Table of Content

31 October 2013, Volume 29 Issue 5 Previous Issue    Next Issue

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Analysis of heavy rain on August 9, 2011 in west of Shijiazhuang area LI Guo-cui,SUN Yun, LI Guo-ping,ZHANG Li-xia 2013, 29 (5):  1-5.  Abstract ( 577 )   PDF (1128KB) ( 483 )   Save Based on the meteorological data from a Doppler radar and intensive automatic weather stations, and the GPS precipitable water vapor data, a local heavy rain process in the west of Shijiazhuang area was analyzed. The results show that the weak shear line moving westward and stretching northward are trigger mechanism and forecasting focus of this process under high temperature and high humidity atmospheric environment. The location of shear line is its main circulation background. Atmospheric water vapor is accumulated rapidly before the severe convective weather occurs, and the curve of the GPS precipitable water vapor contents has two peaks.  The maximum peak value corresponds to the starting time of precipitation exactly, and the second one is ahead of 16 hours before the heavy rain. An echo of the strong precipitation is generated by the combined development of the main echo, the gust front and the newborn echo. The peak values of combine reflectivity (CR), vertically integrated liquid (VIL) and echo top (ET) are 61 dBz, 55 kg.m-2 and 17 km, respectively. Under the high temperature and high humidity atmospheric environment, a newborn echo, the gust front, convergence and cyclone or inversion wind area on the speed map are of indicative to the development of convective weather. Related Articles | Metrics

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Analysis of heavy rain on July 30, 2011 in Liaoning province YAN Qi,SUN Xin,QIAO Xiao-shi,ZHAO Ming,CUI Jin ,LI Shuang 2013, 29 (5):  6-11.  Abstract ( 559 )   PDF (2964KB) ( 551 )   Save  Based on the conventionally meteorological observation data, satellite cloud images, Doppler weather radar echo data, the data from automatic weather stations and the NCEP/NCAR reanalyzed data (1°×1°), a short-time rainstorm process on July 30, 2011 in Liaoning province was analyzed. The results show that upper trough at 500 hPa and shear line at 850 hPa form the forward-titling trough which provides favorable instability conditions for generation of rainstorm. The mesoscale analysis suggests that the temporal and spatial variation of precipitation is significant. The intensive contour zone of TBB and the location of the overshooting cloud of convective systems are indicative to the falling area of rainfall. The intensity of radar echo generally reaches 65 dBz during the strong rainfall and there exists the inversion wind area, and a couple of positive and negative winds. The mesoscale and microscale strong convective characteristics are significant. The dense area of isotherm and the surface shear line (or the mesoscale low pressure) trigger together mesoscale rain cluster, and the intensity of rainfall strengthens sharply. The dynamic mechanism of shear line formation is diagnosed by a vorticity equation, and it suggests that when the positive vorticity variability increases, shear line moves to its large value area and generates the dynamic convergence lifting conditions. Divergence contributes greatly to vorticity variability, and strong convergence is one of the dynamic mechanisms of shear line formation in low level. Related Articles | Metrics

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Meteorological characteristics of a continuous haze process in Beijing TANG Yi-xi ,ZHANG Xiao-ling,XIONG Ya-jun,ZHAO Xiu-juan,FAN Guang-zhou,WANG Jing-li 2013, 29 (5):  12-19.  Abstract ( 820 )   PDF (1486KB) ( 625 )   Save  A heavy haze event occurred in the plain area of Beijing from January 10 to 14, 2013. During this period, the visibility was always less than 2 km; air pollution reached and exceeded severe level; the primary pollutant is PM2.5. The process was synthetically analyzed based on the synoptic situation, the conventional and intensive observational data from weather stations and the observational PM2.5 concentration from the urban and rural station. The results show that there exists relatively straight zonal circulation with west-northwest air current control and without obviously southward cold air in upper level over Beijing during this haze process. It is weak pressure system on the ground which is not favorable to diffusion and transportation of pollutants. The atmospheric stratification is stable; wind speed is low (the daily mean wind speed is less than 2 m·s-1); relative humidity (RH) is high (the mean daily RH is more than 70%); the frequency of temperature inversion is high and its intensity is strong. Thus, the ability of vertical and horizontal diffusion of air pollutants within the boundary layer is very weak. Because of the heavy emission intensity, the high humidity and stable weather background in Beijing-Tianjin-Hebei region, the concentration of pollutants are influenced by the complex terrain and local circulation. Combined actions of local pollutants emission and regional transportation as well as the physical or chemical reactions of fine particle PM 2.5 make the pollutants concentration increasing sharply and maintaining with a high concentration in urban and plain areas of Beijing. The high concentration of PM 2.5 has a significant impact on light scattering extinction, which results in low visibility and severe haze weather. Related Articles | Metrics

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Analysis of a continuously heavy fog process in Shandong province on December 3 to 7, 2011 WANG Xi-lei,MENG Xian-gui,ZHAO Jing-feng 2013, 29 (5):  20-25.  Abstract ( 525 )   PDF (1522KB) ( 301 )   Save  Based on the conventionally observational data and the NCEP reanalysis data from December 1 to 7, 2011, the synoptic background, temperature and humidity conditions, atmospheric stratification feature of a wide area of continuously heavy fog event in Shandong province were analyzed by a diagnosis analysis method. The results show that this event occurs under stable stratification, flat general circulation at high level and mid-latitude. There is a large scale of high pressure area from east Siberia to south China, and Shandong province is located in the middle of high pressure. The synoptic situation is stable. Top of fog image is smooth and there is a clear edge on the high resolution visible cloud image, while there is not distinct feature on the infrared cloud image. The weak east to northeast wind (wind speed is less than 2 m·s-1) near the surface is favorable to advection transportation of warm and humid air flow from the ocean, and it is also favorable factors for the formation of colder underlying surface. Turbulence is vigorous in boundary layer that brings considerable vertical transportation of turbulence kinetic energy. There is a significantly inversion layer at low level in the initial period of the fog process. It is clear and radiative cooling is obvious, so the radiation fog is dominant at the early period. However, it is advection fog at the middle and late period because warm and humid air blows to colder underlying surface. Related Articles | Metrics

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Temporal and spatial characteristics of summer near-surface air temperature in Beijing central business district ZHANG Ben-zhi ,REN Guo-yu,ZHANG Zi-yue,LI Yan 2013, 29 (5):  26-34.  Abstract ( 539 )   PDF (2090KB) ( 366 )   Save Based on the air temperature data from 31 automatic weather stations (AWS) during June to August of 2012, the temporal and spatial characteristics of summer near-surface air temperature and the possibly controlling factors in the Beijing central business district (CBD) were analyzed. Air temperature from the AWS of CBD and from the national meteorological station at Chaoyang district of Beijing was compared. The results show that the spatial distribution of the near-surface air temperature in the CBD is directly affected by the difference of underlying surface types and anthropogenic heating. The mean monthly air temperature in summer of 2012 in the densely populated, high-rising buildings and asphalt surface areas is about 1.0 ℃ higher than that in the green coverage area in the CBD. Anthropogenic heat emission due to human activity and use of vehicles at night is the main reasons for large spatial differences of the urban heating environment, while its difference in the daytime is relatively small. The daily and weekly variations of air temperature are significant in the CBD and in Chaoyang weather station. The air temperature difference between them is a positive value regardless in the daytime or at night. Surface air temperature is higher in the CBD than in Chaoyang weather station in the daytime and at night, which suggests an extra urban heat island (EUHI) effect in the Beijing CBD. The daily variations of urban heat island and EUHI are similar. Under different weather conditions, intensity of EUHI effect is different. The EUHI effect is strong in a sunny day with breeze and partly cloud, especially at night, while is weak in a cloudy day with high humidity; it is the weakest in a rainy day. Sunshine and solar radiation is important to the EUHI. The spatial distribution of EUHI in the CBD is similar under the different weather conditions. Related Articles | Metrics

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Analysis of easterly wind during snow within the 250 m tower layer in western coast of the Bohai Sea SUN Mi-na.YI Xiao-yuan.YAN Zhi-chao.LI Qing-chun 2013, 29 (5):  35-42.  Abstract ( 551 )   PDF (2534KB) ( 393 )   Save Based on the observational data collected from the tower in Tianjin, intensive automatic weather stations and the conventionally meteorological data, the characteristics of the easterly wind were analyzed before and after four snow events. The results show that the four events are all backflow-type snow. The water vapor source is provided by southwest air flow and low level easterly wind. Surface easterly wind is ahead of 8 hours before snowfall whose wind speed is about 2 m·s-1 and is up to 12m·s-1 at the 220 m height level. Easterly or southeasterly wind caused by northward low-pressure system from the south is relatively wet, while easterly or northeasterly wind caused by southward cold high pressure from the northeast is relatively dry. During the maximum snowfall period, the easterly wind at the tower layer increases significantly, while the ground wind speed changes insignificantly. Related Articles | Metrics

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The dual-resolution approach for ensemble Kalman filter and simulation tests SUN Long-yu,QIAO Xiao-shi,JIANG Da-kai,CHEN Li-qiang,WU Man-li,LIANG Han 2013, 29 (5):  43-48.  Abstract ( 614 )   PDF (994KB) ( 305 )   Save  A huge computational cost in the ensemble forecast is primary challenge for the ensemble Kalman filter application into high-resolution mesoscale models under an operational environment. The dual-resolution ensemble Kalman filter algorithm could significantly save the time of computation because its covariance matrix of errors is provided by a group of low resolution samples. Using the simulated data, the dual-resolution ensemble Kalman filter algorithm was tested and it was compared with the high-resolution ensemble Kalman filter method. The results show that in the first assimilation cycle, the center locations of high and low values of simulated increments of horizontal wind field and disturbed potential temperature field at 500 hPa and their observed increment fields are same for both methods, and the structures are close to the observational increment field. The increment value from the approach of the high resolution ensemble Kalman filter is closer to the observational value than that from the dual-resolution method. In the forecast-assimilation cycle test, the root mean square errors from the two methods decrease generally with the increase of assimilation number and it suggests that both methods have compatible assimilation abilities. The result from the dual-resolution is poorer than that of the high resolution method, but the running time of the former is only 1/6 of that of the latter. Related Articles | Metrics

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Discrimination index of precipitation phase state and its verification in Beijing YOU Feng-chun, GUO Li-xia, SHI Yin-shan,ZENG Jian 2013, 29 (5):  49-54.  Abstract ( 554 )   PDF (615KB) ( 545 )   Save  To improve forecast accuracy of precipitation phase state, the variation of sleet day was analyzed based on the daily meteorological data from 20:00 to 20:00 during January of 1951 to April of 2011 from the southern suburb observatory station of Beijing as a representative station. The cases of rain, sleet, snow were selected at 08:00 and 20:00 from October to April during 2000 to 2011, and the effects of conventionally meteorological elements in each layer on precipitation phase state were analyzed according to their corresponding ground and upper meteorological data, and the main influencing factors and the discrimination index of precipitation phase state were found out. A forecast equation of precipitation phase state was established by a multiple regression method. The equation and the corresponding discrimination index were tested. The results indicate that the averaged temperature, dew-point values from rain and snow at lower layer (from the ground to 850 hPa) differ significantly. Both differences decrease with the increase of height. The mean dew-point difference of temperature in each layer is not significant and hardly to use for distinguishing the precipitation phase state. By the test of precipitation phase state from November of 2011 to March of 2012, it shows that the discrimination index and the forecast equation could provide references for forecast of precipitation phase state. Related Articles | Metrics

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Characteristics of winter rainfall in eastern China based on grid data LIAO Rong-wei,SHEN Yan,ZHANG Dong-bin 2013, 29 (5):  55-62.  Abstract ( 649 )   PDF (2417KB) ( 434 )   Save Using the monthly rainfall data from 2419 weather stations with 0.5°×0.5° resolution and the NCAR/ NCEP reanalysis data from 1958 to 2007 in the Eastern China, the variations of winter rainfall and the corresponding circulation were analyzed. The results indicate that there is a climatic trend for rainfall in the recent 50 years. The water vapor resource is more abundant in 1990s, while it is contrary in 1960s and 1970s, which could reveal the intensity of water vapor transport in the East Asia and how much water vapor is transported from ocean to island in China. The difference between years of abundant and scarcity rainfall could reach 40 mm. The correlation coefficient between rainfall and water vapor budget is 0.605. The regression coefficient between water budget and rainfall suggests that the anomalous large value is located in the south of the Yangtze River basin. Winter wind is weak for the years with abundant rainfall; it is the abnormal circulation with cyclone type in lower and upper troposphere; the abnormal southward wind prevails in the low level; the abnormal warm and wet water vapor from the Bay of Bengal and the South China Sea is transported into the eastern China. The sea surface temperature is high in the eastern China and the vertical ascending action strengths, which is favorable to the increase of water vapor, so rainfall increases. Related Articles | Metrics

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Temporal and spatial distribution of rainstorm days from 1961 to 2009 in Yili area ZHU Xiao-mei, ZHU Yi 2013, 29 (5):  63-68.  Abstract ( 636 )   PDF (951KB) ( 515 )   Save Based on the daily precipitation data from 10 automatic weather stations from 1961 to 2009 in Yili area, the temporal and spatial distribution of the inter-decadal, annual, monthly rainstorm days and variation of their cycles were analyzed using methods of a linear trend, a cumulative anomaly, an M-K test, and a cycle analysis. The results showed that the rainstorm days are in an increasing trend in the recent 49 years in Yili area, and its linear trend increases 0.107 days every decade. Rainstorm occurs mainly during May to July which accounts for 73.2 % of the total, especially in June, then in July. The year with the abnormal fewer rainstorm day is 1995, while the years with the abnormal more rainstorm days include 1996, 1999, 2002, 2003 and 2007. The rainstorm days gradually increase from west to east and from north to south. There is a 2.8 years cycle for the annual rainstorm days. Related Articles | Metrics

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Climatic characteristic of rainstorm and its trend in Baoding of Hebei province HUANG He,YU Lei, DING Zheng-zhen, WANG Zhi-chao, MA Hong-qing ,YANG Chao 2013, 29 (5):  69-73.  Abstract ( 841 )   PDF (884KB) ( 474 )   Save Based on the daily precipitation data from 19 meteorological stations in Baoding during 1974 to 2012, the spatial and temporal distribution characteristics of rainstorm and its variation were analyzed using methods of a linear trend analysis, a Mann-Kendall test, a wavelet analysis and a power spectrum. The results show that more rainstorms occur in the north and less in the south and most are in the northeast region. Rainstorm usually appears in the flood season (June to August), especially in the main flood season (July to August). Rainstorm frequency increases slowly since the middle ten days of May, then increases sharply in the last ten days of June, and it reaches the peak value in the last ten days of July. The annual rainstorm frequency is in a decreasing trend in the recent 39 years, especially in August. An abrupt change of rainstorm frequency from less to more during the main flood season occurs in 1980 s, while it is in the late of 1990 s that the rainstorm frequency changes from more to less. Related Articles | Metrics

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Adjustment of upper air temperature based on inhomogeneity of day-night temperature difference series WU Hui ,ZHAI Pan-mao,LIN Jian-xing 2013, 29 (5):  74-80.  Abstract ( 394 )   PDF (913KB) ( 446 )   Save Based on the daily temperature data from 75 radiosonde stations in the eastern China at 08:00 and 20:00 during 1958 to 2005 and the corresponding metadata, homogeneity of temperature at different levels was tested and adjusted using  methods of a temperature difference between daytime and nighttime and a two-phase linear regression. The annual trends of the observed and revised temperature at 49 stations were analyzed by selecting data using 30 % maximum missing rate as a standard. The results indicate that inhomogeneity of temperature is caused by changes of radiosonde instrument and radiation correction method in upper level over the eastern China. The credible breakpoints for inhomogeneity occur in 1966 and 2000, especially in 1996. The most obvious inhomogeneity appears at 100 hPa. Compared with the original temperature series, warming trend of temperature below 500 hPa weakens from 1958 to 2005, so is its decreasing trend from 200 hPa to 50 hPa and the ratio is 0.04-0.08 ℃ every decade. Troposphere temperature increases and lower stratosphere temperature decreases significantly since 1979. Therefore, temperature discrepancy of adjusted and original time series during 1958 to 2005 is small compared with that during 1958 to 2005. Related Articles | Metrics

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Data reconstruction of monthly soil relative humidity during spring sowing period in Liaoning province from 1981 to 2012 LI Yu-hong, LI Ji,WANG Xiao-tao,LI Jing,HUANG Yan,ZHANG Xiao-yue, WANG Ying,LIU Jie 2013, 29 (5):  81-85.  Abstract ( 547 )   PDF (580KB) ( 478 )   Save There are some problems of missing data or discontinuity in long-time series of soil relative humidity data obtained from the observational stations during the spring sowing in Liaoning province. Using the soil relative humidity records from Haicheng observational station as a case study, the relationship between soil relative humidity (0-20 cm) and meteorological factors, relative humidity from the surrounding weather stations was analyzed. A statistical regression model for the construction of monthly soil relative humidity during the spring sowing period was established, and missing soil relative humidity data were simulated using the above method. Meanwhile, the monthly soil relative humidity data during the spring sowing period from 1981 to 2012 in 20 observational stations in Liaoning province were rebuilt. The results indicate that soil relative humidity in Haicheng observational station is significantly correlated with local rainfall and the last precipitation before freezing up in autumn, and the multiple correlation coefficients are over 0.60 and 0.30, respectively. The correlation coefficient of soil relative humidity between Haicheng and Benxi observational stations is over 0.40. A regression model on soil relative humidity in April and May is established by the above three elements, and its multiple correlation coefficients are 0.79 and 0.77, respectively. The mean relative error is 2.6 % between simulated and observational values. The multiple correlation coefficient of the model established by the other loss data in Liaoning province is over 0.50, and the fitting precision is higher than 85 %. The mean relative error is within 15% between simulated and observed values. The rebuilding of monthly soil relative humidity during spring sowing for 20 stations in Liaoning province during 1981 to 2012 is reasonable. Related Articles | Metrics

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Study on forecast element of heat stroke weather grade based on hotness index in Hebei province CHEN Jing, HAN Jun-cai, ZHANG Su-guo, YAN Fang ,YANG Peng 2013, 29 (5):  86-91.  Abstract ( 575 )   PDF (497KB) ( 431 )   Save  In order to forecast heat stroke weather effectively, the heat stroke cases and meteorological conditions were analyzed in Hebei province. The critical index of the daily maximum air temperature which may cause heat stroke was determined, and a formula of hotness index was established based on temperature and humidity. The heat stroke weather grades were divided into four levels by the daily maximum air temperature, hotness index and its duration. According to the effect of heat stroke on human health, some suggestions for different grades were given. Furthermore, the rationality of grade division was tested by meteorological conditions, the heat stroke cases and application of graded index. The results show the forecast index of heat stroke grades is consistent with summer climate distribution characteristics in Hebei province. More than 97% of heat stroke cases occur in the first or second grades of heat stroke. The forecast accuracy rate of grade index reaches 81.2 %. The index has well indicative to forecast heat stroke weather and prevent heat stroke effectively. Related Articles | Metrics

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Sand dust weather and its variation in China based on PLAM index tracking method WANG Ji-zhi ,YANG Yuan-qin ,WANG Ya-qiang ,ZHANG Guang-zh 2013, 29 (5):  92-97.  Abstract ( 697 )   PDF (911KB) ( 799 )   Save Using the meteorological observational data from automatic weather stations and intensive weather stations, the radiosonde data, the weather charts and so on, the tracking analysis of sand-dust weather was developed by the PLAM (parameters of air quality and meteorology) index based on the sand dust deposited PSCF (potential source contribution function) method. A spline trend analysis method was also used to investigate the strength variability of the SDS systems. The distributions of sand dust weather from 1980 to 2011 in North-East Asia region were presented. The annual variation of sand dust weather process was studied using a spline trend analysis method. The results show that the annual intensity variation of sand dust weather process is not in a monotonously decreasing trend and it has a wave change status with both a historical persistence and abrupt transition. Meanwhile, it has a 10 years high-low oscillation. Related Articles | Metrics

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The characteristics of low visibility weather and its impacting factors over the coastal city group in Fujian province ZHENG Qiu-ping,LIN Chang-cheng,WANG Hong,CHEN Xiao-qiu, LIU Hong-nian 2013, 29 (5):  98-105.  Abstract ( 628 )   PDF (1044KB) ( 427 )   Save  Based on the visibility, relative humidity, precipitation, synoptic situations and the concentration of PM10 from 2006 to 2010 in Fujian province, the characteristics of low visibility weather and its impacting factors were analyzed, and the coastal cities were divided into three city groups, i.e. the north, the middle and the south. The results indicate that the annual haze days are from 8 to 26 days in the north city group and the low visibility is caused by (light) fog, while it is caused by haze in other two city groups. The (light) fog and haze weather usually occur in December to June and seldom in other months. The mean visibility is higher in summer and autumn than in winter and spring. The short duration for the low visibility weather, light fog and haze is prevailing, and then is half a day; the least is the whole day in three city groups. The light fog usually occurs under low vortex shear condition, and then under upper trough and warm zone convergence condition, the third is under transformed surface cold high condition, while haze is often under warm zone convergence, upper trough and transformed surface cold high conditions. The mass concentrations of PM10 are 0.068-0.109 mg·m-3, 0.044-0.064 mg·m-3 and 0.041-0.072 mg·m-3 under haze, (light) fog and non-low visibility weather conditions. Related Articles | Metrics

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Introduction of IGRA dataset and analysis of its data quality CHEN Zhe,GAO Jie, YANG Xu 2013, 29 (5):  106-111.  Abstract ( 2734 )   PDF (746KB) ( 700 )   Save The integrated global radiosonde archive (IGRA) is developed by the American national climatic data center (NCDC), and the dataset includes the multi-level, multi-daily radiosonde data elements of 1538 worldwide sounding stations from 1938 till now. The IGRA has the highest space-time density, and is the most complete and high-quality sounding dataset in the world. The IGRA dataset and its quality control were introduced and its data quality was analyzed. The results indicate that although this dataset has data quality control, it still has some problems. For example, the inconsistent rate of data from the IGRA and NMIC (Chinese national meteorological information center) datasets exceeds 70% for the sounding temperature data in China before 1973. The improper wind speed data from the IGRA are mainly from 1975 to 1978 and in 1981 and its rate accounts for 50.74 % among the wrong wind data in the above five years, and most wrong wind data concentrates in stations of the south American, the middle and south Africa and Russia. Most radiosonde data in the world are transported by the global communication system after 1980, so the quality and integrity of the radiosonde data from the IGRA after 1980 are relatively high. This paper can offer a reference to dataset users. Related Articles | Metrics

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The characteristics of sunshine duration from 1961 to 2009 in northeast China ZHOU Xiao-yu, ZHANG Xin-yi, CUI Yan,WANG Ying, ZHANG Xiao-yue,ZHAO Chun-yu 2013, 29 (5):  112-120.  Abstract ( 833 )   PDF (1342KB) ( 639 )   Save Based on the sunshine duration, temperature, precipitation, wind speed and relative humidity data at 104 weather stations from 1961 to 2009 in the northeast China, the monthly, seasonal and annual trends of the sunshine duration and its spatial distribution were analyzed using  methods of a trend analysis, a Mann-Kendall test and a correlation analysis. The impacting factors of sunshine duration were also discussed. The results show that the highest and lowest sunshine duration occurs in May and December, respectively. The annual sunshine duration has a significant decreasing tendency  with 40.5 hours per  decade. The seasonal sunshine duration significantly decreases except for in autumn. The sunshine duration has an abrupt change in the early 1980s and then decreases. The sunshine duration in the northeast China is high in the west and low in the east. Except that in the northern Heilongjiang province, the sunshine duration in the other regions is in a decreasing tendency, especially in the northern Jilin province. The annual sunshine duration is in a negative correlation with annual mean temperature, precipiation and relative humidity, and the corresponding correlation coefficients are -0.40, -0.37 and -0.32 respecitvely, while it is in a positive correlation with wind speed and the correlation coefficient is 0.53. The relative humidity coefficient passes 99.5 % confidence levels, and the other passes 99.9 % confidence levels. Related Articles | Metrics

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Temporal and spatial distributions of cloud-to-ground lightning in Shenzhen JIANG Yin,TAN Ming-yan, LI Lei, CAO Chun-yan 2013, 29 (5):  121-125.  Abstract ( 686 )   PDF (1008KB) ( 548 )   Save Based on the cloud-to-ground lightning data from the detecting station during 1997 to 2011 and the observational data from the national basic weather station at Shenzhen during 1953 to 2011, the temporal and spatial distributions of cloud-to-ground lightning flashes (hereafter abbreviated as lightning flashes) and the trends of thunderstorm days in Shenzhen were analyzed. The results show that the annual thunderstorm day is in a descending trend in recent 59 years, and it is a 5 years main cycle and a 10-15 years sub-cycle by a wavelet analysis. The significant peak values of the monthly thunderstorm days occur in June and August, especially in August. There is a close relation between activity of thunderstorm and solar radiation. The frequency of lightning flashes is highest from 14:00 to 18:00 at Shenzhen. Many lightning flashes are recorded in the northwestern area and inland area, while the few are in the southeastern area and coastal or riverside area in Shenzhen. The spatial distribution of lightning flashes is significantly influenced by the land-sea distribution and the topography. The analysis of the lightning intensity shows that the positive and negative peak values of mean monthly lightning intensity appear in February and June respectively, and the intensity of the negative lightning is lower than that of positive lightning flashes. Neither the positive lightning nor the negative lightning flashes, they never occur in the time period that the frequency of lightning flashes is the highest. Related Articles | Metrics

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Distribution of hail and its correlation to topographical factors based on GIS in Dalian ZHU Qing-lin,WANG Li-na, BIAN Ruo-fen, WANG Xiu-ping 2013, 29 (5):  126-131.  Abstract ( 619 )   PDF (1062KB) ( 771 )   Save Based on the observational hail data from 64 weather stations from 1971 to 2010 and 1:50 000 digital elevation model (DEM) in Dalian, the topographical factors such as elevation, slope, aspect, relief amplitude and terrain incision depth which can be extracted from digital elevation model were selected as potential affecting factors, and the relationships between topographical factors and hail were analyzed using  methods of a digital terrain analysis and an irregular zonal statistics and so on. The results indicate that mean elevation, west-northwest aspect and terrain incision depth are the major factors affecting the distribution of hail. With the increase of elevation, the occurrence probability of hail increases. The west-northwest aspect and complex topography are favorable to the formation of hail, especially for the latter. Finally, a regression equation is established to simulate the relationship between the hail and topographical factors, and the distribution map of hails is simulated. It shows that the serious hail disaster occurs in the northern Wafangdian and Pulandian, while it is seldom in the coastal and southern regions. Related Articles | Metrics

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Change of soil moisture in maize field and its effects on maize growth JIANG Li-xia, YANG Xiao-qiang,ZHANG Li-qun,WANG Liang-liang, LI Shuai 2013, 29 (5):  132-135.  Abstract ( 570 )   PDF (654KB) ( 496 )   Save The main maize variety (Huke 336) in Heilongjiang province was treated with the contrast observation under natural conditions in the maize field, and the effect of different soil moisture on maize growth was analyzed. The results show that soil moisture in the different surface layers (0-30 cm) is in a decreasing tendency in 2011 in Longjiang maize field. The effect of soil moisture in different soil layer on maize growth is different. It has a significant effect on green leaves area and dry weight. Within a certain soil moisture range, the leaf area will increase 28.338 cm2 if soil moisture increases 1%. Suitable surface soil moisture is favorable to increase green leaf area and dry matter of maize. Related Articles | Metrics

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The effect of meteorological factors on soybean yield LIU Jing-li,YANG Yang, LIANG Tao,SHI Kui-qiao,ZHANG Bing-bing,ZHANG-Hui,XU Chang-hua,SONG Min,LU Gang 2013, 29 (5):  136-139.  Abstract ( 637 )   PDF (414KB) ( 488 )   Save Based on the observational field data of soybean from 2001 to 2009, the effect of meteorological factors and biological factors in different soybean growth stages on soybean yield was analyzed using methods of a correlation analysis and a path analysis. The results show that the effect of meteorological factors in the different growth period on soybean yield differs. Among all factors, the correlation coefficient between the mean air temperature and soybean yield is highest and reaches 0.90 in the flowering and bearing pod stages, then that between precipitation and soybean yield is 0.71 in sowing date-emergence stage. Furthermore, relative humidity and sunshine duration in the bearing pod stages to seed-filling period, biomass in the branding stage and leaf area in the flowering stage could also affect the soybean yield (r>0.5). The path analysis indicates that leaf area in the flowering stage is the main and direct influencing factor to soybean yield, while the greater effect of temperature and precipitation on the yield is produced by the indirect effect of biomass and leaf area. Relative humidity and sunshine duration in the bearing pod stages to seed-filling stage have large influence on soybean yield. A regression equation is established by coupling the meteorological factors and biological factors, which could simulate well soybean yield (R2=0.99). Related Articles | Metrics

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Quantitative assessment of impact of extreme high temperature in summer on excess mortality in Wuhan YANG Hong-qing,CHEN Zheng-hong, XIE Sen,YE Dian-xiu, GONG Jie 2013, 29 (5):  140-143.  Abstract ( 1137 )   PDF (487KB) ( 556 )   Save Based on the daily mortality data in Wuhan during June to August from 1998 to 2008 and the corresponding daily meteorological data, the impact of extreme high temperature in summer on population mortality was analyzed and the threshold value of extreme high temperature leading to excess death was determined. An assessment model was established by a stepwise regression method and it was verified, which was useful to assess the effect of high temperature on human health and predict the medical meteorological factors. The results show that the excess mortality in Wuhan can be quantitatively described. The extreme high temperature in summer has great impact on excess mortality, while air humidity, pressure and wind speed almost have no effect on it. The excess mortality rate is in an exponentially increasing trend with the increase of daily maximum air temperature, and its threshold value is 35.0 ℃. The excess mortality is 50.7% higher in “Hot day” than in “Non-hot day”. The excess mortality model is established by effective accumulated temperature with daily maximum temperature ≥35 ℃ and the daily average temperature. Using this model, a high temperature and wave process in 2003 is tested by a back substitution method. It has a good assessment effect for mortality cases during summer of 2007 and 2008. This model could be used to the operational application. Related Articles | Metrics

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The effect of temperature on hatching of Asiatic migratory locust in the grassland of northeast China LE Zhang-yan,BAI Yue-ming, LIU Ling,WANG Pei-juan,GAO Su-hua 2013, 29 (5):  144-147.  Abstract ( 518 )   PDF (599KB) ( 377 )   Save In order to clarify the relationship between the hatching process of Asiatic Migratory Locust and heat conditions in the grassland of northeast China, the influence of temperature and effective accumulated temperature on the overwintering hatching of Asiatic migratory locust was analyzed using an artificial climate box. The results show that the number of hoppers, the output rate of hoppers, the accumulated hoppers and the accumulated output rate of hoppers increase with the mean daily temperature rising. The locusts begin to sprout and hatch when the daily minimum temperature exceeds 25.0 ℃ for three consecutive days. It hatches rapidly when the daily minimum temperature is about 26.0 ℃, while the output rate of locust hoppers slow down when the daily minimum temperature is below 25.0 ℃. When the effective accumulated temperature higher  than 25 ℃ reaches 11.6 ℃•d and the active accumulated temperature is 211.6 ℃•d, the locust eggs begin to hatch. When the effective accumulated temperature increases to 20 ℃•d and the active accumulated temperature exceeds 320.0 ℃•d, the hatching speed slows down and reaches the second small peak of hatching immediately, then the hatching process is over. Related Articles | Metrics

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The application of numerical simulation technique to macro-siting of wind farm XIE Jin-fan ,WANG Yu-kun ,ZHANG Liang, ZHANG Ting ,YU Li 2013, 29 (5):  148-153.  Abstract ( 688 )   PDF (2402KB) ( 439 )   Save It was difficult to confirm the potential wind area according to the meteorological data from the current sparse weather stations. However, the numerical simulation technique can make it up with improving the spatial resolution. The wind energy resource in the west of Jilin province was simulated by the WRF (weather research and forecast) model. The results show the diurnal and annual variations of wind speed could be simulated well. The correlation coefficients between simulated and observed values at 10 m, 50 m and 70 m heights are 0.889, 0.862 and 0.865, respectively, and they all pass 0.001 significance level test. Simulation results could reveal the potential wind area that may not be explored by the observational data. The numerical simulation techniques can be used for siting of wind farm, which is confirmed by the observation of wind tower. It reveals that the simulated wind speed is higher than the observed speed and the simulated spatial distribution differences are less than observed one. It suggests that there is limitation for the accuracy of existing numerical model, so wind farm micrositing would be still relied on the observation of wind tower. Related Articles | Metrics

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Impact of meteorological conditions on the peak load in southern Hebei power system during spring irrigation QU Xiao-li ,ZHAO Na ,ZHANG Jin-man ,WU Hui-qin ,ZHANG Cheng-wei 2013, 29 (5):  154-158.  Abstract ( 606 )   PDF (501KB) ( 411 )   Save  Based on the peak load data and the daily meteorological observational data from 2007 to 2010 in the southern Hebei province, the annual and daily variations of the peak load were analyzed. The results show that the trend curve of the peak load has three peaks and two valleys. Three peak loads appear in the spring irrigation period, the summer high temperature period and before and after the winter heating period, while two low valleys are in the spring festival of China and from October 1 to 7. The three irrigations of winter wheat had a significant effect on the peak load. The regional strong wind and rainfall could make the peak load decreased obviously. The grades of daily peak load are divided based on its variation amplitude. The relationship between peak load and meteorological factors was analyzed using methods of a correlation analysis and a multiple regression analysis, and a forecast model is established. This model is favorable to adjust the routine electric power according to the practical test. Related Articles | Metrics