共查询到20条相似文献，搜索用时 656 毫秒
1.
《大气科学进展》2013,(6):1821-1831
A. P. LINGASWAMY; see B. S. K. REDDY et al.; （1）, 235-246 AN Junling; LI Ying; CHEN Yong; LI Jian; QU Yu; TANG Yujia; Enhancements of Major Aerosol Components Due to Additional HONO Sources in the North China Plain and Implications for Visi- bility and Haze; （1）, 57-66 相似文献
2.
3.
陶跃跃 《南京气象学院学报》2018,10(6):723-730
本文研究了一类具有异步控制器的离散马尔可夫Lur''e跳变系统的稳定性及l2增益性能.通过引入隐马尔可夫模型（HHM）来描述所设计的控制器和原始系统之间出现的异步现象.利用线性矩阵不等式（LMI）方法分析了闭环系统的稳定性和l2增益性能.然后提出了一个充分条件使得闭环系统随机稳定,并使得从扰动到系统输出的l2增益达到最小.同时,通过求解给定条件来设计一个由线性状态反馈和扇形有界非线性输出反馈组成的异步控制器.最后,给出了一个数值仿真例子来验证所提方法的有效性. 相似文献
4.
本文研究非线性多智能体系统在有向拓扑下的领导跟随H∞一致性问题.首先,提出一种新的多项式模糊建模方法来描述由领导者与跟随者构建的偏差动态系统.然后,设计一致控制协议使跟随者渐近跟踪领导者的轨迹.基于多项式李雅普诺夫函数技术,提出松弛的渐近一致的充分条件并确保存在外界干扰时多智能体系统具有H∞抑制性能.将导出的条件转化为平方和形式并能够进行数值求解.最后,给出一个实例来验证所提出的一致控制协议的有效性. 相似文献
5.
传统的空气质量模型多使用简化的光化学反应机制来模拟大气污染物的形成.这些机制主要基于烟雾箱实验拟合的反应速率和产物来模拟二次产物（如臭氧（O3））前体物的氧化反应,具有一定的不确定性,导致模拟结果产生偏差.针对该问题,本研究将详细的大气化学机理（MCMv3.3.1）与美国国家环境保护局研制的第三代空气质量预报和评估系统CMAQ相结合（CMAQ-MCM）,模拟研究长三角地区2015年8月27—9月5日臭氧高发时段的空气质量.CMAQ-MCM模型可以较好地模拟长三角地区6个代表城市O3和其前体物随时间的变化趋势.对模拟的O3日最大8 h平均浓度的统计分析表明,徐州表现最好（标准平均误差=-0.15,标准平均偏差=0.23）.在长三角地区,居民源对挥发性有机物（VOCs）的贡献最大,占39.08%,其次是交通运输（33.25%）和工业（25.56%）.能源对总VOCs的贡献最小,约为2.11%.对活性氧化氮（NOy）的分析表明,其主要组分是NOx（80%）,其次是硝酸（HNO3）（<10%）.O3的空间分布与NOy和NOx非常相似.HCHO等其他氧化产物的分布与NOx相似,这很可能是由于在高NOx条件下VOCs氧化产生的产物.甲基乙烯基酮（MVK）和甲基丙烯醛（MACR）的空间分布与自然源VOCs （BVOCs）非常相似,表明长三角地区MVK和MACR主要由BVOCs氧化生成.长三角地区受到人为源和自然源排放相互作用的影响. 相似文献
6.
7.
Xu Xiangde 《Acta Meteorologica Sinica》1991,5(5):638-648
In this paper,the effects of first and second meridional derivative(i.e.hsu,d2f/dy2,u″)of the Coriolis parameter,Westerly profile and topography structure on ray routes are qualitatively analysed by use of a simplified mathematical model.The analysis indicates that the second derivatives of the above relevant factors play an important role in the formation of great circle route.A profile of west wind similar to the real atmosphere may result in a "sine wave pattern" of ray.The effects of west wind shear,β factor and the slope of topography on the scale of radius of great circle,critical latitude of rays ard the amplitude of wave train of teleconnection are also discussed.Additionally,the characters of critical velocity profile for meridionally trapped wave are mentioned. 相似文献
8.
Statistic and typical-year composition methods are used to study the northwest Pacific typhoon activities in relation with the EI Niño and La Niña events. The result indicates that the typhoon tends to be inactive in the EI Niño years and active in the La Niña years and it is also dependent on the onset and ending time and intensity of the events and areas of genesis of typhoons. With statistic features of the frequency of typhoon activity in the EI Niño and La Niña years and the time-lag correlation between the frequency and sea surface temperature(SST), useful information is provided for the prediction of typhoon occurrence. In addition, the singular values disassemble(SVD)method is applied to study the correlation between the geopotential field and SST field. The result shows that the air-sea coupling in the EI Niño years is unfavorable for the typhoon to develop. Which take place with a smaller number. Opposite situations are found with the La Niña years. 相似文献
9.
Impact of increasing stratospheric water vapor on ozone depletion and temperature change 总被引：2，自引：0，他引：2
Using a detailed, fully coupled chemistry climate model (CCM), the effect of increasing
stratospheric H2O on ozone and temperature is investigated. Different CCM time-slice runs have
been performed to investigate the chemical and radiative impacts of an assumed 2 ppmv increase in
H2O. The chemical effects of this H2O increase lead to an overall decrease of the total column ozone
(TCO) by ～1% in the tropics and by a maximum of 12% at southern high latitudes. At northern high
latitudes, the TCO is increased by only up to 5% due to stronger transport in the Arctic. A 2-ppmv H2O
increase in the model's radiation scheme causes a cooling of the tropical stratosphere of no more than 2 K,
but a cooling of more than 4 K at high latitudes. Consequently, the TCO is increased by about 2%--6%.
Increasing stratospheric H2O, therefore, cools the stratosphere both directly and indirectly, except in
the polar regions where the temperature responds differently due to feedbacks between ozone and H2O changes.
The combined chemical and radiative effects of increasing H2O may give rise to more cooling in the tropics
and middle latitudes but less cooling in the polar stratosphere. The combined effects of H2O increases on
ozone tend to offset each other, except in the Arctic stratosphere where both the radiative and chemical
impacts give rise to increased ozone. The chemical and radiative effects of increasing H2O cause dynamical
responses in the stratosphere with an evident hemispheric asymmetry. In terms of ozone recovery, increasing
the stratospheric H2O is likely to accelerate the recovery in the northern high latitudes and delay it in
the southern high latitudes. The modeled ozone recovery is more significant between 2000--2050 than between
2050--2100, driven mainly by the larger relative change in chlorine in the earlier period. 相似文献
10.
Variance analysis, correlation analysis and regression analysis methods are applied to analyze the
variation of circulation at 500 hPa. In winter, there are three regions (180°E – 150°W, 45°N – 60°N, 70°W – 100
°W，45°N – 75°N, 60°E – 100°E, 65°N – 80°N) whose variations are strong. Those regions are the key regions in
which atmospheric circulation can change. Those regions are correlated to some teleconnections and can present
a part of variations of 500 hPa to some degree. The linear contemporary correlation between those regions and the
height at 500 hPa is significant. Those regions can account for 88 % of variations of concurrent height at 500 hPa.
Those regions can present and forecast some variations to some degree in March and April. The longer the time
interval, the worse the forecast effect will be. The interannual variations of Q1, Q2 and the SST are weak in the
western Pacific. 相似文献
11.
本文考虑了拒绝服务攻击下的网络化控制系统的H∞输出反馈控制问题.拒绝服务攻击的特征表现为能量有限和周期类型,它攻击无线网络通道进而退化系统性能.在系统状态部分未知的前提下,为了保证被控系统的稳定性和H∞性能指标,通过设计基于观测器输出反馈控制器,使得网络化控制系统在丢包和拒绝服务攻击下仍然保持稳定和预定性能.最后数值例子验证了所设计的控制器是有效的. 相似文献
12.
The characteristics of net radiation (Rn)(0.3--10 μm) in Lhasa and
Haibei in the Tibetan Plateau were analyzed based on long-term in-situ
measurements of surface radiation data. The monthly average of daily
Rn reached a minimum during the winter period followed by an increase
until May and then a decline until January. This variation is consistent
with solar activity. The annual mean daily total Rn values were 0.92 MJ
m-2 d-1 and 0.66 MJ m-2d-1 in Lhasa and Haibei,
respectively.
A relationship between Rn and broadband solar radiation (Rs) was
demonstrated by a good linear correlation at the two sites. Rn can be an
accurate estimate from Rs. The estimated Rn values were similar to the
observed values, and the relative deviations between the estimates and
measurements of Rn were 2.8% and 3.8% in Lhasa and Haibei,
respectively. The application of the Rn estimating model to other
locations showed that it could provide acceptable estimated Rn values from the Rs data. Furthermore, we analyzed the influence of clouds on
Rn by different clear index (Ks), defined as the ratio of Rs to the
extraterrestrial solar irradiance on a horizontal surface. The results
indicate that more accurate results are associated with increased cloudy
conditions. The influence of the albedo was also considered, but its
inclusion in the model resulted in only a slight improvement. Because
surface albedo is not usually measured, an expression based solely on global
solar radiation could be of more extensive use. 相似文献
13.
Samples of fog water collected in the area of Guangzhou during February, March and April of
2005 are used in this work to study the chemical composition of fog water in polluting fog there. Three
typical episodes of polluting fog are analyzed in terms of ionic concentration and their possible sources. It
is found that the concentration of various ions in fog water is much higher than those in rainwater. Fog not
only blocks visual range but contains liquid particles that result in high degree of pollution and are very
harmful to human health. SO4= is the anion with the highest concentration in fog water, followed by NO3-.For the cation, Ca++ and NH4+ are the highest in concentration. It is then known that rainwater is more
acidic than fog water, indicating that ionic concentration of fog water is much higher than that of rainwater,
but there are much more buffering materials in fog water, like NH4+ and Ca++. There is significant
enrichment of Ca++, SO4=, and Mg++ in fog water. In the Guangzhou area, fog water from polluting fog is
mainly influenced continental environment and human activity. The episodes of serious fog pollution
during the time have immediate relationships with the presence of abundant water vapor and large amount
of polluting aerosol particles. 相似文献
14.
The energetics process of offehore typhoon in three kinds of explosive enhancement (TEE) are ana lyzed using ECMWF data. The results are as follows: (a) During the explosive development process,the enhancement of the rotational kinetic enersy (KW) is mainly in the lower troposphere while that ofthe potential energy (PE) is in the upper troposphere. The magnitude of rotational kinetic energy islargely bigger than that of divergent enersy (KΧ). (b) The environmental energy advected into the typhoon was about 30% of the internal increment of typhoon energy. The magnitude of energy was an order larger than increment of typhoon energy. (c) Among those three kinds of explosively developed typhoon, the enersy transformation mechanisms are different. (d) The influence of environment fields onabrupt intensification of typhoons couldn't be overestimated. 相似文献
15.
本文介绍了一种低剖面小型化圆盘加载单极子天线.通过盘加载的方式,在中心频率5.8 GHz处,首先将单极子天线的剖面从大约12.9 mm（0.25λ0）降低到2 mm（0.039λ0）,实现了低剖面的特性.加载在单极子天线上方的圆盘,尺寸大概为21 mm（0.41λ0）,因此天线具有结构紧凑的特点.接着,为了使天线具有良好的匹配,在加载圆盘四周加入4个接地通孔,并且在馈电端口加入集总电感.最终,天线在中心工作频率5.8 GHz处实现了反射系数-15 dB的匹配性能. 相似文献
16.
过氧乙酰硝酸酯（PAN）是由VOCs和NOx的光化学反应生成的一种典型二次污染物,比O3更适合作为光化学污染的指示剂.2019年6—10月对浙江中部盆地金华市大气中PAN进行了在线监测,并对影响其体积分数变化的因素进行了分析,同时还分析了一次典型的光化学污染过程.结果表明,观测期间PAN的平均体积分数为0.656×10-9,最高体积分数为4.348×10-9,日均体积分数水平在0.130×10-9~2.203×10-9之间.PAN日变化特征显著,9月为明显的双峰变化,其他月份均为单峰.受气象条件的影响,夏季的污染程度显著低于秋季.9月27—30日典型污染时段内,PAN的小时均值是整个观测期均值的2.8倍,污染以本地积累为主.前体物浓度水平差异与去除机制的不同是影响PAN和O3相关性的重要因素,此外NO/NO2的比值是影响PAN生成速率的重要因素,PAN的峰值基本出现在NO/NO2比值较低的时段.在生成PAN的VOCs物种中,丙烷、乙烷和间/对二甲苯所占比例较大. 相似文献
17.
In this study, a regional air quality model system (RAQMS) was
applied to investigate the spatial distributions and seasonal variations of
atmospheric aerosols in 2006 over East Asia. Model validations demonstrated
that RAQMS was able to reproduce the evolution processes of aerosol components
reasonably well. Ground-level PM10 (particles with aerodynamic diameter
≤10 μm) concentrations were highest in spring and lowest in
summer and were characterized by three maximum centers: the Taklimakan Desert
(～1000 μg m-3), the Gobi Desert (～400 μg m-3), and
the Huabei Plain (～300 μm-3) of China. Vertically, high
PM10 concentrations ranging from 100 μg m-3 to 250 μg
m-3 occurred from the surface to an altitude of 6000 m at
30o--45oN in spring. In winter, the vertical gradient was so
large that most aerosols were restricted in the boundary layer. Both sulfate
and ammonium reached their highest concentrations in autumn, while nitrate
reached its maximum level in winter. Black carbon and organic carbon aerosol
concentrations reached maximums in winter. Soil dust were strongest in spring,
whereas sea salt exerted the strongest influence on the coastal regions of
eastern China in summer. The estimated burden of anthropogenic aerosols was
largest in winter (1621 Gg) and smallest in summer (1040 Gg). The sulfate
burden accounted for ～42% of the total anthropogenic aerosol burden. The
dust burden was about twice the anthropogenic aerosol burden, implying the
potentially important impacts of the natural aerosols on air quality and
climate over East Asia. 相似文献
18.
分析了高等学校内部分配制度改革的一些基本模式及存在的问题,说明了进一步深化高校内部分配制度改革的重要性,并提出建议:1.高校内部分配制度改革应体现"以人为本"的理念;2.完善配套的人事制度改革措施;3.建立向优秀人才倾斜的分配激励机制;4.内部分配制度必须反映学科的不同差异,尊重学术工作的不同特性;5.内部分配制度必须发展相应的公平和可操作的评估计划;6.内部分配制度改革应反映院系工作重点,确保院系工作重点与教师合理利用时间的适当配合;7.制定系统、完整的文件,规范操作。 相似文献
19.
Monthly mean zonal wind data from the European Center for Medium-range Weather Forecasting(ECMWF)for December 1982, April 1983, October 1984 and ApriI 1985 are used in numerical integration as thebasic flow in a non-linear critical-layer model. The subtropical high is extensive and limited in number if simulated with the basic now in December 1982 and April 1983. It consists of 2 to 3 cells that move westward at alloscillatory periods of 1～2 months. The subtropical high, simulated with the basic flow in October 1984 and April1 985. is weak and small in coverage, or distributed in strips that contain up to 4 cells. The high. merged or spillover a short time. is moving westward. The years 1982 ～1983 are a process of EI Niño while the years 1984-1985one of La Niña. lt is known from the chart of energy flux that it oscillates by a much larger amplitude and longerperiod in the EI Niño year than in the La Niña year. All the results above have indicated that the basic flow in the EI Niño year is enhancing the subtropical high lagging by about 4 months and that in the La Niña year is decay'ing it. It is consiStent with the well-known observational fact that the SSTA in the equatorial eastern Pacitlc ispositively correlated with the extent and intensity of the subtropical high in west Pacific lagging by 1～2 seasons.The result is also important for further study of the formation, maintenance and oscillation of the subtropicalhigh. 相似文献
20.
Using indexes of dryness and wetness in historical record over the recent recent years and rainfall data over the tatest century, the work involves itself with the study of climatological evolution of dryness and wetness. periodic variations of climate and interannual laws of variation. The discussion also covers the subjects of effects of El Nino. sunspot, predictors of general circulation on climatic variation of dryness and wetness. There arc main conclusions as follows: (1) The main cyclic variations of climate are 40 and 11 years in Kunming. the former being subject to that of El Nino and the latter to that of sunspots. They are two principal factors for periodic variations of dryness and wetness in Kunming. (2) A close relationship exists between interannual variations and general circulation factors for Kunming. The comprehensive influence as imposed by ENSO and allocations of W.C.E. patterns of circulation in the westerly are ma.tor weather and climate causes for the interannual variations of precipitation in Kunming. 相似文献