ISSN 1000-0526
CN 11-2282/P

Volume 34,Issue 7,2008 Table of Contents

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  • 1  Study on Extrapolation Technique of Weather Radar Echo and  Its Application to Nowcasting
    Zhu Ping Li Shengchen Xiao Jianshe Xu Liang Jin Shiqiang
    2008, 34(7):3-9. DOI: 10.7519/j.issn.1000-0526.2008.07.001
    [Abstract](887) [HTML](152) [PDF 2.37 M](1279)
    The basal data of volume scanning of Doppler radar is extrapola ted.Based on the ripe COTREC (Continuity of Tracking Radar Echo b y Correlation vectors) and centroid tracking technique,the “subpixel" veloci ty is computed by Fourier phase analysis technique, so the echo data and its image are obtained through extrapolation.Furthermore,the distribution of precipitat ion intensity is worked out based on the ZR formula.The extrapolated resu lts with and without use of subpixel velocity are compared with actual intensi ty data of volume scanning,the distribution of precipitation and one hour preci pitation (OHP) product of PUP in WSR88D are compared with the data of automati c precipitation station records. The analysis results indicated that the accura cy of using subpixel velocity in extrapolation is higher than t hat of nonuse,and the re liability of one hour precipitation through extrapolation is greater than the OH P of PUP.The extrapolation technique is tested in different kinds of weather pr ocess. The findings show that this technique is applicable,can improve the tech nique of TREC, and has some referenced value in nowcasting.
    2  A Statistical Analysis of Intensity Change of Tropical Cyclones Landing Taiwan
    Dong Lin Duan Yihong
    2008, 34(7):10-14. DOI: 10.7519/j.issn.1000-0526.2008.07.002
    [Abstract](772) [HTML](93) [PDF 343.94 K](968)
    A statistical analysis on the intensity change of tropical cyclones (TC) that pa ssed Taiwan is performed. The data of 58 years (1949-2006) from Typhoon yearbook and tropical cyclone yearbook compiled by Chinese Meteorological Administration (CMA) is used. The records of each typhoon are linearly interpolated to one hou r per record. Only TCs that passed Taiwan are picked out for analysis. Several c onclusions can be obtained from the statistics. First of all, the intensity loss of TCs landing from the east side is twice more than that of TCs from west side . Secondly, the more perpendicular the angle between the route direction of land ing TC and long axis of Taiwan central mountain, the smaller the intensity loss and duration on the land. Thirdly, there is a positive correlation between the i ntensity loss and initial intensity for the TCs landing from the east side where as no such correlation exists for TCs from west side. Fourthly, the probability that the intensity remains the same or increases of TCs landing from the west si de is higher than that of TCs from the east.
    3  Analysis of Tornado Events in North Anhui and Jiangsu Provinces in July 2007
    Cao Zhiqiang Fang Zongyi Fang Xiang
    2008, 34(7):15-19. DOI: 10.7519/j.issn.1000-0526.2008.07.003
    [Abstract](776) [HTML](120) [PDF 12.55 M](2850)
    There were many tornadoes produced in the area between Tianchang of Anhui P rovince and Gaoyou of Jiangsu Province, and also [JP2]in Xinghua of Jiangsu Province between 0840-1000UTC[JP] on July 3,2007. It was one of the extreme weather events of 2007. High temporal resolution geostationary satellite of FY2C and 2D, Nanjing Doppler weather radar data and routine meteorological data were used in analyzing the evolution of the weather system. The main conclusion was as follows: The dynamic and thermal conditions for strong convection development were provided bythe combination of the short wave trough with cold dry air at high altitude, wa rm moist air advection at low altitude and the divergence field at the north of the ridge line of Tibet high pressure. After 0400UTC, two mesoscale convective c loud belts were developed in the coboundary area of Anhui, Henan, Hubei and Ji angsu provinces. One of them, corresponds to the shear line on Meiyu front and i s rather weak. The other was the fast developing squall line at the south of the first cloud belts and in front of the cold air mass. The weak convective cloud belt moved south slowly. The convective cells in it propagated toward east. The squall line moved from west northwest to east southeast. The strong convective c ells in it propagated from west southwest to east northeast. The tornadoes deve loped in the area where the convective cells in two mesoscale convective cloud b elts merged.
    4  Discussion on the Generation Mechanism of “5.6" Gust Front
    Huang Xuanxuan He Caifen Xu Difeng Wang Yongsheng
    2008, 34(7):20-26. DOI: 10.7519/j.issn.1000-0526.2008.07.004
    [Abstract](897) [HTML](1557) [PDF 9.12 M](991)
    Comprehensive data, including weather pattern, Doppler radar, AWS on a gust fron t occurred on May 6,2007 were analyzed and compared with the squall line on June 10,2006 and a gale process on June 28,2007. Results show that generation mechan ism of a narrowband echo accompanying gale wind is of abrupt refractive index changes along the interface between warm and cold air masses, which lead to elec tromagnetic wave scattering and reflecting, and in turn forms weak echo. Another important factor is the sinking and diffusing motion of cold air in upper level . Behind the narrowband echo, there probably is no main echo following. The fr ont of inclining downdraft is unfavorable to the narrowband echo.
    5  The Roles of Drycold Air Incursion on Persistent Snowfall in Shandong Peninsula During December of 2005
    Qiao Lin Lin Jian
    2008, 34(7):27-33. DOI: 10.7519/j.issn.1000-0526.2008.07.005
    [Abstract](899) [HTML](108) [PDF 2.45 M](958)
    In terms of observed data and NCEP reanalyzed data, circulation background and d rycold activity features of the persistent snowfall in Shandong Peninsula duri ng December of 2005 were analyzed. The roles of drycold air in this event were researched by using the moist potential vorticity and frontogenesis theories. T he results suggested that the change of snowfall in Shandong Peninsula could be well reflected by the lowlevel humidity field, while it was closely associated with upperlevel drycold air. The uppertroposphere potential vorticity are a was corresponded with the low relative humidity area. Dry air came mainly from the northern part (high latitude) of uppertroposphere. The down and sou thstretching of potential vorticity area and low humidity area were correspond ed with the lowlevel moist symmetry instability area. The severe snowfall occurred under the common actions of the lifting of topographic and frontogenesis forcin g of lowlevel saturation moist air, as well as the releasing of moist symmetry instability energy. The incursion of drycold air was the trigger mechanism of the releasing of instability energy.
    6  Analyses of Observation Data Error in Numerical Forecasting Assimilation System
    Tao Shiwei Hao Min Xue Jishan Duo Yiwen
    2008, 34(7):34-40. DOI: 10.7519/j.issn.1000-0526.2008.07.006
    [Abstract](612) [HTML](115) [PDF 686.00 K](954)
    It is important to suitably estimate the root mean square of observation error i n a given assimilation system. Firstly, by using Bessel fitting method, the root mean square of observation error and root mean square of first guess error are separated from the covariance of the deviation of radiosounding observation an d first guess. Then the root mean square of other observation error for other ob servation types are estimated by deducting the root mean square of first guess e rror from the covariance of the deviation of radiosounding observation and fir st guess. The observation data during 1-31, August 2006 and the first guess from T213 numerical weather prediction system are used for analyzing the root mean s quare of observation error. The results show that the estimated root mean square of observation error for each observation type is reasonable.
    7  Comparisons Analysis of Rainstorm Processes in Hunan Province Caused by Typhoon BILIS and SEPAT
    Pan Zhixiang Ye Chengzhi Liu Zhixiong Xulin
    2008, 34(7):41-50. DOI: 10.7519/j.issn.1000-0526.2008.07.007
    [Abstract](464) [HTML](104) [PDF 3.11 M](848)
    The comparative analysis between “BIILIS” and “SEPAT” which had a sobering e ffect to Hunan Province was conducted by using the meteorological and hydrograph ic conventional intensive observational data and NECP reanalyzed data. Results s how that the strength and scope of the precipitation brought from Bilis and Sepa t had significant differences. The precipitation of Bilis mainly located in the southeast side of the low pressure circulation and induced the rainstorm in the southeast area of Hunan. The scope of the precipitation of SEPAT was widespread, and the area of heavy precipitation moved from east to west and lasted longer t han Bilis. Further analysis found that the differences between Bills and SEPAT i n moving route, structures and the South China Sea Monsoon intensi ty revealed obvious discrepancy in dynamic structure, distribution of moistureconvergence intensity and vertical movement. These differences are the important reasons that caused different distribution of their heavy rainfall.
    8  The Heavy Rainfall Event over Sichuan Basin During 4-5 September 2006
    Tu Nini Duan Wei
    2008, 34(7):51-60. DOI: 10.7519/j.issn.1000-0526.2008.007.008
    [Abstract](666) [HTML](165) [PDF 2.86 M](955)
    A severe drought occurred in SichuanChongqing region in 2006 summer. The high temperature disaster was rapidly weakened by the first rainstorm of autumn and the local drought situation was simultaneously alleviated. However, the strong r ain also caused significant economic loss in many areas. To better understand th e causes of the heavy rain, diagnostic analyses are given by using daily 1°×1 ° grid reanalyzed data from NCEP/NCAR at 00:00(UTC), 06:00, 12:00, and 18:0 0. The findings show that the position of low level jet is different with other process, it appears in the north side of the vortex, which sped the transfer of cold air and water vapor coming from the north. Furthermore, both the appearance and disappearance of low level jet are early to the wind convergence region, wh ich is dynamical condition of the occurrence and development of low pressure. An alysis of apparent heat source and apparent moist sink suggest that cumulus conv ection activities were active, and the convective rainfall dominated.
    9  Climatic and Statistical Analysis on Extreme Weather Events During Beijing Olympic Games
    Ding Deping Wang Chunhua Li Xun Liu Yan Liu Yifen Xie Zhuang
    2008, 34(7):61-67. DOI: 10.7519/j.issn.1000-0526.2008.07.009
    [Abstract](739) [HTML](104) [PDF 881.45 K](1097)
    Beijing 2008 Olympic Games will be held on 8-24 August. The extreme weather even ts in this period were analyzed by using the data of Beijing Observatory, Chaoya ng, Fengtai Shunyi Meteorological Stations from August 8-24(1971-2007), and Hai dian Meteorological Station(1975-2007). The results show that the maximum high temperature (Tmax) at Beijing Observatory was 37.3℃ and the occurrence probabi lity of annual Tmax>36.0℃ is 5%. The annual variation of Tmax obviously a ppears an ascending trend with the rate of 0.69℃/10a. It means that the tempera ture nowadays is in a relatively higher period, the annual mean days of Tmax≥33 ℃ at five stations is 2.8 with same increasing trend. The annual mean muggy days (Tm ax≥32.0℃ with the relative humidity ≥55%) is 4.7. The occurrence probability of daily rainfall (R≥25mm) at Beijing Observatory can reach to as high as 68%, the mean number of raining days (R≥25mm) for five stations is 1.1. The maximum daily precipitation intensity is 156.2mm/d. The mean day of thunderstorm is 3.7. These three factors mentioned above are in a lower-value periods. The mean day of strong wind (averaged wind speed ≥7m/s in 10 min) at five stations is 1.2 , and is also in a slower-speed period. The foggy day is 0.7. The day of low v isibility ≤2000m at Beijing Observatory goes down from 3.9(1990-1999) to 1.5(20 00-2007), also in a fewer-occurrence period.
    10  An Analysis of Precipitation and River Flow in  Huaihe River Basin During Summer of 2007
    Wang Weiguo Zhang Jiancheng Li Xiang
    2008, 34(7):68-74. DOI: 10.7519/j.issn.1000-0526.2008.07.010
    [Abstract](539) [HTML](164) [PDF 1.20 M](1638)
    The major flooding event during the summer of 2007 in Huaihe River Basins is stu died based on the observed data of precipitation and hydrology. The analysis of the spatialtemporal distribution of precipitation during the flooding period a s well as the hydroclimatology features is also carried out and compared with historical data. As shown from the results, the heavy rainfall occurred during t he period from 29th June to 26th July with four stages linked to four flood peak s of Huaihe River. Higher precipitation is correlated to more flood water flow, then leading to higher waterlevel. The persistent and heavy rainfall in the up per and middle Huaihe River brought about the major flood in 2007, although the average amount of precipitation for Huaihe River Basins during the flooding peri od of 2007 was equivalent to 2003.
    11  Real Time Data Processing Technique on Very ShortRange and  Nowcasting for Beijing 2008 Olympic Games
    Wang Yubin Zhou Haiguang Yu Dongchang Zhou Yong Su Debin Liang Feng
    2008, 34(7):75-82. DOI: 10.7519/j.issn.1000-0526.2008.07.011
    [Abstract](485) [HTML](92) [PDF 902.65 K](938)
    The data processing kernel problems of the very shortrange and nowcasting are analyzed in detail. These include quality control of automatic weather station d ata,data update frequency, network Doppler radar synchronization observation an d levelII data transfer in time,detecting data transfer in real time,detecti ng data monitoring and dissemination based on the directory monitoring and messa ge drive, software development based on the open source technology, and data fo rmat etc. Some techniques are adopted to meet the shortterm and nowcastin g demands. Based on these techniques,the DRAPS (Data Rapid Acquisition and Process Syste m) of nowcasting for Beijing 2008 Olympic games was developed and run in operat ion more than one year. Some advanced techniques were adopted in DRAPS,such as data transfer in real time, network radar synchronization observation, data mo nitoring and dissemination in time based on message driven, and data format stan dardization etc. The system basically meets the demands on the data processing f or very shortterm and nowcasting.
    12  Interpolating Method for Missing Data of Daily Air  Temperature and Its Error Analysis 
    Wang Haijun Tu Shiyu Chen Zhenghong
    2008, 34(7):83-91. DOI: 10.7519/j.issn.1000-0526.2008.07.012
    [Abstract](874) [HTML](258) [PDF 572.76 K](1302)
    It is the foundation of building up a continuous meteorological datasets for int erpolating the missing meteorological record. A method of estimating missing dai ly air temperature (daily maximum, minimum and average air temperature) for several continuous months is proposed, whichis improved from the linear regression model that are usually used to interpolate the missing data for a single day or several days. A series of improvements are taken on, such as: (1)The number of n eighboring referenced meteorological stations and size of time window about sampl e data are determined by optimized method; (2)The linear regression model is set up between the station of missing data and neighboring referenced stations, and the least absolute deviation(LAD) instead of the least squareroot estimate (LS E)is treated as the object function when the model parameter is solved for higher computing efficiency and parameter stability; (3)In order to reduce extreme err or, the averaged value between LAD method and DeGaetano's standardized method is used as the final result. A lot of interpolating experiments are done with the data of Caidian Meteorology Station, Hubei Province from 1961 to 2006 and the results indicate: (1)The leas t interpolating error can be obtained when 4 neighboring referenced stations, tim e window with 8 years and 15 days is used; (2)The frequency of mean absolute err or of daily maximum, minimum and average air temperature within ±0.8℃ is 94.1% 、84.8%、96.1% respectively. The monthly average and correlation coefficient bet ween actual value and interpolated value are all over 0.886 with the significant level of 0.05 and 0.01 by ttest respectively.
    13  Character Analysis on CINRADAR Products of Strong Convection Storm Weather in Henan Province
    Niu Shuzhen Bao Xiangdong Qiao Chungui Kang Wenying
    2008, 34(7):92-100. DOI: 10.7519/j.issn.1000-0526.2008.07.013
    [Abstract](1047) [HTML](102) [PDF 2.32 M](940)
    CINRADAR Products of Puyang and Sanmenxia combined with data of satellite, radio sounding, synoptic chart and rainfall station were used to analyze the process of the strong convective weather such as thunder rain as well as local hailstone happened in the north, west and middle of Henan on June 25 ,2006. The conclusions are: (1) This strong convection storm showed that several cells for strong convection echo during different development stage consisted t o mesoβ convective echoes band namely squall line with 80~400km long, 40 km wide and in NESW direction. (2) During vigorously developing period of sev e re thunderstorm there was a thunderstorm outflow border. (3) In the low level st rong northwest air flow forced the convective echoes band to grow and form the band echoes like bow shape. (4) There was a velocity line of arc shape short ba nd medial the thunderstorm outflow border in front of the severe convective stor m, this velocity line was far away from the area of blockbuster velocity and gra dually disappeared with the outflow border away from the main body of strong con vection storm. (5) The base reflectivity, echo top and vertical integral liquid water content of different type of severe thunderstorm had distinctions during t he strong convection weather with different properties. Thunder wind with short time strong rainfall weather had the base reflectivity in the strong center of 53~63dBz, echo top of 9~14km and vertical integral liquid water content of 38~48kg/m2 in the north, while 53~65dBz base reflectivity, 11~16km echo to p and 48~63kg/m2 vertical integral liquid water content in the west and the m iddle region in Henan Province. (6) There always was mesocyclone during the vigo rously developing stage of severe thunderstorm. Mesocyclone occurred in front of severe convection cell or foregoing inflow trough scoop. These CINRADAR product s characters of severe convective storm are important reference basements in str ong conwection weather forecast and alarm.
    14  Microclimatic Characteristics under Plastic Film and  Relationship with Macroclimate
    Liu Kequn Li Mingfeng Yang Wengang
    2008, 34(7):101-107. DOI: 10.7519/j.issn.1000-0526.2008.07.014
    [Abstract](679) [HTML](137) [PDF 1.22 M](1166)
    In order to improve the meteorological service on using of plastic fil m house, some contrast observations on hourly ground temperature and air tempera ture between inside and outside plastic film house were fulfilled in Wuhan, Chin a. Based on the observation, the microclimate characteristic under plastic film was analyzed and some equations about the air temperature and ground temperature under plastic film and various weather conditions were established by using cor relation analysis and stepwise regression analysis. The analyzed results indicat ed that the daily maximum temperature under plastic film or double-layer film wa s correspondingly higher by about 20℃ or 24℃ than that outside in the daylight in clear days. The averaged temperature underplastic film or doublelayer film was correspondingly higher by 0.8~3.5℃ or 3.5~6.5℃ in the nighttime. Becaus e the daily range of temperature change could be about 30~35℃ in clear days, s o that a high temperature damage and a low temperature damage should be both pre vented. Correlation analysis showed that the air temperature under plastic film was highly related to air temperature and solar altitude. The air temperature at night and the ground temperature of 0~10 cm soil layer were also highly relat ed to air temperature. As a result, some equations about the air temperature and the ground temperature under plastic film were established, which can be used t o derive and predict the hourly air temperature and ground temperature accuratel y. These equations can be utilized for the vegetable production meteorological s ervices under plastic film conditions.
    15  Study on the Method of Automatic Selection of Seeding  Areas for Weather Modification
    Huang Yimei Zhou Yuquan Liu Jinhua Li Tielin
    2008, 34(7):108-113. DOI: 10.7519/j.issn.1000-0526.2008.07.015
    [Abstract](524) [HTML](89) [PDF 921.14 K](835)
    A method is offered in this study for automatic selection of seeding a reas for weather modification via computer software techniques based on various data with different resolution from radar, satellite, numerical model results an d upperair sounding etc. The method separates the whole area into several smal l square areas forming several small matrixes. By means of dealing with various d ata and analyzing the correlation between these data and certain small areas, it can be determined whether these small areas can be seeded or not. After taking all the small areas as sparse matrixes and adopting the storage mode of orthogon al chain table, all the seeding areas can be found out automatically based on t he algorithm of adjacent search. The algorithm, data and storage structures are d escribed in detail in this paper. The method makes it easy to select the seeding areas automatically with various data on the basis of computer software techniq ues. It can be applied directly into decision-making of aircraft operation and a rtillery (rocket) operation for weather modification and is important to the ope ration modernization of weather modification.

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