Plateau Meteorology

Current Issue

28 April 2014, Volume 33 Issue 2   
  • Characteristics of Vegetation Change and Its Relationship with Climate Factors in Different Time-Scales on Qinghai-Xizang Plateau
  • WANG Qingxia;Lü Shihua;BAO Yan;MA Di;LI Ruiqing
  • 2014 Vol. 33 (2): 301-312.  DOI:10.7522/j.issn.1000-0534.2014.00002
  • Abstract ( ) PDF (7140KB) ( )
  • Using GIMMS NDVI data in the Qinghai-Xizang Plateau(QXP) from 1982 to 2006 and multiple statistical methods, the temporal and spatial characteristics of vegetation change and the relationships between NDVI and climate factors at different time scales (annual, seasonal and monthly) are analyzed. An increasing trend of annual mean NDVI has been shown over QXP. Among all the season, the largest trend of NDVI is in summer, which is about 0.004 per decade. The contribution of different coverage pixel is varied. The pixel change of low vegetation cover dominated the overall change in vegetation, and the largest contribution happens in winter. The pixel change of moderate vegetation cover is significant in autumn, the pixel change of high vegetation cover is more obvious in summer. The change of vegetation cover is not only in temporal, but also in spatial over QXP. The area of increasing and decreasing accounted for 30.51% and 10.52% respectively in summer. Increase region mainly located in the eastern QXP and decrease region located in the northern QXP. With correlation analysis between NDVI and climate factors, the region covered by moderate vegetation has the most relevant to climate factors, followed by the region of high vegetation coverage, and the lowest correlation is in low vegetation coverage area. In the annual and seasonal scales, the cumulative effect of temperature and precipitation controlled vegetation growth in QXP, which is more obvious in vegetation growth well seasons and areas. In monthly scale, vegetation growth in low-moderate vegetation coverage influenced by short-time precipitation events, and the region covered by high vegetation is still dominated by the accumulative effect of temperature.
  • Simulation Influences of Summer Precipitation by Two Cumulus Parameterization Schemes over Qinghai-Xizang Plateau
  • LUO Xiaoqing;YANG Meixue;WANG Xuejia;WAN Guoning;CHEN Xiaolei;LIANG Xiaowen
  • 2014 Vol. 33 (2): 313-322.  DOI:10.7522/j.issn.1000-0534.2013.00177
  • Abstract ( ) PDF (6065KB) ( )
  • The regional climate model RegCM4.0 was used to analyze the impacts of Tiedtke cumulus parameterization scheme and Emanuel scheme on summer precipitation simulation over Qinghai-Xizang Plateau, while JRA25 data and NCEP reanalysis data were used as comparison. The experiment indicated that monthly average precipitation has a complex variation, and precipitation over Southern Qinghai-Xizang Plateau is much larger than Northern. Convective precipitation that accounts for a large proportion in total precipitation, has an obvious daily and monthly variation. Although precipitation simulated by Tiedtke scheme is less than Emanuel scheme, it still has a good performance on daily variation of convective precipitation. Precipitation simulation obviously affected by lower troposphere humidity. Topography has a great impact on water vapor and ascending motion simulation, and except for Southeastern Qinghai-Xizang Plateau where strong ascending motion can reach upper troposphere, the scale of vertical movement in other areas is smaller. The center of Qinghai-Xizang Plateau has net income of water vapor, and the reason why Qilian mountain has more precipitation than surrounding areas is that upper air sinks and lower air rises. The study also revealed that cumulus parameterization scheme based on mass flux has some applicability over Qinghai-Xizang Plateau, but Tiedtke scheme needs great modification, especially to modify the smaller scale convective process for improving simulation ability.
  • Mesoscale Filtering Analysis of a Regional Heavy Rain by Southwest Vortex
  • ZHANG Hong;LI Guoping;WANG Shudong
  • 2014 Vol. 33 (2): 361-371.  DOI:10.7522/j.issn.1000-0534.2013.00016
  • Abstract ( ) PDF (10580KB) ( )
  • By programming a Barnes band-pass filter through conventional data and NCEP data，the mesoscale filtering analysis of a regional heavy rainfall process produced by the Southwest Vortex(SWV) on 14-18 July 2010 and 3-5 July 2012 were done. The case study shows that Barnes band-pass filter could find out the mesoscale weather systems including SWV by choosing the appropriate filter parameters. After filtering and analyzing mesoscale characteristics of stream line, the SWV has four stages：generation，development，disintegration and movement eastward. The mesoscale filtering can better depict the mesoscale circulation characteristics in Southwest regions. The calculating helicity of the filtered data show that the high value of the helicity is conductive to the generation and development of the convective system，as well as vortex.The clearly distribution of positive and negative centers of the filtered local vertical helicity can better reflect prepetition. The rain area occurs in the east of the large gradient values between positive and negative centers of local vertical helicity. Not only local vertical helicity but also integral vertical helicity have a good indication significance in preparations and rainfall intensity changes.
  • Influence of the Position of East Asian Subtropical Westerly Jet in Summer on Precipitation over Sichuan-Chongqing Region
  • YANG Xiaobo;YANG Shuqun;MA Zhenfeng
  • 2014 Vol. 33 (2): 384-393.  DOI:10.7522/j.issn.1000-0534.2013.00034
  • Abstract ( ) PDF (6168KB) ( )
  • Based on the precipitation data at 30 stations over Sichuan-Chongqing region from June to August and NCEP/NCAR reanalysis data of 2.5°×2.5° including the monthly mean geopotential heights and wind fields during recent 50 years, the relationships between the East Asian subtropical westerly jet (EAWJ) in summer and precipitation over Sichuan-Chongqing regiond have been investigated, using the methods of canonical correlation analysis, correlation analysis, and regression analysis. The results are as follows: The latitudinal position of the EAWJ has a significant influence on precipitation of Sichuan-Chongqing region. In detail, the northward EAWJ axis could result in more precipitation in the western Sichuan basin, as well as less precipitation in both the eastern Sichuan basin and the western Sichuan plateau, and vice versa. The correlations between the EAWJ axis and precipitation over Sichuan-Chongqing region take better performance in summer, but weaker in June, July and August. Corresponding to the abnormally northward (southward) EAWJ axis, the South Asian high inclines to more westward (eastward) position, while the western Pacific subtropical high tends to more eastward (westward) position. Meanwhile, the ridge line of the western Pacific subtropical high tends to more northward (southward) position, as well as smaller (larger) area of the South Asian high and the western Pacific subtropical high. Those anomalous configuration patterns of the lower and higher circulation result in variability of precipitation over Sichuan-Chongqing region. The inter-decadal change of latitudinal position of the EAWJ is one of the main factors that cause the reverse distributions of precipitation for the periods 1965-1982 with respect to 1983-2006 over Sichuan-Chongqing region. Especially, both the eastern Sichuan basin and the western Sichuan plateau changed from less to more, and the western basin obviously decreased.
  • Comparison between Two Rainstorm Meso-scale Vortices Circumambulated Respectively from Two Sides of Mountain Dabieshan during Meiyu Season
  • MIAO Chunsheng;LIU Weixin;WANG Jianhong;WU Min;LI Ting
  • 2014 Vol. 33 (2): 394-406.  DOI:10.7522/j.issn.1000-0534.2013.00195
  • Abstract ( ) PDF (8179KB) ( )
  • A statistic analysis of rainstorm vortices during Meiyu seasons from 2007 to 2011 at YangtzeHuaihe River basin shows that the low vortex rainstorm is up to 41% in all rainstorm day during the statistical period, and most of the rainstorm vortices are shallow vortices (under 700 hPa), so they are easy to be impacted by the Dabieshan mountain (about 1500 m height). Two rainstorm vortices are analyzed when they circumambulate and climb the Dabieshan mountain from south along Yangtze River Basin and from north along Huaihe River Basin, respectively under both influences of mountain and steering current of trough foreside at high level. The shallow vortices go round the mountain from two sides with north stronger than south one, and cause their rain zone positions difference along Huaihe River basin and along Yangtze River basin respectively. Meantime the wind shear structure of high level jet and the low level jet together increase the cyclone vorticity of the shallow vortices and indicate the eastward paths and positions of low vortices. Meanwhile, the low level jet also responses to the mountain hindering，the weak low level jet is weaken and shows a circumambulated state to the mountain by blocking of the south part of Mountain Dabieshan. The circulation state causes a weak growing of both vortex and rainstorm intensities at south end than strong growing at north end of Mountain Dabieshan. The distribution of the moisture potential vorticity of vortex rainstorm shows that at vertical-longitudinal cross-section the baroclinic and barotropy gradient areas overlap each other and make a strong rainfall environment，the moisture potential vorticity is proportional to the intensity of rainfall，and the Huaihe River Basin vortex has stronger moisture potential vorticity as there is stronger vertical wind shear at north part of Mountain Dabieshan. The numerical simulation shows that the Dabieshan mountain topography remarkably impacts on the low vortex circumambulated paths from south or north, the low vortex intensity increases at leeward or decrease at windward, and moisture flux convergence strong or weak with vortex intensity. The topography effect causes the center position of low vortex, moisture convergence and rainfall easily close or overlap at two key areas (face-wind side of the mountain south part and the lee-ward arc area of mountain north part), where the air vertical stretched, moisture convergence strengthen and the rainfall of the vortex rainstorm are special heavy. Due to the south part of the mountain is larger and higher than the north part, the topography impact on the south vortex along Yangtze River Basin is more obvious.
  • Applicability Analysis of Standardized Precipitation Evapotranspiration Index in Drought Monitoring in China
  • WANG Lin;CHEN Wen
  • 2014 Vol. 33 (2): 423-431.  DOI:10.7522/j.issn.1000-0534.2013.00048
  • Abstract ( ) PDF (5925KB) ( )
  • 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.
  • Existence of Generalized Energy about a Navier-Stokes Operator Equation
  • LIU Chun;LIU Sibo;ZHANG Chunhui;GUO Sasa
  • 2014 Vol. 33 (2): 467-473.  DOI:10.7522/j.issn.1000-0534.2012.00190
  • Abstract ( ) PDF (381KB) ( )
  • The equations are reduced to nonlinear operator equations of Hilbert space by using functional theory, based on each variable Hilbert space of the general system of atmospheric Navier-Stokes dynamics equations. Thereby, considered the equation for the overall characteristics on this basis, using necessary simplification, the underdetermined partial differential equations are reduced to nonlinear partial differential equations about generalized energy. Because of the nonlinear properties of the partial differential equations, the existence of weak solutions is attempted to consider. According to the analysis, in the turbulent closure process, if the nonlinear coefficient of the generalized energy equation has characteristics of strongly elliptic, according to the projection method of the continuous normal operator equations, that nonlinear partial differential equations of generalized energy has a projection determined, which approach the weak solution, while the external force is known or fixed. In last, the existence of weak solutions for generalized energy is obtained. On the movement of atmosphere, its energy conservation is important. Therefore, conserve-ation of generalized energy is discussed. And the conditions of reaching the conservation of general-ized energy is obtained in the last of this paper.
  • Research of the Distribution of National Scale Surface Roughness Length with High Resolution in China
  • LI Qinyi;CAI Xuhui;SONG Yu
  • 2014 Vol. 33 (2): 474-482.  DOI:10.7522/j.issn.1000-0534.2012.00191
  • Abstract ( ) PDF (3813KB) ( )
  • The normal methods of calculating the surface roughness length were summarized, both with and without observation. In addition, some widely used ways of deriving surface roughness length with remote sensing data were presented as well. The high resolution global land cover data based on satellite observation published lately by European Space Agency (ESA) was utilized to study the distribution of surface roughness length in China. The relationship between ESA land cover categories and surface roughness length was established, which referred to the schemes assigning surface roughness length according to land cover categories used in two common meteorology models—CALMET and WRF, and was utilized to produce the distribution of surface roughness length about 300 m resolution at national scale of China, and comparised with the observation data published by other researchers. The results show that: (1) ESA land cover data could reflect the fine space distribution of surface roughness length but failed in the roughness changes in urban area. (2) The surface roughness length values based on the mapping relationship used in CALMET model were systematic high. (3) The surface roughness length values based on the assigning relationship used in WRF tended to be more reasonable and more consistent with the practical observation, including the seasonal variation of surface roughness length.
  • An Objective Verification of Forecasting Ability of Japan High-Resolution Model Precipitation in China
  • PAN Liujie;ZHANG Hongfang;WANG Jianpeng;NING Zhiqian
  • 2014 Vol. 33 (2): 483-494.  DOI:10.7522/j.issn.1000-0534.2012.00188
  • Abstract ( ) PDF (7999KB) ( )
  • Based on objective statistics, using precipitation data collected every 6 h at 2419 stations from 1 April to 31 August 2012, and hourly rainfall data fusion by CMORPH(NOAA Climate Prediction Center Morphing Method)satellites and more than 30 thousand automatic stations, Japan high resolution mode precipitation forecasting abilities in China by every 6 h, 12 h and 24 h segment was tested. The results show that: (1) Rain or shine forecast skill scores gradually increases with segment intervals increasing, torrential rain forecast skill scores have better performance at 12 h segment than others. (2) On station verification, the precipitation frequency of model rain or shine forecasts is higher than observed frequency, while the 6 h, 12 h segment torrential rain forecast is lower than observed frequency. But for 24 h segment, the torrential rain forecast frequency basically agrees with the observed one. By changing threshold values, forecast skill scores can be improved. (3) 6 h fractional precipitation standard deviation rations are <1, so the more probability of moderate rains are forecasted but heavy or light rains appears, but for 24 h, the case is on the contrary. (4) Generally speaking, forecast skill scores are higher in the southeast areas than in the north west areas, but it may rains unexpectedly in coastal areas. (5) Model prediction consists with high resolution satellite and automatic station fusion precipitation products better and the threshold adjustment is limited. (6) The relevance between forecasting and observing is higher in the southeast area than in the northwest area. The model can forecast precipitation more reasonably in coastal areas than the west area.
  • Numerical Simulation and Analysis of Meso-β Scale Systems of a Heavy Rain Process in Hunan
  • LUO Juan;CHEN Zhongming
  • 2014 Vol. 33 (2): 495-503.  DOI:10.7522/j.issn.1000-0534.2013.00011
  • Abstract ( ) PDF (7631KB) ( )
  • Using the routine observational data，high spatial-temporal data on temperature of black bold observed by satellite and NCEP 1°×1° grid data, the evolution of the meso-β scale systems of a heavy rain process in Hunan during 19-20 June 2010 was analyzed. Using the high-resolution output from WRF model, the structure and evolution of the meso-β scale systems was analysed. The results show that: (1) There are multiple meso-β scale systems in the large scale favorable weather situations, and the heavy rainfall groups are associated with the development of the ground mesoscale convergence lines. (2) The analysis of TBB indicates that the meso-β scale system first generated from the meso-α scale convective cloud cluster front, and new meso-β scale systems are always triggered for the rainstorm. (3) WRF model are successfully simulated. Model outputs also indicates that there are several active meso-β scale systems in the front of the synoptic scale vortex, it is a phenomenon that meso-β scale systems are combined and propagated to downstream during actively. (4) The strong development of the meso-β scale systems are supported by the favorable mesoscale dynamic configuration, namely, a positive vorticity column extending from surface to 200 hPa is coupled with strong lower-level convergence and upper-level divergence.
  • Analysis on General Circulation Anomalies of the Extensive Heavy Rains in Guangxi in Last 50 Years
  • QIN Weijian;LI Dongliang;WANG Hui;QIN Zhinian
  • 2014 Vol. 33 (2): 515-521.  DOI:10.7522/j.issn.1000-0534.2013.00020
  • Abstract ( ) PDF (3186KB) ( )
  • Basing on the daily precipitation data at 90 stations in Guangxi and the NCEP/NCAR reanalysis data during 1961-2010, the characteristic of the atmospheric circulation anomalies of the heavy rains in Guangxi in the past 50 years were analyzed by using Lorenz circulation decomposition method. The deviation index H*, Ic and Ius for global (local) stationary waves are used to analyze the stationary wave anomalies in the extensive heavy rains. The results show that: In recent years, the occurrence of the extensive heavy rain processes exhibit an increasing tendency. The extensive heavy rainfall processes caused by the different weather systems with the different location and intensity of the subtropical high. There is an obvious positive correlation between the extensive heavy rain processes and the intensity of the subtropical high and the H* of the region(130°E-140°W，70°N-90°N)over Arctic Ocean, the negative correlation with the H* of the Northern Greenland and the Midwest Equatorial Indian Ocean and the Northeast Kazakhstan. The strengthen of Ic of the latitudinal bands (75°N-85°N) and (20°N-30°N), Ius of the latitudinal bands (10°N-30°N) and (35°N-55°N). The weaken of Ic of the latitudinal band (40°N-70°N). All these may be the causes of the increasing of the extensive heavy rainfall processes. There always is a most high value zone of Ius near the Arctic in the extensive heavy rainfall processes in Guangxi.
  • Analysis on Radar Echo and Precipitation Retrieve of Short-Duration Heavy Precipitation in Southeast Gansu
  • ZHANG Zhixian;ZHANG Qiang;ZHAO Qingyun;SUN Yun;ZHANG Liyang
  • 2014 Vol. 33 (2): 530-538.  DOI:10.7522/j.issn.1000-0534.2013.00001
  • Abstract ( ) PDF (4554KB) ( )
  • Radar quantitative measurement of precipitation has more advantage in time and space, but the relationship between the change of terrain and precipitation type has great rate. Studying on the radar quantitative measurement of precipitation is one of the main development ways to improve the radar applied ability utilize radar volume scan data. The reflectivity difference of Tianshui, Qingyang and Lanzhou weather radars on the equidistant line were contrasted when they simultaneously observe and the radar echo and precipitation retrieved if occur short-duration heavy rainfall were also analysed by using radar volume scan data. The result shows that: There is no obvious difference when echo more than 10 dBz; Comparing the region station with automatic station of precipitation, comparing the weather scale is less caused by short-duration heavy precipitation than other rainfall type, on the other hand, this conclusion also proved by statistic of radar echo. There are the scale about which 75% of the heavy precipitation are less than 20 km; The original station can't perfectly characterize the local precipitation is demonstrated; The estimated quantitative precipitation through packet of estimation, holistic and categorical Z-I relations were studied. The result shows that: Categorical Z-I relation is better than others on describe precipitation type in the Northeast edge of Tibetan Plateau, thus better solving the problem of underestimated light rain and overestimated heavy rain，and when rainfall belongs to 15~20 mm·h-1 is best.
  • Analysis on the Wind Kineticof Divergence Energy of Torrential Rain in East Guangdong Associated with Typhoon Noguri
  • CHENG Zhengquan;LIN Liangxun;LIU Yan;YANG Guojie
  • 2014 Vol. 33 (2): 557-566.  DOI:10.7522/j.issn.1000-0534.2013.00019
  • Abstract ( ) PDF (8687KB) ( )
  • Typhoon Noguri(0801) caused a torrential rain event after landfall at East Hainan and West Guangdong. Based on the observational data, NCEP reanalysis data and the kinetic energy budget of divergent wind, the large-scale circulation and the transfer of kinetic energy were analyzed. The results show that: The heavy rain event is the result of the interaction between the Noguri remnant and its environmental systems. The strong low-level southeastern jet from the West Pacific together with the weakened southwestern jet linking with Typhoon Noguri after landfall keeps the strong transfer of moisture to the east of Guangdong, and the variation of kinetic energy of divergent wind indicates the details of the process. The convergence effect of kinetic energy flux which is induced by the variation of the intensity of low-level jets and the convergence fields, is the main source of kinetic energy of divergent wind over the heavy rain band. Furthermore, the updraft of warm air in southeaster jet and the downdraft of cold air in southeastern jet result in the transfer of baroclinic available potential energy to kinetic energy of divergent wind. Cold air plays an important role in the two processes. Besides, the variation of heavy rain between the East Guangdong and near the landing site is mostly due to the difference of the atmospheric stratification, even though the low level divergence is close within these two places.
  • Effect of Climate Change on Extreme Energy Consumption for Residential and Commercial Buildings in Tianjin
  • LI Mingcai;GUO Jun;SHI Jun;XIONG Mingming
  • 2014 Vol. 33 (2): 574-583.  DOI:10.7522/j.issn.1000-0534.2012.00197
  • Abstract ( ) PDF (2669KB) ( )
  • Exploring changes of building energy consumption and its relationships with climate parameters can provide basis for energy-saving and emission reduction. Heating and cooling energy consumption of commercial building and heating energy consumption of residential buildings with different energy saving levels in Tianjin from 1961 to 2009 weresimulated. Also, extreme energy consumption threshold was determined bypercentile method. The interannual changes of extreme energy consumption and their relationships to climate change were analyzed. The results showed that: Days of extremeheating load in the heating period for commercial building significantly decreased during the recent 49 years, whereas no apparent variation but large interannual fluctuations for extreme cooling load. The contribution of extreme heating load to total heating load significantly decreased, and weak decline (but no significant change at the 0.05 level) was found in the contribution of extreme cooling load to total cooling load. Days of extreme heating load for the first-stage energy saving residential building and its contribution to total heating load showed significantdecrease, but extreme heating load days occurredonly in 7 years for the second-stage residential building. No extreme heating load was found for the third-stage residential building. The stepwise linear regression suggested that mean temperature was the dominant factor for affecting extreme heating load in winter of commercial and residential buildings, whereas extreme cooling load of commercial building was mainly affected by wet bulb temperature. This study indicates changes of extreme energy consumption and its different responses to climate change at different periods should be considered when energy saving is made in two aspects of the design and operation for commercialand residentialbuildings. The effect of extreme cooling energy consumption on safe operation of air-conditioning systems should also be paid more attention. Additionally, the improvement of energy saving not only reduces energy consumption of residential building, but also apparently decreases the days of extreme energy consumption, which may be beneficialto residential building energysaving.

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