Plateau Meteorology

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28 December 2014, Volume 33 Issue 6   
  • Analysis and Numerical Simulation of Southwest Vortex on Continuous Heavy Rain Processes in South China
  • LU Ping;LI Yueqing;ZHENG Weipeng;LI Ying
  • 2014 Vol. 33 (6): 1457-1467.  DOI:10.7522/j.issn.1000-0534.2013.00137
  • Abstract ( ) PDF (7937KB) ( )
  • Three cases of Southwest vortex heavy rainfall processes occurred in South China are simulated by AREM and their dynamical and thermal characteristics are analyzed in this study. The results show that the atmospheric circulation configuration of which the westerly jet entrance located on 200 hPa, the organized situation of western Pacific subtropical high, mid-latitude short-wave trough and the strong cold eddy in northeast Asia on 500 hPa, and the continuous transportation of warm current from the Bay of Bengal and the South China Sea in the lower levels, favors the eastward movement and development of the southwest vortex and further contributes to the continuous heavy rainfall over South China. The rainfall area is directly related to the vortex location, it mainly occurs to the south of the southwest vortex and extends towards the direction along the moving path of the vortex. The rainfall intensity is closely associated with the isoline gradient of geopotential height in the vortex center area and the wind field strength in the lower layer. Easterly and weak northerly winds locate at the lower levels of southwest vortex, while the southerly winds and strong westerly and weaker northerly winds control the middle and higher levels, respectively, thus it shows a configuration of convergence at lower levels and divergence at high levels for the vertical structure of atmospheric circulation and results in the positive vorticity in the column. The impacts of horizontal advection and convergence mainly confined at the middle and lower levels while the impacts of vertical advection and the twisting action are more important at higher levels. The horizontal advection of convergence is shown to be an important factor in the development of southwest vortex.
  • Analysis on a Heavy Rainfall in Guizhou Province under the Interaction of Two Vortexes
  • CHENG Xiaolong;LI Yueqing
  • 2014 Vol. 33 (6): 1490-1500.  DOI:10.7522/j.issn.1000-0534.2013.00154
  • Abstract ( ) PDF (11998KB) ( )
  • A continuous rainstorm occurred in Guizhou Province from June 24th to June 28th 2012 is analyzed using NCEP data of 1°×1° with 6-hour interval, FY-2E satellite image and automatic observation station data. The results show that: Stable circulation in Europe-Asia at mid-high latitudes and the water vapor from Bay of Bengal and South China Sea provided beneficial conditions for the occurrence and development of the rainstorm. The easterly Southwest China Vortex (SWCV) and the Yun-Gui vortex system which is born in Yunnan-Guizhou plateau couple to strengthen, which causes a heavy rain in Guizhou Province. In the process of rainstorm, the water vapor transport from the southern border of two vortexes makes the greatest contribution to the rainfall, but the water vapor transport from the western border is more important at the early stage of two vortexes development. The mesoscale convective complexes appear in Guizhou Province during the two vortexes approaching and rainfall areas are located in the center of low black body temperature (TBB) areas and high TBB gradient areas. In addition, the persistence and intensity of the precipitation have close relationship with the development and merger of two vortexes. The high generalized moist potential temperature areas and high generalized moist potential temperature gradient areas also can reflect the location of the rainfall zones on the ground.
  • Mechanism Analysis of a Rainstorm Occurred in the Eastern Part of Northwest China
  • WANG Fucun;XU Dongbei;XIU Shaoyu;QUE Longkai;HAN Shupu;GUO Pingping;ZHENG Xuejin
  • 2014 Vol. 33 (6): 1501-1513.  DOI:10.7522/j.issn.1000-0534.2013.00104
  • Abstract ( ) PDF (10866KB) ( )
  • By using the data of sounding and surface intensive AWS, the satellite cloud images and the reanalysis data of NCEP 1°×1°, the forming mechanism of a rainstorm occurred on 23 July 2010 in the eastern part of Northwest China are analyzed. The results show that the eastern part of Northwest China is at the left side of exit zone of the upper level north jet and convergence region of the low vortex and shear-line in the low level, so the coupling of the upper and low level system is easy to form strong ascend movement. The low level southerly air current formed by interaction of typhoon ‘Chanthu' and the subtropical high continuously transports water vapor to the eastern region of Northwest china. During the rainstorm, precipitation rate and rainfall intensity is consistent and the precipitation rate is over 50 mm·h-1 in the strongest period of rainstorm. Under the background of the saddle pattern flow field, the cold and warm air converge in shear lines of the low vortex. The great total deformation zones coincide with the dense belt of equivalent potential temperature isoline, it is conducive to enhance the wet baroclinicity of the low vortex. During the rapid development of the vortex, the vertical vorticity growth mostly come from the twisting term on 500 hPa. The twisting term maximum ahead of vertical vorticity maximum appears, which has the very good instruction significance for rainstorm forecast. The smaller the negative center value of non-equilibrium force of atmospheric motion on 850 hPa is, the stronger the raininess will be.The negative center value of non-equilibrium force of atmospheric motion in the extreme precipitation region is below -10.0×10-9s-2.
  • Detection of Aerosol Vertical Distribution Using Lidar in Lanzhou District
  • ZHOU Bi;ZHANG Lei;SUI Bing;JIANG Deming;CAO Xianjie;LI Xia;LIU Zhixiong
  • 2014 Vol. 33 (6): 1545-1550.  DOI:10.7522/j.issn.1000-0534.2013.00135
  • Abstract ( ) PDF (1458KB) ( )
  • Based on the lidar (CE-370-2) data from 2006 to 2011 which is provided by the team of Semi-Arid Climate and Environment Observatory of Lanzhou University, the vertical profiles of aerosol extinction coefficient (AEC) are analyzed. The results show: aerosols are concentrated below 2 km of which 60% distribute within 1 km; the values of extinction coefficient become high from 00:00(Beijing Time, hereafter the same) to 12:00 with the peak at 12:00, later they become low; the heights of aerosol concentrated distribution in summer and autumn are respectively 3 km and 2.5 km, while 2 km and 1.5 km in spring and winter respectively; in low troposphere (below 2 km) the seasonal distribution of AEC is that the range of AEC is from 0.20 to 0.85 km-1, holding 92% in winter; in spring the range of AEC is from 0.05 to 0.45, holding 88%; in autumn its range is from 0.02 to 0.2 km-1, holding 82%; and in summer its range is from 0.04 to 0.08 km-1, holding 70%; in dust periods, aerosols can penetrate up to 6 km or more higher; in strong dust processes, the height of lidar valid detection is below 2 km; the retrieval of extinction coefficient shows interruptions phenomena. The vertical profile evolvement of aerosol extinction coefficient is consistent with the change trend of atmosphere boundary layer vertical structure.
  • Study of Spatial and Temporal Variations of Sea Salt Aerosol and Its Direct Climate Effect over East Asia
  • ZHANG Ying;WANG Tijian;ZHUANG Bingliang;LIAO Jingbiao;YIN Changqin
  • 2014 Vol. 33 (6): 1551-1561.  DOI:10.7522/j.issn.1000-0534.2013.00106
  • Abstract ( ) PDF (4914KB) ( )
  • Sea salt aerosol (SSA) is one of the most important aerosol components in atmosphere, which plays very important role in atmospheric environment and climate change. The regional climate and chemistry modeling system RegCCMS was further developed and applied to investigate the spatial and temporal characteristics of sea salt aerosol as well as its direct effect. Here we present numerical simulations on sea salt aerosol concentrations and then its direct climate responses in January, April, July and October 2006, representing for four seasons. The annual mean concentration of SSA over ocean areas of East Asia reaches 14.69 μg·m-3. The maximum concentration of 26.27 μg·m-3 occurs in winter, while the minimum concentration of 7.59 μg·m-3 occurs in summer. The results indicate that the spatial and temporal distribution of SSA shows obvious seasonal variation. The high value center of SSA concentration appears in the South China Sea in winter and in the Yellow Sea in summer. The annual direct radiative forcing at the top of atmosphere of SSA in this area is estimated to be -2.35 W·m-2 and -1.17 W·m-2 for clear sky and all sky, respectively. The direct climate effects of SSA lead to cooling over the coastal land and islands. For Taiwan, the cooling is -1.0940 K, -0.0083 K in July and January, respectively. For the coastal land, the coolings in July and January are -0.1330 K and -0.0142 K, respectively.
  • Relationship between Winter Rainfall in South China and Preceding Heat Content Anomaly over Western Pacific Warm Pool and Its Possible Mechanism
  • REN Qian;HE Jinhai;QI Li;ZHANG Wenjun
  • 2014 Vol. 33 (6): 1568-1578.  DOI:10.7522/j.issn.1000-0534.2014.00110
  • Abstract ( ) PDF (8284KB) ( )
  • By using the historical SST data provided by Japan Meteorological Agency, NCEP / NCAR reanalysis data, SST data from Hadley center, and the daily precipitation at wintertime in 19792010 from 753 stations in China, the relationship between winter rainfall of South China and the preceding heat content anomalies over western Pacific warm pool is studied. The results show that winter rainfall in South China is negatively related to the heat content anomalies at 0~200 m over the key area of 6.5°N11.5°N, 160.5°E172.5°E in June and July, thus the heat content over the key area could be regarded as a precursor of the winter rainfall. The difference field of the atmospheric circulation in winter between the cold years and the warm years resembles the regressed atmospheric circulation field against the sign reversal of heat content index defined within warm pool. It is found that there is an anomalous teleconnection on the East Asian coast in the 500 hPa height field, with anomalous low in South China accompanied by cyclonic circulation on 850 hPa and divergence in upper troposphere, and with anomalous anticyclonic circulation near Philippines which significantly enhances water vapor transport to South China. It indicates that the winter rainfall in South China is more (less) in cold (warm) years. In summer, the strong westerly anomalies near the equator in the northern hemisphere results in the development of cold (warm) SST to the west (east) of key area. In late autumn, an anomalous anticyclone centered in Philippines is formed on the west of the cold SST anomalies, which is strengthened during the winter. The anomalous enhanced warm air on its northwest side transport water vapor to South China. At the same time, the anomalous Walker circulation, excited by the warm SSTA in the central and eastern Pacific, has sinking branch in the equatorial western Pacific, strengthening the Philippines anticyclone and rising motion in South China. It is the above processes that lead to more(less) winter rainfall in South China in the years of cold (warm) SST over the key area.
  • Experimentation of Three-Dimensional Variational Data Assimilation of PM2.5 and Its Main Components
  • LIU Hanwei;PAN Xiaobin;ZANG Zengliang;TANG Tingzhao;SUN Tao;SHOU Junming;LI Dalei
  • 2014 Vol. 33 (6): 1599-1607.  DOI:10.7522/j.issn.1000-0534.2013.00133
  • Abstract ( ) PDF (4841KB) ( )
  • A three-dimensional variational system was established rely on the fully coupled meteorology-chemistry model (WRF-Chem) and used to carry a assimilation experiment about the ground-level PM2.5 and its main components: black carbon, organic carbon, nitrate, sulfate in Los Angeles in the west of American. At the same time we compare the area distribution, single station and temporal variations of the output with control experiment and observed. The results show that: This system has a good effect of assimilation, assimilation results and live closer to the site distribution and evolution of the trend in good agreement; take three sites for the evolution of single-point time series and scatter plot analysis, assimilation correlation coefficient increase in more than 0.85, the correlation coefficient selected three sites up to 0.95, the root mean square error has significantly reduced; numerical simulation did not simulate the large value of the center can be reproduced by assimilation; model simulations the low concentration of PM2.5 evolution of trends and values better than the high-concentration values; with the mode of operation, the pre-assimilation results is better, the deviation of assimilation in mid-period and late period and observation increase; modes also exist systematic bias and singularity, these are the areas for improvement mode.
  • Influence of Pacific-Indian Ocean SSTA on Interannual Variation of Summer Precipitation in Shaanxi
  • ZHAO Qiang;YAN Huasheng
  • 2014 Vol. 33 (6): 1608-1617.  DOI:10.7522/j.issn.1000-0534.2013.00126
  • Abstract ( ) PDF (7913KB) ( )
  • Based on the Shaanxi summer precipitation data from 1961 to 2008, NOAA monthly sea surface temperature (SST), NCEP/NCAR monthly global reanalysis data, the relationship between early to the same period in different seasons of the Pacific, Indian Ocean and Shaanxi summer precipitation was analyzed using regression method, SVD method and the cross wavelet analysis method in order to provide clues and foundation for Shaanxi climate prediction. The results show that: The correlation between Shaanxi summer precipitation with central eastern equatorial Pacific and the western Indian Ocean SST in early autumn and winter is positive, and with North Pacific SST is negative. The distribution of SST correlation coefficient is El Niño SST distribution. To the summer over the same year, the significant positive correlation zone move westward to the eastern Indian Ocean and the eastern coastal of China. The significant regions of influence of Pacific-Indian Ocean SSTA on Shaanxi summer precipitation over Preperiod and the same period locate in Guanzhong and the southeast of Shaanxi. The winter Niño3 SST and Shaanxi summer precipitation has the same phase resonance cycle in the 4~5 years scale and Niño3 SST ahead of the Shaanxi summer precipitation change is about 4~6 months. The correlations between East Asia, the South China Sea, Southeast Asia summer monsoon index and Shaanxi summer precipitation and Niño3 SST is all negative. When early Niño3 SST is abnormally high, the East Asian summer monsoon weakened, the Western Pacific subtropical high is stronger and more west, it always appears anomalies southwest wind water vapor transport in southern of Shaanxi, and appears anomalies north wind in northern of Shaanxi Province; the confluence of the warm and cold wind flow in Shaanxi cause more summer precipitation in Shaanxi Province, otherwise summer precipitation in Shaanxi less.
  • Observation Analysis of Local Severe Convection Event in Shanghai on 31 July 2011
  • WANG Xiaofeng;XU Xiaolin;ZHANG Lei;WANG Ping;XU Tong
  • 2014 Vol. 33 (6): 1627-1639.  DOI:10.7522/j.issn.1000-0534.2013.00204
  • Abstract ( ) PDF (14709KB) ( )
  • Considering the peculiar geography of Shanghai, the influences of the complicated underlying surface on the initiation and development of early-afternoon summer convections is an important topic in short-range weather forecasts. Firstly, using automatic weather station observations of Shanghai from 1994 to 2012, the temporal and spatial distributions of the local severe convections and the characteristics of the Urban Heat Island (UHI) in Shanghai summer were studied, after that, using observations from near-surface dense observation network, the role of UHI, sea breeze, lake breeze in the initiation and development of the ‘0731' local severe convection event was analyzed and discussed. The results indicated that the zone of UHI in Shanghai was expanding. The frequency of severe convection in Shanghai summer was increasing and these severe convections mostly occurred in downtown area and regions along rivers or lakes. Due to the Shanghai UHI effects, the boundary layer jet was preserved, the appearance of sea breeze and lake breeze brought moisture to Shanghai area, while the superposition of the UHI effects accelerated the accumulation of unstable energy and the enhancements of the updrafts, once the surface convergence line in downtown area was formed due to the sea breeze effects, the trigger of unstable energy releasing was turned on and the development of the convections was enhanced further.
  • Comparative Analysis on Continuous Two-Day Short Time Strong Precipitation in Huhhot
  • LI Yiping;DELE Gerima;JIANG Jing;JIA Xiaoyan
  • 2014 Vol. 33 (6): 1654-1664.  DOI:10.7522/j.issn.1000-0534.2013.00100
  • Abstract ( ) PDF (10182KB) ( )
  • Short time strong precipitation that appears in Huhhot in continuous two days from 25 to 26 July 2012 was analyzed from circulation background and happening condition and etc by using conventional observation data and non-conventional materials.The results show that: (1) These two processes occur in the circulation of ‘high east and low west’. West Pacific subtropical high and Baikal low are stable maintained, which is favorable for the cold and warm air meets for a long time. (2) The joint action and configuration of the middle-low latitude weather system, the up-down stream system, high-low level and multi-scale system have contribute to this event, among these the meso-small scale system is the main reason of strong precipitation, but the location of main influence system and characteristics of producing factors are different. (3) The whole level humidity condition is better and located in warm region, but convection is relatively weak in the first day; in a while in the second day, convective instability stratification structure appears because of atmospheric stratification of dry and cold in the up and warm and humid in the low, so the convection is comparably strong. (4) These two days' strong precipitation is both the stratiform clouds and convective clouds induced comprehensive precipitation, but the horizontal and vertical scale of first event is larger; in a while convective precipitation happens mainly in the second. (5) From radar data, the reflectivity factor, vertical integrated liquid water content and echo top of the first day are weaker than the second day; there exists a low level jet seen from radical velocity chart; strong reflectivity area appears wide and flake shape can be seen from reflectivity factor, moves toward northeast and expand southward in the first day; while appears narrow range and band shape, moves eastward and expands southward, appears a obvious train effect in the second day. (6) These two days precipitation occurs in the central of Huhhot region which located in the south of Daqing mountain and in the west of Manhan Mountain, so the topography induced updraft motion plays critical role in the process.
  • Influence of CALMET Parameter Adjustment in the XJRUC Coupling of CALMET over Dabanchen-Xiaocaohu Wind Area
  • XIN Yu;CHEN Hongwu
  • 2014 Vol. 33 (6): 1674-1686.  DOI:10.7522/j.issn.1000-0534.2013.00191
  • Abstract ( ) PDF (2274KB) ( )
  • 60 h wind forecasts using the XJRUC system combined with CALMET are validated over a domain centered on the Dabancheng-Xiaocaohu region during 2009 (December) and 2010 (January, April, July and October). Time series of mask data to evaluate the reliability of the forecasting system was used. The results show that the 24 h wind forecasts are slightly better than the 37~60 h forecasts. Higher resolution model system does not seem to always provide better wind forecasts. Generally, wind forecasts with 3 km resolution are better, especially in spring and autumn or afternoon in a day. In the complex terrain region of Dabancheng, wind forecasts with 3 km horizontal resolution are almost the same as that with 1 km resolution, except that 1 km resolution wind forecasts are slightly better in winter. A coaser-resolution wind forecast (9 km) are better in spring when strong wind often occurs at complex terrain and landform area, otherwise, wind forecasts with 3 km horizontal resolution are the generally best. In addition, the author addresses the question of whether configuration of CALMET has significant impacts on the forecast. It is found that the kinematic adjustments in CALMET should be used carefully according to the climatic and synoptic characteristics in the study region. In general, CALMET accounting for the slope flows and Froud number adjustment are the best scheme in the case that the impacts of large-scale circulation on the local wind field characteristic are not sure.
  • Analysis on Characteristics of a Damage Wind Case in Doppler Radar and Boundary Layer across Northern Zhejiang Province
  • TU Xiaoping;YAO Risheng;QI Liangbo;SHEN Yu;SUN Zhang;YANG Hao
  • 2014 Vol. 33 (6): 1687-1696.  DOI:10.7522/j.issn.1000-0534.2013.00092
  • Abstract ( ) PDF (11267KB) ( )
  • Based on the data from the automatic weather stations in Zhejiang Province, two Doppler radars in Hangzhou and Ningbo, Huzhou wind profiler and 370 m tower in Liangmaoshan island in Ningbo, a damage wind case across northern Zhejiang Province during the night time of 2 April 2012 was analyzed. The results show that: Well-organized multi-cell windstorms triggered by the quick-sinking strong cold air mass is blamed for the damage wind in Huzhou, windstorms display as a bow echo in Dopplar radar with 3 well-developed convective cells and MARC structure in base velocity images. Huzhou wind profiler data indicates that the sinking flow causing damage wind begins at the boundary layer below 1 km, it takes only 2 min for the damage wind down from 300 m to the ground. Outflow boundary resulted by a convective cell merges with a southeast-going gust front and causes the damage wind in Jiaxing city. Moreover another gust front results the damage winds in Ningbo and Zhoushan cities. Data of the 370 m tower shows that the lift velocity is enhanced with the maximum up to 1.7 m·s-1 at 318 m but few fluctuations at other levels with the gust front approaching. When the gust front passes by, sinking velocity is firstly observed at the upside of the tower with the maximum one-minute sinking velocity up to 1.81 m·s-1 and the maximum fluctuation ratio of velocity more than 10 m·s-1 within one minute which is centered below 232 m of the tower. Temperature dropping is 1 minute lagged behind speed acceleration, with the maximum 1.6℃·min-1 in the middle level. Dramatic wind and temperature change lasts about 4 min.
  • Analysis of Energy Balance Characteristics on Asphalt Pavement
  • ZHANG Zhongqiong;WU Qingbai;LIU Yongzhi;CHEN J
  • 2014 Vol. 33 (6): 1705-1711.  DOI:10.7522/j.issn.1000-0534.2013.00143
  • Abstract ( ) PDF (2353KB) ( )
  • In order to analyze the differences and the reasons for the heat absorption of asphalt pavement and the natural surface, radiation, wind speed, air temperature, humidity, barometric pressure and shallow ground temperature was observed on the asphalt pavement and natural surface in Beiluhe area on the Qinghai-Tibet Plateau. Evaporation and turbulent heat of the two ground types are calculated using aerodynamic method. The results showed that: From May to September, the net radiation flux of natural surface is greater than the asphalt pavement; at the otherduration, the net radiation of asphalt pavement is greater than the natural surface. The net radiation of asphalt pavement is about 6.2% more than the natural surface. With the use of the asphalt pavement, the difference between them has a decreasing trend. The main cooling way is the turbulent heat in Beiluhe area. Latent and sensible heat flux of asphalt pavement is less than the natural surface; The difference was larger in summer and winter. Compared with the natural surface, the latent heat flux of asphalt pavement reduces by 24.4%, sensible heat flux reduces by 14.3%. Ground temperature at the shallow part of asphalt pavement was significantly greater than the natural surface. In 5 cm depth, ground temperature under asphalt pavement is higher than the natural surface of about 1.15~8.6℃. At 20 cm depth, ground temperature under asphalt pavement is about 0.1 to 5.6℃ higher than the natural surface. The asphalt pavement absorbs more heat than the natural surface, and the roadbed center position is greater than the right shoulder position. The asphalt pavement endothermic role is obvious.
  • Analysis of Influence of Typical Buildings Around Turpan Meteorological Station on Sunshine Hours
  • YE Dong;SHEN Yanbo;DU Jiang;AI Sheng;CHENG Xinghong
  • 2014 Vol. 33 (6): 1712-1721.  DOI:10.7522/j.issn.1000-0534.2014.00051
  • Abstract ( ) PDF (4465KB) ( )
  • Taking Turpan meteorological station as an example, and considering the azimuth and height of six typical buildings surrounding it as well as the distance between the observation field and the six typical buildings, a quantitative calculation method of effects of buildings surrounding the meteorological station on sunshine hours was established. In the concrete analysis, three types of parameters including theoretical influence, theoretical valid influence and real influence were introduced. The results showed that if the focus was confined to astronomical calculations, the theoretical block hours of sunlight by the six buildings were 882.9 h and the theoretical block proportion was 19.9%. The response threshold of sunshine recorder on direct radiation irradiance was further considered. When the circumstance of solar elevation angle of less than 5° was eliminated, the theoretical valid block hours of sunlight by the six buildings were 633.1 h, and the theoretical valid block proportion was 14.2%. When the real weather conditions were considered, the real block hours of sunlight by the six buildings were in the range from 145.4 to 592.7 h and the real block proportion was in the range from 3.3% to 13.3%, according to the present data. Viewed from the independent effect of each building, the valid block proportion of two buildings located on the south side of the observation field was largest for their high height or very close distance. Viewed from the seasonal changes, the solar elevation angle in winter was low and the sunlight was shaded most seriously, followed by the solar elevation angle in autumn, spring and summer. The method can be used to calculate the influence of obstacles surround the national meteorological observation stations on sunshine, and further present a correction recommendation for the observed result of sunshine hours.
  • Algorithm Design of Quality Control for Hourly Air Temperature
  • WANG Haijun;YAN Qiaoqiao;XIANG Fen;PAN Meng
  • 2014 Vol. 33 (6): 1722-1729.  DOI:10.7522/j.issn.1000-0534.2014.00028
  • Abstract ( ) PDF (1479KB) ( )
  • Although range check based on month climatic extremes is one of the most commonly used data quality control methods for Automatic Weather Stations(AWS) data, if it is applied to quality control of hourly air temperature data, there exist two weaknesses: (1) The larger threshold range of climatic extremes can make some abnormal data undetected; (2) Large amount of newly built AWS has no climatic extremes. To improve these weaknesses, a range check method is developed based on hourly threshold, which is computed by day climatic extremes. In order to obtain the lower and upper limits of hourly air temperature threshold, firstly, the principles of time and spatial interpolation are applied to calculate the daily temperature extremes at any site based on the generalized extreme value distribution theory. Then, the computing method of hourly threshold at any site is designed by means of the daily change regularity of temperature and numerical interpolation technology. The daily maximum and minimum air temperature of total 730 AWS in China are applied to design and calculate the lower and upper limits of hourly air temperature threshold which can be used for nationwide. Meanwhile, the punctuality, maximum, minimum air temperature of hourly data produced by 2400 AWS located in the national scale in 2010 are used to demonstrate the effectiveness of our proposed control approach. The results show that the quality control method based on the range check of hourly threshold has a lower undetected rate compared with the daily or monthly climatic extremes check. Especially, it can be adopted by those stations without historical data. Its check results can be strengthened by combining with spatial consistency check to reduce the false detection rate greatly.
  • Beam Blockage Studies of Doppler Weather Radar in Mountainous Region of Zhejiang
  • WANG Hongyan;LIU Liping;HE Liping
  • 2014 Vol. 33 (6): 1737-1747.  DOI:10.7522/j.issn.1000-0534.2013.00173
  • Abstract ( ) PDF (8100KB) ( )
  • Many sites of China new generation weather radar network locate in mountainous regions, where terrain near the radar often causes beam blockage.As an example, actual beam propagation path is calculated based on years of sounding data for Quzhou radar, then using the calculated local beam propagation path, beam blockage is simulated by two processing methods with DEM of different resolutions, 30 m and 90 m.Simulated beam blockage results were verified by contrasting with the probabilityof detection(POD) of radar. The results show that: Normally, the simulated beam blockage agreements with radar observation well; the resolution of DEM and the processing method affects the accuracy of simulation beam blockage significantly if the obstacle is close enough to the radar, the sectionalized-method, the higher resolution of DEM, the more consistent with each other they are. But such is not significant for remoter obstacles. Since the simulated beam blockage is reliable, a method of checking and correcting radar position according to the correlation between it and POD is proposed to resolve the problem of biased or inaccurate position for some radars. Jinhua radar's simulated beam blockage matches actual reflectivity distribution very well after correcting position by this method.

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