Current Issue

• A Study of Diagnosis and Numerical Simulation Test on the Onset of SCSM in May of 1998
• SONG Zheng-shan;PENG Jing-bei;ZHANG Dao-min;ZHANG Qing-yun
• 2006 Vol. 25 (4): 557-566. 
• Abstract ( ) PDF (1401KB) ( )
• The summer monsoon over South China Sea(SCSM) is abrupt settled around 22 May,1998.Utilizing the NCEP/NCAR grid point and TBB data,the middle range process of SCSM onset has been diagnostically studied by heat source,moisture sink as well as a simplified quasi-geostrophic potential vorticity equation.By means of the simulation tests of middle range numerical model,the physical mechanism of SCSM onset has been examined further.It has been found that the development of a tropical cyclone over Bay of Bengal and the activity of cold air over south China,South China Sea and western Pacific both play an important role for the onset of SCSM.The release of latent heat associated with them is the most important factor for the intensity of southwesterlies(easterlies) at 850(200 hPa) over South Asia and the movement of anticyclone system to 22°N at 200 hPa over Indo-China peninsula.The onset of SCSM could be considered as a phenomenon to response the variation of those heat sources.The sensible heating over Qinghai-Xizang Plateau could enlarge the convergence(divergence) in low(high) level leading to the intensity of SCSM,but the influence is not so obvious as that by above latent heating.The Qinghai-Xizang Plateau displays the dynamic block effect forcing the wave trough of westerlies to weaken and move slow down,which is favorable to the shift northward of 200 hPa anticyclone,but without significant influences on the circulation in low latitudes.

• The Application of CoLM to Arid Region of Northwest China and Qinghai-Xizang Plateau
• XIN Yu-fei;BIAN Lin-gen;ZHANG Xue-hong
• 2006 Vol. 25 (4): 567-574. 
• Abstract ( ) PDF (1916KB) ( )
• A off-line validation experimentis done with common land model(CoLM) at Zhangye station of typical arid region in Northwest China and Anduo and MS3478 stations of Qinghai-Xizang Plateau.The result show that the numerical simulation of land surface process of typical arid region is better by the CoLM.The daily and seasonally changes of vertical profile of soil temperature is exactly simulated,in detail,the correlation coefficient between simulation and observationof ground surface temperature is 0.885.The standard error is 0.873,the correlation coefficient between simulation and observation of the soil temperature at 5 cm depths is 0.944,the standard error is 0.891.The simulations of net solar radiation and sense heat flux over Qinghai-Xizang Plateau are better,but the simulated value of latent heat flux is higher,actually,during GAME-Tibet monsoon experiment,the energy imbalance problem has been existed.So,it is not for sure to say that the model's simulation is not good.

• Numerical Simulation of Effect of Vegetation Changes of Loess Plateau on Environment
• LIANG Ling;Lü Shi-hua;LIU Yuan-pu
• 2006 Vol. 25 (4): 575-582. 
• Abstract ( ) PDF (1244KB) ( )
• To show the impact of vegetation changes over Loess Plateau on the environment three experiments with the real,the improved and the degradation vegetation over the Loess Plateau respectively,have been desighed and run,using the new nonhy drostatic atmospheric mesoscale model MM5 of National Center of Atmospheric Research(NCAR),a precipitation process of Loess Plateau from 26 to 30 June in 2003 is simulated.The impact of vegetation changes over loess Plateau on precipitation with a control experiment and two sensitivity numerical experiments.The results show that the improved vegetation can increase precipitation moisture,reduce runoff and diural change of air temperature,but vice versa for the degradation vegetation.The test comprehensively reveals the physical mechanism of the interaction between land surface and temperature,humidity in atmospheric boundary layer of heterogeneous ground surface.

• The Interannual and Interdecadal Variation of Arctic Polar Vortex at 300 hPa
• ZHANG Heng-de;GAO Shou-ting;ZHANG You-shu
• 2006 Vol. 25 (4): 583-592. 
• Abstract ( ) PDF (671KB) ( )
• The area size and intensity of 300 hPa Arctic polar vortex and their seasonal changes are estimated from 1949 to 2002 based upon the 54-year NCEP/NCAR reanalysis monthly mean geopotential height data.By means of linear trend estimate,Morlet wavelet analysis and binomial coefficient smooth,the interannual and interdecadal variation characteristics of 300 hPa Arctic Polar vortex are studied,including the variation of area,intensity and location.The results show that:(1) Before middle age of 1970s,annual area size of Arctic polar vortex trend to rise,with small fluctuating,and after that,with clear undulating,it trend to decrease,but the size has a linear decline trend during 1949-2002.The linear variation trends of regionⅠandⅡ are much smaller than that of region Ⅳ.The interannual variation in summer is the most obvious,and the variation in autumn is the smallest.The area of seasonal Arctic polar vortex also trend to contract linearly,especially in winter.(2) Intensity of annual polar vortex has the similar characteristics of the interannual and interdecadal variations with area,but the linear trend is very slight.Each region resemble Northern Hemisphere about the variation of intensity,especially regionⅠ,except for local difference in some period of time.The interannual variation in summer has the largest extent,and inter-decadal variationin spring and summer is much more prominentthan in autumn.(3) The center of northern polar vortex is not at Arctic pole.The percentage of the polar vortex size in each quadrant hasdistinct difference,and it varies from January to December,which is close related to thermodynamic difference over sea-land.The main location of polar vortex has interannual and interdecadal variation characteristics.The percentage of the vortex size in quadrantⅠ and Ⅱ trend to ascend,while descend in quadrant Ⅲ and Ⅳ,and the linear trend coefficient is small for quadrantⅠand Ⅲ.The center of polar vortex mainly displace towards Asia land and the Pacific.

• The Theory and Numerical Calculation of Mountain Gravity Waves Generated by Flow over Hill
• LI Zi-liang
• 2006 Vol. 25 (4): 593-600. 
• Abstract ( ) PDF (1065KB) ( )
• The theory and numerical calculation of mountain gravity waves and atmospheric ship waves generated by three-dimensional multi-layer flow over isolated hill are investigated.Using the three-dimensional multi-layer linear theory model to calculate the lee wave fields,the characteristics of atmospheric ship waves of trapped and diverging modes are obtained where the three-dimensional multi-layer flow over isolated mountain under the various stability conditions.

• Characteristic Time Scales of Interannual Change of South Asia High in Summer and Its Tempora-l Spatial Evolution
• YOU Wei-hong;DUAN Chang-chun;ZHAO Ning-kun;MA Zhen-feng
• 2006 Vol. 25 (4): 601-608. 
• Abstract ( ) PDF (1724KB) ( )
• Using the temporal wavelet transform method of three-dimensional data, the characteristic time scale and temporal-spatial changes of the interannual variability of South Asia High in summer are investigated.The results show that there are 2, 5, 10 years and maximum characteristic time scales for the interannual change of South A sia High in summer.The maximum amplitude energy regions corresponding to 2, 5 and 10 year characteristic time scales are main to the south of 20°N, the south of 35°N and between the 15°N, 35°Nrespectively.The maximum amplitude energy centers of 5, 10 year characteristic time scales are located at 32.5°N, 92.5°E and 27.5°N, 110°E.The geopotential height longitudinal evolutions of the maximum central latitude in association with 5 year characteristic time scale obviously appear longitudinal oscillations.The geopotential height longitudinal evolutions of the maximum central latitude in association with 10 year characteristic time scales have a tendency to move towards the east.The geopotential height lat itudinal evolutions of the maximum central longitudes in association with 5, 10 year characteristic time scales all have obvious the tendency to move towards the north.

• Distribution Features and Seasonal Variations of Stratospheric CH₄ over China
• ZHENG Bin;SHI Chun-hua;CHEN Yue-Juan
• 2006 Vol. 25 (4): 609-615. 
• Abstract ( ) PDF (686KB) ( )
• CH₄ data throughout 1992 to 2003 from HALOE experiment on UARS are used to analyze the features of distribution and seasonal variations of stratospheric CH₄ mixing ratio over China.The results show that the stratospheric CH₄ mixing ratio over China decrease with height,and there are more larger meridional differences than zonal differences and highter CH₄ concentration to the south than that to the north.Usually,CH₄ concentration varies a little with longitudes.Moreover,the seasonal departures of stratospheric CH₄ mixing ratio over china are reverse signs between DJF and MAM,and their centers are in most agreement.There are the largest seasonal variability between MAM and DJF.Other that,there are high value region of CH₄ mixing ratio during summer at lower stratosphere,and most probably,upward motion and divergence play important role on the high CH₄ concentration in half-summer.

• Relationship between Activity of West Pacific Subtropical High and Condensation Latent Heating in Summer of 1998
• WEN Min;SHI Xiao-hui
• 2006 Vol. 25 (4): 616-623. 
• Abstract ( ) PDF (1437KB) ( )
• By means of daily reanalysis data of the South China Sea Monsoon Experiment in 1998,the influence of condensation latent heating on mid- and short-term activities of West Pacific Subtropical High(WPSH) during Meiyu period 1998 is studied.Results show that the location of condensation latent heating has some impact on WSPH.The condensation latent heating released by rainfall on the west side of WSPH may force an eastward withdrawal of WPSH,while the rainfall is to far west of WPSH will lead to a westward extension of WPSH.The latent heating to the north of WPSH prevents the WSPH from moving northward and vice versa for that to the south of WPSH.When the heating to both the south and north of WPSH has the equal intensity,the WPSH is immovable,but it will intensity and extendes westward when it is strong enough.If the intensity of heating on one side weakens,WPSH moves toward that side.

• Temporal and Spatial Feature Analyses of Winter and Summer Surface Air Temperature over CMASA,Part(Ⅱ): July
• LI Wan-yuan;QIAN Zheng-an;SONG Min-hong;Lü Shi-hua;SHEN Zhi-bao
• 2006 Vol. 25 (4): 624-632. 
• Abstract ( ) PDF (1341KB) ( )
• To analyze the temporal and spatial change features of the surface air temperature over China-Mongolia Arid and Semi-arid Area(CMASA) as a whole,the July mean air temperature field and their annual- and diurnal-ranges have first been analyzed,and the Empirical Orthogonal Function(EOF) and Rotated EOF(REOF) analysis technique have then been conducted utilizing the observed July surface air temperature data from the 104 even-distributed stations selected over the CMASA during the period of 1961-1997.The main results are as follows:(1) There are full of heat climate source over the CMASA in summer.The regional feature of the mean temperature is more clearer in summer than that in winter.(2) Because of the impact of the latitude,terrain height and inland,the summer temperature variation over CMASA show both the large annual- and diurnal-ranges,it is characterized by the typical continental climate,ie the highly continentality and but with the small year to year variation.(3) According to the EOF analyses,the summer temperature anomaly distribution over CMASA were divided into four main modes as the first proximity: with the same temperature anomaly in the entire area,with the different ones in the east and west,in the south and north,and also in the northeast and southwest;and again according to the REOF analyses,the summer temperature anomaly patterns were,in some more detail,divided into seven subregions further: Qinghai Plateau Region,Oneon the northeast side of the Qinghai-Xizang Plateau,Southern- and Northern-Xinjiang,Shaanxi and Southern Gansu,Northwestern- and Southeastern-Mongolia.(4) In the past 37 years,the summer warming of CMASA occurs mainly in the Region on the northeast side of Qinghai-Xizang Plateau and the Southern Xinjiang.The warming over CMASA in summer is less than that in winter and spring.Also the summer temperature changes have the period of three to four years.

• Climate Variation of Southwest China in Recent 40 Years
• MA Zhen-feng;PENG Jun;GAO Wen-liang;Tian Hong
• 2006 Vol. 25 (4): 633-642. 
• Abstract ( ) PDF (1675KB) ( )
• Using the annual mean surface observational data(1961-2000) at 139 stations in SW(Yunnan,Guizhou,Chongqing,Sichuan and Tibet),the character on interannual and interdecadal changes of climate is analyzed,thus revealed the distinct tendency of temperature rising,precipitation and relative humidity increasing over the Tibetan Plateau,western Sichuan highland and Yun-Gui Tableland at this period.However there is apparently decreasing trend of temperature in the Northeast and Southwest Sichuan Basin.Evidently,the climate change in the southwest area does not synchronize with global warming.Through analyzing the interannual and interdecadal changes of meteorological elements,we obtained the result that, basically,these elements all have the obvious oscillations on the interannual and interdecadal changes.And then these element's catastrophes are tested,the results indicate that the temperature catastrophe take place in the Tibetan Plateau first,and then Yun-Gui Tableland,last,Sichuan Basin and the hilly land of eastern Guizhou.Other elements start catastrophe generally from the Tibetan Plateau as well.Therefore,most of the factors in this region begin abruptness earlier in higher elevation than in lower.And global abrupt change of temperature occurs earlier than that of this region.

• Analyses on Surface Air Temperature Changes in East Part of Northwest China in Last 40 Years
• ZHAO Qing-yun;LI Dong-liang;WU Hong-bao
• 2006 Vol. 25 (4): 643-650. 
• Abstract ( ) PDF (1872KB) ( )
• The surface yearly mean air temperture and yearly extreme air temperature have been analyzed by the area weighted method and 100 meteorological observation stations of air temperature data in the east part of the Northwest China(ENWC) in 1960-2002.The result shows that the climate of the ENWC has became more extreme in years of ten,which appear consistent increasing trend,but it has turned from 1986 to 1987,namely,the climatic mean value is from low to high.The area of abnormal low temperature is clominant position before 1986,while the abnormal high area of minimum temperature hardly present after 1987.The temperature increasing in the late of 1990's is significant,the temperature difference decreases,the area of abnormal high temperature obvoiusly extend,particularly,the abnormal high areas of maximum temperature extend over 50% in the ENWC from 1997 to 2002.The variabilily between mean temperature and extreme air temperature is not all the same,the increasing trend of minimum temperature is more obvoius than mean temperature and maximum temperature.The comparative analysis shows that the statistical method of area weighed mean reveals the intensity and effect region of climatic anomaly to get the best of simple site mean.

• An Attempt in Improving Numerical Simulation of Severe Precipitation Via the Physical Dissipative Technique
• LIU Ying;LIU Chong-jian;XU Hui;ZHAO Yong-ming
• 2006 Vol. 25 (4): 651-657. 
• Abstract ( ) PDF (1182KB) ( )
• The numerical comparative experimentson sensibility of the physical dissipative technique to precipitation parameterizations,esp.to the different combinations of the explicit micro-physical schemes and cumulous convection parameterizations,in the PSU/NCAR meso-scale model MM5V3 with a triple-nested domain is conducted using the case of heavy rain occurredin the North China in October 2003.The experiments reveal some meaningful results,notably the dramatic improvement in the simulative accuracyand quality by thephysical dissipative technique based on the second law of thermodynamics resulting from modifying the direction of horizontal diffusion in the model into the correct one.On the other hand,the weak sensibility of the physical dissipative technique to the schemes of parameterization,as shown by the comparative experiments,is mainly because improving the field of rainfall by the physical dissipative technique is reached via improving the outputs of the model variables such as wind field determining the divergence field that is one of the most important factors when designing the schemes of precipitation parameterization.

• Relationship between the Low Frequency Oscillation of TBB in Summer of Qinghai-Xizang Plateau and Drought/Flood in Central China
• HE Yi-hua;LI Cai-yuan;JIN Qi;WANG Xiao-ling
• 2006 Vol. 25 (4): 658-664. 
• Abstract ( ) PDF (1990KB) ( )
• The relationships between the low frequency oscillation(10~20 d,30~60 d) of TBB in summer of Qinghai-Xizang Plateau(QXP) and drought/flood in Central China(CC) were analyzedby compositingthe TBB's pentad anomaly of summer drought/flood in CC,using the 17-year pentad mean GMS TBB data.The results show that the Southeast QXP(27°~30°N,90°~100°E) is the most active area of the low frequency oscillation,especially there is positive relation with the TBB in CC which is more remarkable in the flood year than in the drought year.The 30~60 d low frequency oscillation over the Southeast QXP is more sensitive than the 10~20 d low frequency oscillation.In the drought(flood) year of CC,there is stronger(weaker) negative center of TBB's low frequency oscillation in the Southeast QXP,and its influence way is some spread from west to east,some strengthen or weaken with the low frequency of TBB(30~60 d) in CC.The negative phase of TBB's low frequency(30~60 d) over QXP contributes to the convective cloud growing and developing.

• Experiments of Soil Moisture Data Assimilation System Based on Ensemble Kalman Filter
• HUANG Chun-lin;LI Xin
• 2006 Vol. 25 (4): 665-671. 
• Abstract ( ) PDF (473KB) ( )
• Ensemble Kalman filter is a new sequential data assimilation algorithm which originally developed from the field of atmospheric data assimilation.It calculates background error covariance matrix using Monte-Carlo method and is able to resolve the nonlinearity and discontinuity exist within model operator and observation operator.When observation data are assimilated at each time step,background error statistics estimated from the phase-space distribution of an ensemble of model states are used to calculate the Kalman gain matrix and the analysis increments.In this work,we develop A one-dimensional land data assimilation scheme based on ensemble Kalman filter and simple biosphere model(SiB2) to assimilate soil moisture observation.We also do some assimilation experiments using GAME-Tibet observation data from July 6 to August 9,1998,at the MS3608 station on the Tibetan Plateau.Once every 6 hours,in situ observations of soil moisture at the depths of 4,20,100 cm are assimilated into land surface model(SiB2) and the best estimations of soil moisture at the surface layer,the root zone and the deep layerare calculated.The results indicate that the data assimilation can significantly improve the soil moisture estimation in the surface layer,the root zone and the deep layer.And we think that the Ensemble Kalman filter is both practical and effective for assimilating in situ observation into land surface models.

• Numerical Simulation on a Severe Sand-Dust Storm Process Caused by the Mongolia Cyclogonesis
• JIANG Xue-gong;ZHAO Lin-Na
• 2006 Vol. 25 (4): 672-679. 
• Abstract ( ) PDF (768KB) ( )
• Using the sand-dust storm numerical predict model,which coupling MM5 model,sand-dust raising and transporting models and GIS dataset,a severe sand-dust storm process occurred over the Northern China from 6 to 8 April 2001 has been done numerical simulation experiment.The results showed that the strength and evolution of Mongolia cyclone,the intensity,position and evolution of sand-dust storm have been successfully simulated.The sand-dust source regions in this process were in south Mongolia and western Inner Mongolia of China.The small diameter dust(d≤22 μm)was in a dominant position among the sand-dust particles contributing to the formation of sand-dust storm.The modeling diurnal change of sand-dust storm strength,which acted as intensive in daytime while as weak at night,was greater than the observational one.The sand-dust radiation heating,which exists in real atmosphere but is not considered in the model,will minimize the diurnal change of atmospheric stratification and the intensity of sand-dust storm.

• Analysis on Circulation Difference of Sandstorms with Different Intensities in Ningxia
• CHEN Nan;CHEN Xiao-guang;ZHAO Guang-ping
• 2006 Vol. 25 (4): 680-686. 
• Abstract ( ) PDF (658KB) ( )
• The circulation difference feature of sandstorm with different intensities at the same period of Ningxia was diagnostically analyzed using the sandstorm process data of Ningxia in 1970-2003 and reanalyzed global daily data of NCEP/NCAR(1971-2000),according to the sandstorm intensity standard.Results show that the frequencies of very severe,severe and general sandstorms have obvious different under different circulation backgrounds,one ridge and one trough pattern,northwest route cold air path is the most main circulation and cold air pattern in very severe and severe sandstorm process of Ningxia region;since the intensity and location of Ural high pressure ridge,Baikal cold low pressure,Mongolia cyclone and surface cold high pressure are different,the caused sandstorm intensities have significantly differences.At same time,the different distributions of upper level westerly jet on 200 hPa is closely related to the intensity of Ningxia sandstorm.

• Diagnostic Analysis of a Severe Convective Storm ahead of Trough in Shaanxi
• LIU Yong
• 2006 Vol. 25 (4): 687-695. 
• Abstract ( ) PDF (623KB) ( )
• The diagnostic analysis of severe convective storm ahead of trough line happened in middle of Shaanxi province on 5 August 1995 has been done.The result shows that one of main reasons for the severe storm was not the dry air at the middle level(dry and warm lids),but the dry air at the lower level which invaded thunderstorm area.Under condition of preferable water vapor at middle level,the change of vapor flux from high to low was primary cause of the transition from rainstorm to severe convective storm.

• Diagnostic Analysis of a Heavy Snowstorm Processe in Lower Latitude Plateau of China
• ZHANG Teng-fei;LU Ya-bin;ZHANG Jie;PU Gui-ming
• 2006 Vol. 25 (4): 696-703. 
• Abstract ( ) PDF (2117KB) ( )
• Using the conventional meteorological data,the various variable fields,the satellite and the Doppler radar echo images,the heavy snow process on February 7,2004 has been analyzed.The results show when the Xinjiang upper trough oriented in NE-SW direction changes its orientation into N-S direction and moves eastward,the cold air from the north diffuses continually southward,accumulates and intensifies in the boundaries among Sichuan,Guizhou and Yunnan,makes the Kunmin stationary front to intensify,move westward and affect the mid-Yunnan province.Meanwhile the satellite images also show that the cloud area of the southern brauch trough in India intensies,moves eastward and merges with the forementioned strong stationary front cloud area,so the moderat-heavy snow storm occur in mid- and east-Yunnan.Because of the function of the relief,there is light rain in west Yunnan mostly.Southwest wind enhancement,water vapour flux increase,ascending motion enhancement and water vapour convergence in upper level arouse the heavy snow process in central and east Yunnan.In the meantime the cold and warm advections and the southwest jet in upper level are the main characters of the heavy snow in the Doppler radar velocity fields.This further substantiates that the water vapor condition brought by southwest airflow is very important to snowfall in lower latitude plateau.

• Modeling of 3D Miltisource SO₂ Concentration Field under Benxi Complex Terrain
• MA Yan-jun;ZUO Hong-chao;WANG Yang-feng;LIU Ning-wei
• 2006 Vol. 25 (4): 704-709. 
• Abstract ( ) PDF (345KB) ( )
• The spatial-temporal distributions of SO₂ in Benxi region is simulated using the method of difference for solving the 3D equation of the atmospheric diffusion.The contrast of the simulated and observed values shows that the calculated result of modle basically reflect the real change of SO₂ concentration.On the basis of the calculated result, it is found that the pollution of SO₂ in Benxi is very severe, and the spatial-temporal distributions of SO₂ concentration appear obvious dayily change.The number of concentration of SO₂ is higher before 10:00, and after 10:00, the number of concentration gradually became low, the number of concentration of SO₂ became slowly high around 18:00.

• Application of Genetic Algorithm in Optimizing the Z-R Parameter to Radar Rainfall Estimation
• XU Zhi-fang;XIONG Jun;GE Wen-zhong
• 2006 Vol. 25 (4): 710-715. 
• Abstract ( ) PDF (1040KB) ( )
• A real coded genetic algorithm(GA) using GUC crossover is introduced to optimize the Z-R parameter for radar rainfall estimation and a new error function is proposed with the control of total rainfall estimation error.This new method is compared with the conventional Least Means Method(LMS),Optimized Method and M-P parameter with the Fuyang radar data and associated raingauge data from June 28 to July 2,1998.Experiment result shows that the accuracy of total rainfall estimation is increased and the new method is more adaptive.

• Analysis on Short-Time Forecast of Severe Convection Weather Based on Stability and Energy Indexes
• ZHOU Hou-fu;QIU Ming-yan;ZHANG Ai-min;ZHAI Jing
• 2006 Vol. 25 (4): 716-722. 
• Abstract ( ) PDF (303KB) ( )
• Based on the severe convectionweather data and upper sounding data from 1995 to 2001,the instability and energy indexes are calculated,which are K index,A index,potential instability index,the energy balance level,potential instability energy,respectively.The tests and comparison among some indexes have been done.The results show:(1)A and K index values have some effects on forecasting severe convectionweather.(2)The forecast effect of potential instability index in south may be better than that in north.(3)The energy balanceheight and potential instability energyin every year are divided with two stages.(4)The energy balance level is rather high during the severe convectionweather.With the potential instability energy enhance,the appearance possibility of severe convection increase.

• Numerical Simulation of Cloud Microphysical Structure and Artificial Seeding Condition in Precipitation Cloud in Shandong Province
• GONG Dian-li;WANG Jun;LIU Shi-jun
• 2006 Vol. 25 (4): 723-730. 
• Abstract ( ) PDF (1491KB) ( )
• Using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research(PSU/NCAR) Mesoscale Model(MM5 V3.5) and operational weather data,the heavy storm occurred on 17 April 2003 and the cold front rainfall occurred on 24~25 October 2002 in Shandong Province were successfully predicted.The data output from model,especially the quality content of ice(Q_i),graupel(Q_g),snow(Q_s),cloud water(Q_c) and rain water(Q_r) calculated by Reisner explicit microphysical schemes were analyzed to describethe characteristics and evolvement of cloud microphysic structures in two cases.The results shown that the mecro-synoptic dynamic action and the vapor transfer process play a key role in the development of the rainfall.The opportunity of artificial seeding in different conditions was discussed.

• Studies on Characteristic and Prediction of Dog-Days Drought in Anhui Province
• TIAN Hong;XU Min;LI Shu;CHEN Xiao-hong
• 2006 Vol. 25 (4): 731-736. 
• Abstract ( ) PDF (859KB) ( )
• Using the daily precipitation data of 35 stations in Anhui Province during JJA from 1961 to 2003,100 hPa and 500 hPa geopotential height fields over the Northern Hemisphere,sea level pressure over Northern Hemisphere,sea surface temperature over tropical Pacific Ocean from previous September to next May during 1961-2002,the characteristics of dog-days drought are analyzed.The results of Empirical Orthogonal Function(EOF) show that there are three main rain patterns during dog-days drought period in Anhui province: The whole provincial,the southern or northern,and the middle patterns.The correlation between the three time coefficients and the previous factors(H100,H500,SLP,SST) are studied, respectively.Then three prediction models for the three time coefficients can be constructed in terms of a stepwise regression with the aid of the previous significant correlation factors whose value are area average of the key regions in the correlation fields.After the three time coefficients are predicted by the models,the total of the three time coefficients multiplied by their eigenvectors is the predictive rainfall field.It is concluded that the models are superior in fitting,and experimental forecasting of 2001,2002 and 2003 indicate that the models have an ability to predict the dog-days drought in Anhui Province.

• Analyses on Spatial-Temporal Change Characteristics of Rainfall over Chinese Loess Plateau from April to October
• WANG Yi-rong;WANG Xi-wen
• 2006 Vol. 25 (4): 737-743. 
• Abstract ( ) PDF (529KB) ( )
• Using the observed precipitation data over Chinese Loess Plateau from April to October in recent 40 years,the spatial-temporal changes of the rainfall are studied,the distributions of precipitation anomaly in dry and wet years are analyzed as well.The results show that the rainfall over Chinese Loess Plateau in April~October appeared an abrupt change in 1985 or so,and since then on the more rain year change into less rain year.The wavelet analysis shows that the anomalous changes of precipitation had 3~5,8 and 11~16 year oscillation periods,but 3~5 year periods were more obvious.There were three sensitivity regions of anomalous precipitation over Chinese Loess Plateau,and two phases appear obvious in the years of 1985.The rainfall amount in dry and wet years had obvious difference,and the one of wet year was more 40% than that of dry year.The differences of dry and wet years were remarkable.Also,the dry year occur easier in the northeast of Chinese Loess Plateau,and wet year,in north.

• Study on Changes of Water Resources in Hanjiang and Upper- and Mid-Reaches of Yangtze River Valley in Recent 531 Years
• ZHOU Yue-hua;WANG Hai-jun;GAO Xian-lai
• 2006 Vol. 25 (4): 744-749. 
• Abstract ( ) PDF (254KB) ( )
• Using the atlas of drought and flood distribution of China in 500 years and precipitation data at 10 representative stations in Hanjiang and upper- and mid-reaches of Yangtze River vallies from May to September 1953-2000,the grade series of drought and flood of two rivers in recent 531 years were established,the change charateristics of drought and flood of two rivers,and the relation of their grades and water amount are analyzed.The consistency of two rivers are analyzed using the α²-test,it is found that,when there were severe drought in Hangjiang river and severe flood in Yangtze River,their consistency was good.The analysis through a kind of high- and low-decade water index(HLDI) show that the probability of simultaneous occurrenceof high water was rather great in the two rivers,and drought in Hanjiang River valley was characterized by relative convergence and a long duration.The water resources of Hanjiang and in upper- and mid-reaches of Yangtze River valley were abundant in 18^th and 19^th century,deficient in 17^th and 20^th century,respectively.The centurial changes ofwater resources of the two rivers bore a characteristics of mutual complementarity.

• The Regional Average Method of Yearly High Temperature Day Series in North China and Its Tendency Analysis
• ZHANG De-kuan;YAO Hua-dong;YANG Xian-wei;LIAO Yao-ming
• 2006 Vol. 25 (4): 750-753. 
• Abstract ( ) PDF (190KB) ( )
• Based on the data of yearly high temperature days at 33 stations in North China from 1961 to 2002,the regional averaged high temperature day series was established by optimum interpolation method.From the series,it can be seen that the year-to-year high temperature days in North China from 1961 to 1972 and from 1997 to 2002 were obviously more than normal,and the interannual variability in North China was obvoius during the two periods.On the other hand,the high temperature days frommid of 1970's to mid 1990's was less than average.The parttern designed by mean generating function method can preferably fit historic series and its confidence level has passed 99%.The high temperature days in 2003-2005 have been predicted using the pattern,it is found that the impact of tendency prediction in 2003 and 2004 is better.

• Research and Application on Helicity in China
• YUE Cai-jun;SHOU Yi-xuan;SHOU Shao-wen;QI Liang-bo;SHI Hong
• 2006 Vol. 25 (4): 754-762. 
• Abstract ( ) PDF (384KB) ( )
• The domesticstudies of theory and application on the helicity since 1990's are reviewed substantially and systematically.The helicity is classified as vertical helicity,horizontal helicity and perfect helicity,meanwhile,the vertical helicity is classified as local vertical helicity and integrated vertical helicity.The formulas of vertical,horizontal and perfect helicity are introduced and provided,in the mean time,the status of each kind of helicity application to synoptic diagnosis is induced completely.What is more,the present applied situation of the helicity is discussed and analyzed simply,along with a prospective study in this field at last.