平流层NAM 异常事件与东北亚地面温度的关系

对再分析资料的合成分析表明,10 hPa北半球环状模(NAM)指数和东北亚地区地面温度(SAT)存在显著的后滞相关关系.正/负位相平流层NAM异常事件往往伴随着东北亚地区正/负异常地面温度变化.负位相NAM指数超前东北亚地面温度异常20～40天,正位相NAM指数超前约20天.定义了有效平流层极端事件(ESE),并研究了不同标准下平流层NAM异常能够传到对流层的比例.研究表明,NAM异常下传的比例随定义标准的提高而增加.研究结果显示,平流层大气环流异常在一定程度上能够作为先兆因子来延长中国北方冬季对流层天气预报.     

平流层NAM异常对乌拉尔山阻塞高压的影响

使用NCEP/NCAR再分析资料, 对53年(1958?2010年)冬季的平流层北半球环状模(NAM)正、负异常下传期间乌拉尔山阻塞高压的活动特征分别进行合成分析。结果表明, 在平流层NAM负异常下传期间, 阻塞高压事件的发生频次更高, 生命期更长, 并且在空间上发展得更加深厚。阻塞高压崩溃之后, 冷空气主体偏北, 所造成的我国北方地区降温也更强。通过对E-P 通量分析发现, 在NAM负异常下传期间, 乌拉尔山区域的波动更容易向上传播, 更有助于对流层乌拉尔山阻塞高压的维持和发展。这些结果对利用平流层环流异常信号预测我国北方冬季短期气候变率, 尤其是寒潮天气有重要意义。     

平流层NAM异常对东北冷涡活动影响的研究

为了研究平流层环流异常对东北冷涡的影响, 使用NCEP/NCAR(1958?2010年)再分析资料(日平均、月平均位势高度场及温度场), 对平流层NAM (northern hemisphere annular mode, 北半球环状模)异常期间东北冷涡的活动特征和三维空间结果进行了统计和合成分析。结果发现, 与平流层NAM正异常相比, 在平流层NAM负位相异常期间, 东北冷涡发生的频次更多和持续天数更长, 强度也更强。对平流层NAM不同位相异常期间的合成分析表明, 在平流层NAM负位相异常期间, 东北冷涡强度更强, 与平流层环流异常联系更紧密。同时平流层NAM负位相异常期间, 有强的行星波活动, 行星波的活动促进和加强了东北冷涡的发展。研究结果对使用平流层NAM异常预测冬季东北冷涡有重要意义。     

平流层NAM异常对东北冷涡活动影响的研究

为了研究平流层环流异常对东北冷涡的影响,使用NCEP/NCAR(1958—2010年)再分析资料(日平均、月平均位势高度场及温度场),对平流层NAM(northern hemisphere annular mode,北半球环状模)异常期间东北冷涡的活动特征和三维空间结果进行了统计和合成分析。结果发现,与平流层NAM正异常相比,在平流层NAM负位相异常期间,东北冷涡发生的频次更多和持续天数更长,强度也更强。对平流层NAM不同位相异常期间的合成分析表明,在平流层NAM负位相异常期间,东北冷涡强度更强,与平流层环流异常联系更紧密。同时平流层NAM负位相异常期间,有强的行星波活动,行星波的活动促进和加强了东北冷涡的发展。研究结果对使用平流层NAM异常预测冬季东北冷涡有重要意义。     

2003-2004年冬季北半球爆发性增温期间极地平流层甲烷、水汽的演变特征

利用欧洲空间局(ESA)提供的ENVISAT/MIPAS(Michelson Interferometer for PassiveAtmospheric Sounding)卫星观测数据以及ECMWF业务分析场,综合分析了2003-2004年冬季北半球爆发性增温(SSW)事件中极地平流层大气甲烷和水汽的演变特征.结果表明:(1)增温出现时,平流层高、中层极涡先后发生分裂,对应的甲烷、水汽极值中心也同时发生分裂;(2)增温下传过程中,平流层中上层甲烷、水汽同时具有"向上输送"的特征,这主要是由极地平流层的上升运动造成;增温过程中行星波活动引起的向极输送造成这种"向上输送"特征在高层具有一定的超前性;(3)增温后期,高层极涡迅速恢复,极涡内的下沉运动将中间层低层的空气(甲烷、水汽浓度极低)输送进入平流层,造成平流层高层极涡(52 km附近)内出现甲烷、水汽浓度的异常低值.     

2003—2004年冬季北半球爆发性增温期间极地平流层甲烷、水汽的演变特征

利用欧洲空间局（ESA）提供的ENVISAT/MIPAS （Michelson Interferometer for Passive Atmospheric Sounding）卫星观测数据以及ECMWF业务分析场,综合分析了2003—2004年冬季北半球爆发性增温（SSW）事件中极地平流层大气甲烷和水汽的演变特征.结果表明：（1）增温出现时,平流层高、中层极涡先后发生分裂,对应的甲烷、水汽极值中心也同时发生分裂;（2）增温下传过程中,平流层中上层甲烷、水汽同时具有“向上输送”的特征,这主要是由极地平流层的上升运动造成;增温过程中行星波活动引起的向极输送造成这种“向上输送”特征在高层具有一定的超前性;（3）增温后期,高层极涡迅速恢复,极涡内的下沉运动将中间层低层的空气（甲烷、水汽浓度极低）输送进入平流层,造成平流层高层极涡（52km附近）内出现甲烷、水汽浓度的异常低值.     

2008年1―2月雪灾作物灾情遥感监测方法

文章利用北京1号遥感数据以及MODIS数据提取作物雪灾灾情的范围，并利用1月上旬的北京1号遥感数据监测作物种植成数，利用GVG农情采样系统调查作物受灾比例，然后结合耕地数据库计算了江西、湖北、湖南和贵州4个重点省份的作物受灾面积，分析了受灾的程度和影响因素。监测结果表明：江西、湖北、湖南和贵州4省农作物受灾总面积约429.76×104 hm2，此次雪灾造成的作物受害地区主要分布在冬小麦和油菜广泛种植的江汉平原、洞庭湖和鄱阳湖地区，作物受灾严重地区主要分布在海拔相对较高的山区和丘陵地带。比较而言，冬小麦因处     

基于平流层环流变化的夏季长江下游强降水频数气候预测模型

采用相关分析方法,研究了6~8月长江下游强降水频数与前期冬季12~2月全球50 hPa纬向风的关系;并研制了基于KLM滤波的夏季长江下游强降水频数气候预测模型。结果表明,存在3个显著的相关区:北极附近,北太平洋中纬度和南半球高纬度地区。用这些前期12~2月全球平流层关键区的纬向风建立KLM预测模型进行预测试验,发现它对近10年6~8月长江下游地区强降水频数的变化具有较好的预测能力,明显优于多变量的线性回归预测;其中与北极附近和南半球高纬度地区平流层纬向风相关稳定,而与北太平洋中纬度纬向风的相关存在一定程度的不稳定。基于平流层环流变化的夏季长江下游强降水频数KLM模型可以为短期气候预测业务预报提供重要参考。     

从2008年初我国南方雪灾反思上海城市气象灾害的防御

从2008年初发生在我国南方及上海市冰冻雨雪灾害谈起,分析了这次灾害的特点和形成原因,指出在社会应对灾害、中长期天气预报能力和气象专业预报服务等方面暴露出的一些问题和薄弱环节.介绍了上海地区主要气象灾害的特点,强调防御气象灾害的重要性,提出了如何进一步加强我市气象灾害的预报预测能力、加强社会多部门的气象防灾减灾联动机制、加大气象灾害防御知识宣传等方面的一些建议.     

全球环流异常特征及其与中国气候变化的关系

采用球谐函数展开方法对1948—2009年NCEP/NCAR(美国国家环境预报中心/美国国家大气研究中心)高度距平场再分析资料进行分析,通过"时间-高度"的二维坐标方式考察环流异常的立体结构特征,发现南、北半球大气环流在1980年前后发生了明显的正负位相(槽脊)突变.与中国冬季温度和夏季降水的相关分析表明:前期春、夏、秋季的北半球环流纬向正异常越强,华北地区的冬季气温越高,反之越低;前一年冬季环流异常与华北—河套地区的夏季降水呈现反相关,春季北半球均匀异常环流与华北及西南夏季降水呈现反相关;大气环流的纬向异常与华北—河套地区的夏季降水呈现正相关,而同期环流异常与华北东部、西南及江南北部的降水呈现负相关.     

宁夏冬季气温变化与大气环流异常的关系

利用1961~2015年冬季(12月到次年2月)宁夏20个气象站月平均气温资料,NCEP/NCAR发布的500 h Pa位势高度场和海平面气压场,200 h Pa、850 h Pa风场月平均再分析资料,运用线性倾向估计、M-K法及合成分析等方法,在研究宁夏冬季平均气温的年际变化及年代际变化特征的基础上,分突变前后的冷、暖期时段进一步分析大气环流场不同影响因子与宁夏冬季气温异常的关系,揭示宁夏冬季气温异常的成因。结果表明:(1)宁夏冬季平均气温由冷变暖的趋势非常显著,在1985年之前为冷期,1985年以后为暖期;冬季平均气温年代际变化在20世纪增暖趋势显著,21世纪后上升趋势趋于平缓。(2)不仅500 h Pa位势高度场的乌拉尔山高压脊和西太平洋副高是影响宁夏冬季气温异常的主要系统,海平面气压场的西伯利亚高压也是影响宁夏冬季气温异常的关键系统;高低空的偏北气流和偏南暖湿气流异常流场也对宁夏冬季气温变化造成一定影响。     

Relationship between structural order and the anomalies of liquid water

In contrast to crystalline solids--for which a precise framework exists for describing structure--quantifying structural order in liquids and glasses has proved more difficult because even though such systems possess short-range order, they lack long-range crystalline order. Some progress has been made using model systems of hard spheres, but it remains difficult to describe accurately liquids such as water, where directional attractions (hydrogen bonds) combine with short-range repulsions to determine the relative orientation of neighbouring molecules as well as their instantaneous separation. This difficulty is particularly relevant when discussing the anomalous kinetic and thermodynamic properties of water, which have long been interpreted qualitatively in terms of underlying structural causes. Here we attempt to gain a quantitative understanding of these structure-property relationships through the study of translational and orientational order in a models of water. Using molecular dynamics simulations, we identify a structurally anomalous region--bounded by loci of maximum orientational order (at low densities) and minimum translational order (at high densities)--in which order decreases on compression, and where orientational and translational order are strongly coupled. This region encloses the entire range of temperatures and densities for which the anomalous diffusivity and thermal expansion coefficient of water are observed, and enables us to quantify the degree of structural order needed for these anomalies to occur. We also find that these structural, kinetic and thermodynamic anomalies constitute a cascade: they occur consecutively as the degree of order is increased.     

Water vapor image of snow storm process over southern Tibet

The northward movement of the storm over Bengal Bay was the main weather system producing heavy snow over southern Tibet in Nov. 1995. The effect of the Tibetan Plateau on the track of the storm over Bengal Bay and its cloud system was discussed by analyzing the GMS-5 water vapor image. It is estimated from this discussion that the altitude of the Plateau obstruct effect on synoptic system can reach up to 300 hPa.     

Relationship between Hadley circulation and sea ice extent in the Bering Sea

The linkage between Hadley circulation （HC） and sea ice extent in the Bering Sea during March-April is investigated through an analysis of observed data in this research. It is found that HC is negatively correlated to the sea ice extent in the Bering Sea, namely, strong （weak） HC is corresponding to less （more） sea ice in the Bering Sea. The present study also addresses the large-scale atmospheric general circulation changes underlying the relationship between HC and sea ice in the Bering Sea. It follows that a positive phase of HC corresponds to westward located Aleutian low, anomalous southerlies over the eastern North Pacific and higher temperature in the Bering Sea, providing unfavorable atmospheric and thermal conditions for the sea ice forming, and thus sea ice extent in the Bering Sea is decreased, and vice versa. In addition, it is further identified that East Asian-North Pacific-North America teleconnection may play an important role in linking HC and changes of atmospheric circulations as well as sea ice in the Bering Sea.     

风暴潮与天文潮非线性相互作用的理论分析

对一维狭长半封闭水域中的风暴潮与天文潮非线性相互作用问题进行了研究,并用摄动方法求出了纯风暴潮增水善s、天文潮增水h及风暴潮与天文潮非线性相互作用形成的增水善sr的一阶近似解析表达式．通过三者表达式的分析,直观地讨论了浅水效应、非线性效应在风暴潮与天文潮非线性相互作用中的影响．结果表明,浅水效应对增水水位起主要作用,非线性效应对增水的作用取决于波幅与水深比值的量阶．     

Relationship between the tropical cyclone genesis over the Northwest Pacific and the sea surface temperature anomalies

Using the tropical cyclone (TC) data derived from the Joint Typhoon Warning Center (JTWC) and the sea surface temperature data derived from the Joint Environmental Data Analysis Center (JEDAC) at the Scripps Institute of Oceanography from January 1955 to December 2000, we analyzed the relationship between the TC genesis over the Northwest Pacific (NWP) and the sea surface temperature anomalies (SSTA) over the Pacific basin. A long-term trend indicated that the highest frequency of monthly TC genesis appeared earlier and the annual genesis sum increased gradually during the last half century with some oscillations. No significant synchronous correlation was found between the NWP TC events and the SSTA over the Pacific basin, while the annual sum of TC genesis was closely related with the SSTA averaged from the first three months (January, February and March) of the year in the equatorial western and eastern Pacific and over mid-high latitudes of the North Pacific. The results implied that there are an interannual El Nio SSTA mode in the equatorial western and eastern Pacific and an interdecadal SSTA mode in the northern Pacific, which affected the TC genesis. A regression analysis between the first three-month SSTA and the annual TC sum based on two time scales was conducted. The correlation coefficient between simulated and observed TC sums reached a high value of 0.77.     

Relationship between the tropical cyclone genesis over the Northwest Pacific and the sea surface temperature anomalies

Using the tropical cyclone (TC) data derived from the Joint Typhoon Warning Center (JTWC) and the sea surface temperature data derived from the Joint Environmental Data Analysis Center (JEDAC) at the Scripps Institute of Oceanography from January 1955 to December 2000, we analyzed the relationship between the TC genesis over the Northwest Pacific (NWP) and the sea surface temperature anomalies (SSTA) over the Pacific basin. A long-term trend indicated that the highest frequency of monthly TC genesis appeared earlier and the annual genesis sum increased gradually during the last half century with some oscillations. No significant synchronous correlation was found between the NWP TC events and the SSTA over the Pacific basin, while the annual sum of TC genesis was closely related with the SSTA averaged from the first three months (January, February and March) of the year in the equatorial western and eastern Pacific and over mid-high latitudes of the North Pacific. The results implied that there are an interannual El Nio SSTA mode in the equatorial western and eastern Pacific and an interdecadal SSTA mode in the northern Pacific, which affected the TC genesis. A regression analysis between the first three-month SSTA and the annual TC sum based on two time scales was conducted. The correlation coefficient between simulated and observed TC sums reached a high value of 0.77.     

雪灾对武夷山常绿阔叶林土壤有效氮的影响

雪灾是一种重要的自然干扰类型,通过改变资源的有效性和异质性而对森林生态系统过程产生显著影响。笔者以福建武夷山的常绿阔叶林为试验地,探讨雪灾干扰后不同土层(0~10 cm、10~25 cm和25~40 cm)常绿阔叶林土壤微生物生物量氮和可溶性氮的变化。结果表明:受灾常绿阔叶林土壤微生物生物量氮、可溶性有机氮、铵态氮含量除25~40 cm土层外都显著高于对照,随土层深度的增加而减少;受灾常绿阔叶林各土层土壤硝态氮含量与对照无显著差异。相关分析显示土壤微生物生物量氮、可溶性有机氮、铵态氮含量均与土壤温度、土壤湿度呈极显著正相关。研究结果表明,由于雪灾导致了土壤温度和湿度的改变,土壤中的氮可能以铵盐和可溶性有机氮的形式从生态系统中流失。     

大气环流对冬季黑潮延伸体海温异常的响应

利用全球大气环流模式CAM3,研究了冬季北半球大气环流和东亚副热带西风急流对同期黑潮延伸体海温异常增暖响应的敏感性及东亚西风急流的响应机理.结果表明,模式能较好地刻画冬季黑潮延伸体海温异常增暖导致的北半球大气环流异常,特别是中纬地区大气环流异常“+、-”相问的分布特征.中高纬是大气对冬季黑潮延伸体海温异常响应的敏感区,...     

雪灾对毛竹林土壤呼吸与微生物生物量碳的影响

2008年中国南方雪灾是对森林生态系统过程一次极大的自然干扰。为研究雪灾对土壤主要生态因子和土壤生态学过程的影响,笔者对福建武夷山受雪灾干扰的毛竹林生态系统受灾程度进行了调查。依据毛竹林分的受灾程度,分为重度、中度和轻度3种类型。结果显示：雪灾后,重度、中度与轻度受灾毛竹林的受损率分别为43.7 %、21.8 %和10.3 %;因雪灾输入林地地表的生物量分别为2.21、1.04和0.60 kg/m2;受灾程度不同对毛竹林生态系统的主要生态因子影响有显著的差异。林分郁闭度分别与土壤含水率、土壤呼吸、土壤温度、微生物生物量碳、受损率、雪灾后输入地表生物量等呈显著负相关;雪灾后输入地表生物量分别与微生物生物量碳、土壤温度、受损率、土壤呼吸呈显著正相关。不同程度受灾林分间的土壤呼吸和微生物生物量碳有显著差异性,林冠的打开和大量凋落物、粗木质残体碎屑的输入直接或间接导致了土壤含水率、土壤温度、土壤呼吸、微生物生物量碳等生态因子的变化,这些变化将改变竹林生态系统的生物学与生态学过程。