Plateau Meteorology

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28 February 2017, Volume 36 Issue 1   
  • Characteristics of the Surface Sensible Heat on the Qinghai-Xizang Plateau in the Spring and Its Influences on the Summertime Rainfall Pattern over the Eastern China
  • ZHANG Changcan;LI Dongliang;WANG Hui;DAI Yifei
  • 2017 Vol. 36 (1): 13-23.  DOI:10.7522/j.issn.1000-0534.2016.00028
  • Abstract ( ) HTML PDF (4109KB) ( )
  • Based on the 70-station monthly surface Qinghai-Xizang Plateau sensible heat (QXPSH) data derived from the station observation data combined with the NASA-made normalized difference vegetation index (NDVI) data for the period of 1982-2012, the monthly summer precipitation data at 160 stations in the eastern China covering 1951-2012 and the monthly NCEP/NCAR I reanalysis data, the spacial-temporal variability of the QXPSH and its influence on the later summer rain pattern over the eastern China are analyzed through statistical method including EOF, SVD, etc.Results from observation and reanalysis dataset show that:(1) In the 1990s, the Ⅲ rainfall pattern appears most times in China, and the eastern China experiences more frequent precipitation, especially regions along the Yangtze River.As the rainfall pattern shifts northward since the 21st century, the Ⅱ rainfall pattern began to increase.(2) Generally, the spring (March-May) QXPSH is strong in the west but weak in the east.The surface sensible heat flux is strongest in May and its interannual variability is most obvious.On the spatial evaluation, there are two patterns of "consistent change" and "east-west reverse change", and they have a turnabout in 2003.(3) When the spring QXPSH is on its negative (positive) phase, the high (low) pressure anomalies over northern China, the weak (strong) South Asian high that located westward (eastward), and the water vapor flux diverges in the vicinity of South China (Yangtze River and Hetao River), it results in the rainfall pattern shifting southward (northward) in the eastern China.
  • Dynamic Snow-Melting Process and Its Relationship with Air Temperature in Tuotuohe, Qinghai-Xizang Plateau
  • ZHOU Yang;XU Weixin;BAI Aijuan;ZHANG Juan;LIU Xiaojing;OUYANG Jianfang
  • 2017 Vol. 36 (1): 24-32.  DOI:10.7522/j.issn.1000-0534.2016.00013
  • Abstract ( ) HTML PDF (822KB) ( )
  • The recognition and research of high-frequency dynamic snow-melting process in hinterlands of Qinghai-Xizang Plateau are insufficient due to the restriction of natural conditions and observation data.In this paper, every-30-minute snow depth and air temperature synchronous observation data of Tuotuohe area in the winter of 2013-2014 are used to investigate the dynamic snow-melting process in November and its relationship with air temperature.The results indicate that the snow in the Central Qinghai-Xizang Plateau melts slowly at first but then quickly during the whole snowmelt process, and especially rapidly during the last period.The change of snow depth is closely related to the air temperature.3 hours before the snow melting, temperature will significantly affect snow depth change.Significant correlation exists between snow depth and simultaneous or advanced 30 minutes air temperature.The linear correlation coefficients can reach-0.3589 and-0.3600 respectively under significant test of 0.01.Considering the lag effect of temperature, the snow melting has occurred at-13℃.The main snow melting temperature range is from-2℃ to-4℃, which is obviously lower than the snow-melting critical temperature in other mountainous areas of China.The snow melting process mainly occurred during the period of 12:00-18:00.In addition, the snow depth decreases rapidly during 12:00-13:30 and 16:30-18:00.It should be noticed that the snow depth has no obvious variation from 14:00 to 16:00, which seems to supply good heat condition.The correlation coefficient between the snow depth and the sunshine duration is-0.845.In the early stage of snow melting process, air temperature has a stronger impact on snow depth than the sunshine duration, and oppositely in the last stage.Snow melting process has a complex relationship with heat conditions and sunshine duration, indicating that snow ablation is certainly contacted with solar radiation, ablation status, snow characters and sublimation process.
  • Estimating the Soil Thermal Parameters and Modeling the Soil Temperature in Litang of Qinghai-Xizang Plateau
  • ZHANG Yonghui;GAO Zhiqiu;TONG Bin
  • 2017 Vol. 36 (1): 33-44.  DOI:10.7522/j.issn.1000-0534.2016.00015
  • Abstract ( ) HTML PDF (1759KB) ( )
  • In order to obtain the soil thermal parameters accurately, the soil thermal diffusivity is calculated by phase method, amplitude method and thermal conduction-convection algorithm respectively, and water flux density is calculated by the thermal conduction-convection algorithm, using the soil temperature data collected from Litang site over Qinghai-Xizang Plateau during 27 August to 4 September 2006.Taking the soil temperature at the surface as the upper boundary, the temperature during 19 to 21 September 2006 for the soil layers at the depth of 10 cm, 15 cm and 20 cm are modeled by the three methods mentioned before based on the computed soil thermal diffusivity and water flux density results.The results show that:due to taking the soil water movement into account, the correlation coefficients between the modeled values simulated by thermal conduction-convection algorithm and the observed data are the highest, r10cm=0.97, r15cm=0.98 and r20cm=0.99, respectively, confidence level is 99%.On the depth of 0.1 m, the soil temperature phase shift is overestimated about 0.21 hours by the thermal conduction-convection algorithm.However, the amplitude methods overestimate the phase shift more than 0.45 hours.The daily amplitude of soil temperature is overestimated about 0.79℃ by the thermal conduction-convection algorithm, but more than 0.96℃ by the phase methods.The thermal conduction-convection algorithm simulates the soil temperature better than the other two methods.
  • Analysis of the Qinghai-Xizang Plateau Monsoon Evolution and Its Correlation with Soil Moisture
  • ZHOU Juan;WEN Jun;WANG Xin;JIA Dongyu;CHEN Jinlei
  • 2017 Vol. 36 (1): 45-56.  DOI:10.7522/j.issn.1000-0534.2016.00003
  • Abstract ( ) HTML PDF (8387KB) ( )
  • The Plateau monsoon evolution is essential to synoptic climatology process over the Qinghai-Xizang Plateau.Based on the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis data from 1979 to 2014, a new Plateau Monsoon Index (ZPMI) which could effectively quantify the monsoon evolution is constructed, and it is compared with the existing plateau monsoon indices TPMI, DPMI and QPMI.The results show that, the onset and retreat time of the Plateau monsoon represented by TPMI is about 1~2 months earlier than that of ZPMI, DPMI; and the ZPMI can better quantify the climatological monthly and inter-annual variations in precipitation over the Qinghai-Xizang Plateau.While the plateau summer and winter monsoons both have similar inter-annual and inter-decadal variation characteristics of a rising trend, and the increasing trend of the summer monsoon is more significant.And the ZPMI is also capable of effectively quantifying the meteorological elements.In stronger plateau summer monsoon years, more (less) precipitation and higher (lower) air temperature appear over the eastern and central (western) plateau, and vice versa.The summer ZPMI and soil moisture in April and May over the Qinghai-Xizang Plateau are used to explore the influences of soil moisture on the Plateau monsoon, and a significant correlation was found between the soil moisture in spring (April-May) over the Qinghai-Xizang Plateau and Plateau summer monsoon.It is found that when the soil moisture over the central and eastern Plateau is higher (lower), while the soil moisture over the western Plateau is lower (higher) than normal, the Plateau summer monsoon may be stronger (weaker).
  • Top-Layer Soil Moisture Retrieval over the Qinghai-Xizang Plateau in Summer Based on AMSR-E Data
  • LI Zhe;WANG Lei;WANG Lin;LI Xiehui;XIAO Guojie
  • 2017 Vol. 36 (1): 67-78.  DOI:10.7522/j.issn.1000-0534.2016.00085
  • Abstract ( ) HTML PDF (5078KB) ( )
  • Utilizing AMSR-E brightness temperature data, we adopted a simplified and modified Single Channel Algorithm model (SCA) to estimate the surface soil moisture (SM) of the Qinghai-Xizang Plateau from June to July 2011.To validate and contrast the retrievals, we used two kinds of soil moisture products based on AMSR-E from NASA and VUA-NASA, and in-situ SM data from Maqu network and CTP-SMTMN (Soil Moisture and Temperature Monitoring Network on the central Qinghai-Xizang Plateau, hereafter called Naqu network).The results indicated that:(1) Compared VUA-NASA products with SM retrievals by modified SCA model, the NASA product has a higher MAE (Mean Absolute Error), RMSE (Root Mean Square Error) and a lower correlation coefficient both in pixels and areas, apparently underestimating the SM of the two areas.(2) VUA-NASA product has a good performance in Maqu area, while in Naqu area it has a high correlation coefficient but relatively large MAE and RMSE resulting in a worse precision.(3) In contrast to other two products, modified SCA model has a better accuracy in two areas and provides reliable information on surface SM temporal variability with the low MAE (about 0.050 m3·m-3), RMSE (about 0.060 m3·m-3) and high correlation coefficient (about 0.800).We conclude that the modified SCA model can be applied to SM monitoring in the Qinghai-Xizang Plateau, and offer a good reference to study of climate and weather changes as well as hydrological cycle in the Qinghai-Xizang Plateau.
  • Study on Pan Evaporation and Energy Change Process by Micro-Meteorological Method
  • CHEN Bolong;ZUO Hongchao;GAO Xiaoqing;GUO Yongtao;LU Sha;YANG Yanlong
  • 2017 Vol. 36 (1): 87-97.  DOI:10.7522/j.issn.1000-0534.2016.00021
  • Abstract ( ) HTML PDF (2821KB) ( )
  • Pan is used as an instrument of measuring the evaporation demand of atmospheric, and is widely used in hydrological and meteorological stations.In order to deeply understand the physical significance of pan evaporation, a field experiment "Inner Mongolia Pan Evaporation Experiment (IMPEEX)" is carried out in the arid region of northwest China.Based on the energy balance principle, the evaporation processes of Class A, 20 cm and E601B pans are measured minutely with micro-meteorological method.The observations results show that the diurnal variations of three types of pans evaporation processes have significant differences owing to the non-uniformity intensity between water body of pan and the surrounding environment.Temperature stratification of water in the pan is increasing with the depth of water.The heat flux between E601B pan water and around soil fluctuates between ±10 W·m-2, and the sum of this flux is almost 0 at daily time scale.The albedo of water surface of Class A pan is displays "U" type at sunny days, and the daily averaged albedo is 0.087.Energy balance of water of pans analysis shows that the solar radiation and water thermal storage rate are the main two components of energy which control the pan evaporation, the sensible heat flux at water surface and heat conduction through pan wall and bottom are subordinate components.
  • Comparison Analysis of Variability of Meteorological Elements Observed at Three Mountain Observatories over Central-Eastern China
  • ZHANG Jianming;YE Chengzhi;MO Ruping
  • 2017 Vol. 36 (1): 107-118.  DOI:10.7522/j.issn.1000-0534.2015.00103
  • Abstract ( ) HTML PDF (24208KB) ( )
  • Linear regression and wavelet analysis are performed on wind, temperature, and precipitation observed at three mountain meteorological observatories (Nanyue, Lushan and Huangshan) in central-eastern China over a 57-year period (1956-2012).The results show that:(1) significant decreases in annual-mean wind speed at these mountain observatories.(2) In comparison, the wind speed at Nanyue station and Huangshan station increased in the early period from the late 1950s to the late 1960s, decreased significantly from the late 1960s to the late 1990s, and increased slowly since 2000, whereas the wind speed at Lushan station exhibits a steady decreasing trend through the 57-year period.The annual-mean hourly maximum wind speeds at these three observatories dropped abruptly in the 1960s, and then followed by a steady decreasing trend thereafter.(3) The wind direction experienced remarkable seasonal transition at all observatories.The prevailing wind was southerly in the warm season from April to September, northerly in the cold season from October to March at all observatories.(4) Significant inter-annual oscillations of 2~3 years and 5~7 years and various decadal oscillations were identified in wind speeds at the three stations.Significant increasing trends with quasi-oscillations of 2~3 years, 5~7 years, and 13~17 years are identified in the maximum/mean/minimum temperatures at all observatories.(5) The variations of annual precipitation amount and rainy days were similar at all three stations.A weak increasing trend existed in annual precipitation amounts.A significant increasing trend in rainy days at Nanyue and Lushan stations, but a significant decreasing trend at Huangshan.At the three stations, quasi-oscillations of 2~3 years, 5~7 years are found in the annual precipitation amounts, and quasi-oscillations of 2~3 years, 5~6 years, 10~12 years are found in rainy days.
  • Preliminary Analysis of Representativeness of Precipitation Observation over Southwest China
  • LI Nina;LI Jian
  • 2017 Vol. 36 (1): 119-128.  DOI:10.7522/j.issn.1000-0534.2016.00008
  • Abstract ( ) HTML PDF (7510KB) ( )
  • The representativeness of rain gauge stations over southwestern China is a long-standing problem because of the influences of complex topography and local distributions of stations.Based on the interannual variability of precipitation, this paper targets investigating the spatial representativeness of precipitation data.First, the Dali National Climate Observatory was used as an example to quantitatively evaluate the spatial representativeness of a single station, and the result shows that the representative area of the precipitation at Dali station is mainly concentrated on a north-south narrow strip and covers an area about 5000 km2 due to the influences of surrounding north-south-oriented ridges.Based on the understanding of spatial representativeness of a single station, the station network coverage in the current region has been analyzed by using rain gauge data and APHRODITE precipitation data.The results suggest that the spatial coverage of station observation is good at the regions that have high station network density or are flat basins, and the number of stations covering these areas is above 40.It is poor at the main body of Tibetan Plateau, and the area with no observation accounted for 15.90% of the entire southwest region, which is mainly distributed in the north and southwest of plateau body.Considering the importance of spatial differences of interannual precipitation variation to the representativeness of station observations, this problem is further studied based on the CMORPH satellite rainfall data.The spatial difference of rainfall at basins and plateau valleys is small, and the transition regions between mountains and basins have significant difference.We suggest that more stations can be set up over the area with large differences in precipitation variability but without observational stations.
  • Evaluation of Precipitation Probability Forecasts of ECMWF Ensemble Prediction System in Central China
  • PAN Liujie;ZHANG Hongfang;CHEN Xiaoting;QU Liwei;YUAN Yuan
  • 2017 Vol. 36 (1): 138-147.  DOI:10.7522/j.issn.1000-0534.2016.00014
  • Abstract ( ) HTML PDF (7484KB) ( )
  • Using precipitation forecasting data of ECMWF ensemble forecast from May to October in 2013 and 2014, hourly fusion precipitation data of CMORPH (NOAA Climate Prediction Center Morphing Method) satellites and gauged rainfall from about 30000 automatic weather stations, based on Brier score, Talagrand distribution and ROC (Relative operating characteristic) analysis, the precipitation probability forecast ability of ECMWF ensemble system in central China is studied.Results show that:ECMWF ensemble system has stable forecast skill for light rain, but probability forecast is large; the resolution for heavy rain or rainfall magnitude greater than heavy rain is low, and probability is small.Talagrand distribution overall show "U" shape, forecast frequency for moderate precipitation is less; as for the consistency of forecast and observation in different magnitude rainfall, the longer the forecast time is, forecast ability more stable; ensemble members' divergence have apparent changes in 11th forecast day, Talagrand distribution show "clocks" shape, forecast score decreased significantly.The shorter the forecast days, the better the precipitation probability forecast, on average, forecast time more than 2 days, forecast skill of 12 hours (24 hours) rainstorm probability less than 30% (40%) is lower than climatic prediction.24 hours precipitation forecast has higher hit rate and lower false rate compared with 12 hours forecast, forecast skill is better; in previous six days, ROC area of 12 hours precipitation probability forecast is better than 24 hours.
  • Sensitivity Analysis of Multi-Source Observations in WRF-ADAS Rapid Refresh System
  • WANG Xiaofeng;WANG Ping;ZHANG Lei;LI Jia;XU Xiaolin
  • 2017 Vol. 36 (1): 148-161.  DOI:10.7522/j.issn.1000-0534.2016.00018
  • Abstract ( ) HTML PDF (62972KB) ( )
  • Using SMS-WARR system with rapid refresh technique, the sensitivity of three different types of observational data (Doppler radar reflectivity, radiosonde, AMDAR) to the numerical simulation of the severe convection event was analyzed.The impacts of these three different types of observations were discussed through a numerical simulation of a server convection event, which occurred in Shanghai on July 31 2011.Results showed that assimilating radar data was helpful for adjusting model initial hydrometer distributions, the simulated distribution of cloud was reasonable, the structure and intensity of the mesoscale convection system was adjusted to some extent, and the forecasted rainfall location and intensity were also improved.Although only one time piece of the radiosonde data was assimilated during the whole simulation cycle, the impact of radiosonde data assimilation on the model forecasting still can be kept and maintained for a long time.Results showed that the simulated height and wind fields at 500 hPa, 700 hPa and 850 hPa were improved after radiosonde data assimilation.Correspondingly, the simulated surface temperature was also improved.Results from AMDAR data assimilation experiment showed that the location and strength of synoptic situation are more close to the observations and the rainfall forecast was improved.
  • Influence of Sensible Heat on Planetary Boundary Layer Height in East Asia
  • WAN Yunxia;ZHANG Yu;ZHANG Jinwen;PENG Yanqiu
  • 2017 Vol. 36 (1): 173-182.  DOI:10.7522/j.issn.1000-0534.2016.00001
  • Abstract ( ) HTML PDF (4605KB) ( )
  • By using the monthly global planetary boundary layer height (PBLH) and sensible heat reanalysis data provided by the NCEP/CFSR, utilizing different statistical methods, the trend of the planetary boundary layer height and sensible heat are discussed.The relationships of PBLH and sensible heat have been studied with singular value decomposition (SVD).The results are showed as following.The trend of PBLH in summer increased in the east of eastern Asia, but decreased in the west of the region.The trend of PBLH in winter increased in the west of eastern Asia, but decreased in the east of the eastern Asia.In summer, the trend of sensible heat decreased in the Qinghai-Xizang Plateau but increased in the other regions.The trend of sensible heat in winter decreased in the Xinjiang region and the east of China, but increased in the east of the eastern Asia.In summer, the first mode of singular vectors (SVD1) is founded when the sensible heat reduced in the Qinghai-Xizang Plateau; the PBLH in the corresponding region reduced.When the sensible heat increased in the east of Inner Mongolia and the northeast China, the PBLH in the corresponding regions increased.The SVD1 is characteristic of interdecadal variation.For the SVD1, to a certain extent, the changes of PBLH in the Tibet Plateau, Eastern Inner Mongolia and Northeast China are mainly influenced by the surface heating.The SVD2 in summer shows when the sensible heat increased (or reduced) in the north of China and the south side of Qinghai-Xizang Plateau, the PBLH in the corresponding regions increased (or reduced).The SVD2 in summer is characteristic of interannul variation.This mode shows the difference of both PBLH and sensible heat in the region of the south side of the Qinghai-Xizang Plateau and that in the main body of the Qinghai-Xizang Plateau.In winter, the SVD1 shows the out-of-phase distribution between the regions of east of eastern Asia and west of eastern Asia.The SVD2 in winter shows the out-of-phase distribution between the both of the North and East China regions and the other regions.Those two of modes in winter are characteristic of interdecadal variations.In the region of the Qinghai-Xizang Plateau and its south side, and the arid and semi-arid region of northwest China, the PBLH changes are mainly influenced by surface heating, but in the eastern monsoon regions, the change of sensible heat is only one of the factors affecting the change of PBLH.
  • Spatiotemporal Characteristics of Summer Rainstorm Days in Gansu Province and Their Relationships with the Atmospheric Circulation
  • HUANG Yuxia;WANG Baojian;WANG Yanfeng;HUANG Wubin
  • 2017 Vol. 36 (1): 183-194.  DOI:10.7522/j.issn.1000-0534.2015.00118
  • Abstract ( ) HTML PDF (32398KB) ( )
  • Because of characteristics of summer rainstorm easy to form disasters, difficultly to forecast, so it has been the focus of the study.Gansu province is located in the upper reaches of the Yellow River, the region at the confluence of the Loess Plateau, the Inner Mongolia Plateau and the Qinghai-Tibet Plateau.Climate type variety are complex, special geographic location and significant spatial variation of precipitation make forecast exceedingly difficult in Gansu province.Previous studies are mostly for the heavy rainstorm, rarely studied the characteristics of the rainstorm days change, but the rainstorm days is also an important indicator of climatic characteristics of heavy storm days in Gansu province.In order to study climate change characteristics and laws of the rainstorm, improve the accuracy of the rainstorm forecast, using daily precipitation data at 80 stations in Gansu Province, NCEP/NCAR reanalysis datasets during 1974-2013, and following empirical orthogonal function, system clustering and composite analysis method, the spatial and temporal variation characteristics of rainstorm days during summer in Gansu province and their relationships with the atmospheric were studied.The results showed that:Rainstorm days in Gansu province experienced three significant interdecadal variation process in recent 40 years during summer around 1989、2002、2009.According to the EOF and cluster analysis, the summer rainstorm days were divided into four distribution patterns, namely the Hedong strong and Hexi weak pattern, Gansu mountain of Minxian pattern, Longnan and Longdong pattern, the whole province pattern.The summer rainstorm days were closely related to the East Asian summer monsoon in the South China Sea with more available moisture.The Hedong strong and Hexi weak pattern and Longdong and Longnan pattern were related to the movement of cold wave.The Hedong strong and Hexi weak pattern corresponded to strengthen with cold vortex of Lake Baikal, cold air south, the monsoon with its position by northwest, moisture from the South China Sea and the East China sea transporting to east.The Gansu mountain of Minxian pattern pattern corresponded to the monsoon with its position by north, moisture from the South China Sea and the Bengal bay transporting to west and meeting in Gannan region.The Longdong and Longnan pattern corresponded to Iran high and Mongolia low weaken, cold air activity reducing, the monsoon with its position by south, moisture from the South China Sea transporting to southeast, cold air backflow more likely to resulted in forming precipitation in Longdong and Longnan region.The whole province pattern corresponded to the monsoon with its position by the Tibetan plateau, moisture from the South China Sea and the Bohai Sea transporting to westwards extending and northwards advancing that impacting most regions of Gansu Province.
  • Influence of Thermal and Dynamical Conditions over Beijing City Area on Strength of Down-to-Hill Thunderstorms
  • SUN Jing;CHENG Guangguang
  • 2017 Vol. 36 (1): 207-218.  DOI:10.7522/j.issn.1000-0534.2016.00007
  • Abstract ( ) HTML PDF (11701KB) ( )
  • There are some γ-scale thunder storms moving from either the west or north mountain areas to the city of Beijing under the weak circulation systems of synoptic scale within 15-17 June 2014.It is interesting that the strength of each down-to-hill thunder storm is changing differently.For example, the first and the last moving storms become stronger while closing to the city of Beijing, but the others become weaker, which increases the difficulties in the prediction for the local forecasters.In order to find the clues to understand the various changing, several observation data, such as surface auto weather station data, sounding data, wind profiles and Doppler Radar data, are used to analysis these cases.According to the study, except for the strength of moving storms themselves is an obvious factor to influence the changes after leaving the hills, an important reason been found is that the thermal and dynamic energy would be consumed, the cold pool and the downward flow are created by the moving of the thunder storms from mountain to the plain at first, so there is not enough energy and advantages available for the next thunder storms' to development.Then with the temperature of the plain increasing because of the sunshine and south wind, the thermal and dynamical condition become advantageous available again to maintain and strengthen the convective cell.Moreover, it should be noted that if the thunder storms' strength can be intensified in the mountain area, then the strength will maintain and even become stronger easily when leaving away from the hill.In conclusion, it is necessary to observe the change of the thermal and dynamic conditions in city areas, which is key to successfully forecast the strength change of down-to-hill thunder storms.
  • Using 3 mm Cloud Radar Data to Analyze Frontal Mixed Cloud Vertical Structure and Supercooled Water
  • HUANG Yimei;ZHOU Yuquan;YANG Min
  • 2017 Vol. 36 (1): 219-228.  DOI:10.7522/j.issn.1000-0534.2015.00119
  • Abstract ( ) HTML PDF (11295KB) ( )
  • The vertical structure of the cloud directly affects the micro-physical processes, thus affecting the occurrence and intensity of precipitation.Cloud Radar can be used to directly detect the vertical structure of the cloud, which is of great significance to understand the physical process of cloud precipitation.The theory of the artificial rainfall and operating conditions identification technology research is very focus on the distribution of mixed phase clouds and supercooled water in the front.Many scholars mainly analyze the vertical structure of the cloud and the distribution of supercooled water from the aspects of telemetry, in-cloud observation and numerical model.With 3 mm wave cloud radar data and sounding data, the vertical structure and distribution of supercooled water of two frontal mixed cloud processes from 6 to 8 November 2008 in Shouxian, Anhui were analyzed in detail.The vertical strcture analysis included the cloud structure analysis in cold region, the bright band analysis in melting layer and the cloud structure analysis in warm region.The results show that Shouxian in Anhui Province had been affected by the impact of the west weak cold front and the east cold front on 6~8 November 2008.It produced thick mixed phase cloud in 11:00-13:00 (BJT, the same as after) on 6 and in 01:00-04:00 on 7, but the precipitation of the two periods was relatively small.Frontal mixed cloud existed "Sow-Supply" vertical structure in this process.The top temperature of the frontal mixed phase cloud was low, the ice crystals produced in the cloud, then dropped to provide the "Sow effect".There was some supercooled water in the cloud, which provided "Supply effect" to the dropping ice and snow crystals.Frontal mixed cloud has echo intensity, Doppler velocity and velocity specturem width three bright bands.Because of the ice and snow crystals in the melted surface had the reflection characteristics of water droplets, and different sizes ice and snow crystals with different melting time and different drop final velocity, the velocity specturem bright band with a height less than Doppler velocity bright band, and Doppler velocity bright band with a height less than echo intensity bright band.In a cloud field with uneven horizontal structure, falling particle swarm has obvious "filtering effect", which is not conducive to the growth of raindrops.Therefore, the radar echo intensity and the Doppler velocity region were not consistent, the Doppler velocity region appeared in the front of the strong echo area in the middle and upper part of the warm region.There were certain supercooled water in frontal mixed cloud, and the vertical distribution of supercooled water was not continuous, and the distribution of the temperature range was relatively wide.Because of 3 mm cloud radar observation data is less in China, this paper only analyzed a case of frontal mixed phase cloud vertical structure, and the results still need more data for further validation.In addition, the temperature range of the supercooled water distribution obtained by the inversion algorithm of Shupe and the temperature range of the observation of the supercooled water in China has a certain difference, but also need to be furher confirmed.
  • Influence of Climatological Calibration Algorithm on Accuracy of TMPA 3B42 V7 Product
  • CAI Yancong;XU Leilei;JIN Changjie;WANG Anzhi;GUAN Dexin;WU Jiabing;YUAN Fenghui;BU Changqian
  • 2017 Vol. 36 (1): 256-267.  DOI:10.7522/j.issn.1000-0534.2015.00113
  • Abstract ( ) HTML PDF (4078KB) ( )
  • The satellite-based precipitation is a key data source for investigating regional precipitation, especially over ungauged area, which can improve the knowledge of understanding pattern of precipitation.However, due to the limited spatial coverage of calibration data, for the widely used Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) 3B42 data, the new Climatological Calibration Algorithm (CCA) fails to effectively implement in the mid-high latitude regions, which leads to much more uncertainties and errors exist in TMPA.Two representative regions with similar climate and topography are selected, which located inside and outside the coverage of TRMM satellites (38°N, 38°S), respectively.The similarity and difference in data accuracy between two regions are analyzed by four statistical indexes to reveal the effect of CCA on TMPA, based on observation data from weather stations during 1998-2012.The results indicate that there is a general overestimation of precipitation at daily, monthly and annual scale in both regions.Particularly, precipitation event ranging from 0 and 10 mm is severely overestimated.Though CCA can not get rid of this overestimation, the degree of overestimation is alleviated to some degree.It is clear that the degree of overestimation is higher in Liaoning with 8.87% than that in Shandong with 2.79%.In terms of variation of precipitation, the monthly and annual precipitation can be regenerated by TMPA.TMPA follow the similar trends to the observed.It is noted that, an unsatisfactory accuracy is shown for two regions with large fluctuations in annual variation during winter.But the application of CCA in TMPA in Shandong, makes an improvement in correlation between two precipitation datasets and weaken the degree of overestimation of precipitation by TMPA.
  • Numerical Simulation Studies on "2012·7·29" Rainstorm Process in Ningxia
  • WANG Hui;LONG Xiao;WEN Xiaopei;TIAN Feng;LIU Yanfei
  • 2017 Vol. 36 (1): 268-281.  DOI:10.7522/j.issn.1000-0534.2016.00017
  • Abstract ( ) HTML PDF (23893KB) ( )
  • Based on the routine observation data, Yinchuan doppler radar data, FY-2E satellite TBB data and the output of high resolution in temporal and spatial from WRF model, the paper analyzed and discussed a rainstorm process, which happened from 29 to 30 July 2012 ("7·29 rainstorm process" for short).The main results are as follows:(1) The development of rainstorm is closely related to upper-level jet at 200 hPa, short-wave trough at 500 hPa, the shear line at 700 hPa.(2) Eastward low vortex, warm-type shear line and low level jet (LLJ) are the main reasons of rainstorm.The low level jet (LLJ) came into being at 20:00 on 29 July, which maintained for about 7 hours.(3) Strong divergence at the right side of upper-level jet exit region, which occurred before the convergence in low level and maintained, is crucial for the formation and maintenance of obviously upward motion and low level jet.(4) The region of ΔNBE has a corresponding relationship with the rainfall region, which is large in convective precipitation stage, and quite small in stable precipitation stage because of the diferrent quasigeostrophic balance in two periods.(5) The water vapor transfer is mainly from the south wind of low level jet, which is corresponded to the formation and development of the LLJ.The variation of net water vapor transport is consistent with the feature of convective precipitation and stable precipitation.

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