Current Issue

• Impacts of Different Radiative Transfer Schemes on thePerformance of P-σ RCM9 Regional Climate Model
• HUANG An-ning;ZHANG Yao-cun
• 2009 Vol. 28 (1): 1-11. 
• Abstract ( ) PDF (7647KB) ( )
• The NCAR CCM3 radiative transfer scheme CRM (Column Radiation Model) has been introduced into P-σ RCM9regional climate model, and the difference of the climate characteristics over east Asia in winter and summer simulated by P-σ RCM9between with KQ and with CRM radiative transfer scheme has been contrastivelystudied in this paper. It is found that adopting CRM can improve the P-σ RCM9′s performance in simulating the surface temperature over China in winter and summer, and theimprovement is much more significant in summer than in winter. The improved simulations of the east Asian subtropic westerlyjet in winter and summer follow the improvement in simulating the mean meridional air temperature grads in 200~300 hPaowing to the improved caculations of the long and short wave radiative heating rates in mid\|higher tropospheres. Meanwhile, it is noted that the precipitation over China in winter and summer simulated by P-σ RCM9with CRM is closer to the observation than that in KQ experiment, CRM radiative scheme can significantly improve the P-σ RCM9′s abilityin simulating the precipitation over China in winter and summer.

• A Reference Profile Based on the Average of Initial Valueand Its Effect on the Prediction of Tibetan Plateau
• ZHANG Hong-liang;HUANG Li-ping;CHEN Jia-bin
• 2009 Vol. 28 (1): 12-19. 
• Abstract ( ) PDF (3853KB) ( )
• Usually, a reference atmosphere is used to deduce the computing error of pressure gradient in the terrain\|following dynamical equations. The reference atmosphere is static, satisfied hydrostatic balance. The real atmosphere is a perturbation from the reference atmosphere. The nearer the real atmosphereis from the reference,the smaller is the prediction error. The reference atmosphere can be isothermal atmosphereor a constant vertical temperature profile;this temperature profile can also be set as horizontal averageof the initial value. In this paper we chose the last scheme to set the reference atmosphere. In a real 3-dimensional space, the initial value of a model is sparse, distributed on severalvertical levels, so we give an analysis express of these sparse points using a cubic-spline function which is continuous and smooth in a section part. The new reference atmosphere is satisfied the hydrostatic balance in a difference formation, so the hydrostatic balance part in the equations can be removed at most. Comparing with the isothermal reference atmosphere. This scheme make the pressure gradient more accurate around the sharp terrain and can reduce the 500 hPa height prediction error.

• Study on Measurement of Urban Boundary LayerRadiation on the Meteorological Tower in Beijing
• WANG Zheng-xing;JIANG Yu-hua-;LI Ju;LIU Wei-dong;WANG Qiang
• 2009 Vol. 28 (1): 20-27. 
• Abstract ( ) PDF (2243KB) ( )
• Measurement ofradiation inboundary layer is very important for studying on interaction between air and land or sea. The change of radiation in urban boundary layer influenceson local climate and urban environment. But the meteorological radiationinstrumentscan′t satisfy the special request for studyingon the urban atmosphericboundary layer.The experimentwas conducted in Beijing from October to December 2004 , with the pyranometer and pyrgeometer installed on the 325 m meteorological tower at the heights 280 m and 2 m, respectively. For improvement of the accuracyand the agreement of the different radiation instruments on the different heights, several analysis, data corrections and carefully designed comparisonshave made and the results are fine. The calculations to eliminate the influenceof the long wave radiation emittedon radiation measurement from meteorologicaltower that have got reasonable results. Thedata analysis showsthat the variation of radiation fluxwith height in boundary layeris obvious, and the influences on boundary layer structure areimportant under different environments and conditions.

• Distribution of Source Area and Footprint of Jinta Oasis in summer
• MA Di-;Lv Shi-hua;CHEN Shi-qiang;LUO Si-qiong;QUAN Xiao-jing
• 2009 Vol. 28 (1): 28-35. 
• Abstract ( ) PDF (635KB) ( )
• The distribution of source area and footprint of Jinta oasis were analyzed by using the 3 layers′ flux data derived from the Jinta oasis experiment， which was implemented from May to July of 2005.The source area was examined by FSAM analytical model under stableand unstable conditions. Furthermore the source area was examined at different heights. It found that the source area under stable condition is larger than under unstable condition. And the higher receptor mounted, the larger source area is. The maximum footprint is futher and futher away from the tower. In addition, the surface roughness can influence the source area. In the same stability condition and height, the smaller the surface ronghness is, the larger source area is.

• Analysis on the Difference of Soil Temperature Variationbefore and after Precipitation in Gobi Region
• HAN Bo;Lv Shi-hua;AO Yin-huan
• 2009 Vol. 28 (1): 36-45. 
• Abstract ( ) PDF (6598KB) ( )
• The characteristicof soil temperature near Jinta oasis area is analyzed by using soil heat equation as well as Morlet wavelet transform during June 22 and August 18, 2004. It is found that besides diurnal variation, quasi-4 day and quasi-2 week period fluctuationsare significant during this time. Using the running correlation analysis between downward solar radiation intensity and wavelet analysis result of soil temperature, we can get the conclusion that downward solar radiation intensity is positive correlatedwith the diurnal variation power of soil temperature, which is agreed with the result of researches on annual variation of soil temperature diurnal variation amplitude. Downward solar radiation intensity is negative correlatedwith real part of quasi-4 day fluctuations at time near the precipitation. It is found that the counter radiation of cloud is attributed to the quasi-4 day fluctuations after comparing the temperature of sky with the power of quasi-4 day fluctuations. By comparing soil temperature and soil water contentdiurnal variation on two periods, before and after precipitation, it is found that after the rain, the diurnal fluctuation amplitude of both water content and temperature are strengthened, and both phases are moving forward, which can be explained as the thermal diffusivity of soil is enlarged when the soil water content is increased in a certain range. Finally, the soil temperature quasi\|2 week fluctuations is found might be related to large area atmospheric circle anomaly after using regression analysis.

• Deep Mixed Layer in Northwest China Dry Area in SummerHalf Year and Formation of the Dry Climate
• LI Yan-ying;-;QIAN Zheng-an;XUE Xin-ling;LAN Xiao-bo;LI Ling-ping
• 2009 Vol. 28 (1): 46-54. 
• Abstract ( ) PDF (2453KB) ( )
• To better understand the features of distribution and variation of the atmospheric mixed layer depth( hereafter ML) and the impact of the deep ML on the dry climate over Northwest China( NWC), in this paper, the ML thickness, its change, and the impact of it on the NWC dry climate formation have been calculated and analyzed, utilizing the observed sounding data in Zhangye and Minqin in summerand related months in more years. The main conclusions are as follows: (1) There are clear annual changes and inter-local differences for the ML thickness in Zhangye and Minqin. On the average, the ML depth is the shallowest with just less than 1 km in winter； the deepest with 3~4 km, in summer half year( especially in May and June before the local relative rainy period ). The ML depth is much higher than that in humid- and semi-humid areas in East China, and also is equivalent to or even higher than that in Qinghai-Xizang Plateau in summer. Further, the ML depth are higher in far north and west in Hexi Corridor of Gansu, where are near to the center of dry area of NWC. (2) The dry ( wet) weather has largely influence on the ML depth in arid area over NWC summer through intensifying(weakening) the exchange of sensible heat and dry convection . The statistic shows that the deepest averaged ML depth can be as high as 3413 m on the high temperature days； the next with 2838 m, on the dry days； the third with 2261 m, on the light rain ones； the shallowest with just 1942 m, on the medium-and strong-rain days. Consequently, in comparison to wet summers, the ML depth in dry summers is about 300 m highers. (3) Not only the dry and wet weather in dry area summer can considerably influence the ML depth, but also through the evaporation depletion of rain drop, the deep ML over the arid land in summer half year reduce, in turn, precipitation and intensify its dry climate. Thus, the deep ML over arid area in summer half year is one of factors of NWC drought climate formation. Some existed evidences show the conclusions above have the representative for entire NWC(even China-Mongolia) dry land for whole summer half year(May~September, not just June-August). Certainly some further investigation is still needed as well.

• Features of Climate Change of Water Vapor Resource overEastern Region of the Tibetan Plateau and Its Surroundings
• ZHOU Chang-yan;JIANG Xing-wen;LI Yue-qing;WEI Guo-cai
• 2009 Vol. 28 (1): 55-63. 
• Abstract ( ) PDF (6172KB) ( )
• Based on the monthly reanalysis data provided by the European Center for Medium-range Weather Forecasts (ECMWF), features of climate change of water vapor resource overthe eastern region of the Tibetan Plateau and its surroundingsare studied. The monthly reanalysis data provided by the National Centers for Environmental Prediction (NCEP) and radiosonde data provided by China Meteorological Administration are also used to comparativly analyzed. The main results are as follows: From 1958 to 2001, the regional average of yearly atmospheric precipitable water had been decreased in 44 years, with an average decreasing rate of 3 kg·m^-2·(10a)^-1. But it is worth noting that there is an obvious increasing trend from the late 1980s.In the four seasons, the regional averaged atmospheric precipitable water had a decline trend, the with a obvious rate of 1 kg·m^-2·(10a)^-1 in spring and summer, and 0.9 kg·m^-2·(10a)^-1 in autumn, and the decreasing rate of winter is faint. At same phase, the regional moisture budget also had a evident decreased trend in 44 years, with an average decreasing rate of 6×10⁵kg·(10a)^-1. Except for the winter, the regional moisture budgetof which had a faint increase trend in 44 years, the other three seasons′s moisture budget had been decreased. So, in a word, the water vapor resource overthe eastern region of the Tibetan Plateau and its surroundings had a decrease trend from 1958 to 2001.The weakeness of northward and westward march of the water vapor transport with summer monsoon has an important influence on the variation ofwater vapor resource in the region.In comparison with radiosonde data provided by China Meteorological Administration, it is found the results based on the ERA-40 reanalysis data are believable.

• Statistical Study on the Plateau Low Vortex Activities
• WANG Xin-;LI Yue-qing;YU Shu-hua;JIANG Xing-wen
• 2009 Vol. 28 (1): 64-71. 
• Abstract ( ) PDF (1987KB) ( )
• The activity characteristics of the Plateau Low Vortex (PLV) in summer(from May to September) are investigatedby using the daily synopticcharts of 500 hPa at 08:00 and 20:00 (BST) from 1980 to 2004. Some significant results areobtained as follows: The occurrence frequency of PLVs in summer has evident interdecadal, interannualand intraseasonal variation characteristics, and shows a decreasing tendency in the 1990s comparing with that in the 1980s. July is an active period of PLVs. The four sources of PLV forming in the Tibetan Plateau are between Shenzha and Gaize, northeastern Naqu, northeastern Dege, and Songpan. PLVs moving out of the Tibetan Plateau also have four sources: Northeastern Naqu, Qumalai, Dege and Maqin. Some PLVs can survive over 36 h in the Plateau and move eastward including three routes (northeast, southeast and east) that PLVs moving toward northeast are in the majority, but the routes out of the Plateau are different from those in the Plateau that most of PLVs are moving toward east first, then toward northeast and southeast. There are two main routes when PLVs are moving out of the Plateau, one is northeast to Hexi, Ningxia and Loess Plateau, the other is southeast to Sichuan Basin, and PLVs moving to Loess Plateauare the most. PLVs move out Plateau also has evident interannualand intraseasonal variation characteristics.Most of PLVs will weaken and vanish during 12 h after moving out of the Plateau, some can persist for 60 h, and only a few for 100 h, even 192 h. They would influence the precipitation in the vast area of east China, and maybe Korea peninsular and Japan. Warm PLVs are nearly two timesmore than baroclinic PLVs in the beginning state, while after moving out of the Plateau, the characteristics of PLVs change a lot during 12 h and most are baroclinic vortices. The occurring sources, removing routes and properties of PLVshave changed since the middle of 1980s compared with 1960s~1970s.

• Moistening Effect Analyses in Tibet in Recent Several Decades
• LUO Bu;ZHUO Ga;CHI Qu
• 2009 Vol. 28 (1): 72-76. 
• Abstract ( ) PDF (1272KB) ( )
• Based onthe observational data at six stations of Tibet from 1955 to 2000, the variation features of temperature, precipitation and water vaporin the recent several decades are analyzed.The second thermal wind helicity is also used to release the relation betweentemperature and precipitation.The resultsshow that the temperature of Tibet has a significant increasing trend in the recent several decades, especially for 1990′s and the annual average temperature rise 0.32℃ for this decade. The precipitation is also increased trend. The increase of temperature and second thermal wind helicity from 1955 to 1964leads to the increase of precipitation. Whereas the changes of temperature, precipitation and second thermal wind helicity from 1965 to 1981 are not obvious, and precipitation is actually increased when temperature and second thermal wind helicity are increased from 1982 to 2000. Furthermore, it indicates that climatic warming has induced the raiseof second thermal wind helicityand moistening rotation effect, the strength of temperature disturbance which lead to condensation of more and more water vapor, and then much water falls to the ground. At the same time, the water in surface groundis increased while the evaporation is decreased, which has caused much flood and more mountain landslidesas well as costs.

• Preliminary Study on the Character of Raindrop Spectrumand Precipitation Mechanism in Menyuan of Qinghai
• . Meteorological Research Institute of Qinghai Province;Xining;China;. Qinghai Weater Modification Offic;Xining
• 2009 Vol. 28 (1): 77-84. 
• Abstract ( ) PDF (4830KB) ( )
• Using the raindrop spectrum information at two observation stations in the Menyuan region, the changes of the average micro-structure parameters of precipitation raindrop spectrum with precipitation process and the three common types of precipitation raindrop spectrum microstructure parameters change features with time and the type of raindrop spectrum with precipitation are anlyzed. Under the micro-structure parameters and spectral type raindrop changes, combining satellite data and other data on three types of precipitation to preliminary study the precipitation mechanism for the formation.

• Characteristics of Climate Change in Qilian MountainsRegion in Recent 50 Years
• YIN Xian-zhi-;ZHANG Qiang;XU Qi-yun;XUE Wan-xiao;GUO Hui;SHI Zhi-juan
• 2009 Vol. 28 (1): 85-90. 
• Abstract ( ) PDF (1097KB) ( )
• Based on the observational air temperature and precipitation data at 5 meteorological stations in Qilian mountains region over 2800 m above sea level, the characteristic of climate change in recent 50 years are discussed. Annual mean air temperature of Qilian mountains region was on the rise during the recent 50 years, its abrupt change occured in middle of 1980s, while air temperature rose slowly before it and rapidly after it. Temperature rising rate of winter was higher than that of summer, meanwhile that of night was higher than that of daytime. And it was the highest in east and weast regions of Qilian mountains region. Simultaneously, the precipitation totally presented an increasing tendencyin Qilian mountains region. There were drought years in 1960s and 1970s. The more rain years are mostly in recent 20 years. Precipitation in spring and summer, and in west region of Qilian mountains region showed a markedincreasing tendency.

• Influence of Planetary Wave on the Seasonal Variabilityof Stratospheric Methane
• ZHENG Bin;SHI Chun-hua
• 2009 Vol. 28 (1): 91-97. 
• Abstract ( ) PDF (3369KB) ( )
• The methanemixing ratio of Halogen Occultation Experiment(HAOLE) sunrise data from 1992 to 2000 were used to analyze its seasonal variability in the stratosphere, and the National Center for Atmospheric Research(NCAR) SOCRATES (Simulation of Chemistry, Radiation, and Transport of Environmentally important Species) model is utilized to simulate the relationship of the methane seasonal variability with stratospheric planetary wave. The results indicate that there are significant seasonal variability both the observations and simulations, but the simulated variability is 30%~60% smaller than that in the observations. Otherwise, the transports by the planetary wave contribute to the methane seasonal variabilityin the model mainly below 30 km. Comparing with the CH4 transportsby planetary wave in the model and observation, the result indicates that the model underestimate the effect of the planetary wave on the CH4seasonal variability, which may be a main cause to induce a weak seasonalvariability in the model.

• Numerical study on the Water Vapor Transports of the TwoLandfalling Cyclones Affecting Hunan Province
• YE Cheng-zhi-;LI Yun-ying;LI Zu-xian
• 2009 Vol. 28 (1): 98-107. 
• Abstract ( ) PDF (6089KB) ( )
• Based on the multiple meteorological, hydrological intensify observations, and the NCEP reanalysis data, combined with the simulation and diagnosis data of meso\|scale numeric model of AREM, the water vapor features of two unique cyclone, the typhoon Bilis and Sepat which inducing heavy rainfall in the Hunan province are analyzed and some comparisons are conducted. The results show that, both of cyclones have two main water vapor channels, one is from south linkingwith the west\|south monsoon, and the other is from north linkingwith the cyclone′s low\|pressure circulation. In addition, their rain water mainly originates from the convergence of the lower levels, and is transported to the middle and high levels by local ascending airflows. However, it is noted that the water vapor flux in the Sepat′s heavy rain areas has stronger intensity than that of Bilis. Although with the weaker convergence of the water vapor flux and thinner convergent depth, Sepat′s lifetime is longer, total rainfall is larger and coveringarea is broader, since it has relatively stronger inner strength, and the steady wind shear in the south part of the cyclone′s center. On the otherhand, the main water vapor path of Bilis is much more southerly,the moisture convergence andthe interaction of the South China Sea monsoonarestronger than those of Sepat′s, its rain intensity in some areas and in certain periods is much more stronger.

• Analysis and Simulation of Relation of the Weakening Trend ofLand-Sea Difference of Springtime Mean Surface Air Temperaturein South China and Its Ambient Ocean and Intensityof East Asian Summer Monsoon
• SHI Xiao-hui;XU Xiang-de
• 2009 Vol. 28 (1): 108-114. 
• Abstract ( ) PDF (4677KB) ( )
• Using NCEP/NCAR reanalysis data, the linear change rate (LCR) of springtimemean surface air temperature (SAT) is calculated. It is found that the negative LCR is dominant in South China, but the positiveLCR is mainly located on the ocean, i.e., there exists a weakening trend of land-sea difference of springtime mean SAT in South China and its ambient ocean. The composed analysis result shows that this weakening land-sea difference of SAT is correlated with the weakened trend of summertime southerly in East Asia. According to the diagnostic result, ICTP RegCM3 is adopted to have a sensitivity numerical experiment with changed SATs in South China and its adjacent ocean (CST). The aim is to further investigate the impacts of the weakening trend of land-sea difference of the springtime mean SAT on the intensity of East Asian summer monsoon. Comparing with the control experiment (CTL), the monthly wind field at 850 hPa in summer of CST shows an obvious feature with decreasing southerly in eastern China (the difference of CST-CTL is northerly). It also can be found that a cycle circulation locates over the eastern China and its neighboringocean from the difference field of wind at 850 hPa, which is maybe related with the variations of the West Pacific Subtropical High in CST. Furthermore, the “increasing in Southern and decreasing in Northern China”change of summertime precipitation in the eastern China could be simulated in CST. Summing up the above results, the weakening trendof land-sea difference of springtime meanSAT in South China and its adjacent ocean have certain influences on the intensity of East Asian summer monsoon.

• Numerical Study for the Influences of Orographic Dynamicon Cloud and Precipitation in North China
• LIAO Fei-;HU Ya-min;HONG Yan-chao
• 2009 Vol. 28 (1): 115-126. 
• Abstract ( ) PDF (6737KB) ( )
• Orographic dynamical effects on cloud and precipitation arediscussed through the numerical experimentsof a North China rainstorm case on 22~24 July 2005 by using Advanced Regional Prediction System (ARPS) model. The researched results show that the distribution and size of horizontal and vertical wind will obviously change due to terrain height variety. Increase of terrain height is favorable to the development of horizontal wind divergence and upward convection, especially the development of mid\|high cloud. Owing to cloud water enhancement in mid\|high level, distributing area of surface precipitation extends and total rainfall increases. The reason of such change is mainly due to the augmentation of supercooledcloud water content, which is suitable to the growing of snow and graupel. Although increasing terrain height will weaken warm cloud process during the forepart time of cloud development, cold cloud process will be intensified continuouslyduring the whole rain process. So, cold cloud process is still the main precipitation mechanism. As a result, increase of ice particle melting will lead to accretionof rain water, and accelerate the development of cloud and precipitation.

• Observation and Study of Wind Velocity Variationwith Altitude over the EXPO Land, Shanghai
• XIN Tiao-er;HE Qian-shan;WEI Hai-ru;LIU Dong-wei;ZHOU Guang-qiang;Yang He-qun;SHAO De-min
• 2009 Vol. 28 (1): 127-135. 
• Abstract ( ) PDF (3425KB) ( )
• The wind velocity variations with height are observed over the EXPO Land, Shanghai using the flat arrayacoustic wind profiler from July 17 to September 28, 2007. This study shows the westerly domination in nighttime and easterly domination with low velocity variation at daytime by analyzing the diurnal variations of the local circulations, indicating sea-land wind significantly influences on the circulation in low atmospheric boundary layer. The day-to-day variations of wind velocity with height are characterized by north-westerly dominationbefore August 2 and transiting to south-easterly from then on. The day-to-day variations of vertical wind velocity are dominated by updraft at most of days and the increased wind velocity connected withnorth-westerly. Nighttime averaged wind profile characterized by higher wind velocity and increasing with height is obvious different from that of daytime, which is almost constant with altitude below 270 m, except that daytime averaged wind velocity is higher than that of nighttime below 90 m and the steady northerly over urban canopy layer throughout the whole day. The wind speed of the city is lower than that of the suburb due to inhomogeneous underlying surface of city, and the difference of wind speed between the city and the suburb begins to decrease with the elevation with correlation coefficient of 87% at 330 m.

• The Quality Evaluation of Solar Radiation Data Measuredin Shangdianzi Background Station
• QUAN Wei-jun;CHEN Hong-bin;GAO Yan-hu;GUO Wen-li;LIU Yong-hong
• 2009 Vol. 28 (1): 136-142. 
• Abstract ( ) PDF (2635KB) ( )
• The method introduced by Baseline Surface Radiation Network (BSRN)is presented to evaluatethe quality of solar radiation data measured in Shangdianzi background station in 2005. The Root Mean Squared Error(RMSE)and the coefficient of variation(Cv)between the measured and calculated surface global solar radiation data under cloudless sky conditionsare analyzed and substitute for the step of “eye check of time series plots” used by BSRN. The results indicate that more than 95% of the direct, scattering and total solar radiation data pass through the first 3 step checks on all months in 2005 except for the July and August. Similarly, 74.7% to 85.8% of up-wellingsolar radiation data measured in March, April, July and August pass through the 3 step checks, and more than 91% on other months. At the same time, The RMSEs on all months are less than 23.5 W·m-2, and the Cv are less than 0.05 on all months, except for November andDecember.

• Study on Distributed Simulation of Diffuse Solar Radiationover Complex Terrains Based on DEM——Taking Guizhou Plateau for Example
• GU Xiao-ping;YUAN Shu-jie;SHI Lan;KANG Wei-min;MIAO Qi-long;QIU Xin-fa
• 2009 Vol. 28 (1): 143-150. 
• Abstract ( ) PDF (3157KB) ( )
• The diffuse solar radiation (DSR) is the elements of global solar radiation. Due to the influence of local terrain factors such as slope, aspect and terrain inter-shielding, it is very difficult to calculate DSR over complex terrains(CT). The previous models have been improved in this paper on the basis of past studies. The influence of slope, aspect, and terrain inter-shieldingon astronomical solar radiation over CTis considered, a distributed model, whichis based on astronomical solar radiation over CTanddiffuse radiation′s anisotropism,for calculating DSR quantities over CT is developed. Using this model, the elaborate distribution of DSR with resolution of 100 m×100 m bya DEM and meteorological observation data in the Guizhou Plateau are generated. The results are as follows: (1) The influence of local terrain factors as the slope, aspect and terrain inter-shielding on DSRis great, so that DSR′s elaborate spatial distribution has obvious terrain distributing feature over CT in Guizhou Plateau. The spatial distribution of DSR is obvious dissimilarity with hypsography, and the zonal distributing character is not evident. (2)For DSR,the effect of topographical factorsshould not be disregarded.

• Chemical Composition of Water-Soluble Ions in Aerosolsover Xi′an in Heating and Non-Heating Seasons
• SHEN Zhen-xing-;HUO Zong-quan;HAN Yue-mei;CAO Jun-ji;ZHANG Ting
• 2009 Vol. 28 (1): 151-158. 
• Abstract ( ) PDF (3911KB) ( )
• TSP and PM2.5samples were collected over Xi′an in winter (heating season) and summer (non heating season) to characterize the seasonal variations of water-soluble inorganic ions and to evaluate the effectiveness of the pollution controls during the past ten years. Mass concentrations of the water-soluble ions (Na+, NH+4, K+, Mg2+, Ca2+, F-, Cl-, Br-, NO-2, NO-3, and SO2-4) were measured for the total of 104 samples. The average concentration of the total 11 ions in PM2.5and TSP were 53.2 and110.3 g·m-3 in heating seasons, while they were 51.3and89.3 g m-3in non-heating seasons, respectively. SO2-4, NO-3,and NH+4were the majorions both in PM2.5and TSP; they occupied 78% and 76% of the total ions in PM2.5and TSP in heating seasons, and 88% and 76% in non-heating seasons. These three ions were mainly in the form of (NH4)2SO4, NH4HSO4and NH4NO3in aerosol particles. The sulfuroxidation ratio (SOR)and nitrogen oxidation ratio (NOR)in non heating season were higher than those in heating season, indicating SO2-4and NO-3were largely from the process of gas-phase photochemical reaction, and mainly influenced by ambient temperature. The ions balance between total cations and total anions and pH measurement showed that the airborne PM2.5at Xi′an was just a little acid, while TSP was a little alkaline. The heating season samples were more acid than the summer aerosol samples. Comparison with the data from ten years ago showed that the concentrationsof major three ions (SO2-4, NO-3and NH+4 ) decreased significantly,indicating that pollution controls in Xi′an were effective during the past ten years.On the other side, the emission of mobile source was prevailed to coal combustionand should be paid more attention in the near future.

• Simulation of the Deposition of Hg Emitted from CoalConsumption in China by CMAQ-Hg Model
• QUAN Jian-nong-;ZHANG Xiao-shan;ZHANG Qiang;LI Hong-yu
• 2009 Vol. 28 (1): 159-164. 
• Abstract ( ) PDF (1874KB) ( )
• Mercury (Hg) emission from coal combustion in China isestimated in this study and its deposition calculated using the Models-3 Community Multi-scale Air Quality (CMAQ-Hg) modeling system with meteorological fields calculated by MM5.Threekinds of Hg speciationwere included in the models: Particle-bound mercury (PHg), gaseous elemental mercury (GEM) and gas oxidized mercury (RGM). Much of the Hg was released as RGM from coal combustionin China, accounting for 58.4%~66.8% of total emissions. The large proportion of RGM in overall Hg emissionalso ledto large Hg deposition. Based on simulations, Hg deposition originatingfrom coal combustion reaches as high as 2~6 μg·m-2·mon-1 insouthwestern China (particularly Guizhou Province), the industrialized and populated regions of east central and coastal China, and Liaoning Provincein the northeast.

• The Impact of Gravity Wave on a Hailstorm Weather Process Evolution
• SUN Ji-song-;WANG Hua
• 2009 Vol. 28 (1): 165-172. 
• Abstract ( ) PDF (6127KB) ( )
• Using the auto-weather station networkwith high spatial-temporal resolution,radar and wind profiler datasets, some of micro-and meso-scale features of severe convective multi-hail storms that occurredin Beijingarea on 31 May 2005 have been investigated, and the preliminaryrelationship among ambientmeteorological elements and evolutions of hailstorm including their initiation, development and regeneration has been revealed, andemphatically,the effect of gravity wave on the interaction between hailstorm or hailstorm cluster has been analyzed. The results indicate： (1) when atmospheric circulationispropitious tosevere convective activities, gravity wave forced by topography or severe hail storm not only activate new storm cell, but also produce direct effect on the motion, development, booming or fading of storm cell; (2) evolutions of multi-storm cells are significantly influenced by complicated interaction among the meso-scale gravity waves stirred by different forcing resources (such as topography, severe hailstorm), different amplitudes, wavelengths and periodic variations, and it is beneficial to generation of hailstorm cluster.

• Assimilation of Microphysical Adjustments Using Reflectivityof CINRAD/CD Doppler Radar For Meso-Scale Model
• WANG Jin-;LIU Li-ping
• 2009 Vol. 28 (1): 173-185. 
• Abstract ( ) PDF (16076KB) ( )
• For the purpose of researching the impact of assimilation of microphysical adjustments using reflectivity of Doppler radar, ARPS model ,ARPS3DVAR and a complex cloud analysis procedure were used to assimilate CINRAD/CD Doppler radar data of a severe storm weather case which occurred in Northern Guizhou province(locate in south-west of china).The assimilation and predictions used a 3 km grid nested inside a 15 km one. There were three numerical experiments with different settings for retrieving cloud hydrometeors using Doppler radar reflectivity in our studying. Results showed that the two experiments with complex cloud analysis procedure can analyze a suitable distribution of cloud water and hydrometeors, and the distribution of potential temperature and vertical velocity responded to the adjustment of hydrometeors perfectly. As compared with the EXPR_NOREF experiment without complex cloud analysis, the CNTL-SMITH-REFONLY experiment which used the complex cloud analysis had analyzed a suitable field of cloud water and hydrometeors in model′s initial time, captured the major features of convective storm, so duration of spin up time had been remarkably decreased and the major structure and features of the storm in initial time and over 1 h forecasting time can be suitably simulated, but the experiment without cloud analysis must cost 2 or 3 hours to analyze a field of hydrometeors which has error position. The assimilation of reflectivity of Doppler radar had acted as key role in the simulation of severe convective storm.

• Analayese on CG Lightning Characteristics in Hailstorm processin Center-South Parts of Hebei Caused East Mongolia Cold Vortex
• LIAN Zhi-luan;GAO Lian-shan;LI Guo-cui;ZHAO Rui-jin;ZHAO Yan-chang
• 2009 Vol. 28 (1): 186-194. 
• Abstract ( ) PDF (4722KB) ( )
• Using the data from Lightning Detection Network, Doppler radar and intensified Automatic Surface Observation System, the temporal and spatial distributions of CG lightning is investigated for two hailstorms under cold vortex over East Mongolia synoptic situation on 8~9 July 2007. The results show that a great deal of CG lightning produced and negative CG lightning predominated during the two hailstorms. The periods of time that CG lightning were intensively occurred to were equivalent to the severe convective holding time. CG lightning pole feature in hailstorm was obvious difference from convectional rainstorm. Shooting hail took place in the most of active stage of positive CG lightning. The positive CG lightning clustered in the region with maximum intense echo. Point of falling hailstone was at the nearby of positive CG flashes compact area. Negative flash rate was high in convectional heavy precipitation cloud. Severe rainfall occurred nearby high density center of the negative flash. In multi-cell storm, rate and cluster area of CG lightning depend on the number, strength and closeness of cells. Severe shooting hail caused by multi-cell storm happened at the stage with active CG lightning . In the case, the peak of CG flash rate and the sudden enhancement of positive flash rate is only a few minutes prior to the hail events (nearly same time), so flash rate could be used to monitor the development and evolution of convective and hail events.

• Statistical Estimation of Artificial Precipitation EnhancementEffectiveness in Beijing in 2006
• WANG Wan-;YAO Zhan-yu
• 2009 Vol. 28 (1): 195-202. 
• Abstract ( ) PDF (2554KB) ( )
• By setting the daily rainfall volume as the statistical variable,the Historical Regression Method is used in this study for estimation of precipitation enhancement effectiveness in Beijing in 2006. There are 43 operating days in Beijing in 2006 and 41 days of them are artificial precipitation enhancementdays. The target area liesthe northern part ofBeijing and the area is 100 km×50 km. The objective evaluation results are obtained showing thattherelative increase of precipitation is 13%, and total absolute artificial precipitation enhancement is 39 mm, but the result is not significant. The operating days are divided into different categories and the artificial precipitation enhancement effectivenessof these different categories are estimated and the resultshaveindicated that the effectiveness of artificial precipitation enhancementin ground sufficientcatalytic operational days（21） is 34% at significanceof 0.019 by u\|test, in ground and airplane sufficientcatalytic operational days（29） is 37% at significanceof 0.022 by u\|test, in airplane operational days（8） is 48% at low significance, in ground insufficientcatalytic operational days（12） is -49% and in precipitation reducing days（2） is -12% at low significance. Then it comes to a conclusion that it is needed abundant catalyticif we want to get a good result of precipitation enhancement.

• Diagnosis Analysis on a Thunderstorm Eventin the East of Northwest China
• GONG Min-ying;JIN Ying-yan
• 2009 Vol. 28 (1): 203-208. 
• Abstract ( ) PDF (3361KB) ( )
• The diagnosis analysis for a case thunderstorm occurredon 14 August 2006 was studied utilizing the observed data in this paper. The main results were as follows: (1) The thunderstormevent has closely relationship with the trough at 500 hPa and the withdrawingof the western Pacific subtropical high. At the same time, the saddle pattern of wind field at low level of troposphere favored the occurrence and development of thunderstorm. (2) The existence and persistenceof dry and warm lids were in favor ofaccumulation of energy on contrast it could restrainvertical transport of moisture， and the existence of instability stratification provided the important mechanism for this case. (3) The development of strong PV center was close with this event, and the strong divergence on high level and convergence on low level were the important dynamicmechanism for the thunderstorm; (4) To analyze the temperature, pressure, moisture and wind characteristics in vertical stratification, to reference evolution of weather at upstream sites, and to observethe speed, direction and change in the intensity of thunderstorm convective system via echo on the screen of radar are valid means in recent forcast.

• k-Nearest Neighbor Method and Its Application toTongchuan Hail Prediction
• AN Dong-wei-;YANG Yan;SUN Tian-wen;ZHAO Guo-ling;LI Ming
• 2009 Vol. 28 (1): 209-213. 
• Abstract ( ) PDF (939KB) ( )
• Limitations of traditional statistic methods used in weather predicting are analyzed. And the basic theory of k-Nearest Neighbor (kNN) is briefly introduced. Seven factors from high altitude are picked up according to the physic mechanism of hail′s generation. Based on the 248 intact examples of 8 consecutive years, kNN is used to predict hail in Tongchuan in May. Experiment shows kNN′s better performance(the best TS reaches to 0.444). The data in 2005 and 2006 are picked up to do further experiment using the preferred model. Its TS is superior to that of SVM, ANN and the traditional methods which are used by many forecasters. At last, the experiments' results are analyzed, and the applications of kNN in weather broadcasting are further analyzed.

• Climatic Characteristic and Change of Rain Dayfor Different Intensities in Yunnan
• PENG Gui-feng;LIU Yu
• 2009 Vol. 28 (1): 214-219. 
• Abstract ( ) PDF (2072KB) ( )
• Using the data of 125 weather stations in Yunnan Province form 1959 to 2005, and the modern statistic diagnosablemethod of counting the trend-coefficient, the rain-day, moderaterain-day, heavy-day, rainstorm-day, heavy rainstorm-day and climatic characteristic and change each magnitude precipitation in Yunnan Province are researched. The results indicate that, there is an obvious difference between dry and rainy seasons from moderate to heavy rainfall in Yunnan Province. In the rainy season, the moderate rain-day, heavy rain-day, rainstorm-day and heavy rainstorm-day accounts for 84%, 90%, 94%, 99%, respectively of the whole year.In particular, the heavy rain-day of June, July, and August take up more than 61% of the whole year. There is a high concentration for the severe rain-day, but the larger the rainfall magnitude, the higher the concentration.The heavy rain-day, rainstorm-day, heavy rainstorm-day are increasing. Furthermore, the increasing trend of the heavy rainstorm-day is the most remarkable, more than that of rainstorm-day and the heavy rain-day. Meanwhile the rain-day and the moderaterain-day are decreasing, and the decreasing trend of rain-day is quite obvious. On average of 10 years, the heavy rain-day increased by 6.9 days, the rainstorm-day increased by 4.3 days, and the heavy rainstorm-day increased by 0.7 days, while the moderaterain-day decreased by 75.4 days, and the average rain-day decreased for 7.6 days. There is a reductive trend on the annual precipitation of Yunnan Province, but it is not remarkable, which decreased by 15.3 mm per year. Meanwhile, The precipitation of heavy rain, rainstorm and heavy rainstorm increased slightly, but not remarkable also. Instead, that of light rain and moderaterain decreased remarkable.

• Spatial and Temporal Distributions and Climatic Changeof Summer Precipitation in Shandong Province
• CHI Zhu-ping-
• 2009 Vol. 28 (1): 220-226. 
• Abstract ( ) PDF (4277KB) ( )
• The spatialand temporal distributions of summer (June~August ) precipitation and rainy days and rainstorm days using the daily precipitation data at 26 stations in Shandong province in 1961-2005 are analyzed. The climatic variationcauseof precipitationis studied, and then dry/wet summer is determined. The resultsshow that the trend of summer rainfallis decreasing, the relation is better betweenthe variation of average quantity of daily rainstormand the rainfall decrease. The climatic change features occurred abruptly around 1981, and the circulation background are studiedusing the 500 hPa geopotential height data and circulation eigenvalue.

• The Review of Hygroscopic Seeding
• SU Zheng-jun-;ZHENG Guo-guang;FENG Da-xiong
• 2009 Vol. 28 (1): 227-232. 
• Abstract ( ) PDF (861KB) ( )
• The review is begun with a brief summary of the history of hygroscopic seeding and the current status of our understandings of the physics of precipitation in warm clouds. Seeding convective type of clouds with hygroscopic particles produced by flares have received a lot of attention in the past decade, several field projects around the world are actively exploring the possibility of enhancing rainfall using this technique. This renewed interest in cloud seeding and the increasing number of field projects, has led to the development of new and improved hygroscopic flares. There are some exciting new results of hygroscopic seeding with flares. Especially， the recently hygroscopic seedingexperiments in South Africa, Thailand and Mexico made the enthusiasm for the potential of hygroscopic seeding grown. The hygroscopic seeding hypothesis is not yet scientifically proven because it cannot explain the statistically significant increases in precipitation that wasobserved in recent experiments. Finally, the overview is concluded with specific recommendations regarding the current status of warm cloud modification, and futuredirections for the scientist and weather modification practitioner in China.