江淮之间夏季雨滴谱特征分析

分析了2011—2013年夏季(6—8月)滁州地基雨滴谱观测资料,根据雨强及其随时间的变化将降水分成对流降水和层云降水,分析不同降水类型的雨滴谱特征。结果表明:滁州地区对流降水的质量加权直径D_m和标准化参数lgN_w的平均值分别为1.67 mm和3.91 mm^-1·m^-3,层云降水D_m和lgN_w的平均值分别为1.18 mm和3.57 mm^-1·m^-3,对流降水雨滴平均尺度更大。N_w相比Γ分布参数N₀能更好地反映总数浓度N_t的大小。Γ分布3参数均随雨强的增大而减小,当雨强增长到一定程度时,μ(谱型)和Λ(斜率)趋于常数。研究了μ-Λ关系和Z(反射率因子)-R(雨强)关系。对流降水和层云降水的Z-R关系分别为Z=408R^1.20和Z=301R^1.21。新的Z-R关系和经典Z-R关系(Z=300R^1.40)反演的雨强相比实际观测值均偏小,但新的Z-R关系反演的雨强与实际观测值更接近。     

南京市城市不同功能区PM10和PM2.1质量浓度的季节变化特征

使用Anderson-Ⅱ型9级撞击采样器测量了南京市鼓楼商业区、江北工业区、钟山风景区和宁六高速公路交通源春、夏、秋三季的大气气溶胶质量浓度。分析结果表明:南京市PM_2.1和PM₁₀的质量浓度存在明显的季节变化,秋季>春季>夏季;ρ_PM10春季为167.47 μg/m³,夏季为 85.99 μg/m³,秋季为238.99 μg/m³;ρ_PM2.1春季为59.66 μg/m³,夏季为42.80 μg/m³,秋季为100.15 μg/m³。不同季节中ρ_PM10和ρ_PM2.1均存在较好的相关性,夏季相关性最好,相关系数为0.952;秋季次之,相关系数为0.783;春季相对较差,相关系数为0.613。城市不同功能区之间ρ_PM2.1和ρ_PM10的质量浓度值差异很大,交通源>工业区>商业区>风景区。城市不同功能区的质量浓度谱分布基本一致,均为双峰型分布,峰值分别位于0.43~0.65 μm/m³和9.0~10.0 μm/m³。南京市春、夏、秋三个季节大气粒子质量浓度谱为双峰分布,粒子主要集中在0.43~3.3 μm/m³的粒径段。江北工业区ρ_PM10和ρ_PM2.1质量浓度的相关系数为0.814,略高于鼓楼商业区的0.797。     

顶点Pk覆盖问题的研究综述

顶点覆盖问题是经典的NP完全问题,在排序、计算机网络等现实生活中有许多的应用.近几年来,许多研究者开始探究它的推广形式——顶点P_k覆盖（VCP_k）问题,即寻找一个顶点子集,从拓扑结构图中删除后使得剩下的顶点导出的子图不包含P_k路,其中P_k是指包含k个顶点的路.本文简单介绍了VCP_k问题的应用背景,归纳了它在近似算法、精确算法、参数化算法3个方面的主要研究进展,并分析了一些主要的方法和技巧.在此基础上,对VCP_k问题及其相关问题的研究前景进行了展望.     

一类非线性Volterra积分不等式

本文简要讨论Gronwall不等式的研究进展,并给出关于如下的一类非线性Volterra积分不等式的一个结果：w(u(t))≤g(t))+∑_i=1ⁿ∫_αi(t0)^α_i(t)f_i(t,s)∏_j=1^mH_ij(u(s))G_ij(max_s-h≤ξ≤s u (ξ))ds.     

HⅢ(2n)中元素的一种标准化表示

给出HⅢ(2n)中元素的一种标准化表示,HⅢ(2n)={Z∈C^2n×2n|1/2(Z+Z'')>0,ZJ=JZ''},J=0 I_n-I_n 0,1/2(Z+Z)>0表示矩阵1/2(Z+z'')是正定的。     

江淮地区龙卷超级单体风暴及其环境参数分析

利用多普勒雷达探测资料和NCEP再分析资料,对2003—2010年发生在江淮地区的6个龙卷超级单体风暴及其环境参数进行了分析。研究表明：（1）龙卷超级单体风暴H_BASE平均为1.7 km,H_TOP平均为9.1 km;H多在风暴的下部,近于下部的1/4处。H_BASE平均值比江淮地区各种超级单体的平均值低得多,H_TOP则略低。（2）龙卷超级单体I_VIL平均为25.6 kg/m²,Z_MX平均为54.8 dBz。和江淮地区超级单体相比,龙卷I_VIL要小得多,而龙卷Z_MX略低。（3）龙卷超级单体的中气旋M_BASE、M_TOP和M_SHR平均值分别为1.2 km、3.9 km和14.4×10^-3s^-1,和江淮地区超级单体相比,龙卷M_BASE、M_TOP明显低,而M_SHR略高。（4）TVS参数最强时的V_AD在12—45 m/s,V_LLD多大于30 m/s,V_MXD多超过30 m/s,V_MXD的高度不低于0.8 km,T_DPT在2.4—6.4 km,T_BASE在0.7—1.5 km,T_TOP在2.3—6.4 km,T_MXSHR超过22×10^-3s^-1。TVS参数最强时间与龙卷实际时间基本吻合,平均相差4.2 min;平均而言,TVS出现后6 min有龙卷发生。（5）雷达推算的龙卷超级单体的0—6 km风垂直切变比江淮地区超级单体的风垂直切变平均值高15.2%;龙卷发生前I_CAPE平均为1752 J/kg,I_K为38℃,850 hPa到地面风切变平均超过12 m/s,850—500 hPa温差平均为23.7℃。龙卷发生前能量处在中等到强的状态,大气不稳定性较强,风垂直切变大。     

2016年冬季南京地区大气污染特征的观测分析

基于2016年11月24日—12月23日南京市草场门站、鼓楼站和仙林站的强化试验观测资料,分析了城市和郊区主要大气污染物的时空变化特征及其与气象要素的相互关系。研究发现：观测期间南京PM_2.5、PM₁₀、NO₂、O₃、CO、SO₂月均质量浓度分别为52.84~84.34 μg·m^-3、88.36~120.34 μg·m^-3、49.98~51.66 μg·m^-3、24.85~50.57 μg·m^-3、0.99~1.2 mg·m^-3和22.1~26.48 μg·m^-3;近地面,城市大气污染物质量浓度高于郊区,其中城市O₃比郊区高61.0%;在城市地区,除NO₂和CO外,鼓楼站大气污染物质量浓度高于草场门站,其中鼓楼站PM_2.5比草场门站高42.7%;PM_2.5小时质量浓度最大为210.93 μg·m^-3,重污染过程出现时风速较低、温度较高,郊区PM₁₀、PM_2.5、NO₂质量浓度呈现高值时的最频风向为南风,O₃和SO₂质量浓度呈现高值时的最频风向分别为西风和西南风,所以郊区大气污染受城市输送影响。利用HYSPLIT模式研究发现12月4—8日和16—20日的污染气团分别来自西部和北方地区,聚类分析发现12月影响南京市的污染气团45%来自西部地区且移动速度较快,55%来自北方地区且移动速度较慢。由此可见,南京市冬季出现的大气污染,其形成不仅与本地排放和局地气象条件有关,而且西部和北方地区的远距离输送也会造成影响。     

黑云杉林大气CO2稳定同位素组成δ13C,δ18O的分析

研究CO₂稳定同位素特征可以揭示光合、呼吸作用等众多信息,从而有助于了解生态系统与环境之间的碳循环过程。利用大气CO₂浓度及其稳定同位素的测定资料,分析稳定同位素比δ¹³C、δ¹⁸O,发现两者具有相似的时空分布特征。主要表现在δ¹³C和δ¹⁸O在冠层内具有明显的垂直变化趋势,冠层上部重同位素含量较高,而底部含量较低。从时间变化看,δ¹³C和δ¹⁸O在午后到日落具有较高的水平,而凌晨,δ¹³C和δ¹⁸O较低。运用Keeling图法分析δ¹³C、δ¹⁸O和CO2浓度的关系,发现δ¹³C值主要受光合和呼吸作用影响,与CO₂浓度的高低密切相关;而δ¹⁸O的变化比较复杂,因为δ¹⁸O除受光合、呼吸强度影响外,还取决于环境空气湿度。     

城市下垫面影响空气污染的机制分析

本文采用RBLM-chem模式,利用杭州市高分辨率城市建筑等资料,定量分析城市动力效应、热力效应以及城市植被、人为热对SO₂、NO₂、O₃、PM_2.5等主要污染物浓度的影响。结果表明,城市化过程使得大部分城区温度上升约1℃,相对湿度下降约6%,风速下降约0.8 m·s^-1,湍流动能增强约0.03 m²·s^-2。城市动力效应主要通过降低城市风速,使得城区污染物浓度升高,SO₂浓度有近5 μg·m^-3的上升,PM_2.5、O₃浓度也有近15 μg·m^-3的上升。城市热力效应主要通过热岛环流使城区污染物向上输送,令地面污染物浓度降低,在城市大部分区域PM_2.5都有大约10 μg·m^-3的浓度下降。城市动力效应大于热力效应,城市的总体作用是使污染物浓度升高。城市下垫面使污染物浓度上升的另外一个机制是代替了自然有植被的下垫面,使污染物干沉降速度下降,但这一作用小于动力学效应。另一方面,人为热对城市主要污染物浓度都起着减小的作用,其中SO₂、NO₂、O₃、PM_2.5浓度降幅分别在2.5、3.0、6.0、10.0 μg·m^-3左右。城市植被可以显著增加污染物干沉降速度,使主要污染物SO₂、NO₂、O₃和PM_2.5的干沉降速度分别上升0.1、0.1、0.03、0.06 m·s^-1左右,相应地使上述污染物浓度分别下降2.5、6.0、4.0、6.0 μg·m^-3左右。     

UV-B辐射增强对不同品种花生结荚期生理特性日变化的影响

以3个花生品种（开农49号、64号和69号）为材料,通过大田模拟试验,研究UV-B辐射增强对花生结荚期叶片的净光合速率（P_n）、气孔导度（G_s）、胞间CO₂浓度（C_i）、蒸腾速率（T_r）和水分利用效率（E_wu）日变化的影响,为筛选高产、抗旱、抗UV-B辐射花生品种提供依据.UV-B辐射设2个水平即自然光（CK,1.5 kJ·m^-2）和UV-B增强20%（T,1.8 kJ·m^-2）.结果表明,UV-B辐射增强明显抑制花生的光合作用和蒸腾作用,与对照相比,UV-B增强条件下,开农49号、64号和69号P_n日均值分别降低19.4%、27.8%、24.7%;G_s日均值降低26.7%、42.9%、28.6%;C_i日均值降低27.2%、20.4%、23.1%;T_r日均值降低17.8%、23.3%、25.1%;E_wu日均值降低16.6%、23.2%、23.9%.UV-B辐射增强对3个品种生长都具有抑制效应,但品种间存在一定的敏感性差异,其中开农49号最不敏感,因此,开农49号在抗UV-B辐射方面比其他2个品种具有更大的优势.     

大气中硝酸盐、硫酸盐、铵和钙的浓度

1985年10月,在中国的三个不同地点用太氟龙和尼龙滤膜采样系统观测了硝酸根、硫酸根、铵和钙的浓度。平均而言,硫酸根的摩尔浓度与硝酸根的摩尔浓度之比不到2。考虑到中国燃煤大量排放SO_2这一事实,这一低比值有点出乎预料。在北京钙是最重要的阳离子,而在华北山区的兴隆天文观测站和南方城市长沙气溶胶中铵离子多于钙离子。在北风条件下,兴隆的硫酸根和硝酸根浓度与文献中报道的欧洲和北美的本底值接近。因此,兴隆天文观测站是研究亚洲大陆本底空气的理想地点。     

Wind-driven, double-gyre, ocean circulation in a reduced-gravity, 2.5-layer, lattice boltzmann model

A coupled lattice Boltzmann （LB） model with second-order accuracy is applied to the reduced-gravity, shallow water, 2.5-layer model for wind-driven double-gyre ocean circulation. By introducing the secondorder integral approximation for the collision operator, the model becomes fully explicit. The Coriolis force and other external forces are included in the model with second-order accuracy, which is consistent with the discretization accuracy of the LB equation. The feature of the multiple equilibria solutions is found in the numerical experiments under different Reynolds numbers based on this LB scheme. With the Reynolds number increasing from 3000 to 4000, the solution of this model is destabilized from the anti-symmetric double-gyre solution to the subtropic gyre solution and then to the subpolar gyre solution. The transitions between these equilibria states are also found in some parameter ranges. The time-dependent variability of the circulation based on this LB simulation is also discussed for varying viscosity regimes. The flow of this model exhibits oscillations with different timescales varying from subannual to interannual. The corresponding statistical oscillation modes are obtained by spectral analysis. By analyzing the spatiotemporal structures of these modes, it is found that the subannual oscillation with a 9-month period originates from the barotropic Rossby basin mode, and the interarmual oscillations with periods ranging from 1.5 years to 4.6 years originate from the recirculation gyre modes, which include the barotropic and the baroclinic recirculation gyre modes.     

Forest ecosystems, disturbance, and climatic change in Washington State, USA

Climatic change is likely to affect Pacific Northwest (PNW) forests in several important ways. In this paper, we address the role of climate in four forest ecosystem processes and project the effects of future climatic change on these processes across Washington State. First, we relate Douglas-fir growth to climatic limitation and suggest that where Douglas-fir is currently water-limited, growth is likely to decline due to increased summer water deficit. Second, we use existing analyses of climatic controls on tree species biogeography to demonstrate that by the mid twenty-first century, climate will be less suitable for key species in some areas of Washington. Third, we examine the relationships between climate and the area burned by fire and project climatically driven regional and sub-regional increases in area burned. Fourth, we suggest that climatic change influences mountain pine beetle (MPB) outbreaks by increasing host-tree vulnerability and by shifting the region of climate suitability upward in elevation. The increased rates of disturbance by fire and mountain pine beetle are likely to be more significant agents of changes in forests in the twenty-first century than species turnover or declines in productivity, suggesting that understanding future disturbance regimes is critical for successful adaptation to climate change.     

Anthropogenic, Climatic, and Hydrologic Trends in the Kosi Basin, Himalaya

A great debate exists concerning theinfluence of land-use and climatic changes onhydrology in the Himalayan region and its adjacentplains. As a representative basin of the Himalayas, westudied basinwide land-use, climatic and hydrologictrends over the Kosi Basin (54,000 km²) in themountainous area of the central Himalayan region. Theassessment of anthropogenic inputs showed that thepopulation of the basin grew at a compound rate ofabout one percent per annum during the past fourdecades. The comparison of land-use data between thesurveys made during the 1960s and 1978–1979 did notreveal noticeable trends in land-use change. Theanalysis of meteorological and hydrological timeseries from 1947 to 1993 showed some increasingtendency of temperature and precipitation. Thestatistical tests of hydrologic trends indicated anoverall decrease in discharge on the Kosi River andits major tributaries. The decreasing trends ofstreamflow were more significant during the low-flowmonths. The statistical analysis of homogeneityshowed that the climatic as well as the hydrologictrends were more localized in nature lacking adistinct basinwide significance.     

Nowcasting precipitation, clouds, and surface state in winter

Freezing of rainwater on a surface is often caused by nocturnal clearing after precipitation, which goes along with radiative cooling. Forecasting cloudiness, and especially the risk of clearing, on a scale of 1 to 3 h is of interest in the domains of road weather, agriculture, or water management.Cloud amount and the difference between air and surface temperature are important parameters of the radiation balance. In this contribution, we show the relationship between them, proved at several stations all over Switzerland. We found a correlation coefficient of 0.88 and improved it considering other meteorological parameters like wind speed. We conclude that temperature difference is a signature for nocturnal cloudiness.We investigated nocturnal cloudiness for a case from winter 2001/02 in northern Switzerland. An ultra-dense combination of two networks with 70 stations in total is operated, measuring air and surface temperature, wind and other parameters. With the aid of our equations, these measurements where converted into cloud maps, including also precipitation seen by radar. We identified a frontal precipitation area, postfrontal clearing, freezing, and the first clouds of a following frontal passage.All these findings will contribute to a better observation and predictability of surface state and other risks connected with radiative cooling.     

Benefits, Costs, and Cooperation in Greenhouse Gas Abatement

Abatement cost and benefit projections through 2100are computed, assembled and interpreted with respectto various levels of emission reduction. Mathematicalexpressions describing regional costs and benefits asa function of abatement strategy are developed. Usingthese data and expressions, optimal abatementstrategies are defined for noncooperative andcooperative (Pareto optimal) policies. Thecooperative solution calls for an average emissionsreduction of 16.6 percent over the 1990–2100 period,as compared to 5.8 percent in the noncooperative case. Achieving the cooperative solution would require sidepayments to China and potentially to the U.S., as wellas stringent (though beneficial) restrictions onnon-OECD countries. It is argued that Paretooptimality is technically achievable but possiblyinfeasible in the real world.     

Climate change,migration and adaptation in Funafuti,Tuvalu

This paper shows the extent to which people in Funafuti – the main island of Tuvalu – are intending to migrate in response to climate change. It presents evidence collected from Funafuti to challenge the widely held assumption that climate change is, will, or should result in large-scale migration from Tuvalu. It shows that for most people climate change is not a reason for concern, let alone a reason to migrate, and that would-be migrants do not cite climate change as a reason to leave. People in Funafuti wish to remain living in Funafuti for reasons of lifestyle, culture and identity. Concerns about the impacts of climate change are not currently a significant driver of migration from Funafuti, and do not appear to be a significant influence on those who intend to migrate in the future.     

中国古诗词中的云雾雨雪

从云雾降水物理学的角度学习和分析了一些中国古诗词。内容有:1）分析和统计了唐诗300首和毛泽东诗词中用到云雾雨雪等字的百分比,其分别占总首数的45%和66%;2）列举和分析了描述自然过程、大气过程有云雨雪等字的诗(词)句;3）从现代科学观出发,分析了在一些古诗词中有关云、雨、霜、露等的理解,并作了一些评述;4）对古诗词中直接描述云、雾、雨、雪的内容进行了评论。       

从气候变化的新视角理解灾害风险、暴露度、脆弱性和恢复力

不断变化的气候可导致前所未有的极端天气和气候事件。这些事件能否构成灾害,在很大程度上取决于脆弱性和暴露度水平。虽然无法完全消除各种灾害风险,但灾害风险管理和气候变化适应的重点是减少脆弱性和暴露度,并提高对各种潜在极端事件不利影响的恢复力,从而促进社会和经济的可持续发展。全面的灾害风险管理要求更加合理地分配对减灾、灾害管理等方面所付出的努力。过去的主流是强调灾害管理,但目前减灾成为关注焦点和挑战。这种主动积极的灾害风险管理与适应有助于避免未来的风险和灾害,而不仅仅是减少已有的风险和灾害,同时这也是灾害风险管理和气候变化适应更加紧密联系的一个背景。灾害风险管理促进气候变化适应从应对当前的影响中汲取经验,而气候变化适应帮助灾害风险管理更加有效地应对未来变化的条件。     

Aridity in Vojvodina, Serbia

For investigating aridity in Vojvodina, two parameters were used: the De Martonne aridity index and the Pinna combinative index. These indices were chosen as the most suitable for the analysis of climate in Vojvodina (a region in northern part of Serbia). Also, these indices were calculated from data obtained from 10 meteorological stations for the period from 1949 to 2006. The spatial distribution of the annual and seasonal De Martonne and the Pinna combinative indices as well as the mean monthly values of the De Martonne index and aridity trends of these indices are presented. There were two, four, and five types of climate on a yearly, seasonal, and monthly basis in Vojvodina, according to the De Martonne climate classification which consists of a total of seven types. In addition, semi-humid and humid climate types were represented in the region, on a yearly basis. The winter season was dominated by wetter types of climate, while the summer season was characterized by drier ones. During the spring and autumn seasons, there were types of climate which range between both aforementioned types. Two out of three climate types, which can be identified using the Pinna combinative index, were registered in Vojvodina region. The most dominant climate type was the semidry Mediterranean with formal Mediterranean vegetation, while the humid type was only identified in one small part of southwestern Vojvodina. The calculated values of both aridity indices showed that there were no annual trends. Therefore, it can be considered that there were no recent aridity changes during the observed period. For paleoclimate, the general story is more complex. The lack of aridity trends in the recent period from 1949 to 2006 supports the fact that Vojvodina has very well preserved loess–palaeosol sequences from the Middle and Late Pleistocene, which indicates that crucial point for their preservation was caused by the weak aridity variability in the region.