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  • THE CALCULATION ALGORITHMS FOR AVERAGE WIND DIRECTION AND THEIR COMPARISON
  • Qiu Chuantao;Li Dinghua
  • 1997, 16 (1): 94-98.
  • Abstract (889) PDF (170KB)(3146)
  • In this paper, four calculation algorithms for average wind direction and their comparison are given, these algorithms include arithmetic, scalar, unit vector and vector. The comparison of the results from these algorithms using the observation data was also made. Results are as follows: the results of arithmetic algorithm enlarge the percentage of south wind, the results of scalar algorithm cause a larger error when wind direction rotation cxceeds 360°. The unit vector has similar results with vector, and does not need wind speed. The unit vector is the best.
  • Estimation of Land Surface Heat Flux in the Heterogeneous Underlying Surface in Jinta Oasis Based on Remote Sensing and Numerical Model
  • MENG Xian-Hong;LV Shi-Hua
  • 2012, 31 (4): 910-919.
  • Abstract (90) PDF (1108KB)(2597)

  • Abstract: The satellite remote sensing retrievals are based on pixel by pixel, but it is quite difficult to obtain some atmospheric parameters such as air temperature and air pressure  using the remote sensing technique and field campaign, while numerical modeling can provide them easily. So, the atmospheric parameters from mesoscale model simulation are corrected using the filed observation and then are applied in the estimation of evapotranspiration using EOS/MODIS data. Validation results show that the estimation error of sensible heat flux decreased 5.8% and error of latent heat flux decreased 5.5%  using the numeric results comparing with  the single observation, all errors are less than 10%, which indicate that the land surface flux could be retrieved successfully  using the SEBS model. Analysis on the distribution of the land surface heat flux displays that the introduction of numericalsimulation improves the description on the characteristics of energy balance in the oasis and the deserts. Latent heat flux is little in the deserts and Gobi, while it is greater in the oasis and water.
  • Baidu(4)
  • Study and Application of Precise Index of Meteorological Drought tothe Loess Plateau in Shaanxi
  • 孙智辉;雷延鹏;曹雪梅;刘志超
  • 2011, 30 (1): 142-149.
  • Abstract (75) PDF (905KB)(2497)
  • Based on the meteorological data including monthly temperature and precipitation from April to October 1959-2008 at 15 weather stations in Loess Plateau of Shaanxi Province, the relative moisture index is calculated. The results show that the Loess Plateau of Shaanxi Province is divided into 5 types by cluster analysis method, namely Yulin, north Yan′an, south Yan′an, west Guanzhong and east Guanzhong, the three seasons are divided from April to October, namely spring (April~June), summer (July~August) and autumn (September~October). The standard of drought grade for region and season is determined using the percentile method. Meanwhile the determined drought index is checked using other 5 stations, the precipitation anomaly precentage, standardized precipitation index and comprehensive drought index in July 2008 and June 2009 are analyzed and compared. The results show that the revised localization relative moistur index is suitable for application in Loess Plateau of Shaanxi. The application of regional weather station data to drought monitoring is realized, and the drought refinement monitoring level is greatly improved.
  • Baidu(18)
  • Research for Length Change of Four Seasonsover China in Recent 47 Years
  • 郁珍艳-;范广洲;华维;周定文;赖欣;刘雅星
  • 2011, 30 (1): 182-190.
  • Abstract (144) PDF (1119KB)(2213)
  • Using the daily temperature data at 599 stations in 1961-2007, the length change trends of four seasons during the past 47 years was analyzed. The results show that throughout the change region of length of seasons are: The spring becomes shorter(-0.8 d·(10a)-1), the summer, longer(3.2 d·(10a)-1), the autumn, shorter(-0.5 d·(10a)-1), and the winter, shorter(-1.6 d·(10a)-1). This trend is different in spatial distribution, namely more obvious in the North of China than in the South, and more obvious in the eastern part of China than in the western part. Summer change is the most obvious, but autumn change has little comparatively. This trend is highly obvious in the North, East China, Central China and South China. In the Southwest of China the summer becomes longer and the winter shorten starts in the 21st century. The Plateau region has a trend that the spring becomes longer and the winter becomes shorter from 1980s. The average annual temperature increases during the past 47 years, the change of the average annual temperature occurs preceding the season length, the average annual temperature has a rather influence on the length change of season.
  • Satellite Retrieval Analysis on Microphysical Property of Thunderstormwith Light Precipitation over the Qinghai-Xizang Plateau
  • 戴进;余兴*;刘贵华;徐小红;岳治国;孙伟;杨馥祯
  • 2011, 30 (2): 288-298.
  • Abstract (51) PDF (1376KB)(2093)
  • Taking three typical thunderstorms with light precipitation over the Qinghai-Xizang Plateau as examples, the microphysical propertiesof the three kind thunderstorms were analyzed, mainly based on the polar-orbit satellite retrievalmethodologies, and the properties and the cause of their formation were briefly investigated, combing the surface observation and reanalysis data from NECP. The clouds are the convective ones, whose basetemperatureis low and close to 0 ℃, 1.5~2.5 km above the surface, which causes the hydrateand the released latent heat in the clouds less than that the clouds of warm base do, this may be the one of the main reasons that few severeconvective disasters occurredover the Plateau. The glaciation temperatureof the clouds is rather high, and the glaciation level rather low, the cloud particles almost glaciateat the temperatureof -20~-25 ℃, it must has connectedwith the larger cloud effective radius (Re) at the cloud base. The main charge layer is between the level where Re reaches 15 μmand the glaciationlevel, its correspondingtemperatureranges from -10 to -25 ℃, and is the coexistentlayer of water and ice. The main body of thecloud develops above the temperaturebelow zero, their precipitation mainly is dominated by the cold cloud process, and the warm cloud is difficultto trigger in them. The growth process participated by ice phase is the main growth mode of cloud and rain particles.
  • Baidu(17)
  • Global, China-Mongolia Arid- and Semiarid\|Areas (CMASA) andthe Details of Precipitation Distribution in Part Regions of CMASA
  • 钱正安-;宋敏红;李万源;蔡英
  • 2011, 30 (1): 1-12.
  • Abstract (134) PDF (1494KB)(2044)
  • In this paper, after the simply review and intercomparison of the global eight major arid-and semiarid-areas have been done, also and the CMASA size, area, name and the some details of the precipitation distribution over part regions of CMASA have been calculated and analysed. The some main conclusions are as follows: There are eight major semi-permanent arid- and semiarid-areas totally in the world. They are the North Africa-, MidwestAustralia-, Central Asia-, China-Mongolia and Midwest America arid- and semiarid\|areas and so on, are mainly located in Africa, Asia and Oceanica. The CMASA is linked together and should be treated as a whole, not in partly. If taking simply the multi-year mean rainfall less than 200 mm and 200~500 mm as the criterions of arid- and semiarid-areas, respectively, then the CMASA covers both the entire Mongolia and north China bording on Daxinganli-Luliangshan a line to the east and the latitude of 36°N to the south, has the totally area of 5×106 km2, with the main body, making up 69% of its total area, and the extremely arid on China side. And it is the homeland of nearly one hundred million populations in China-Mongolia. The CMASA is dry in the middle, something wet on its south- and north-sides. On the China side, the southmost part of Shaanxi is quite humid, with the mean rainfall as much as more than 900 mm, but in the inland hyper arid region, Toksun, the east end of South Xinjiang Basin, is with the rainfall less than 7 mm only; on the Mongolia side, its central and northern part is with the rainfall more than 400 mm; south part, nearly 100 mm; its southwest corner, just 30 mm. The CMASA is a unique mid-latitude, inland dry zone in the Earth. There are four dry centers in isolation in the extremely dry region of the east end of South Xinjiang basin. That is the common impact of the thermal dynamical inducing compensate descent of Qinghai-Xizang Plateau (QXP) topography on the large scale and Fohn effect on leeward side of East Tianshan and Arjinshan orography on the meso-scale. And also there is a obviousextending southward ‘V’ shappeddry valleyon the northeast side of the QXP, that is the impact of thermal compensatedescent of QXP orography as well.
  • A Regional Snowstorm Process in the Eastern Tibetan Plateauin October 2008 and Climatic Background Analysis
  • 周倩-;程一帆;周甘霖;王式功*;尚可政;杨德保
  • 2011, 30 (1): 22-29.
  • Abstract (137) PDF (1175KB)(2004)
  • A very severe and unusual snowstorm occurred in the eastern Tibetan Plateau during 26~28 October 2008. The climatic background, circulation situation and physical diagnostic analysis of this snowstorm are analyzed using MICAPS data, T213 product and NCEP data. The result shows that the 500 hPa circulation situation of the snowstorm occurred in the east of Tibetan Plateau can be classified into three types, namely, north vortex\|south trough pattern, subtropical high pattern of West Pacific Ocean, south\|north trough battern, and the regional snowstorm process is subtropical high pattern of West Pacific Ocean. It also can be seen clearly from the infrared cloud image that the tropical depression from the Bengal Bay is the main influencing weather system of the snowstorm with sufficient water vapor supply. What′s more, the strong water convergence and ascending motion both play a very important role in this extreme climate event.
  • A Projecting Test of Lanzhou Ground Temperature(GT) andPrecipitation Data to "Rule of More Rain in Positive GTand Less Rain in Negative GT"
  • 吴红-;汤懋苍;邵志宏;郭维栋
  • 2009, 28 (3): 581-585.
  • Abstract (67) PDF (823KB)(1976)
  • For the seasonally and monthly precipitation prediction test of \!rule of more rain in positive GT and less rain in negative GT\" ground temperature and rainfall data of Lanzhou in 1954\_2006, we discuss about the impact degree of earthquake and surface ground temperature on the seasonal and monthly rainfall projecting. The same symbol ratio of the rainfall prediction of summer and autumn using spring and summer data reach to 62.5%, this result can preliminarily be applied to prediction operation, but for monthly prediction had no such performence moreover, the result is not good after correction by ground temperature. The ratio of 3.2 m inter\|monthly variable temperature corresponding less rainfall in next month is 72% without the strong earthquake quiet month, this can be used to less rainfall climate prediction. Strong earthquakes of Ms≥6 are intensive stimulating facters of pluvial period in Lanzhou. Spatial representative of monthly precipitation data in Lanzhou is not very high, an average of the relative radius of 0.01 reliability is only about 170 km.
  • Baidu(2)
  • Applicability Analysis of Standardized Precipitation Evapotranspiration Index in Drought Monitoring in China
  • WANG Lin;CHEN Wen
  • 2014, 33 (2): 423-431. DOI: 10.7522/j.issn.1000-0534.2013.00048
  • Abstract (325) PDF (5925KB)(1941)
  • The applicability of Standardized Precipitation Evapotranspiration Index (SPEI) in China has been analyzed. The main aspects of this research comprise goodness of fit test, capability in reproducing history drought events and the comparison between SPEI and Standardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI), both of which are widely used in drought monitoring and analysis. The result of goodness of fit test shows that for the boreal winter and shortest time scales, the precipitation minus potential evapotranspiration series fail to match the presumed Log-logistic distribution in the south of Xinjiang, the northwest of Tibet and the area from North China to Hetao indicating the unreliability of SPEI values. With mentioned exceptions above, for most regions nationwide a good fit between the sample series and the Log-logistic distribution independent of the time scale and the month of the year guarantees the robustness of SPEI computation. Secondly, the comparison between spatial distribution of SPEI and China Historical Drought Dataset in typical years indicates that SPEI has good performance in measuring drought as well as flood. Furthermore, the relationship among SPEI, SPI and PDSI is also analyzed. The correlation coefficient between SPEI and SPI is roughly above 0.8 for different time scales. However, how well the SPEI correlated with PDSI relies on the time scale. When the time scale is less than 10 months, the poor correlation is observed between SPEI and PDSI; when the time scale is greater than 10 months, the correlation coefficient between SPEI and PDSI remains between 0.7 and 0.9. The comparison result shows that if the suitable time scale is chosen, the statistically based drought index, SPEI, has the similar capacity with PDSI which is based on complex soil water balance to describe and monitor drought reasonably. Furthermore, the SPEI has flexibility to adapt to intrinsic multi-scale nature of drought and advantage over simple calculation.
  • Application of AWTP Index to the Agricultural Drought in Guangxi
  • 张凌云-;简茂球
  • 2011, 30 (1): 133-141.
  • Abstract (48) PDF (1043KB)(1926)
  • Based on the daily rainfall data from 1961 to 2007 at 32 stations in Guangxi, the spatial and temporal evolutions of the agricultural drought events in Guangxi were analyzed using the average waiting timefor precipitation(AWTP) as drought index. Climatologically, the equivalent dry period is the longest in autumn, followed by winter, spring and summer. The dominant time scales of the seasonal equivalent dry periodare both interannual and interdecadal changes in spring and summer. In autumn and winter, there also exist remarkable increasing longterm\|trend in the equivalent dry period, in addiction to the significant interannual and interdecadal variations. However, the increasing trend rate of the equivalent dry periodin autumn is the largest in other seasons. The district\|wide drought is a dominant pattern in all seasons in Guangxi. There are higher agricutural drought frequencies in autumn and winter than in other seasons. Under the background of global warming, the agricultural drought frequency has an increasing trend in Guangxi.
  • Study on the Quantitative Relationship between the Heavy Precipitation Process and VIL Product of Radar in Southeast Gansu Region
  • ZHAO Wen;ZHANG Qiang;ZHAO Jianhua
  • 2016, 35 (2): 528-537. DOI: 10.7522/j.issn.1000-0534.2015.00056
  • Abstract (92) PDF (1459KB)(1896)
  • Based on the New Generation Weather Radar data in Tianshui and 1 h precipitation data in Tianshui and Pingliang, this study analyzes the quantitative relationship between the moving average of VIL(Vertically Integrated Liquid Water Content), the movement of VIL and different types of heavy rainfall in southeast Gansu, which found that:(1)1 h precipitation has a lagged relationship with(also known as delayed response to) VIL, where precipitation and VIL are almost synchronous in non-convective precipitation, while precipitation is 15~25 min behind VIL in convective precipitation, and 15~20 min in mixed precipitation. (2)The approaching of a continuous non-zero VIL sequence to a region, which can be a forecasting indicator, is closely related to a 1 h precipitation larger than 1~2 mm which is followed by that for non-convective precipitation and mixed precipitation, or a 1 h precipitation larger than 0 mm which is followed by that for convective precipitation.(3) Once VIL is used as a forecasting indicator, only the continuous nonzero VIL sequence makes sense for forecasting. The value 0-even if appears only once in a VIL sequence-should be used to separate the two independent VIL sequences in forecasting.
  • Wind Power Forecasting over the Typical Complex Terrains
  • LI Yan;CHENG Peipei;LU Yixiong;SONG Yaoming
  • 2015, 34 (2): 413-425. DOI: 10.7522/j.issn.1000-0534.2013.00181
  • Abstract (92) PDF (6472KB)(1845)
  • Jiangsu and Inner Mongolia were selected as typical complex terrains of coastal beaches and inland plateaus,respectively. The wind forecasting system for the typical complex terrain of China are examined bycomparing the two simulation experiments between the two boundary layer parameterization schemes (YSU/MRF) using the mesoscale WRF V3.3.1 (Weather Research and Forecasting) model. The 48 h wind forecasting with 1 km horizontal resolution and 10 min time resolution were performed for Jiangsu and Inner Mongolia in 2010.The WRF/Noah/YSU wind forecasting system was proved to be more accurately on wind characteristics, wind power distribution, and the prevailing wind pattern during the analysis of power spectrum, wind rose diagram, and thewind variation.The WRF/Noah/YSU wind forecasting system has more ability in spring and autumn than in summer, but the forecast error on diurnalwind variation is different for its different terrain.
  • Baidu(4)
  • Analysis on Mesoscale Characteristics of a Rainstorm Process in Southeastern Gansu
  • WANG Baojian;KONG Xiangwei;FU Zhao;HUANG Yuxia
  • 2016, 35 (6): 1551-1564. DOI: 10.7522/j.issn.1000-0534.2015.00114
  • Abstract (113) HTML PDF (23191KB)(1840)
  • A rare torrential rainfall process which show the long lasting, strong concentrating and obvious mesoscale characteristics attacked southeastern Gansu province on 19-20 June 2013. This rainfall process consisted of 76.8% warm-area precipitation and low-level shear line precipitation. The causes of torrential rainfall and characteristics of mesoscale system are studied in detail by using conventional and unconventional observation data, NCEP reanalysis data, satellite data and Tianshui radar data. During the period of warm-area precipitation, it shows that the related circulation patternare similar to the typical circulation patternin this area. However, thelow-level wind shear shifts westward and the rainfall area isaffected by the warm air. High temperature and high humidity in the low level reduce the LCL and LFC height and weaken the lifting condition, corresponding withthecold trough in the middle level and then forming theunstable stratification. Besides, the low-level temperature inversion in the early stage isalso conducive to the accumulation of unstable energy. On the other hand, the low-level vertical wind shear, jet stream, and the effect of terrain elevation arelikely to play an important role in triggering and maintaining the convection there. The Strong convectioncorrespondsto the low-level jet stream. The convective cells mainly generateoverthe Huixian-Chengxian basin. The mesoscale convective system showthe characteristics of warm cloud precipitation, low-mass center, high efficiency, backward propagation and train effects. During the period of low-level shear line precipitation, the Wudu vortex located overthe northeast Qinghai-Xizang Plateau developsand strengthensdue to the warm advection, positive vorticity advection in the middle level, and low-level cold air intrusion. Besides, the thickness of wet layer increasesin the troposphere, and the thermal instability condition diminishessignificantly. As a result, the low-level shear line, vortex, and the ground convergence line formthe synoptic-scale upward movement, causing a wide range of stability precipitation. For both the warm-area precipitation and low-level shear line precipitation, there showthree obvious water vapor transportation channel in the lower troposphere:around the east of the Qinghai-Xizang Plateau from the bay of Bengal, through Central China from the South China Sea, and through East China from the east coast. Warm and moist air areconstantly transported to the torrential rainfall area from the tropical and subtropical and result thewater vapor convergence.
  • Publication Trends of the Journal of Plateau Meteorology in 1982-2011 -----Results and Enlightens Based on Bibliometric Analysis
  • NING Bao-Ying;SONG Min-Hong;SHEN Qiao-nan;ZHANG Jing-Hui
  • 2012, 31 (1): 285-293.
  • Abstract (86) PDF (1100KB)(1825)
  • The innovative achievements in basic scientific research and applied basic research are mainly published as articles in related specialized periodical.  The Journal of Plateau Meteorology has been published for 30 years, which is concentrated on Tibetan Plateau, atmospheric science and the related questions. This article uses the detailed bibliographic data obtained from database to analyze the publication trend in 30 years. Through quantificational analysis on articles' number, discipline classification, study area, core-author group, research hot spots, cited number and periodicals, funds, influence factor, annual variation of these indices have been illustrated, so do as the research content and direction, research institutes and researchers′ distribution changes. The result indicated that in recent 30 years, the number of articles published in  Journal of Plateau Meteorology assumes the swift growth tendency, this kind of growth is especially obvious since the implements of knowledge innovation project in Chinese Academy of Science; the related research institutes have the obvious subject relevance, as to location distribution, they are mainly concentrates in the Northwestern Region; Tibetan Plateau, numerical simulation and climate change present the three highest frequency key words, Tibetan Plateau is the highest one during 1991-2010 years, which reflected the research hot spots in  Journal of Plateau Meteorology. The results of bibliometric analysis on citing literatures showed that citing frequency by CSCD and SCI and influence factor enhances unceasingly, which further explains the influence′s increasing. However, the core author group of  Journal of Plateau Meteorology has not really formed because of the new researchers′ jointing and the outstanding ones starting to enhance the international influence by submitting their articles to other related journals with higher influence factor, this proposed the new opportunity and the challenge to the future development of the journal.
  • Interdecadal Change of Winter Snow Depth on Tibetan Plateauand Its Effect on Summer Precipitation in China
  • 宋燕-;张菁;李智才;赵平
  • 2011, 30 (4): 843-851.
  • Abstract (61) PDF (1076KB)(1784)
  • A set of consecutive and long-recorded observational snow depth data with 51 observation stations are obtained through choosing, removing and interpolating original observation data in the Tibetan Plateau during 1961-2006. Using the monthly precipitation and temperature data at 160 stations in China during 1951-2006, which was collected by National Climate Center, through calculating the correlation coefficient, significance test, polynomial trend fitting, composited analysis and abrupt change test and so on, the interdecadal change of winter snow on Tibetan Plateau and its relationship to summer precipitation and temperature in China, and to tropospheric atmospheric temperature, the general circulation and the East Asian summer monsoon under the background of global warming are studied.
  • Baidu(27)
  • Comparisons Analysis on Short-Term Precipitation Between the Radar-Based Extrapolation and the Meso-Scale Numerical Model Weather Prediction
  • WANG Dan;WANG Gaili;LIU Liping;ZHONG Shuixin
  • 2014, 33 (3): 811-822. DOI: 10.7522/j.issn.1000-0534.2013.00038
  • Abstract (141) PDF (5923KB)(1756)
  • The forecast skill of Radar-basedextrapolation model MTREC (Multi-scale Tracking and Forecasting Radar Echoes) which is developed by the state key laboratory of severe weather (LaSW) of Chinese academy of meteorological science (CAMS). The forecast skill of MTREC and a meso-scale numerical weather prediction(NWP) BJ-RUC(WRF-based rapid updating cycling forecast system of Beijing meteorological bureau) were analyzed, base on thefour precipitation events observed by radar networks in Beijing in the summer of 2011. The results show that: (1) In terms of bias, both MTREC and BJ-RUC show overforecast the rain area.The bias of MTREC is stable for the considered four events, while the bias of BJ-RUC is sensitive to rainfall types. (2) In terms of the position of precipitation forecast, the forecast skill of MTREC depends on the scale of rainstorm. Larger scale rainstorm corresponds to higher forecast skill. BJ-RUC performs steadily except thelocal rainstorm event 3. (3) For 0~6 h precipitation forecast, MTREC has more skill than BJ-RUC for the first lead times. There is a cross-over point in time where BJ-RUC starts to have more skill than MTREC. The time of the cross-over point depends on the rainfall types. The larger the rainstorm scale is the later the cross-over point occurs. The results would provide some references to improve short-term quantitative precipitation based on blending MTREC and BJ-RUC.
  • Baidu(9)
  • 陕西关中地区层状云降水及雷达特征分析
  • 李金辉;罗俊颉;梁谷;田显;陈保国
  • 2010, 29 (6): 1571-1578.
  • Abstract (124) PDF (729KB)(1751)
  • The data from three stations of 711 radar located at Guanzhong region of Shaanxi Province from 1998 to 2007 were analyzed, and the daily precipitation with more than 5 mm from 12 climatological stations near the radar stations were also statistically calculated. The main results are as follow: (1) The suitable period for precipitation enhancement in Guanzhong region is from 5 February to 15 November. (2) The stratiform clouds can be classified as stable stratiform clouds and mixed stratiform clouds according to radar echo and synoptic situations. (3) The radar echo characteristics of two kind stratiform clouds are statistically analyzed, including maximum echo strength, height of echo top, thickness of cold cloud, warm cloud and melting layer. (4) In spring and autumn, cold layer thickness is more one time than warm layer thickness for two kinds of stratiform clouds, and the moisture in the clouds is much rich, it is optimal time to implement artificial rainfall using the air\|plane, cannon, rocket.
  • Analysis on Dynamic Diagnostic before and after Typhoon ‘Morakot’ Landing
  • WANG Yong;DING Zhi-Ying;LI Xun;SHEN Xin-Yong
  • 2012, 31 (5): 1356.
  • Abstract (32) PDF (1813KB)(1732)
  • Using the GFS (Global Forecast System) analytical data with 0.5°×0.5° grid intervals, the NCEP reanalysis data with four times a day and the satellite cloud image data, the evolution characteristic   before and after the  typhoon  ‘Morakot’ landing with No. 8 are dynamically analyzed. Based on the diagnostic analysis of tendency equation of disturbed potential vorticity, the result  shows that: Firstly, there exists centers of tangential wind near typhoon center at mid- and low-levels which lead to the intensive area of the horizontal flux divergence of potential vorticity located on the inner side of the center of tangential wind. Secondly, the  negative and positive horizontal flux divergences of potential vorticity at low levels can be employed as a pointer for forecast the  typhoon moving on the sea. Thirdly, the intensive areas of negative vertical flux divergence of potential vorticity offer reference for forecast of  typhoon moving under the p coordinate. Finally, by using the vorticity equation, the principal determinants of the variation of the cyclone  vorticity at mid- and low-levels are discussed. Meanwhile, the important coupling effect of typhoon and southwest low-level jet in coastal region of the South China Sea and Southern China on the structure and routine of this typhoon are also investigated.
  • Characteristics of Troposphere-Stratosphere Transports over AsianMonsoon Region in Summer Based on Aura-MLS Data
  • 陈斌;施晓晖;徐祥德;张胜军
  • 2011, 30 (1): 65-73.
  • Abstract (49) PDF (1091KB)(1731)
  • Firstly, by comparison with the ozone (O3 ) sonder profile, the Aura microwave limb sounder(Aura\|MLS) O3 observation data in the upper troposphere and lower stratosphere were validated. Then based on the Aura\|MLS data of 2005 and 2006, the mainly transport channel from troposphere to stratosphere over Asian monsoon region in boreal summer is analyzed. The results show that the concentration of carbon monoxide(CO) and O3 variations have obvious characteristic of inverse correlation in the upper troposphere and lower stratosphere over Asian monsoon region. The distribution of scatter of CO and O3 appears with a ‘L’ shape. On 100 hPa the air with the characteristic of tropospheric atmosphere is mainly localized over the Southern Asian monsoon region, including south of the Tibetan Plateau, Bay of Bengal, Indian Peninsula, Arabian ocean and Arabian Peninsula areas, which composite the main transport channel from troposphere to stratosphere over Asian monsoon region in summer.
  • Research of Reconstruction and Characteristics of Hazes in Anhui
  • DENG Xueliang;SHI Chun'e;YAO Chen;WU Biwen;YANG Yuanjian;ZHANG Hongqun
  • 2015, 34 (4): 1158-1166. DOI: 10.7522/j.issn.1000-0534.2014.00007
  • Abstract (109) PDF (3509KB)(1728)
  • Based on the data provided by 80 surface observation stations from 1970 to 2009, haze days were reconstructed with the objective distinction method for recent forty years in Anhui and the climatic features of haze were systematically analyzed. Results show that the reconstructed haze days were well consistent with the observed and reconstructed values were often higher than observation, so the reconstructed haze days can compensate the lack of haze observations in some stations. Meanwhile, haze days expressed a notable spatial-temporal distribution feature. In annual variation, the time at the begin of 1980s is a cut-off point and after that time haze days exploded. Then the number and density of haze days both increased continuously with the development of Anhui economy. In spatial, haze days were more in eastern region than them in western region and haze regions gradually expanded to the west and the north. As a result, two high hazes centers were formed in the central region of Anhui and the eastern region of Yangtze River. In season, haze occurs mainly in fall and winter rather than in spring and summer. In particular, the medium degree and high degree hazes are all in fall and winter.
  • Baidu(10)
  • INFLUENCES OF QINGHAI-XIZANG (TIBET) PLATEAU UPLIFT ON THE ATMOSPHERIC CIRCULATION, GLOBAL CLIMATE AND ENVIRONMENT CHANGES
  • LIU Xiao-dong
  • 1999, 18 (3): 321-332.
  • Abstract (238) PDF (449KB)(1717)
  • This paper introduces some important influences of Qinghai-Xizang (Tibet) Plateau uplift on the past global change and up-to-date advances in this field.Previous researches show that Qinghai-Xizang Plateau upheaval plays a key role in the following aspects:(1) the reconstruction of the atmospheric general circulation,including the development of Asian monsoon system and the adjustment of stationary planetary wave;(2) the climate change on the global scale,especially over the Plateau and its neighborhoods,such as drying in the northern midlatitudes,wetting in monsoonal Asia and the global cooling events;(3) the evolution of the natural environment,like the formation of the Loess Plateau northern of China and enlargement of deserts in the Asian continental interior,the development of mountain glaciers and snow cover,the evolution of lakes and drainage systems,and the regional differentiation of ecosystem.Meanwhile,some problems in the present work and the direction for the future research are pointed out.For example,linear and nonlinear impacts of the uplifting,gradual and abrupt changes induced by the Plateau uplift and intercomparison between geological climate records and paleoclimate modeling.
  • Construction and Application of Extreme Rainstorm Probability Prediction Based on Radar Echo Base Data
  • WANG Jianhong;HUANG Wei;WANG Qun;MIAO Chunsheng;ZHANG Zhigang;XU Liangmou
  • 2015, 34 (2): 575-585. DOI: 10.7522/j.issn.1000-0534.2014.00132
  • Abstract (71) PDF (4960KB)(1708)
  • Based on a statistical relation between local Radar echo intensity base data and local heavy rainfall, to find the upstream echo areas that will move to the local raining region in next hour by the regional Lucas-Kanade optical flow method. Meanwhile to analyze the echo features at every scan surface, so that to learn the raining system stretching altitude. By analysis of the temporal and spatial characteristics of dynamic echo areas in current hour with information at scan surfaces every 10 minutes, to build the relation between Radar echo intensity features and local rainfall, then applied it on a predicting method of improved rainfall extreme probability, thus to construct forecast and warning index of extreme rainfall return period in next hour. The results will provide the technique support and professional reference for emergency schemes and strategy and tactics. The whole scheme is based on the Doppler radar echo intensity base data at scanning surfaces and the hourly precipitation data of Jianhu weather station during June, July, August in 2006-2011. Jianhu station is within the scanning area of the radar located at Yancheng . The echo dynamic upstream of the local heavy rainfall system is determined by the regional Lucas-Kanade optical flow method. The statistical probability correlation is calculated between echo intensity classification and precipitation series in day and night by Peirson III and Generalized Pareto Distribution methods. The probability characteristics of return period of graded extreme rainfall and the local extreme rainfall under the echo types are also calculated, then the statistic index is constructed between the radar echo dynamic features including the trend of evolution and the probability of local extreme rainfall in next hour, the index correlation and its test all get to 70%. The index can predict the probabilities of different grade extreme rainfall in return period at local place. It is an optimization method of radar dynamic statistics for nowcasting and warning of the extreme rainstorm in next hour.
  • Study on the Relationship Between Mesoscale Wind Field Changes and Rainstorm Using Windprofiler Data
  • ZHOU Xinyu;LIAO Fei;SUN Guangfeng
  • 2015, 34 (2): 526-533. DOI: 10.7522/j.issn.1000-0534.2013.00188
  • Abstract (112) PDF (5668KB)(1697)
  • By using the windprofiler data, this paper studies the relationship between mesoscale wind field changes and rainstorm. Firstly, it is indicated that the high spatial and temporal resolution data can clearly reveal the effect of mesoscale wind filed changes such as low-level jet and low-level wind shear before the heavy precipitation happens. Before the heavy precipitation happens, the strong wind field and the momentum continuously go downstream, making the low-level positive vorticity increase, with the warm and humid air, trigger the precipitation. Secondly, an index I is designed to represent the intensity and height of the low-level jet, the index will increase rapidly before the heavy precipitation. Thirdly, the low-level vertical wind shear increases significantly, and it plays a significant role in triggering the generation of heavy precipitation.
  • Baidu(4)
  • Review of Forecast Result for China Natural Disaster in 2010
  • LIAO Liu-Feng;TANG Mao-Cang;GAO Xiao-Qing
  • 2012, 31 (1): 144-149.
  • Abstract (101) PDF (790KB)(1681)
  • There are many natural disasters in 2010 in China. The prediction process is summarized based on the disaster(drought/flood/earthquake) forecasting methods which be advanced at the beginning of 2010. The prediction include Yushu microseism on 14 April, continuous drought in southwest of China through autumn to spring during 2009-2010. The severe precipitation of the mid- and lower-reaches of Yangtze River in the flood season which also happened in Qinghai Province, debris flow in Zhouqu which caused by downpour on 7 August. The analyzed results show that the natural disasters, which include drought, flood, earthquake and so on, are related with Benard convection in outer core of Earth. The earthquake process is that the outer core convective fluid uprising the Crust-Mantle layer, so the epicenter maybe is the midpoint of the uplifting and sinking where the horizontal shearing of vertical velocity is the most. The downpour is arosed that the mid-point of two convective uplifting   fluid can constitute a  ‘beat frequency’ effect because of  ‘beat’. The reset (tension) of Crust effects after strong earthquake is the cause of drought. These actions are called as the ‘develop of the deep system below ground’ collectively, so we can distinguish them from the fluid conductivity named ‘Shallow system’ in lithosphere.
  • Baidu(6)
  • Research on Ground-Level PM2.5 Mass Concentration Retrieval Based on MODIS Aerosol Optical Thickness
  • XIA Zhiye;LIU Zhihong;WANG Yongqian;CHEN Hongbin;SUN Mingjiang;JIAO Lu
  • 2015, 34 (6): 1765-1771. DOI: 10.7522/j.issn.1000-0534.2014.00075
  • Abstract (101) PDF (1110KB)(1677)
  • Urban haze is becoming more and more serious in these years, especially in the Yangtze River Delta region, the Pearl River Delta region, the Area of Beijing ferry look forward to and other cities, the PM2.5 particles are the main component. In order to mainly retrieve mass concentration about PM2.5 near the surface using MODIS AOT(aerosol optical thickness) data. Firstly, the comparison analyses between AOT from MODIS and corresponding PM2.5 mass concentration in situ are done, the direct linear correlation coefficient R=0.323. And then R=0.467 improved on the base of elevation correction for AOT and relative humidity correction for PM2.5 primarily. Secondly, the seasonal variations about AOT and PM2.5 in depth are analyzed, find that the correlation is highest in autumn, 0.802, and lowest in spring, 0.252, and other seasons are between them, and analyzing the effect mechanism from AOT and PM2.5 themselves' physical and chemical features and meteorological factors to the both correlativity. In the end, a logarithm reversion model about PM2.5 mass concentration coupled with the elevation and relative humidity correction is constructed, the RMSE is 2.84% and mean error is 9.53% respectively, compared to ground measured data. Studies show that this logarithm reversion model can retrieve PM2.5 mass concentration near the ground effectively using AOT, and provide a new scientific basis for PM2.5 reversion by remote sensing, and also valuable for haze detection.
  • Evaluation and Projections of Permafrost on the Qinghai-Xizang Plateau by CMIP5 Coupled Climate Models
  • CHANG Yan;LYU Shihua;LUO Siqiong;WU Jing;LI Ruiqing;LI Suosuo
  • 2016, 35 (5): 1157-1168. DOI: 10.7522/j.issn.1000-0534.2015.00090
  • Abstract (94) PDF (4718KB)(1666)
  • As an important forcing factor of the land surface, permafrost is very sensitive indicator of climate change. The freeze-thaw process is directly involved in local energy and water cycles, and in turn affects weather and climate. In this study, using the multi-model results from the fifth phase of the Coupled Model Intercomparison Project (CMIP5), we computed the near-surface permafrost area on the Qinghai-Xizang Plateau (QXP) via surface frost index (SFI) method, and assessed the ability of models to simulate the related climate variables and present-day (1986-2005) permafrost, by comparing with the reanalysis products and the frozen soil map of the QXP. Based on this assessment, the climate models were aggregated by arithmetic mean to project the changes of permafrost on the QXP under the four different Representative Concentration Pathways (RCPs). The results show that the CMIP5 coupled models have some simulation capabilities for permafrost on the QXP. The simulated present-day near surface permafrost distribution is similar to the plateau frozen soil map, with the annual average of permafrost area of 127.5×104 km2 (1986-2005). The prediction results by multi-model ensemble mean indicate that the permafrost appear a degradation tendency on the QXP, especially on the eastern, southern and the edges of northern plateau. The permafrost will shrink from the edges to the north-west inner part of the QXP, and most probably exist only in the northwestern regions by 2099. Using the SFI method, the rate of the permafrost area change under RCP2.6, RCP4.5, RCP6.0 and RCP8.5 scenarios are-2.2×104 km2·(10a)-1, -5.9×104 km2·(10a)-1, -5.4×104 km2·(10a)-1 and -10.0×104 km2·(10a)-1, respectively. In the next 50 years, the permafrost area will decrease about 23.9×104 km2 (20.8%), 33.5×104 km2 (27.7%), 25.6×104 km2 (21.1%) and 43.5×104 km2 (35.3%) under RCP2.6, RCP4.5, RCP6.0 and RCP8.5, respectively. The average values of permafrost area in the last period of 21st century are about 91.4×104 km2 (RCP2.6), 70.9×104 km2 (RCP4.5), 72.8×104 km2 (RCP6.0) and 41.7×104 km2 (RCP8.5). Although there are large ranges in degree of degradation for different scenarios, the linearity of relationship exist between the permafrost area and the surface air temperature.
  • Baidu(4)
  • Numerical Simulation of Land Surface Process at Different Underlying Surfaces in Tibetan Plateau
  • LI Yan;LIU Xin;LI Wei-Ping
  • 2012, 31 (3): 581-591.
  • Abstract (42) PDF (1440KB)(1649)
  • The simulations of  typical land surface processes at three stations in the Tibetan Plateau are evaluated using Common Land Model (CoLM). The three observation stations are affiliated to the Institute of Tibetan Plateau Research, Chinese Academy of Sciences: Southeast Tibet station, Namco station and Qomolangma station. The offline validation experiments were conducted with the observation data from 2007 to 2008. Default soil porosity and hydraulic conductivity of saturated soil in CoLM are adjusted according to the analyzed  soil samples from Southeast Tibet station and Namco station. Vertical soil layering scheme in CoLM is also adjusted to a shallower height according to the soil samples. The results indicate that after the adjustment of soil layer scheme in CoLM, the model can simulate the soil moisture distribution at three stations more reasonably. The average deviation of the simulated soil moisture decrease 0\^014 or even more. However, there are still biases comparing with the observation: The simulated soil moisture is less than the observed at Southeast Tibet station, but more at Namco  and Qomolangma stations. As to simulations of soil temperature, net surface radiation, surface sensible and latent heat flux, the bias is reduced after the adjustment of soil layer scheme, especially the simulation of surface latent heat flux.
  • Baidu(37)
  • 2007年夏季我国西北地区云凝结核的观测研究
  • 赵永欣;牛生杰;吕晶晶;徐杰;桑建人
  • 2010, 29 (4): 1043-1049.
  • Abstract (56) PDF (722KB)(1630)
  • 利用连续气流纵向热梯度云凝结核仪对我国西北地区2007年夏季空中和地面的云凝结核(CCN)进行观测研究, 并对观测结果进行了对比分析。飞机观测资料表明, 西北地区的CCN主要来源于地面, 近地层浓度较高, CCN浓度随高度增加而减少。污染城市上空的CCN比一般地区上空浓度高, 浓度随高度变化趋势相同; 地面观测结果显示, CCN具有明显的日变化, 与人类活动、 气象因子和下垫面相关; 污染地区和清洁地区的CCN浓度在相同过饱和度下差异很大, 在低过饱和度下浓度相差可达一个量级、根据关系式N=CSk拟合得到的地面CCN活化谱参数, 银川地区的C值明显较大(>2200), k值较高(约0.7), 表明银川地区具有大陆性特征; 而祁连山地区C值较低(<2200)、 k值较高(约0.77), 属清洁型大陆性特征。
  • Calculations of Planetary Boundary Layer Height and Its Relationship with Particle Size Concentration in Xi’an City
  • DU Chuanli;TANG Xiao;LI Xingmin;CHEN Chuang;PENG Yan;DONG Yan;DONG Zipeng
  • 2014, 33 (5): 1383-1392. DOI: 10.7522/j.issn.1000-0534.2013.00077
  • Abstract (170) PDF (4627KB)(1624)
  • Using sounding data, surface meteorological data and particle size concentration, the planetary boundary layer height(PBLH) was calculatedand its change characteristic with particle size concentration were compared. Diurnal and seasonal PBLH variation characteristics are based on Nozaki method which is evaluated by Liu method, daily maximum and minimum PBLH are determined by Holzworth method. Results show that:Nozaki method is valuable for the diurnal and seasonal variation of PBLH though substantially overestimate stable boundary layer which can be compensate by Holzworth method. Daily maximum PBLH occurs during 11:00(Beijing Time, hereafter the same)to 16:00, and seasonal maximum PBLH is during spring attributing to annual maximum wind speed. PM2.5, PM1.0 and PM10 mass concentrations are negatively correlated with PBLH for interannual, annual, and seasonal time scale. Content of PM2.5 in PM10, PM1.0 in PM2.5 and PM1.0 in PM10 show notable monthly variations indicating Xi'an city also affects by upwind windy and dusty weather besides local pollution sources.
  • Relationships between North Indian Summer Monsoon and Midsummer Rainfall in Hetao and Its Vicinity Regions of China
  • LI Dongliang;ZHANG Qian;YAO Huiru;LI Xiao
  • 2016, 35 (6): 1512-1523. DOI: 10.7522/j.issn.1000-0534.2016.00075
  • Abstract (67) HTML PDF (5715KB)(1619)
  • Based on monthly rainfall series of seven homogeneous zones in India and 160 observational stations in China during 1951 to 2006, as well as monthly mean reanalysis data from NCEP/NCAR and NOAA, the relationships between rainfall in each subregions over India and China are investigated. The results show that rainfall in July and August over the northwest and north mountains of India and Hetao and its vicinity areas (Hetao for short) of China exhibit a significant positive correlation, thus defining the midsummer rainfall of the northwest and North Mountains of India as North Indian summer monsoon (NISM). To further reveal the relevant mechanism of the NISM on the rainfall of Hetao, we discuss the relation from two aspects of teleconnection and water vapor transport. It is indicated that when the NISM is strong, Hetao is controlled by the southerly stream in front of abnormal depression, which is located to the southeast of Lake Baikal and tilts westward with the increase of altitude. In addition, the enhancement of NISM also induces the reinforcement of water vapor transporting to Hetao, which is favorable for more rainfall there than normal, and vice versa. Strong/weak NISM is often companied by a La Niña/El Niño event. Eastern equatorial Pacific anomalous SST plays an important role on Hetao rainfall through NISM, while NISM is still significantly correlated with the rainfall of Hetao after excluding the effect of eastern equatorial Pacific SST anomalies.
  • Baidu(1)
  • DESIGNING PHOTOCHEMICAL SMOG POLLUTION REGIONAL TOTAL CONTROL SCHEMES BY USING EKMA DIAGRAM
  • LI Bing;CHEN Chang-he;YU Jin-xiang
  • 1998, 17 (2): 111-119.
  • Abstract (149) PDF (313KB)(1618)
  • Because the principal composition of photochemical smog-ozone is secondary pollutant, the control scheme to primary pollutant isn't applicable to ozone. With EKMA diagam, daily maximum ozone concentrations are controlled by cutting down precursors NOx and HC emissions. Thus, photochemical smog can be controlled by total air pollutant emission control(or total control). There is serious photochemical pollution in Xigu industrial area of Lanzhou, so we take this area as our first attempt of O3 control in China. In this paper, photochemical mechanism and related parameters are given, the process of making and using method for applying EKMA diagram is described in detail. Therefore, the key to ozone control strategy,namely the relationships between emissions and air quality are solved and NOx,HC reduction schemes are put forward. Model results show the schemes can reduce maximum ozone concentrations obviously to the national standards and the best scheme is determined by economic condition feasibility.
  • Planetary Wave Activity and Its Impact on Different Types of SSW Events
  • XU Luyang;CHEN Quanliang
  • 2016, 35 (5): 1389-1400. DOI: 10.7522/j.issn.1000-0534.2015.00051
  • Abstract (106) PDF (4463KB)(1603)
  • Based on the criteria of WMO (World Meteorological Organization), 52 SSW (stratospheric sudden warming) events during 1957-2002 were firstly classified into two types:31 major warming and 21 minor warming events, then 31 major warming events were divided into 20 vortex displacement events and 11 vortex splitting events according to their forms of vortex. Using the ERA-40 daily reanalysis data from ECMWF, composition analysis was used to study these three types of SSW events from 1957 to 2002, including 20 vortex displacement major warming, 11 vortex splitting major warming and 21 minor warming events. The changes of stratosphere of these three were studied, and the anomalies of lower stratospheric planetary wave-number 1, wave-number 2 and the corresponding EP fluxes during the sudden warming period were also interviewed in detail. The results showed that the vortex displacement major warming offsets its low temperature center and the vortex, and reverses wind field of high latitude from westerly to easterly wind. The vortex splitting type splits its low temperature center and the vortex, and reverses wind field of high latitude into easterly wind as well as the vortex displacement event. Minor warming events only offsets its low temperature center, the vortex and wind field of high latitude remain stable. For all these three SSW types, the amplitude of wave-number 1 anomalously increases before the sudden warming and the amplitude of wave-number 1 reaches its climax when the warming occurs, but the climax reaching date and the degree of amplitude increase is different according to the different types. The vortex displacement events and minor warming events remain its climax of amplitude of wave-number 1 for approximately 6~8 days, while the vortex splitting type decreases its amplitude of wave number 1 when the warming occurs. As to the wave-number 2, the vortex displacement type and minor warming events are alike, the amplitudes increase before the sudden warming, and then decrease when the warming began. The vortex splitting type increases its amplitude of wave number 2 after the warming begins. The EP flux of wave-number 1 and wave-number 2 were also calculated and analyzed. The minor warming type and vortex displacement type both have strong upward wave-number 1 EP flux, but the vortex displacement type is stronger, these strongly uploaded EP fluxed of wave number 1 causes the strong increase of the amplitudes of wave number 1. However, the upward wave-number 2 EP flux of these two types is much weaker. For the vortex splitting type, the upward wavenumber 2 EP flux is quite strong, which leads to the increase of the amplitude of wave number 2.
  • Diagnostic Analysis of the Effect of ThermalInhomogeneous Field on the Hail
  • 刘一玮;寿绍文;解以扬;王雪莲;吕江津;贾惠珍
  • 2011, 30 (1): 226-234.
  • Abstract (131) PDF (1351KB)(1586)
  • Using the new data which are combined by the data from Automatic Weather Stations(AWS) in Tianjin and the data above 850 hPa in Beijing, a hail case in Tianjing before dawn of 27 August 2008 is diagnostically analyzed. The hail is observed in two areas, in which is Jixian mountain, other is Hangu area that is near to the sea. Through the research on the thermal and dynamic parameters, the results show that: (1) Using the new sounding data, the calculated convective parameters can reflect the distribution of the characteristics of the severe mesoscale convective weather, especially, the high value area of CAPE and low value area of LI is well correspording to occurrence area of severe convective weather. Besides, it shows that the thermal and dynamic characteristics in the boundary layer are significant to the short\|time nowcasting of the local severe convective weather. (2)The thermal parameters of CAPE (LI) in Hangu area are increasing (decreasing) with time and it is opposite to the phenomena in Jixian area. This phenomena show that there is more significant difference in the reasons of causing the hail between those two locations. The former is dominated by thermal effect while the latter is not. In Hangu area, the reason is that the inhomogeneous distribution of thermal effect causes secondary circulation and upward motion, so that water vapor condense and release the heat. Due to the uplift effect of Jixian mountain, the upward system of the eastward movement is strengthened to cause the hail.
  • Analysis of Extreme Temperature Changes in China based on the Homogeneity-Adjusted Data
  • WANG Dai;YOU Qinglong;JIANG Zhihong;WU Wenbo;JIAO Yang
  • 2016, 35 (5): 1352-1363. DOI: 10.7522/j.issn.1000-0534.2016.00019
  • Abstract (84) PDF (4917KB)(1579)
  • Based on homogeneity-adjusted and quality-control daily maximum, minimum and mean temperature data of 693 meteorological stations in China from 1961 to 2014, then divided the area of China into several regions due to the spatial variability of extreme temperature, and analyzed the change characteristic of 11 extreme temperature indices (were defined by World Meteorological Organization) by linear trend and cumulative departure methods. The result shows that an increasing trend occurs on extreme high temperature indices (including extra-maximum air temperature, summer days, warm nights, warm days, a continuous warm stage and the growing season length) in all regions, while extreme low temperature indices (including extra-minimum air temperature, frost days, cold nights, cold days and continuous cold stage) present a decreasing trend, except for extraminimum air temperature, which shows a trend of increase. Among them, the degree of change of extreme temperature indices in night is the greatest (increase of warm nights and decrease of cold nights are the most significant). Furthermore, in most of regions of each index have an obvious trend turning. The turning time of extreme high temperature indices is nearly in 1995 to 1998, while extreme low temperature indices is nearly in 1985 to 1986 and 1995. Extreme high temperature indices show a decreasing/increasing trend before/after turning, but extreme low temperature indices are adverse, except for extra-maximum air temperature that is increased/decreased before/after turning. There is a significant correlation between all extreme indices with average temperature nearly in all regions. The correlation between the threshold indices with average temperature is the most significant.
  • Baidu(3)
  • Monitoring Application of Hailstorm Event with the Observation of Wind Profile Radar and Ground-Based Microwave Radiometer
  • HUANG Zhiyong;ZHOU Zhimin;XU Guirong;ZHANG Wengang;WANG Yu
  • 2015, 34 (1): 269-278. DOI: 10.7522/j.issn.1000-0534.2013.00130
  • Abstract (125) PDF (7046KB)(1567)
  • The evolution characteristics of hail potential conditions, such as mesoscale weather system, wind shear, water vapor, vertical velocity and unstable stratification at Xianning City in Hubei Province on 12 April 2010 were analyzed with wind profiler radar data and ground-based microwave radiometer that were applied to monitoring of hail fall process. Results show that: (1) The hail-fall process initiated during the process of low trough moving eastwardly and cold air moving southwardly. The mesoscale weather system such as southwest jet at middle and low levels, the shear line on 850 hPa, moist tongue and cold front at the ground afforded dynamic, thermal and water vapor conditions. The deep vertical wind shear from 0 to 6 km and the zero elevation at 3.5 km afforded circumstance condition for hail fall.(2)The passage of the low trough between 850 hPa and 700 hPa is about 0.5 hour earlier than hail-fall process. And the influence of the cold front near the ground was 2 hours earlier than low trough on 850 hPa. And the temperature advection between 1400 m to 5000 m changed from positive to zero, then to negative. The warm and wet flow followed air of higher temperature and greater humidity. Cold advection at middle level was beneficial to the development of convectively un-stability. (3) The fluctuation of vertical velocity increased with the height from 0 to 4 km 0.5 hour earlier of hail fall process. The maximum vertical velocity difference could reach 11 m·s-1. It shows that the thermal and dynamical structure in the atmosphere were very different at different level at the convective storm. (4) There existed deep wind shear at the vertical direction all the time from 0 km to 6 km before hail fall. And it was positive and stable calculated every 200 m. At the same time, the maximum appeared about 1.5 hour earlier which was significant to the monitoring and prediction of hail-fall. (5) The relative humidity was less and drier between 5 km to 10 km while it was greater and wetter between 0 km to 5 km before the hail-fall process. It showed three-layer distribution of "wet at high and low levels, dry at middle level". ILW and IWV increased rapidly from 4 mm to about 15 mm and from 40 mm to more than 60 mm respectively. When ILW and IWV reached maximum, the hail-fall initiated. (6) The K index exceeded 35℃ about 6 hours earlier than hail-fall process. The averaged value of CAPE was about 627 J·kg-1 before hail-fall process. Heights of 0℃, -10℃ and -20℃ were at 5 km, 6 km, 7.5 km respectively. The indexes evolution could show the unstability of atmospheric stratification to some extent.
  • Baidu(7)
  • Evaluation of Flood Season Prediction in Southwest Region by The Second-Generation Monthly Dynamic Extended-Range Forecast
  • LIU Jia;XU Jinxia;MA Zhenfeng;WU Tongwen
  • 2014, 33 (6): 1468-1479. DOI: 10.7522/j.issn.1000-0534.2013.00168
  • Abstract (86) PDF (6679KB)(1565)
  • By use of fully coupled retrospective forecasts covering the 28-year period(1982-2009) provided method, the geopotential height fields and precipitation field from the Second-generation monthly dynamic extended-range forecast(DERF2.0) of China National Climate Center, NCEP / NCAR reanalysis data information, and the rainfall data from the 433 stations in Southwest. Based on Anomaly Correlation Coefficient(ACC), Threat Score(TS), Empirical Orthogonal Function (EOF) iteration method, test and evaluation the predictive skill and errors between forecast and observation of southwest regional circulation and precipitation in the flood season forecast skill. The results show that DERF2.0 can predict the circulation field situation, better forecasting capability in southwest flood season average precipitation, especially the forecast skill of 20 d is better .The model can predict the basic spatial pattern and the leading EOF mode. It shows spatial distribution of precipitation southeast and northwest less modal, but different variance contribution rate and the time coefficient from observation. In addition, the forecast skill of model in the average monthly precipitation forecast is better than the average daily precipitation. It shows that the low intensity rainfall has been forecasted better than the high and medium intensity rainfall.
  • Baidu(6)
  • Applicability Analysis of MERRA Surface Air Temperature over the Qinghai-Xizang Plateau
  • CHU Duo;YANG Yong;LUOBU Jiancan;BIANBA Ciren
  • 2016, 35 (2): 337-350. DOI: 10.7522/j.issn.1000-0534.2015.00018
  • Abstract (148) PDF (2312KB)(1550)
  • Atmospheric reanalyses integrate a variety of observing systems with numerical models to produce a temporally and spatially consistent synthesis of data for weather and climate variability studies. Products provided by reanalyises are the objectively analyzed fields over the globe, including regions with minimal observations, and also for fields that are rarely or never observed. In order to evaluate the applicability of MERRA products over the Qinghai-Xizang Plateau (QXP) MERRA reanalysis surface air temperature product T2m with surface observation air temperature from 60 meteorological stations over 30 years from 1981 to 2010 were compared for the seasonal variations and long tern trends of temperature over the QXP. Main results are as follows:(1) MERRA T2m shows very high correlation with observation temperature with a correlation coefficient of 0.76 on average, in which 96.7% of the total stations is significant at the 95% level and 85.0% of the total stations is significant at the 99.9% level. The correlation in winter is better than that in summer. The relatively low correlation coefficients are found at higher latitude regions of northern QXP. (2) MERRA T2m is lower than the in-situ observations in most of stations on the QXP with lower 3.2℃ on average, and is more close to observation temperature in relatively flat terrain and homogeneous surface features in interior and northern region of the QXP while higher bias is found in complex terrain and surface features in the southeastern and southern mountain and river valleys where land-atmosphere interactions strongly affect the physical parameterizations in the numerical models and complex terrain and heterogeneous surface features as well as persistent cloud cover may contribute to these differences. MERRA T2m standard deviation is smaller than observed as well. However, for long term trends the increase in observation temperature (0.525℃·(10a)-1) is well represented by MERRA (0.342℃·(10a)-1) though MERRA underestimates this increasing rate. (3) According to analysis using observation data, it is indicated that the annual mean surface air temperature on the QXP ranges from -5.1℃ to 14.8℃, with 3.6℃ on average. Over the last 30 years from 1981 to 2010, QXP has experienced obvious increase in temperature with 0.525℃·(10a)-1), which obviously higher than 0.29℃·(10a)-1)of China and 0.13℃·(10a)-1) of global warming trends. At seasonal levels, the highest temperature increase occurs in winter with 0.724℃·(10a)-1), followed by spring(0.523℃·(10a)-1) and autumn(0.467℃·(10a)-1), and the lowest increase in temperature is found in summer but it still reaches to 0.389℃·(10a)-1). These 30-year trends of seasonal temperature are well represented by MERRA T2m product although increasing rates are to some extent underestimated. (4) Based on this work and previous comparison study for surface air temperature from NCEP/NCAR, NCEP/DOE and ERA-Interim over the QXP, MERRA T2m has higher correlation with observation compared to these reanalysis products, which means MERRA surface air temperature has some advantage over the QXP compared to other reanalysis data and is one of the better ways to compensate for sparse ground observation network, to implement climate change, energy balance and water cycles related study, and to use initialization fields for regional climate models etc.
  • Baidu(2)
  • Influence of South Branch Trough of Westerlies on Weather of Yunnan Province
  • DUAN Xu-;TAO Yun-;XU Mei-Ling-;LU Ya-Bin-;LIANG Hong-Li-
  • 2012, 31 (4): 1059-1065.
  • Abstract (110) PDF (977KB)(1545)
  • Using the daily surface observationand radiosonde data from 1980 to 2008, the cases of the south branch  trough  of westerlies influencing on the weather of Yunnan Province are investigated. The spatial and temporal distributionsof the south branch trough  of westerlies and   characteristic of influencing on the precipitation of Yunnan are analyzed. The results indicate thattheyearly averaged number occurred south branch trough  of westerlies influencing on the weather of Yunnan is 18.76. The monthly mean numbers from November to May in next year are almost the same. About 5.88% of processes of the  south branch trough will produce the weather from heavy rain  to rainstorm in Yunnan, about 54.83% of  processes will produce the weather from light rain to moderate rain in Yunnan. Other 17.28% of processes will produce the hail weather. The result shows that the advance and retreat of south branch trough are closely related to the  westerly belt circulation, position of subtropical high, the large-orography of plateau, and so on. The intensity of precipitation and occurring of  severe convective weather in Yunnan are determined by the position of the  south branch trough, water vapour transporting, moisture front zone and low-level jet and strong and weak cold air,  and so on.
  • Baidu(17)
  • Development and Preliminary Application of Environmental Meteorology Numerical Model System in Central China
  • BAI Yongqing;QI Haixia;LIU Lin;CUI Chunguang;LIN Chunze;TAN Chenghao
  • 2016, 35 (6): 1671-1682. DOI: 10.7522/j.issn.1000-0534.2015.00086
  • Abstract (108) HTML PDF (2732KB)(1538)
  • In order to support central China environment meteorological prediction services, and protect environment reducing air pollution, the environmental meteorology numerical model system was developed basing on the regional chemical dynamical model (WRF/Chem). It could provide the numerical forecasting product of air quality for regional environment. The system was preliminary applied in numerical prediction of air pollution in Wuhan at present, and was compared with CUACE forecast products. In addition, an air pollution optimal control plan was discussed through this test. The results show that:The numerical simulation results of model system could validate the temporal variation and spatial distribution of the air pollutants concentration inWuhan.The population correlation coefficients and the forecasting effectiveness of PM10, PM2.5, SO2, NO2, CO concentrations were credible, and the mean absolute percentage error (MAPE) was controlled in 20%~40%. The O3 concentration correlation coefficient was satisfactory, but the forecast results appeared positive deviation in winter. Compared with CUACE forecast products of every 3 hours concentrations of six air pollutants in Wuhan from September 2014 to January 2015, WRF/Chem products was better. It means that WRF/Chem was more referential value for the air quality forecast in Wuhan. Furthermore, an optimal adjustment test for air pollution control was tentative discussed by changing hourly emissions of pollution source. It suggests that without reduction of daily total emission, the air pollutants concentration can be reduced to some extent by changing the diurnal variations of the emissions according to the characteristics of atmospheric boundary layer height at different times of the day. In the later, we will collect longer observation data in more cities, and evaluate the accuracy and stability of WRF/Chem system.
  • The Narrow Beam C-Band Dual-Polarization Doppler Weather Radar of NUIST and Its Performance Analysis
  • CHU Zhigang;HU Hanfeng;HUANG Xingyou;WEI Ming
  • 2017, 36 (4): 1072-1081. DOI: 10.7522/j.issn.1000-0534.2016.00081
  • Abstract (130) HTML PDF (1461KB)(1536)
  • A dual-polarization Doppler Weather radar with narrow beam of C-band was installed at Nanjing University of Information Science & Technology. To verify its observational capability and potential applications, high-resolution radar data were comprehensively analyzed. The radial positioning bias was adjusted based on the echoes of the stationary references. Moreover, the differential reflectivity (ZDR) bias was calibrated by the online solar signals. Also, the radar data retrieved from both convective and stratiform precipitation were performed. The results showed that the resonance scattering effect, various precipitation particle information, and non-uniform beam filling (NUBF or NBF) existed. Besides, tilt precipitation structure and possible supercooled water evidences were revealed.