Current Issue

• Validation of MODIS Land Surface Temperature Products in East of the Qinghai-Xizang Plateau
• MIN Wenbin;LI Yueqing;ZHOU Ji
• 2015 Vol. 34 (6): 1511-1516.  DOI:10.7522/j.issn.1000-0534.2014.00082
• Abstract ( ) PDF (1663KB) ( )
• In order to validate the Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperature (LST) products in the east of the Qinghai-Xizang plateau, the ground observation data of Litang Atmospheric Boundary Layer Observation Station are used. The accuracy of the ground-based surface temperature and its influencing factors are also analyzed. The results show that the surface radiometric temperatures (T_r) measured by the thermal infrared thermometer are lower up to 1.9 K during daytime and 1.1 K during nighttime than the surface temperatures (T_{s_R}) in account of the surface emissivity and atmospheric downward radiation. The deviations decrease with surface emissivity and increase with net long-wave radiation. The absolute errors between T_{s_R} and the surface temperature estimated using long-wave radiations (T_{s_L}) concentrate in less than 2.5 K when T_{s_L} are lower than 285 K, but reach up to10K when T_{s_L} are higher than 285K. If the surface emissivity error is less than 0.01, the surface temperature calculation error is less than 0.5 K. T_r, T_{s_R} and T_{s_L} are significantly positively correlated with LST and the correlation coefficients between T_{s_L} and LST are biggest. The coefficients are larger during nighttime than daytime, while are larger for Terra than Aqua, particularly during daytime. The regression model of T_{s_L} based on the LST has a standard error of 4.4904 K and passes the 99% confidence level.

• Distribution Characteristics of Plateau Monsoon and a Contrastive Analysis of Plateau Monsoon Index
• ZHOU Yi;FAN Guangzhou;HUA Wei;WANG Bingyun;ZHU Lihua;ZHOU Dingwen
• 2015 Vol. 34 (6): 1517-1530.  DOI:10.7522/j.issn.1000-0534.2014.00111
• Abstract ( ) PDF (25967KB) ( )
• Based on NCEP /NCAR monthly reanalysis data, the elements of the circulation field over the Qinghai-Xizang Plateau in winter and summer in P, Z and σ coordinate systems were analyzed, got the main distribution field of plateau monsoon, and drew a conclusion that the divergence field can most effectively reflect plateau monsoon's characteristics in the troposphere. Based on regional average of divergence field in the center of plateau main body, a new plateau monsoon index Div-PMI was defined. By contrasting the Div-PMI versus 4 kinds of plateau monsoon index on computing method, physical significance, seasonal and interannual variation, it was found that Div-PMI has a simple calculation method, can also reflect plateau monsoon's production mechanism preferably. Besides, it has a preponderance on reflecting the characteristics of the plateau monsoon's seasonal variation. A correlation analysis was made between monsoon index and the monthly precipitation of January, April, July and October in China, it was discovered that Div-PMI has a negative correlation with plateau area precipitation and the correlation is most remarkable in all indexes.

• New Characteristics of Temperature Change over Qinghai-Xizang Plateau on the Background of Global Warming
• ZHENG Ran;LI Dongliang;JIANG Yuanchun
• 2015 Vol. 34 (6): 1531-1539.  DOI:10.7522/j.issn.1000-0534.2014.00123
• Abstract ( ) PDF (1866KB) ( )
• Based on after homogenization treatment data at 81 stations over the Qinghai-Xizang Plateau(QXP) from 1971 to 2011, using of the area weighting method, the new characters of temperature over the QXP for nearly 41 years is researched. The result show that the QXP has a more significant warm mutation in 1997, lag behind the North China (1989), the Northeast China (1987) for 8 ~ 10 years, and later about 1 ~ 3 years than south and east and northwest of China. The mutation process in interior plateau has a significant relationship with terrain of the QXP, which performance as the higher the altitude, the later mutation. Besides, the warming form before and after the mutation is different, before the mutation the magnitude of warming decrease with elevation, but after the mutation the increasing tendency of temperature shows as increase with altitude, which by a 99% significant test. The maximum magnitude of the QXP warming no matter after and before mutation is in winter, and after the mutation the magnitude of warming in fall and winter had decreased, but increased in summer. Compared with the slowdown of global warming for recent 15 years, plateau after mutation showed more substantial warming, and the phase of temperature fluctuations over the QXP similar to the global temperature, both have good consistency.

• Circulation Features of Sustained Departure Plateau Vortex at Middle Tropospheric Level
• YU Shuhua;GAO Wenliang;PENG Jun
• 2015 Vol. 34 (6): 1540-1555.  DOI:10.7522/j.issn.1000-0534.2014.00134
• Abstract ( ) PDF (7525KB) ( )
• By using NCEP/NCAR reanalysis data, historic weather maps and Tibetan Plateau vortex and shear line yearbooks from 1998 to 2012, on basis of investigation and analysis of the sustained departure Plateau vortexes (SDPVs) with strong influence and their puissant period general circulation and weather systems affected them. The SDPVs are sorted into four types. Furthermore, the composite analysis and comparison analysis of physical field are carried out of different SDPVs with strong influence. The research shows:The SDPVs with strong influence of east blocking with shearing in two highs type has the greatest influence to China rainfall and mainly influences the Hetao area. The shearline type, tropical low impact type and foreside low trough type mainly influence areas are respectively the Huanghuai valley, southwest region, Changjiang river valley. The SDPVs with strong influence is not relied on the north of 40oN circulation after moved out of the plateau. They are mainly influenced by the interaction of middle level tropospheric western wind weather systems, sub-tropical weather systems and tropical weather systems near the SDPVs with strong influence. The middle tropospheric level large scale conditions of sustained departure plateau vortex types and the differences between them are revealed.

• Diagnostic Analysis of Potential Vorticity on a Heavy Rain in Sichuan Basin under Interaction between Plateau Vortex and Southwest Vortex
• QIU Jingya;LI Guoping;HAO Liping
• 2015 Vol. 34 (6): 1556-1565.  DOI:10.7522/j.issn.1000-0534.2014.00117
• Abstract ( ) PDF (4206KB) ( )
• The potential vorticity is used to diagnose the interaction between the Plateau Vortex (PV) and the Southwest Vortex (SWV) during the period of 28 June to 2 July 2013. According to the Hoskins potential vorticity theory, analyzed the vortex, height field and wind field of low vortex center position difference, verify the PV and SWV's intensity of movement of the change. The results show that when the form of vortex, the vorticity center are located in the west side of low vortex center of height field and wind field. The PV spread eastward,the intensity of strengthening. When the PV into the Sichuan Basin, the intensity weakening. Before the interaction, with PV moving eastward the downdraft can inhibit the development the SWV. When the PV removed the Tibetan Plateau,the PV interacts with the development of SWV. The vertical cross-section of potential vorticity can reflects PV interaction process with SWV and their movements, but also can be used to indicate changes in the intensity of the cyclone center. Analyses of isentropic potential vorticity indicate that the horizontal isentropic can well reflect the PV and the SWV interaction process.

• Influence of Plateau Summer Monsoon on Summer Precipitation in the Arid and Semi-Arid Regions of the Central and East Asia
• QI Yulei;FENG Song;HUANG Jianping;RAN Jinjiang;LONG Zhiping
• 2015 Vol. 34 (6): 1566-1574.  DOI:10.7522/j.issn.1000-0534.2014.00088
• Abstract ( ) PDF (5630KB) ( )
• The summer monsoon indexes in the Qinghai-Xizang Plateau derived from seven reanalysis datasets and their relationship with the summer precipitation in the arid and semi-arid regions of the Central and East Asia are examined in this study. Overall, the variations of plateau summer monsoon are fairly consistent among the seven reanalysis datasets, especially in interannual time scales. Correlation and composite analysis showed that the plateau summer monsoon plays an important role on variations of summer precipitation in the study region. During the strong plateau summer monsoon years, anomalous southerly winds with convergence in the Central Asia and anomalous easterly winds in southern Xinjiang bring more moisture transport to the study region, leading to more precipitation. While in Northern China, the anomalous northeasterly winds hinder the water vapor transport by the southwesterly flow and inhibit the precipitation development. During the weak plateau summer monsoon years, anomalous northerly winds with divergence in Central Asia and anomalous westerly winds in southern Xinjiang lead to less rainfall. While in Northern China, the abnormal southwest wind leads to excessive precipitation.

• Variation of Thunderstorm Activities and Its Connection to East Asian Summer Monsoon in Transition Region Between Qinghai-Xizang Plateau and Loess Plateau
• LI Jianglin;YU Ye;LIU Chuan
• 2015 Vol. 34 (6): 1575-1583.  DOI:10.7522/j.issn.1000-0534.2015.00001
• Abstract ( ) PDF (3255KB) ( )
• Thunderstorm days data collected from 54 stations over the transition region between the Qinghai-Xizang Plateau and the Loess Plateau from 1951 to 2012 were used to study the variation of thunderstorm activities and its connection to the East Asian Summer Monsoon (EASM). The results show that thunderstorm is the most active in summer, followed by spring and autumn. While almost no thunderstorm occurs in winter. There are two centers with high number of thunderstorm days, one of which is located in the Gannan area close to the Qinghai-Xizang Plateau and the other is in the Yongdeng and Wushaoling area. The Loess Plateau has much less number of thunderstorm days. The number of thunderstorm days decreased during the study period and years with strong EASM corresponded to years with high number of summer thunderstorm days, while years with weak EASM corresponded to years of medium and low number of summer thunderstorm days. Years with strong EASM are characterized by relatively high water vapor flux to the study region, eastward position of the western ridge of Western Pacific subtropical high,low geopotential height on 500 hPa in the east of Xinjiang and the northwest of Inner Mongolia, and developed Mongolia thermal low. These characterized are conducive to the generation of severe convective weather. Wavelet analysis indicates a quasi-thirty year period for both the number of thunderstorm days in summertime and the EASM.

• Possible Linkage between Land Surface Thermal Anomalies in Mid-High Latitudes of Eurasian Continent and Atmospheric General Circulation in Winter
• XU Chen;CHEN Haishan;HUANG Lingfang
• 2015 Vol. 34 (6): 1584-1592.  DOI:10.7522/j.issn.1000-0534.2014.00062
• Abstract ( ) PDF (5844KB) ( )
• Based on ERA40 monthly reanalysis data, the features of the land surface thermal anomalies over the mid-high latitudes of the Eurasian Continent during 1958-2001 were investigated, and the possible linkage between the land surface thermal anomalies and the atmospheric general circulation was further explored. Because of the global warming in recent years, the land surface temperature warming trend is more obvious and higher in the north of Lake Balkhash and Lake Baikal than the lower latitudes. Due to the inhomogeneously meridional land surface thermal changes, there is an apparent decadal weakening of the meridional land surface temperature gradient over the mid-latitude region of Eurasian Continent (around 40°N-50°N) at the early 1980. Decreased meridional gradient of the surface soil temperature tends to decrease the meridional gradients of both the surface air temperature and the air temperature in the lower atmosphere. According to thermal wind theory, decreased meridional temperature gradient will result in the decrease of the atmospheric baroclinicity. Meanwhile, the gradient of low level troposphere temperature, the vertical shear of zonal wind and zonal wind itself will be decreased.

• Characteristics of China Climate States Change and Its Impact on the Analysis of Climate Change
• LIN Jingjing;ZHANG Qiang
• 2015 Vol. 34 (6): 1593-1600.  DOI:10.7522/j.issn.1000-0534.2014.00092
• Abstract ( ) PDF (2888KB) ( )
• Based on the yearly surface air temperature and yearly precipitation of nearly 2000 meteorological stations over China from 1961 to 2012, compared the differences between the climate state and the climate standard state for the periods of 19712000 and 19812010. And used the standard of temperature grades and precipitation grades, and the definition of extreme events, the quantitative analysis of temperature and precipitation characteristics under different climate states for are investigated. The results indicate that: (1) The comparisons between climate state and climate standard state for the periods of 19712000 and 19812010 are respectively slightly higher and lower, which are likely to influence the climate analysis and evaluation; (2) Under the different climate states, the frequency of abnormal cold temperature grade increase, but the abnormal heat temperature are different; (3) Analyzed the frequency of extreme high value for the same elements in the same period, they are diametrically opposite under the different climate climates. But the frequency of the extreme low value are the consistent increase, especially the climate state of 19812010.

• Simulation Study about Climatological Basic State and Seasonal Variations of Global O₃ in the 20th Century
• LI Shubo;WU Tongwen;ZHANG Jie;ZHANG Fang;WANG Jun
• 2015 Vol. 34 (6): 1601-1615.  DOI:10.7522/j.issn.1000-0534.2014.00119
• Abstract ( ) PDF (13315KB) ( )
• The global chemistry-general circulation model BCC-AGCM-Chem0, newly developed in Beijing Climate Center, is used to investigate model performance in simulations of the tropospheric ozone from 1871 to 1999. Global archive of ground-based ozone data products derived from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) as well as the ozone data provided by CMIP5 are employed for model evaluation. BCC-AGCM-Chem0 can well capture climate mean state of ozone. Ozone concentration in the Northern Hemisphere is higher than that in the Southern Hemisphere, and is poleward increase. Simulated vertical ozone profiles agreed well with the ground-based ozone data. In comparison with the CMIP5 data, BCC-AGCM-Chem0 underestimated ozone concentration over the South Ocean south of 40°S and overestimated it over the latitude band from 40°S to 50°N about 3 to 6 Dobson units. Model biases are more pronounced over land than over ocean, which may be attributable to surface ozone emission, horizontal and vertical ozone advections. Spatial structures of the ozone seasonal evolution are also well reproduced. Spatial correlation coefficients of the ozone concentration between the BCC-AGCM-Chem0 simulation and the CMIP5 data in January, April, July and October are 0. 89, 0. 97, 0. 86 and 0. 91, respectively. The ozone concentration reaches its maximum in spring and its minimum in autumn for both the Northern and Southern Hemispheres. The seasonal evolutions of the ozone concentration show different performances below and above 500 hPa. This is evident in both simulation and the ground-based observation. Ozone concentration changes at the lower troposphere may be due to surface emission, dry and wet deposition, whereas ozone concentration changes at the higher troposphere can be attributed to chemistry reactions and the downward ozone transport from the stratosphere.

• Applicability Evaluation of Drought Indices in Monthly Scale Drought Monitoring in Southwestern and Southern China
• WANG Suping;WANG Jinsong;ZHANG Qiang;LI Yiping;WANG Zhilan
• 2015 Vol. 34 (6): 1616-1624.  DOI:10.7522/j.issn.1000-0534.2014.00089
• Abstract ( ) PDF (5282KB) ( )
• Based on daily and monthly meteorological data from 129 weather stations , the applicability of seven drought indices include in SPI, PDSI, MCI, GEVI, K, SPIW60 and DI in Southwestern and Southern China were evaluated. The results showed that for the ability of drought monitoring at a certain month, MCI and K indices have the best performances in all of the four seasons. And in comparison, K has better ability in summer and autumn and MCI is good in winter and spring. SPIW60 is less effective than others. And the rest four indices performance well in one or two season, for instance, DI can get the best monitoring effect in winter and spring. PDSI and GEVI performance well in summer and autumn, and SPI do best in summer. Refer to the ability of depiction of the developing and changing process of drought, K has the best performance, which can depict the dynamics changes well in each station. Followed by DI, MCI has unreasonable aggravate in ease period. and own to the less consideration of drought accumulative effect, SPI, SPIW60 and GEVI react too fast in ease or remove stage. And the PDSI was poor in depict the fluctuation of drought developing. Taken together, MCI and K are better than other indices, and K is most suitable for drought monitoring in monthly scale in the study area.

• Research on Different Types of Cloud and Variation Characteristics of Hydrometeors in Cloud over China and Its Neighborhood in Daytime
• LI Haoran;SUN Xuejin;WANG Minyan;WEI Kejing;ZHANG Riwei;LIU Lei;LI Yan;ZHOU Yongbo
• 2015 Vol. 34 (6): 1625-1635.  DOI:10.7522/j.issn.1000-0534.2014.00129
• Abstract ( ) PDF (23008KB) ( )
• Based on the CloudSat 2B-CLDCLASS and 2B-CWC-RO data from December 2011 to November 2013, the distribution of cloud amounts and cloud water path (CWP) for single layer and multi-layer respectively for different cloud types over China and its neighborhood in the daytime were analyzed. Also the researches on the seasonal variation of the cloud water path over this area and how the macroscale circulation affects the variation were performed. The results show that the annual mean cloud amounts and CWP of single layer are in general more than the cloud overlapping's over this area. The 30°N is a clear north/south boundary for cloud amounts and CWP, which are relatively high in the north. The CWP of this area is greatly influenced by macro scale circulation,water vapor condition and terrain, and shows a feature that the content of the hydrometeors in summer is more than that in winter. Besides, the distribution of CWP is affected by the seasonal variation of the Westerlies substantially.

• Precipitation Characteristics and Water Vapor Source Analysis of Record Heavy Rainfall Process in Sichuan
• ZHOU Changyan;TANG Xinying;DENG Biao
• 2015 Vol. 34 (6): 1636-1647.  DOI:10.7522/j.issn.1000-0534.2014.00121
• Abstract ( ) PDF (3824KB) ( )
• Observational and NCEP/NCAR reanalysis data are used to diagnose the precipitation characteristics and water vapor source analysis of record heavy rainfall in Sichuan on 7-12 July 2013. Results indicate that the record storm occurs mainly in the western Sichuan Basin, with a heavy rainfall belt extending from Guangyuan in northwestern Sichuan Basin to Ya'an and Leshan in southern Sichuan Basin, and it has a large amount of total precipitation, high rainfall intensity, stable strong precipitation centers, long duration time and other notable features. The maximum cumulative rainfall during the record storm occurs in the area of Dujiangyan in Chengdu with a value of 744. 9 mm, setting a new rainfall record for itself and for the national observatory station in the meteorological record of Sichuan. The moisture source in this storm is not exactly the same as that in the climate mean state. Except for the southerly water vapor transport from the South China Sea and the Western Pacific, the southwesterly water vapor transport from the northern part of the Bay of Bengal and the westerly water vapor transport over the main body of the Qinghai-Xizang Plateau, in this storm, there appears a new water vapor transport path that is the southwesterly water vapor transport from the northern part of the Arabian Sea, which passes main body and the southeastern part of the Plateau and arrives in Sichuan Basin. The abnormal strong water vapor transport, the favorable convergence and divergence situation over Sichuan Province and its neighboring, the stable existence of the large-scale circulation patterns over the middle and high latitudes over the Eurasian continent and other factors work together and eventually lead to a steady rain belt and extraordinary rainfall.

• Analysis on Unusual Path Associated with Mesoscale Convective System in a Continuous Heavy Rain
• GUO Damei;LIU Yong;MA Xiaohua;LI Pingyun
• 2015 Vol. 34 (6): 1648-1657.  DOI:10.7522/j.issn.1000-0534.2014.00076
• Abstract ( ) PDF (6519KB) ( )
• By using observation data, NCEP/NCAR reanalysis data, FY-2E product and the automatic station data, a continued strong convection rainstorm in North China to the eastern region of Northwest China is analyzed. The obtained result are as follows.Firstly, 500 hPa short wave trough which locates in the bottom of the northeast cold vortex, the northeast wind on the east side of the continent high, shear line and cold temperature advection in lower levels and the cold air in surface provide favorable synoptic background for the mesoscale convective system's occurrence, development and movement. Secondly, meso-β scale and meso-α scale convective systems cause the strong convection rainstorm. With 23 h, mesoscale convective systems move roughly from southwest to northeast. Interaction between cold air from the eastern area and warm moisture in North China, convection has triggered. Thirdly, the moving direction of MCS depends on wind direction and speed in the whole layer. When there is the weak wind speed on high layer and middle layer and opposite strong wind speed on low layer, the mesoscale convective system's moving path is consist with wind direction on low layer. When there is the weak wind speed on low layer and opposite strong wind on high and middle layers, strong wind speed on high and middle layers, the mesoscale convective system's moving path is consist with wind direction on high and middle layers. Fourthly, the all layers are no temperature advection before the convective precipitation occurs. At the same time, the high and middle layers wind is very weak, and the vertical wind shear is very small.

• Relationship between Sensible Heat Net Flux over the Bay of Bengal and Autumn Rainfall during September and October in Shaanxi
• WANG Dan;SHENG Lifang;HUANG Shaoni;BAI Guangbi;GAO Hongyan
• 2015 Vol. 34 (6): 1658-1667.  DOI:10.7522/j.issn.1000-0534.2014.00073
• Abstract ( ) PDF (5606KB) ( )
• Based on the NCEP/NCAR reanalysis monthly data and daily precipitation data in autumn during September and October at 96 stations in Shaanxi from 1979 to 2011, the relationship between sensible heat net flux over the Bay of Bengal and autumn rainfall in Shaanxi has been studied, which possible cause and mechanism is also preliminary analyzed. The result shows that there is a notable negative correlation between the rainfall in Shaanxi and the intensity of the sensible heat net flux over the Bay of Bengal in autumn. The rainfall in Shaanxi is more than normal while the sensible heat source over the Bay of Bengal is weaker in autumn. The Ural blocking high is stronger than normal, the ridge positions of the western Pacific subtropical high lean to west and north, and the vapor transport comes from the Indian Ocean and the Atlantic ocean by southerly flow and convergent upward velocity in Shaanxi are strengthened while the intensity of the sensible heat net flux over the Bay of Bengal is weaker in autumn, which is propitious to appearance of circulation making for the autumn rainfall in Shaanxi. Besides, the position of South Asian High is lean to north, and the South Asian Summer Monsoon is stronger than normal in September. Abnormal autumn precipitation in Shaanxi is close to the characteristics of sea surface temperature in low latitude. In some extent the relationship between sensible heat net flux over the Bay of Bengal and rainfall in Shaanxi can be explained by spatial pattern of the second EOF model of SST in autumn. The sensible heat source over the Bay of Bengal in autumn has significantly positive correlation with that in previous winter and summer, which can be taken as a reference for forecast of autumn rainfall in Shaanxi.

• Impact of Thermal Action on Different Intensity Sandstorms in Ningxia
• CHEN Yuying;CHEN Nan;TAN Zhiqiang;ZHENG Xiaohui
• 2015 Vol. 34 (6): 1668-1676.  DOI:10.7522/j.issn.1000-0534.2014.00090
• Abstract ( ) PDF (4228KB) ( )
• Based on conventional observation data and the ECWMF ERA-Interim 6 hourly reanalysis data with resolution 0.25°×0.25°, the frontogenesis function and the surface heat flux on thunderstorm gale on 18 May, strong wind and dust on 28 February and 9 March 2013 in Ningxia were comparative analyzed. The result shows that surface temperature was increased rapidly due to the developed thermal low or Mongolia cyclone ahead of cold fronts, then the temperature and pressure gradient across the fronts and the boundary instability enhanced by impacts of surface sensible heat flux. Further, the frontogenesis and dry convection could be easily developed, which were beneficial thermal conditions for the strong wind and sandstorms weather. The wind and sandstorms appeared in the dense gradient belt of the sensitive heat flux, the strong sandstorm appeared in the amplitude center of the sensitive heat flux. Meanwhile the important indicators of forecasting and warning for the wind and sandstorm weather in Ningxia are the intensity of the cold air, the position of high pressure ridge, the center value of the frontogenesis function, the sensitive heat flux and the obvious frontogenesis below mid and low level troposphere.

• Characteristics of Two Hail Cases in Boundary Layer
• YAO Risheng;TU Xiaoping;DU Kun;DING Yeyi;ZHU Jiamin;YANG Hao
• 2015 Vol. 34 (6): 1677-1689.  DOI:10.7522/j.issn.1000-0534.2014.00072
• Abstract ( ) PDF (13673KB) ( )
• Based on the data from the conventional meteorological observations, the automatic weather stations in Zhejiang province, the Ningbo Doppler radar and the 370 meters tower on the Liangmaoshan island etc., detailed comparison analysis was carried out on two hail cases occurred on 7 July 2012 (case 1) and 22 March 2013 (case 2) in Ningbo. The results show that the two cases happened under different synoptic backgrounds, with case 1 initialized from a strong thermal convectional cell, while case 2 developed from a moving convective zone with characteristics of elevated thunderstorms. The 2 cases displayed similar surface flow patterns, with the front inflow convergence zones and the rear divergence areas both relatively stable to the storm centers. The front outflow edges were found 8~10 km away from the hail-hit areas in both cases with sinking trail vortices about 4 km behind. The boundary layer of the front inflow zones primarily showed pressure dropping, air flow turning to the storm center, and increasing of both velocity and convergence intensity. Within the divergence areas, drastic meteorological element changes were observed. In case 1, the tower was in front of the hail storm inflow zone, the meteorological changes at the tower were observed at the lower levels prior to the higher levels. Also it showed a short time period of reversed changes of all elements right before hailfall, due to the downward air-flow dragging and weakening of air suction. In case 2, when the tower was in the lower inflow region, velocities were observed strengthened at the low levels first as well. When the hail storm went by, the boundary layer elements at the tower showed simultaneously abrupt changes as the result of cold outflows.

• Activities of Cold-Dry Air and Its Impact on Convective Heavy Rain Process in Beijing
• WU Qingmei;ZHANG Shengjun;LIU Zhuo;ZHAO Wei
• 2015 Vol. 34 (6): 1690-1698.  DOI:10.7522/j.issn.1000-0534.2014.00081
• Abstract ( ) PDF (12018KB) ( )
• By using conventional observation data, radar reflectivity, 1°×1° NCEP reanalysis data and unconventional observations including wind profile radar and ground-based radiometer data, the cold air and its influence was studied according to a strong convective storm in Beijing area on 23 June 2011. The main results are as follows: The dry zone and high potential area above middle-level corresponded well with dark zone in WV image, which showed the dry intrusion was obvious. The temperature, humidity and wind changed instinctly which was observed by the ground-based radiometer and profile radar, the storm was triggered just after the temperature and humidity above 5 km decreased to the lowest. The dry intrusion caused the low θ_se center just over the high θ_se center, which led to strong convective instability. The lower level northeast airflow was cold and dry, and the corresponding temperature front was distinct under 850 hPa, which provided dynamical and thermal effect for the development of the convective system. The backflow cold formed anticyclone on the east of Beijing, which was good for the convective system to stay at Beijing and the rainfall to sustain longer.

• Numerical Simulations of Cloud Structure and Seedability of a Precipitating Stratiform in Hebei
• SUN Jing;YANG Wenxia;ZHOU Yuquan
• 2015 Vol. 34 (6): 1699-1710.  DOI:10.7522/j.issn.1000-0534.2014.00086
• Abstract ( ) PDF (8826KB) ( )
• A case of westerly trough precipitating stratiform cloud on 21 September 2012 is simulated using the mesoscale model MM5. Meso- and micro-structures of this precipitation are analyzed using simulations and observations of satellite, radar and aircraft. The large-scale weather systems of the precipitation are westerly trough on 500 hPa and shear line on 700 hPa. There is no obviously cold front at low levels. The cloud structures are different at different area of the cloud system. In the forepart, the cloud system composes of only supercooled cloud water and ice particles. There is a little cold cloud precipitation. The cloud top temperature is -35 ℃. Near the line of westerly trough, the cloud is mixed phase with more ice, snow, graupel and more supercooled cloud water in cold area and more cloud water and rain water in warm area. The cloud top temperature is -20 ℃. In the rear part, the cloud system composes of mostly warm cloud water. The cloud top temperature is -5 ℃. There is a little warm cloud precipitation. The production of cloud water needs updraft and high saturation and is proportional to them. The seeding areas are distinguished by supercooled water, updraft, number concentration of ice, temperature and precipitation intensity. It is strongly seedable near the trough line due to the much more supercooled water. The seeding height is 3.8~6.5 km. These areas have good potential of artificial precipitation enhancement.

• Dynamic and Thermal Structure and Evolution Characteristics of a Central Asian Vortex
• LI Man;YANG Lianmei;ZHANG Yunhui
• 2015 Vol. 34 (6): 1711-1720.  DOI:10.7522/j.issn.1000-0534.2014.00077
• Abstract ( ) PDF (11426KB) ( )
• By using the NCEP 1°×1° reanalysis daily datasets, the dynamic and thermal three-dimensional structure and evolution characteristics of a central Asian vortex causing rainstorm during 4 to 7 September 2009 were analyzed, and its development mechanisms were discussed. The results indicated that the vortex had an obvious cold core structure and developed strongly, which developed at the upper firstly (its center and evolution characteristics were evident on 300 hPa) and extended downward with time, its development-mature-weakened process was a baroclinic-barotropic-baroclinic process. In mature stage, cold center coincided with height center with the axis tending to be vertical; there was a positive vorticity center on both western and eastern flank of vortex center on 300 hPa which were symmetrical and the vorticity almost was positive in troposphere; the lower troposphere was convergence while the upper troposphere was divergence, making conditions favorable for ascending motion and vortex development. In weaken period, the axis-line tilted toward the west and cold center declined significantly; there was negative vorticity in the middle and upper troposphere and no obviously divergence/convergence and ascending motion in almost all of troposphere over vortex center. During this process, ascend motion combined with ample water vapor condition causing the heavy precipitation. The “upper dry, lower wet” spatial structure in troposphere, the cold air moved downward as well as the intrusion and downward motion of high potential vorticity were conducive to the development of this vortex and played a significant role in its development and evolution.

• Asymmetric Characteristics of the Northeast Cold Vortex and Its Effect on Heavy Rain
• WANG Zongmin;LI Jiangbo;WANG Fuxia;LIN Chaoxu
• 2015 Vol. 34 (6): 1721-1731.  DOI:10.7522/j.issn.1000-0534.2014.00084
• Abstract ( ) PDF (15836KB) ( )
• The characteristics of cloud image, radar image and precipitation during the heavy rains caused by the northeast cold vortex are analyzed using some cases including June 8, 2009. Based on the NCEP FNLs analysis data, the three dimensional structure characteristics, the possible establishing process and releasing mechanism of convective instability are studied further. The results show that the northeast cold vortex has dynamic and thermal asymmetric characteristics except for the middle layer of atmosphere. In the upper level troposphere the cold vortex evolves to a trough accompanied by a warm center and an upper-level jet stream, but in the low level troposphere itturns to an inverted though and a warm tongue while the cold center is not obvious.The main negative vorticity, divergence and upward motion distribute in the south by east of the cold vortex. The dry and cold advection in the middle atmosphere superimposes on the low-level warm and moist advection in the southeast part of the rotating cold vortex,causing rapid growth of the convective instability which can be enhancedby the warming of surface air due to the net radiation in afternoon. While the cold vortex produces convective instability, the upward motion in its southeast part provides favorable triggering conditions leading to the convection development and the releasing of instable energy.

• Analysis of a Severe Convection Event Causing Heavy Disaster in North Central of Henan
• SI Fuyi;ZHOU Shunwu;WANG Chuanhui;XU Wei
• 2015 Vol. 34 (6): 1732-1740.  DOI:10.7522/j.issn.1000-0534.2015.00027
• Abstract ( ) PDF (9121KB) ( )
• By using the MICAPS conventional observation data, 0. 5° × 0. 5° NCEP FNL data and radar data, combined traditional “pattern recognition” method with “ ingredients-based” method, the rare regional server convective weather of hail, thunderstorm and gale that happened in the morning of August 1, 2013 in North central Henan was analyzed. The results are as follow:(1) This process was caused by a forward-tilting trough, and its formation cause was the warm moist air hindered and weakened the trough near the ground.(2) On the basic of circulation classification, adopting forecast method (Ingredients-based method)to analyze the convective weather four components helped to improve the ability of strong convection weather forecast. (3) The transportation and convergence of water vapor improved rapidly because the radial degree of atmospheric circulation within the low and mid latitude increased, while westerly trough approaching the edge of subtropical high belt. (4) The invasion of mid-level dry jet and large vertical wind shear were considerably important in maintaining and developing of the storm. (5) Radar echo tracking displays that the storm system originated from the intersection and merging of two bow echoes (squall lines), and after the outbreak of severe convective weather the main system developed into a typical squall line again, which moved along the convergence line from southwest to northeast, the extrapolation method could be used to determine its next area of influence, and there were more than 30 minutes earlier warning time. In the end, a technology route about convection weather forecast was also given.

• Propagation Patterns and Airflow Structure Characteristics of Extreme Rainstorms in Shandong
• WAN Mingbo;MENG Xiangui;DIAO Xiuguang
• 2015 Vol. 34 (6): 1741-1750.  DOI:10.7522/j.issn.1000-0534.2015.00012
• Abstract ( ) PDF (13178KB) ( )
• Based on the radar data and extreme rainfall events,the reflectivity characteristics and airflow structures of extreme rainstorms occurred in Shandong Province were analyzed comprehensively. The results showed that the evolution of extreme rainstorms have four patterns: backward propagation, forward propagation, quasi-stationary and regeneration. For backward propagation pattern, the outflow from multicell cluster of storms interacted with the surface wind and formed areas of strong surface convergence on the upwind side, this strong convergence triggered new cells, thereby causing a cell propagation vector in the opposite direction of the steering flow. For forward propagation pattern, at low levels, cooler air diverging from the downdraft intersects the inflowing air along a gust front, creating a region of strong low- level convergence favorable for new updrafts. The quasi-stationary or motionless rainstorms often accompanied by γ-scale cyclone vortex sustaining long time in the middle-low level for the quasi-stationary pattern. As regards to regeneration pattern, regeneration zone where new cells were constantly inspired often correspond with stable and less moving local convergence zone. Two or more patterns were included in process of large scale heavy precipitation.

• Application of Back-Propagation Neural Network in Predicting Non-Systematic Error in Numerical Prediction Model
• LI Huchao;SHAO Aimei;HE Dengxin;WANG Yueya
• 2015 Vol. 34 (6): 1751-1757.  DOI:10.7522/j.issn.1000-0534.2014.00120
• Abstract ( ) PDF (1562KB) ( )
• Based on the temporal dependence of forecast errors derived from numerical weather prediction, the back-propagation (BP) neural network is used to establish the prediction model for predicting non-systematic forecast error. The effectiveness of this model is tested with the analysis and 24-hours forecast data produced by T213 model from 2003 to 2007. The results show that the established BP neural network model has a good ability on predicting non-systematic error in the next 24 hours. For most of 332 test samples, the spatial distribution of the predicted non-systematic errors is consistent with the truth. The non-systematic error estimated by BP neural network model can further correct forecasts on the basis of the systematic error correction, and its correction effectiveness is better than that of the systematic error correction only. For 332 test samples, the effective rate of systematic error correction on forecasts is 61%, but the effective rate of nonsystematic error further correction can increase to 82%.

• Glaciation and Ice Multiplication of Convective Clouds and Their Dependence on Aerosol Investigated by Satellites
• ZHU Yannian;YU Xing;XU Xiaohong;LIU Guihua;DAI Jin
• 2015 Vol. 34 (6): 1758-1764.  DOI:10.7522/j.issn.1000-0534.2014.00083
• Abstract ( ) PDF (3431KB) ( )
• The ice phase of convective clouds is complicated and affects the precipitation and cloud radiative properties. The ice forming nuclei (IFN) activity of aerosols glaciate the clouds are still unclear. The CALIOP and MODIS satellite data during 2008 to 2011, were used to investigate the cloud T_g and r_e distribution over the China and surrounding areas. The results shows as follows: (1) Satellite observations show that desert dust and heavy air pollution over study area have similar ability to glaciate convective clouds, when r_e-5<12 μm T_g increase with increasing AOT. (2) When r_e-5≥12 μm, aerosol suppress ice multiplication and decrease T_g. (3) Ice multiplication is the main mechanism for pristine maritime deep convective clouds, while it works only 20 percent for continental convective clouds.

• Research on Ground-Level PM_2.5 Mass Concentration Retrieval Based on MODIS Aerosol Optical Thickness
• XIA Zhiye;LIU Zhihong;WANG Yongqian;CHEN Hongbin;SUN Mingjiang;JIAO Lu
• 2015 Vol. 34 (6): 1765-1771.  DOI:10.7522/j.issn.1000-0534.2014.00075
• Abstract ( ) PDF (1110KB) ( )
• 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 PM_2.5 particles are the main component. In order to mainly retrieve mass concentration about PM_2.5 near the surface using MODIS AOT(aerosol optical thickness) data. Firstly, the comparison analyses between AOT from MODIS and corresponding PM_2.5 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 PM_2.5 primarily. Secondly, the seasonal variations about AOT and PM_2.5 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 PM_2.5 themselves' physical and chemical features and meteorological factors to the both correlativity. In the end, a logarithm reversion model about PM_2.5 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 PM_2.5 mass concentration near the ground effectively using AOT, and provide a new scientific basis for PM_2.5 reversion by remote sensing, and also valuable for haze detection.

• Assessment of CINRAD Regional Coverage for Quantitative Precipitation Estimation
• WANG Hongyan;LIU Liping
• 2015 Vol. 34 (6): 1772-1784.  DOI:10.7522/j.issn.1000-0534.2014.00122
• Abstract ( ) PDF (7798KB) ( )
• Accurate analysis of coverage of weather radar is important for using CINRAD observations, and flooding is one of the main meteorological disasters in China. In this paper, a method considering terrains' occultation and according to local distribution of melting layer height is supported to assess coverage of weather radar for quantitative precipitation estimation (QPE). Taking Zhejiang province as an example, objective assessment of CINRAD regional coverage is presented respectively for CINRAD operational QPE and algorithm considering terrains' occultation to radar beam. The results are:during the flood season, 17% of the maximum covered area is invalid as the result of the limit of melting layer. And coverage capability of beam below melting layer is directly related to beam blockage, blind area is very small for both QPE regions. For default operational CINRAD QPE, 35% of the maximum covered area faces the risk of underestimation due to partial beam blockage, which covers most region of the province. When considering terrains' occultation, most of the region, more than 82%, is valid coverage, including the whole province. Regional coverage is good to most rainfall of a year too. Finally, a improved method of getting hybrid scan from all elevation cuts with both the restriction of melting layer height and beam blockage is presented, in addition to good coverage, it's QPE results agree with actual precipitation distribution best when comparing with operational CINRAD method and hybrid scan method below averaged rain top.

• Spatial Distribution of Error from the Convective Precipitation Estimation of Radar and Optimization of Z-R Relationship
• YANG Jie;LIU Liping;ZHAO Chengcheng;WU Yahao
• 2015 Vol. 34 (6): 1785-1796.  DOI:10.7522/j.issn.1000-0534.2014.00074
• Abstract ( ) PDF (5585KB) ( )
• In the quantitative precipitation estimation of China New Generation Weather Radar (CINRAD) adjusted with rainfall stations, better matching between radar echo intensity and the observation from rainfall stations is the key to fit Z-R relationship accurately. The large spatial and temporal changes characteristics of convective precipitation echo intensity have a serious impact on the radar and rainfall station data matching and the accuracy of quantitative precipitation estimation. According to analysis the spatial distribution of error between the convective precipitation estimation of radar and rainfall station of three convective precipitation process in Henan Province, the following rules are founded: most seriously overvalued radar echo intensity points and some underestimate points are distributed on the edge of the strong echo intensity area with the single point's echo-intensity changes with time; part of rainfall stations with zero value observation for part time are distributed in the center of the strong echo intensity. The analysis shows the sudden heavy precipitation and heavy precipitation center is easy to cause the large error of observation from rainfall stations and therefore cause great influence on the Z-R relationship fitting. According to the characteristic of convective echo-intensity and the matching relationship between the echo intensity and rainfall stations got in this paper, adding method of eliminating large error rainfall stations by using the echo intensity gradient index and also method to optimize the average echo intensity and cumulative time are proposed, and get the best solution for convective precipitation estimation. Through analyze influences of all above factors on the precipitation estimation in detail, the results show that eliminate the large error rainfall stations by a certain index and then use the best precipitation estimation solution, and these improve estimation precision for convective precipitation.

• Topological Structure of Spectrum Modal System for Atmospheric Dynamics Equations
• LIU Chun;LIU Sibo;LI Xiumei;ZHANG Chunhui;ZHOU Wenlin;QIAO Qi
• 2015 Vol. 34 (6): 1797-1804.  DOI:10.7522/j.issn.1000-0534.2014.00065
• Abstract ( ) PDF (408KB) ( )
• Compared to the fluid motion field changes with time to slow time, it is reasonable for the assumption which exogenous does not change with time, when the atmospheric circulation as the fluid movement in the exogenous driven dissipative. Therefore, this paper discusses forcing the disturbance effect of positive pressure and without divergence of system dynamic equations of atmosphere, neglecting the topography and β effect. For linear systems, the equilibrium is a saddle point structure. At this time, changes in external forcing will cause change of the structure of the system. The topological structure of the system does not change, still for three dimensional saddle point structure, when the external force to the critical point. However, invariant subspace and unstable dimension of the invariant subspace will change. When the external source force tends to zero, the system from unstable will turn to stable state. At this time, the new steady bifurcation occurs, and the saddle point structure of before into stable node structure. For nonlinear systems, do not affect the structure of positive pressure and without divergence of atmospheric system, when the external forcing is small enough. In the vicinity of the real equilibrium, there is a stable local invariant submanifold and unstable local invariant 3D saddle submanifolds invariant manifold structure. Finally, based on the saddle point structure is difficult to integral characteristic, the structure of solutions near the equilibrium point is given, through used to integral method.

• Existence of Periodic Orbits about Quasi-Geostrophic Model on Three Waves
• LIU Chun;LIU Sibo;LI Xiumei;ZHANG Chunhui;LENG Lidong
• 2015 Vol. 34 (6): 1805-1811.  DOI:10.7522/j.issn.1000-0534.2014.00066
• Abstract ( ) PDF (658KB) ( )
• When dimension n≥3, the existence, nonexistence, uniqueness and stability of periodic orbits of dynamical systems, in the theory and application, are worthy of study. in the two-dimensional dynamical systems, the basic tools of study the existence of periodic orbits is Poincar-Bendixson and its corollary (ring zone principle).However, The counter example of D. Heedene display that Poincar-Bendixson has not been simply popularized in the high dimensional case. Thus, over the years, studying the existence of periodic orbits in the dynamical systems, mainly rely on the ring zone principle. To the quasi-geostrophic model in the action of the three waves, the simple pattern of exogenous, turbulent friction has been more mature, but there is less study about it is cyclical behavior. Furthermore, homoclinic orbit and heteroclinic orbit are associated with solitary wave and the vortex, and homoclinic orbit and heteroclinic orbit at rail cross-sectional intersect is the condition of chaos, also the key to study the certainty and randomness. The combination of certainty and randomness is the main methods that quasi-geostrophic model explaining the turbulent structure. So, homoclinic orbit and heteroclinic orbit are very important to the periodic and stability of quasi-geostrophic model. Through analyzing, we discover that the nonlinear has a form of three-dimensional- Hamilton, induced by the main structure-Jacobi of the quasi-geostrophic model in the action of three-wave, so the article study the topological nature of the model based on Poincar-Bendixson. Meanwhile, in view of the importance of the quasi-geostrophic model for the structure of turbulence, homoclinic orbit and heteroclinic orbit that the balance point of the four saddle pattern corresponding to were analyzed. The analysis revealed that the presence of four different homoclinic (heteroclinic) orbit as well as the center for each type of balance exist in a column corresponding periodic orbits around the center on the Poisson symplectic leaf surface. Having a discussion about a special class of perturbations of the situation and the system of central periodic orbit perturbations near the equilibrium point, people are able to access to the conditions of the original three-wave quasi-geostrophic model of periodic solutions exist.