Current Issue

• Impacts of Microphysics and PBL Physics Parameterization on a Convective Precipitation over the Qinghai-Tibetan Plateau
• LUAN Lan;MENG Xianhong;Lü Shihua;LI Zhaoguo
• 2017 Vol. 36 (2): 283-293.  DOI:10.7522/j.issn.1000-0534.2016.00086
• Abstract ( ) HTML PDF (10294KB) ( )
• A convective precipitation occurred in Nagqu over the Qinghai-Tibetan Plateau was simulated using WRF model with different microphysics and PBL physics options in this work. The simulations and observations were compared to understand the influence of the different microphysics and PBL physics options. The results show that WRF model can reproduce the precipitation, but a deviation of precipitation center exists between the simulation and the observation, which leads to discrepancies between them. Comparing the simulations with TRMM, a remote sensing product, the time when convention occurred is close. In addition, differences were produced by using different initial and boundary inputs. Overall, the simulations using ERA-Interim datasets as inputs produced better precipitation pattern than that using the NCEP FNL datasets, comparing with the TRMM datasets. By analyzing the differences of water vapor flux, water vapor flux divergence and vertical wind between the simulations with different microphysics and PBL physics options, it is found that the simulation of precipitation is more sensitive to the PBL physics than the microphysics options.

• Characteristics of the Moist Pool over the Qinghai-Tibetan Plateau and Its Variation
• ZHOU Changyan;DENG Mengyu;QI Dongmei
• 2017 Vol. 36 (2): 294-306.  DOI:10.7522/j.issn.1000-0534.2016.00042
• Abstract ( ) HTML PDF (3509KB) ( )
• Characteristics of the Moist Pool over the Qinghai-Tibetan Plateau and its variation are analyzed by using ERA-Interim reanalysis data from 1979-2011.The result shows that, under the climate average state, to the global middle-high levels, there exists an entire layer of high humidity area over the Tibetan Plateau from June to September, which is known as the Qinghai-Tibetan Plateau Moist Pool in this paper. The vertical features of the Plateau Moist Pool are studied through the relative zonal difference of specific humidity. It is found that, during June and September, the Plateau Moist Pool is a vertical, deep and maximum center of the water vapor content to other parts of the globe at the same latitude. The value of water vapor content at different level inside the Moist Pool is above one time to three times of the zonal average. The high value areas of the relative zonal difference of specific humidity inside the Plateau Moist Pool are obviously extending obliquely to the downstream regions with the increase of the altitude and can reach 120°E and the areas east to it. The empirical orthogonal function (EOF) analysis shows that the Plateau Moist Pool in summer has three modes in spatial distribution as follows: the same signs in the whole, the reverse signs in the western and eastern, and the reverse signs in the southern and northern. The summer intensity index of the Plateau Moist Pool is defined in this paper, and it is found the Moist Pool has a significant increase trend in summer from 1979 to 2011, mainly with the oscillation cycle of 3~4 years and 7~8 years. The Plateau Moist Pool in summer has changed significantly around 1997.Since 1998, the Plateau Moist Pool in summer enhanced significantly, and the increase trend in the western is more stronger than that in the eastern. In the west of the Moist Pool, the increase trend of the upper air is stronger than that near the surface, and the maximum center is located near the 400~200 hPa. Finally, the results with three kinds of reanalysis data and the relating researches using sounding data and satellite data are integrated to analyze the applicability of the data in the study, and the analysis shows that the data for this study is applicable, and the results based on ERA-Interim reanalysis data in this paper are credible.

• Analysis of the Characteristics of Deep Soil Heat Flux in Qinghai-Tibetan Plateau
• ZHOU Ya;GAO Xiaoqing;LI Zhenchao;HUI Xiaoying;YANG Liwei
• 2017 Vol. 36 (2): 307-316.  DOI:10.7522/j.issn.1000-0534.2016.00120
• Abstract ( ) HTML PDF (5545KB) ( )
• The surface thermal condition of Qinghai-Tibetan Plateau is not only important for the local weather and climate, but also for the short-term climate change in the surrounding areas, especially in sub-seasonal to seasonal scale. Soil thermal diffusivity and soil heat flux are two key factors to determine soil thermal condition. The spatial and temporal distribution of soil thermal diffusivity and the soil heat flux in Qinghai-Tibetan Plateau are still not well understood. In this paper, the method of Conduction-Convection was applied to calculate the soil thermal diffusivity and the soil heat flux in Qinghai-Tibetan Plateau by using monthly mean soil temperature at the depths of 0.8 m and 3.2 m in 39 meteorological observatories from 1980 to 2001.Their characteristics of annual and inter-annual variations and the relationship between soil heat flux and plateau monsoon were analyzed and got some meaningful conclusions. The results show that the annual amplitude of soil temperature decreases and phase of soil temperature delays with depth. The soil thermal diffusivity appears an overall decreasing trend from 1980 to 2001.The annual variations of soil heat flux have opposite phase between deep and surface. The annual variations of total heat flux and convective heat flux have the same phase. The monthly mean soil heat flux is negative during the winter, and positive in summer. The correlation coefficient between the soil heat flux and plateau winter monsoon index is-0.53.The soil heat flux is consistent with the plateau summer monsoon index, the correlation coefficient between them is 0.58.Both values pass the T-test with significance of α=0.05.These results are valuable for us to understand the plateau air-land interactions.

• Diagnostic Analysis Based on Wet Q-Vector of a Shear line with Rain on the East side of Qinghai-Tibetan Plateau under the Saddle Pattern Circulation Background Field
• LI Shanshan;LI Guoping
• 2017 Vol. 36 (2): 317-329.  DOI:10.7522/j.issn.1000-0534.2016.00025
• Abstract ( ) HTML PDF (20987KB) ( )
• Using NCEP global 1°×1° final-analysis data and hourly merged precipitation data of automatic weather station in china and CMORPH satellite data, with the theories of non-geostrophic wet Q -vector and moisture flux divergence, a heavy rain caused by a shear line on the east side of Qinghai-Tibetan Plateau on 28-29 July 2013 have been diagnostically analyzed. The results show that: The strong convergence shear line is along the stretching axis orientation of deformation field, which is located in the area between ascending and sinking movement. Horizontal distribution of 500 hPa non-geostrophic wet Q -vector have a good prediction of the next 6 h cumulative precipitation centre. The moisture flux divergence field shows that moisture convergence band is situated in shear line basically, and the distribution of wind field has a very important effect on moisture convergence. Moreover, the overlapping areas of moisture convergence band and non-geostrophic wet Q -vector convergence band have better implications of the heavy precipitation areas.

• Observation Study on Effects of Snow Cover on Local Micro Meteorological Characteristics in Maqu
• LI Danhua;WEN Lijuan;LONG Xiao;CHEN Shiqiang
• 2017 Vol. 36 (2): 330-339.  DOI:10.7522/j.issn.1000-0534.2016.00074
• Abstract ( ) HTML PDF (6883KB) ( )
• Using the observation data at Maqu station in integrated climate and environment observation station from Chinese Academy of Sciences from December 2011 to March 2012.The research station is located at Hequ horse farm of the southwest of Maqu County in Gansu Province. It's elevation is 3423 meteors, it's called the first bend of the Yellow River. Its unique location makes the climate cold in winter, the surface of the ground is mainly dominated by alpine meadow and alpine grassland. The three-snow cover process was analyzed, analyzing the different characteristics of the meteorology elements of the near surface between the snow cover and no snow cover, observation results show that: The snowfall process caused by cold air crossing makes the highest and lowest temperature of a day in 2.35 m decrease 10 ℃ in one day, temperature rise slowly after the snowfall, the average rate is 2.5 ℃ every day. The temperature gradient value is negative in the daytime and positive in the night, the absolute value of temperature gradient is larger below 7.17 meteors, and the value of 7.17~18.15 meteors is smaller, its value is less than 0.2 ℃·m^-1, the absolute value of 18.15 meteors is decreased to 0.05 ℃·m^-1. When the surface is covered with snow, the change trend's appearance in the morning that temperature decreases with height is one hour later than no snow cover, in the evening, the trend of the temperature increases with the increasing of height is one hour ahead. Snow cover reduce distribution range of temperature during the day, the reduction of second snow process is the most obvious because the large wind speed. In addition to 4.2~7.17 meteors for 11:00-16:00 on sunny days, snow cover will decrease the absolute value of temperature gradient in each layer. The absolute value of the 4.2~7.17 meteors temperature gradient in the sunny days is larger than 2.35~4.2 meteors during the period of 11:00-16:00, and the partial large amplitude increase when there is snow cover, it may be caused by the temperature advection that caused by different vegetation cover in the inner and outer surface of the observation field, when the wind speed is large, it will destroy the advection effect, and the temperature tends to be uniform in each layer.

• Study of Boundary Layer Parameterization Schemes' Applicability of WRF Model over Complex Underlying Surfaces in Southeast Tibet
• LI Fei;ZOU Han;ZHOU Libo;MA Shupo;LI Peng;ZHU Jinhuan;ZHANG Yu
• 2017 Vol. 36 (2): 340-357.  DOI:10.7522/j.issn.1000-0534.2016.00041
• Abstract ( ) HTML PDF (17477KB) ( )
• Southeast Tibet is the typical representative of complex underlying surfaces of the Qinghai-Tibetan Plateau, the boundary layer processes above this region are quite complex, which greatly challenge modeling and numerical weather forecasting. Accurate simulation and forecasting of local atmospheric processes depend on the choice of boundary layer parameterization scheme. In this study, the Weather Research and Forecasting model (WRF) was employed to simulate the convective and stable atmospheric boundary layer processes of Nyingchi district, Tibet. By comparing with the results from comprehensive campaign "Observation on the surface-to-air Exchange Processes in the Southeast Himalayas" (OSEP) carried out during the summer of 2013, the 5 boundary layer schemes ACM2, Boulac, MYJ, QNSE, and YSU from WRF model were evaluated for their applicability above complicated underlying surface in southeast Tibet. The results indicate that Boulac scheme and MYJ scheme perform the best on convective and stable boundary layer vapor mixing ratio simulation, respectively. ACM2 scheme is a more preferable parameterization scheme on potential temperature and wind filed vertical structure simulation over the complex underlying surface of southeast Tibet. Convective boundary layer height simulated by all schemes are lower than observations; While QNSE simulation shows the minimum deviation. Simulation ability of the same boundary layer parameterization scheme on convective boundary layer and stable boundary layer are different. Boundary layer wind field in this region is greatly weakened by orography. Near surface wind speed simulated are weaker than observation, MYJ and QNSE parameterization scheme shows the best result.

• Evaluation of Surface Air Temperature in Southwestern China Simulated by the CMIP5 Models
• WU Qing;JIANG Xingwen;XIE Jie
• 2017 Vol. 36 (2): 358-370.  DOI:10.7522/j.issn.1000-0534.2016.00046
• Abstract ( ) HTML PDF (4396KB) ( )
• The simulated abilities of 40 models for the surface air temperature in Southwestern China (SWC) are evaluated from the perspective of the warming amplitude, interdecadal variation and abrupt changes by using the surface air temperature observational data at 115 stations in Southwestern China (Sichuan, Guizhou, Yunnan and Chongqing) from 1961 to 2005 and the output of the historical simulations from 40 models participating in the Fifth Phase of the Coupled Model Intercomparison Project (CMIP5). The results show that most of the models can reproduce the increasing trend of the annual mean temperature in different areas of SWC in recent 45 years, however, only six models can better capture the features that the increasing amplitude of the surface air temperature is dependent on altitude. Annual mean temperature in lower altitude Sichuan Basin and Chongqing hills presents dropping trend from 1960s to 1980s, increasing trend from the late 1980s, and cool period from the middle of 1970s to the middle of 1990s. 10 modes could simulated the cooling trend, but the cooling trend and decadal slants cold time is well simulated in only 3 models. All models failed to simulate the characteristics of the temperature mutations. In general, model ACCESS1.0、CESM1-WACCM、CMCC-CMS、GFDL-CM2.1、GISS-E2-R-CC、MRI-ESM1、NorESM1-ME are relatively well in simulating the change of the surface air temperature in SWC, among them, the best is ACCESS1.0.

• Variation and Its Influences of 0 ℃ Isotherm Height in Summer over High Asia
• ZHOU Panpan;ZHANG Mingjun;WANG Shengjie;QIANG Fang;WANG Jie;ZHAO Peipei
• 2017 Vol. 36 (2): 371-383.  DOI:10.7522/j.issn.1000-0534.2016.00048
• Abstract ( ) HTML PDF (23395KB) ( )
• Based on radiosonde data and ERA-Interim reanalysis with resolution of 3°×3°, 2.5°×2.5°, 2°×2°, 1.5°×1.5°, 1.125°×1.125°, 1°×1°, 0.75°×0.75°, 0.5°×0.5°. The variation of 0 ℃ isotherm height in summer over High Asia during 1979-2012 is analyzed by using the climate tendency rate and linear interpolated. The relationship with latitude and altitude as well as the correlation of ERA-Interim reanalysis with different spatial resolutions and radiosonde data are discussed. The result indicates that variation of 0 ℃ isotherm height in summer since 1970s shows an increasing trend based on radiosonde data and ERA-Interim reanalysis with different spatial resolutions. 0 ℃ isotherm height based on the reanalysis data with resolution of 0.75 °×0.75° is fluctuate between 4800~5000 m which is close to the radiosonde data. 0 ℃ isotherm height based on the ERA-Interim reanalysis with different resolutions and radiosonde data have similar spatial distribution which are usually associated with latitude and altitude. In High Asia, 0 ℃ isotherm height showed an increasing trend from north to south and from low to high elevations. ERA-Interim reanalysis with different spatial resolutions interpolated to each stations have the negative bias of most interpolated gridded data and measured data during 1979-2012, which 0 ℃ isotherm height based on the reanalysis data exists cold bias with radiosonde data, in which the small cold bias of the ERA-Interim reanalysis with high spatial resolutions and radiosonde data has a greater proportion.

• Study on the Micrometeorological Characteristics over the Loess Plateau under the Influence of Thunderstorm
• ZHANG Xinke;CHEN Jinbei;YU Ye;ZHAO Suping;JIA Wei
• 2017 Vol. 36 (2): 384-394.  DOI:10.7522/j.issn.1000-0534.2017.00002
• Abstract ( ) HTML PDF (1577KB) ( )
• Based on the observation data from May 2012 to September 2012, the micrometeorological characteristics in the surface layer during gust, gale wind and hail were analyzed at the Pingliang Land Surface and Severe Weather Research Station. The results showed that there was strongly updraft a few hours before the occurrence of thunderstorm. The 30 minutes' average vertical velocity of the updraft could reach 0.25 m·s^-1 at 14 meters above the ground. When suffering server thunderstorms, the vertical velocity in this region is almost 1 to 2 orders of magnitude greater than normal. When the thunderstorm passed the station, the near surface pressure increased rapidly, the temperature fell sharply and the updraft quickly changed to downdraft. These are all because of the influences of the strong and cool downdraft divergence flow. Besides, the 30 minutes' average vertical velocity of the downdraft can reach-0.18 m·s^-1 at 14 meters above the ground. At the same time, there were strong temperature shear and the horizontal wind shear between the thunderstorm and the surrounding environment. They can lead to the extremely increasing in turbulence and sharply increasing of friction velocity, especially when gale wind and hail passed the station with the friction velocity twice than the maximum of its noon friction velocity. The turbulence spectrum analyses showed that the spectral energy of vertical velocity at low frequency region increased under the condition of the severe thunderstorm which not only increased sensible heat flux but also dominated turbulent flux. This may make development of thunderstorms.

• Characteristics of Spring Precipitation and Their Connections with the Spring Drought over the Loess Plateau during Last Three Decades
• WANG Danyun;Lü Shihua;HAN Bo;LI Zhaoguo;PAN Yongjie;MENG Xianhong;AO Yinhuan;WANG Xin
• 2017 Vol. 36 (2): 395-406.  DOI:10.7522/j.issn.1000-0534.2016.00121
• Abstract ( ) HTML PDF (5585KB) ( )
• Based on the observed precipitation with 52 meteorological stations from 1980 to 2014, the standardized precipitation index (SPI) within the Loess Plateau was calculated. Then the SPI was used to compare the temporal and spatial variation of the spring drought in different regions of the Loess Plateau in recent 35 years. The results showed that the temporal variation of SPI and precipitation in spring were similar. Both of them captured three severe drought events happened in 1995, 2000 and 2001; And their linear trends for 1980-2014 were negative. However, the spatial patterns of spring precipitation and spring SPI were different due to the difference of the probability density distribution about spring precipitation with different stations. The probability of light precipitation is higher in the northern than in southern Loess Plateau, and the heavy rainfall is more likely to happen in the southern region. For the whole Loess Plateau, if the spring precipitation is short but equal for everywhere in Loess Plateau, then the southern region might meet a severe drought measured by SPI. If the precipitation anomaly is negative and equal for everywhere, then the drought is more severe in the northern region. Therefore, the level of spring drought in the Loess Plateau are not only controlled by the amount of spring precipitation, but also determined by the probability density distribution of precipitation for different regions.

• Comparison of Different Stochastic Physics Perturbation Schemes on a Storm-Scale Ensemble Forecast in a Heavy Rain Event
• CAI Yuanchen;MIN Jinzhong;ZHUANG Xiaoran
• 2017 Vol. 36 (2): 407-423.  DOI:10.7522/j.issn.1000-0534.2016.00024
• Abstract ( ) HTML PDF (14032KB) ( )
• A weather forecast system is very sensitive to the model error. Particularly, the uncertainty in sub-grid parametrization process has the essential effect on the accuracy of weather forecast system. Due to small time scale, fast and strong nonlinear development of the storm-scale system, the traditional medium-range ensemble forecast method is obsolete. Stochastic Perturbed Parameterization Tendencies (SPPT) scheme, Stochastic Kinetic-Energy Backscatter (SKEB) scheme and mixed model perturbation (SKEB+SPPT) scheme are added to the storm-scale ensemble forecast system, in order to simulate a severe convection weather process in Anhui province on 31 May 2014.This paper evaluates the performance of ensemble forecast and analyses the characteristics of stochastic perturbation and kinetic energy evolvement. Results shows that the 60 km length scale and 3 h decorrelation time scale in SPPT are best in this case. The mixed model perturbation scheme increases (reduces) the spread and accuracy (the forecast error) of SPPT scheme only or SKEB scheme only, and decreases the mistaking and missing forecast of precipitation. The perturbation spatial distribution of the mixed model perturbation scheme is similar to that of the SPPT scheme at the beginning of forecast. As forecast time goes on, the perturbation spatial distribution is transformed and is similar to that of SKEB. The kinetic energy perturbation of the mixed model perturbation scheme is obviously bigger than that of SPPT only or SKEB only in all scales, indicating that the combination of the two stochastic perturbation schemes can efficiently complement the missing energy in different scales.

• Impacts of Vegetation on Vater and Heat Exchanges in the Source Region of Yellow River
• JIA Dongyu;WEN Jun;MA Yaoming;LIU Rong;WANG Xin;ZHOU Juan;CHEN Jinlei
• 2017 Vol. 36 (2): 424-435.  DOI:10.7522/j.issn.1000-0534.2016.00044
• Abstract ( ) HTML PDF (13756KB) ( )
• The land surface radiation budget and the impacts of vegetation on water and heat exchanges are the keys of land surface process.By using the field observed data at Maduo from 2013 to 2014, the characteristics of surface radiation budget were analyzed under different types of synoptic conditions.The results show that: (1) The different value of upward shortwave radiation is about 7.76 W·m^-2, between 100% vegetation covered and the control test.However, the different value of upward longwave radiation is only-0.62 W·m^-2.(2) The difference value of simulated longwave radiation between bare land and controlled test is about 5.34 W·m^-2.Moreover, the difference value between 100% vegetation covered and the control test is just-0.62 W·m^-2.(3) The decrease of LAI value has an influence on the increasing land surface albedo.Furthermore, the radiation flux and the surface turbulence flux change little.The upward shortwave radiation increases just about 1.35 W·m^-2.Meanwhile, the latent heat decreases about 8.43 W·m^-2.(4) On the other hand, the increasing LAI have an impact on the decrease of upward shortwave radiation and upward longwave radiation.What's more, the variation of radiation flux is larger when LAI increasing than LAI decreasing.(5) The radiation flux reveals obvious diurnal variation.The net radiation varies from 200 W·m^-2 to 461 W·m^-2 under different types of synoptic conditions.The soil heat flux at different depths reaches the peak from June to July in 2013.

• Observation Analysis and Numerical Simulation about a Heavy Rain in the Middle of Yellow River
• ZHAO Guixiang;BO Yanqing;QIU Guiqiang;ZHU Yu
• 2017 Vol. 36 (2): 436-454.  DOI:10.7522/j.issn.1000-0534.2016.00093
• Abstract ( ) HTML PDF (41628KB) ( )
• A heavy rain in the middle of Yellow River (Shanxi) on 9 July 2013 was analyzed through conventional observation data, FY-2E TBB, and ground encryption automatic weather station data. Evolution characteristics of shear line at low and near Mesoscale turbulence, dynamic and thermal structure characteristics, water characteristics, and nature and function of partial northeast air flow were analyzed by using output data of the high-resolution Weather Research and Forecasting (WRF) model. The results show that the heavy rain was directly caused by four Mesoscale convective cloud clusters aroused near shear line at 700 hPa. The occurrence and development of the Mesoscale convective cloud clusters were together triggered by the turbulent vortex formed near shear line at low, the ground Mesoscale dew front, and the ground Mesoscale convective line. The warm air overhead heavy rain area were forced uplift along northwest to southeast, so that form an inclined upward flow area along west cold air climbing affected by pinch of west and northeast cold air coming from low level. Two secondary circulations in the opposite direction were formed in two sides of inclined upward flow area. The convergence center of water was located near boundary layer. But it was not main reason causing heavy rain. The important reason of causing this heavy rain were that convergence ascending motion at low level was continued strength, water was collected to the heavy rain area by inflow of southerly winds, water was transported to high lever by ascending flow so causing the whole layer water of continued increasing over heavy rain area, and instability of vortex layer was strengthened due to symmetrical and convective instability were coexist. And under the background of strong instability, water was lifted along inclined upward flow, condensed, and falling by high efficiency way. The northeast airflow at low level was an interface of dry and cold air and warm. Various meteorological elements were uniform distribution on the interface. But in the center of the interface, it was a zero area of advection, vertical velocity, vorticity, and divergence at low level. There formed an anti-cyclonic secondary circulation around the northeast flow. There had a great vertical wind shear in two sides of the northeast flow. With it goes deep into Hetao area and Shanxi province, convergence of ascending flow at low level was continually strengthened. At the same time, subsidence became active. It was one of important triggering mechanism.

• Dominant Spatial Patterns of Summer Precipitation and Circulation Characteristic in the Middle of Northwest China
• SHEN Hongyan;CHEN Lijuan;HU Po;QIAO Shaobo;ZHANG Tiaofeng
• 2017 Vol. 36 (2): 455-467.  DOI:10.7522/j.issn.1000-0534.2016.00139
• Abstract ( ) HTML PDF (29470KB) ( )
• Based on the 55 stations data in the middle of Northwest China and NCEP/NCAR reanalysis dataset, the dominant modes of summer precipitation anomalies over the middle of Northwest China and corresponded circulation characteristic, water vapor transportation conditions were analyzed by diagnostic methods.There are three dominant EOF modes about summer rainfall.The first mode showed the same anomaly in whole region.The second showed an inverse pattern between the east and west.The third showed the opposite anomaly between the south and north.Further analysis were shown that the dominant precipitation EOF modes had different circulation and water vapor condition features.For EOF1 positive phase, the center of subtropical westerly wind was eastern to its normal position, Ural blocking high usually stronger than normal, water vapor transportation originates from Bay of Bengal, South China sea and west tropical Pacific.The water vapor convergence was significant in the middle of Northwest China.The EOF2 mode was connected with 'silk road' teleconnection pattern circulation.For the more rainfall in east and less in west pattern, the enhanced anticyclone circulation over central Asia provided strong cold air.And the anticyclone circulation anomaly in Northwest Pacific provided strong transport water vapor to the middle-west regions of China.A significant convergence was formed in the east part of Gansu province.The EOF3 mode was deeply affected by the middle-high geopotential height pattern.When rainfall anomaly was positive in south and negative in north, the circulation showed 'North-high and South-low' pattern over Eurasia.This mean a strengthened trough over Baikal which provides the strong westerly anomalies to the south of Baikal.At the same time, the vapor transformation originated from the Bay of Bengal, and further move to the east side of Tibet.A clear convergence formed in the southern of Qinghai province.From the above analysis, it showed significant differences about cold air conditions and the source of water vapor of the three dominant modes of summer precipitation in the middle of Northwest China.

• Comparison of Reanalysis Data and Observations about Summer Maximum Temperature on Different Time Scales in Eastern China
• ZHANG Ting;GAO Qingjiu;SUN Yuting
• 2017 Vol. 36 (2): 468-479.  DOI:10.7522/j.issn.1000-0534.2016.00030
• Abstract ( ) HTML PDF (10796KB) ( )
• Based on daily maximum temperature derived from the ground observation dataset of China meteorological data sharing network (OT) and JRA-55, ERA-Interim, NCEP/NCAR, NCEP/DOE reanalysis datasets, respectively, linear trend analysis, variance analysis, EOF analysis and filtering methods were used to compare multi-scale features of reanalysis and observation daily maximum temperature in summer during 19792013 in eastern China.Results show that: The average daily maximum temperature in summer during 1979-2013 decreased gradually from south to north and is above 30 ℃ to the south of the middle and lower reaches of the Yangtze River; The ability of reanalysis data to depict these characteristics from high to low is JRA-55, ERA-Interim, NCEP/DOE, NCEP/NCAR.In recent 35 years, the daily maximum temperature in summertime in the eastern region shows increasing trend, while the middle and lower reaches of the Yangtze river and eastern Inner Mongolia region shows obvious increase trend; The ability of reanalysis data to reproduce the characteristics in different regions have their own advantages and disadvantages, with JRA-55 slightly better than other datasets.The average daily maximum temperature in summer shows opposite distribution to the north and south of the middle and lower reaches of the Yangtze River, the distribution of ERA-Interim is very closely to the observations, then the NCEP/DOE.The temporal feature of summer maximum temperature is interannual variation, the ERA-Interim data is the one which interannual feature is most similar to the observations'.After 21st century, the temporal characteristics of JRA-55, NCEP/NCAR and NCEP/DOE is relatively similar to the observation data, showing the amplitude decreased and then picks up; The daily maximum temperature of summer main period is 20~60 days.The variance contribution of intra seasonal variability of the summer daily maximum temperature in Yunnan, Guizhou, Northeast China and the eastern Gansu, Shanxi area is larger.The reproduction ability of the 4 reanalysis for intra-seasonal variability from high to low is JRA-55, ERA-Interim, NCEP/DOE and NCEP/NCAR.

• Study of Atmospheric Low-Frequency System and Strong Precipitation Processes in Southern China
• CHEN Shenpeng;SUN Guowu;ZENG Dingwen
• 2017 Vol. 36 (2): 480-490.  DOI:10.7522/j.issn.1000-0534.2016.00006
• Abstract ( ) HTML PDF (12835KB) ( )
• Based on the NCEP/NCAR grid point data and precipitation data of southern China area, and the geographical location and mutual disposition of low-frequency system (low-frequency cyclones and anticyclones), the paper study and establish a low-frequency system based prediction model, which aim at heavy precipitation events of southern China area in extended-range (10~30 days) during flood season.The application of 2013-2014 flood season shows that the model can forecast heavy precipitation events of southern China area 10~30 days in advance.The model accurately forecasted the first heavy precipitation event of southern China in 2014 flood season, which is well reflected on low-frequency synoptic chart (LFSC).Synoptic and dynamic significance of weather systems on low-frequency synoptic chart and live weather chart is also analyzed, and it is pointed out that low-frequency system can reflect live weather system, the two are interrelated and reflects convergence of north and south airflow in the southern China, which therefor cause strong precipitation process, also the two are both associated with the conversion of baroclinic energy and activity of low frequency wavetrain.

• Interdecadal Variation Characteristics of Spring Rainfall and Its Intraseasonal Oscillation Intensity in South China
• LI Chunhui;PAN Weijuan;LI Xia;LIU Yan
• 2017 Vol. 36 (2): 491-500.  DOI:10.7522/j.issn.1000-0534.2016.00034
• Abstract ( ) HTML PDF (3949KB) ( )
• Based on the National Centers for Environmental Prediction (NCEP) reanalysis data and precipitation measured from 743 weather stations across China, the interdecadal variation characteristics of precipitation and its intraseasonal oscillation intensity in spring in South China are discussed.The results form EOF analysis show that the strong rainfall and rainfall intraseasonal variability intensity appear over the South China in the first modes.The correlation between the rainfall and its intraseasonal oscillation intensity is very high and significant.They experience obvious three period of decadal variability, namely that, dryer (weaker) in 19581973, wetter (stronger) in 1974-1990 and dryer (weaker) in 1991-2007.Moreover, the heavy rain and heavy rain intraseasonal oscillation intensity also take place fewer (weaker), more (stronger) and fewer (weaker) changes.But, the ratio between the heavy rain ISO and the total heavy rain event days and intensity shows the tendency of decrease.In different decadal time, atmospheric circulation and sea surface temperature (SST) anomaly on the variation of rain and rain intraseasonal oscillation intensity play a leading role, but the effect is different.In 1958-1973, surrounding SST, North Pacific decadal oscillation (PDO) and atmospheric circulation anomaly both play the main role.In 1974-1990, the main role is attributed to the PDO and atmospheric circulation anomaly.In 1991-2007, the PDO and atmospheric circulation anomaly suppress the influence of surrounding SST.

• Water Vapor Transportation Characteristics in Pre-rainy Season Precipitation anomaly of South China
• LI Ying;YUAN Wenjie;XU Qianqian;HU Runjie;LI Junli;MEI Xueying;LI Xiali
• 2017 Vol. 36 (2): 501-509.  DOI:10.7522/j.issn.1000-0534.2016.00031
• Abstract ( ) HTML PDF (4659KB) ( )
• Based on NCEP reanalysis data and daily precipitation data of 76 meteorological stations in South China from 1980 to 2011, using Lagrangian trajectory model (HYSPLIT_4), the water vapor transportation path, main sources and its contribution in frontal rainfall and monsoon rainfall anomalies during pre-rainy season in South China were studied. Results showed that: In frontal rainfall phase, water vapor path was mainly from Western Pacific, Arabia sea-Bay of Bengal and Continental Eurasian. In wet years of frontal rainfall, water vapor from the Western Pacific accounted for more than 69%, and the water vapor was 14% higher than that in dry years. While the contribution of water vapor from Arabia seaBay of Bengal was 20%, and the water vapor was 10% less than that in dry years. This stage was greatly influenced by the water vapor from the Pacific Northwest. In Monsoon rainfall phrase, water vapor was mainly from the cross-equatorial flow from north Indian Ocean, the Pacific Northwest wind airflow and the northwest cold air in Eurasia. In wet monsoon rainfall years, the water vapor from India ocean had the largest contribution 88%, the moisture from Indian ocean was 18% higher than that in dry years, while the moisture from the Western Pacific was 7%, the moisture from the Western Pacific was 15% less than that in dry years. This stage was greatly influenced by southwest cross-equatorial flow of water vapor transmission.

• Study of Numerical Model Stimulation of the Tropical Indian Ocean Basin Mode Impacts on May Precipitation Anomaly in East of Northwest China
• YANG Jianling;HU Haibo;MU Jianhua;WANG Min;HU Wendong
• 2017 Vol. 36 (2): 510-516.  DOI:10.7522/j.issn.1000-0534.2016.00036
• Abstract ( ) HTML PDF (5946KB) ( )
• Using fast ocean atmosphere model 1.5 (FOAM1.5), the numerical model stimulation of the tropical Indian Ocean Basin mode impacts on precipitation in east of northwest China in May are run and tested. The modeling precipitation and atmospheric circulation anomaly fields are basically similar to observational results, only with the anomaly system in East Asia a little eastward shifting. It is found that the tropical Indian Ocean SSTA warm Basin mode, being a heating source near the equator, can induce atmospheric circulation anomaly responses of the like "Matsuno-Gill Pattern". The atmospheric circulation anomaly appears to be an anomaly high center over southwest of Qinghai-Tibetan Plateau, and this anomaly further spreads downstream to forming a remote correlation wave train along the jet axis in the mid-high latitude of north hemisphere. With the altitude increasing, the atmospheric anomaly responses are more significant. The east of northwest China is just located under the anomaly circulation pattern of "east high and west low" of anomaly wave train over East Asia, with wind being strong anticyclone and divergence at high level and weak cyclone and convergence at low level. And accompanying with upward motion, it is advantage for more precipitation. Therefore, FOAM1.5 model experiment verified observational results of the tropical Indian Ocean SSTA impacts on precipitation of east of Northwest China basically.

• Variation of Haze and Its Relationship with Climate Change in Chengdu from 1980 to 2010
• JIA Jia;NI Changjian;HU Zeyong;XIE Jun;XIE Yuzhu
• 2017 Vol. 36 (2): 517-527.  DOI:10.7522/j.issn.1000-0534.2016.00077
• Abstract ( ) HTML PDF (1677KB) ( )
• In recent years, haze has become a serious problem in Chengdu area. Using surface observation data in Chengdu from 1980 to 2010 with two thresholds of relative humidity, this paper analysis the seasonal and inter-annual change of precipitation, relative humidity and average wind speed, and find the relationship between those meteorological elements with haze at the same time. The result shows the significant seasonal difference of haze when using two thresholds, it means the average number of haze days in winter is maximum among four seasons, while the haze days in summer is minimum. However, there is a significant difference between the two method when it comes to annual trend. Generally, the number of the haze days by using the old method shows a sharply increasing trend during recent years while the new one shows a weakly decreasing trend at the same time. It means the haze whose humidity is between 80% and 90% has been decreasing in recent year, and it may be related to the dry trend of atmospheric in Chengdu. The annual precipitation of Chengdu area shows a weak decreasing trend. When it comes to the relationship between haze and precipitation, using two threshold to calculate the correlation coefficient between precipitation and haze days in winter, the correlation coefficient are-0.559 and-0.534, respectively, and the remaining three seasons' precipitation is inversely related to the number of haze days, and their correlation coefficient are small. The relative humidity dropped to 80% since 1997, and the atmosphere shows dry trend. And two methods show the different relationship between the haze and relative humidity, the old one shows negative correlation and the correlation coefficient is-0.698, while the new one shows positive correlation. The frequency of calm in Chengdu area is high. The wind speed decreased significantly since 2005, and it is inversely related with haze days. In a word, the key point to the increased haze days is the dry trend of climate and the reduced wind speed.

• Characteristics of Carbonaceous Aerosols and Their Source in the Atmosphere during Summer in Lanzhou
• ZHANG Xueying;WANG Xin;ZHOU Yue;WEI Hailun;PU Wei;SHI Jinsen;DAI Mingkai
• 2017 Vol. 36 (2): 528-537.  DOI:10.7522/j.issn.1000-0534.2016.00103
• Abstract ( ) HTML PDF (4527KB) ( )
• Organic Carbon (OC), Blakc Carbon (BC), and Elemental Carbon (EC) are major kinds of carbonaceous particles depended on their measurement techniques. We collected 40 samples during summer in Lanzhou by two kinds of filters (nuclepore filters with 0.4 μm pore sizes and quartz fiber filters with 1 μm pore sizes), respectively. The concentrations of OC, EC were measured by the thermal/optical method using DRI-2001A carbon analyzer with the IMPROVE-A temperature protocol, while the BC concentrations were measured by the Integrating Sphere/Integrating Sandwich Spectrophotometer (ISSW). The results indicated that the concentrations of BC and EC were affected by the sampling efficiency and different measurement techniques. Actually, for each kind of filters, there were 20 samples in the daytime and nighttime, respectively. There was a large variation of the BC concentrations at night. The average concentration of OC in the daytime was (3.90±1.23) μg·m^-3, higher than that of (3.35±1.24) μg·m^-3 at nighttime, but for EC, (1.07±0.46) μg·m^-3 at daytime, lower than that of (1.59±0.68) μg·m^-3 at nighttime. Through the backward trajectories analysis, we found that the air with short transport distance, slower move speed and sinking motion would accumulate the pollutant. On the contrast, long transport distance and faster move speed were conducive to the spread of pollutants. The high value (greater than 2) of OC/EC indicated that the concentration of secondary organic carbon (SOC) was high, especially during the daytime in summer in Lanzhou. SOC made a major contribution to the mass of OC in the atmosphere with the concentration of (2.43±0.90) μg·m^-3 during the daytime, while in the nighttime the concentration of SOC was (1.16±0.73) μg·m^-3, they were about 62% and 35% of OC in the daytime and nighttime, respectively, which manifested that OC was dominated by primary sources at nighttime. In order to further determine the pollution sources, we separated EC into two categories (char and soot) based on different combustion temperatures. In fact, in the IMPROVE-A Thermal-Optical Reflectance (TOR) method, we had got OC1, OC2, OC3, OC4, OPC and EC1, EC2, EC3.From the previous studies, we could calculate the concentrations of char and soot (char=EC1-OPC; soot=EC2+EC3). By comparing the changes of char and soot concentrations, we found that the main pollution source was motor vehicle exhaust both at daytime and nighttime in summer, but the contribution of the biomass and coal combustion pollution increased and presented an increasing trend at nighttime.

• Research on Hail Disasters and Its Effects on Agricultural in Shaanxi Region for the Past 2000 Years
• WAN Honglian;SONG Hailong;ZHU Chanchan;ZHANG Mi
• 2017 Vol. 36 (2): 538-548.  DOI:10.7522/j.issn.1000-0534.2016.00104
• Abstract ( ) HTML PDF (5168KB) ( )
• By collecting and sorting the hail disasters of historical literature in Shaanxi region for the past 2000 years, and analyzing the spatial and temporal distribution characteristics of hail disasters and discusses its effects on regional agricultural by ArcGIS and Matlab software from different stages, seasons, influence degree, and so on. The results showed that there have occurred 1296 times of hail disasters in Shaanxi region during 0 to 2014 AD, approximately once every 1.55 years in average, hail disasters are given priority to with medium hailstorm, including elementary, secondary and special hailstorms occurred 315 times, 867 times and 867 times each other, respectively accounted for 24.3%, 66.9% and 24.3% of hail disasters in total. According to the change and development of instrumental observation instrument, hail disasters are divided into 3 stages on the times scale, including the year 0 to year 1911, the year 1912 to 1980 and the year 1980 to 2014, during the period when hail disasters respectively accounted for 375 times, 418 times and 503 times in Shaanxi region, on the whole, showing the decadal changes characteristic of hail disasters that less in early and much later in historical period of Shaanxi, hail disasters have obvious seasonal variation characteristics and present prominently monthly difference which within the year, and in each stage, characteristics of hail disasters in the seasonal and monthly are related to the occurrence with past 2000 years of Shaanxi. Hail disaster exists in 11 years and 16 years two period of oscillation on time scale, which has relationship with sunspot activity cycle. There are obvious different in the spatial distribution of hail disaster where the characteristics of the northern are more than the southern. With the influence of different seasons and different degrees, the effects of hail disasters on agricultural production in Shanxi Province are different, the distributions are mainly in the Guanzhong plain and north of the region. Since the 20th century, regional human activity way and strength has changed, the centralization of the population, social economy and agricultural production in the area increased agricultural level of disasters of local areas.

• Analysis of Two Cases of Extremely Severe Snowstorms in Northeast China
• SUN Yanhui;LI Zechun;SHOU Shaowen
• 2017 Vol. 36 (2): 549-561.  DOI:10.7522/j.issn.1000-0534.2017.00012
• Abstract ( ) HTML PDF (12621KB) ( )
• Based on data from observations, NCEP/NCAR reanalysis and the WRF simulations, two cases of intense snowstorms with blizzard conditions on 29 April 1983 and on 4 March 2007 in northeast China are investigated, in order to discuss the features of the environment conditions of these violent and persistent snowstorms which occurred over wild areas, and try to make accurate where and when it would occur. Results show, these snowstorms produced by the extensively deepened cyclones, which developed under the left side of the exit region of the southern jet and the right side of the entrance region of the northern jet at 300 hPa level, with the central cyclone sea level pressure drop rates of 1.2 hPa·h^-1 (observation) and 0.71 hPa·h^-1 (model grids) respectively. Wind shears in the troposphere are very remarkable, wind direction changed in clockwise with height, wind velocity increased with height, there exist an equally velocity layer from 4.5 to 8 km. Airflow divergent in the upper troposphere and convergent in the lower layer, updrafts developed due to the warmer air inflow and pumping caused by the divergence in the upper layer. Heavy snowfall and severe winds occurred at the northern and western parts of the cyclone, 10 min mean northerly surface winds greater than 20.8 m·s^-1 occurred about 110 km away northwest of the central cyclone, with a snowfall rate of 20~35 mm·(12h)^-1 (liquid water). The surface winds velocity and the snowfall accumulation increased to their highest values rapidly during the period of the sea level pressure dropped most quickly. A mesoscale warm and moist jet closed to the surface was formed at about 300 km away southeast of the central cyclone. Heavy snowfall accompanied by less severe winds of about 10.8~17.2 m·s^-1 also presented within areas of 3~5 latitudes away from the cyclone in the northern part, surface winds velocity of most stations derived their maximize values just after the snowfall terminated. The 3D VAPOR visualization of the velocity from the GRIB grids and the WRF simulations show, severe surface winds are connected to the airflow among the two upper-level jets, suggesting that the surface winds energy originated from the upper troposphere aloft.

• Interaction of Anthropogenic Heat Emission from Building Cooling System and Meteorological Environment
• ZHENG Yulan;MIAO Shiguang;BAO Yunxuan;LIU Ke
• 2017 Vol. 36 (2): 562-574.  DOI:10.7522/j.issn.1000-0534.2016.00005
• Abstract ( ) HTML PDF (20160KB) ( )
• Since the accelerating of urbanization in China, in this paper the BEM (building energy model) is improved and used to study the interaction of the anthropogenic heat release from cooling system and the urban meteorological environment. Based on the case of May 29 to 30 in 2014 (extreme high temperature case in the Beijing area in summer), this paper begin to quantitative analyze above interaction. The online WRF/Noah/SLUCM/BEM results showed that, without the anthropogenic heat summer night heat island in Beijing urban areas has a deviation at night, and can hardly simulate summer heat island in the daytime. WRF model with anthropogenic heat can improve the extent and the intensity of urban heat island, which means the result can be more correct. The considering of building anthropogenic heat in WRF model would improve the simulation of temperature and specific humidity at 2 meters, upward sensible heat flux, latent flux and the upward moisture flux at the surface, and the urban boundary layer height. In case2 which adding BEM anthropogenic heat, the sensitive heat flux of downtown area increase by 30~50 W·m^-2, while the 2 meters temperature at relevant area rose about 0.4~0.6 ℃, which is almost the same. The latent release in case2 result that the latent heat flux near the surface, the moisture flux, and the specific humidity of downtown area increased nearly 80~140 W·m^-2, 0.04~0.09 g·m^-2s^-1, 0.5~0.9 g·kg^-1 respectively. In addition, the planetary boundary layer height rose about 100~150 m, and the time of beginning falling got later about 1 hour. The change of meteorological condition caused by the additional building anthropogenic heat made effect on the building anthropogenic heat too. Compared to case1, the consumption of energy for case2 increased 1.11%~3.33%, the released heat from building can split into two part: sensitive heat flux and latent flux. The former increased 0.67%~1.67%, the later increased 0.625%~1.56%(which can reach above 2.0 W·m^-2). This study shows that coupling with the heat release of building to WRF can improve the simulation effect of meteorological elements in the surface layer.

• Assessing the Performance of Domestic Optical Large Aperture Scintillometer under Different Environment Conditions
• LI Huaixiang;LIU Shaomin;SHI Shengjin;XU Ziwei;ZHU Zhongli
• 2017 Vol. 36 (2): 575-585.  DOI:10.7522/j.issn.1000-0534.2016.00035
• Abstract ( ) HTML PDF (10481KB) ( )
• The accuracy, stability and consistency of domestic optical large aperture scintillometers (YZLAS) were assessed using the observation experiments located in Miyun, A'rou, Jiyuan, Zhangye, Guantao and Guyuan in China during 2009 to 2012.The results can provide a potential scientific basis to improve and produce the subsequent domestic optical large aperture scintillometer. The results showed that: (1) Taken BLS900 scintillometer as the reference, the domestic large aperture scintillometer derived very similar sensible heat fluxes with the reference, with the averaged RMSE of 19.91 W·m^-2 and 9.81 W·m^-2, respectively at Zhangye Baji site (three YZLAS sets) and Guyuan site (five YZLAS sets). The RMSE of YZLAS sets were 21.08 W·m^-2and 12.87 W·m^-2, respectively, when compared with the measurements from eddy covariance system. These comparisons indicated that the domestic large aperture scintillometer performed very well; (2) The domestic large aperture scintillometer also has reliable stability under harsh environments such as high and low temperature, high and low humidity conditions; (3) The sensible heat fluxes measured by YZLAS also showed good consistency with each other with diversity of about 6% and the correlation coefficient greater than 0.98.These mean that the domestic optical large aperture scintillometer basically reached the level of the foreign instrument.