Vol.15, NO.3, 2004

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IMPACTOF LOCAL SURFACE WINDS ON ATMOSPHERICMETHANE BACKGROUND CONCENTRATIONS AT MT.WALIGUAN
Zhou Ling xi, Wen Yupu, Li Jinlong, Tang Jie, Zhang Xiaochun
2004, 15(3): 257-265.
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Abstract:
In combination with partitioned continuous data sets of atmospheric CH4 and local surface winds corresponding to different seasons from July 1994 to December 1996, the impact of surface winds on the CH4 background concentrations at Mt. Waliguan (36° 17′N, 100° 54′E, 3816 m ASL) in the western China was studied, which is one the global atmospheric baseline monitoring stations. Results indicate that the variability in the horizontal and vertical wind speed/direction over the periods of different seasons has a distinct impact on the observed CH4 variations. Horizontal wind direction of NE—ENE—E is the major non-background section of atmospheric CH4 observation at the site. Horizontal wind speed larger than 10m/s, or calm condition, or vertical wind speed larger than±1 m/s has maximum impact on CH4 hourly mixing ratios. Statistical analysis also gives the averaged CH4 distribution and its diurnal variation pattern in different seasons during this period. By using the local surface winds outcomes as one of the data filters for the atmospheric CH4 observed concentrations at in-land plateau of China, the selection procedures of background concentrations were provided for the applications to the different purpose and requirements. The selected hourly data sets representing "baseline" conditions accounts for 50% of the raw records approximately.
RADIOMETRIC CALIBRATION ON ORBIT FOR FY-2B METEOROLOGICAL SATELLITE' S VISIBLE CHANNELS WITH THE RADIOMETRIC CALIBRATION SITE OF DUNHUANG
Rong Zhiguo, Zhang Yuxiang, Qiu Kangmu, Hu Xiuqing, Zhang Lijun
2004, 15(3): 266-272.
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Abstract:
Pre-launch calibration of the FY-2B's visible channels has much error due to the influence of stray light. The radiometric calibration on orbit for FY-2B's visible channels might be running with the radiometric calibration site of Dunhuang's Gobi. There are must calibrated the BRDF of bi-direction characteristic of Dunhuang's site, because the zenith is close to 50°. The reflectance of the Gobi, light extinction of atmosphere and radiosonde observation were measured in synchronization for FY-2B in July 2002, while the bi-direction characteristics of the site were measured. The data processed results indicate that the calibration precision are debased 20% due to influence of stray light for FY-2B's visible channels, and the output of FY-2B's visible channels is very stabilization after long stakeout. The calibration tables calibrated by the site of four visible channels were listed.
THE METHOD OF EVALUATING SUB-PIXEL SIZE AND TEMPERATUREOF FIRE SPOT IN AVHRR DATA
Liu Cheng, Li Yajun, Zhao Chang hai, Yan Hua, Zhao Hongmiao
2004, 15(3): 273-280.
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Abstract:
A method to evaluate the sub-pixel size and temperature of fire spot was presented by using the multiple infrared channel data from polar-orbiting meteorological satellite sensor under various fire spot conditions with the different infrared band data, for example, the mid-band (3.7μm) and thermal-band (11μm), or short infrared band (1.6 μm) and thermal-band (11μm). The Newton's iteration method can be used to find an accurate solution from a dual non-linear coupled equation established by the expression of mixed pixel. For the different channels in the same infrared band, the relationship, between sub-pixel size and temperature of active fire vs the brightness temperature increment of mixed pixel in 11μm channel and difference of brightness temperature increment of mixed pixel in 11μm and 12μm channel, can be established by generating a look up table, and from the table, the evaluating of sub-pixel size and temperature of fire spot can be derived from the brightness temperature of a mixed pixel.
HUAMEX RADAR DATA PROCESSINGMETHOD
Liang Haihe, Ruan Zheng, Ge Runsheng
2004, 15(3): 281-290.
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Abstract:
A method of processing weather radar data of HUAMEX was presented, and an integration application system was established, including (1) converting raw data format into united format and verifying raw data, (2) producing radar 3-D square grid and latitude-longitude grid data, (3) processing radial velocity, and (4) retrieving rain and mosaic wind filed. 2-D wind field in a hail day was retrieved, and convergence field appearing before echo zone forming was discovered. When the echo moving into convergence field, it became hail. It reveals that hail can be predicted by retrieved wind. In HUAMEX, 3-D wind field from single Doppler was retrieved, and 3-D wind mosaic map was formed by three Doppler radar data, the applications potential for understanding and employing Doppler wind was exhibited.
ASSESSING POTENTIAL PREDICTABILITY ASSOCIATED WITH BOREAL SEA ICE WITH AN AGCM
Wang Jia, Guo Yufu
2004, 15(3): 291-300.
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Abstract:
The potential predictability associated alone with boreal sea ice on the seasonal to intraannual scale is studied with AGCMR15L9, the atmospheric component of LASG/IAP GOALS. With the aid of the analysis variance, it is found that the predictability index, expressed as a ratio of the external variance to the total, is weak in most regions. But as far as some low level, say 1000 hPa, variables are concerned, such as atmospheric temperature and relative humidity, stronger predictability larger than 0.5 can be found in some regions where the interannual sea ice variability is great. Compared with sea surface temperature (SST) in the lower latitude, the Boreal sea ice may have an equivalent or even stronger impact on the mid-high latitude atmospheric circulation. In addition, in some regions where the local sea ice variance is great, a greater predictability in the years of large sea ice area anomalies can be achieved than the results of the total 31 years. It means that large sea ice anomalies in some specific regions may lead to great anomalies in the corresponding atmospheric circulation.
CHANGE IN GROWING SEASON OVER CHINA:1961 —2000
Xu Ming zhi, Ren Guoyu
2004, 15(3): 301-312.
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Abstract:
Using daily temperature data at 642 stations in China Mainland from 1961 to 2000, the decadal variation and change in temperature-defined growing season over the past 40 years were analyzed. The growing season increased 6.6 days in China as a whole, 10.2 days in the northern China, and 4.2 days in the southern China. The largest increase in growing season, 18.2 days for the period, occurred in the Qinghai-Xizang Plateau. The most rapid increasing of growing season was in the 1990s, and 1998 is likely to be a year with the longest growing season in past 40 years.
CLIMATIC VARIATION OFMEIYU IN THE MIDDLE-LOWER REACHES OF CHANGJIANG RIVER DURING 1885 —2000
Wei Fengying, Zhang Jing jiang
2004, 15(3): 313-321.
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Abstract:
The decadal scale variation characteristics of the Meiyu (plum rains) time series in the middle and lower reaches of the Changjiang River during 1885—2000 were investigated by using statistical technique. Including maximum entropy spectrum, cross spectrum and abrupt change analysis etc. It is found that: ①There exist a significant positive correlation between the Meiyu rainfall and Meiyu duration and the ending date of Meiyu. ② The main periodic length of Meiyu series are three years, six years and eight years, which are related to the 100 hPa geopotential height over the low latitude, tropical systems and the variation of global land temperature respectively. ③ The 6-year period of the Meiyu duration, onset date and ending date of Meiyu are controlled by the same climatic factors, but the 3-year period of the Meiyu probably are influenced by the different climatic factors. ④ Six different climate phases are identified in the Meiyu time series for recent 116 years (1885—2000).
OPTIMIZATION AND PARALLEL OF TYPHOON TRACK PREDICTION MODEL IN NMC AND TRACK ERROR ANALYSES
Ma Suhong, Qu Anxiang, Zhang Yi
2004, 15(3): 322-328.
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Abstract:
The Model for Typhoon Track Prediction (MTTP) on Cray 92 in National Meteorological Center (NMC) was optimized and paralleled through data paralleling and message passing on Shenwei (SW) super computer made in China and the running time could meet the requirement of operational running. The new typhoon track prediction system was set up based on this model and SW computer was put into real time running on 30 June 2002. The initial condition and lateral boundary were updated from T106L19 to T213L31. The track results show that the track forecasts from the new system are better than that from the old system (the system on Cray 92) on the whole. But the performance is different for different types of tracks: The results from the SW system are better for the northeast recurving typhoons and worse for west and northwest moving typhoons.
IMPROVEMENT AND APPLICATION OF CAPPS LOCALIZED IN TAIYUAN CITY
Miao Aimei, Li Taoguang, Zhang Hongyu, He Hanyuan, Luo Linan
2004, 15(3): 329-335.
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Abstract:
Based on the analysis of the main reasons that lead to the error problems appearing in the operation of the CAPPS Model System in Taiyuan City, the varying of the orographic background fields were discussed. According to different seasons and different synoptic situations, the accommodation function of complex error coefficient and raising dust coefficient is added to this model system and various numerical simulation experiments are made. The result shows that through the simulation experiment schemes based on error analysis, the correlation coefficients of the prediction and the observation of main pollutants: SO2, NOx and PM10 are increased to 0.96, 0.91 and 0.89. The forecast accuracy of the CAPPS Model System localized into an operation numerical model system in Taiyuan City can be reached to 90%.
EFFECT OF SEASONAL CIRCUMFLUENCE DRESSAL IN SPRING AND AUTUMN ON SUMMER FLOOD IN HUBEI PROVINCE
Zhou Yuehua, Xiang Hua
2004, 15(3): 336-344.
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Abstract:
Flood is the major meteorological disaster of Hubei Province. Nine lasting torrential rain flood year are defined after analysis on climatic characteristics of precipitation in the flood period in Hubei Province, which occur mainly in years when there is a southern or middle raintype in the eastern China. The correlation between the rainfall in the eastern Hubei in the flood period and 500 hPa circumfluence elevation field is analyzed. It concludes that abnormal redressal of circumfluence in spring and autumn is an important prophase factor in forecasting rainfall in the flood period in Hubei Province. A departure composing demonstrates that, in typical flood year and draught year, the departure from average of the heights at 55°—65°N in preceding March is inverse within 130°E—120°W and 90°—10°W. The 500 hPa circumfluence fields of preceding March of the year and March, October of the year before are studied to find out some key indexes which make senses on the abnormal excessive summer rain in the Province. Then a short-term climatic forecasting model for summer flooding year in the Province is established. The model utilizes two factors to transfer serious flood as a small probability (probability=18%) occurrence into a big probability (probability=70%) occurrence, after that, a judgment is made through two steps, which demonstrates a 100% distinguishing rate for the serious flooding year in history of Hubei Province, and the test forecast for 2000—2002 accorded well with actual conditions.
A NEW METHOD FOR NON-LINEAR CLASSIFY AND NON-LINEAR REGRESSION Ⅰ :INTRODUCTION TO SUPPORT VECTOR MACHINE
Chen Yongyi, Yu Xiaoding, Gao Xuehao, Feng Hanzhong
2004, 15(3): 345-354.
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Abstract:
A brief introduction to an increasingly popular machine learning technique, SVM (support vector machine) is presented for solving nonlinear classification and regression problems. Properties of SVM are discussed together with potentials of applying SVM to numerical weather forecast. SVM is a novel learning method that has solid theoretical basis and requires only small amount of sample. It does not rely on probability measures and Law of Large Numbers, hence is different from many other statistical methods. In essence, SVM smartly evades the traditional inference process from induction to deduction. Instead, it employs transductive inference from training sample to predicting sample, which greatly simplifies classification and regression problems. The decision function of SVM is only determined by a few support vectors. The complexity of computation relates to the number of support vectors rather than the dimension of the sample space. Thus, to some degree, SVM avoids the "curse of dimensionallty".
A NEW METHOD FOR NON-LINEAR CLASSIFY AND NON-LINEAR REGRESSION Ⅱ :APPLICATION OF SUPPORT VECTOR MACHINE TO WEATHER FORECAST
Feng Hanzhong, Chen Yongyi
2004, 15(3): 355-365.
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Abstract:
A novel weather forecast method using the support vector machine (SVM) is introduced. Both of SVM model of area rainfall categorical forecast of 15 mm excess and SVM model of single-station temperature regression in Sichuan basin are built upon ECMWF analysis fields of 500 hPa height, 850 hPa temperature, and sea level pressure from April to September through 1990—2000. Extensive experiments are performed with performances evaluated by the Threat Scores (TS) or Correlation Coefficient. Empirical results demonstrate much improved performance compared with those given by standard statistic analysis and forecast methods.
REVIEW OF DUSTSTORM WEATHER AND RESEARCH PROGRESS
Wang Wei, Fang Zongyi
2004, 15(3): 366-381.
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Abstract:
Duststorm is a weather phenomenon near the desertification area. It is formed as a result of nature factors and human activities. Nature factors include high wind, decreasing precipitation and enough sand sources. Human activities result in increasing of duststorm by decreasing vegetation covers in semiarid and arid region during the economical development. The main aspect of the paper is influences of the nature factors, which includes seven aspect of duststorm research. For example, sand distributions and path of duststorm in East-Asia, duststorm periodic variation, the influences of climatic change, a variety of weather system of making duststorm, mechanism of dust emission, utilizing of satellite image and wind erosion model. The present main research results are introduced in detail. In addition, several problems of duststorm research are discussed.
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