ISSN 1000-0526
CN 11-2282/P

Volume 38,Issue 12,2012 Table of Contents

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  • 1  Matching FY 2 Dual Satellite Infrared Cloud Top Temperatures in Typhoon Monitoring Application
    QIN Danyu LI Bo
    2012, 38(12):1449-1455. DOI: 10.7519/j.issn.1000-0526.2012.12.001
    [Abstract](1210) [HTML](108) [PDF 1.09 M](1102)
    Abstract:
    Since typhoon operational monitoring found a large difference of infrared cloud top temperatures (TBB) between geostationary FY 2D and FY 2E satellites in a region of overlap, it is necessary to find a solution to typhoon intensity estimation by using both FY 2D/E satellites. For this motivation, the cumulative distribution function (CDF) matching algorithm, which uses the 10.3-11.3 μ channel TBB of FY 2D/E, is introduced to solve the problem. Case study of typhoon Megi, which is chosen for testing the algorithm during 1030-1230 UTC 17 October 2010, shows results as below: (1) The CDF matching algorithm works well to reduce the difference of FY 2D/E TBB, and depicts more consistent distribution of the probability distribution function (PDF). When estimating typhoon intensity, the CDF matching algorithm can perform independently with satellite data before going step by step to the intensity estimation scheme. For example, the Advanced Dvorak Technique (ADT) can directly use this normalized TBB as input data without any code modification. (2) Given MTSAT TBB as reference and FY 2D/E TBB as candidates, the CDF matching algorithm provides a normalized TBB of FY 2 D/E. Therefore, the typhoon intensity estimation by FY 2 D/E TBB only can be comparative with those from MTSAT, and this algorithm can also be checked.
    2  Evaluation of the New Cross Calibrated, Multi Platform Ocean Surface Wind Fields in the East China Sea Region
    MAO Kefeng CHEN Xi LI Yan XIAO Zhongle ZHOU Kai
    2012, 38(12):1456-1463. DOI: 10.7519/j.issn.1000-0526.2012.12.002
    [Abstract](864) [HTML](104) [PDF 1.54 M](1115)
    Abstract:
    The new Cross Calibrated, Multi Platform Ocean Surface Wind Velocity (hereafter,CCMP wind) products have been introduced, and the biases of CCMP wind fields are validated and evaluated against the wind measurements from satellite altimetry and in situ buoys. Furthermore, a comparison between CCMP wind fields and ERA Interim wind fields and QuickScat/NCEP wind fields is performed. The following conclusions can be drawn. The CCMP may have a negative mean speed difference in relation to the observations, and the best performance accurately occurs in open sea areas as well as a noticeable positive difference and trend in nearshore areas. In the East China Sea region, the CCMP has smaller absolute mean square errors and relative errors from the observed data compared with the ERA Interim wind fields and QuickScat/NCEP wind fields. The results have shown that the underestimation is mostly found for low wind speeds but overestimation for high wind speeds in these three kinds of wind fields, and a significant seasonal variation is also discussed.
    3  Analysis on Interannual and Interdecadal Variability of Annual Rainfall over China During 1960—2009
    SUN Xiubo LI Qingquan WEI Min
    2012, 38(12):1464-1472. DOI: 10.7519/j.issn.1000-0526.2012.12.003
    [Abstract](1265) [HTML](314) [PDF 3.10 M](1987)
    Abstract:
    Based on the rainfall data from meteorological observation stations in China from 1960 to 2009, the multi time scale complex construction and notably regional differences of annual precipitation variability have been revealed and the precipitation changes in the future also projected according to the interdecadal period. The fluctuant energy of annual precipitation in the northern part of China is larger, and so is the contribution of interannual variation. However, the reality in the southern part of China is reverse. Unlike other regions,the interdecadal variabilities of annual precipitation in the Northeast China and Northwest China are remarkable and in the same phase. At present, the contribution of interdecadal variabilities to the annual precipitation in Northeast China, Northwest China, South China, Tibetan Plateau, and Southwest is in decreasing phase, and tends to keep on going down in the future 5-10 years. However it is in the ascendant phase and tends to keep on rising in the future 5-10 years in the middle and lower reaches of the Yangtze River.
    4  The Contrastive Research on Environmental Conditions for Tornadic and Nontornadic Severe Convective Weather Under Ahead of Trough Pattern During Summer in Anhui Province
    WANG Yi ZHENG Yuanyuan ZHANG Xiaomei HAO Ying CAO Weiwei
    2012, 38(12):1473-1481. DOI: 10.7519/j.issn.1000-0526.2012.12.004
    [Abstract](1404) [HTML](63) [PDF 4.37 M](1091)
    Abstract:
    Based on NCEP (1°×1°) reanalysis data, the large sale circulation features as well as thermal and dynamic conditions for two types (5 cases for each type) of severe convective weathers under ahead of trough pattern during summer in Anhui Province are analyzed. The results show that: the nontornadic type mainly causes strong wind and short time heavy rainfall which is characterized by deep upper trough. However, the tornado is usually triggered by short wave trough with the low level jet which causes strong vertical wind shear. By comparing the composite thermal and dynamic parameters, it is demonstrated that the moisture condition is good for both types of severe convective weathers and the average precipitable water during summer is above 55 mm. However, the vertical wind shear at middle to low levels is very strong when tornado occurs and the 0-1 km vertical wind shear is about 3 times higher than that of nontornadic type. Because of larger vertical wind shear, the storm relative helicity (SRH) of tornadic type is stronger than that of nontornadic type. According to the thermal and dynamic conditions,the CAPE of tornadic type is not very large while the energy helicity is large and significant differences are found in storm relative helicity. Therefore, more attention should be paid to the vertical wind shear and SRH in forecasting the tornado under ahead of trough pattern.
    5  Comparative Analysis of Two Abrupt Heavy Rain Processes in Sichuan Basin in July 2011
    XIAO Dixiang YANG Kangquan QI Shengxiu
    2012, 38(12):1482-1491. DOI: 10.7519/j.issn.1000-0526.2012.12.005
    [Abstract](2759) [HTML](128) [PDF 10.45 M](37032)
    Abstract:
    By using the conventional meteorological data, Doppler radar data and NCEP/NCAR reanalysis data, the characteristics of Doppler radar’s reflectivity, environmental condition and trigger mechanism of the heavy rain are analyzed and compared between two abrupt heavy rain processes occurring in Sichuan Basin on 3 July (7.3) and 23 July (7.23) 2011. The results show that: the “7.3” heavy rain happened under a typical circulation background, and moisture transporting to the heavy rain area from the South China Sea was smoothly, thus the heavy rainfall maintained so long, but the “7.23” heavy rain occurred behind the upper cold vortex, and convective unstable energy was abundant and vertical wind shear was strong, thus this heavy rain process happened with hail and thunderstorm weather accompanied, its radar reflectivity was 5 dBz stronger than “7.3” case and had the characteristics of severe storms such as the low level weak reflectivity and the upper echo overhang. As a whole, the non equilibrium force is contributed to the occurrence of heavy rain and it is the excited mechanism of the two heavy rainfalls, and the change of the divergence evolvement is consistent with the strength and the position of the heavy rain which would happen 6 hours later.
    6  The Research of Extreme Forecast Index Based on the T213 Ensemble Forecast and the Experiment in Predicting Temperature
    XIA Fan CHEN Jing
    2012, 38(12):1492-1501. DOI: 10.7519/j.issn.1000-0526.2012.12.006
    [Abstract](1410) [HTML](75) [PDF 2.51 M](1250)
    Abstract:
    Based on the T213 global ensemble prediction system (EPS), a new ensemble forecast product——extreme forecast index (EFI), which combines the cumulative distribution functions (CDF) derived from climate and the EPS forecast, is designed. EFI is an index which can measure the continuous differences between the climate CDF and the EPS forecast CDF. When the EFI gets close to 1 or -1, extreme weather is likely to occur. Because EFI is calculated by both climate CDF and the EPS forecast CDF, then there is negative deviation in T213 EPS forecast. In order to ensure the result of the EFI is unaffected by the model error, we choose the T213 EPS model data to form the climate CDF. Next take the 2 m temperature for example, we use EFI3 to forecast the extreme low temperature in January 2008. The results show when the threshold of EFI3 that gives extreme low temperature signal is set to -0.3, most areas of extreme low temperature can be predicted on EFI3 map in 3 to 5 days in advance. We should note that the areas of extreme low temperature do not agree very well with where the EFI3 signals the extreme low temperature. It may be there are some deficiencies in the present formula of EFI3 and the EFI3 is less sensitive to extreme value of the EPS forecast. Later, a relative operating characteristic (ROC) curve is used to verify EFI3. In all three leading times shows that the averaged ROC curves valid for 2 m temperature EFI3 during 25—29 January 2008 are above the diagonal, the areas of the averaged ROC of three leading times are 0.680, 0.657, and 0.542, respectively. This means that the EFI3 is skillful in forecasting the extreme low temperature, with the leading time growing, the EFI3 is less skillful. Finally, another model climate cumulative distribution function is used to generate the EFI3 and a comparison of skill derived from two kinds of EFI3 is presented. The results show that the skill of EFI3 generated by the former model climate is slightly higher than that of EFI3 generated by the latter model climate. The reason may be that the initial field of the former model climate data is derived from the same as similation scheme while the initial field of the latter model climate data is derived from two kinds of schemes. Therefore the more consistent the model data are, the more equitable the cumulative probability distribution of model climate is. We need not to collect much model data if they be not consistent.
    7  A Study on Climatic Characters in High Frequency Period of Thunderstorm in Jiangmen of Guangdong Province
    LIN Zhuohong LIANG Minyan LIANG Jun LU Zi’an HUANG Jiayou
    2012, 38(12):1502-1507. DOI: 10.7519/j.issn.1000-0526.2012.12.007
    [Abstract](930) [HTML](47) [PDF 540.06 K](1039)
    Abstract:
    The data of daily thunderstorm in Jiangmen City during 1961-2010 and the other twenty cities of Guangdong Province during 1971-2010 are used in the study of the high frequency period of thunderstorm, through the method of frequency analysis and the principal component analysis (PCA). The results show that, the climate characteristics of thunderstorms in Jiangmen City have the high correlation with the other cities of Guangdong Province, and the thunderstorm’s climate law is of the very strong representative in Guangdong area. The high frequency period of the thunderstorm is concentrated in the April-September period. Furthermore, it can be divided into the early phase (April-June period) and the later phase (August-September period), and July is a transition period. The climate change trend of the early phase high frequency thunderstorm is dropping first and then rising, with the abrupt change year being 1983. It is corresponding to the abrupt change of the atmospheric circulation in the westerly zone at the beginning of 1980s. Analysis of pentad scale reveals that the abrupt change occurs at the fourth pentad in May, just the South China Sea summer wind outbreak period.
    8  The Application of Dynamical Statistical Method to 24 h Thunderstorm Forecast
    ZENG Shuling GONG Chongshui ZHAO Zhongjun LI Xu ZHOU Ganlin WANG Shigong SHANG Kezheng
    2012, 38(12):1508-1514. DOI: 10.7519/j.issn.1000-0526.2012.12.008
    [Abstract](1574) [HTML](68) [PDF 1.17 M](1113)
    Abstract:
    Based on the T213 numerical forecast products and many convective parameters calculated, the 24 h thunderstorm potential prediction formulas are set up for 690 national meteorological stations from April to September by using event probability regression method. At the same time based on the TS score maximum principle, the critical probability of occurrence of thunderstorm forecast is defined and the forecasts for April-September 2010 are focussed. The results show that, (1) the convective parameters based on T213 output product calculation have clearly physical meaning, and are highly related with the occurrence of thunderstorms, making significant contributions to the forecast formulas. (2) Thunderstorm potential prediction formulas are stronger indicators to regional forecasts of thunderstorms, especially to lightning striking areas. (3) The average TS score for 690 stations is 0.24.
    9  Research on Lightning Forecast at Yangkou Harbor Based on Convective Indexes
    FENG Minxue ZHOU Junchi ZENG Mingjian JIAO Xue WANG Hongsheng XU Xiaochuan GE Lili ZHUANG Zhifu
    2012, 38(12):1515-1522. DOI: 10.7519/j.issn.1000-0526.2012.12.009
    [Abstract](939) [HTML](64) [PDF 1.01 M](1012)
    Abstract:
    This paper analyzed statistical characteristics of 22 convective indexes in the 1645 samples from April to September, 2001-2009 at Yangkou Harbor and their correlation with lightning activities. The results have shown the monthly variations and different coefficients of the indexes, and then the elimination and forecasting equations were set up by means of bi level logistic regression using the multiple thresholds of indexes pw, SI, TT, JI for elimination and those of SSI, tcl_t, dt_58 for prediction with consideration of monthly diversity of each index which is in close correlation with lightning activities. The fitting test has confirmed good forecasting effects of the equations above.
    10  Climate Characteristics of Snowfall Day Numbers in Ningxia and Structure of Atmospheric Circulation
    DING Yonghong FENG Jianmin MA Shaiyan ZHENG Guangfen
    2012, 38(12):1523-1531. DOI: 10.7519/j.issn.1000-0526.2012.12.010
    [Abstract](927) [HTML](64) [PDF 1.15 M](1033)
    Abstract:
    Conventional observed data and the characteristic quantities of the atmospheric circulation were used to analyze the climate characteristics of snowfall day numbers in Ningxia and the affecting atmospheric circulation during the period of 1961 to 2010 by the methods of the statistic analysis, correlation analysis, and maximum entropy spectrum. The results have shown 〖JP2〗that the snowfall day numbers of each grade occurring in Ningxia have two extreme values which appear in spring and autumn. In winter, the heavier the snowfall, the lower the frequency. The geographical distribution of snowfall day numbers in different seasons is relatively consistent and increases obviously from north to south in Ningxia. High frequency centers have a strong correlation with terrain features. The frequency of non sustained 1 d snowfall is higher, and the lasted time decreases with the increasing of snowfall grades. The total day numbers of snowfall have decreased, the contributions of light snow, heavy snow and snowstorms have reduced, however, moderate snow has the opposite trend. Different grades of snowfall have different variations of short, medium and long period. Polar vortex in the Northern Hemisphere, index of the Tibetan Plateau, European Atlantic pattern and Eurasian circulation (Asia circulation) are the main atmospheric circulation systems influencing snowfall day numbers in Ningxia. The characteristic quantities of atmospheric circulation significantly correlated with snow frequency in Ningxia are season variational, so are the characteristics of atmospheric circulation. However, the affecting mechanism is the same, supplying the cold air and water vapor.
    11  Station Relocation Influence on Homogeneity of Temperature Series over Shaanxi Province and Deviation Correction
    WEI Na SUN Xian JIANG Chuangye CHENG Xiaoxia
    2012, 38(12):1532-1537. DOI: 10.7519/j.issn.1000-0526.2012.12.011
    [Abstract](897) [HTML](48) [PDF 739.22 K](951)
    Abstract:
    By the method of two phase regression (TPR), using temperature dataset and the information of the meteorological station’s historical evolution from 1961 to 2008, the temperature series of 74 stations in Shaanxi Province were detected and adjusted. The results have shown that: station relocation has influence on the homogeneity of temperature series in Shaanxi Province; there are few station relocations in the northern Shaanxi and more in central and southern Shaanxi; the temperature series at 24 stations are apparently inhomogeneous because of station relocation, and among them the temperature series at 12 stations are adjusted. This work makes the temperature series as homogeneous as possible over Shaanxi Province.
    12  The Backward Trajectory Simulation of the Planthopper During Migratory Peak in Hubei Province
    WAN Suqin REN Yongjian LIU Zhixiong ZHOU Guozhen GAO Zhengxu DENG Huan DENG Aijuan
    2012, 38(12):1538-1545. DOI: 10.7519/j.issn.1000-0526.2012.12.012
    [Abstract](871) [HTML](165) [PDF 1.57 M](945)
    Abstract:
    Rice planthopper is one of the causes for the great reduction of the yield of rice in Hubei Province. It is a kind of typical climatical moved flying insect pest, its takeoff, flying and settlement are closely related to weather conditions. In this article, the upper air meteorological field data, and the rice planthopper monitoring data under the lamp, are used to analyze the example, using particle track and diffusion and settlement pattern HYSPLIT 4, etc. for exploring the fly path and main source of rice planthopper in Hubei Province. The main conclusions may be drawn as follows: (1) There are five paths of rice planthopper having moved in Hubei Province, i.e. the southwest path, the south path, the southeast path, the east path and the northeast path. (2) In spring and summer, the southwest path is the main path, with its proportion of 47%, followed by the south path and the southeast path. (3) In autumn, the northeast path is the main path, with its proportion of 30%, followed by the southwest path, being 23% of the total number. (4) In comparison with spring and summer, in autumn the proportion of southwest path is decreased by 24%, that of northeast path is increased by 22%, that of the east path is increased by 8%, and very few changes in the south path and southeast path. (5) The proportion of the southly path (the sum of the southwest path, the south path and the southeast path) is 80% in spring and summer, and that is 55% in autumn. Compared with spring and summer, autumn has a decrease of 25%. (6) No matter whether it is spring and summer, or autumn, the southwest path is the most impact on Hubei Province, and influence on the southern part is greater than the northern part. The influence of the northeast path in autumn is greater than that in spring and summer. The impacts of south path and southeast path on the Jianghan Plain are greater than the others. (7) In theory, the source area of rice planthopper is 19°-25°N, 90°-120°E, with an east west long axis and a north south short axis, a rectangular area of approximately 3300 km×660 km Countries Vietnam, Thailand, Myanmar, Cambodia, and Philippines are the initial sources of rice planthopper, and regions Yunnan, Guizhou, Guangdong, Guangxi, Fujian, Hunan, Jiangxi, etc., are the secondary sources or the third class insect sources. Combining the forward trajectory simulation by numerical prediction field and the comprehensive analysis of insect source and target areas, we can carrry out the planthopper moving weather forecasting, and this work still needs further developing in operational tests.
    13  Benefit Analysis and Study of Public Meteorological Services in Jiangsu Province
    YU Gengkang SHEN Shuanghe LUO Yan HUANG Liang XU Min
    2012, 38(12):1546-1553. DOI: 10.7519/j.issn.1000-0526.2012.12.013
    [Abstract](923) [HTML](53) [PDF 913.02 K](985)
    Abstract:
    In order to understand the present situation of public meteorological service in Jiangsu Province and provide scientific basis for promoting the weather service standard, a large scale scientific and systematic survey has been conducted for the public in 2010. Through collecting and analyzing the data from the social questionnaires, the following topics such as the channels of meteorological information, the public’s attention to the meteorological information, the proportion of the public’s attention to meteorological index, the public’s assessment of accuracy of weather forecasts and meteorological services and meteorological insurance were studied separately. The results showed that: (1) the main channels are TV, mobile phones and networks to getting public meteorological information in Jiangsu. (2) The daily weather forecast on future 1-3 days are more concerned by public than all of the others. (3) The percentage of respondents who think current situation of meteorological services very satisfied and satisfied and basically satisfied reaches 94.9% and the percentage of those who think weather forecast very accurate and accurate and basically accurate reaches 92.9%. In addition, the economic benefit of public meteorological service has also been evaluated in this paper by the methods of shadow price, voluntary payment and cost saving respectively. The assessment result through cost saving is relatively objective and the value of economic benefit of public meteorological services in Jiangsu Province is about 0.866 billion yuan.
    14  The Development Period Prediction of Winter Wheat Based on Climatic Suitability in North China
    LI Haoyu WANG Jianlin ZHENG Changling SONG Yingbo
    2012, 38(12):1554-1559. DOI: 10.7519/j.issn.1000-0526.2012.12.014
    [Abstract](929) [HTML](47) [PDF 999.88 K](920)
    Abstract:
    Using the data of daily highest temperature, the lowest temperature, precipitation, sunshine duration, soil moisture and winter wheat development period, agrometeorological indexes, and considering the different effects of soil moisture and precipitation on winter wheat different growth stage, the calculation method for winter wheat moisture suitability is established. And the paper further constructs a climate suitability model of winter wheat combined with the calculation methods of winter wheat moisture suitability, temperature suitability and sunshine suitability. Based on the forecasting factor of winter wheat climate suitability, the forecast model of winter wheat development period is established. The simulation results indicate that the average errors between the simulation days from models of different districts and actual days are 1-2 days, the average errors between simulation days from models of different development period and actual days are within 4 days. The forecast and test demonstrate that average errors between simulation days from models of different districts or development periods and actual days are within three days. The results show that the operational applications of these models are possible.
    15  Design and Application of Dynamic Multi Process Model for AWS Data Processing
    LIU Yuanyuan JU Ling HE Wenchun
    2012, 38(12):1560-1564. DOI: 10.7519/j.issn.1000-0526.2012.12.015
    [Abstract](903) [HTML](48) [PDF 760.70 K](950)
    Abstract:
    Because large quantities of automatic weather station (AWS) data are increasing dramatically as well as the weather forecast system and data assimilation system are developing continually, the current processing efficiency of AWS data is unable to meet the requirement of data users. Aimed at efficiency problem of AWS data, a dynamic multi process data processing model is proposed. In this model, configuration files are used to define handling scope of each process, and a process with parameter is designed to deal with the data of particular region which needs to be got efficiently. The model has been implemented in three cases such as disastrous debris flow at Zhouqu, Gansu Province on 7 August 2010. The result shows that data processing strategy can be adjusted easily in terms of important weather phenomena and data processing timeliness can be guaranteed, increasing data processing efficiency by 80%.
    16  Research on Meteorological Suitability Index for Winter Wheat Irrigation in Winter Drought Period
    LI De ZHANG Xuexian LIU Ruina
    2012, 38(12):1565-1571. DOI: 10.7519/j.issn.1000-0526.2012.12.016
    [Abstract](780) [HTML](45) [PDF 789.14 K](912)
    Abstract:
    Based on the mathematical statistics analysis on temperature changes and precipitation data in Suzhou City of Anhui Province in winter from 1955 to 2010, the study has shown that winter wheat in Suzhou always grows slowly in winter, especially under the double influences of drought and warmer winter, when irrigation is needed. According to the above results, by using Delphi technique, the three meteorological factors (precipitation, daily minimum temperature, and wind speed) are chosen, which have effects on winter irrigation, and their quantitative grades and weight coefficients affecting irrigation suitability are set up. And then, the meteorological suitability index for winter wheat irrigation in winter drought period is proposed and its computational model is built. Finally, combined with the appropriate technology of weather forecast, the study presented the weather forecast products for winter wheat irrigation in winter drought period. The case validation shows that the model has the ability to satisfy the needs of issuing the weather forecast products for farming.
    17  Prediction of Optimum Sowing Date of Winter Wheat in Jiangsu Province Based on Sea Surface Temperature and Atmospheric Circulation Characteristics
    GAO Ping ZHANG Pei XIE Xiaoping HU Luolin XIANG Ying
    2012, 38(12):1572-1578. DOI: 10.7519/j.issn.1000-0526.2012.12.017
    [Abstract](927) [HTML](49) [PDF 1.29 M](877)
    Abstract:
    Based on the analysis of temperature data from 60 meteorological stations in Jiangsu Province during the period 1961-2010 by using the Mann Kendall method, it was found out that both daily mean temperature and effective accumulative temperature during the growing period of winter wheat prior to winter have significant increasing trends in parallel with global warming. The statistical analysis on the agro meteorological records in different regions has shown that the sowing date of winter wheat is significantly correlated with the total and effective accumulative temperatures prior to the winter. The correlation between sowing date and effective accumulative temperature has passed the test at the 0.001 significance level. According to coupling between the atmosphere and oceans and the fact that the atmospheric circulation characteristics (ACC) of 500 hPa can indicate the weather patterns and control the weather conditions, a batch of effective sea surface temperature (SST) and ACC predictors of accumulative temperature prior to the winter were selected using the optimum correlation technique. These SST and ACC predictors are independent each other and have stable and significant correlations with the accumulative temperature. Then the models for predicting the accumulative temperature prior to the winter were developed. Calibrations and validations show that these developed models are able to predict the accumulative temperature prior to the winter with satisfied accuracy. They can be routinely operated to predict the accumulative temperature prior to the winter and to determine the optimum sowing date of winter wheat one to two months in advance.
    18  Analysis of the September 2012 Atmospheric Circulation and Weather
    QIAN Qifeng
    2012, 38(12):1579-1584. DOI: 10.7519/j.issn.1000-0526.2012.12.018
    [Abstract](874) [HTML](70) [PDF 2.65 M](1189)
    Abstract:
    The following are the main characteristics of the general atmospheric circulation in September 2012. The polar center over the Northern Hemisphere is a single vortex pattern and deviated to the Western Hemisphere. The circulation presents a five wave pattern in the middle high latitudes and the trough areas are over the east part of Asia, the west part of Asia, the middle part of the Pacific, the east part of North America and the west part of Europe, respectively. The intensity of the subtropical high is slightly stronger than normal years, and its western ridge spot has large variation during September. The monthly mean temperature (16.6℃) is nearly the same as the value of normal years. The mean precipitation (73.8 mm) is 13.2% more than normal (65.2 mm). There are six precipitation processes and three tropical cyclones generated in the western North Pacific with none landed in China. In this month, freezing calamity occurred in several northern provinces of China and sixteen provinces (regions, cities) suffered from strong wind and hail disasters.

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