Table of Content

28 December 2012, Volume 28 Issue 6 Previous Issue    Next Issue

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Warning characteristic and trigger mechanism of a local strong hailstorm in northern He’nan province SU Ai-fang,LIANG Jun-pin,CUI Li-man,LIU Chao 2012, 28 (6):  1-7.  Abstract ( 669 )   PDF (3202KB) ( 603 )   Save Based on the conventionally meteorological observation data, Doppler radar data, satellite data, meteorological data from regional automatic weather stations and the NCEP reanalysis data, the forewarning characteristic and trigger mechanism of a local strong hailstorm occurred on June 11, 2011 in the northern He’nan province were analyzed. The results show that the local severe convective weather occurs under the background of the northeast cold vortex, and the potential area of severe convective weather is located on the right side of the junction areas of upper and lower mesoscale synoptic system (trough, sheer line, the axis of larger wind speed ). The CAPE values are large and the vertical wind sheer from 0 km to 6 km determined from the revised sounding data before the local severe hailstorm weather happens is moderate or strong, which facilitate the formation and development of supercell. The convective instability of atmosphere increases while the cold advection in upper level moves southward and the warm advection in lower level moves northward. The meso-β-scale convective cloud cluster is generated in the rear of the northeast cold vortex and its development and evolution have some certain reference values for weather warning. Strong convective echo goes through the developing stage with cell shape to band shape and the weakening stage with block shape. The supercell generated on the south of the convective echo-belt results in the characteristic of ‘three-body scattering’ when the local severe hailstorm weather appears. The cold air and surface convergence lines are the important trigger mechanisms for severe convective weather, and the surface convergence lines are indicative for strong convection weather. Related Articles | Metrics

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Diagnostic analysis of a heavy snowstorm process inTianjin area WU Zhen-ling,WANG Jing,ZHAO Gang,LIU Yi-wei,SHI De-dao 2012, 28 (6):  8-13.  Abstract ( 667 )   PDF (3601KB) ( 602 )   Save Based on the conventional meteorological observational data and the NCEP reanalysis data, the heavy snowstorm process in the last ten-day period of February of 2011 in Tianjin area was diagnosed. This process was under the situation of typical return-flow weather in the north China. The results show that the westerly circulation over the north China is mainly the zonal type during the return-flow snowfall process. Cold air mainly leans to northward, and the main influencing systems are the return-flow cold high in north China and low pressure inverted trough. At the same time, there exists a thin cold air cushion in return-flow snowfall accompanied by the climbing of warm-wet air that can reach about 650 hPa. During the process of the return-flow snowfall, the southwesterly warm-wet air and northeasterly cold-dry air converges in Tianjin area, and it is the northeast air flow at low or ultra low levels. Ultra low level jet stream and southwest warm-wet air flow appear near 900 hPa and above 700 hPa, respectively. There is the uniform strong ascending motion from the low to high troposphere during the snowfall and the ascending height can reach 200 hPa, which corresponds to the strong low-level and ultra-low-level convergence. The convective instability energy and symmetry instability are strong before snowfall in Tianjin and its surrounding area, which is favorable to the development of convection. Related Articles | Metrics

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Forming reason of a warm front rainstorm case and its radar echo characters in Dalian area LI Yan,ZHANG Jun-feng,WANG Shu-xiong,LIU Xiao-chu 2012, 28 (6):  14-18.  Abstract ( 691 )   PDF (2805KB) ( 605 )   Save Based on the conventionally observational data, meteorological data from automatic weather stations and Doppler radar data and so on, a rainstorm and locally heavy rainstorm event on July 14, 2009 in Dalian area were analyzed. The results show that it is a warm front rainstorm process. The upper-level trough located in Hetao area moves northward and overlays with the tail of the north branch trough. In the middle and low levels, a vortex circulation forms from the northern Bohai Sea to Dalian area. The region of high cyclonic curvature at 700 hPa is located above surface warm front. The top of surface cyclone, i.e. the top of warm front is just in Dalian area. This weather pattern results in the occurrence of heavy precipitation. High humidity area together with low-level convergence centre in front of the warm front and upper-level divergence centre provides favorable moisture and dynamic conditions for heavy rainstorm event. Radar echo analysis shows theβ-middle scale reflectivity area with 45 dBz in front of the warm front and the “single oxeye” characteristics in radial velocity field directly contribute to this rainstorm and short-time strong precipitation. The analysis of VWP data shows the height of shear layer formed by low-level southeasterly jet and upper-level southwesterly jet and the intensity variation of the two jets correspond to warm front and determine the rainfall intensity. Related Articles | Metrics

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Analysis of meso-micro scale system in a?rare heavy rain on the?northern slope of Tianshan Mountain ZHAO Jun-rong 2012, 28 (6):  19-24.  Abstract ( 460 )   PDF (2526KB) ( 517 )   Save Based on the Doppler radar products and T639 reanalysis data, small-scale system characteristics of a rare heavy rain on June 22, 2010 in the south of Shihezi and its occurrence time and falling area were analyzed. The results show that mesoscale short wave split from cold low-pressure from Siberia to Lake Balkhash is the direct influencing system of this process. The middle scale shear line from low level to ground and convergence line as well as cold front are the trigger mechanism for the local heavy rain. There is the transportation of strong southwest and southeast warm-wet air flow and their strong convergence in front of the mountain near low level, which provides the effective moisture and unstable energy for this process. Multiple-γ convective cells roll and change along the special topography, which are the direct reasons forming falling areas of the local strong rain event. The occurrence of meso-cyclone is indicative to the heavy rain. The heavy precipitation occurs in the superposition areas where the echo intensity is more than 50 dBz, the echo top height exceeds 5 km, vertical accumulated liquid water content is above 45 kg·m-2 and it exists in the mesocyclone. It is in advance about 20 min for warning of short-time strong precipitation using mesocyclone. Related Articles | Metrics

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Comparison analysis of downscaling forecast methods on wind speed in wind power field LI De-qin,CHEN Li-qiang,ZHOU Xiao-shan,YANG Sen,WANG Shu,CUI Jing 2012, 28 (6):  25-31.  Abstract ( 867 )   PDF (1331KB) ( 804 )   Save  The small-scale CALMET model and bilinear interpolation (BLI) method were used to downscale the output of mesoscale numerical weather prediction from the WRF model using both 9 km and 3 km resolutions. The simulated and observed wind speeds were compared. The results show that forecast accuracy of wind speed after downscaling with the CALMET model is higher with 9 km resolution than that with 3 km resolution. At the same time, the forecast effect of wind speed is also good using the BLI method because of the spatial resolution of mesoscale numerical weather prediction model is high. Wind speed is divided into three levels, namely, 0 m·s-1≤wind speed<5 m·s-1, 5 m·s-1≤wind speed<10 m·s-1 and wind speed≥10 m·s-1, and the percentage of prediction errors of three levels are tested. It shows that forecast results for wind speed ≥10 m·s-1 are poor no matter whether the CALMET model or the BLI method. It is therefore important to correct strong wind forecast for improvement of wind speed forecast accuracy. Related Articles | Metrics

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Characteristics of water vapor content and its influencing factors in summer over Northern China HAN Jun-cai,ZHOU Shun-wu,LIU Wei 2012, 28 (6):  32-37.  Abstract ( 539 )   PDF (1114KB) ( 585 )   Save  Based on the radiosonde data from 14 sounding stations and the NCEP/NCAR reanalysis data from 1979 to 2008 over the Northern China, the temporal and spatial distributions of water vapor content in summer and its influencing factors such as circumfluence were analyzed using methods of a linear trend and a Mann-Kendall mutation test as well as a composite analysis. The results show that water vapor content decreases with the increase of latitude from the southeast coastal areas to northwest inland areas over the Northern China, namely, the southeast is wet and the northwest is dry. On the whole, the water vapor content in summer is in a slightly increasing trend in recent 30 years, and it has an obviously abrupt change on the late 1980s. Whether or not there is obvious water vapor convergence to North China from South China Sea to the western Pacific and whether or not there is water vapor transportation to North China in westerly belt in middle latitude in the year with more or less water vapor content will lead to the surface temperature high or low on the whole. The location of subtropical high moves to westward and the intensity is stronger for the year when there is more water vapor content at 500 hPa height fields. Related Articles | Metrics

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Character of severe convection weather from 1991 to 2008 in Fujian province CAI Yi-yong,WANG Hong,YU Yong-jiang 2012, 28 (6):  38-43.  Abstract ( 505 )   PDF (469KB) ( 559 )   Save Based on the meteorological data from 1991 to 2008 in Fujian province, the temporal and spatial distributions of severe convective weather and its formation reason as well as the dominantly synoptic patterns were analyzed. The results indicate that the monthly change of severe convective weather presents a typical bimodal pattern with the higher one from March to June and the other from July to August. A majority of severe convective weathers occur during 14:00 to 20:00 and life time is normally less than one day, and its influencing areas are often within two weather stations. The spatial distributions of severe convective weather in different seasons are different. The regional character of severe convective weather in spring is obvious.  For example, the most severe convective weather events occur in the inland mountain, the middle and north areas rather than in the coastal area and in the south areas. In comparison, the distributions are even in other seasons. Severe convective weather often occurs under severe shear weather situation and mainly happens in spring, autumn and winter. The rates of severe convective weather situations accompanying with low-level southwest jets are 66.5%, and the majority are types of moderate or slightly northward jet. The dominant synoptic situations are low trough and low-vortex shear or upper-level trough which influences areas covering more than three stations or ten stations. The severe convective weather of weak shear type often occurs during July to September, and the dominant synoptic patters are subtropical high edge type and typhoon periphery type. There are not southwest jets in low level, so a wide severe convective weather rarely happens. Related Articles | Metrics

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An observational study of atmospheric ice nuclei concentration using 5 L mixing cloud chamber in Fushun, Liaoning province ZHOU De-ping,LI Bing-kun,CHEN Guang,HONG Ye,ZHANG Yun-hai,WAN Zhi-hong,DONG Guo-ping 2012, 28 (6):  43-49.  Abstract ( 457 )   PDF (899KB) ( 531 )   Save The atmospheric ice nuclei (IN) concentrations near the ground were measured in atmospheric composition station using an improved Bigg mixing cloud chamber in Fushun during May to November, 2011. The features of the diurnal and seasonal IN concentrations were analyzed and the effects of meteorological elements such as wind, air pressure, air temperature, humidity and weather situation etc. on IN concentrations were discussed. The results show that the average IN concentrations is about 30 L-1 (when activation temperature reaches -20 ℃) in Fushun during the observational stages. With the decline of activation temperature, the IN concentrations increase exponentially. The meteorological factors have a certain influence to the IN concentrations, and the influencing extent is different in the different seasons. Related Articles | Metrics

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Prediction models of summer extreme high temperature in Liaoning province LI Jiao,REN Guo-yu,REN Yu-yu,SHEN Zhi-chao,SUN Xiu-bao 2012, 28 (6):  50-57.  Abstract ( 550 )   PDF (3844KB) ( 588 )   Save Based on the summer extreme high temperature data in 23 weather stations in Liaoning province and 74 circulation indices information from the climate monitoring department of the National Climate Center (NCC), China Meteorological Administration (CMA), the temporal and spatial distribution features of summer extreme high temperature in Liaoning province were analyzed by a Empirical Orthogonal Function (EOF) decomposition method. The results show that the first EOF vector is characterized by a uniform anomaly over the whole area and the centers are in the northern and northwestern Liaoning province, while the second and third EOF vectors are the reversed phase patterns in the east and west areas and in the south and north areas, respectively. The correlation coefficient between first three time coefficient series and preceding circulation indices are calculated. It is found that the influencing factors are different for the three time coefficients. The optimum subset regressions are chosen as prediction equations using the CSC evaluation method and the fitting rate of past records in the 23 weather stations and each year are tested. It shows that the fitting rate of past records in the 23 weather stations is generally stable, except for in the western Liaoning province. In addition, the fitting rate is unbalanced each year, and it is stable in most years, while it is low in few individual years. While the prediction effect is good for the first year in the future it declines yearly in the following two years. The results can be used as reference in climatic prediction. Related Articles | Metrics

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Analysis of a short-time heavy rainfall in southeast of Jilin province on July 31, 2010 CHOU Shi-lian,CHEN Chang-sheng,WANG Kui-yun 2012, 28 (6):  58-64.  Abstract ( 635 )   PDF (4067KB) ( 446 )   Save Based on the real-time observational data from the dense weather stations, the NCEP reanalysis data with 1°× 1° resolution and Dopplor radar data in Baishan, a short-time heavy rainfall process on July 31, 2010 in the southeast of Jilin province was analyzed. The results show that a small short-wave disturbance appears in 500 hPa flat front area accompanied by severe connective weather. The thermal vertical structure which is cold in upper level and warm in low level is favorable to lifting of low level convergence. Precipitation does not occur when convergence lifting caused by wind field only exists in the bottom, so one must pay attention to the structure change of the whole field wind. Water vapor is from accumulation of prophase precipitation, and lacking water vapor transportation is one of the main reasons that this rainfall lasts in only short period. The invasion of small stock cold air in the high energy region is the trigger origin of heavy precipitation. The location of strong rainfall falling area corresponds to that of the high energy area invaded by cold air, and so is the period of the heavy rainfall and the process that the K index decreases from the maximum value, then unstable energy releases quickly. The intensity and gap of radar echo, the intensity of radical velocity, zero velocity line shape, and headwind area are indicative to the heavy rainfall. Related Articles | Metrics

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The temporal and spatial characters of gale in the northern coast of the Yellow Sea and the Bohai Sea, China WU Man-li,CHEN Yu,WANG Ying,QIAO Xiao-shi,LIANG Han,LU Jing-long,LI Shuang 2012, 28 (6):  65-71.  Abstract ( 604 )   PDF (1479KB) ( 625 )   Save  Based on the wind direction and wind speed data on 18 weather stations around the northern coast of the Yellow Sea and the Bohai Sea and the NCEP reanalysis data from 1971 to 2008, the temporal and spatial distributions of wind field were analyzed using a statistical method, a wavelet analysis and a weather pattern. The results show that gale is in a significantly decreasing trend around the northern coast of the Yellow Sea and the Bohai Sea. The gale occurs mainly in spring, especially in April, then in November. The wind directions are south and north in half year of summer and in half year of winter, respectively. Weather patterns are divided into four types, i.e. cold front rear type, high pressure rear type, typhoon type and cyclone type. Moreover, cyclone type includes types of Jianghuai cyclone, North China cyclone, Mongolia cyclone and northeast low-pressure. Among them, the frequency of cold front rear type is the highest, then that of the cyclone type, and that of typhoon type is the lowest. Related Articles | Metrics

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The effect of climate change on heating period in winter in Shenyang GUAN Jian-hua,WANG Guan,LI Lan,MING Hui-qing,TANG Ya-ping,SUN Jing,ZHAO Miao,ZHANG Nan 2012, 28 (6):  72-75.  Abstract ( 621 )   PDF (626KB) ( 676 )   Save Based on the annual mean air temperature data and the daily mean air temperature data of the one month before heating and after heating from 1961 to 2010 in Shenyang, the annual mean air temperature trend and mean air temperature trend of heating period were analyzed using methods of a linear trend and a degree-day. The beginning date and ending date of heating, heating duration and heating intensity were discussed. The results show that the annual mean air temperature and mean air temperature of heating are in increasing trends from 1961 to 2010, especially the former and it passes the significance test. The beginning date of heating is put off because of climate warming, and the ending date of heating is in advance. The heating duration is shortened. The climate warming makes the heating intensity decreasing. Related Articles | Metrics

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Design and implementation of the provincial new generation meteorological telecommunication system information transmission flow LIU Jin-xia,WANG Hui-yu,ZHAO Wei,LI Jing 2012, 28 (6):  76-80.  Abstract ( 476 )   PDF (824KB) ( 635 )   Save A new generation domestic meteorological telecommunication system was important promotion after “9210 project”. The unified management platform of the national and provincial meteorological departments was established, including data transmission, processing and system monitoring function. According to the national meteorological wide band development schedule, the current meteorological telecommunication system will be replaced by a new generation of domestic meteorological telecommunication system. At present, the new generation domestic meteorological telecommunication system and the current operational system were running simultaneously, which was the needs of not only the new system test but also the localization configuration and flow management. The operational flow of the new generation meteorological telecommunication system was set up and run in the operation work in Liaoning province based on the classification flow, which operates synchronously with the current system. Radar products and its basic data were transferred to the new generation domestic meteorological telecommunication system by PUP software, so were automatic weather station (AWS) data and wind energy data by the software of center station, while others were transferred by 9210 transmission server and radar transmission server. The results show that all meteorological information can be transmitted to the National Meteorological Information Center by the new generation communication system and it does not affect the current business. This meets the needs of testing the new generation communication system and localizing application. Flow design of this system is reasonable, and it can meet the demand of the meteorological information transmission quality check. At last, the current telecommunication system transportation flow, the aim and rule as well as scheme of design of the new system flow, and its operational effect are introduced. Related Articles | Metrics

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Evolvement character of agricultural climate resources in Liaoning province from 2011 to 2050 based on B2 climate change scenarios LIU Jing-li,JI Yang-hui,MI Na,HU Dan,SHI Kui-qiao,ZHOU Li-na,LI Shi,CAI Fu 2012, 28 (6):  81-87.  Abstract ( 526 )   PDF (2073KB) ( 642 )   Save Based on the output data of the regional climate model PRECIS, the temporal and spatial evolvement characteristics of agricultural climate resources considering future climate change scenarios of B2 (2011—2050) in Liaoning province were investigated by the methods of a time series analysis and a spatial analysis. The results indicate that the increasing trend of radiation resources is not significant, but has a peak value from 2031 to 2040. Precipitation is in a decreasing trend during the growing season, and the changes of radiation resource and precipitation are contrary. The decreasing amplitude of precipitation increases from the west to the east, and reaches 20 mm/decade in the east of Liaoning province. Precipitation is indicative to flood and drought events in the different periods. The accumulated temperature (≥10℃) is in an obvious increasing trend, and its increasing amplitude is 100 ℃·d/decade in most of Liaoning province. The beginning date of frost is delayed 1-3 days in the east of western Liaoning province and the west of northern Liaoning province, while the ending date of frost is  advanced in about 1-2 days in the north and the east of Liaoning province. The changes of the beginning and ending dates make frost-free season are prolonged, and it suggests that the thermal resource will increase obviously in future 40 years, which will provide the references for the adjustment of agricultural planting structure in order to respond to climate change. Related Articles | Metrics

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Interdal-annual variation of freezing event and its relationship with atmospheric circulations in Hubei province CHEN Wei,YUE Yang,DENG Hong,LONG Li-min 2012, 28 (6):  88-95.  Abstract ( 614 )   PDF (3710KB) ( 501 )   Save Based on the daily observation data from 16 meteorological stations and the NCEP/NCAR reanalyzed data from 1961 to 2010 in Hubei province, the distributions of the numbers of freezing day and its evolution characteristics were analyzed. The atmospheric circulation characters were discussed in more and less year of freezing day. The results indicate that the mean annual freezing day in winter is 8.2 days, and its spatial distribution is characterized with more in the west and less in the east and more in the north and less in the south, which is related to the topography of Hubei province. There are many mountains in the west of Hubei province and less river valley. The inter-decadal variation of freezing day is obvious in recent 50 years. Its spatial distribution changes with ladder shape from more in the west and less in the east to more in the north and less in the south, while temporal distribution is in a increasing trend firstly and then in a decreasing trend and in a increasing trend again in recent 5 years. There is an abrupt change of decreasing in the early of 1990s. Additionally, the pentad freezing day concentrates in the areas and the southern areas along the Yangtze River, especially in the fourth and fifth pentad of January. The high ridge in Ural Mountain and the East Asia trough strengthen (weaken) abnormally at 500 hPa in high latitude area of the Asia, and so are the central Asia trough over the east of the Caspian Sea in the middle and low latitude areas and the Indian-Burma trough. At the same time, Mongolia strong (weak) cold high controls the East Asia mainland on sea surface pressure field, and it makes the freezing day more (less) in Hubei province. Related Articles | Metrics