东北夏季极端低温天气事件的定义及其冷空气路径分析

采用东北三省150 个测站1961~2010 年的逐日温度资料和同期美国环境预报中心（NCEP）以及国家大气研究中心（NCAR）2.5°×2.5°分辨率的全球再分析资料,定义了东北夏季极端低温天气事件（extreme low-temperatureevent 以下简称ELTE事件）,统计给出了ELTE事件的发生、峰值和持续时间的日历表。根据该日历分析,发现了影响东北地区夏季ELTE事件的最主要的2 条冷空气路径（西北路径和东北路径）,1961~2010 年期间,影响东北地区的ELTE事件最主要是受西北路径的冷空气的影响,其次是东北路径。同时也发现,ELTE事件20 世纪80 年代发生频率最高,90 年代后开始减少,但是东北路径的ELTE事件在90 年代以后开始明显的增加。还发现,ELTE事件发生的前4 d,贝加尔湖地区若是被低压槽覆盖,易发生西北路径的ELTE事件,若该区域被一个东北-西南走向的高压斜脊控制,同时鄂霍次克海区域存在一个低压中心,形成西北“+”东南“-”的跷跷板形态,易发生东北路径的ELTE事件。     

An approach to spatially explicit reconstruction of historical forest in Northeast China

The spatially explicit reconstruction of historical land-cover datasets plays an important role in studying the climatic and ecological effects of land-use and land-cover change（LUCC）. Using potential natural vegetation（PNV） and satellite-based land use data, we determined the possible maximum distribution extent of forest cover in the absence of human disturbance. Subsequently, topography and climate factors were selected to assess the suitability of land for cultivation. Finally, a historical forest area allocation model was devised on the basis of the suitability of land for cultivation. As a case study, we used the historical forest area allocation model to reconstruct forest cover for 1780 and 1940 in Northeast China with a 10-km resolution. To validate the model, we compared satellite-based forest cover data with our reconstruction for 2000. A one-sample t-test of absolute bias showed that the two-tailed significance was 0.12, larger than the significant level 0.05, suggesting that the model has strong ability to capture the spatial distribution of forests. In addition, we calculated the relative difference of our reconstruction at the county scale for 1780 in Northeast China. The number of counties whose relative difference ranged from-30% to 30% is 99, accounting for 74.44% of all counties. These findings demonstrated that the provincial forest area could be transformed into forest cover maps well using the model.     

中国东北夏季极端高温变化特征及其与环流异常的联系

利用东北地区1960—2010年夏季逐日气温资料,研究了中国东北地区夏季极端高温的时空变化特征和区域性特征,并对东北地区夏季极端高温事件与大气环流异常的可能联系进行分析。结果表明,东北地区夏季极端高温频数有明显的升高趋势,升高幅度由南向北逐渐增大;东北地区南部、东北部和西北部夏季极端高温频数的年际及年代际变化存在明显差异。东北地区夏季极端高温高发年500 hPa位势高度上盛行纬向环流,东北地区上空位势高度的垂直分布接近于正压结构,且一直延伸至对流层顶,海平面气压场上亚洲大陆低压明显偏弱,南北气压梯度减小,冷空气不易南下;低发年,则反之。     

基于册与相对湿润度指数的1961-2009年东北地区5-9月干旱趋势分析

依据1961-2009年东北地区71个气象台站月平均气温和降水资料,运用标准化降水指数（SPI）与相对湿润度指数等干旱指标分析了东北地区5-9月的干旱趋势。结果表明：1961-2009年,东北大部分地区在5-9月呈干旱化趋势,仅在黑龙江省大兴安岭北部、黑龙江省西南部以及黑龙江省与吉林省的东部交界处表现为湿润化;东北三省干湿振荡主要周期为22-24a,近49a发生了4次干湿交替,突变年为1976年和1996年。就干旱发生范围而言,近49a东北地区干旱面积呈上升趋势;以1996年为分界线,农作物干旱受灾比在吉林省增幅最大,辽宁省次之,黑龙江省最小,采用删与相对湿润度指数评价东北地区干旱较符合实际。就干旱发生频率而言,高值区主要集中在东北地区西部,特别是黑龙江省的齐齐哈尔和大庆地区、吉林省的白城地区及辽宁省的朝阳地区。干旱与极端干旱的发生频率1981-1990年为较低,2001-2009年为最高;而极端干旱发生频率增加幅度明显高于一般干旱。     

广西暴雨的区域性和连续性研究

利用广西1961～2010年90个气象观测站的逐日降水资料,使用相关分析等方法研究广西暴雨的区域性和连续性,结果表明：前汛期存在三个大的暴雨高相关区：以桂林市、柳州北部形成一个暴雨区;一个以南宁市南部、崇左市北部地区、玉林部分地区为暴雨区;另外一个以梧州市西南部、玉林、北海、钦州三市为暴雨区。后汛期同样存在三个大的暴雨高相关区：以桂林、柳州二市、河池市南部形成一个暴雨区;一个以南宁、玉林二市南部、崇左市大部及沿海地区为暴雨区;另外一个以梧州、贵港、玉林及钦州、北海二市北部、南宁市中东部为暴雨区。总之,广西后汛期期暴雨相关显著区面积均比前汛期大。广西存在两个高的暴雨同时发生区域：一个由桂林市、柳州市北部组成的区域．该区域同一天发生暴雨的频率达到40％以上;另一个区域为桂南沿海地区,同一天发生暴雨的频率达到30％以上。     

东北冷涡的结构及其演变特征的个例综合分析

利用NCEP再分析资料、FY-2C、CloudSat云探测卫星和实况观测等资料对2009年6月27—30日出现的东北冷涡的热力动力结构、三维流场和云系演变特征进行了分析,并初步探讨了冷涡的发生、发展机理。结果表明:该冷涡冷心结构最初始于高层,随后逐渐向下伸展。成熟阶段的冷涡,对流层整层为冷心结构,冷中心位于对流层中高层,其上即平流层低层为暖心结构,中心东西两侧上升气流随高度向外倾斜,经向风趋于对称。发展初期温度槽落后于高度槽,且轴线向西倾斜,斜压性特征明显;至成熟阶段,温度中心与高度中心趋于重合,轴线近于竖直,显示出正压的特征;到减弱阶段,由于低层偏北风减弱明显,轴线又略向西倾斜。冷涡云带的产生与低层辐合带密切相关。CloudSat云探测卫星资料分析结果表明,冷涡环流内多中小尺度对流云团发展,且分布极不均匀。此次个例的研究结果揭示出冷涡的形成和发展跟对流层中上层切断低压的生成发展与对应的地面低压逐步耦合的动力学过程紧密相关,其中,冷暖气流呈旋转式下沉和上升,在冷涡中心形成偶极;对流层高层的干冷空气总是沿着等熵面从高层穿越等压面向下侵入到冷涡中心附近,干侵入使冷涡加强发展并维持其冷心结构。干侵入机制实际就是高位涡的侵入和下传,对预报冷涡的发展演变具有重要指示意义。     

The Major Interannual Modes of Late-Summer Precipitation Over the Northern China Monsoon Region

ABSTRACT

Summer precipitation in the northern China monsoon region (NCMR; 35°–55°N, 108°–135°E) shows significant intraseasonal variability. The early-summer (June) and late-summer (July–August) precipitation patterns show clear differences in their formation mechanisms and the systems that affect them. We used empirical orthogonal function (EOF) analysis to investigate the two leading modes of July–August precipitation over the NCMR and their associated atmospheric circulation anomalies using linear regression. The results show that the first (EOF1) and second (EOF2) modes correspond to a pan-NCMR precipitation variation pattern and a precipitation oscillation pattern between North China (NC) and Northeast China (NEC), respectively. These two modes account for 22.1% and 10.1% of the total variance, respectively. The associated principal components (PCs) both have significant interannual variability with a period of 2–4 years. In addition, PC1 has significant interdecadal variability with a period of 20–30 years. Further analysis suggests that EOF1 and EOF2 clearly have a different relationship with the summer monsoon circulation system. In the positive phase of PC1, the East Asian subtropical westerly jet stream (EAWJS) shows a northward trend with higher intensity than normal the blocking high at mid- to high latitudes is inactive; and the western Pacific subtropical high (WPSH) is located to the north of its normal position. The NCMR is controlled by stronger southerly winds, which cause the convergence of water vapour, favouring more precipitation in this region and vice versa. In the positive phase of PC2, the EAWJS swings to the south of Lake Baikal. Significant positive height anomalies exist from western NC to NEC. Significant negative height anomalies occur to the subtropical northwestern Pacific. This indicates that the cold vortex in Northeast China is inactive, the WPSH tends to be weaker and located to the south of its normal position, and NEC (NC) is dominated by anomalous northeasterly (southeasterly) winds. The convergence (divergence) of water vapour in NC (NEC) favours more (less) precipitation in NC (NEC) and vice versa. Therefore, EOF1 is related to the large-scale circulation anomalies over East Asia and the northwest Pacific in July and August, whereas EOF2 is more closely related to the anomalies in the regional circulation over the NCMR and the subtropical northwestern Pacific.     

Analysis of the weather process of blizzard caused by Northeast Cold Vortex in HeUongjiang province

利用NECP再分析资料、卫星云图资料、新一代天气雷达资料及实况观测资料对2010年4月12-13日一次东北低涡产生的黑龙江省暴雪天气过程进行分析,详细讨论了此次暴雪的发生机制及天气特点。此次降雪过程由地面气旋北上引发,高空低涡前部东风暖平流和槽后冷平流相遇形成暖锋锋生,低涡东北部产生暴雪。低空急流对水汽的输送作用和低层较强的辐合上升运动为此次降雪过程提供增强机制。云系的发展、移动与降雪有较好的对应关系,较大降雪出现在逗点云系顶部。     

东北非矿业投资环境分析

东北非地区成矿地质条件优越,矿产资源丰富,主要优势金属矿产为金、铜金矿、稀土及铂族元素矿产。本文对东北非主要矿产类型、开发现状进行了介绍,并详细阐述了埃塞俄比亚、厄立特里亚、苏丹三国的矿业法律法规、矿业权管理制度等内容,在此基础上对三国的矿业投资优势及风险进行了分析,并对投资者提出了相应的建议,认为东北非具有较好的矿产资源开发潜力和投资环境,中方企业应依据各国国情,把握机会,适时介入。     

东北准噶尔哈旦逊石炭纪弧岩浆及堆晶柱形成机制

为了阐明东北准噶尔弧岩浆形成机制和破译中地壳P波高速块体,对哈旦逊石炭纪侵入杂岩进行了锆石U-Pb年龄(324.8～323.1 Ma)和 δ18O及 εHf(t)、矿物化学、主微量元素和Nd-Sr同位素分析.其稀土元素分布模式上凹,从闪长岩(夹带角闪石岩堆晶)到二长花岗岩的主微量元素变异可以用两阶段分离结晶模拟.结果显...