Plateau Meteorology

Current Issue

28 October 2011, Volume 30 Issue 5   
  • Seasonal Evolution Features of the Southerly Windon the Southeast Side of Tibetan Plateau
  • QI Li;HE Jin-hai
  • 2011 Vol. 30 (5): 1139-1147. 
  • Abstract ( ) PDF (1522KB) ( )
  • Observations indicate that there is a special region on the southeast side of Tibetan Plateau, over which the meridional wind is always the southerly during the whole year both in the climatology or the EOF domain mode. This is different from the typical East Asia monsoon climate. However, the southerly has significant seasonal variation. As early as in February it has seasonalenhancement in southerly phase, which demonstrates this special region is sensitive to the East Asia general circulation transition from winter to summer. Moreover, in later March to early April it reaches its peak, forming double-peak structure. These two time points are just when the East Asian subtropical summer monsoon onsets and becomes matures. Consequently, the southerly is closelyrelated with the East Asian subtropical summer monsoon. Furthermore, in the strong southerly year, intense southwesterly wind prevails in eastern China in summer (JJA), which brings the rain belt to much northward, the west Pacific subtropical high is much stronger and locates more westward than usual. However, at the same time the crossing-equator flow is weak and the trough over Bay of Bengal is of weakness. These indicate that the tropical summer monsoon is weaker than normal. That is, in strong southerly year the East Asian subtropical summer monsoon is more intense while the tropical summer monsoon is weaker than normal. Therefore, the southerly wind over the southeast Tibetan Plateau is special and important, where is the key region for the weather and climate in eastern China.
  • Variations of South Asia High and West Pacific SubtropicalHigh and their Relationships with Precipitation
  • CHEN Yong-ren-;LI Yue-qing;QI Dong-mei
  • 2011 Vol. 30 (5): 1148-1157. 
  • Abstract ( ) PDF (1361KB) ( )
  • Using the precipitation data of 160 climatic stations in China and NCEP/NCAR reanalysis data, the characteristics on South Asia High (SAH) and the Wes Pacific Subtropical High (WPSH) and their effects on precipitation in mid-summer were analyzed. The results showed that the index of eastward extension of SAH had time scales of 3~6 a periods, 10~15 a and approximate 20 a period. The index of westward extension of WPSH had time scales of 3~6 a and approximate 20 a periods. Also the relations between the index of eastward extension of SAH and the index of westward extension of WPSH were more significant from 1980 to 1990. Meanwhile, the results of spectrum analysis showed that both relationships were very significant in 10~15 a, 3 a, 6 a periods, and there was significant correlative relation between the precipitation of Yangtze River and SAH on 10~15 a time scales, but not significant relation between Yangtze River and WPSH. To some extent, the precipitation variation of Yangtze River region had close relationship with SAH in 10~15 a periods, therefore, the index of eastward extension of SAH can be regard to forecast precipitation interdecadal variation of Yangtze River in mid-summer as a conference signal.
  • Diagnostic Analysis and Numerical Simulation of a TorrentialRainstorm Process Caused Southwestern Low Vortex
  • 2011 Vol. 30 (5): 1158-1169. 
  • Abstract ( ) PDF (2240KB) ( )
  • A case of torrential rainstorm process caused by a southwest vortex (SWV) is diagnosed using the observation data, FY-2C satellite image, and NCEP/NCAR reanalysis data. The result shows that the main influencing systems are South Asia High, lee trough, and shear line from the tropopause to near surface in vertical direction. The tropical storm ‘0907’(Goni) is another key factor in this case. The torrential rainstorm is directly caused by three mesoscale convective cloud clusters continuously, which occurred asymmetrically in close SWV. The WRF_ARW is used to simulate, the result shows that it prompts the SWV strengthened that strong divergence exists in the vicinity of South Asian High ridge in the upper troposphere, vertical coupling of leeward vortex in the middle troposphere and the strong easterly dry and cold jet and the southward warm and wet jet interaction with each other in the Sichuan Basin in the lower troposphere. There exists a warm core near 300 hPa in developing SWV, this distribution pattern changes to cold in north and warm in south under 850 hPa in the lower troposphere, and the warm and cold air junction section appears northward slope with height increases. The upward motion of secondary circulation on the north and south sides of the low vortex center convergent near vortex center, which results in strong upward motion to enhance the SWV. With the South Asian High and high level jet stream moving to south, high level divergence weakens, causing SWV decay. As main westerly trough moving over the Hetao area, strong cold air behind it rapidly progression southward along the east side of the Plateau, that is a large number of cold air enter into the Sichuan basin to cause SWV moving out Sichuan basin, and it disappears eventually.
  • Spatial-Temporal Variations of Drought and Flood Intensitiesin Sichuan Region in the Last 50 Years
  • 2011 Vol. 30 (5): 1170-1179. 
  • Abstract ( ) PDF (1136KB) ( )
  • The frequencies of drought and flood events in Sichuan were analyzed based on the daily precipitation data at 123 stations in summer from 1961 to 2007 and the NCEP/NCAR monthly reanalysis data, taking Z index method as classify thedrought and flood grades. In addition, the EOF, REOF,linear trend, running t test, and wavelet analysis methods were used to analyzethe temporal and spatial change trendsof drought andflood events in Sichuan. The analyzed results are as follows: Drought andflood events in Sichuan region in summer can be identified into four regions, namely, east Sichuan basin, west Sichuan basin, southwest Sichuan mountain region,and western Sichuan Plateau. As to the temporal change trend, it changes from drier to weter in east Sichuan basin, southwest Sichuan mountain region and western Sichuan Plateau, whereas the trend in west Sichuan basin is fromweter to drier. In the four regions, the interannual and interdecadal changes in the drought and flood eventsare obvious.The fluctuating of west Pacific subtropical high and South Asia high and the intensity of plateau monsoonhave significant impactson droughtandflood events in east Sichuan basin, west Sichuan basin,and western Sichuan Plateau.
  • Further Analyses of Obvious Moistening in Central Xinjiangin Recent 20 Years
  • LIU Yuan-pu;BAI Huzhi;QIAN Zheng-an;;YANG Xia;ZHANG Liang
  • 2011 Vol. 30 (5): 1195-1203. 
  • Abstract ( ) PDF (1108KB) ( )
  • The obvious moistening fact in Central Xinjiang(CX) in recent 20 years was further analyzed utilizingthe observed precipitation data at 15 stations in CX in 1951-2008 and partly hydro-meteorological data and the wavelet technique. The main conclusions are as follows: (1) Both the meteorological and hydrological data show that there exist three dry/wet episodes: i.e., gait wet one in 1946-1960, evidentdry one in 1961-1986, and striking wet one in 1987-2007, in CX in the past 60 years. Each lasted 20 years or so, the rainfall in the last 20 years increase by 10%～20% than usual. (2) The moistening in recent 20 year is mainly occurringin summer. (3) The short period (quasi-three years) change for the precipitation in CX in past 60 years is quite clear; and the midrange-period change about 20 years is also clear especially in summer. (4) Judgingfrom above moistening area is not on the whole Northwest China scale, the area precipitation had already decreased in the past three years, and also the precipitation climate projection in drought area has much more uncertain. It is possibly that above moistening is just the reflection about 20 year interdecaded change of Xinjiang precipitation.
  • Analysis on Three-Dimensional Motion of an IntenseAnomaly Ocean-Effect Snowstorm in Bohai
  • 2011 Vol. 30 (5): 1213-1223. 
  • Abstract ( ) PDF (1615KB) ( )
  • Based on the simulated data of RAMS4.4 model, 3-D trajectory analysis of air parcel and diagnosis, three-dimensional structure and development mechanism of an intense anomaly example of Bohai ocean-effect snowstorm which occurredin Shandong peninsula and Bohai on 4~16 December 2008 are analyzed. The results shows that the strong extremely cold air leads large difference between the sea and atmosphere. From 3-D trajectory analysis, the air parcel in Bohai low level goes upward, but the middle and upper air parcels remain the original direction. Dynamical force of weather scale system and ocean-effect play the common action on the snowstorm. Upper trough deepening has two actions. One, compensatoryassending motion caused by positive vorticity advection is favorable tomore snowfall. Another, it can lead cold air to outbreak southward. Then more instable layer will bring more ocean-effect snowstorm. In result, the strongest snowfall occurredduring the upper trough influence. So it is the importance tothis phenomenon in the forecast operation. In the low troposphere, shear line between the northwest and northeast wind decide the intensity and position of snowfall. What′s more, the weak vertical wind direction is helpful to form strong snowfall in local area.Key words: Ocean-effect snowstorm in Bohai; Three-dimensional motion; Upper trough; Shear line
  • Large Scale Circulation Characteristics and Diagnotic Analysesof Two Spring Rainstorm in Dalian
  • 2011 Vol. 30 (5): 1243-1254. 
  • Abstract ( ) PDF (1817KB) ( )
  • Using NCEP/NCAR reanalysis data, conventional observation data, and hourly rainfall observation data from nearly 100 automatic weather stations (AWS) in Dalian, the characteristics of the large scale circulation associated with the two heavy rainstorms processes in Dalian during 3～5 March 2007 and 19～21 April 2009 are diagnostically analyzed. The results show that: (1) Increasing of temperature and moisture in the lower troposphere, and intrusion of cold air from the mid-latitude region are the important conditions to result in the two torrential rain occurrences in spring; (2) Rainfall intensity is enhanced after the cyclone genesis which located in front of a long-wave trough, and tends to move close to the baroclinic frontal zone in the mid-latitude region, and is opposite when no long wave trough is nearby and the mid-latitude baroclinic frontal zone is far distant away; (3) It is favorable for occurring of heavy precipitation in Dalian area this has the long time link this area with the moisture transport channel from lower level jets; (4) Downward propagation of westerly momentum in the southern branch of the upper level jets is favorable for genesis and development of cyclone over Yangtze-Huaihe River valleys. During its progressing northward, the jets move close to the upper level jets in the mid-latitude region, leading to enhanced divergent flow in the upper layer in the northeast of Dalian. Such flow pattern is favorable for re-intensification and long time substation of the cyclone; (5) Propagation of strong moist potential vorticity from upper to lower levels leads to intrusion of cold air into the periphery of the cyclone, and genesis of front. Forcing by frontal genesis enhances uplift of warm and moist flow. Downward propagation of strong moist potential vorticity is channeled with positive vorticity at the surface, thus the amplifies local perturbation of potential vorticity, and induces favorably cyclonic circulation in the frontal zone of lower layer. The cyclonic circulation will force the cyclone to develop and strengthen, and result in heavy precipitation occurrences. (6) Supplement of dynamic energy acquired from the ageostropic movement in the large scale circulation in middle and upper layers to the energy loss by frictional dissipation amplifies precipitation intensity. Therefore, during the genesis and northeastern movement of cyclone over Yangtze-Huaihe River valleys in spring, from extension of the moisture channel to Dalian area, relationship of cyclone with baroclinic frontal zone, and interaction between upper and lower level jets are identified the cyclone will develop and intensify or rapidly weaken, thus to forecast precipitation intensity indicatively. Different intensities of cold air result in different amplifications of temperature decrease. The rapidly decreasing of temperature will bring about precipitation form of multiple phase changes, which is easily induce extremely severe weather events which is directly linked to hazard. During the heavy precipitation in spring, attention might be focused not only on rainfall amount, but also on rapid changes of phases of water.
  • Diagnostic and Analysis of Consecutive Fog Processon Large-Scale in East China Region
  • 2011 Vol. 30 (5): 1255-1265. 
  • Abstract ( ) PDF (1718KB) ( )
  • Using the surface observation data, upper probe data and NCEP/NCAR reanalysis data, the characteristic， property and circulation of consecutive fog process on large-scale in East China from 30 January to 10 February 2009 are analyzed， and the water vapor and dynamic conditions are diagnosed， then the difference between the processes of fog and haze in middle-east China in the first ten days of January 2008 is briefly compared. The progress mainly belongs to radiation fog， and the fog is the most serious during 05:00～08:00 in the morning. The whole process is divided three stages， while it is the more serious on January 31， February 1， 5， 10. There is zonal-type circulation in middle-high latitudes， and westerly flow is relative flat and straight， so it is difficult for cold air moving southward to middle-east China. East China is basically controlled by the equal high pressure field， so the pressure gradient force and near-surface wind are very small， and it is beneficial to the formation and maintenance of fog. Interpretation of the physical quantity distribution is very good for the occurrence and maintenance conditions of fog. 1～3 m·s-1 surface wind， divergence， negative vorticity， weak vertical movement in lower level are the dynamical conditions of fog formation. The configurations of small relative humidity， little difference of dew point to air temperature on lower level， and relative dry in middle troposphere constitutes water vapor condition of the fog. Inversion layer on lower level and stratified stable atmospheric stratification stability compose of stable condition. The process is significant different to the fog and haze in middle-east China in the first ten days of January 2008.
  • Evaluative Characteristic of Extreme Minimum Temperatureof Northwest China in Recent 49 Years
  • 2011 Vol. 30 (5): 1266-1273. 
  • Abstract ( ) PDF (898KB) ( )
  • The low temperature events were analyzed based on the NCEP/NCAR dataand the daily minimum temperature observation data from 135 meteorological stations in the Northwest China during 1961-2009, using the methods of linear regression analysis, Mann-Kendall, running T-test, wavelet analysis, power spectrum and composite analysis. The results show that: (1) The spatial distribution of the extreme minimum temperature in Northwest China presents the distributed tendencies of two high and low interactions. The areas with minimum temperature value are located in northern Xinjiang and Qinghai Plateau. And the threshold value of extreme minimum temperature in these places are below -20 ℃; (2) The frequency of annual extreme minimum temperature has obviously reducing at a rate of 3.7 d·(10 a)-1, majority places remarkably reduced at a rate of 3~5 d·(10 a)-1. There isan abrupt change in 1985, the minimum temperature frequency has the remarkable 3 year periods. (3) The values of extreme minimum temperature are between -49.8to -8.6 ℃, the maximum value appears in Fuyun of Xinjiang. There is a same geographic distribution between minimum temperature intensity and extreme minimum temperature. The intenser the extreme minimum temperature is, the longer the day number of duration is. The phase of frequently occurring of minimum temperature is also the phase of the strongest minimum temperature. The global warming causes the extreme minimum temperature events reducing and intensity weakening. (4) From the circulation characteristic quantity analysis, the extreme minimum temperature in Xinjiang related withzonal circulation, polar vortexcharacteristic quantity and Atlantic-Europe circulation, but the extreme minimum temperature in other places related with subtropical highandQinghai-Xizang Plateau height field. The composited analysis indicated that the polar vorticity center is located the Eastern Hemisphere. The Arctic region is the positive anomalous. The middle latitude is belt-shaped negative anomaly. Xinjiang high ridge is located to the west. The East Asian trough is deep. The northwest arid area is in front of the Xinjiang high ridge. The northwest air current is easy to appear the minimum temperature weather. The positions of Ural mountain minimum trough, Xinjiang high ridge and East Asia big trough from 500 hPa to high-level are stable. The atmosphere is the quasi-barotropic state, Northwest China region is controlled by the Xinjiang high pressure ridge, which is unfavourable to the wide range and duration minimum temperature weather.
  • Analysis on Mean Abrupt Change of Precipitation in HexiCorridor Region in Recent 50 Years
  • 2011 Vol. 30 (5): 1286-1293. 
  • Abstract ( ) PDF (979KB) ( )
  • Based on the precipitation data at 16 meteorological stations in Hexi corridor from 1960 to 2009, the multi-scale mean abrupt changes of annual and seasonal precipitation at each typical station in recent 50 years had been analyzed based on the Mexican Hat wavelet technique. It was showed that mean abrupt changes of annual precipitation in Hexi corridor were detected in 1968, 1973, and around 1982, 1991 and 2005. Abrupt changes of precipitation from less to more were detected in 1968 and 1991 in the western corridor(Dunhuang). Abrupt changes of precipitation from more to less occurred around 1982 to 1983 and in 2007. The abrupt change in 1968 was the most significant one. In the eastern Corridor(Wuwei), there were abrupt changes from more to less in 1973 and from less to more around 1989-1992, respectively. In the middle Corridor (Zhangye), there was abrupt changes around 2004-2005 form less to more. And in the Mazhongshan region(Mazhongshan), there were abrupt changes from less to more in 1968, and from more to less in 1982. Summer precipitation at each station accounted for more than 50% of annual precipitation. And among four seasons， the abrupt changes were the most significant ones, which also consistent well with annual precipitation.
  • Studies of Land-Atmosphere Interaction Parameters inTaklimakan Desert Hinterland
  • 2011 Vol. 30 (5): 1294-1299. 
  • Abstract ( ) PDF (697KB) ( )
  • Continuously observational data collected in Taklimakan Desert hinterland (38°58′N,83°39′E) from July 21, 2008 to July 20, 2009, have been used to investigate some key parameters of land-atmosphere interaction, including surface albedo, soil thermal parameters and their relationships with soil temperature, and aerodynamic roughness length. The obtained results are as follows: (1) The diurnal variation of surface albedo appears as a ‘U’ shape on sunny day. It decreases with the increase of solar elevation angle, and it tends to be a constant when solar elevation angle is larger than 10, thus, the daily average surface albedo was computed using the data when solar elevation angle is large than 10. Mean daily surface albedo is found to has obvious season variation, lower in winter but higher in summer, average annual surface albedo is 0.270±0.003. (2) The variations of soil heat capacity and thermal conductivity are becominglower and more stable during the late autumn to the early spring in next year, and reach the lowest in middle of January. They are lower in winter and higher in summer, also has clear season variations. Average soil heat capacity, soil thermal conductivity and soil thermal diffusion are 1.559(±0.140)×106 J·m-3·K-1， 0.234(±0.021)W·m-1·K-1and 1.504(±0.110)×10-7m2·s-1, respectively. (3) Surface emissivity, estimated by a physically based, semi-empirical method, is 0.91. (4) Aerodynamic roughness length in Taklimakan Desert hinterland is far less than other domestic deserts, range is (2.7~8.0)×10-5 m, less than 2 orders of magnitude of Dunhuang and Heihe experimental values, but increased to range (21.04~91.32)×10-5min winter.
  • Radiative Force and Temperature Response of DustAerosol over East Asia in Recent Decade
  • 2011 Vol. 30 (5): 1300-1307. 
  • Abstract ( ) PDF (931KB) ( )
  • A regional climate model RegCM3 coupled with an on-line dust module is used to simulate the radiative force and temperature response of dust aerosol over East Asia in the recent decade from 2000 to 2009. The simulated results show that the geographicaland seasonal differences of dust aerosol distribution over East Asia are obvious. There exist two extremes of dust aerosol with column burden larger than 1 000 mg·m-2, one is in the Takelamagan desert of Xinjiang UigurAutonomous Region, China, and the other is in the Badain Jaran desert of Inner Mongolian Autonomous Region, China. The maximum value of column burden appears in spring, the secondary maximum in winterand the minimum in autumn.The radiative force of dust aerosol has similar distribution characteristic with column burden. The averaged radiative force over East Asia at the top of atmosphere is -1.72 W·m-2 in spring and -1.17 W·m-2 in autumn, and that at the surface is -4.34 W·m-2 in spring and -2.33 W·m-2 in autumn. The surface temperature is decreased by dust aerosol, and the averaged decreased extent over East Asia is 0\^154 ℃in spring and 0.085 ℃in autumn. There are different impacts of dust aerosol on air temperature at different heights. The air temperature is decreased by dust aerosol in lower troposphere, and the decreased extent is diminished with the height increasing. The air temperature turns to increase by dust aerosol at the heights of 300~400 hPa in spring, but it is more complicatedin autumn.
  • Cloud Structure, Precipitation Mechanism and Artificial EnhancementPrecipitation Condition for a Frontal Stratiform Cloud System
  • 2011 Vol. 30 (5): 1308-1323. 
  • Abstract ( ) PDF (1840KB) ( )
  • Using the observation data and numerical simulation result, the structure and its distribution and the precipitation mechanism of the ‘seeding-feeding’ cloud for a typical stratiform cloud system are studied, the artificial enhancement precipitation conditions are studied using the analysis of cloud structure and moisture transformation. The result shows that there is different vertical structures in the different parts of cloud system. The water content centers located in three levels: The upper level (nearly 300 hPa level) is consisted of ice and snow; the middle level is mixed layer with ice and water, located in 600~650 hPa; the lower level is composed by liquid water to be between 800~900 hPa levels. These levels are corresponding to heights of maximum water vapor condensation rate. In the three different parts of cloud system, there are three different cloud combinations. The multilayer structure is a main characteristic of the cloud system and ‘seeding-feeding’ cloud is the main precipitation mechanism. The analyses of moisture transformation show that the cloud water of 29% is transformed into the precipitation particles by the accretion process. Ice crystal of approximately 49% is converted snow and snow about 92% becomes graupel. graupel of 96% is melted into rainwater and accounts for 57 percent of total rain water. Mechanism of precipitation formation is different in the different parts of frontal cloud system. In the zone away from the front zone, the precipitation is produced mainly by the cold cloud process and the growth of ice particle is mainly by sublimation process. The precipitation is formed almost completely by ice particles melting. Comparing with the frontal zone, in the prefrontal zone， contribution of warm cloud process to rain water is larger and account for 60% of the rain water; and in the near front zone, the cold cloud process is the main in forming process of rainwater. the artificial enhancement precipitation conditions are analyzed based on the cloud structure and precipitation mechanism. The ‘seeding-feeding’ cloud structure, precipitation mechanism, super-cooled water content, ice crystal concentration and water vapor content in the warm zone of cloud and water vapor content of supper-saturation with respect to ice may be used to judge seeding conditions of artificial enhancement precipitation.
  • Precipitation Estimation of Mountain Weather Radar ImprovedUsing Ultra-Low Elevation
  • 2011 Vol. 30 (5): 1337-1345. 
  • Abstract ( ) PDF (1235KB) ( )
  • Based on 26 times radar data at ultra-low elevationduring the process of heavy rainstorm in Kunming in May 2004, the value of radar data at 0° elevationin quantitative precipitation estimation (QPE) was discussed using the radar data at 0° and 0.5° elevations. The results showedthat: The ability of detection precipitation at far from mountain weather radarwas weaker at 0.5° elevationthan that of 0° elevation. There was no ground clutter at 0° elevationin Kunming radar by comparing with radar data at 0° and 0.5° elevations. 0° elevation can improve the ability of detection precipitation at far from mountain weather radarfrom amount of precipitation and detection range. Precipitation range/amount at 0° elevationwas larger 9.96%(about 28.147 km2)/11.6% than that of 0.5° elevation. The precipitation process dominated by stable stratiformechoes about 25 dBz, which reflected inhomogeneous precipitation distribution in Yunnan from vertical and horizontal structures of precipitation. It was showed that ultra-low elevationin mountain weather radarcould improve the detection ability after eliminating ground clutter.
  • Research of Spatial Distribution Characteristic of AtmosphricAerosol in Jinan and Its Surrounding Regions
  • 2011 Vol. 30 (5): 1346-1355. 
  • Abstract ( ) PDF (1034KB) ( )
  • The spatial distribution of aerosol was analyzed by the measured data with PMS rented from Beijing weather modification in October 2009. The relations of aerosol distribution characteristics with inversion layerand relative humidity were discussed. The results show that there was significant difference in the vertical distribution of aerosol. The inversion layer and relative humidity have a great impact on the distribution of aerosol. Nearby the inversion layer and higher relative humidity, there was a accumulative area of aerosol concentration. The maximum value of aerosol concentration magnitude can reach 1×104 cm-3， and the maximum value of mean diameter is 0.38 μm. The aerosol spectrum often is multimodal because of inversion layer and relative humidity. The peak of aerosol concentration is consistent with inversion layer and maximum relative humidity, and the concentration of aerosol and mean diameter of aerosol have an inverse proportionrelation. The aerosol spectrums are quite similar, and most of them are unimodal, and the peak value is on the end of small particles, and the spectrum width reaches 2\^4 μm. There is a drastically reduce of aerosol concentration in the vicinity of 0.28 μm. The fitting analysis of number density spectrum about aerosol is done.
  • Numerical Simulation of Influence of Aerosols on DifferentCloud Precipitation Types in Beijing Area
  • 2011 Vol. 30 (5): 1356-1367. 
  • Abstract ( ) PDF (1467KB) ( )
  • Three types of rainfall (rainstorm, moderate rain and slight rain) in Beijing area are simulated using Weather Research and Forecast (WRF3.2) model coupled with Milbrandt-two-moment cloud microphysics scheme, under the continental and maritime aerosol concentration, to explore the influence of aerosols on cloud precipitation. The results indicate that the aerosol increase has various influences on the cloud precipitation: (1) Influencing the ground precipitation. With the increasing of aerosol concentration in Beijing area, 48 h total precipitation of the rainstorm and moderate rain are decreased 23% and 16.6%, and 24 h total precipitation of slight rain decreased 14%;(2) Influencing the surface precipitation distribution.The average precipitation of the rainstorm is increased in the most of parts of western Beijing and reduced over 20 mm in the most of parts of easternBeijing with the increasing of aerosol concentration. The average precipitation of the moderate rainfall decreases 0.1～5 mm in the most of parts of Beijing area. With the increasing of aerosol concentration, the precipitation in western Beijing increase in the slight rainfall process, but eastern, decrease. (3) Influencing the ground precipitation intensity. With the increasing of aerosol concentration the rainfall duration of the rainstorm is prolonged in the high aerosol concentration. An earlier precipitation termination of the moderate rain is found with the increasing of aerosol concentration;(4) Influencing the airbornehydrometeors. The increasing of aerosol concentration causes higher cloud water concentration and lower rain water during the rainstorm and moderate rainprocesses .
  • Study on Vertical Microphysical Structure of Cloud for aMulti-layer Cloud System
  • 2011 Vol. 30 (5): 1368-1375. 
  • Abstract ( ) PDF (982KB) ( )
  • Using the PMS flight detection data, radar echoes data and FY-2 satellite cloud image, a deep multi-layer cloud system without ground precipitation in June 2009 is analyzed. The cloud system is a Cs-As2-As1-Sc2-Sc1 structure with dry layer. The result shows that in the cloud system the warm layer is deep while the super-cooled layer is very thin. The liquid water distributes quite unevenly with height, showing several peak values. The liquid water content in the multi-layer cloud system is mainly determined by the number concentration of small cloud particle. There are a number of small cloud droplets, a few large cloud particles, a small quantity of precipitation particles and scarce ice nuclei. The vertical distribution of particle is very uneven. The lack of enough ice nuclei take as condensation nuclei in the multi-layer cloud system, while super-cooled water does not exist in the multi-layer cloud system, as well as the thick dry layer between Cs and As2 obstructs the falling of ice nuclei, the cold cloud process contributes little in the forming of precipitation particles. In the warm cloud process in the middle layer and the low layers, because As2 is weak, and so the large droplets in As1 are lack, precipitation particles form from cloud droplets mainly through tardy condensation growth, so that precipitation particles never fall through the base of As1. In Sc2 precipitation particles form from cloud droplets through condensation and collection growth. However, the precipitation particles in Sc2 are mainly small particles, and large particles are limited. The transforming speed and efficiency from cloud droplets to precipitation particles is slow. Precipitation particles could not pass the dry layer to impact Sc1. And Sc1 has not yielded particles larger than 300μm. Finally, the deep cloud system has not formed ground precipitation.
  • Study on Bright Band Detection Using Wind Profiler Radar
  • 2011 Vol. 30 (5): 1376-1383. 
  • Abstract ( ) PDF (1086KB) ( )
  • L-band wind profile is used in coherent accumulation technology to rise radar sounding sensitivity, vertical measurement precipitation cloud body is applied, which can obtain the entire spectrum information of cloud body return signal of high resolution. The wind profiler is used to continuously detect the bright band appeared in stratiform cloud precipitation process on May 14, 2009. The variation and evolution characteristics of return signal spectrum parameter (power, average Doppler velocity, speed spectral width) and the changes of power spectral density distribution with the height nearby the region of bright band were obtained. The ice and water transformation process is found near the bright band area, in the cloud the surface of snowflake, ice crystals start to melting near -1.3 ℃, the whole skeleton of snowflake, ice crystal begin breaking into the smaller scale liquid precipitation particles near 0.8 ℃, the ice crystal, snowflake melt to liquid precipitation particles completely 3.5 ℃. At the same time, the levels about 300 m thickness and around 0.8 ℃ can be observed the phenomenon that the echo intensity spectral range stretch suddenly, it reflected that the obvoius decreasing of local environment temperature caused by ice and water transformation of precipitation particle may lead to the few detail convection.
  • Analysis on Atmospheric Characteristic of Precipitationin Qilian Mountain
  • 2011 Vol. 30 (5): 1392-1398. 
  • Abstract ( ) PDF (924KB) ( )
  • Using the observated data of Qilian field experiment station and the introduction method of an objective reflection of upper atmospheric cloud and precipitation, the atmospheric characteristic of precipitation in the Qilian mountain is analyzed. The result shows that the cold cloud in upper level and warm cloud in lower level are to form main cloud systems of precipitation in the Qilian mountain, and the cold cloud in upper level depends on the weather system scale， but the warm cloud in lower level is formed by the terrain blocking and surface heating. In the different weather systems, the role of topography on precipitation is different. It is easy to form valley wind circulation to enhance precipitation under the influence of southwest air flow, and to form down valley wind circulation under the influence of the northwest and straight west air flow, the water vapor is transported from valley to mid- and upper-levels, but which is inhibited main leading air flow to form shallow precipitation cloud. The temperature above 0 ℃ is corresponding to the obvious wet and saturated zone near mountain top in summer, the cloud take the water cloud as main. In addition, CAPI can objectively reflect the upper-level cloud and position of precipitation occurrence and its basic characteristic, and its change trend with height is consistent to the change of surface precipitation with time.
  • Changes of Mean and Extreme Temperatures in Tianjinin Recent 100 Years
  • 2011 Vol. 30 (5): 1399-1405. 
  • Abstract ( ) PDF (653KB) ( )
  • Mean temperature, mean maximum and minimum temperature series in Tianjin were calculated using the observed data of daily maximum and minimum temperaturesduring 1910-2009, as well as the several extreme temperature series, including high and low temperature thresholds, the longest warm day and cold night durations, and frost days. Trends and abrupt changes were examined for these temperature series using the linear regression and Mann-Kendall test. It is indicated that the mean temperature in Tianjin significantly increased in the recent hundred years, and the increasing trends of minimum temperature in winter and spring are the most significant. The longest warm day tended to increase since the 1990s, though annual and summer high temperature thresholds significantly decreased in the recent hundred years. Meanwhile, the low temperature thresholds significantly increased through all seasons, and the increasing trends in winter is the most significant. In accordance, the day numbers of frost and the longest cold night days significantly decreased in winter and spring. From the abrupt changes in the recent hundred years, the temperature increasing since the late 1980s main is the rapid increases of minimum temperature and winter temperature. Comparing with the period of 1910-1959, the variances of mean temperature and numbers of the longest warm days/cold night days were smaller in the period of 1960-2009, which indicate moderate annual temperature variations and extremes.
  • Comparision of Three Drought Indices in Drought of Shanxi Province
  • 2011 Vol. 30 (5): 1406-1414. 
  • Abstract ( ) PDF (642KB) ( )
  • Using the monthly and yearly precipitation data at 30 weather stations in Shanxi Province during 1957-2003 and three drought indices, namely the precipitation anomaly percentage(R′ index), Z index and Palmer index calculated drought conditions of the northern, central and the southern part of Shanxi Province and the whole province. The determination of the three indices were compared and analyzed. The obtained results are as follows (1) comparing with the occurrence frequency of flood and drought years, the credibility of the drought trend judged by R′ index is the highest, P index is second, Z index is relatively low; (2) the drought intensity grade determined by Z index is two grade as well as R′ index and one grade as well as Palmer index. The drought intensity determined by Palmer index relatively conform to realisty; (3) the R′ index directly expression the impact of amount of rainfall on drought and flood, Z′ index is more suitable for a single station to reflect changes in drought and flood. P index has more advantage in describe the intensity of the regional drought.
  • Impact of Temperature Change on Energy Consumption ofResidential Building in East China
  • 2011 Vol. 30 (5): 1415-1421. 
  • Abstract ( ) PDF (755KB) ( )
  • Based on the mean daily temperature data from 478 meteorological stations during 1961-2007 and those from RegCM3 model during 2010-2039, the spatial and temporal variationsof heating and cooling degree-days and their relationships with the temperature variation in East China were analyzed. The results indicated that from 1961 to 2007, heating degree-days firstly increased and then decreased, but cooling degree-days firstly decreased and then increased in East China. The heating degree-days will decrease and the cooling degree-days will increase continuously in East China during 2010-2039. Spatially, the heating degree-days basically decrease in the whole East China in the past 47 years and in the future 30 years, with more decrease in the northern parts and less decrease in the southern parts of East China. The cooling degree-days increased more in the Yangtze Delta regions, the eastern parts of Zhejiang and Fujian in the past 47 years, but in the future 30 years, they will increase more in the central and western parts of East China, and less in the northern parts and eastern coastal areas of East China. There are high correlations between the variationsof heating and cooling degree-days and thoseof temperature. In the past 47 years, the heating degree-days decreased by 7.1%, and the cooling degree-days increased by 16.7% in East Chinadue to the rise of temperature. In the future 30 years, temperature will rise significantly, and the heating degree-days will decrease by 8.2%, and the cooling degree-days will increase by 29.6% compared with those during the period from 2010 to 2019.

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