Table of Content

28 February 2013, Volume 29 Issue 1 Previous Issue    Next Issue

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Numerical simulation and diagnostic analysis of a rainstorm process WANG Wen,CHENG Pan 2013, 29 (1):  1-11.  Abstract ( 500 )   PDF (4922KB) ( 605 )   Save Based on the NCEP/NCAR reanalysis data with the resolution of 1°×1° and the observational precipitation as well as the 3 h interval TRMM precipitation data, a heavy rain process on July 22, 2010 in the south of the middle of the?Yellow River was analyzed using a mesoscale Weather Research and Forecasting model (WRF). The results indicate that this rainstorm is simulated successfully by the WRF model. This rainstorm is generated together by a subtropical high over the West Pacific and a low trough in the Hetao area under a situation of large scale circulation. The abundant water vapor source is from the Indian Ocean and the Southern China Sea. The?mesoscale gravity wave is excited by the upper level jet stream on 200 hPa. According to the divergence field and cloud water distribution, the existence and moving direction of the mesoscale gravity wave could be determined. The reasons that effect of gravity wave on rainstorm generation in the east area of Gansu province are analyzed based on the simulation data. It shows that the mesoscale gravity wave in upper level jet and its absorption in lower atmosphere cause the formation of the rainstorm. According to the wind direction in upper jet and values distributions of the?nonlinear balance?equation (NBE), the area and moving direction of the mesoscale gravity wave could be determined in advance, so the falling area and time of rainstorm could be forecasted. Related Articles | Metrics

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A method for accurate calculation of Showalter index ZHANG Duan-yu,LI Hong-li,YE Jin-tao,LI Shu-ling 2013, 29 (1):  12-17.  Abstract ( 996 )   PDF (653KB) ( 562 )   Save Since Showalter index is widely applied in convective weather analysis and forecast, it is meaningful to calculate it accurately and rapidly all the time. Based on the rule that equivalent potential temperature is unchangeable during both dry and moist processes, condensation temperature and equivalent potential temperature were calculated using a series of equations provided by David Bolton. Showalter index was computed automatically and accurately by a program in terms of radiosonde data. 11 cases were selected to calculate Showalter index using the new method. Compared with other 5 methods, the new method has characteristics of simple calculation, less average and maximum absolute errors. The possible reasons included two aspects. Many complex derivations and approximation treatments have been avoided. On the other hand, the deduced figures such as the lifting condensation level temperature, the equivalent potential temperature were more accurate than that from other methods. Based on the radiosonde data with MICAPS format from 2010 to 2011at Hankou station in Hubei province, the forecast accuracy of two methods, namely, a table method and the new method in this paper, was compared for thunderstorm. The results show that the missed number of thunderstorm is reduced if a negative Showalter index is used as a factor to show the possible presence of thunderstorm. In addition, a limitation of the new method is also discussed. Related Articles | Metrics

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Characteristics of visibility over Anshan from 2010 to 2011 ZHAO Hu-jia,MA Yan-jun,ZHU Yi-ming,GAO Qing-yuan 2013, 29 (1):  18-22.  Abstract ( 706 )   PDF (577KB) ( 545 )   Save Based on the visibility data at atmospheric composition monitoring station of Anshan from June 2010 to May 2011, the relationship between visibility and meteorological elements such as mass concentrations of PM10, PM2.5, PM1.0, wind speed, precipitation intensity and aerosol optical depth (AOD) were analyzed. The results indicate that the monthly average visibility is in an increasing trend after August, reaches a peak in November and then drops significantly and gets the lowest value in February; it is in a substantial increase after March, while it is in a slight decrease in summer. The ratios of PM2.5 to PM10 and PM1.0 to PM10 have a negative correlation with the visibility, namely, the higher the visibility is, the lower two ratios are, and the decreasing trend of PM1.0/PM10 is significant. Thus, it suggests that particles affecting the visibility are mainly fine particles. The trends of the average wind speed and visibility are basically the same, while the trend of average wind is in a negative correlation with those of PM2.5/PM10 and PM1.0/PM10. The average visibility decreases with the increase of precipitation intensity. The average visibility in the days before the precipitation day and after the precipitation day is more than that in the precipitation day, and their change values and change rates increase with the increase of precipitation intensity. It can be seen by the change of the Angstrom exponent that pollutant particles impacting the visibility in Anshan are more stable as a whole. It is a significant negative correlation between visibility and AOD. Related Articles | Metrics

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Synoptic characteristics of heavy air pollution day in winter over Harbin ZHONG You-jun,GUO Shi-you 2013, 29 (1):  23-27.  Abstract ( 560 )   PDF (1815KB) ( 510 )   Save  Based on the data of the daily air quality report from China Ministry of Environmental Protection from 2000 to 2009, the day that air pollution index (API) is more than 200 is selected as the heavy pollution day, and its formation reasons were analyzed in terms of meteorological elements. The results show that the surface wind speed at 20:00 o’clock in the heavy pollution day in Harbin is the first level or calm. There is a temperature inversion phenomenon below 850 hPa for 85% heavy pollution days. The maximum inverse temperature is 0.73 ℃/100 m and occurs between the ground and 925 hPa. There is a descending motion below 850 hPa for 95% heavy pollution days. The primary synoptic situation of heavy pollution days is high pressure edge type, high pressure center type and low pressure edge type. It is not favorable to the horizontal and vertical transport of pollutants for the first two types, while it is favorable to the vertical transport of pollutants for the third type. The classification of synoptic situation could provide references for air pollution forecast. Related Articles | Metrics

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Weather situation classification and its feature in severe air pollution days in winter in Urumqi WANG Jian,LI Jing-lin,ZHANG Yue-hua 2013, 29 (1):  28-32.  Abstract ( 455 )   PDF (878KB) ( 588 )   Save  Based on the daily ground synoptic chart and the upper synoptic chart at 500 hPa at 08:00 in winter from 2000 to 2008 as well as the daily air pollution index (API) in Urumqi from the Internet, the seasonal and monthly atmospheric pollution characters were analyzed. The effect of circulation situation on air quality was discussed. The results indicate that circulation situation influencing Urumqi could be divided into 7 types in upper level and 5 types on the ground. The analysis of correlation between the different circulation situations and the serious pollution days in winter shows that circulation situations that causes easily the heavy pollution are high pressure ridge type and low vortex type,  followed by a high pressure ridge front type and ground cold high pressure type. Related Articles | Metrics

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Analysis of physical parameter field and echo characteristics of Doppler radar in a thunderstorm process YAN Fang,CHEN Jing,BIAN Tao,LIAO Ying-hui,ZHANG Cui-hua 2013, 29 (1):  33-39.  Abstract ( 552 )   PDF (2175KB) ( 754 )   Save A thunderstorm disasters appeared in Shijiazhuang region from 15:00 to 18:00 on August 27, 2009. The mesoscale synoptic systems of this process such as gust front, squall line and mesocyclone and so on were detected by a Doppler radar at Xinle county of Shijiazhuang region. The characteristics of physical parameter field of this process and Doppler radar product were analyzed. The results show that unstable stratification of temperature inversion in the low level and vertical wind shear in the middle and low levels provide favorable conditions for strong convective development. Gust front has feedback action on the development of convective storm intensity. When gust front is moving away from the convective storm, the convective storm weakens or even dies out; when both are gradually close to each other, the convective storm strengthens or even develops into a supercell convective storm. Multiple single convective storm belt arrangement constitutes a squall line system, which brings wind speed spurt, wind zag, pressure upwelling and temperature falling. The supercell convective storm has the typical features of echoes with a “hook” shape, a “herringbone” shape, a “bow” shape, and deep lasting mesocyclone. The ground destructive wind is mainly brought by supercell convective storms. Related Articles | Metrics

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The effect of ENSO events on climate in the western Sichuan Plateau area ZHENG Hao,XU Wu-cheng,SUN Gao-min 2013, 29 (1):  40-46.  Abstract ( 525 )   PDF (618KB) ( 625 )   Save Based on the precipitation and temperature data from seven meteorological stations in the western Sichuan Plateau area and the data of El Nino/La Nina events from 1951 to 2010, the relationship between precipitation, temperature and El Nino /La Nina events was analyzed. The effect of El Nino/La Nina events on the climate in the western Sichuan Plateau area was studied. The results indicate that the annual precipitation in the western Sichuan Plateau area changes weakly since 1951, and it has a weak increasing trend. El Nino/La Nina events have impact on the annual average precipitation. The annual average precipitation decreases because of the impact of El Nino events, while it increases because of the impact of La Nina events. The annual precipitation is 39.14 mm less in El Nino years than in the normal year, while it is 22.56 mm higher in La Nina year than in the normal year. The average of annual temperature fluctuates weakly and has an increasing trend in the western Sichuan Plateau area since 1951 .The correlation between the levels of ENSO events and the average annual temperature in the western Sichuan Plateau area is not significant since 1951. Related Articles | Metrics

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Winter temperature variability and its relationship with atmospheric circulation anomalies in Northeast China SHEN Zhi-chao,REN Guo-yu,LI Jiao,SUN Xiu-bao 2013, 29 (1):  47-54.  Abstract ( 477 )   PDF (1226KB) ( 577 )   Save Based on air temperature data from 90 metrological stations in winter from 1957 to 2010 in the northeast China, the study area was divided into the south and north subregions in terms of winter air temperature using methods of a rotated empirical orthogonal function (REOF) and a cluster analysis. The variation trends of winter air temperature and warm and cold winter were analyzed, and their relationships with main circulation indexes were discussed. The optimum forecast factor was selected by a back-method, and regression models were built in the whole study area and two subregions. The results indicate that winter air temperature increases obviously in the northeast China, and the ratio reaches 0. 45 ℃/ 10 a, especially in the north area. The correlation between winter air temperature and the simultaneous Euro-Asian zonal circulation indexes is significant. The subtropical high area index in August in the east Pacific Ocean, polar vortex area index in October in the Asia area and polar vortex area index in August in the north hemisphere are in the significantly positive correlations with winter air temperature, and their multiple correlation coefficients all reach 0.70. The above three factors are the key forecast factors in regression equations. If the subtropical high and polar area indexes are used as the important influencing factors when it forecast cold winter and warm winter, the forecast effect is good. Related Articles | Metrics

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The application of distributed model of mean monthly air temperature in Hebei province CHENG Hai-min,QIU Xin-fa,LI Meng-jie,LIU Hao-bo 2013, 29 (1):  55-61.  Abstract ( 639 )   PDF (1283KB) ( 471 )   Save Based on the conventionally observational data from 126 weather stations in Hebei province and surrounding area from 1971 to 2000, the monthly mean air temperature under the tugged topography condition was simulated using a  distributed model and a  spatial distribution map of air temperature with the resolution of 100 m ×100 m. The results indicate that the air temperature fluctuates weakly because of the flat terrain in the Bashang plateau and the plain area of Hebei province, while the effect of the local terrain on the air temperature is significant in a range of Yanshan mountain and Taihangshan mountain. The maximum air temperature difference between the south-facing slope and the north-facing slope with the same angle appears in January, then in October and April, while the minimum one occurs in July. The air temperature difference increases with the increase of slope angle during the same period. The air temperature fluctuates weakly and is higher than that in the surrounding area because there are many basins and river valleys in Zhangjiakou area. The simulation accuracy of the distributed model on mean monthly air temperature is high in Hebei province, so is the simulation capability of time and space dimensions, and it could be applied in the mountainous region. Related Articles | Metrics

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Study and establishment on conceptual model of heavy fog falling area in China MA Xiao-gang,LUO Si-wei,SHU Hai-yan,ZHANG Xu,ZHANG Hong-xia,GE Lin,SHEN Nan,WU Wen-jie 2013, 29 (1):  62-67.  Abstract ( 495 )   PDF (2635KB) ( 899 )   Save Based on the historical meteorological data from the meteorological information comprehensive analysis processing system (MICAPS), the main influencing factors in the typical regional heavy fog weather cases from 2008 to 2010 were analyzed by the physical mechanism of heavy fog formation. Seven factors that were favorable to the formation of heavy fog were selected. The results indicate that there are some certain features for sever factors, namely, the inversion layer thickness is 20-200 hPa; the ground temperature dew point difference is mostly less than 1 ℃, and it is mostly less than 3 ℃ on the previous day; the surface wet air thickness is 0.05-0.70 km; the inversion layer high point 0 ℃ line is the feature line of rime occurrence; the wind speed of southerly wind near  the ground is 2 to 6 m? s-1; air temperature is from -15 ℃ to 20 ℃ and most of temperature are between – 5.0 ℃ and 5.0 ℃, and 0 ℃ line is the feature line of fog occurrence; high pressure degenerates or weakens. These characters could be found 12 to 24 h earlier. Therefore, a heavy fog falling area conceptual model is established, so is a corresponding forecast system according to the model. Test shows that regional fog forecast can be advanced by 12 to 24 h, and the accuracy rate of 24 h regional fog forecast can reach 87.5 %. Related Articles | Metrics

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Character of soil temperature from 1980 to 2010 in Lishui, Zhejiang province WU Hao-min,WANG Hong-lei, LIANG Yan 2013, 29 (1):  68-73.  Abstract ( 500 )   PDF (691KB) ( 421 )   Save  Using the soil temperature data measured in 5 soil layers from 0 to 20 cm underground at weather station in Lishui from 1980 to 2010, the variation trend, abrupt changes of soil temperature and its response to climatic change in Lishui were analyzed in terms of methods of a linear trend analysis, a Mann-Kendall test and a correlation analysis. The results indicate that the annual mean soil temperature is in a significantly increasing trend with the ratio of 0.18 ℃/10 a, especially in winter. There is a peak value for the mean monthly soil temperature in Lishui. The amplitude of soil temperature variation decreases with the increase of the soil depth, and there exists a certain time lag. According to the Mann-Kendall test, the soil temperature is in a stable increasing trend in Lishui, especially from 2004 to 2009 in five soil layers, and it passes the test of 0.01 confidence level. The abrupt change of soil temperature in five soil layers lags with the increase of soil depth. The abrupt change of mean annual soil temperature occurs during 1994-1996. Soil temperature is in a significant positive correlation with air temperature, while it is in a significant negative correlation with spring and summer precipitation in Lishui, which is the response of soil temperature to climate change. Related Articles | Metrics

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Climate characters of high temperature and its formation reason in summer in Wenzhou CAO Chu,WANG Zhong-dong 2013, 29 (1):  74-79.  Abstract ( 754 )   PDF (1268KB) ( 610 )   Save  Based on the summer high temperature data from 1971 to 2010 in Wenzhou, the time sequence of high temperature process was built and the climate characters and the main weather systems were discussed. The results indicate that the temporal and spatial characteristics of summer high temperature are significant. The high temperature day increases suddenly since 2003, so is the frequency of hazard high temperature day. The main weather system influencing summer high temperature is subtropical high. When there is westely air flow, it is located near the ridge line of the subtropical high, there is warm center in the low level, and sunshine duration is long, the hazard high temperature will happen. When subtropical high reduces, it is southwesterly air flow in Wenzhou, it is controlled by warm area with above 20 ℃ at 850 hPa in south China, sunshine duration is long, high temperature weather occurs usually in Wenzhou. The above two weather types often appear from the last ten days of June to the first twenty days of July, and the probability is lower. The descending action caused by the north air flow outside the tropical system such as typhoon and so on will lead to high temperature weather, too. Related Articles | Metrics

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Climatic characteristics of thunderstorm in Dalian from 1951 to 2010 WANG Xiu-ping 2013, 29 (1):  80-83.  Abstract ( 793 )   PDF (655KB) ( 791 )   Save  Using the thunderstorm data from 1951 to 2010 in Dalian, the climatic characteristics of the thunderstorms were analyzed in terms of  methods of a mathematical statistics, a Mann-Kandall test and a Morlet wavelet analysis. The results show that the mean annual thunderstorm days increase in the recent 60 years, and the variation of the inter-annual and inter-decadal thunderstorm is significant. The annual thunderstorm day is in an increasing trend, and its ratio is the 0.5 d/ decade. The first thunderstorm date is ahead and the last thunderstorm date delays notably. The seasonal variation of thunderstorm is significant, and the frequency of thunderstorm is higher in summer than in autumn, while it is lowest in winter. Most thunderstorm appear during May to September, and those from June to August account for 60 %. There is a peak value for the mean monthly thunderstorm day, so are the mean monthly air temperature and the monthly precipitation. The maximum thunderstorm day occurs in July, and it decreases rapidly in October. Thunderstorm often occurs from 02: 00 to 06: 00 and seldom happens from 16: 00 to 20: 00. The thunderstorm days show 2-4 years and 14-16 years oscillating periods for inter-annual and inter-decadal variations, though these two periods are not significant. An abrupt change occurs in 1972. Related Articles | Metrics

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An objective forecast method on sea wind based on data from automatic weather stations WU Man-li,WANG Ying,YUAN Zi-peng,QU Rong-qiang,LIANG Han 2013, 29 (1):  84-88.  Abstract ( 507 )   PDF (507KB) ( 570 )   Save Utilizing wind speed and wind direction data from automatic weather stations along the coast in Liaoning province, mesoscale numerical prediction products from the MM5 model in Shenyang regional meteorological center were applied by a Kalman filtering method. A forecast method on the maximum wind vector along the Bohai Sea and the surrounding sea area was developed. The forecast results  from August to October of 2009 were tested. It is seen that the forecast accuracy of the maximum wind vector is higher for  wind speed than for  wind direction. The forecast accuracy of wind direction is highest in the north of the Huanghai Sea and reaches 57.3%, while that of wind speed is in the middle of the Bohai Sea and it is 64.6%. Most errors of wind speed are positive, and it means that the forecast value is higher than the observational value. This method is good for sea wind forecast in the Bohai Sea and the neighbor sea area. This forecast method could reflect truly the evolution process of sea wind, and it could provide references for the corresponding forecast. Related Articles | Metrics

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Progress in technology and application of agricultural weather forecast in Heilongjiang province WANG Ping,LI Shuai,YANG Xiao-qiang,WANG Liang-liang,GONG Li-juan,ZHU Hai-xia,JIANG Li-xia 2013, 29 (1):  89-92.  Abstract ( 359 )   PDF (526KB) ( 552 )   Save The progress in technology and application of agricultural weather forecast in Heilongjiang province was introduced. The method and technology of agricultural weather forecast were summarized, and the index database, the knowledge database, the technology and the work flow were emphasized. The light and heat resource of rice growth were assessed in Heilongjiang province. It indicates that the effect of sunshine on rice yield is significant compared with temperature, and its contribution rate on rice yield reaches 64.58%. The maximum contribution rate of sunshine appears in blossom stage and the minimum one is in sowing stage, while that of temperature is in jointing stage and the minimum one is in transplanting stage. Related Articles | Metrics

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A review on relationship between subtropical high anomaly over West Pacific and summer precipitation in the middle-lower reaches of the Yangtze River LI Hui,ZHOU Shun-wu,WANGYa-fei 2013, 29 (1):  93-102.  Abstract ( 458 )   PDF (1376KB) ( 859 )   Save The effect of subtropical high anomaly over West Pacific on summer precipitation in the middle-lower reaches of the Yangtze River was reviewed. On the basis of intensity and location of subtropical high over West Pacific and its formation reasons, the effect and mechanism of subtropical high anomaly over West Pacific on summer precipitation in the middle-lower reaches of the Yangtze River were summarized. The results indicate that dynamic factors and thermodynamic factors both affect subtropical high. There are 3-4 years and 10-13 years oscillation periods for subtropical high intensity over West Pacific. There is an abrupt change about 1978. The ridge position index starts to move from positive to negative, while the strength index is contrary. These changes influence significantly precipitation in the middle-lower reaches of the Yangtze River. The location, shape and intensity of subtropical high over West Pacific are one of decisive factors for drought and flood in the middle-lower reaches of the Yangtze River. There are generally four methods to be used to predict precipitation in the middle-lower reaches of the Yangtze River based on subtropical high over West Pacific. Finally, some existed problems and further directions are briefly discussed. Related Articles | Metrics

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Evaluation and division on climatic risk of rice delayed cool damage in Jilin province WANG Dong-ni,GUO Chun-ming,LIU Shi,YAN Xiao-ying 2013, 29 (1):  103-107.  Abstract ( 774 )   PDF (1615KB) ( 555 )   Save Jilin province is one of the major rice production areas in China. The rules of rice delayed cool damage and its risks were studied in order to prevent the damage and protect rice food safety. Based on the mean air temperature data at 46 weather stations from 1961 to 2008 in Jilin province, an index system was built, including heat variable coefficient during growing period, cool disaster frequency and its risk index as well as its climatic risk probability, and the risk of low temperature cool damage was assessed. Four indices were standardized using an extreme difference value method, and the synthetic index of climatic risk of rice low temperature cool damage was obtained by an equal weight method. The study areas were divided into five climatic risk areas of rice low temperature cool damage, i.e. the highest area, the high area, the middle area, the low area and the lowest area. The results indicate that the higher risk area is located in the east of Jilin province such as Yanbian, Baishan, and the lower one is in the most west of Jilin province, most Siping area and the south of Tonghua. Related Articles | Metrics

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Potential ecological risk assessment of heavy metal pollution in surface sediment of the Dahuofang reservoir REN Hong-quan,HU Cheng 2013, 29 (1):  108-112.  Abstract ( 384 )   PDF (842KB) ( 541 )   Save The Dahuofang reservoir is a typical drinking water source in the Liaohe River basin. However, the heavy metal pollution is an important problem for the Dahuofang reservoir due to waste water discharges from the surround industrial enterprises. The contents and distribution of the heavy metal in the surface sediment of reservoir such as Cr, Cu, Zn, Cd and Pb were analyzed by a Hakanson potential ecological risk index method in order to study pollution situation. The pollution extent and potential ecological risk were evaluated, and the evaluation results were tested by a geoaccumulation index method. The results indicate that Cd is the primary pollution element of potential ecological risk in surface sediment of the Dahuofang reservoir. The ecological risk order of five pollution elements is as follows: Cd>Cu>Pb>Cr>Zn. Related Articles | Metrics