基于Voronoi图的强降水过程空间非均匀性定量表征方法

利用Voronoi\\Delaunay图模型影响范围和局部动态的特性,提出一种基于动态边界定量提取强降水过程空间非均匀分布特征的新方法,根据1959—2002年中国740站逐日降水资料,构建5日、10日两种时间尺度区域持续性年极端强降水过程序列,用以检验该方法的应用效果,并应用该方法分析了5日(10日)区域持续性年极端强降水过程空间非均匀分布特征及其演变规律。结果表明：与传统的数量统计方法和区域插值方法相比,该方法在强降水空间分布中心、过程内不同强度降水覆盖区域、降水集中区等的定量度量方面具有更高的分辨力和较好实际应用价值;气候趋势分析中在1959—2002年间,5日区域持续性年极端强降水过程出现日期有明显提前趋势。     

贵州都匀七星洞石笋剖面晚更新世高分辨率的气候地层学

通过对贵州都匀七星洞4根石笋42件系统的TIMS230Th测年及694件稳定同位素分析,揭示的气候变化记录时限范围连续1～15万年,稳定同位素样品平均分辨率晚期达150～220a,早期达440～530a。研究表明,石笋δ18O曲线,相当于海洋记录的终止点Ⅰ及终止点Ⅱ具有特别明显的突变,其年龄分别为11.3kaB.P.及129.3kaB.P.,应为晚更新世顶、底界线的准确年代。晚更新世与深海氧同位素记录MIS2～MIS5e相对应的气候地层单元,其界限年代也分别得到了明确的界定。相当于格陵兰冰芯记录、北大西洋沉积记录的YD事件、Heinrich气候突变事件,几个石笋记录取得了一致的准确定位及定年。其中YD事件为12.76～11.52kaB.P.;Heinrich事件的H1～H6分别为17～15kaB.P.,24.6kaB.P.,30.5kaB.P.,39.3kaB.P.,47.8～46.8kaB.P.以及60.4kaB.P.。对其与北大西洋沉积及格陵兰冰芯记录所揭示的短尺度气候突变事件的可比性,表明东亚季风气候变化,与高纬度地区的气候变化呈遥相关响应,对研究东亚季风气候驱动机制及其与全球气候变化的响应关系和对晚更新世的地层学研究,均具有特别重要的意义。     

Multi-scale variation characteristics of polar vortex at 10 hPa in the Southern Hemisphere

By use of 1948-2007 NCEP/NCAR reanalysis monthly geopotential data, a set of circulation indices are defined to characterize the polar vortex at 10 hPa in the Southern Hemisphere, including area-(S), intensity-(P) and centre position-(λc , φc) indices. Sea-sonal variation, interannual anomalies and their possible causes of 10 hPa polar vortex in the Southern Hemisphere are analyzed by using these indices, the relationship between 10 hPa polar vortex strength and the Antarctic Oscillation are analyzed as well. The results show that: (1) the polar region at 10 hPa in the Southern Hemisphere is controlled by anticyclone (cyclone) from Dec. to Jan. (from Mar. to Oct.), Feb. and Nov. are circulation transition seasons. (2) Intensity index (P) and area index (S) of anticy-clone (cyclone) in Jan. (Jul.) show a significant spike in the late 1970s, the anticyclone (cyclone) enhances (weakens) from ex-tremely weak (strong) oscillation to near the climatic mean before a spike, anticyclone tends to the mean state from very strong oscillation and cyclone oscillates in the weaker state after the spike. (3) There is significant interdecadal change for the anticyclone center in Jan., while markedly interannual variation for cyclone center in July. (4) The ozone anomalies can cause the interannual anomaly of the polar anticyclone at 10 hPa in the Southern Hemisphere in Jan. (positive correlation between them), but it is not related to the polar cyclone anomalies. (5) There is notable negative correlation between the polar vortex intensity index P and the Antarctic Oscillation index (AAOI), thus AAOI can be represented by P.     

极端降水事件变化的观测研究

利用湖北1961—2014年站点逐日降水资料及人口和人口城乡构成数据,通过平均值分离、最小二乘法拟合、趋势系数和气候倾向率分析、M-K检验和累积距平检验等方法,从时空分布、趋势变化、局地特征等方面,分析了近54 a湖北极端降水的变化特征及其与城市化的关系,结果表明：(1)对于第95百分位的极端降水事件,湖北极端降水阈值的范围为43.5~85.1 mm,大部分站的阈值在暴雨雨量范围,高阈值区位于江汉平原和鄂东,低阈值区位于鄂西北,最高阈值出现在武汉站,最低阈值出现在竹山站和房县站。(2)近54 a来湖北多年平均的极端降水日(D_ep)、极端降水量(P_ep)、极端降水强度(I_ep)、最大5 d降水(R_{5 d})和雨量比均存在明显的区域特征,但I_ep、R_{5 d}的地域差异不如D_ep、P_ep明显。鄂西南南部以及鄂东南东部和南部是极端降水事件的高发区,鄂西北北部是极端降水事件的低发区。(3)极端降水指数(R)能反映极端降水的强弱,其大尺度存在明显的年际差异,而长期变化趋势不显著,P_ep、I_ep和雨量比呈弱增加趋势,R_{5 d}和极端降水频数呈弱减少趋势。(4)城市化发展速度会改变R及其局地距平百分比DR_ij、趋势系数和气候倾向率的空间分布。随着城市化发展速度加快,湖北城市“雨岛效应”的格局发生了变化,D_ep、P_ep、I_ep、R_{5 d}及其DR_ij从南北差异明显变为东西差异明显,江汉平原和鄂东的D_ep、P_ep、I_ep、R_{5 d}增加,而鄂西南的减少,且四者趋势系数通过显著性水平检验的站点数更多,气候倾向率绝对值也普遍增大,但大部分站点的变化趋势为负值。(5)湖北极端降水具有明显的城市效应,城市化发展速度较快的大城市代表站的极端降水阈值大于配对的小城市代表站,两种代表站平均的D_ep、P_ep、I_ep、R_{5 d}的年际变化较一致,但大城市代表站的I_ep、R_{5 d}普遍较大,极端降水的变化趋势更明显。

     

ESTIMATE OF METHANE EMISSIONS FROM RICE FIELDS IN CHINA BY CLIMATE-BASED NET PRIMARY PRODUCTIVITY

1INTRODUCTIONIrrigated ricefieldsarecharacterizedbylargespatialandtemporalvariationsin CH4 emissiontotheatmo-sphere.Accordingly,thereisagreatuncertaintyintheestimate ofCH4 emissionsfromricefields.GreateffortshavebeenmadetoestimatetheCH4 emissionsfromricefieldsandseveralapproacheshavebeendeveloped.TherepresentativemethodsincludetheIPCC(Inter-governmentPanelofClimateChange)region-specificemissionfactormethodandthemodelcalculationmethod.Toimprovethecalculationaccuracy,theIPCCmethodreq…     

铁岭市近45年气候变化特征分析

利用线性倾向率、滑动平均等方法,对铁岭市1960--2004年间4个气象观测站的月平均气温、降水量、平均最高气温、平均最低气温以及初终霜、无霜期、积温、透雨等资料进行分析,结果发现铁岭市近45年气候变化特点为温度呈上升、降水略减少的趋势,特别是近15年,气温增暖幅度加大,降水春夏两季减少明显;但各季增温幅度差异较大,对气候变暖贡献最大的是冬季,平均最低气温升温幅度明显高于平均最高气温,气温日较差变小;初霜拖后、终霜提前及无霜期延长,积温明显增多,透雨偏晚频率增大,极端气候事件出现的几率增大。     

Variability of East Asian Winter Monsoon in Quaternary Climatic Extremes in North China

In order to examine high-frequency variations of East Asian winter monsoon in Quaternary climatic extremes, two typical loess–paleosol sequences in the Chinese Loess Plateau were investigated. Sandy layers in the loess deposits, the “Upper sand” and “Lower sand” (layers L9 and L15, respectively), which represent a high-resolution record of paleomonsoon changes, have been sampled at intervals of 5–6 cm from sections at Luochuan and Xifeng. The grain size and magnetic susceptibility was measured for all samples. The grain-size results (a proxy of winter monsoon strength) indicate that the winter monsoon strength fluctuated on a millennial timescale during cold climatic extremes, with climatic events of a few hundred to a few thousand years. However, the winter monsoon was relatively stable during warm periods. The magnetic susceptibility signal (a proxy of summer monsoon intensity) is practically constant over the same period. This is tentatively explained by the assumption that the summer monsoon intensity was too low to be recorded in the magnetic susceptibility signal. The intensified winter monsoon events show periodicities in a range of 1000 to 2770 yr, with a dominant cycle of approximately 1450 yr. The detection of this oscillation in older glacial stages strongly suggests that it may be a pervasive cycle of the cold climatic phases of the Quaternary. Millennial-scale variations of the winter monsoon may be caused by instability of the westerly jet, which is determined by temperature differences between the polar and the equatorial regions.     

1965-2012年甘肃平凉地区大雪天气气候特征

利用甘肃平凉地区7个气象自动站1965-2012年的逐日气象整编资料, 统计出近48 a来大雪天气出现次数, 分析了平凉大雪天气的统计特征和气候变化规律, 然后用近14 a历史天气图资料对31次大雪过程进行对比分型, 总结出三类天气形势的特征. 结果表明: 1965-2012年48 a来, 平凉大雪天气出现次数总体变化趋势不显著; 大雪天气多集中出现在秋冬、冬春冷暖季节交替的时期, 冬春交替期间出现次数多于秋冬交替期间, 隆冬季节出现次数相对较少. 平凉产生大雪天气的主要天气形势有三类: 高原低槽型、西风带小槽型和阻高-横槽型, 三类形势中最多的是高原低槽型, 其他两类出现概率相差不到10个百分点.     

大气污染物含量分布与环境气象条件的关系

将1981—1986年我国大气降尘量、SO_2、NO_x及降水物pH平均值的分布特征与同期的平均雨量、雨日、相对湿度和地面风场等的分布作了对照,发现其间存在一定关系,当上述环境气象场发生变动或出现反常时,这些大气污染物的分布也将发生变化。     

Environmental evolution of Gongwang Mountains during Holocene in northeastern Yunnan, China

This paper presents the study on two continuous glacio-lacustrine sedimentary deposits, Laotanfang （3 597 m） and Shibantang （3 689 m） located on the southern and northern sides of Hulifang peak in Yunan, China. Environmental change indexes are constructed for each deposit, based on grain size, geochemical and pollen analysis, environmental magnetic susceptibility, and 14C dating. The study of climatic environmental change since the Holocene epoch in this region shows that the climate fluctuated at different stages during the early Holocene, that is, the climate was cool and wet during 8.4-7. 7r ka, cold and wet during 7.7-6. 5 ka, cold and dry during 6. 5-4.7 ka, cool and wet during 4.7-2. 1 ka, warm and wet during 2. 1-1.0 ka, and warmer and wet since 1 ka. These findings reflect the overlapping influences of the southwest and southeast monsoons in different times during the Holocene in the north part of southwestern China are in accord with other Holocene climate change models in this part of China.