展气球携带碘化银焰弹雨雪作业的作业技术，经济效益等问题。通过各种增雨雪技术比较，认敢球携带碘化银焰弹增雨雪作业在北方干旱地区的抗旱工作中或作为收音机增雨雪作业的补充手段具有应用价值