ZHENG You-fei , FAN Min-hao , ZHANG Xue-fen , WU Rong-jun
2008, 31(2):145-150.
Abstract:MODIS(Moderate-Resolution Imaging Spectroradiometer) remote sensing data have higher radiometric sensitivity,but its lower spatial resolution always causes the pixel’s impurity,normal classification methods of land cover can not solve this problem.In order to achieve the classification of land cover a line spectral mixture model was used in MODIS data pixel unmixing of Zhengzhou area.The preprocessing of MODIS data,line spectral mixture model(LSMM),and methods for solving image end-member’s reflectance were also discussed.The classification result was compared with the class map derived from Landsat ETM+ data.The RMS shows that the pixel unmixing method has good results and the MODIS data can be effectively applied to remote sensing dynamic monitoring,and land cover classification.
FENG Min-xue , WEI Hai-rong , JIAO Sheng-ming , ZHOU Ceng-kui , WANG Xi-zhong , JIAO Xue
2008, 31(2):151-157.
Abstract:In order to fully utilize the lightning strike positioning systems of Jiangsu province,thus to achieve better results of the alarm and forecast services,the article uses a variety of visual-observation lightning information,and Doppler radar echoes to make an inspection analysis on the dependability and detection efficiency of the lightning strike positioning data from June to August of 2006,within 10km from Xiaojiaochang of Nanjing(32°00′N,118°48′E).The results show that the lightning strike data obtained by the lightning strike positioning system of the Jiangsu provincial meteorological department are dependable,the undetected lightning rate is within the tolerance range of the detection efficiency η and the incorrect detection rate is around 9%,which is also within the tolerance range.As is indicated by an inspection and analysis on the lightning strike positioning data obtained by the system of Jiangsu provincial power department in the same period and the same area,the detection system is much poorer in the correct detection rate than that of the Jiangsu provincial meteorological department.After a proper amendment to the lightning strike positioning data obtained by Jiangsu power department,well consistency between the two sets of data was found,and therefore the two sets of data are mutually sharable and complementable.
DAI Kan , LUO Zhe-xian , TENG Dai-gao
2008, 31(2):158-166.
Abstract:In the framework of vortex self-organization dynamics,the influences of a small-scale system on the self-organization process of two meso-β vortices are investigated by utilizing an ƒ-plane 2D quasi-geostrophic barotropic vorticity equation model.Four groups of numerical experiments are performed,and the results show that: the small-scale system may change the two vortices interaction and trigger the merging process;the final state is sensitive to the initial location of the small-scale system;there is a "Z" shape sensitive region,when a small-scale vortex initially appears there,resulting in the fact that the interaction stage of the two vortexes is more likely to be changed;for altering the vortices interaction results,the small-scale system should satisfy the following three necessary conditions:an initial position in the "Z" shape sensitive region,proper distances to other two vortices,enough intensity and longer life cycle.
LIANG Lin-lin , SHOU Shao-wen , MIAO Chun-sheng
2008, 31(2):167-175.
Abstract:Using the ageostrophic wet Q vector(Q*),modified ageostrophic wet Q vector(QM) and Q vector partitioning theories,a Meiyu front weather process which occurred in the Jianghuai River Valley in July 2005 is diagnostically analyzed and the diagnosis ability of Q* and QM compared.The results show that the release of the convective latent heat played an important role in the formation and maintenance of the meso-scale system.By dividing the wet Q vector into two parts of parallel and perpendicular to isotherms,it is shown that the large-scale convergence deminated at the low levels at the intensifying stage of the rainstorm,however,at the high levels,the situation was apposite,and meanwhile the meridionally secondary circulation appeared.All those show that the subsynoptic-scale persistent moisture convergence and the positive feedback mechanism are the key factors responsible for the rainstorm event.
ZHANG Yan , SUN Zhao-bo , BAI Ying-ying , DENG Wei-tao
2008, 31(2):176-182.
Abstract:Daily precipitation of April,May and June during the period 1958—2004 from 61 observational stations is applied to study drought/flood characteristics of the pre-flood season in South China with statistic methods.Results show that 12 flood years and 12 drought years occurred in 1958—2004,with severe flood/drought years mainly in the late 1950s—the middle 1970s and after the 1990s;and the interannal period of 2—4 years was most remarkable in the flood/drought variations of the pre-flood season.The interdecadal character of the flood/drought variations for April and May was consistent,while the interdecadal variations for May and July showed an out of phase relation.South China can be geographically divided into five flood/drought anomaly sub-areas,and in the past 46 years,the pre-flood season climate showed an evolution trend of drought-flood-drought in southern Guangxi,western Guangdong,and the southeast coast region,a trend of drought-flood in northern Guangxi,and a trend of flood-drought in the northeast part of South China.
SHEN Gui-feng , WU Hong-bao , WEI Ying-ying , LIU Xue-hua
2008, 31(2):183-191.
Abstract:Based on the NCEP/NCAR reanalysis data of OLR,Nonlinear Principal Component Analysis(NLPCA) are used to research the convective activity over the tropics and its relationship with ENSO.The results show that more nonlinear characteristics of time-space structer are found by using NLPCA than by linear analysis techniques.Such nonlinear characteristics may reflect the nonlinear relationship between tropical convective activities and ENSO.The intensity of OLR anomalies is stronger in the average El Nino period than in the average La Nina period.And the center of OLR anomalies in the averger in the average El Nino period tends to lie at a position east of that in the average La Nina period,thus showing the spatial asymmetry of OLR in the average warm and cold phases of ENSO.
ZHANG Ling , ZHANG Yan-ling , LU Han-cheng , SHOU Shao-wen
2008, 31(2):192-199.
Abstract:The atmospheric unstable energy accumulation and release play a key role in the formation of severe convective weather.A mesoscale severe convective storm with tornado and hails at 1730 BST July 12,2004 in Nantong,Jiangsu Province is analyzed in this paper by using the conventional observational data and the NCEP/NCAR 1°×1° reanalysis data.The results show that beore 1730 BST July 12 the stratification was unstable with dry and cold air at the upper level and warm and moist air at the lower level over Nantong,and dry air intrusion and its strong convergence with the warm and moist air in the boundary layer induced the release of unstable energy and the formation of tornado.Based on the numerical simulation results,parameters IBCAPE,ICIN,INCAPE,IEHI and ISWEAT etc are calculated,and it is found that the parameters and indexes were good indicators for the severe weather including this tornado.
DU Chun-li , SHEN Xin-yong , CHEN Wei-min , SHI Shuai-hong
2008, 31(2):200-207.
Abstract:Based on climatic ocservational data and radiation information from 1961 to 2003,the interannual trends of cloud cover,sunshine percentage,relative humidity,temperature,precipitation and solar radiation at the earth surface are all investigated.The results show:1)the total cloud cover has decreased and the low cloud increased in most of the ten cities in recent 43 years;2)the sunshine percentage has reduced greatly,the relative humidity decreased except Urumqi,the temperature increased significantly,and the amount of rainfall changed slightly and regionally;3)the total solar radiation at the earth surface has decreased remarkably except Kunming,which was mainly caused by the reducing of direct solar radiation.These results suggest that cities in our country have experienced warming and drying processes,and human activities,especially industrialization and urbanization,have important influence on the climatic system.
SHEN Tong-li , HE Ru-yi , ZHANG Li-hong , HE Di
2008, 31(2):208-213.
Abstract:In this paper,the AMSU(Advanced Microwave Sounding Unit) data from NOAA-16 satellite are used in the simulation of the heavy rainfall event in the Changjiang-Huaihe River Valley during July 4—5 2003.When the atmospheric temperature,wind and humidity retrieved from the AMSU are added into the MM5 Adjoint Model,the initial fields are improved,especially in temperature and humidity.Compared with the simulation results from the MM5 model using only conventional observations,it is found that retrievals have ability to reveal clearly the structure of temperature and humidity fields,thus obviously improving the intensity and location of model precipitation,so that the accuracy of MM5 Adjoint Model’s rainfall prediction and its Ts grades are greatly improved.
LI Qing , LIU Xuan-fei , PAN Ao-da
2008, 31(2):214-220.
Abstract:By using 1958—1998 NCEP/NCAR reanalysis,1975—1998 OLR and 1973—1998 monthly snow cover days(SCD) at 115 stations over the Tibetan Plateau(TP) and its peripheral areas,the possible mechanism of impacts of winter-spring snow cover on the South China Sea(SCS) monsoon onset is investigated.The increase in winter-spring snow cover is associated with the weakening of sensible heating over the TP,and with the decrease in temperature in the middle-upper troposphere over the TP and its east side,thus leading to a later reversion of large-scale meridional temperature gradient.At the same time,the seasonal reversion of Hadley Circulation in the TP region will also take place later than normal,with the abmormal descent airflow maintaining over the Indo-China Peninsula(ICP),causing a later split of the subtropical high over the Bay of Bengal,and a later outbreak of convective activities over the ICP,in such a way that the surface temperature over the ICP will decrease later,resulting in a later reversion in local zonal temperature gradient between the ICP and the SCS.The SCS monsoon may outbreak later under the joint action of the above large-scale meridional and local zonal temperature gradients.
HOU Tuan-jie , NIU Sheng-jie , LEI Heng-chi , GUO Xue-liang , SUN An-ping
2008, 31(2):221-227.
Abstract:Charges accumulation and electric field development within two convective clouds which had different degree of convection and wind shear in Changchun were simulated by introducing an improved noninductive charging mechanism including the influence of particle diameters and impact velocity into the three-dimensional dynamics and electrification coupled model.The numerical results show that tripolar structures are produced when the updraft velocity reaches the maximum value for the strongly-developed cloud,and an inverted dipole for the other cloud.Updraft is an important parameter reflecting the development of electric field.For the strongly-developed convective cloud,there are rapid rises of inductive and noninductive charging rates as a result of large amounts of graupel and ice crystals in the middle and upper part of the cloud due to stronger updraft velocity.
ZHAI Yu , XIAO Hui , DU Bing-yu , LIU Jin-hua , YAO Zhan-yu
2008, 31(2):228-233.
Abstract:In this paper the statistical test of cluster analysis suggested by Professor Yao Zhensheng(1994) was used to improve the original Cluster-Analysis-based Floating Control historical regression Method.The new method can diminish blindness in cluster analysis,increase the correlativity of stations precipition in the same cluster,and make the cluster analysis have statistical meaning.The assessment of precipitation enhancement in the cloud seeding operation cases in April in Henan Province were performed using the new method and the original one,the results show that the evaluation effctiveness is improved greatly by introducing in the cluster test.
2008, 31(2):234-241.
Abstract:Based on NCEP/NCAR reanalysis data and the daily precipitation of 25 stations in southern China,the relationship between the anomalies of the summer precipitation in southern China and the upper level geopotential height and temperature anomalies in the spring and summer 2003 was analyzed.Results show that the Subtropical Anticyclone over the Western Pacific during the summer 2003 shifted southward and northward,and controled the most part of the southern China,which resulted generally in the meager rainfall in the area during the summer.The South Asian High in the summer 2003 was much stronger than normal and extended eastward,dynamically inducing the westward extension of the Subtropical Anticyclone over the Western Pacific.The overlay area of the South Asian High and the Subtropical Anticyclone corresponds primarily to the area with drought.In addition,the summer precipitation in southern China correlated significantly with the temperature at 100 hPa with a lag of 1—2 months.The previous temperature anomalies at 100 hPa in middle and high latitudes may serve as an important predictor for the drought and flood in southern China.
HAN Xue , SHEN Tong-li , SHEN Xin-yong
2008, 31(2):242-249.
Abstract:The multigrid method,one of the most efficient iterative algorithm nowadays,possesses of the advantages of fast convergent speed and high accuratcy.Adaptive mesh technique aims at improving the accuracy of prediction by arbitrarily densifying the grids in areas where the gradient of quantities is large.By use of the muti-nested mesh method to speedup the simulation process,adaptive mesh technique is developed with MM5 model to simulate a rainstorm in south of Yangtse River from 17th to 18th June 2002.The result indicate that if the accurucy requirement of convergence is high,the amount of precipitation simulated by adaptive mesh model approaches the observation better than that simulated by uniform mesh model,and the multigrid method can raise the computing efficiency successfully,but if the accurucy requirement of convergence is very low,the multigrid method may be invalidated.
ZHAO Xiao-yan , SHEN Shuang-he , SUN Hu-sheng
2008, 31(2):250-256.
Abstract:This paper uses the routine meteorological data for the past 31 years,starts with the three basic factors(temperature,relative humidity,wind speed) which affect person’s easiness and utilizes the method of fuzzy evaluation to assess pentadly comfortable indices in Nanjing city in detail.The results of analysis and assessment provide some scientific guidance to tourist industry in Nanjing.
LI Yong-xiu , LUO Wei-hong , NI Ji-heng , CHEN Yong-shan , XU Guo-bin , HAN Li , CHEN Chun-hong
2008, 31(2):257-263.
Abstract:A simulation model of development stages of greenhouse cucumber(Cucumis sativus) was developed based on photo-thermal reactions of crop development rate.The concept of physiological development time(PDT) was used as the scale to measure the greenhouse cucumber development stages.Experimental data of different varieties were used to validate the model.The results show that the PDT value for the duration from sowing date to the first harvest date was 30 days,with 3,11,9,5,2 days,respectively,for the duration from sowing to germination,germination to tendril elongation,tendril elongation to flowering,flowering to fruit setting,and fruit setting to first harvest.The root mean squared error(RMSE) between the simulated and observed results for duration of germination,five leaf stage,tendril elongation,flowering,fruit setting,and from sowing to first harvest,respectively,was 0,2.6,1.7,0.8,2.1,1.4 days,which was lower than the prediction errors using the growing degree days(GDD)(0.7,10.0,5.7,2.4,2.5,22.0 days,respectively).
ZHU Lin , SHOU Shao-wen , PENG Jia-yi , ZHANG Hong-hua
2008, 31(2):264-271.
Abstract:Ensemble Kalman filter(EnKF) is used to assimilate the sounding data of a torrential rain process in July 2005 into the mesoscal model MM5.The experiment results show that under the assumption of perfect model,the analysis of EnKF assimilation is closer to the real observations,and the emsemble prediction with the EnKF assimilation is better than that without the EnKF assimilation and the single numerical prediction without adding perturbations.
GAO Qi , SUN Zhao-bo , DENG Wei-tao
2008, 31(2):272-276.
Abstract:Based on the NECP/NCAR daily reanalysis data from 1948 to 2004 using the methods of filtering accumulative anomaly,Morlet wavelet transform and composite analysis,we studied the inter-decadal variation characteristics of the intensity,longitude,latitude and area index of North Pacific storm tracks,and found that the mean intensity of storm track centers during the 56-yr is about 32 dagpm2 and it locates at about 44.5°N,172°W.Morlet wavelet analysis indicates that its strongest interdecadal periodical signal is 18-yr.Besides,the intensity of the centre and area index of storm tracks have a good mutual corresponding relationship.Generally,when the intensity becomes strong(weak),the area expands(shrinks) with a westward(eastward) and southward(northward) shift of the center.
WANG Wei , ZHU Wei-jun , DUAN Yi-hong , YU Hui , JIANG Le-yi , WANG Xiao-feng
2008, 31(2):277-286.
Abstract:Using large-scale reanalysis files and stationary satellite cloud pictures,we analyzed respectively the lager-scale circulation backgrounds associated with tropical cyclone formations in the Western North Pacific between 1995 and 2004.And we got a conclusion that about 27.5% of tropical cyclogenesis cases in the past ten years were attributed to the Intertropical Convergence Zone(ITCZ),45.6% occured in monsoon troughs,10.1% occurred in easterly waves,10.4% occured under Tropical Upper Tropospheric Trough(TUTT),and 6.3% occurred in baroclinic disturbances.We analyzed the characters of tropical cyclones under different large-scale circulation backgrounds,such as life cycle,origion,intensity,horizontal scale,and landfall,and finally found that TCs of baroclinic disturbance category had a shorter life and was weaker than any other category of TCs.The average life cycle of the baroclinic disturbance category of tropical cyclones was 108.60 h,and the average intensity 39.250 kn,while the average of others was about 200 h and 70—80 kn respectively.1/3 of the monsoon trough category of tropical cyclones would land in China,which is of the highest possibility.The secondary was the easterly wave category.TCs of baroclinic disturbance category were of least possibility.Only those that formed in the South China Sea might land in China.
HUANG Xiao-yan , JIN Long , YAO Cai , HUANG Ming-ce
2008, 31(2):287-292.
Abstract:Based on the samples of typhoons in July,August and September from 1960 to 2003 over the South China Sea,multivariate regression prediction models of typhoon track for July,August and September developed by using the condition number method in selecting predictors from numerical prediction products and predictors used in the CLIPER model of typhoon track,and prediction experiments indicate that the average error of the three models is 153.9 km,which is smaller than those of objective prediction models currently used in China and western countries.Comparison experiments of new regression models with stepwise regression models and CLIPER models are performed under the conditions of identical modeling and independent samples and identical or almost identical predictor mumber,and results show that new regression models are superior to the stepwise regression models in prediction accuracy,and the forecast skill of new regression models relative to the CLIPER models is positive.
Address:No.219, Ningliu Road, Nanjing, Jiangsu, China
Postcode:210044
Tel:025-58731158