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30 December 2014, Volume 30 Issue 6 Previous Issue    Next Issue

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Mesoscale convective conditions of abrupt and local rainstorm and its characteristics at Heishan of Liaoning province CAI Kui-zhi,JIANG Da-kai,YANG Lei,YU Zeng-hua,SUN Xiao-wei,CHEN Yu,TAN Shi-jun 2014, 30 (6):  1-7.  Abstract ( 539 )   PDF (5077KB) ( 395 )   Save  Based on data from conventional and automatic weather stations, satellite and radar, and the NCEP reanalysis data (1°×1°, 6 h), the mesoscale convective conditions and convective system characteristics of an extraordinary rainstorm process on August 15-16, 2013 at Heishan of Liaoning province were analyzed. The results show that the severe precipitation process is caused by mesoscale-β convectional systems. The short-term torrential rain area occurs at the edge of energy tongue. Surface eastward wind and topographic force are dominant factors that causes generation, development and movement of convection cells along the east side of mountain, which lead to the continuous and convectional precipitation. The mesoscale wind shear and vortex motivated by the northeast low-pressure cold front trigger the local torrential rain. Two separate convective cells generate in upper reaches of heavy rain areas, and merge together and then influence Heishan County. The oblique ascension airflow in front of echo moving direction and low heart echo both enhance precipitation efficiency. Related Articles | Metrics

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Contrast analysis of a heavy rain at the end of the first rainy season in 2010 in west and east of South China ZHANG Duan-yu,CUI Chun-guang,ZHAO Yu-chun 2014, 30 (6):  8-15.  Abstract ( 524 )   PDF (4210KB) ( 510 )   Save A heavy rain took place at the end of the first rainy season of 2010 in the South China, and this process in the west was different from that in the east. By applying the NCEP reanalysis data, conventional observation data, characteristics and mechanisms of the heavy rain were analyzed. The results show that as a whole, main influencing system at high levels over the Southern China is a weak ridge stretching southeast from South Asia High, and the air flow there is divergent. Middle level ridge stretching westward from Subtropical High retreats eastward firstly, and then moves westward. Once boundary layer jet forms, the heavy rain appears in the south of equivalent potential temperature front at low level, and stream convergence takes place. For different divisions, the heavy rain occurs at many stations simultaneously twice in the west of South China, and it lasts 1 day every time. Averaged indexes calculated using the radiosonde stations data show that 850 hPa equivalent potential temperature and precipitable water vapor are large, and stratification in the middle and low levels is very unstable before the number of stations with the heavy rain increases significantly in the west. Boundary layer jet weakens obviously twice over the west of South China between the two days when heavy rain takes place at many stations simultaneously. Between the two days of multiple heavy rain sites in the west, both upward movement and water vapor convergence in low level is interrupted obviously. It is only one time for the heavy rain event of many stations simultaneously in the east of South China, while it lasts for 3 days. The 3 indexes mentioned above are all not very favorable for the increase of number of heavy rain stations, although boundary layer jet maintains over the east of South China during the three days, and water vapor convergence and upward motion at low level are not interrupted. Thus this precipitation in the east is characterized with large areas, strong intensity and long duration. Generation or disappearance of southerly boundary layer jet and horizontal scale are crucial to heavy rain in the first rainy season in the South China. Related Articles | Metrics

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Influence of topography on a severe rainfall process in western He’nan province ZHANG Ning,SU Ai-fang 2014, 30 (6):  16-24.  Abstract ( 511 )   PDF (2330KB) ( 562 )   Save A severe convective rainstorm on July 29, 2007 in the western mountain area of He’nan province was simulated by a WRF3.3.1 mesoscale numerical model, and topographic sensitive tests were carried out at the same time. The results show that the model could simulate this process better, and simulated precipitation area and its center are coincident with the observed. A comparison of control test and topographic sensitive test shows that topographical change can affect both horizontal and vertical circulations as well as falling area of precipitation and its central rainfall level. When terrain height and gradient of windward slope rise, convergence of horizontal flow near the surface and lifting movement in middle level become stronger, and water vapor flux in low level increases, which increase the area and amount of rainfall. However, under the contrary conditions, strong precipitation center in the front of windward slope weakens or disappears. Also, precipitation in the lower reaches of mountain slightly increases. Analysis of relationship between topography height and precipitation of windward slope suggests that the latter rises or falls with the former changes correspondingly, while both are not an absolutely linear positive correlation. Related Articles | Metrics

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Analysis of isentropic potential vorticity for a heavy rain caused by a southwestern low vortex TIAN Xiu-xia,HE Li-hua,CHEN Xiao-juan 2014, 30 (6):  25-30.  Abstract ( 376 )   PDF (2206KB) ( 312 )   Save Based on the conventionally meteorological data and GFS reanalysis data with 0.5°×0.5° resolution, a heavy rainstorm on June 19, 2010 caused by a southwest low vortex in Hebei procince and Shandong province were analyzed, including its forming conditions and evolution of isentropic potential vorticity. The results show that the southwestern low vortex, high jet, low jet and surface low pressure are the main weather systems of this process．The evolution and forming of isentropic potential vorticity are indicative to activity status of cold air. Convergence of airflow on both south and north sides of the isentropic potential vorticity center is favorable to development of surface low pressure. High potential vorticity moves downward, which leads to the heavy rain. Precipitation area has a better corresponding relationship with area of large isentropic potential vorticity values and its moving direction. Related Articles | Metrics

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Analysis of a rainstorm process and its forecast error in Liaoning province LU Zhong-yan,WU Xiao-feng,LI Ping,LI Shuang,HUANG Ge,MA Hong-xu 2014, 30 (6):  31-36.  Abstract ( 479 )   PDF (4573KB) ( 287 )   Save  Falling areas of rainstorm and local heavy rain affected by high trough and North Chain cyclone were summarized. Based on the conventional ground observation data, intensive automatic weather station data, radiosonde data and the European Centre for Medium Range Weather Forecasting (ECMWF) numerical weather prediction products, weather situation, physical quantity field of a rainstorm process on July 29-31, 2011 were analyzed. The results show that forecasting for summer rainstorm considers not only large scale circulation such as high situation, subtropical high intensity and position and so on, but also mesoscale and small scale weather system that is easy to form under favorable large scale circulation background. Generation and development of upper level trough and North China cyclone trigger mesoscale cyclone in this process. Thus, intensity and moving path of mesoscale cyclone are the key factors forecasting this rainstorm process. Related Articles | Metrics

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Characteristics of a local short-time rainstorm using V-3θ chart method in Jinzhou area WEN Zhou,ZHANG Fang,YANG Gui-juan,SHI Hong-ting,HU Ming,CHEN Chuan-lei,ZHAO Miao 2014, 30 (6):  37-42.  Abstract ( 613 )   PDF (4573KB) ( 323 )   Save Based on MICAPS3 data, a local short-time severe rainstorm occurred on July 1-2, 2013 in the eastern area of Jinzhou was analyzed using a V-3θ chart method. The results show that this process occurs under the background of northeast cold vortex. In general, it is difficult to forecast a local short-time rainstorm by the conventional synoptic analysis, while a structure analysis method of the V-3θ chart using inhomogeneity and discontinuity of significant pressure layer could reflect vertical motivation of vortex. Thus, it could make up deficiency of conventional rainstorm forecasting. There exists ultra-low temperature on the V-3θ chart in Jinzhou and its upper reaches area before previous 12 to 24 hours of local short-time rainstorm. From the start to the end of this process, tumble is changed from “clockwise” to “anti-clockwise”. Curves of θ, θsed and θ* are changed from left incline in many points to gradual right incline, and instability energy gradually reduces. Water vapor invades from dry layer to wet layer, and then the whole layer changes wet layer. At last, the whole layer becomes dry layer. The above characters mentioned could be of indicative to a local short-time rainstorm in Jinzhou area. Analysis of radar velocity is favorable to judge wind speed and wind direction at different heights, and then judge the “tumble effect”, which can make up shortcomings of low space-time resolution of V-3θ chart. Also, different distribution of underlying surface could change wind speed and wind direction, and further influences "tumble effect”, so this is an important basis for falling area of local short-time rainstorm. Related Articles | Metrics

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Dynamics characteristics of rainstorm division in Guangdong province and analysis of a severe rainstorm process WANG Jian-hong,XU Bi-yu,LIU Gang,XU An-gao 2014, 30 (6):  43-51.  Abstract ( 500 )   PDF (2790KB) ( 435 )   Save According to daily precipitation data from 72 weather stations in the South China area during 2009 to 2013, temporal and spatial characteristics of heavy rainstorms from April to June (pre-summer flooding period) were analyzed by methods of a REOF and a component analysis. The results show that the heavy rainstorm rainfall accounts for 34.6% of total rainfall and the number of annual rainstorm days is over 170 days. By the EOF analysis, the 5 modes of rainstorm area are obtained. Two modes in Guangdong province have higher coefficients than the other modes and have abundant rainfall and stronger rainfall intensity. Using the component analysis, it is found that the rainstorm area in the north of Guangdong province is influenced by westward wind belt system, and mesoscale system of rainstorm is cyclone and deformation field frontogenesis; rainstorm area in the coast of Guangdong province is controlled by subtropical high system, and mesoscale system of rainstorm is low level jet that transfers cyclone shear wind and rotates vorticity to the area and also provide ample moisture from sea surface, so it causes stronger rainstorm in the coast than in the north. There are 14 severe rainstorm (rainfall >200mm) events during pre-summer flooding season in the recent 5 years in Guangdong province, and all of them happened in the coast. Dynamic mechanisms of heavy rainstorm in both areas are different. It is westerlies mesoscale and deformation frontogenesis in the north, while it is subtropical high warm jet system landing and clambering up the coastal land in the coast. SST of off shore provides more latent heat, higher moisture and more active thermal convection environment in the coast than in the north, while sensible heat field show that rainstorm area in the coast could absorb more thermal energy, which is favorable to maintain and strengthen unstable rainstorm process. Analysis of the continue severe rainstorm at Shangchuan island of Guangdong on June 9-12, 2010 suggests that northeast blocking high and subtropical high that extends to west and moves to north both are of similar intensity, so are water vapor flux and convergence of flux divergence. Aslo, barotropic and baroclinic moisture potential vorticity all together are favorable to vertical vorticity development. The above factors are responsible for maintaining the heavy rainstorm process at Shangchuan island of Guangdong province. Related Articles | Metrics

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Characteristics of local rainstorm and its falling area forecast in Tianjin WANG Ying,LIU Yi-wei,HE Qun-ying,LI Ying-hua 2014, 30 (6):  52-60.  Abstract ( 615 )   PDF (2823KB) ( 355 )   Save Based on conventional observed data from 2009 to 2011 in Tianjin, weather systems of 33 local rainstorm processes were analyzed. Atmospheric physical parameters were analyzed statistically before local rainstorm happened, and key points of forecasting under different weather systems were compared. The results show that local rainstorms often occur under four weather systems, namely, Mongolia cold vertex, northeast cold vertex, before or after upper trough. Plenty of water vapor throughout the atmosphere and deep convergence ascending motion on the southeast quadrant of vortex system are main factors of forecasting under Mongolia cold vertex, while low-level moisture conditions and middle-level strong convergence uplift are emphasis of forecasting under northeast cold vortex systems. Dynamic, water vapor and energy conditions under upper trough system are more balanced. However, all kinds of strong convective characteristics are very significant if the local rainstorm happens after upper trough. Diagnosis of falling areas of typical local rainstorms suggests that precipitable water, convection effective potential energy and vertical wind shear between ground to 3 km height are of indicative to falling area of rainstorm, because these three parameters are calculated based on data in Tianjin radiosonde station where temperature, humidity and wind are considered fully. At the same time, the case analysis shows that a TJ-WRF numerical model has a good ability for predicting local rainstorms, and physical parameters calculated by the model can be used to well forecast the local rainfall area. Related Articles | Metrics

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Low-frequency characteristics of heavy rain and its extended forecast during Meiyu season in Shanghai XIN Fei,CHEN Bo-min,SUN Guo-wu 2014, 30 (6):  61-67.  Abstract ( 513 )   PDF (2217KB) ( 378 )   Save  Based on wind field and water vapor field on 700 hPa from daily NECP/NCAR reanalysis data during 2007 to 2013, as well as daily precipitation data at 11 weather stations in Shanghai, cycles of precipitation were analyzed and low frequency information was extracted. Types of precipitation were classified by an empirical orthogonal function method of vector field. The results show that precipitation has a significant 30-50 days cycle during Meiyu season in Shanghai. There exist 4 main accumulation areas for low frequency system during heavy rainfall. Low frequency anticyclones lie in the west of Lake Baikal to Hetao Area, and low frequency cyclones always appear near the ??Okhotsk Sea. Cold air in middle and high latitudes mainly occurs in these two areas. Low frequency anticyclones near the Bay of Bengal and on surface of tropical ocean are two larger source areas of water vapor. The main references of extended forecast are generation and dissipation of significant low frequency system in the areas mentioned above. North air flow controls over Shanghai before the first heavy rain happens during Meiyu season. When low frequency water vapor moves north to near 30°N, the rainy season begins in Shanghai. Low frequency wind field and water vapor field moves to north, which is corresponding with moving of Meiyu belt. When low frequency water vapor is stable near 30°N, the rainy season begins in the north of study area, and then water vapor continues moving to north or remaining, it corresponds with Meiyu belt continuing north or stagnating intermittently. Low frequency meridianal wind and water vapor transport are an indicative signal of extended heavy rain. Therefore, tracking low frequency southerly flow can contribute to forecast strong precipitation in rainy season. Related Articles | Metrics

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Relationships between South Asian High and precipitation in Yunnan region in summer from 1961 to 2012 GUO Zhi-rong,LI Hui-min,SHANG Yi,DONG Li-na,PENG Li-xia 2014, 30 (6):  68-74.  Abstract ( 595 )   PDF (1699KB) ( 398 )   Save Based on monthly average reanalysis data from NCEP/NCAR and monthly precipitation data at 124 weather stations in Yunnan region from 1961 to 2012, relationships between the South Asian High (SAH) and precipitation in summer in Yunnan were analyzed using a correlation analysis method. The results show that relationship between summer precipitation in the southwest of Yunnan region and longitude of SAH main center is a significant negative correlation from 1961 to 2012, so is between precipitation in the south of Yunnan region and areas of SAH. In June, precipitation in the northwest and south of Yunnan region is significantly positive correlated to positions of SAH ridge line as well as main center latitude; precipitation in the southwest of Yunnan region is a significantly positive correlation with SAH main central intensity and a significant negative correlation with SAH main center longitude; precipitation in the middle of Yunnan region is a positive correlation with SAH main center latitude. In July, relationship between precipitation in the southwest of northwestern and southwestern Yunnan region and in the south of study area and SAH ridge line location is positive, while it is negative between precipitation in the west of Yunnan region and SAH main center intensity and between precipitation in the middle and east of Yunnan region and SAH main center longitude. In August, precipitation in the south, east and center of Yunnan region is significantly negative correlated to SAH area. Related Articles | Metrics

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Impact of station density on accuracy of area rainfall under different topography over Haihe River basin WEI Ying-hua,DONG Gao-hong,XU Shu 2014, 30 (6):  75-79.  Abstract ( 487 )   PDF (780KB) ( 505 )   Save Based on hourly precipitation data from conventional weather stations and regional automatic stations over Haihe River basin in flood season from 2011 to 2013, a set of new rainfall data with high network density was generated and this new data is from synthetic weather stations. Effects of station density under different topography on accuracy of area rainfall were analyzed by using area rainfall dispersion coefficient and its ratio coefficient as well as relationship between point rainfall and area rainfall. The results show that station density is an important factor which affects accuracy of area rainfall, and it has different effects on area rainfall under different topography. In water system of mixed topography such as Luan River basin, topography and precipitation are complex, so effect of station density is also the most significant. Area rainfall is overestimated about 2.5 mm using lower density data from conventional weather stations compared with using higher density data from synthetic weather stations, and 12% errors exceed 5 mm. In water system of mountain area topography such as Yongding River, it is more than 1.5 mm, and relative errors reach 80.3%, especially during local short-time precipitation, errors of area rainfall is ten times as large as the true value. Additionally, station density has lower impact in mixed topography such as Beisan River, Nanyunhe River than in Luanhe River, so is in Tuhaimajia River of plain area, and the area with small difference of topography such as Daqinghe River and Ziyahe River. Related Articles | Metrics

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Disaster-causing index of rainstorm and pre-assessment of disaster effect in Liaoning province HAN Xiu-jun,SUN Xiao-wei,LI Shuang,WANG Ming-hua,LI Guang-xia,CHEN Yu,WANG Gui-chun 2014, 30 (6):  80-84.  Abstract ( 432 )   PDF (829KB) ( 445 )   Save Based on rainstorm processes and disaster data in Liaoning proince from 1951 to 2012, characteristics of rainstorm disaster and its assessment were analyzed. Relationship between disaster-causing index and assessment of disaster effect was investigate using a statistic analysis method. The?results?show?that the number of annual average rainstorm days in Liaoning province gradually reduces from southeast to northwest during 1951 to 2012. Frequency of rainstorm disaster gradually increases from the middle to northwest, especially in the western Liaoning province, for example, rainstorm disasters account for 73% of total rainstorm events in Kazuo County of Chaoyang. Rainstorm frequency is high and precipitation intensity is weak in the western of Liaoning province, while it is contrary in other areas. Also, probability of rainstorm disaster with the first and second grades is lower in the west than other areas. Effect of rainstorm disaster on crop and its facilities is most significant. Frequency of affected disaster is the highest in Liaoyang area, and it is 95% of total disaster events. Rainstorm disaster can be divided into three grades, i.e. high area, middle area and low area. Related Articles | Metrics

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Relationship of northeast cold vortex with migration and landing of Loxostege sticticalis (Ls) SUN Hong-yu 2014, 30 (6):  85-91.  Abstract ( 583 )   PDF (1340KB) ( 280 )   Save Based on a migration and capture experiment of marked adults of Loxostege sticticals (Ls) in plant protect station of Inner Mongolia autonomous region on June of 2009, relationship between mark-release-recapture (MRR) of overwinter-generation adults and weather system was analyzed by using information from daily upper synoptic maps (500-1000 hPa isobaric surface maps at 08:00 and 20:00 on June of 2009) and surface synoptic maps with 8 times per day. The results indicate that adults of Ls are involved into northeast cold vortices and fly with air flow along anticlockwise direction in control region after they are released, and their migration direction is close related to weather system. Meteorological factors such as airflow direction, precipitation and wind-speed significantly influence migration and landing of Ls adults. Analysis of both relationships is favorable to understand migratory habits of Ls at the age of fulminant period, while analysis of meteorological conditions of Ls active landing and moving and corresponding early warning index plays an important role in the process of monitoring migration of Ls adults. Related Articles | Metrics

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Numerical simulation of haze weather in the central cities of Liaoning province ZOU Xu-dong,YANG Hong-bin,ZHANG Yun-hai,LIU Yu-che,WANG Hong-yu 2014, 30 (6):  92-99.  Abstract ( 536 )   PDF (3527KB) ( 335 )   Save Based on NCEP/NCAR reanalysis data and MM5, characteristics of weather system during the most serious haze process in winter of 2010 were analyzed in the central cities of Liaoning province. Characteristics of haze weather and daily mean PM10 concentrations in winter of 2010 in Shenyang, Liaoyang and Benxi were simulated by a CALPUFF model. The results indicate that it is weak warm ridge in Liaoning province at 500 hPa geopotential height field, while it is influenced by divergence and downdraft at 800 hPa geopotential height field. Surface wind directions are inconsistent, and they are affected by divergent flow. It has an obvious potential vorticity rising area above the ground and at low altitudes according to the vertical profile of wind field. It has significant inversion temperature at low altitude based on temperature profile from ground to upper level, and the top of inversion layer is lower. PM10 concentrations on December 19 to 21, 2010 in Shenyang, Liaoyang, Benxi diffuse to east, northwest, southeast directions, which is influenced by surface wind direction. In the whole winter, it diffuses to south for mean PM10 concentration. Related Articles | Metrics

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Climate characteristics of haze and its impacting factors from 1961 to 2010 in Sichuan basin GUO Xiao-mei,CHEN Juan,ZHAO Tian-liang,ZHENG Xiao-bo 2014, 30 (6):  100-107.  Abstract ( 653 )   PDF (1221KB) ( 423 )   Save Based on observed data from 122 weather stations during 1961 to 2010 in Sichuan basin, temporal and spatial distribution of the number of haze days and its seasonal and annual trends were analyzed. Relationships of the number of haze days with atmospheric extinction coefficients, wind speed, energy consumption and population and so on were discussed. The results indicate that the number of annual mean haze days at 122 weather stations is 62.5 days from 1961 to 2010 in Sichuan Basin, and the maximum could reach above 100 days for a certain station. The number of haze days has a significant seasonal variation, and its maximum occurs in winter with 28.4 days, and then in spring and autumn, and the minimum is in summer with 2.9 days. Annual variation of the number of haze days is in an increasing trend for 104 weather stations in Sichuan Basin, and there are 71 weather stations passing a confidence level of 99%. The maximum and minimum increasing rates occur in Qiyuan station with 42.0 days per decade and Xindu station with 0.4 days per decade. On the other hand, annual variation of the number of haze days is in a decreasing trend for 18 stations in Sichuan basin, and there are 7 weather stations passing a confidence level of 99%. The most significant decreasing rate occurs in Nanjiang station with -16.7 days per decade. Annual variation of the number of haze days is a positive correlation relationship with atmospheric extinction coefficients, regional energy consumption and population, and is a negative correlation relationship with wind speed. Related Articles | Metrics

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API characteristics and its relationships with meteorological factors in different solar terms from 2001 to 2012 in Beijing JI Cui-hua,WANG Shi-gong,WANG Min-zhen,SHANG Ke-zheng 2014, 30 (6):  108-114.  Abstract ( 545 )   PDF (966KB) ( 474 )   Save Based on air pollution index (API) data from 2001 to 2012 and ground observed meteorological data in Beijing, API characteristics in different solar terms and its relationships with meteorological factors were analyzed. The results indicate that API values in spring and winter from 2001 to 2012 is the highest in Tomb-sweep solar term and Lesser Snow solar term respectively, so air quality is the worst during these two periods. API value is the lowest in the beginning of Autumn of the solar term, so the air quality is the best. The primary pollutant is PM10 from Vernal equinox to Frost fall solar terms, while it is SO2 from the beginning of Winter to Great cold and from the beginning of Spring to Insects awaken solar terms, especially in Slight cold solar term. The air quality in Beijing is influenced by temperature, wind speed and relative humidity. Pressure plays an important role for API from the beginning of Spring to Grain rain solar terms, and relative humidity and sunshine duration are important from the beginning of Winter to Great cold solar terms. API has a significant correlation with mean air temperature and maximum air temperature from the beginning of Summer to Frost fall solar terms. Wind speed mainly affects air quality in solar terms of spring and autumn. Related Articles | Metrics

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Analysis of external source of acid rain in Dalian SONG Yu,HUANG Ting,PU Weng-yao 2014, 30 (6):  115-119.  Abstract ( 544 )   PDF (1474KB) ( 574 )   Save Air parcel backward trajectory during periods with acid and no-acid rain from 2008 to 2009 in Dalian was calculated based on a Hysplit model, and external source of acid rain was analyzed by methods of a conditional probability distribution and a trajectory clustering. The result shows that the external source transported through atmosphere makes a greater contribution to acid deposition in Dalian area. The main source of acid rain owe to near-surface atmospheric transportation comes from the East China coast to Shandong peninsula, passing through north Huanghai Sea or Bohai Sea and its west coast, and the lower-air atmospheric transportation from the inland area of southward and eastward of China and East Asia countries around Japan Sea provides additional sources. On the contrary, source of no-acid rain comes from ocean air mass or northward land air mass. Related Articles | Metrics

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Effects of water stress on stem, plant and yield of winter wheat over North China plain LE Zhang-yan,LIAO Rong-wei,LIU Jing-miao,LU Jian-li,BAI Yue-ming,LIANG Hong,AN Shun-qing,HUANG He 2014, 30 (6):  120-124.  Abstract ( 355 )   PDF (508KB) ( 336 )   Save In order to study effects of water stress on winter wheat yield on the North China plain, field experiments under three levels of soil moisture, namely, severe water stress (≤40.0%), moderate drought (40.1%-55.0%) and suitable water (55.1%-80.0 %) were carried out at Gucheng ecological-meteorological experimental station of Chinese Academy of Meteorological Sciences. The test cultivar was winter wheat (NO.22 Jimai). The results show that a growth period of winter wheat is shortened, and its plant height, leaf area and filling rate decrease under two treatments of severe water stress and moderate water stress. The order of growth rate of plant height under different water treatments is suitable water> moderate drought> severe water stress, so is that of filling rate. More dry-matter is transferred into stem due to soil water stress. Wheat yield will be reduced if wheat is influenced by water stress during growth and development. Compared with yield under suitable water, yield under severe water stress could reach only 69%. Related Articles | Metrics

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Effect of two vertical stratification methods of GPS tomography grid on GPS water vapor tomography result CAO Yu-jing,LIU Jing-miao,LIAO Rong-wei,LIANG Hong,CHU Yan-li,LI Yuan-shou 2014, 30 (6):  125-133.  Abstract ( 419 )   PDF (1414KB) ( 309 )   Save A Global Positioning System (GPS) experimental station network including nine GPS stations in Fangshan district of Beijing was used for a study on GPS tomography grid. Effects of vertical stratification on the water vapor tomography results were analyzed in terms of methods of a vertically uniform and a non-uniform stratification. The results show that GPS water vapor tomography results obtained by two vertical stratification methods are reliable, and they are consistent with observed water vapor from radiosonde stations. However, tomography grid of vertically non-uniform stratification is more accurate compared with the observed atmospheric water vapor distribution, and the results are more precise compared with that of vertically non-uniform stratification, especially for GPS stations with less altitude differences. Thus, the vertically non-uniform stratification method should be chosen for these stations, although two methods both can provide references for the GPS tomography grid in Beijing. Related Articles | Metrics

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Estimation of surface fluxes using flux-variance method over alpine meadow surface on east edge of Tibetan Plateau LI Ying,LU Ping 2014, 30 (6):  134-140.  Abstract ( 373 )   PDF (1108KB) ( 386 )   Save Based on the observed data in 2008 at Litang site over the alpine meadow surface on the east edge of Tibetan Plateau, the temporal variations of surface fluxes measured by an eddy-covariance system were analyzed, and the flux-variance relationships of normalized standard deviations of temperature, water vapor and CO2 concentration as a function of stability parameter were determined. Sensible heat, latent heat and CO2 fluxes were computed by using a flux-variance method, and they were compared with results from eddy-covariance measurements. The results indicate that there is a regular daily variation for surface fluxes, and seasonal variations are also significant. Latent heat flux is greater than sensible heat flux in a rainy season (May to September), whereas sensible heat flux is dominant in a dry season, and CO2 flux is overwhelming during June to September. Under unstable conditions, the normalized variances of the scalars and stability parameter satisfy the similarity, and their universal functions also can be fitted according to the law of “-1/3 fractional power”. Similarity constants of heat, water vapor and CO2 are 1.2, 1.4, and 0.9, respectively. Flux estimations are found to be in good agreement with observation. Among three parameters, estimation of sensible heat flux is better than that of other two fluxes. In general, this method overestimates the sensible heat flux and latent heat flux, while it underestimates CO2 flux. Prediction accuracy of latent heat and CO2 fluxes can be improved if predictions are obtained using the flux-variance method in combination with the measured sensible heat flux. Related Articles | Metrics

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Comparative analysis of three methods detecting inhomogeneity of radiosonde temperature data in China CHEN Zhe,YANG Xu,LIU Liang-ke,HOU Wen-jie 2014, 30 (6):  141-146.  Abstract ( 423 )   PDF (765KB) ( 452 )   Save Combining reanalysis data as a reference series and the detailed metadata of each radiosonde station in China, homogeneity test and corrections were carried out for monthly temperature data at mandatory levels at 123 radiosonde stations from 1951 to 2008 in China using a Pairwise method developed by America National Climatic Data Center, PMFT and PMT methods developed by the Environment Center of Canada. The results show that adjusted values of radiosonde temperature data in China and its trends before and after correction have some differences for three different methods. One of the main reasons is that design of the Pairwise method leads to the weak capability for break points detection if majority regional stations of China change their radiation correction method and update the system simultaneously. Another reason is that the PMFT method cannot remove the climate temperature trend because of no reference series, so some break points cannot be detected. The PMT method combines with reanalysis data, which is more suitable for homogeneity test and correction of radiosonde temperature data in China. The adjusted results show that the statistical characteristics of radiosonde temperature are greater than those of the global scale at the low level, and both are consistent at the high level. Two break points and adjusted values between -0.2 ℃ to 0.0 ℃ have a larger proportion in datasets. After adjustment, the troposphere temperature average over China is warming trend. This warming trend weakens gradually with increase of heights and becomes a weak cooling trend till 100 hPa. Related Articles | Metrics

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Comparative analysis of atmospheric temperature between three reanalysis datasets and radiosonde dataset in northeast and northwest of China ZHI Xing,XU Hai-ming,MI Wei-hong,SU Zhi-xia,DUAN Xiang-suo,TANG Zhen-xing 2014, 30 (6):  147-157.  Abstract ( 500 )   PDF (2397KB) ( 596 )   Save Based on temperature data from radiosonde dataset at 105 stations in China and three reanalysis datasets of NCEP/NCAR, ERA and JRA, the reliability of free atmospheric temperature in the northeast and northwest of China was analyzed by methods of a root mean square error analysis and a trend analysis and so on. The results indicate that in terms of climatological mean, the root mean square error of JRA datasets is lower than that of radiosonde dataset, and it is lower in winter and higher in the northwest of China than in the northeast of China. In terms of annual variance, atmospheric temperature of three reanalysis datasets are close to that of radiosonde dataset in low layer than in upper layer in the northeast of China, while temperature differences between three reanalysis datasets and radiosonde dataset are higher in the northwest of China than in the northeast of China. In the aspect of long-term variance, three reanalysis datasets have comparable ability in reproducing the trend in lower troposphere. Cooling trend in upper layer can be better identified by the NCEP reanalysis dataset in the northeast of China, while it is by the JRA reanalysis dataset in the northwest of China. Related Articles | Metrics

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Comparative study on land surface temperature retrieval using split-window method based on MODIS data QIAO Xiao-shi,SUN Long-yu,FENG Rui,JI Rui-peing,YU Wen-ying,ZHANG Shu-jie,WU Jin-wen 2014, 30 (6):  158-162.  Abstract ( 597 )   PDF (1004KB) ( 335 )   Save Using QIN and SOB representative algorithms for retrieving land surface temperature (LST) based on the MODIS in Liaoning province, both precision and error were analyzed. The results show that LST retrieved by QIN and SOB algorithms has a good linear fitting with the observed air temperature and surface temperature, especially for a SOB algorithm. According to the error histograms, retrieved LST by two methods is close to the observed surface temperature. Errors of the air and surface temperature between ±2 ℃ calculated by two methods are compared, and error ratio of the SOB algorithm is slightly higher than that of the QIN algorithm. Field experiment, being a same resolution with remote sensing data, suggests that mean absolute errors between two the retrieved and observed temperature both are 1.5 ℃. Compared with the LST from NASA website, mean absolute error of the QIN and SOB algorithms are 1.75 ℃ and 1.70 ℃, respectively. Thus, the two algorithms both are suitable in Liaoning province, and the SOB algorithm has less error. Related Articles | Metrics

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Causes of radar height error alarm and its solutions LI Yong,WANG Jing,GAO Lei 2014, 30 (6):  163-168.  Abstract ( 625 )   PDF (2269KB) ( 576 )   Save Combining with a radar height error alarm case in Dalian sounding station on July 26 of 2011, the height error alarm mechanism was analyzed based on its formation mechanism, and reasons of errors and their solutions were summarized. The results show that height errors are caused by pressure "flying spot", incorrect distance tracking tolerance, sidelobe radar tracking, deviation because of lowering the gain arising from "Flying point "tolerance level alarm and ultra poor weather conditions and so on. Causes and solutions of height error are summarized in terms of three aspects, i.e. recurring deviation alarm, occasionally tolerance alarm and special weather-induced tolerance alarm. The results could provide references for aerological sounding. Related Articles | Metrics