Current Issue

articel

• Vertical Distribution of Ozone and Stratosphere-Troposphere Exchanges on the Northeastern Side of Tibetan Plateau
• CHEN Chuang;TIAN Wen-Shou;TIAN Hong-Ying;HUO Yan-Feng;SHU Jian-Chuan
• 2012 Vol. 31 (2): 295-303. 
• Abstract ( ) PDF (1309KB) ( )
• Using the ozone and temperature sounding data, NCEP/NCAR data, total ozone column of TOMS satellite observations and back trajectories calculated from NOAA HYSPLIT model, the factors and processes affecting vertical profiles of ozone near the Tibetan Plateau through a case study were investigated. The analysis shows that the dynamic transport is the main factor which influences on the vertical distribution of ozone over the Tibetan Plateau. The invasion of air from the high latitude to the south will lead to the increase of ozone concentration over the Tibetan Plateau and affect the range and shape of ozone valley' over the Tibetan plateau. Although the impact of chemical processes on ozone concentration over the Tibetan Plateau is not significant in the lower stratosphere, but the analysis indicates that the ozone changes are in good accordance with ozone changes in the stratosphere. The analysis also reveals that downward invasion of the stratospheric air into the troposphere is likely to occur near the edge of high pressure systems, particularly for those strong quasi-stationary anti-cyclone systems at middle and high latitudes. This invasion of stratospheric air will cause the increase of the ozone concentration in the troposphere.

• Characteristic Analysis of a Severe Convective Weather over Tibetan Plateau Based on TRMM Data
• LI Dian;BAI Ai-Juan;HUANG Sheng-Jun
• 2012 Vol. 31 (2): 304-311. 
• Abstract ( ) PDF (909KB) ( )
• In order to explore the horizontal and vertical structures of precipitation over the Tibetan Plateau（TP）， the characteristics of the severe convective weather such as hail and thunderstorms were studied using TRMM (Tropical Rainfall Measure Mission) satellite and NCEP data．The results showed that： (1) The cloud causing the severe convective precipitation consisted of some isolated and scattered cells， and the weak deep convective cloud cell was the predominant type． At the same time， the center of low microwave temperature appeared to be isolated and scattered．Spectrum distributions of the deep convective precipitation mainly occurred in 1～20 mm·h-1， the sample and precipitation more than 90% for the week convective precipitation concentrated in 0～5 mm·h-1．The convective clouds were compressed vertically．Cloud\|ice particles were concentrated at the level of 6～18 km， but precipitation\|ice, precipitation\|water and cloud\|water particles were concentrated below 8 km．The hail and thunderstorms over TP performance for much precipitation\|ice particles in low troposphere．(2) Comparing with the severe convective over other plain region， the convective clouds over TP had  smaller or weaker precipitation rate， the heterogeneous sample distribution and  shorter storm height．It was not symmetrical distribution between the high precipitation rate and the low microwave temperature．Latent heat release appeared to be single\|peak type．(3) When the severe convective system occurred， the vertical speed can get its maximum on 400 hPa and water vapor was concentrated mainly below 400 hPa．

• Characteristics of Surface Sensible Heat Flux Calculated from Satellite Remote Sensing and Field Observation in Arid Region of Northwest China
• WANG Hui;LI Dong-Liang
• 2012 Vol. 31 (2): 312-321. 
• Abstract ( ) PDF (1200KB) ( )
• The monthly surface thermal transfer coefficients at 84 meteorological stations inthe arid region of northwest China are calculated usingthe normalized difference vegetation index (NDVI) data from July 1981 to December 2006 observed by National Oceanic and Atmospheric Administration（NOAA）remote sensing satellitesand Ch-INDVparametric relational expressions, then the monthly surface sensible heat fluxes are calculated by bulk transfer method with the observations of meteorological stations. The obtained conclusions are as follows： (1)The surface sensible heat fluxes calculated by the observation of conventional meteorological station and ERA-40 reanalysis data are uniform on magnitude and in both distribution situation and the interannual change tendency. But the spatial distribution of the calculated values can obviously reveal the local climate characteristics of the surface sensible heat flux in the regions where the weather stationswere located. (2)Annual variation characteristic of the surface sensible heat flux appears unimodal change,the surface sensible heat transfer is extremely strong in spring and summer and weak in autumn and winter. The surface sensible heat fluxes in most arid region of northwest China are  positive in whole year, so the surface presents as sensible heat source. (3) Taking 97.5°E as the boundary, there are different interannual variation trends in the eastern and western parts of arid region northwest China. The surface sensible heat transfer in the eastern part of the arid region of northwest China increases gradually year by year in four seasons, that in the western part  is similar to that of eastern in autumn and winter, but it is contrary in spring and summer and the climate tendency are -1.15 W·m-2·(10 a)-1 and -2.08 W·m-2·(10 a)-1 respectively. (4) The surface sensible heat transfer has an obvious interdecadal change.  the surface sensible heat transfer is strong (weak) in 1980s (1990s), that in middle part of arid region of Northwest China is weak since 2000, but  strong in its eastern and western parts except for individual stations. (5) The change of surface sensible heat in arid region of northwest China is not only decided by the change of ground-air temperature difference, it also has a close relationship with the changes of ground wind speed and surface condition. In winter, its change is mainly in response to the change of ground and air temperature difference. In spring, the change of ground ground-air temperature difference and surface wind speed play an equally important role. Contrary to autumn, it is prior to the change of surface wind speed and the  ground-air  temperature difference takes the second place in summer. Furthermore, the influence of surface condition on the sensible heat should not be neglected in summer.

• Characteristics of Soil Heat Flux in Different Soil Types in China
• LI Liang;ZHANG Hong;HU Bo;LIU Guang-Ren;LIU Zi-Rui;WANG Yue-Si
• 2012 Vol. 31 (2): 322-328. 
• Abstract ( ) PDF (900KB) ( )
• Utilizing the observed soil heat flux, global radiation and net radiation data during 2004—2007 from the Ecosystem Research Network (CERN) built by the Chinese Academy  Sciences, the diurnal and seasonal variation characteristics of surface soil heat flux for different soil types and their relationship with the global radiation and net radiation are studied. The results show that the soil heat fluxes of cultivated loessial and purplish soils have the largest diurnal ranges of 220～280 W·m-2, while tableland meadow and paddy soils correspond to the least values of 55 W·m-2. The seasonal difference of the soil surface heat flux in different soil types vary from 12 to 28 W·m-2. The sequence from the largest to the least is gray desert soil, cultivated loessial soils, saline soil, red soil, purple soil and swamp soil and soils. Soil heat flux has obvious positive correlation with global radiation and net radiation. The ratio of the soil heat flux to the net radiation at 12:00 (local solar time) is different in different soil types. The tableland meadow soil has the least value of about 8%, while cultivated loessial soil has the largest value of 38%. The ratios of most of soil types are between 15%～20%, which fully shows that the transmission of soil surface heat flux for different soil types is very different.

• Research about the Extreme High Temperature Event and Its Composite Index Based on Stochastic Re-Sort Detrended Fluctuation Analysis
• HOU Wei;ZHANG Da-Quan;QIAN Zhong-Hua;FENG Guo-Lin
• 2012 Vol. 31 (2): 329-341. 
• Abstract ( ) PDF (1704KB) ( )
• Using S-DFA method, the thresholds of extreme high-temperature events from 1961 to 2006 are obtained and spatial-temporal characteristic distributions are analyzed. The effectiveness of S-DFA method is also validated through extreme event detection using the temperature series. Giving a definition composite index of extreme low-temperature event from the angle of predictability， this composite index integrate the information of the frequency and the strength of the extreme low-temperature events, and consider the characteristic of regional climate system. Based on the composite index， China are divided into four different zones by their own rank. The composite index of extreme high-temperature event in the 20th century until the early 1990′s have maintained smooth fluctuations, but after the early 1990′s, the composite indicator has been on the rise, especially in the late 1990′s rapidly rise.

• Characteristics of Water Vapor Transportation and Budget of Winter and Summer in the Yellow River Basin
• LI Jin;LI Dong-Liang;ZHANG Jie
• 2012 Vol. 31 (2): 342-350. 
• Abstract ( ) PDF (1242KB) ( )
• Using the NCEP/NCAR reanalysis data and the observed rainfall data, the water vapor flux, the water vapor convergence (divergence) and water vapor budget in every sub-region of January and July over the Yellow River basin in drought/flood years and multi-year mean are studied. The results indicate that water vapor transport is insignificant in January, while in July the water vapor is transported from Southwest, Southeast and Northwest China to the Yellow River basin, and the lower reach Yellow River of multi-year mean is mainly influenced by the first two airflows. In the flood years, the southwest and southeast water vapor  have obvious impact on middle and lower reaches of the Yellow River basin, while its upper reach region is rarely influenced; In the drought years, the water vapor  transport to neither the upper nor middle reaches of the Yellow River basin, only the southwest water vapor  transports to the lower reach region. Spatial and temporal variations of water vapor budget correspond to that of precipitation over every sub-region, respectively, while the meridional net water vapor flux is the main supply for the water vapor budget and precipitation. The net water budget and the water vapor input to every boundaries in flood years are significantly larger than those of in drought years. In January, the weak water vapor input from the west and the north boundaries is much smaller than the output from the east and the south boundary, leading to moisture divergence; In July, huge amounts of water vapor comes from the west and the south boundary, it results in the water vapor convergence over most sub-region of multi-year mean. But specifically speaking, it results in the water vapor convergence over all sub-region in the flood years, while results in the water vapor divergence in the drought years.

• Characteristic of Tropopause Height over China in Recent 51 Years
• LIU Hui;WEI Zhi-Gang;WEI Hong;LI Zhen-Chao;WANG Chao
• 2012 Vol. 31 (2): 351-358. 
• Abstract ( ) PDF (984KB) ( )
• Using the long term monthly mean pressure and monthly mean pressure data on tropopause of NCEP/NCAR reanalysis data, the spatial distributional and temporal evolution of tropopause height over China in recent 51 years are studied by Empirical Orthogonal Function(EOF) and Rotated Empirical Orthogonal Function(REOF) methods. The results show that the boundary line between the tropical tropopause (the second tropopause) and the polar tropopause (the first tropopause) is on the most southern side of China in February and on the most northern side of China in August. The higher tropical tropopause gradually moves too north since February and reaches the north-edge about 44°N  in August, and then withdraws southward and reaches the south-edge about 29°～30°N in February. Annual variation amplitude of the tropopause height is greater in the region of 29°～44°N in China. There are three main EOF modes of tropopause height field: The first EOF mode is consistently higher (lower) than normal; the second EOF mode is a opposite pattern between southern (northern) region and northern (southern) region; the third EOF mode is a opposite pattern between northern-southern (central) region and central (northern-southern) region. Furthermore, based on the data of tropopause height field, the studied region can be divided into 6 sub-regions by   REOF. They are South China, Xinjiang region, Northeast China, North China, the Yangtze River valley and Tibet Plateau area. The maximum tropopause height generally occurs in summer and the minimum occurs in winter in each region except for South China. In South China, the maximum tropopause height occurs in spring and the minimum occurs in summer. The interannual change and secular trend of the tropopause height show obvious regional differences.

• Influence of the Surface Sensible Heat Flux of North Asian Continent in Winter on Meiyu in Yangtze-Huaihe Valleys
• CHEN Sheng-Jie;LI Dong-Liang;HE Jin-Hai
• 2012 Vol. 31 (2): 359-369. 
• Abstract ( ) PDF (1698KB) ( )
• Based on the monthly mean values of surface sensible heat flux(SSHF) from NCEPⅡ reanalysis data, the onset and end date of Meiyu in Yangtze-Huaihe valleys provided by Jiangsu Meteorological Administration, and the observed daily precipitation at 753 stations from 1979 to 2008, the influence of the SSHF of the North Asian Continent (60°~135°E, 32°~75°N) in Winter on Meiyu and its possible mechanism are analyzed. The results show that the surface of the North Asian Continent in winter is a cold source of sensible heat, which is strong cold air action to the atmosphere. Here, an index WSH is defined as a measurement of the intensity of this cold source, the lower (higher) index indicates the stronger (weaker) cold source. During the strong year of the cold source of the surface sensible heat, the cold air to the north of Meiyu front and the northeast cold vortex in summer is intensified widely, and the longitude circle is also strengthened. Meanwhile the subtropical westerly jet is anomalously southward and the South Asian high is far southeast-ward in July, resulting in the stronger ascending flow over Yangtze-Huaihe valleys, where the upper-level air turning to be drier while the low-level air turning to be wetter dramatically cause a more unstable air layer and severe convective activity. All above contributes to more precipitation and delays the end date of  Meiyu.  The reversal is true for the weaker years of the cold source of the sensible heat. In view of these, the anomaly of SSHF of the North Asian Continent in winter could act as an indicative signal in predicting Meiyu in Yangtze-Huaihe valleys during flood season.

• Analysis on Micrometeorological Characteristic in the Surface Layer of Laohugou Glacier No.12 in Qilian Mountains
• LI Jian;QIN Xiang;SUN Wei-Jun;ZHANG Ming-Jie;YANG Jun-Hua
• 2012 Vol. 31 (2): 370-379. 
• Abstract ( ) PDF (1168KB) ( )
• The micrometeorological variation characteristics, such as temperature, rainfall, specific humility, air pressure, wind, sensible heat flux, latent heat flux and so on, are analyzed based on the observed meteorological data from September 1, 2009 to August 31, 2010, at the elevation of 4 550 m of the Laohugou Glacier No.12 in Qilian Mountains. Due to the influence of the glacier underlying surface, the rising rate of  hourly mean variations of temperature is larger than the decreasing rate, opposite to the seasonal variation. The phase variation of temperature is in advance of wind speed. Precipitation mainly concentrates from May to September, which is 68.1% of the annual amount.The mean wind speed is the largest in winter, the smallest in summer, and in spring it is above in autumn. The glacier wind is heavier than valley wind in spring and autumn, opposite to in summer. It governsin winter and plays an important role in energy exchanges in the land-surface process. Themajor portion of daily mean sensible heat flux is positive, and the latent heat flux is almost negative in all the year, which increase noticeably in the case of higher temperature and larger wind speed. The absolute values of sensible heat  and latent heat fluxes in summer are larger than in winter.

• Temporal-Spatial Distributions of Severe Precipitation Event during Flood Period in Tibet in Last 30 Years
• JIAN Jun;YANG Zhi-Gang;ZHUO Ga
• 2012 Vol. 31 (2): 380-386. 
• Abstract ( ) PDF (842KB) ( )
• Using the daily precipitation data from 38 obseration stations in Tibet during the flood period (from May to September) in 1980-2008, the standard of severe precipitation event is defined and the temporal-spatial distributions of severe precipitation frequency based on REOF, SSA and so on. The results show that the frequency of severe precipitation event decreases from southeast to northwest during the flood period, in general it increases slightly, which decreases in the middle of 1980s, the most significant in the middle of 1990s, then gradually increases. The severe  precipitation  event has five anomalous spatial patterns in Tibet, such as south pattern, Yarlungzangbo pattern, east pattern, north pattern and southeast pattern. The change of severe  precipitation  frequency in each spatial pattern  with time is different. South pattern and southeast pattern appear the decreasing trend, and other three patterns appear the increasing trend. The singular spectrum analysis shows that 2~3 and 5~6 year periods exist among all of 5 patterns for the frequency of severe precipitation event during the flood period in Tibet.

• Analysis of Vorticity during Vortex Producing Snowstorm in North China in Winter
• ZHANG Yuan-Chun;SUN Jian-Hua;FU Shen-Ming
• 2012 Vol. 31 (2): 387-399. 
• Abstract ( ) PDF (1779KB) ( )
• The snowstorm occurred in North China on 2~3 January 2010 was simulated  using WRF model. And potential vorticity and vorticity equation were used to diagnose the developing mechanism of the vortex producing heavy snowfall process in winter. The results showed that, firstly, the weak trough in middle troposphere leaded to lower and surface systems moving from west to east. Secondly, potential vorticity from upper-level intensified development of vortex in middle-lower troposphere. Thirdly, the mean flux and stretching term of the integrated vorticity equation was the main source of vorticity, but eddy flux and like-tilt term was relatively weak. During the mature period of vortex, the vorticity decreased because of the divergence of environmental circulation to vortex area while the vortex moved faster than surrounding air, and to the contrary, vorticity increased for the convergence between environmental circulation and vortex area. During the dissipating period, the vorticity decreased since the loss of the absolute vorticity flux. On the basis of all diagnosis, the  PV  forcing inupper-troposphere, convergence inlower-troposphere and the vorticity produced by environmental circulation are main mechanisms of vorticity developing.

• Analysis on the Moisture Flux of a Rainstorm by Southwest Vortex Using Precipitable Water Vapor Data of Ground-based GPS
• DENG Jia;LI Guo-Ping
• 2012 Vol. 31 (2): 400-408. 
• Abstract ( ) PDF (1161KB) ( )
• Based on the GPS Precipitable Water Vapor (GPS-PWV) data from the ground-based GPS network in Chengdu plain, the observed precipitation at automatic weather stations (AWS) and NCEP reanalysis data, the changes of water vapor in a heavy rainstorm in Sichuan basin during 20~22 July 2008 are analyzed, which is caused by the plateau vortex and southwest vortex. The results show that there is a good relationship between the variation of GPS-PWV and the precipitation, especially in the heavy rainstorm,  the amplitude of GPS-PWV happens before the formation of heavy precipitation while the dramatica decrease of GPS-PWV indicates the end of the precipitation process. As the shown relationship between water vapor flux, water vapor flux divergence and GPS-PWV, the increase of GPS-PWV and its maximum value can better reflect the impact of southwest warm and humid airflow on the changes of water vapor over the Sichuan Basin. The southwest vortex is formed on the basis of the amplitude of GPS-PWV and the following heavy precipitation. During the time of prosperity, there is a center of water vapor convergence in the low level over the Sichuan basin and the GPS-PWV gradually reduced to the lowest level with the eastward shift of the southwest vortex. In summary, the ground-based GPS-PWV can correctly reflect the changes of water vapor for a southwest vortex over the Sichuan basin.

• Climate Characteristic and Formative Cause of Autumn Rain in Weihe River Basin in Recent 50 Years
• XUE Chun-Fang;DONG Wen-Jie;LI Qing;WANG Shi-Gong
• 2012 Vol. 31 (2): 409-417. 
• Abstract ( ) PDF (1048KB) ( )
• Autumn rain is one of the important climate characteristics in the Weihe River basin. With the methods linear trend estimate, EOF, Morlet wavelet analysis, SVD and correlation analysis, the temporal and spatial variation characteristics of the autumn rain in Weihe watershed are analyzed by using the autumn precipitation data at 64 observational stations in the period of 1960-2009. Meanwhile, the interdecadal variations of atmospheric circulation in Eurasia in autumn and relationships between the autumn precipitation and the SST in Pacific ocean,  the snow cover in Tibetan Plateau, and  the atmospheric circulation characteristic values are emphatically analyzed. The results show that the trends of autumn precipitation and rain day number are linear decrease. There is an abrupt change  about 1985, the autumn precipitation and rain day number are more than normal in 1960-1985 and  2001-2009, and are less than normal in 1986-2000. The precipitation and rain day numbers decrease from south to north gradually in this region, and the  precipitation trends at most stations are decreasing but precipitation in Zhangxian, Gangu and Heshui are increas. The evident interdecadal variations of atmospheric circulation in Eurasia in autumn cause the change of autumn precipitation from a strong pattern in 1964-1975 to a weak one in 1986-1999. High pressure ridge in western Europe, trough in westerlies and western Pacific subtropical high are the main influence systems of autumn rain in Weihe River basin. Based on the analysis of the relationships between the autumn precipitation and internal and external factors of atmosphere, a concept model of autumn precipitation prediction in Weihe River basin is built.

• Global Warming and North Edge of Asian Summer Monsoon: Numerical Experiment with Doubled CO₂
• WANG Jia-Wei;TANG Xu;CHEN Bao-De;PENG Yu-Ping
• 2012 Vol. 31 (2): 418-427. 
• Abstract ( ) PDF (1431KB) ( )
• The change of north edge of the Asian summer monsoon under the global warming is investigated using the NCAR CAM3 global atmospheric circulation model through numerical experiment of doubled CO2. The overall large-scale features of the eastern Asian monsoon are captured rather well by the Control_run and doubled CO2experiment. In doubled CO2 concentration experiment, the north edge is more northward, which indicates a stronger monsoon. The analysis demonstrates that the surfacetemperature increasing from enhancedradiative force makes the cyclonic circulation in the lower level of Qinghai-Xizang Plateau stronger, which furtherstrengthens the zonal thermal contrast between sea and land; moreover the moisturecontent is remarkably increased in the North  China. Furthermore, it is shown that the thermal difference between the Northern and Southern Hemispheres hardly changes comparing with the Control_run. Those imply that theinteraction of bothHemisphereshas a relativelysmall impact onthe intensification of the Asian summer monsoonactivity.

• Research of Wind Energy Resource in Jiuquan Region Using MM5 and CALMET Pattern
• WANG Xing;MA Peng-Li;ZHANG Tie-Jun;ZHOU Rong-Wei
• 2012 Vol. 31 (2): 428-435. 
• Abstract ( ) PDF (942KB) ( )
• The wind energy resources of 1 km×1 km resolution in Jiuquan region in Gansu Province from June 2009 to May 2010 was simulated using the mesoscale model MM5 combined with wind diagnosis field model CALMET and 1°×1° reanalysis data of NCEP. The comparison of the simulated and observed wind speeds shows that the relative errors of  flat site and away from the mountain are smaller， thecomplicated topography is bigger. The relative errors in seven wind towers of ten wind towers are no more than 10%, the values ofother three towers  are within 20% too.The seasonal changes of wind speed and wind power density display that the data of spring is the biggest, then autumn and winter,  and the summer is the smallest. This seasonal variation has a close relation withterrain, physiognomyand affected weather system. The wind speed increases with the increasing of  height in Jiuquan region, especiallyin low latitude area, namely the most west part of Hexi corridor and north part of Jiuquan. Through the analysis of wind speed representativeness in the simulated year, there is  stronger wind in Jiuquan region in the simulated year. If the average wind state is further analyzed,  some correction of the simulated results should be done.

• Analyses on Variation and Cause of Surface Solar Radiation in Beijing, Tianjin and Hebei Regions from 1960 to 2005
• ZHENG You-Fei;YIN Zhao-Yin;WU Rong-Jun;LIU Jian-Jun
• 2012 Vol. 31 (2): 436-445. 
• Abstract ( ) PDF (1073KB) ( )
• The temporal and spatial variations of global radiation in Beijing, Tianjin and Hebei regions from 1960 to 2005 are analyzed. The results shows that the phenomenon ‘from dimming to brightening’ is not observed in this area, while the global radiation decreases during spring and winter but increased during summer and autumn. However, two different regions could be distinguished based on the variation of global radiation: The increase of trend coefficient in eastern region is 1.016 MJ·m-2·mon-1·(10 a)-1 and their decrease in western region is 10.092 MJ·m-2·mon-1·(10 a)-1. It is also found that the increase of global radiation is caused by two primary factors: One is the increase of    which follow with the decrease of cloud amount and precipitation and the other is the decrease of aerosol optical depth. Besides, the major cause of the decreased radiation in western area is the little change of cloud amount, precipitation, aerosol optical depth and sunshine duration.

• Analysis on Cloudiness Change in Qinling Mountain Region and Its Possible Reason in Past 60 Years
• DU Chuan-Li;YU Xing;LI Xing-Min;WANG Fan-Qiang;PENG Yan;DONG Yan;DONG Zi-Peng
• 2012 Vol. 31 (2): 446-455. 
• Abstract ( ) PDF (1198KB) ( )
• Using the different meteorological element data between mountain and plain weather stations, monsoon index and sea surface temperature (SST), the changing characteristic of cloudiness in Qinling mountain region and its reasons have been investigated. The main conclusions can be summarized as follows: (1) The trends of low  and total cloudinesses in Qinling mountain region are decreasing, for low cloudiness, decreasing rate of mountain station(Hua mountain station) and plain stations(Huaxian and Xi′an stations) are -1.74%·(10 a)-1, -1.56%·(10 a)-1, -4.23%·(10 a)-1, respectively at nighttime, and -0.73%·(10 a)-1, -1\^94%·(10 a)-1, -4.62%·(10 a)-1 in daytime. (2) For total cloudiness, decreasing rate  mountain station is more than that at plain station. (3) For different seasons, low  and total cloudinesses at mountain  and plain stations are all decreasing, except for summer at plain station. (4) The change reasons  for cloudiness in Qinling mountain region are: Firstly, because of the cooling effect of aerosol, the absorbed solar radiation from surface  redues, the local convection become weaken and  the low cloudiness in Qinling mountain region decrease; Secondly, the strengthening of the Western Pacific Subtropical High, has negative correlation with the total cloudiness in  Hua mountain.

• Uncertainty for Change of Mean Surface Air Temperature in China in Last 100 Years
• DU Yu-Gang;TANG Guo-Li;WANG Yuan
• 2012 Vol. 31 (2): 456-462. 
• Abstract ( ) PDF (771KB) ( )
• Uncertainty in mean surface air temperature is an important factor for the research of climate change. It can be divided into four groups: Station error, bias error, sampling error and limited coverage error. The uncertainty affecting the annual mean surface air temperature in China during 1905-2006 is estimated. The results show that the largest contribution to uncertainty is limited coverage error before 1960s. The influence of bias errorincreases withthe acceleration of urbanization process in China after 1970s. Therefore, the reducing limited coverage error is the key factor of detecting true climatic signal in China. In addition, the urbanization effect can not be ignored in recent years. As for trend, the total uncertainty in China has been decreased since 1905. Comparing with the global, trends of uncertainties in these two regions aresimilar to each other, whichare both characterized by a decline. Therefore, in order to detecting true climatic signal, we must pay more attention to uncertainty especially the uncertainty in the early period bothin China andglobe.

• Temporal and Spatial Characteristics of Extreme Dry Spell in Each Season in Southeast Guizhou
• GU Xin;YANG Shao-Hong;HUANG Da-Wei;PAN Ping-Zhen
• 2012 Vol. 31 (2): 463-469. 
• Abstract ( ) PDF (949KB) ( )
• The spatial and temporal characteristics of extreme dry spell are analyzed  using the daily precipitation data at 16 stations in Southeast Guizhou from 1961 to 2009. Using EOF， Mann-Kendall catastorophe test， linear trend estimate and others, the maximum continuous rainless days (daily rainfall less than 0.1 mm) of each season are analyzed. The results show that the spatial and temporal variation characteristics of the extreme dry spell in each season of Southeast Guizhou have a great difference， the most days of extreme dry spell taken place in autumn， the least days, in spring， and there is the non-uniformity characteristic in a year. Under the control of large-scale weather system， the extreme dry spell of each season had the same frequency， but it is abnormal high in east central of Southeast Guizhou, the influence of the weather systems in different seasons on the sub-region in Southeast Guizhou is of significant localization and stage. After 21st century, the extreme dry spell appearsthe  increasing trend in spring， autumn and winter， but not obvious in summer.

• Relations between Spring Precipitation in Shanxi and Anomalies of 500 hPa Circulation Field and SST in Pacific Ocean
• ZHOU Jin-Hong;JING Xiao-Jun;REN Hui-Long;LI Fen
• 2012 Vol. 31 (2): 470-476. 
• Abstract ( ) PDF (1031KB) ( )
• Based on the monthlyprecipitation data at 62 meteorological stations in Shanxi Province in spring from 1961 to 2008, NCEP/NCAR reanalysis data and NOAA sea surface temperature (SST) data in the Pacific Ocean, the relations between the spring precipitation  in  Shanxi  and anomaliesof   the 500 hPa circulation and Pacific Ocean SST are studiedusing the SVD method, Monte Carlo statistical test and composite analysis methods. The results show that when  500 hPa mean geopotential height field in spring appears  positive anomalies over the North Europe, the Japan Sea and eastern North Pacific Ocean, and the negative anomalies over west Siberia and the North Pole, it always has contemporaneous more precipitation in spring in Shanxi, otherwise spring precipitation less; whenthe mean SST in middle and eastern equatorial Pacific is abnormallyhigh and the mean SST in the southeast of  North Pacific  is abnormallylow in spring, and the areas  have the similar distributions of SST anomaly in previous winter,it alwaysappears more precipitation in Shanxi in spring, otherwise spring  precipitation less. The weakened 850 hPasouthwind in spring in the eastern China of 110°～120°E may cause contemporaneous less precipitation in Shanxi Province.

• Diagnostic Analysis of Snowstorm in Shanxi Province in November 2009
• WANG Zheng-Wang;YAO Cai-Xia;LIU Xiao-Wei;ZHANG Jian-Hong
• 2012 Vol. 31 (2): 477-486. 
• Abstract ( ) PDF (1722KB) ( )
• Using the snowfall data at 109 observation stations in Shanxi Province, the FY-2C satellite cloud image and  radar image in North China, the circulation background,  the middle and lower altitude system dispositions,  the relative humidity of physical quantity field, the divergence and the spatial-vertical cross-sections of vertical velocity field,  the snowstorm occurred on 9～13 November 2009 were analyzed. The results showed that the storm weather took  500 hPa southern branch trough and the westerly trough one before and after  influence as background; the favourable  system disposition in the middle and lower levels provided the conditon for continuous heavy snowfall; In the severe snowfall time interval, the spatial-vertical cross-sections of physical field  showed that  the relative humidity center  more than 80% uplifted over 200 hPa at 36°N, the unstable structure of upper divergence and lower convergence were formed in the ranges of 900～200 hPa,  34°~40°N, Shanxi Province was in ascending motion zone, the maximum negative center (-36 × 10-3 hPa·s-1) was on 400～500 hPa, this configuration formed the favourable condition of heavy snowfall. The evolution of FY-2C cloud image was similarly to the radar reflectivity factor over   North China, the severe snowfall were mainly produced by three times wide ranges of middle and lower cloud systems and strong echo moved to the east.

• Analysis on of Sand-Dust Weather Change and Transportation Path in Beijing Region in the Past 60 Years
• ZHANG Tai-Ren-;ZHANG Ming-Wei;JIANG Jian-Ying
• 2012 Vol. 31 (2): 487-491. 
• Abstract ( ) PDF (911KB) ( )
• The frequency of sand-dust weather is decreasing in general, especially the duststorm, in the Past 60 years. The  meteorological data in 1951-2010 were used to analyze the transportation path of sand-dust weather affecting Beijing region. The result shows that most of sand-dust weather affecting Beijing has passed through a region in North China. The north boundary of the region is from Zhangye and Minqin of Gansu Province, Otog Front Banner of Inner Mongolia, Datong of Shanxi Province to Beijing, and the south boundary is from Xilin Hot of Inner Mongolia, Hunsandake desert, Zhangbei of Hebei Province to Beijing.

• Characteristics of Secular Change and Base State of Temperature in Harbin
• WANG Yong-Bo;ZHANG Zhi;ZHOU Xiu-Jie
• 2012 Vol. 31 (2): 492-497. 
• Abstract ( ) PDF (655KB) ( )
• Based on the temperature data in Harbin from 1881 to 2009, the climate base state of seasonal and annual mean temperatures and its climate variability features have been examined. The results indicate that the summer temperature anomaly subsequent after the 1980s is significant increase. The lower wintertime temperature variability in the recent warm background shows that a period of warm winter persistence is likely in most years in Harbin. The change characteristics of mean temperature and mean maximum (minimum) temperature as well as the daily temperature range in Harbin in recent 49 years have been analyzed. The result shows the seasonal and annual mean temperatures have remarkably increased in Harbin in recent 49 years, with the most obvious warming occurring in winter. The mean maximum (minimum) temperature has increased in all season, generally, increase in mean minimum temperature is more dominant that of mean temperature and increase in mean temperature is more dominant that of mean maximum temperature.

• Influence of Climate Change on Agricultural Planting Structure in Shaanxi, Gansu, Ningxia and Qinghai in Northwest China and the Adjustment Scheme
• DENG Zhen-Yong;ZHANG Qiang;ZHAO Hong-Yan;WANG Run-Yuan;SHI Zhi-Juan;FANG Jian-Gang;LI Lin;LI Yan-Chun
• 2012 Vol. 31 (2): 498-503. 
• Abstract ( ) PDF (786KB) ( )
• Based on the meteorological data at 141 weather stations in Shaanxi, Gansu, Ningxia and Qinghai, the characteristics of climate change  are analyzed. The result shows that, the increasing temperature in these regions is the main trend and the annual mean temperature increases 0.27 ℃·(10 a)-1  and the abrupt point is in 1996. The annual precipitation had decreased since 1961 and the abrupt point was in 1986. The mean  annual precipitation from 1987 to 2008 was less 20~40 mm than that from 1961 to 1986. The annual precipitation in the region of eastern Yellow River was decreased 10~ 40 mm·(10 a)-1   and increased 10 mm·(10 a)-1 in the region of western Yellow River. It showed that decrease trend was more obviously than the increase. The trend of climate turning dry and warm became weak in 21st century. Based on the characteristics of nature resource in different regions and the impact of climate change on crops, the adjustment scheme were provided for 13 regions in Shaanxi, Gansu, Ningxia and Qinghai  with the method of systematic planning theory and climate ecological similar principles. In order to promote agriculture structure adjustment and get obvious ecological social and economic benefits,  four safeguard measures were proposed.

• Study on the Formation and Evolution of ‘6.3’ Damage Wind
• WANG Xiu-Ming;YU Xiao-Ding;ZHOU Xiao-Gang;NIU Shu-Zhen
• 2012 Vol. 31 (2): 504-514. 
• Abstract ( ) PDF (1790KB) ( )
• Adamage wind event occurredon 3 June 2009 over an extensive area, which cause great damage and casualty in Shangqiu and North of Anhui and Jiangsu Province. The convective stormdevelopsfrom superscell to bow echo squall line, severe convection last more than seven hours. It′s hard to forecast the storm′s evolution and the surface damage wind. The mesocale environment, the storm structure and the interaction between storm and circumstances are analyzed, the results are as follows: (1) The mesoscale circumstancesare favorablefor ‘Derecho’ where Shangqiu damage wind occurred. (2) Shangqiu wind storm is triggered by gust front of old thunderstorm clusters, when it moves to the place in where  is enough moisture. Storm quickly  developed into supercell storm with strong middle altitude radial velocity. The surface wind damage was driven by downdrafts incorporation of multi-supercell; (3) The reasons of strong long-life squall line are self-organization structure of squall line; interaction between squall line and surrounding inflow jet; incorporation of line-shapecumuluswhich was triggered by dryline and overlappeddisturbances again and again; (4) The damage winds of bow echo are driven by strong downdraft divergenceflow, strong cold pool outflow and evaporation of stratus hydrometeors. From estimate of radial velocity it can see that the effectof these three elements is almost equal. The incorporation of cold pool plays an important role of damage wind in Yongcheng.

• Contrast of Radar Information between Two Destructive Gales Occurred in the East of Henan Province on June 3 and July 17
• ZHANG Yi;ZHAO Zhi-Yu
• 2012 Vol. 31 (2): 515-529. 
• Abstract ( ) PDF (2430KB) ( )
• Using the conventional and non-conventional data,  the gales occurred in the east of Henan Province on June 3, 2009 (‘6.3’ process for short)  and July 17, 2010(‘7.17’ process for short) are analyzed. The result shows that though the upper-level trough and the northeast wind behind trough cause from  cold air of Northern China to south both in ‘6.3’ and ‘7.17’ processes, the temperature in middle troposphere rapidly fell, which cause the instability of atmosphere and the vertical wind shear of upper and lower tropospheres, and then the downward transport of momentum cause the occurrence, development, maintenance and spread of strong convection. According to radial velocity of radar and wind profile,  ‘6.3’ process is of  such squall line features: The strong echo region is in the front of echo region and likes a bow, moving speed of the echo is fast, and convergent radial wind. However, ‘7.17’ process forms much strong local convection cells in mesoscale vortex cloud system, contributing to heavy rain, thunder and lightning, severe local storm and so on.

• Analysis of Cloud Microphysics Structure over Hebei Region during Autumn of 2007
• ZHANG Yu;YIN Yan;SHI Li-Xin;DUAN Ying;WU Zhi-Hui
• 2012 Vol. 31 (2): 530-537. 
• Abstract ( ) PDF (806KB) ( )
• The cloud microphysical properties are analyzed based on the aircraft measurements conducted over Hebei region, Northern China during autumn of 2007. Theresults show that thedroplet number on the bottom layer of altostratus is greater than that on the upperlayer, and the particle diameter increases with height. The maximumn content of liquid water is 0.25 g·m-3, and the average content of liquid water is 0.025 g·m-3at the bottom. It is also shown that the concentration of cloud droplet onthe upper layer werehigher than that on the bottom, the droplet number concentration ranges from10to 80 cm-3. The diameters are around7.56μm, with height increasing  the particle diameter increasesfirst and then decreases. Cloud droplet spectrum narrowsand the disappearance of two peaks are cloud droplet related with the change of water content. Comprehensive analysis of cloud microphysics structure suggests that planning in advance the flying pattern is possibly not the best scheme for cloud seeding in some cases, and the seeding operation should be designed based aircraft condition and  weather as well as cloud conditions. In view of the temperature, it could be considered using the catalytic of liquid nitrogen or liquid CO2.

• Analysis on Microphysical Characteristic of Stratocumulus Precipitation in Shanxi Province in Summer
• FENG Qiu-Juan;LI Pei-Ren;JIN Li-Jun;HOU Tuan-Jie;WANG Gong-Wa
• 2012 Vol. 31 (2): 538-546. 
• Abstract ( ) PDF (1262KB) ( )
• The microphysical data of cloud measured by the airborne DMT probes in a precipitation stratocumulus on 17 July 2008 in Shanxi Province are analyzed. The microphysical characteristics of cloud in vertical direction during both ascending and descending stages   of aircraft are presented through analyzing number concentration, mean diameter, shape and size distribution of cloud particles. The results show that the cloud is Ac configuration during ascending stage of aircraft and Ac-Sc configuration during descending stage of aircraft. Number concentrations sampled by CDP and CIP are larger and maximum number concentration are respectively 236 cm-3and 9.74cm-3. Horizontal change of microphysical parameter of stratocumulus  shows obviously inhomogeneous features. During ascending stage of aircraft, the raindrops are mainly from ice particle melting. The cool cloud processes are dominant. The radar echoes exist 0 ℃ isotherm bright band. During descending stage of aircraft, combination the cool cloud processes of altocumulus and the warm cloud processes of stratocumulus are distinct.

• Feature and Mechanism of the Foehn Weather on East Slope Taihang MountainsⅠ: Statistic Feature
• WANG Zong-Min;DING Yi-Hui;ZHANG Ying-Xin;WANG Cong-Mei;LI Jiang-Bo;GU Yong-Li
• 2012 Vol. 31 (2): 547-554. 
• Abstract ( ) PDF (1214KB) ( )
• Using the observation of two-element AWSs in Hebei Province, multi-elementAWSs in  Beijing and Tianjin,the foehn occurredon east slope of Taihang Mountains is detailanalyzed according to hourly temperature variation. The results show that: The foehn has obvious seasonal and diurnal variations;The distribution features is clear at night, strong foehn usually occurs within 50 km on east side of Taihang Mountains, but weak foehn can reach up Taihang Mountains to the  east 100 km area. There are two foehn centers in northernand southern parts of Taihang Mountains;the foehn is closely related with wind direction,foehn caused northwest wind is mainly inthe northern parts of Taihang Mountains, west ward wind mainly affectfoehn inthe southern parts of Taihang Mountains, while the southwest wind mainly affects foehn in the middle part of Taihang Mountains; Foehn strength is somewhat corresponding to wind speed; it has obvious gustiness,and often appears a clear dark bandin infrared cloud image. The heating zone caused by foehnmay move to east or southeast which  cause rapid rising  temperature in Hebei Plain.Key words: Foehn; East slope of Taihang mountains; Infrared satellite cloud image

• Feature and Mechanism of the Foehn Weather on East Slope Taihang Mountains Ⅱ: Case Analysis of the Effects of Lee Wave on Foehn Occurring and Moving
• WANG Zong-Min;DING Yi-Hui;ZHANG Ying-Xin;FAN Jun-Hong;ZHANG Shou-Bao;TIAN Li-Qing
• 2012 Vol. 31 (2): 555-561. 
• Abstract ( ) PDF (1478KB) ( )
• One typial case of foehn on the east slope of Taihang Mountains is simulated  using ARW-WRF V3.3. The result shows that the formation and movement of the foehn is closely related to the lee wave. Based on the relation, a conceptual model of foehn formation  on the east slope of Taihang Mountains is proposed. Lee waves develop on the east slope of Taihang Mountains while the northwestly or westly flow goes over the mountains, basins and plateau in the west of Taihang Mountains. The adiabatic heating is due to the decent component of lee waves and the compression warming effect on the lower atmosphere is caused by the downdraft, which lead to the foehn on the east slope of Taihang Mountains. Being one kind of gravity wave, lee waves can propagate downstream, which results in the foehn warming areas moving eastward with the downdraft propagating downstream at the same speed. Theoretical analysis shows that Scorer number decreases upward discontinuously, meaning that the atmosphere is stable and the obvious wind shear exists in the lower atmosphere, which is helpful to the formation of lee wave.

• Application of VIL Product in High Mountain Radar
• ZHANG Chong-Li;QIAN Bao-Min;HE Wei-Dong;YANG You-Ren;LAI Yun-Hua
• 2012 Vol. 31 (2): 562-567. 
• Abstract ( ) PDF (630KB) ( )
• Using the hail observation data, short\|time heavy precipitation data, hail disaster information provided from  Civil Administration Department and the observational data from CINRAD/CC radar in Lijiang in 2006-2009, the vertically integrated liquid water content(VIL） was statistically analyzed. The results show that, if VIL value is greater than 5 kg·m-2, the severe convection weather will occur; if VIL value is greater than or equal 21 kg·m-2, it indicates that the possibility of  hail occurrence is enormous, which  start the key values of hail suppression operations. The VIL value of hail cloud is much larger than the VIL value of common convective cloud in short\|time heavy rainfall. The VIL value will appear obvious abrupt before the shooting hail. Usually the VIL values of hail are more than 37 kg·m-2, but the VIL value in   closer or farther region distance from the radar station will be underestimated, and  the VIL value  less than 37 kg·m-2 will occur shooting hail.

• Capacity Analysis on China\|Made HS02 Humidity\| Sensitive Capacitor Sensor
• LI Wei
• 2012 Vol. 31 (2): 568-580. 
• Abstract ( ) PDF (1520KB) ( )
• In order to improve upper\|air humidity observation data quality, the capacity analysis of HS02 humidity\|sensitive capacitor sensor has been made through participating in the 8th WMO Yangjiang radiosonde international intercomparison, in which multi\|sonde with the same balloon model has been applied to total 29 launching, as well as Swiss Snowwhite dewpoint humidity radiosonde as reference. Moreover, three different methods are applied for the analysis, considering pressure factor, temperature factor and mixing factors (pressure, temperature and humidity). The analyzed results are as follows: (1) In terms of precision and stability, big gap still exist between HS02 humidity sensor and foreign advanced humidity sensor, especially in low temperature environment. (2) Regarding temperature segment analysis, HS02 humidity sensor have wet bias both in daytime and nighttime except for the 2 temperature segments in daytime(above 0 ℃ and below \|30 ℃). (3) With respect to humidity segment comparison analysis, the random error of HS02 humidity sensor show change trend with ‘>’ type, i.e., big error for middle level humidity segment and decreasing errors for high and low level humidity segments. In future, low temperature performance improvement and correction algorithm for HS02 humidity sensor will be focused as well as stability and consistency improvement, aiming at acquiring high quality data of upper\|air humidity observation.