1954年山丹7 1/4级地震概述

1954年山丹7 1/4级地震的极震区烈度达X度,造成50人死亡,329人受伤,受灾面积4800 km2,山丹县城破坏最重.本文回顾、总结了山丹地震五十年的研究积累,重点论述了该地震的基本参数、震源机制、地震序列、地震烈度、地震破裂带、历史地震、震害及其损失等.     

甘肃张掖市冬季气温变化的时空特征

依据张掖市近50年来的冬季气温观测资料,运用Mann-Kendall法、小波分析、空间插值等方法,对张掖市冬季气温的时空分布规律和变化周期进行分析。结果表明:冬季气温总体上呈现增暖的趋势(β值为0.08),线性增长率为0.56℃/10a,相当于近50年冬季气温升高了2.8℃,冬季增温对全年升温的贡献率高达89%。1985年冬季气温发生突变,之后进入偏暖期,1987年后增温趋势更加显著。冬季气温存在10年左右和22年左右的振荡周期,其中22年左右的振荡周期较强。冬季气温空间分布不均,呈现出由东南向西北逐渐增温的趋势。冬季气温从20世纪70年代起就开始增温,东部增温速度明显高于西部,冬季气温增暖主要发生在最近的20余年内。     

基于混合像元分类的城市地表覆盖时空演变格局研究

基于可能性理论和中心点聚类方法的原理,提出可能性C中心点(PCRMDD)聚类方法.运用该法对上海市中心城区Landsat ETM+遥感影像进行混合像元分类,并自动获取地物端元盖度分布图及影像端元光谱,解混精度的检验结果表明该方法能在噪声环境下获得精度较高的分类结果和端元光谱信息.根据各时期研究区域的地表覆盖分类结果,应用GIS空间分析功能,进一步探讨在城市化过程中上海中心城区土地利用时空演变格局,揭示城市用地空间扩展模式.     

鄱阳湖非平稳水位波动及其与长江的交互作用关系(英文)

Seasonal water-level fluctuations(WLF) play a dominate role in lacustrine ecosystems. River-lake interaction is a direct factor in changes of seasonal lake WLF, especially for those lakes naturally connected to upstream and downstream rivers. During the past decade, the modification of WLF in the Poyang Lake(the largest freshwater lake in China) has caused intensified flood and irrigation crises, reduced water availability, compromised water quality and extensive degradation of the lake ecosystem. There has been a conjecture as to whether the modification was caused by its interactions with Yangtze River. In this study, we investigated the variations of seasonal WLF in China’s Poyang Lake by comparing the water levels during the four distinct seasons(the dry season, the rising season, the flood season, and the retreating season) before and after 2003 when the Three Gorge Dam operated. The Water Surface Slope(WSS) was used as a representative parameter to measure the changes in river-lake interaction and its impacts on seasonal WLF. The results showed that the magnitude of seasonal WLF has changed considerably since 2003; the seasonal WLF of the Poyang Lake have been significantly altered by the fact that the water levels both rise and retreat earlier in the season and lowered water levels in general. The fluctuations of river-lake interactions, in particular the changes during the retreating season, are mainly responsible for these variations in magnitude of seasonal WLF. This study demonstrates that WSS is a representative parameter to denote river-lake interactions, and the results indicate that more emphasis should be placed on the decrease of the Poyang Lake caused by the lowered water levels of the Yangtze River, especially in the retreating season.     

上海短历时强降水的雷达和闪电活动特征

用雷达反射率及其导出产品(分层垂直液态水含量(VIL)、分层平均反射率等)与闪电和大气温度层结资料,通过对降水系统时间演变、反射率垂直结构和闪电活动的分析,将上海2010年6—11月的短时强降水(1 h雨量≥20 mm)分为层状暖云型、对流暖云主导型和对流冷云主导型。(1) 与雨强密切相关的关键因子是:低层(0 ℃层以下、高度在0～1 km、0～2 km、0～3 km和0～4 km)的VIL、低层(高度在1～2 km、2～3 km和3～4 km)的平均反射率和整层最大反射率;(2) 不同类型强降水中,高层(高度在0 ℃、-10 ℃和-20 ℃层以上)的VIL、整层VIL、高层(高度在5～6 km、6～7 km和7～8 km)的平均反射率、总地闪和负地闪频次这5个因子对雨强的作用各有不同;(3) 对应不同降水类型的平均反射率垂直廓线具有不同的垂直结构和发展演变特征;(4) 在三类强降水中,对流冷云主导型的雨强与总地闪和正地闪的相关性最好。      

INVESTIGATION ON EFFECTS OF INITIAL SCHEMES FOR BINARY TYPHOONS ROKE AND SONCA IN 2011

Based on the Tropical Region Atmospheric Modeling System for South China Sea (TRAMS), Typhoon Roke (1115) and Sonca (1116) in 2011 which have large forecast errors in numerical operation prediction, have been selected for research focusing on the initial scheme and its influence on forecast. The purpose is to find a clue for model improvement and enhance the performance of the typhoon model. Several initialization schemes have been designed and the corresponding experiments have been done for Typhoon Roke and Sonca. The results show that the forecast error of both typhoons’ track and intensity are less using the initial scheme of relocation and bogus just for the weak Typhoon Sonca, compared with using the scheme for both typhoons. By analysis the influence of the scheme on weak typhoon vortex circulation may be the reason that leads to the improvement. All weak typhoons in 2011 to 2012 are selected for tests. It comes to the conclusion that the initial scheme of relocation and bogus can reduce the error of track and intensity forecast. Besides, the height of cloud top in typhoon vortex constructed by bogus is too high according to weak typhoon. It is feasible to develop a bogus which is suitable for weak typhoon.     

2013 年汛期ECMWF集合统计量产品的降水预报检验与分析

2013年汛期ECMWF集合预报在江南、四川盆地和华北地区强降水过程中的表现如下：对江南和四川盆地强降水,概率匹配、融合产品、最大值、75%和90%分位数在大雨和暴雨预报中较确定性预报有明显正技巧,融合产品和90%分位数的技巧评分最稳定;对华北地区强降水,仅90%分位数在大雨预报中有一致的正技巧;上述统计量产品的中期预报技巧评分总体要高于短期预报,对四川盆地（华北地区）暖区强降水预报技巧评分总体要高（低）于对该区域锋面强降水预报技巧评分。根据概率匹配和融合产品各自特点,综合二者原理,设计出概率匹配-融合和融合-概率匹配两种新方案。结果显示,在暴雨和大暴雨降水预报中,融合-概率匹配的评分较融合产品有一定提高。     

我国无缝隙精细化网格天气预报技术进展与挑战

本文总结了2014年以来我国无缝隙精细化网格天气预报业务的技术进展,讨论了未来发展所面临的关键技术难点。无缝隙精细化网格预报技术的发展,得益于综合气象观测数据和多源资料融合分析网格实况产品的支撑,更依赖于多尺度数值预报模式和实时快速更新同化预报系统的快速发展。经过近5年的探索和努力,我国已经初步建立了针对不同预报时效的无缝隙精细化网格预报技术体系。对于0～4 h预报时效,主要基于全国雷达拼图和GRAPES-Meso模式预报,发展临近分钟级滚动外推预报技术;对于4 h到30 d预报时效,主要通过对区域或全球不同时空分辨率模式预报进行偏差订正、客观解释应用以及降尺度分析,提高预报的准确度和精细度。与此同时,研发了自动化、智能化的交互式预报制作平台,以满足客观高效制作与预报员对极端或高影响天气主观预报优势相结合的需求。发展了以格点实况分析场为参照的空间分析检验方法,初步实现了对高分辨率网格预报的质量跟踪和性能评估。未来的网格预报技术体系,需要吸纳前沿的技术研究成果,包括人工智能应用技术、高级多模式统计后处理技术和协调一致性关键技术等,并且建立统一完整的技术架构和开发标准等。     

广东寒冷预警信号所示寒冷天气的时空分布特征

根据广东各地常规气象观测站建站至2006年地面观测资料,采用现行的寒冷预警信号定义,对广东省各地历史寒冷天气状况进行统计,结果表明,广东寒冷天气秋、冬、春3季在全省范围均可出现,达到寒冷预警信号发布标准的寒冷天气最长可持续2个多月;寒冷天气一般始于粤北,也终于粤北;南部出现寒冷天气的频率少于北部;气温降幅程度和最低气温的极端值,北部的寒冷程度始终甚于南部。黄色信号代表的寒冷天气出现的频率随年代的变化不大,而橙色和红色信号代表的极端寒冷天气出现的频率随年代的推移有减少的趋势。     

北京几次弱降水过程预报失误分析

在选取的北京地区2011年冬季至2012年春季9次弱降水过程中,预报员出现了4次空报、2次漏报,预报效果总体不理想。通过对9次过程的预报检验、天气分析和多模式预报对比,得到如下认识:北京地区弱降水过程天气形势复杂多样,按高空大气环流形势可分为两槽一脊型、一槽两脊型、一槽一脊型,按地面天气形势可分为冷锋型、华北锢囚锋型、东风与倒槽型和东风回流型;弱降水过程普遍具有对流层低层水汽条件差或动力抬升弱的特点;对湿层浅薄、饱和层高度高、抬升凝结高度高的弱降水过程,数值模式容易出现空报;而对低层湿度条件好、饱和层高度低、抬升凝结高度低但高空系统弱的降水过程,模式又容易出现漏报;预报员主观预报出现空、漏报主要源于对天气系统的结构及发生发展机理认识不足,对边界层水汽、抬升等关键降水要素缺乏预报订正经验。