Plateau Meteorology

Current Issue

28 August 2015, Volume 34 Issue 4   
  • A New Plateau Monsoon Index Based on Wind Dynamical Normalized Seasonality and Its Application
  • ZHANG Shaobo;Lü Shihua;AO Yinhuan;MA Di
  • 2015 Vol. 34 (4): 881-889.  DOI:10.7522/j.issn.1000-0534.2015.00067
  • Abstract ( ) PDF (9350KB) ( )
  • By using the reanalysis data of ERA-interim and assimilated data of precipitation in the period of 1979 to 2012, a new plateau monsoon index, named IPMzhang, was defined, based on the wind dynamical normalized seasonality index. After compared with existing monsoon indices, IPMtang, IPMqi and IPMxun, the following conclusions were given. Each index could well reflect the activity of the plateau monsoon and its relationship with precipitation on the Qinghai-Xizang Plateau(QXP) and its surrounding areas. When compared with IPMtang and IPMxun, IPMqi and IPMzhang showed better relationships with precipitation at a more broad significant area on the QXP under high resolution data. The correlation coefficients of IPMzhang were a little smaller than that of IPMqi, but IPMzhang showed bigger correlation coefficients in the southeast part of the QXP, meaning that IPMzhang could well reflect the summer precipitation there. Composite analysis also showed that abnormal water vapor convergence was found in the years monsoon was strong. It mainly distributed at the central part of the QXP in IPMtang and IPMxun, over almost all of the QXP in IPMqi, and over the southeast part of the QXP in IPMzhang. It was IPMzhang that showed a more proper distribution of the abnormal water vapor convergence on the QXP, leading to a better correlation with the summer precipitation of southeast QXP. In a word, the new defined monsoon index on the QXP could well reflect the summer precipitation on the QXP, especially for the southeast part of the QXP where more people live.
  • Evaluation and Comparison of Two Double-Moment Bulk Microphysics Schemes Using WRF Single-Column Model
  • MEI Haixia;SHEN Xinyong;WANG Weiguo;HUANG Wei
  • 2015 Vol. 34 (4): 890-909.  DOI:10.7522/j.issn.1000-0534.2014.00113
  • Abstract ( ) PDF (6246KB) ( )
  • Two double-moment Bulk Microphysics Schemes, Milbrandt 2-mon(MY) and Morrison 2-mon(MORR), were compared using the WRF single-column model during the period of the Tropical Warm Pool International Cloud Experiment. Results from the control simulations with the default settings of the two microphysics schemes in the Weather Research and Forecasting(WRF) model were able to reasonably reproduce the characteristics of the rain rate, the liquid water content, and the frozen water content, as compared with observations and cloud resolving model(CRM) results. The surface downward longwave radiation and outgoing longwave radiation were very close to observations as well. There is little difference in the macro-and micro-physical properties of the raindrops but a large divergence in the mixing ratio of cloud droplets between two schemes throughout the whole period. In the MY scheme, Ice crystals are dominant in ice clouds while snow particles make more contributions to the ice clouds in the MOR scheme. On a micro level, in the MOR scheme, water clouds contain more smaller cloud droplets while ice clouds are made up of less bigger ice crystals than those in the MY scheme. The distribution differences in ice clouds between two schemes are closely related with conversion rates of microphysical. Analyses of the conversion terms of microphysical processes suggest that ice crystals in both schemes are mainly related to processes of deposition growth, autoconversion of ice crystals to snow, collection by snow and sedimentation during the active monsoon period. The dominating conversion terms of snow in MY scheme are more various than those in the MOR scheme with deposition growth and sedimentation processes included in two schemes. The differences in vertical distribution and magnitude of the main conversion terms are pretty consistent with the composition features of ice clouds simulated by two schemes during the active monsoon period. In the depressed monsoon period, ice crystals in both schemes are dominated by deposition growth and sedimentation processes with ice nucleation in deposition mode and condensation freezing mode playing an equally important role only in the MY scheme. Snow clouds in the MOR scheme develop stronger with more kinds of primary conversion terms about one order of magnitude higher than the MY ones during the depressed monsoon period.
  • Terrain Construction and Experiment for Numerical Model Based on High Resolution Terrain Data
  • HE Guangbi;PENG Jun;TU Nini
  • 2015 Vol. 34 (4): 910-922.  DOI:10.7522/j.issn.1000-0534.2014.00022
  • Abstract ( ) PDF (10565KB) ( )
  • Based on high resolution terrain data, terrain experiments using different terrain disposal methods, including WRF synthetic terrain disposal method(TESTC), Chebyshev polynomial filtering method(a representative experiment TEST5) and five points weighed average method(TEST7) have been done for an heavy rainstorm occurred in Sichuan during 20-22 July 2008. The results show as follows: (1) Using terrain data at different resolutions and adopting different terrain filtering methods have different effects on the prediction results of numeric weather prediction model. Comparatively, based on high resolution terrain data, Chebyshev polynomial filtering method of using 90 truncation rank shows a slight predominance over other methods. (2) Three kinds of terrain disposal methods can predict main precipitation area and intensity. Although precipitation intensity simulated by TEST5 is stronger than the real, simulated precipitation evolution and precipitation area are closer to the real than that of TESTC and TEST7. As to overall simulation effect, TEST7 is between TESTC and TEST5. (3) Different terrain deposal schemes bring about changes to the model terrain altitude and slope of basin and surrounding area, and such changes impact on precipitation areas, intensities and evolutions by working on physical elements going with meso-scale systems activities. (4) Due to differences of terrain disposal, in the east basin where terrain gradient is bigger, topographic perturbation boosts up wind field fluctuation and TEST5 brings about bigger east-west wind-shear. The wind convergence strengthens low vortex and ascend motion, inducing more low-layer vapor being transported to upper air. The intensity of low vortex simulated by TEST5 is stronger and the low vortex position is more eastward, leading to stronger precipitation intensity and more eastward precipitation position than TESTC and TEST7.
  • Numerical Simulation of Transient Land Surface Process over Desert-Steppe Transitional Zone in Arid Areas Using Community Land Model
  • YANG Yang;ZUO Hongchao;YANG Qidong;DU Bin;WANG Xiaoxia;WANG Mingxing;WU Jianjun
  • 2015 Vol. 34 (4): 923-934.  DOI:10.7522/j.issn.1000-0534.2014.00105
  • Abstract ( ) PDF (2592KB) ( )
  • To study the transient change of desert-steppe transitional zone, a single point simulation experiment has been done by using the Community Land Model version 4.0 of NCAR(CLM4.0) and the observed data of Microclimate and Evaporation Experiment during July to September 2012. The simulation capability of the model was test by comparing the simulated values with the observed ones. The results showed that:(1) The results showed that:CLM4.0 model can successfully simulate the variation of the surface radiation, turbulent fluxes, soil temperature and water content with the transient changes over the underlying surface, while there are deviations between the two. In the dry and moist surface conditions, deviations between simulated and observed values of the reflected radiation is small, while the grass surface model simulations higher value compared to the observed values;CLM4.0 simulate the trend of surface longwave radiation, but deviations exist on noon and night. (2) The correlation coefficient between the simulated turbulent fluxes and observed values reached above 0.85, but the simulated values are higher than the observed values. (3) The simulated soil temperature and water content are smaller than the observed values. The CLM4.0 has a poor performance of the simulated soil moisture changes caused by heavy precipitation process. Developing applicable soil porosity parameterization schemes over the arid desert-steppe transitional zone, improving soil thermal and hydraulic conductivity simulation can help to improve simulation performance of soil temperature and water content over such underlying surface.
  • Moist Helicity Indexes Selection and Checking in Chengdu Region for Heavy Rainfall Based on the Fine Data
  • NIU Jinlong;HUANG Chuhui;LI Guoping;TANG Qiankui
  • 2015 Vol. 34 (4): 942-949.  DOI:10.7522/j.issn.1000-0534.2014.00053
  • Abstract ( ) PDF (5030KB) ( )
  • In order to better improve the heavy rain forecast accuracy in Chengdu area (30.1°-N31.5 °N, 103°E-104.9°E, samehere in after), based on T639 high resolution (0.28°×0.28°) data and the data of encrypted automatic stations of Chengdu, 15 cases of heavy rainfall indexes for moist helicity in flood season from July to September in 2011 and 2012 were analyzed by statistical method, included the moist helicity indexes of 3 hours, 24 hours strong precipitation occurrence, development and falling area distribution. Two cases of strong precipitation process in Chengdu Region were checked out and scored by using these criteria and threw into the business forecasting work in the flood season. The results showed that distribution of 700 hPa or 850 hPa moist helicity can give good indication to the distribution of rainfall. Heavy rainfall appeared in the positive and negative moist helicity value isoline concentration areas on 700 hPa and close to the positive side, but in the positive area on 850 hPa. When regional heavy rainfall occurs, moist helicity values reached the number of index values(20×10-11~80×10-11 Pa·s-3) for 5~8 times or more in 3 hours interval forecasting field; When the moist helicity values reached the number of index values(20×10-11~140×10-11 Pa·s-3) for 5~8 times or more in 3 hours interval forecasting field, regional torrential rainfall occurs; When moist helicity values for 300×10-11~500×10-11 Pa·s -3 appeared in different levels, local strong convective weather, such as wind, short-time strong rainfall would possible happen.
  • Relationship between Indian Ocean Dipole and Autumn Rainfall in West China
  • LIU Jia;MA Zhenfeng;YANG Shuqun;XU Jingxia
  • 2015 Vol. 34 (4): 950-962.  DOI:10.7522/j.issn.1000-0534.2014.00107
  • Abstract ( ) PDF (5671KB) ( )
  • The relationship between the Indian Ocean Dipole(IOD) and autumn rainfall in West China was examined statistically. The results show as the seasonal lock of IOD, there is a significantly correlation between the Indian Ocean Dipole and the autumn rainfall in West China: positive correlation develops in spring and summer, and stable in autumn, it is consistent with the delays associated in summer, but the correlation weakens and inverse in early winter. During the occurrence of positive IOD episode, the southwest(cyclonic) anomalies in the middle(lower) troposphere over West China, and the equatorial easterly wind anomaly. These circulation anomalies are related to the above normal precipitation in West China. Moreover, during the occurrence of positive IOD episode, most areas of Huaxi are moisture divergence in winter and spring, but northeastern Sichuan, Guizhou and Chongqing are moisture convergence in summer and autumn, and the water vapor transport relying on the southwest air in Bay of Bengal and easterlies outside the Western Pacific subtropical. In positive IOD episode, OLR increased. The positive phase of the summer IOD provides a potential valuable signal for predicting the autumn precipitation in West China, and the positive phase of the autumn IOD play the role of continuation of development in autumn rainfall.
  • Influence of Frequency Assimilation with Radar Data in Southwest Vortex Rainstorm
  • QIN Yuefeng;GU Jianfeng;WU Zheng;LIU Haiwen;CHEN Guichuan;ZHANG Yaping
  • 2015 Vol. 34 (4): 963-972.  DOI:10.7522/j.issn.1000-0534.2014.00050
  • Abstract ( ) PDF (7904KB) ( )
  • In order to analyze the effect of rainfall forecast and initial field with the radar data assimilation and different assimilating intermittence in the Southwest Vortex rainstorm process, this paper illustrates the single time and multiple times cycle assimilating experiments in the southwest vortex rainstorm process on 21 July 2012 by assimilating the Chongqing Doppler radar data with the three-dimensional variable data assimilation system (ARPS-3DVAR) and complex cloud analysis scheme of the ARPS model. The result show that: (1) Assimilating radar data, model initial field depict the strong center and distribution of the echo, increasing the meso- and micro-scale systems information. Multiple times cycle assimilation experiments have β meso-scale cyclonic vortex, and work with the lower layer convergence, it enhances the ascending motion and develops the southwest vortex. (2) In prediction field, it greatly improve the situation that no rainfall at the period forecast after assimilating radar data. The 18 min assimilation intermittence experiment does the best rainfall forecast and gets the highest score, as is followed by 12 min, 6 min, single time and 24 min assimilation experiment. (3) The maximum vertical velocity reach maximum value by forecasting 18 min after continues assimilating, it shows that the model takes 18 minutes to adjust a suitable dynamic and thermodynamic constrains among different variables and to achieve a balance condition.When cycle assimilation is shorter or longer than 18 minutes, the mode will be badly effect.This may be the reason why the 18 min assimilation experiment have a better forecast of the rainfall and the highest TS score.
  • Comprehensive Analysis on the Severe Convective Weather Situation Configuration and Its Particularity in Northwest China
  • XU Dongbei;XU Aihua;XIAO Wei;SHA Honge;WAN Xueli;CHE Yuchuan;JI Huimin
  • 2015 Vol. 34 (4): 973-981.  DOI:10.7522/j.issn.1000-0534.2014.00102
  • Abstract ( ) PDF (5104KB) ( )
  • By using the precipitation data of the main convective weather processes from the year of 2004 to 2010 in Northwest China, the basic situation configuration of northwest convective weather is divided into three categories by different dominant factors. And, we analyzed the salient features of these three configurations in the field of synoptic-scale environment and the different roles which these features are played in mesoscale convective systems. Meantime, we summarized the main differences among these configurations and also the differences with other regional convective weather configurations. The primary conclusions are as follow: The strong convective weather which is forced by upper air cold advection shows that cold advection may extend downward from 300 hPa to 700 hPa, and 850 hPa is mostly weak warm advection. Compared such kind of convective weather with that occur in the central, eastern of China, temperature lapse rate in the lower troposphere is greater; instability stratification can be stronger in the afternoon;and LFC is higher. Regional convective weather is often associated with ground humidification after large-scale precipitation or low altitude warm air moving northward;local strong convective weather is associated with ground uplift of complex terrain and uneven distribution of water vapor. The strong convection weather which is forced by low level warm advection shows that warm advection plays a dominant role in the lower and wet layer extends from ground upward to near 500 hPa, LFC height is lower significantly. The temperature lapse rate in the lower troposphere is less than the rate in the first situation configuration. The most notable feature of the baroclinic frontogenesis convective weather is the intense interaction between cold and warm air in the lower level, which accompanied with significant temperature frontal zone and frontogenesis. Moisture condition is better than the first situation configuration, vertical wind shear is stronger than the previous two categories significantly.
  • Fact and Simulation of Dust Aerosol Transported to Stratosphere during a Strong Dust Storm in South Xinjiang
  • ZHANG Jie;TIAN Wenshou;LONG Xiao;TIAN Hongying;HUANG Qian;XU Pingping;YANG Qin;ZHANG Jiankai
  • 2015 Vol. 34 (4): 991-1004.  DOI:10.7522/j.issn.1000-0534.2014.00103
  • Abstract ( ) PDF (24069KB) ( )
  • Using NCEP reanalysis data and satellite observations, together with a mesoscale chemical transport model(WRF-Chem), a dust event occurred in the Taklimakan desert, north of the Qinghai-Xizang Plateau on April 17, 2007 is analyzed in an attempt to understand the characteristics and mechanisms of dust aerosol transport from the surface to the upper troposphere and the lower stratosphere over Qinghai-Xizang Plateau and its vicinity. Differences in the transport of particles with different sizes are also discussed. The results indicate that: Vertical transport of dust aerosols is closely related to background horizontal winds. In the absence of the cloud microphysical processes, when a deep convergence zone of northerly and southerly winds forms over Qinghai-Xizang Plateau, the vertical motions resulted from the convergence could transport dust aerosols, originated from the Taklimakan desert, to the lower stratosphere with an evident inclined transport pathway. The result implies that the position of the dust reached the lower stratosphere may not collocate with the surface dust source. In addition, dust particles with different sizes present different transfer characteristics. Small dust particles can be transported to the stratosphere relative easily by upward motions, while particles with size larger than 8.0 μm could not be transported to the lower stratosphere due to strong deposition process. The results from a sensitivity experiment with decreased orography height show that the upward and southward transport of dust aerosols is depressed when orography height is decreased.
  • Research of Retrieving Gamma parameters in Precipitation Cloud from Data Obtained of Vertical Radar
  • RUAN Zheng;LIU Chuyi;MA Jianli;JIN Long
  • 2015 Vol. 34 (4): 1019-1028.  DOI:10.7522/j.issn.1000-0534.2014.00037
  • Abstract ( ) PDF (4691KB) ( )
  • The data obtained from vertical radar can give better understanding of the microphysical processes inside precipitation cloud. A direct method of precipitation echo spectrum parameters estimate raindrop parameters is presented. Assumed the raindrop distribution is Gamma distribution, via radar meteorological equation, the relationship of raindrop terminal velocity and the diameter, exported the relationship of radar precipitation echo spectrum parameters and raindrop parameters. Using implicit functions explicit and series expansions to solve the equation, obtained approximate solution of the precipitation echo spectrum parameters estimate the raindrop parameters. Using forward method to establish testing database, verify the accuracy of approximate solution intercept parameter mean average relative error is 0.83%, slope parameter mean average relative error is 3.04%, and shape parameter mean average relative error is 13.60%. Test results show that the estimation method is feasible. Radar data of a precipitation event in Tengchong, Yunnan Province on 22-23 July 2012 is used to estimate the raindrop size parameters, and compared with terrestrial laser spectrometer obtained average diameter of the results, the results relatively consistency. This method of retrieving Gamma parameters is suit for straitiform precipitation cloud.
  • Characteristics of Albedo over Different Underlying Surface in the Semi-Arid Area
  • ZHANG Chi;FAN Guangzhou;MA Zhuguo;CHENG Bingyan;ZHAO Tianbao;FENG Jinming;WANG Hesong
  • 2015 Vol. 34 (4): 1029-1040.  DOI:10.7522/j.issn.1000-0534.2014.00071
  • Abstract ( ) PDF (4052KB) ( )
  • Based on radiation-flux, regular meteorological data and simultaneously remote sensed MODIS EVI data, obtained from various underlying land-surface of nine Chinese semi-arid area stations from July to September in 2008 and 2009, the seasonal and diurnal mean albedo, the fit regression with precipitation and the one-week continuous variations were characterized. The mutual effects among albedo, solar radiation and land-surface temperature in different weather conditions, including rain and snow, were deeply delved. The seasonal mean albedo over 4 types of underlying land-surface show that the magnitude are decreased as following: desert grassland > plateau grassland > recessive grassland > farmland, re-supporting the previous reports. The fit regression between the albedo and the precipitation on the plateau grassland, desert grassland and farmland are all significant (P-value < 0.05), but the recessive grassland is not available. The night rain scarcely effect the 'U' style distribution of the next day's diurnal albedo because the soil water cycling from latent heat or evaporation system attributed to the sensible heat on the desert grassland surface. While on the plateau grassland without snow cover, the albedo is mainly decided by the plant coverage per unit area and leaves property of plateau plant. The proper rainfall, lower shallow soil temperature, land-surface air temperature and lower solar income radiation can make the albedo bigger on the snow covered grassland. The new snow and frozen soil might be the crisis for the albedo of highland grassland. For the recessive grassland, the diurnal '√' style distribution in a marked rainfall procedure will be more obvious, if mean albedo from 09:00(Beijing Time, hereafter the same) 11:00 is much bigger due to more cloud scattering and the slowly increased albedo from 15:00-17:00 mainly due to the fact that raising force of the lower solar motive angle is bigger than the decreasing effect of the increasing the shallow soil water per column. In a diurnal 'U' style distribution of albedo on the farmland planted with corn, the mutual function between the solar motive angle and plant coverage per unit is conducive to the sudden increase of the mean albedo during 15:00-17:00 in the rain day, and the shallow soil water per column hardly contribute to the raised albedo at that time.
  • Evaluation and Improvement on Palmer Index of Tarim River Basin
  • LI Hongjun;JIANG Zhihong;BAI Yungang
  • 2015 Vol. 34 (4): 1057-1064.  DOI:10.7522/j.issn.1000-0534.2013.00201
  • Abstract ( ) PDF (3842KB) ( )
  • The Palmer index of Tarim River Basin was improved by using meteorological, hydrological and soil data, and the abilities of improved Palmer index and original Palmer index monitoring drought/wetness were compared and analyzed. The results are as following: the values and grads of improved Palmer index are closed to NDVI index than that of original Palmer index in season and year, the correlations between year, summer and autumn improved Palmer index and NDVI index are positive and higher, while the correlations of improved and original Palmer in autumn and winter are negative, all the correlations of improved Palmer index are higher than the correlations of original Palmer index in year and season. These show that the abilities of improved Palmer index monitoring drought/wetness are better than that of original Palmer index, and the abilities are good in year, summer and autumn, while it is weak in spring and winter. The correlations of improved Palmer index are higher than the correlations of original Palmer index in most basin area in year and season. This show that the improved Palmer index can reflect the spatial variation of drought/wetness in Tarim River Basin better. The correlations and degree of coincidence of inter-annual variation between improved Palmer index and NDVI index are better than that of original Palmer index in year and seasons, by comparing the actual drought situation, the correct year total of improved PDSI monitoring drought is more than that of original PDSI, the miss year total, vacancy year total and correctness of improved PDSI monitoring drought is better than that of original PDSI, so the improved Palmer index can monitor the drought/wetness in Tarim River Basin better.
  • Study on Whether a Tornado Occurred of ‘7·21’ Rainstorm in Beijing
  • ZHANG Linna;GUO Rui;HE Na;HE Yun;WU Jiankun
  • 2015 Vol. 34 (4): 1074-1083.  DOI:10.7522/j.issn.1000-0534.2014.00025
  • Abstract ( ) PDF (9464KB) ( )
  • ‘7·21’ rainstorm has been the new record of precipitation process in Beijing. Before the rainstorm, Tongzhou district in Beijing's eastern plains suffered strong wind attack. Because of not witnessed, whether it is caused by a tornado or not has been the focus of debating. After studying synoptic environment and radar echo data, it is proved that it is a tornado caused the gale; then using VDRAS data analyzed the dynamic structure of supercell storm. Study showed, the synoptic situation, vertical structure on temperature, humidity and wind are very conducive to the occurrence and development of tornadoes. BWER in reflectivity echo and mesocyclone in velocity echo showed it's a supercell storm; the convergence in 300 m and TVS further confirmed it's a tornado process. At last using the VDRAS inversion wind field showed the dynamic characteristics of the supercell storm: Low level in right rear the storm movement direction is easterly inflow layer, in start stage, easterly inflow layer is in higher, then the easterly wind weakened with height reduced. It forms a stable wind shear with high level enhanced westerly wind of outflow layer; in the mature stage, the storm has strong easterly inflow in low-level, and westerly outflow in high-level. At the core of supercell storm there is strong upward movement, so the supercell storm itself has forming a complete vertical circulation. The supercell storm is weakened when the environmental vertical wind shear is weakened and vertical circulation collapse.
  • Mechanism of Formation and Maintenance for a Torrential Rain on Strong Meiyu Front
  • ZHENG Jing;SUN Suqin;XU Aihua;WU Jing
  • 2015 Vol. 34 (4): 1084-1094.  DOI:10.7522/j.issn.1000-0534.2014.00019
  • Abstract ( ) PDF (8115KB) ( )
  • By using conventional meteorological observation data, TBB data, NCEP reanalysis data, a brief rainstorm happened on 14 June, 2011 in northern Jiangxi was analyzed. The results showed that: (1) Torrential rain happens with the interaction of South Asia High, subtropical high, west trough, monsoon, frontal cyclone and its meso-scale system. The stronger divergence in front of west trough on higher-levels is different from typical MeiYu. (2) Some general structural characteristics of Meiyu fronts are confirmed, such as the strong contrast of θse, the positive velocity, the wind and moisture convergence over the lower troposphere within the Meiyu front zone, etc. Especially, it is revealed that Meiyu front is highly baroclinic during the period. Besides, there are strong contrast of temper and wind shear within the front zone. (3) There exists convective instability in typical Meiyu, while symmetry instability in the event because of interactions between boundary convergence, baroclinic front zone and tropospheric jet, which make brief rain maintains.(4) More effective dynamic conditions, more stronger frontal zone and its frontogenesis process are close to the occurring of rainstorm than typical Meiyu. The strong ascending motion, strong divergence in higher-levels, strong convergence in lower-levels coupled with the development of meso-scale system, positive vorticity develops upward along the frontal zone of θse, which contributes much to the maintenance of heavy rain. (5) There is favorable vapour transfering mechanism by strong high-low level jets. The short distance between high-low level jets is effect to the coupling of high-low level jets.
  • Analysis on Evapotranspiration of Maize Field Measured by Lysimeters in Huailai
  • YANG Guangchao;ZHU Zhongli;TAN Lei;LIU Shaomin;XU Ziwei;BAI Junhua;XIAO Qing
  • 2015 Vol. 34 (4): 1095-1106.  DOI:10.7522/j.issn.1000-0534.2014.00114
  • Abstract ( ) PDF (4115KB) ( )
  • Based on the measurements of lysimeter, eddy covariance(EC) and automatic weather station(AWS) in Huailai Remote Sensing Experiment Station in 2012 and 2013, the daily and seasonal variation of soil evaporation and maize field evapotranspiration have been analyzed. The relationship between field evapotranspiration and meteorological factors(net radiation, air temperature, air humidity, and wind speed), soil moisture has been studied through multiple regression analysis method. Comparison has been made between the evapotranspiration measured by lysimeter and EC. The result shows that the daily variation curves of soil evaporation were quite consistent with maize field evapotranspiration, while seasonal differences were obvious. In the region of Huailai, net radiation and soil moisture obviously correlated with daily evapotranspiration, while other factors did not obviously correlated. Lysimeter's representativeness was significantly affected by the growth of the crops within it. The correlativity between evapotranspiration measured by EC and that by lysimeter is very good. The value of lysimeter is 10.5% higher than that of EC. As heat can not be exchanged between the soil in lysimeter and the soil outside, the average temperature of the soil in the lysimeter is 9.5% higher than that of the field outside. As a result, the evapotranspiration of lysimeter is relatively larger.
  • Numerical Forecasting Study of a Rainstorm at Liaoning by Assimilating Radar Data of Two Kinds of Background Fields
  • LI Deqin;DUAN Yunxia;ZHOU Xiaoshan;CUI Jin;YANG Yang;QIU Xiaobin;HAN Fangqiang
  • 2015 Vol. 34 (4): 1107-1118.  DOI:10.7522/j.issn.1000-0534.2014.00115
  • Abstract ( ) PDF (8839KB) ( )
  • To understand the improvements of two types of background filed used to weather forecasting assimilate radar observation, WRF model and ADAS are used to forecast the rainstorm that occurred at Jinzhou and Fushun of Liaoning during 15-17 August 2013, and two types of background filed include T639 and NCEP. The Result shows: (1) WRF fails to forecast the rainstorm in Jinzhou area. After assimilating radar observation with ADAS, it has been great improved in forecasting the rainstorm at the area of Jinzhou with both background fields. There is little improvement of forecast rainfall at Fushun after assimilation within 12~24 hours, and the performance of T639 is better than NCEP as background fields. (2) The initial filed of specific humidity is improved greatly after assimilating radar observation, and distinctly at 700 and 850 hPa. Meanwhile, the water substances in initial field are updated by assimilation, and the position have good correspondence with the area of rainstorm. (3) A strong and deep moist area is forecasted at the rainfall region in both assimilation tests. A system of strong warm wet wind jet stream from southwest at low level and cold dry at high level cooperation with the high moist region is the main reason leads to the occurrence of prolonged heavy precipitation ultimately, and a wind convergence in front of the moist region and a strong sinking inflow in the back of the rainfall region also forecasted with two background fields.
  • Circulation Pattern for Summer Precipitation in Northeast China and Application of Dynamical Climate Model Information
  • DING Ting;CHEN Lijuan
  • 2015 Vol. 34 (4): 1119-1130.  DOI:10.7522/j.issn.1000-0534.2014.00101
  • Abstract ( ) PDF (6775KB) ( )
  • Based on 91 station monthly data, NCEP/NCAR Reanalysis data and monthly dynamic extended range forecast 2.0 (BCC_DERF2.0) products from National Climate Center for 1991-2010, the circulation patterns for summer precipitation in Northeast China in each month are analyzed, the prediction skills of precipitation and main circulation systems by BCC_DERF2.0 are tested, and the precipitation prediction regression models are established. Precipitation in June is mainly influenced by Northeast cold vortex and Okhotsk blocking high, while in July mainly by western Pacific subtropical high, and in August by western Pacific subtropical high and Northeast cold vortex. On the analysis of model validation, BCC_DERF2.0 outputs are found to provide skillful predictions for precipitation in a few sites in Northeast China, and can predict the southerly wind in June, western Pacific subtropical high in July and August and Northeast cold vortex in August well. On the basis of validation for DERF2.0 model products, high-skilled prediction information of key circulation regions for precipitation anomalies in Northeast China is selected, and linear regression models are established. The cross-validation for precipitation regression model for August shows good prediction skill, and the correlation between observation and hindcasts is significant. By comparison, the raw BCC_DERF2.0 precipitation outputs for 1991-2010 in each month show better prediction skills than the operational prediction from National Climate Center in the same period, while the prediction skills for cross-validation of the prediction regression models are better than the raw BCC_DERF2.0 precipitation outputs in the corresponding month. The precipitation prediction by high-skilled circulation information from BCC_DERF2.0 10 days ahead of forecast time can improve the prediction ability for summer monthly precipitation in Northeast China.
  • Diagnostic Analysis of a Historical Extreme Snow Process in Shandong
  • ZHANG Qin;DING Zhiying;YANG Chengfang;WANG Shijie;HAN Xiao
  • 2015 Vol. 34 (4): 1131-1138.  DOI:10.7522/j.issn.1000-0534.2014.00009
  • Abstract ( ) PDF (9361KB) ( )
  • Based on conventional surface data, reanalysis data from NCEP and TBB data, the comprehensive analysis of snowstorm occurred in Shandong province from 19 to 20 April 2013 was done. The results show as following. It is the main synoptic background to generate the snowstorm that 500 hPa upper trough, 700 hPa southwest low level jet and the shear line and 850 hPa low-level northeaster made the backflow snow. During the snowshorm, snowstorm area physical quantity in the space above the vertical section shows: A relative humidity of 90% or more under high humidity area downloaded and warm moist air along the southern low-level cold climbed, and after reach a certain height, the water vapor condenses snow, and snowstorm fell the center of the area was not located in the strong upward movement, but located in the north side of the center value biggest, between 28°N~40°N has a high energy frontal zone, and along with the increase of latitude leaning to high altitude. Near the ground layer is an obvious convergence field, and distribution of TBB reaction during the snowstorm had meso-microscale system coordination, TBB maximum in between -45~-40℃. Terrain in the extreme blizzard events over a rapid decline in the temperature played a very important role.
  • Climatological Characteristics of Different Type Heavy Snowfall Weather in Jilin during 1961-2010
  • WANG Xiaoming;SUN Yan;YUN Tian;SUN Hongyan;JI Lingling;NI Hui
  • 2015 Vol. 34 (4): 1139-1148.  DOI:10.7522/j.issn.1000-0534.2014.00008
  • Abstract ( ) PDF (3511KB) ( )
  • The spatial and temporal distribution characteristics and topographic effect of different types heavy snowfall are analyzed with the daily precipitation data in Jilin in winter (October to March in next year) during 1961-2010. The influence system and it's vertical structure of various types heavy snowfall are analyzed in the same time. The results show that (1) There is high interannual variability and obvious stage change characteristics in temporal distribution of heavy snowfall that mainly occurred in late autumn and early winter(October and November) or between winter and spring(March), and those interannual variability and trend of decadal variation was consistent with the trend of temperature variation in winter. (2) Heavy snowfall I most in March which is regional or large range snow, but heavy snowfall II most in October. (3) There is large difference of spatial distribution and obvious regional features of heavy snowfall which occurred in the windward slope of Changbai Mountain and mountain area was significantly more than in the leeward slope of Daxing'anling Mountains and plain areas by the interactioninteraction of weather systems and the Changbai Mountains. (4) The high altitude effects system of heavy snowfall was the most in upper trough, followed by cold vortex, and the least in the shear. (5) Affected by upper trough, surface system of local heavy snowfall is more in cyclone inverted trough, but regional and widespread heavy snowfall is more in Huabei and Jianghuai cyclone. Affected by the high altitude cold vortex, surface system of local is first at Mongolia cyclone, regional and large-scale heavy snowfall is most in cyclone inverted trough. (6) In terms of the ground system, the heavy snowfall I is most in Huabei cyclone, but the heavy snowfall II is most in Mongolia cyclone that are regional and widespread heavy snowfall.
  • Research of Reconstruction and Characteristics of Hazes in Anhui
  • DENG Xueliang;SHI Chun'e;YAO Chen;WU Biwen;YANG Yuanjian;ZHANG Hongqun
  • 2015 Vol. 34 (4): 1158-1166.  DOI:10.7522/j.issn.1000-0534.2014.00007
  • Abstract ( ) PDF (3509KB) ( )
  • Based on the data provided by 80 surface observation stations from 1970 to 2009, haze days were reconstructed with the objective distinction method for recent forty years in Anhui and the climatic features of haze were systematically analyzed. Results show that the reconstructed haze days were well consistent with the observed and reconstructed values were often higher than observation, so the reconstructed haze days can compensate the lack of haze observations in some stations. Meanwhile, haze days expressed a notable spatial-temporal distribution feature. In annual variation, the time at the begin of 1980s is a cut-off point and after that time haze days exploded. Then the number and density of haze days both increased continuously with the development of Anhui economy. In spatial, haze days were more in eastern region than them in western region and haze regions gradually expanded to the west and the north. As a result, two high hazes centers were formed in the central region of Anhui and the eastern region of Yangtze River. In season, haze occurs mainly in fall and winter rather than in spring and summer. In particular, the medium degree and high degree hazes are all in fall and winter.

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