两次台风过程近地层湍流度和阵风因子分析   总被引：4，自引：0，他引：4  

黄世成  周嘉陵  王咏青  刘建波  张杰 《气象科学》2009,29(4):454-460

利用2005年台风"麦莎"和"卡努"期间青岛海岸实测三维风观测资料,挑选6个10 min平均风速≥8 m/s的强风时段,使用矢量分析方法研究台风影响华东地区时近地层的平均风速风向变化、湍流度和阵风因子变化等湍流特性,结果表明台风影响期间,近地层湍流脉动风速不稳定,水平方向、垂直方向风速风向快速变化;虽然台风"麦莎"、"卡努"入海地点不同,不同强风时段近地层湍流度差异也较大,但湍流强度都表现为Iu(横向)＞Iv(纵向)＞Iw(垂直向).两次台风影响过程不同强风时段近地层阵风因子的变化与湍流度的变化是一致的,在风速增大风向转变的时段,湍流度和阵风因子明显增大.  相似文献   

Detecting inhomogeneity in daily climate series using wavelet analysis   总被引：1，自引：0，他引：1  

严中伟 《大气科学进展》2008,25(2):157-163

A wavelet method was applied to detect inhomogeneities in daily meteorological series, data which are being increasingly applied in studies of climate extremes. The wavelet method has been applied to a few well- established long-term daily temperature series back to the 18th century, which have been ＂homogenized＂ with conventional approaches. Various types of problems remaining in the series were revealed with the wavelet method. Their influences on analyses of change in climate extremes are discussed. The results have importance for understanding issues in conventional climate data processing and for development of improved methods of homogenization in order to improve analysis of climate extremes based on daily data.  相似文献   

Impacts of Multi-Scale Solar Activity on Climate. Part I: Atmospheric Circulation Patterns and Climate Extremes     

Hengyi WENG 《大气科学进展》2012,29(4):867-886

The impacts of solar activity on climate are explored in this two-part study.Based on the principles of atmospheric dynamics,Part I propose an amplifying mechanism of solar impacts on winter climate extremes through changing the atmospheric circulation patterns.This mechanism is supported by data analysis of the sunspot number up to the predicted Solar Cycle 24,the historical surface temperature data,and atmospheric variables of NCEP/NCAR Reanalysis up to the February 2011 for the Northern Hemisphere winters.For low solar activity,the thermal contrast between the low-and high-latitudes is enhanced,so as the mid-latitude baroclinic ultra-long wave activity.The land-ocean thermal contrast is also enhanced,which amplifies the topographic waves.The enhanced mid-latitude waves in turn enhance the meridional heat transport from the low to high latitudes,making the atmospheric "heat engine" more efficient than normal.The jets shift southward and the polar vortex is weakened.The Northern Annular Mode(NAM) index tends to be negative.The mid-latitude surface exhibits large-scale convergence and updrafts,which favor extreme weather/climate events to occur.The thermally driven Siberian high is enhanced,which enhances the East Asian winter monsoon(EAWM).For high solar activity,the mid-latitude circulation patterns are less wavy with less meridional transport.The NAM tends to be positive,and the Siberian high and the EAWM tend to be weaker than normal.Thus the extreme weather/climate events for high solar activity occur in different regions with different severity from those for low solar activity.The solar influence on the midto high-latitude surface temperature and circulations can stand out after removing the influence from the El Nin o-Southern Oscillation.The atmospheric amplifying mechanism indicates that the solar impacts on climate should not be simply estimated by the magnitude of the change in the solar radiation over solar cycles when it is compared with other external radiative forcings that do not influence the climate in the same way as the sun does.  相似文献   

1960-2005年长江流域降水极值概率分布特征   总被引：1，自引：1，他引：0  

苏布达  Marco Gemmer  姜彤  Ren Guoyu 《气候变化研究进展》2008,4(Z1)

Based on the daily observational precipitation data of 147 stations in the Yangtze River basin for 1960-2005,and the projected daily data of 79 grids from ECHAM5/MPI-OM in the 20th century,time series of precipitation extremes which contain annual maximum(AM)and Munger index(MI)were constructed.The distribution feature of precipitation extremes was analyzed based on the two index series.Research results show that(1)the intensity and probability of extreme heavy precipitation are higher in the middle Mintuo River sub-catchment,the Dongting Lake area,the mid-lower main stream section of the Yangtze River,and the southeastern Poyang Lake sub-catchment;whereas,the intensity and probability of drought events are higher in the mid-lower Jinsha River sub-catchment and the Jialing River sub-catchment;(2)compared with observational data,the averaged value of AM is higher but the deviation coefficient is lower in projected data,and the center of precipitation extremes moves northwards;(3)in spite of certain differences in the spatial distributions of observed and projected precipitation extremes,by applying General Extreme Value(GEV)and Wakeby(WAK)models with the method of L-Moment Estimator(LME)to the precipitation extremes,it is proved that WAK can simulate the probability distribution of precipitation extremes calculated from both observed and projected data quite well.The WAK could be an important function for estimating the precipitation extreme events in the Yangtze River basin under future climatic scenarios.  相似文献   

Measurement of Solar and Cosmic Radiation during Spaceflight     

Donat-P. Häder  Tsvetan Dachev 《Surveys in Geophysics》2003,24(3):229-246

The external platform of the International Space Station (ISS) will provide aunique opportunity for exobiological studies under space conditions, e.g., spacevacuum, solar UV radiation, cosmic radiation, and temperature extremes. In orderto facilitate this research, ESA is developing the EXPOSE facility to be attachedto the External Pallet of the truss structure of the ISS. The experiment is plannedfor a duration of 18 months during the ISS early utilization period. Experimentson the ``Responses of Organisms to the Space Environment (ROSE)' will studythe survival of spores from bacteria, fungi, ferns, etc., under space conditions andthus investigate whether life could potentially survive extended travel through space.In parallel to the exposure of the biological material, the charged particle and solarextraterrestrial radiation will be measured with a multichannel dosimeter. Thisinstrument is based on two separate developments. The dosimeter which determinessolar radiation in four channels is based on the ground-based ELDONET (Europeanlight dosimeter network) instrument which has been developed to measure solar UVand visible radiation in three channels. The other part of the instrument is based on a256 channel dosimeter of cosmic radiation which was developed and used on theRussian space station Mir. A final miniature prototype has been developed to fit thespace available. The instrument incorporates the latest technologies such as SurfaceMounted Devices (SMDs), switchable amplifiers, as well as on-board microprocessorcontrol. Several software packages have been developed to record the solar visible andUV, and charged particle, radiations, to display them in graphical form and to store them for future analysis. All recorded data will be made available to the public via the Internet.  相似文献   

Graphical characterisation of probability distribution tails     

K. Chaouche  P. Hubert  G. Lang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2002,16(5):342-357

 The purpose of this paper is to present a graphical method to characterise the nature of a distribution (exponential or algebraic). In the algebraic case, this statistical tool provides an estimation procedure of the parameter characterising the decrease of the survival function. The realizations of the random variable under study being available in the form of time series, this method is based on the relationship between the duration of exceeding an intensity threshold and the accumulation of the realizations of the random variable during this length of time. The behaviour of the duration-accumulation graphs (when the threshold of reference increases indefinitely) results in a function, the limit of which only depends on the parameter characterising the algebraic decrease of the probability distribution. The estimate of this parameter is biased but can be corrected effectively by numerical methods. We applied this method to two rainfall series differing by their geographical origin (Dédougou in Burkina Faso and a station on the Island of La Réunion) and their time step (respectively 1 day and 76 seconds). For both of them, the behaviour of tail distributions is shown to be algebraic and the values of the parameter characterizing the algebraic decrease of the probability distribution of the two series are very close. This would tend to justify the assumption of a multifractal nature for these series. This work was achieved as part of the National Programme of Research in Hydrology of the INSU (project 99 PNRH 27). The authors are grateful to A. Barcello for providing them the data of the Island of La Réunion Island.  相似文献   

On tail estimation: An improved method   总被引：1，自引：0，他引：1  

G. R. Dargahi-Noubary 《Mathematical Geology》1989,21(8):829-842

A step is described toward better statistical treatment of data for tail estimation. The classical extreme value theory together with its practical inefficiency for tail inference are discussed briefly. The threshold method that utilizes available information in a more efficient manner is described, and its relation to extreme value theory is mentioned. Some comparison is also made using two sets of published data.  相似文献   

An indicator kriging model for investigation of seismic hazard   总被引：2，自引：0，他引：2  

James R. Carr  Raymond E. Bailey 《Mathematical Geology》1986,18(4):409-428

Time domain probabilistic techniques most often are used for assessment of seismic hazard. Such techniques are based on the historic frequency of ground motion. Hazard is expressed as a probability of experiencing a particular level of seismic activity over a given length of time. One of these techniques utilizes frequency of extreme values for assessment of hazard. The major disadvantage of this technique, however, becomes evident when maximum seismic activity for two consecutive years occurs only a few weeks or months apart. In this case, the extreme value approach overestimates seismic hazard. A new approach for hazard assessment is founded on principles of indicator kriging. This technique evaluates seismic hazard as a simple frequency record, which is more realistic for regions of little to moderate seismicity.  相似文献   

植被微气象的数值模拟     

王信理  熊文愈 《气象学报》1995,53(2):217-224

综合考虑梯度输送和阵性穿透作用，并对植被上方的过渡层作适当处理，提出了植被微气象的一阶闭合模型。它对温、湿、风等物理量垂直分布的模拟精度良好。引用系统优化理论和方法，对模型中参数作多维非线性搜索，结果客观可靠。由于植物本身的调节适应能力和反馈作用，大气与植被间的动量与水热交换机制和过程不尽相同。在动量输送过程中，梯度产生项和阵性穿透皆不可忽视，尤其在群体下部，更为重要；而在热量和水分输送过程中，阵性穿透作用在低矮密集植被中的贡献甚微，梯度产生项起主导作用。  相似文献   

Changes of precipitation and extremes and the possible effect of urbanization in the Beijing metropolitan region during 1960–2012 based on homogenized observations     

Zhen Li  Zhongwei Yan  Kai Tu  Hongyi Wu 《大气科学进展》2015,32(9):1173-1185

Daily precipitation series at 15 stations in the Beijing metropolitan region (BMR) during 1960-2012 were homogenized using the multiple analysis of series for homogenization method, with additional adjustments based on analysis of empirical cumulative density function (ECDF) regarding climate extremes. The cumulative density functions of daily precipitation series, the trends of annual and seasonal precipitation, and summer extreme events during 1960-2012 in the original and final adjusted series at Beijing station were comparatively analyzed to show the necessity and efficiency of the new method. Results indicate that the ECDF adjustments can improve the homogeneity of high-order moments of daily series and the estimation of climate trends in extremes. The linear trends of the regional-mean annual and seasonal (spring, summer, autumn, and winter) precipitation series are -10.16, 4.97, -20.04, 5.02, and -0.11 mm (10 yr)-1, respectively. The trends over the BMR increase consistently for spring/autumn and decrease for the whole year/summer; however, the trends for winter decrease in southern parts and increase in northern parts. Urbanization affects local trends of precipitation amount, frequency, and intensity and their geographical patterns. For the urban-influenced sites, urbanization tends to slow down the magnitude of decrease in the precipitation and extreme amount series by approximately -10.4% and -6.0%, respectively; enhance the magnitude of decrease in precipitation frequency series by approximately 5.7%; reduce that of extremes by approximately -8.9%; and promote the decreasing trends in the summer intensity series of both precipitation and extremes by approximately 6.8% and 51.5%, respectively.  相似文献