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28 August 2017, Volume 36 Issue 4   
  • Study on Turbulence Characteristics in the Atmospheric Surface Layer over Nyainrong Grassland in Central Qinghai-Tibetan Plateau
  • YANG Liwei;GAO Xiaoqing;HUI Xiaoying;GAO Na;ZHOU Ya;HOU Xuhong
  • 2017 Vol. 36 (4): 875-885.  DOI:10.7522/j.issn.1000-0534.2016.00089
  • Abstract ( ) HTML PDF (700KB) ( )
  • Turbulence is the basic characteristic of atmospheric motion and main way of matter and energy exchange between land and air. Based on the turbulence data observed at Nyainrong station, central part of Qinghai-Tibetan Plateau, from 18 July to 31 August 2014, the variation of turbulent statistical parameters and the energy exchange near surface layer were analyzed. The results show that the relationship between the normalized standard deviation of wind velocity components σu/u*, σv/u*, σw/u* and stability parameter z/L satisfies the "1/3" power law in stable/unstable stratifications. Under the near-neutral stratification condition, normalized standard deviations are approximately constant, and σu/u*σv/u* >σw/u*. The relationship between the normalized standard deviations of temperature, humidity and CO2 concentration σT/|T*|, σq/|q*|, σC/|C*|and stability parameter|z/L|satisfies the "-1/3" power law under unstable conditions. Under the near-neutral condition, normalized standard deviations are approximately constant, they are significantly greater than those in other regions of the Qinghai-Tibetan Plateau. When the wind speed is 0 m·s-1 < U < 3 m·s-1, the development of turbulence is much vigorous. The performance of the turbulence intensity in the three directions is Iu≈Iv > Iw. The diurnal variations of surface fluxes are evident, and latent heat flux is larger than the sensible heat flux in the summer.
  • Discussion of Plateau Monsoon Index and Its Impact on Precipitation in Sichuan Basin in Midsummer
  • PANG Yishu;MA Zhenfeng;YANG Shuqun;YANG Xiaobo
  • 2017 Vol. 36 (4): 886-899.  DOI:10.7522/j.issn.1000-0534.2016.00027
  • Abstract ( ) HTML PDF (1684KB) ( )
  • A new Qinghai-Tibetan plateau monsoon index was built on the basis of synthetically consideration of the wind and height field variation on Qinghai-Tibetan plateau. After comparing with other indices by statistical methods such as correlation coefficient and wavelet analysis, the new index showed good response to the heat inter-annual variation of Qinghai-Tibetan plateau, and reflected the midsummer height and wind field of Tibetan plateau in a better way. On this base, the relationship between Qinghai-Tibetan plateau monsoon and precipitation of Sichuan Basin in midsummer was analyzed. The results showed that in midsummer, the strengthening of the plateau monsoon led the height over the Bay of Bengal-India strengthened, West Pacific Subtropical High, Ural Blocking High and Northeast Asia Blocking High abnormally enhanced, and the East Asia/Pacific (EAP) teleconnection pattern being "+-+". In the lower troposphere, warm water air was transported from the Arabia sea, the bay of Bengal and the South China Sea to South China by anticyclones circulation around the Indian-Bengal high and West Pacific Subtropical High. On the other side, Northerly airflow between Ural Blocking High and Northeast Asia Blocking High, and northeast airflow over Northeast China brought cold air southward. The warm and cold air met in Sichuan Basin, the convergence and uplifting motion of water vapor led the increasing of local precipitation.
  • Quantitative Study on Water Vapor Pumping over Qinghai-Tibetan Plateau and Water Vapor Paths Influencing Summer Precipitation in the Middle and Lower Reach of the Yangtze River
  • JING Wenqi;CUI Yuanyuan;LIU Ruixia;WANG Yegui;FANG Hanxian;ZHAO Xiaoyan;MA Jie
  • 2017 Vol. 36 (4): 900-911.  DOI:10.7522/j.issn.1000-0534.2016.00084
  • Abstract ( ) HTML PDF (1039KB) ( )
  • Based on JICA Tibetan sounding data in 2008, ERA-Interim and MERRA reanalysis data during 1979-2015 and monthly average precipitation of 160 stations in China, firstly this study evaluates the applicability of two reanalysis data on Qinghai-Tibetan Plateau (QTP) and defines the high-level and low-level difference of water vapor flux divergence on QTP as QTP water vapor pumping index; By synthetic analysis, it is found that there are mainly five water vapor paths influencing summer precipitation in middle and lower reach of Yangtze River (MLRYR):The Bay of Bengal path, Yunnan-Guizhou Plateau path, South China Sea path, low latitude path and confluent water vapor path, whose magnitude is calculated by index. The result shows that ERA-Interim reanalysis data shows better applicability than MERRA reanalysis data on QTP. On the inter-annual variability, all the water vapor paths perform the same phase change with MLRYR summer rainfall. Five paths are closely related, making up two anticyclonic water vapor transport correlation-chains:One is "South China Sea-the Bay of Bengal-southern edge of QTP-Yunnan-GuiZhou Plateau-MLRYR", the other is "South China Sea-Yunnan-Guizhou Plateau-MLRYR". South China Sea path is important water vapor channel of the rainfall in east China; Confluent path is the vital water vapor channel controlling the summer rainfall in MLRYR, but Yunnan-Guizhou Plateau path shows significant correlation with the summer rainfall in whole reach of Yangtze River. QTP water vapor pumping, which effects summer rainfall in MLRYR, mainly occurs over southern edge of QTP. QTP water vapor pumping can pump up water vapor in lower level to the top of QTP, and plays an indirect role in influencing the summer rainfall in Yangtze River by increasing zonal water vapor transport towards the Yangtze River Basin.
  • The Impact of ATMS and CrIS Data Assimilation on Weather Forecasts over the Qinghai-Tibetan Plateau
  • XUE Tong;GUAN Zhaoyong;XU Jianjun;SHAO Min
  • 2017 Vol. 36 (4): 912-929.  DOI:10.7522/j.issn.1000-0534.2016.00087
  • Abstract ( ) HTML PDF (2703KB) ( )
  • The impact of ATMS and CrIS data assimilation on weather forecasts over the Qinghai-Tibetan Plateau investigated by using NOAA's Gridpoint Statistical Interpolation (GSI) data assimilation system and NCAR's Advanced Research Weather Research and Forecasting (ARW-WRF) regional model. The experiment was designed with 4 parts:A control experiment (CTRL) and three data assimilation experiments with different data sets, including conventional data only (CONV), a combination of conventional and ATMS satellite data (ATMS), and a combination of conventional and CrIS satellite data (CRIS). The 2 m temperature (T), 2 m relative humidity (RH) and 10 m wind speed (WS) in January and July 2015 were evaluated to investigate the weather forecast ability. Furthermore, those variables in different vertical layers over the terrain were also analyzed to improve the forecast results. The simulation results showed that the improvement of three data assimilation experiments was not general. The forecast ability of 10 m WS in January and the 2 m RH in July could be modified by assimilating ATMS over high-elevation region, while 2 m T prognosis could be rectified over low-elevation region. CRIS showed a good performance over high-elevation region for 24 h 2 m T prediction in July. Meanwhile, CRIS could also improve the prediction accuracy of 10 m WS over high-elevation region in both January and July. Considering the vertical stratification, the CRIS data assimilation had a negative contribution in all vertical layers while ATMS data assimilation had different forecast accuracy in different vertical layers and variables. The forecast error in T was typically caused by the systematic error, which was controlled by the physical representation within the model. In contrast, the inaccuracies in the RH and WS forecasts were dominated by nonsystematic errors, derived from the random inadequacies of the initial conditions. In summary, the overall improvement of ATMS data assimilation over the Qinghai-Tibetan Plateau is better than the improvement of CRIS data assimilation.
  • Development of Hourly Wind Speed Dataset in China and Application on Qinghai-Tibetan Plateau
  • ZHAO Yufei;ZHANG Qiang;YU Yu;YANG Gui
  • 2017 Vol. 36 (4): 930-938.  DOI:10.7522/j.issn.1000-0534.2017.00001
  • Abstract ( ) HTML PDF (736KB) ( )
  • Station observation data is fundamental to data processing and climate analysis. Wind is the horizontal movement of air relative to the ground, and is the main item of ground meteorological observation. Based on wind recording observation data files of more than 2400 stations and hourly wind speed data of automatic stations which started from 2001, integration resulted in the formation of the hourly wind speed series. According to the information characteristics of wind speed data, the quality control is developed based on the hourly wind speed data in China. In 1950s, only a small part of the ground observation stations carried on wind observations, mainly distributed in Northeast China, North China, south of the Yangtze River and so on. The number of wind station increased rapidly after 1970s, gradually close to that of the ground observation station. After 2004, all ground stations realized the hourly observation of wind. By the analysis, the missing measure rate of 76.3% stations was less than 7% in China. Since the beginning of the automatic observation in 2005, the correct rate was higher than 95%. Suspicious rate was highest in 1969 and 1970, respectively, 0.21% and 0.18%. The error rate was higher in 1991, 1998, 1997 and 2004, which were 0.013%, 0.005%, 0.001% and 0.001%, respectively. By using the hourly wind speed dataset, the diurnal variation of wind speed in the Qinghai-Tibetan Plateau was analyzed, the result shows that the maximum wind speed and the average hourly wind speed in spring is higher than the other three seasons. The maximum hourly wind speed in the western Qinghai-Tibetan Plateau is 2 hours earlier than that in the eastern region, and the hourly wind speed in the eastern region is larger than that in the western region. In the eastern (western) part of the Qinghai-Tibetan Plateau, the maximum velocity reaches on local time of 16:00 (14:00), and the minimum wind speed on local time of 06:00 (06:00). In the eastern region, the wind speed on local time of 16:00 is significantly greater than that in the western region on 14:00, the wind speed is 3.75 m·s-1 and 2.90 m·s-1, respectively. In the spring of 1995-2015, both the eastern peak wind and the average wind speed series show significant trends of decreasing (pass the test of significance of 0.01), but there is no significant trend of peak wind speed and mean wind speed series in Western Qinghai-Tibetan Plateau.
  • A Forecast Analysis of Precipitation Phase Transformation and Rainfall Intensity in Spring over Northern Xinjiang
  • ZHANG Junlan;PENG Jun
  • 2017 Vol. 36 (4): 939-949.  DOI:10.7522/j.issn.1000-0534.2016.00094
  • Abstract ( ) HTML PDF (1150KB) ( )
  • A large-scale rain followed by snow and heavy snow process happened in northern Xinjiang from 13 to 15 April 2014, which has brought serious impact on local agricultural, works and people's life. Using the diagnosis method of the weather, the forecast index of phase transformation between rain and snow as well as rainfall intensity was studied. The result shows:(1) Change of temperature at middle-low level is the key factor and index to Forecast precipitation phase transformation in spring in Northern Xinjiang. (2) Temperature at the middle level is a key factor to distinguish between the snow and sleet. Sleet turning to snow when the temperature is less than -25℃ on 500 hPa and less than -12℃ on 700 hPa; Temperature at the low level can distinguish between the rain and sleet, rain turning to sleet in the case of the temperature less than -2℃ on 850 hPa and less than 2℃ on 925 hPa. Additionlly, the forecast index of sleet turning to snow when the temperature is less than -4.5℃ on 850 hPa. (3) Cooling condensation of water vapor plays an important role on precipitation process in spring over the northern edge of the Northern Xinjiang and the Tianshan mountainous. Cooling condensation of the lower water vapor is an important factor affecting the rainfall intensity. There are more water vapor、stronger cold air、thicker condensation which can induce longer and stronger rainfall. The rainfall intensity is decided by the cooling condensation of water vapor.
  • Spatial-Temporal Validation of TRMM 3B42V7 Precipitation Products and Analysis of Precipitation Characteristics in the Upper Reaches of Nujiang River
  • LI Meng;QIN Tianling;LIU Shaohua;LU Yajing
  • 2017 Vol. 36 (4): 950-959.  DOI:10.7522/j.issn.1000-0534.2016.00071
  • Abstract ( ) HTML PDF (779KB) ( )
  • The Nujiang river is a typical area of lacking data with complicated terrain and climate characteristics. TRMM (Tropical Rainfall Measuring Mission) precipitation data can effectively describe the spatial distribution characteristics of regional precipitation, and it has great reference value to the area of lacking information. We use TRMM 3B42V7 data and 18 weather stations data to explore the spatial and temporal distribution characteristics of precipitation and analyze the accuracy of TRMM 3B42V7 data in the upper reaches of Nujiang river. The correlation coefficient method and spatial analysis method are used to solve the problem. By analyzing the correlation coefficient, it shows that the best correlation coefficient between TRMM 3B42V7 data and the site observation data occurs at monthly scale (R>0. 9), second is yearly scale (R>0. 5), the worst is daily scale (R < 0. 5). The two sets of data have strong correlation under monthly scale when it comes to areal precipitation (R≈0. 98). Time series also fit well though TRMM 3B42V7 data is slightly larger than the site observation data in the month of abundant precipitation. Spatial-temporal comparative analysis indicates that precipitation spatial distribution has good consistency of these two group data at different time scales though the local distribution characteristics are different. There is an underestimation tendency of TRMM 3B42V7 data in the northwest of the basin, and overestimation tendency in the southeast. Precipitation in most other area has little difference between TRMM 3B42V7 data and the site observation data. TRMM 3B42V7 data is also used to analyze the seasonal proportion of precipitation in the basin and it is found that seasonal patterns of precipitation in study area vary greatly. Precipitation in summer (from June to August) account for a large proportion of total annual precipitation. The ratio of precipitation in summer is 42%~72%, while the total ratios of spring (from March to May), autumn (from September to November) and winter (from December to February) to annual precipitation are 28%~58%.
  • Analysis of Water Vapor Transport Characteristics of Typical Rainstorm Cases in Northeast China
  • MA Liangchen;SUN Li;WANG Ning
  • 2017 Vol. 36 (4): 960-970.  DOI:10.7522/j.issn.1000-0534.2016.00078
  • Abstract ( ) HTML PDF (802KB) ( )
  • Using the NCEP GDAS (1°×1°) data and the airflow trajectory model based on the Lagrangian method (HYSPLIT_4.9), the cold vortex rainstorm case from June 27 to July 1 in 2009, the shear rainstorm case from August 19 to 22 in 2010, the cyclone rainstorm case from August 14 to 17 in 2013 and the typhoon rainstorm case from August 27 to 30 in 2012 were selected in Northeast China. The variation features of the water vapor transport passages and the contribution rate of water vapor from different sources of these four rainstorms were simulating calculated. Results show that there are basically two water vapor transport channels in the four rainstorm cases, one comes from South China Sea or the western Pacific, the other is the northwest flow. The characteristics of typical rainstorms in different weather systems are different. In the case of cold vortex, 42.1% of the water vapor contribution comes from the western Pacific and the South China Sea, and the water vapor near the Okhotsk Sea is also supplemented. The northwest airflow and the sea water vapor account for about 50%. The heavy rain of shear is similar with cyclone. The West Pacific and South China Sea passages of water vapor transportation account for the main part and the decreasing proportion of water vapor is from northwest. In the case of shear rainstorm, a small percentage comes from local areas. In the typhoon rainstorm, the main source of water vapor is from North Pacific, Yellow Sea and Bohai Sea. The magnitude and distribution of precipitation are closely related to the contribution rate of sea water vapor.
  • Comparison and Application of Two Kinds Vertical Wind Profile Data Part Ⅱ:The Characteristics of Wind Profiles under Different Weather Conditions Related to Rainfall
  • FANG Dexian;DONG Xinning;ZHOU Guobing;WU Zheng;ZHANG Yong;HUANG Anning
  • 2017 Vol. 36 (4): 971-983.  DOI:10.7522/j.issn.1000-0534.2016.00091
  • Abstract ( ) HTML PDF (2100KB) ( )
  • Based on the wind vertical profiles observed by Doppler radar (SA) and wind profiler radar (TWP8-L) in Chongqing, China during 2013, this study explored the characteristics and evolutions of wind profiles under four different weather conditions related to rainfall (i. e., clear sky, light rainfall, moderate rainfall and heavy rainfall). Our analyses found that:(1) Under the weather condition of clear sky or light rainfall, the moisture condition is so weak that the wind vertical profiles observed by Doppler radar are mostly identified as "ND" (No Data) and wind speeds (directions) observed by wind profiler radar are weak (ill-organized). Meanwhile, the observed vertical wind shears are weak and ill-organized as well, inhibiting the development and sustenance of convection systems; (2) Under the weather condition of moderate rainfall, precipitations are well distributed over regions, and hourly accumulated precipitation amount is little. In terms of the wind vertical profiles, the low-middle winds are ill organized, while a uniformsouthwest by west jet is evident at the middle-high levels. Also, the wind vector maps are featured by a good unidirection in the vertical wind shears. All these processes favor the development and sustenance of convection systems; (3) Under the weather condition of heavy rainfall, the wind vertical profiles present good consistency between observations by Doppler radar and wind profiler radar. In particular, during the pre-precipitation period, wind changes gradually from easterlies at the low level to westerlies at the high level, which favors triggering convections. During the precipitation period, especially when the rain (convection) is the heaviest (most intense), the vertical wind shears are featured by a good unidirection and low-level jets are present at the low-middle levels, both favoring the sustenance of convection systems. During the post-precipitation period, the winds become weak, northerlies are gradually present at the low-middle levels, and convection systems start to decay, which contribute to the end of precipitation.
  • Diagnostic Analysis of a Historical Extreme Snow Process in South of Shandong Province
  • HU Shunqi;CAO Zhangchi;CHEN Tao
  • 2017 Vol. 36 (4): 984-992.  DOI:10.7522/j.issn.1000-0534.2016.00134
  • Abstract ( ) HTML PDF (1077KB) ( )
  • For a more comprehensive understanding to the influence mechanism of the occurrence and development of historical extreme snow process in south of Shandong province, the cause and the dynamic structure on a snowstorm event occurred in south of Shandong Province from 23 to 24 November 2015 was investigated by the dynamic diagnosis with the routine sounding and surface observation data, OLR data of FY-2E satellite, NCEP/NCAR 1°×1° reanalysis data. The results show that:(1) Under the return-flow situation, the abnormal snowstorm occurred by the combined effect of the strong low-level southwest jet, shear line and northeast jet stream in the mid-troposphere. (2) The transfer of water vapor to southern Shandong via southwest low-level jet which also produced intense convergence center just above the sensitive area provided favorable water-vapor conditions for the occurrence of snowstorm. (3) The upper-level and the low-level jets were coupled. The positive vorticity advection in front of the trough lessened the pressure from low-level which caused its upward movement. It was conductive to the occurrence and development of snowstorm. (4) The southwest low-level jet and northerly winds had a convergence just over the southern area of Shandong. This was the main reason why the heavy snowfall concentrated in this region. (5) It was the strong cold air that made the rain turn to snow instantly, which also made the snow have a long duration. The above two reasons accounted for the occurrence of the extreme snowstorm. (6) The OLR analysis showed that the 3 hours average minimum center of OLR was closely related to the 3 hours maximum center of snowfall. The study on the characteristics of historical extreme snow process in south of Shandong province contributes to prediction ability of severe weather in the region, and is of tremendous importance to the disaster control and reduction.
  • Study of Temporal-Spatial Distribution and Variation Characteristics of Thunderstorm Gales in Hunan
  • XU Lin;YAO Rong;WANG Xiaolei;OU Xiaofeng
  • 2017 Vol. 36 (4): 993-1000.  DOI:10.7522/j.issn.1000-0534.2016.00088
  • Abstract ( ) HTML PDF (716KB) ( )
  • The climate characteristics of the thunderstorm gales and its possible cause were analyzed with the data of thunderstorm gales in Hunan province from 1971 to 2010 using the climate slope, Mann-Kendall test, wavelet analysis and correlation analysis. Moreover, the paper compared and analyzed the parameters in different stations based on the NECP reanalysis data from 2001 to 2010. It's meaningful to understand the formation mechanism of thunderstorm gale in Hunan. The results show that the overall amount of thunderstorm gales was decreasing continuously in Hunan over the last four decades, and the thunderstorm gales decreased significantly, especially after the 1990s. Thunderstorm gales mainly occurred appeared primarily in the afternoon to evening in summer, and there was an abrupt change of its occurrences in 1990. It was found that there existed short oscillating periods (2~3, 3~5 and 6~7 years) and long periods (11~12 years) in the occurrence of thunderstorm gales by using the wavelet analysis, besides, the short oscillating periods of 2~3, 3~5 years were the main characters. Furthermore, the differences of thermal instability in different regions were analyzed, the result indicated that the west area was higher than east in Hunan. The differences of the dynamic instability suggests that the south area is higher than north in Hunan. The characteristic of upper and lower water vapor difference demonstrates that mountain area is higher than lake area.
  • Analysis of Characters of Wind Field in Surface Layer in Lanzhou New District
  • LI Xiaoxia;HUANG Tao;WANG Xing;LIANG Dongsheng
  • 2017 Vol. 36 (4): 1001-1009.  DOI:10.7522/j.issn.1000-0534.2016.00092
  • Abstract ( ) HTML PDF (871KB) ( )
  • This paper used wind direction and speed data collected at four anemometer towers (70 meters) from Qinchuan-Jinjiamao, Xicha-Duanjiachuan, Heishichuan-Heping and the southeast of Lanzhou New District, and other four high AWS (Automatic Weather Station) (10 meters) at the new district from January to December 2014, to analyze the area's prevailing wind direction, speed, characteristics and distributions of air pollution. The reselts showed:The new district exhibited complex geographic variations; Prevailing wind direction, speed, and air pollution index (API) changed depending on altitude, time, and location. During the period of 2014, the new district anemometer towers (70 meters) observed a dominant frequency of northeastern prevailing wind, a direction with the highest average wind speed; As for API, it was the lowest between Qinchuan-Jinjiamiao and Xicha-Duanjiachuan at the west by north, and the lowest API between the southeast of Lanzhou New District and Heishichuan-Heping is at the north and the near directions. Furthermore, the prevailing wind direction, speed and API had some differences between the 10 meters towers and the 70 meters towers. The wind fields also changed among the four towers. Calm wind weather occurred at each observation point. The Frequency for calm wind was 4. 2%~13. 5% at 70 meters, and 5. 6%~11. 6% at 10 meters; Each tower had distinct seasonal differences; Autumn and winter shared a similar prevailing wind direction, and spring and summer shared a similarity at another direction. The daily wind changes at the new district also displayed characteristics of valley wind, with a southeast or southwest prevailing wind in the day, and a northeast or east wind at night.
  • The Impact of Meridional Wave Trains over East Asia on the Air Temperature over Central and East China in Midsummer Time
  • ZHANG Yinghua;LI Yan;LI Deshuai
  • 2017 Vol. 36 (4): 1010-1021.  DOI:10.7522/j.issn.1000-0534.2016.00080
  • Abstract ( ) HTML PDF (1121KB) ( )
  • Based on the CN05 grid datasets of monthly mean surface air temperature from 1980 to 2008, the distribution of surface air temperature over Central and East China in July is studied, and three main modes are obtained, the three leading modes explained 44%, 17% and 11% of the total variance, respectively. The first mode shows a linear trend of surface air temperature over Jianghuai area in the North China and Northeast China in the last thirty years, the second mode shows a 'dipole'pattern between Jianghuai-Jiangnan area and the east portion of Northeast China, and the third mode shows a 'tripole'pattern between Huabei-Huanghuai area, the South China and the Northeast China. Because of the characteristics of the first mode have been discussed in a number of articles, the second and third modes account for the main component. The composite fields indicate that the meridional wave trains over East Asia play an important role on the second and third modes:When the meridional wave trains over East Asia and Western Pacific locate north, it's in favor of generating the above dipole pattern. When the wave trains locate south, it's in favor of generating the above tripole pattern. When the convective activities over South China and Taiwan Island is weaker than normal, it's favorable to generate the negative phase of the meridional wave trains corresponding to the second mode, and vice versa. In the composite fields of positive and negative years about the second mode, wave activity flux mainly point to north at low latitudes at the 850 hPa level near East Asian coast. At 300 hPa level, wave activity flux mainly point to north at low latitudes and point to east at middle latitudes. However, OLR and wave activity flux anamolies at low latitudes in the third mode are not significant.
  • Application Research on the Multi-Model Fusion Forecast of Wind Speed
  • SHI Lan;XU Lina;HAO Yuzhu
  • 2017 Vol. 36 (4): 1022-1028.  DOI:10.7522/j.issn.1000-0534.2017.00021
  • Abstract ( ) HTML PDF (571KB) ( )
  • Using ECMWF (European Centre for Medium-Range Weather Forecasts) 100 meters wind speed ensemble forecast products and professional numerical model products on wind power, after the comparative test and analysis, designing a fusion forecast product of wind speed including the single value forecast and the wind speed variation zone in the studied wind farm, which is suitable for short term wind power prediction and electric dispatch. In the paper, the value of ensemble, maximum, minimum, and temporal and spatial distribution are analyzed according to multi statistic fusion, and then the probability information of extremely strong, weak and transition fluctuation of wind speed is researched and extracted using probability distribution function and ensemble technique, the most probable positions of the wind speeds fluctuation are pointed out, the magnitude deviation of the ensemble forecast products is calibrated by probability matching technique. The members of Bayesian probabilistic forecasting are attempted to fuse, thus the fused Bayesian probabilistic forecast representing the uncertainty of ECMWF ensemble forecast is obtained, the single value forecast is formed by calculating the different ensemble statistics at last. Using ARIMA(Autoregressive Integrated Moving Average Model) method to improve the time resolution of the forecast, and based on the BMA(Bayesian model averaging) method and fusion with the deterministic numerical model forecast, the optimal wind speed forecast curve and the wind speed variation zone is produced. The study shows that the BMA method is applied to the short-term wind power forecast and the dynamic fusion prediction model can reduce the forecast error effectively, the fusion forecast has obvious improvement on the accuracy than the ECMWF ensemble forecast and the existing numerical forecast products. Comparison between the validation period and the existing deterministic forecast, MAE decreased by 24. 3%, and the correlation coefficient (R) was increased 12. 5%. Compared with the ECMWF ensemble forecast, the MAE was reduced by 11. 7%, and the R was increased 14. 5%. In addition, the wind speed variation zone of the fusion forecast can capture the fluctuation of wind speed effectively and further reduce the risk on the electric dispatching plan and the wind farm operation decision caused by the single power prediction. The fusion of the existing numerical forecast products, is an effective way to improve the forecast accuracy of province whose computing resources are limited. Less number of study area selected and the study period is short in this study, more wind farms will be selected, and multi model ensemble forecast products will be fused next step. This method will be refined in order to promote and apply in all wind farms serviced.
  • Study on Estimation of Photosynthetically Active Radiation under Complicated Topography by Remote Sensing
  • NIU Xiaojun;FENG Wenlan;WANG Yongqian;HUANG Yuqian;ZENG Lin
  • 2017 Vol. 36 (4): 1029-1038.  DOI:10.7522/j.issn.1000-0534.2016.00066
  • Abstract ( ) HTML PDF (584KB) ( )
  • The photosynthetically active radiation (PAR) is one of the important input parameters in different terrestrial ecosystem models. The estimates of PAR by satellite remote sensing data are beneficial to strengthening continuity and diversity of spatial information. There are uncertainties in the parameters estimated by remote sensing under the complex terrain conditions, meanwhile, the instantaneous PAR estimated by remote sensing is unable to satisfy the requirements in practical application. Therefore, a remote sensing estimation model was developed in this paper to estimate PAR under complicated topography and exemplified in the upper Min River Basin. The instantaneous PAR was estimated based on a simplified atmosphere radiation transfer model and MODIS standard atmospheric products. Then the estimates results were corrected by comprehensive considering variation of incident angle of solar radiation, terrain masking and the effect of radiation enhancement caused by adjacent terrain under the complicated topography. The daily PAR was obtained by linear interpolation algorithm. The instantaneous PAR of the upper Min River Basin on the 22 sunny days in 2013 were estimated. Comparisons of satellite-based and field-based of Maoxian station estimates indicated the average errors of the instantaneous PAR were 7. 26%, the daily PAR were also 7.26%. The research results revealed that the instantaneous PAR and the daily PAR estimated by the model developed in this paper could be available to the complex terrain of the upper Min River Basin.
  • A New Data Assimilation Method Based on Robust Ensemble Filter
  • BAI Yulong;ZHANG Zhuanhua;YOU Yuanhong;LIU Yingjuan
  • 2017 Vol. 36 (4): 1052-1059.  DOI:10.7522/j.issn.1000-0534.2016.00072
  • Abstract ( ) HTML PDF (512KB) ( )
  • The background error covariance matrix based on properties of the ensemble prediction statistics play an important role in the ensemble Kalman filter data assimilation. However, data assimilation divergence occurs from the inaccurate estimate of the covariance matrix and the limited ensembles. In this study, based on an ensemble time-local H-infinity filter which inflates the eigenvalues of the analysis error covariance matrix, a new data assimilation filter method is proposed, referred to as the inflation transform matrix eigenvalues algorithm, in order to improve properties of the estimation. The properties of data assimilation is improved in the framework of ensemble filters according to the min-max criterion of robust filtering theory. Using the nonlinear Lorenz-96 chaos system, we investigate how the ensemble time-local H-infinity filter methods impacts the robustness of the assimilation systems under the selected change conditions, such as initial background conditions, force parameters, and performance level coefficients. It is show that the ensemble time-local H filter has good robustness to the change of above parameters. Compared with traditional filter methods, robust filter methods can improve the assimilation effect.
  • Application of the Particle Swarm Optimization in the Land Surface Model Parameters Calibration
  • YANG Qidong;LING Caiyun;DU Bing;WANG Lijuan;YANG Yang
  • 2017 Vol. 36 (4): 1060-1071.  DOI:10.7522/j.issn.1000-0534.2017.00004
  • Abstract ( ) HTML PDF (1130KB) ( )
  • The uncertainty of the input parameters in land surface model can introduce simulation deviation. To improve the capability of the models and reduce the parameter uncertainties, usually the parameter optimization process is necessary. In this study, using the surface layer data observed in Wenjiang station and the particle swarm optimization (PSO) algorithm to optimize soil and vegetation parameters that difficult to obtain by observations in the SHAW (Simultaneous Heat and Water) model. On this basis, the SHAW model was run with the optimized and default parameters. Then the simulations were compared with the corresponding observations to investigate the effect of optimization parameters in land surface process simulation. The following conclusions were drawn:Using the optimized parameters calibrated by PSO algorithm can improve the simulation of the soil moisture and latent heat flux. The biases between simulated soil moisture and latent heat flux with the corresponding observations are decreased, but the net radiation, soil temperature and sensible heat flux simulation are not improved. This study suggests that PSO algorithm can be used for land surface model parameter optimization, but the simulation of all variable cannot be simultaneously improved only by optimization process.
  • Analysis on the Weather Radar Products Characteristics of the Gust Front and the Wind after the Gust Front on July 14, 2015
  • WU Juxiu;ZHOU Qing;YANG Chuanfeng;HUANG Lei;TU Aiqin;MA Chuancheng
  • 2017 Vol. 36 (4): 1082-1090.  DOI:10.7522/j.issn.1000-0534.2016.00090
  • Abstract ( ) HTML PDF (1558KB) ( )
  • Using Jinan Doppler weather radar and automatic station data, and combining the weather situation and the real weather state, the evolution characteristics of the gust front and the wind after the gust front occurred in Shandong province on 14 July 2015 were analyzed. The results showed that the wind with more than 8 grade continued more than an hour during the life cycle of the gust front, which exceeded three hours, and the measured maximum wind speed reached 24 m·s-1 (9 grade gale). During the development and vigorous stages of the gust front, the storm parameters of the strongest convective cell leading to the gust front were that maximum reflectivity factor remained at around 60 dBZ, the strong center height top was around 5 km, cell top was above 9 km, C-VIL was over 40 kg·m-2. The storms had the propagation characteristics with first left to spread then right to spread, then two storm groups were developed, which jointly maintained the development and sustainability of the gust front. The difference between the two storm groups for the echo intensity and top was not obviously, but there was larger difference among the strong winds caused by the two storm groups. The largest wind power reached 10 grade caused by the left storm groups, and the gust front ahead of them reached the largest wind power with 9 grade, but for the right storm groups, the corresponding values were 8 grade and 7 grade respectively. There was lager inflow in the lower back of the left strong storms, and the right storms did not. Strong rear inflow led storms to produce stronger sinking airflow, then to produce stronger downburst and gust front on the ground.
  • A Quasi-Lagrangian Integration of Conservation of Atmospheric Mass with Unify Scheme of Cubic Spline Function Transformating on Quasi-uniform Latitude-longitude Grid and Its Integration Cases
  • GU Xuzan;ZHAO Jun;TANG Yonglan
  • 2017 Vol. 36 (4): 1091-1105.  DOI:10.7522/j.issn.1000-0534.2016.00069
  • Abstract ( ) HTML PDF (718KB) ( )
  • The spline format is a no-linear, second-order derivative one, its linear segment is that of the second-order central difference. In this paper, we give a derivation proof of that the space truncation error, phase velocity and group velocity errors of the second-order center differential is halved that of the first-order center differential under a hypothesis of genuine solution of simple harmonic wave. So, we draw lessons from the idea of the dynamic core of spectral model, the semi-implic semi-Lagrangian integration scheme with 2D spectral spherical harmonic function transform on the Gussion grid, to introduce a new explicit quasi-Lagrangian integration scheme with cubic spline function transform on guasi-uniform latitude-longitude grid (called "spline model"). Adopting original atmospheric equations of motion, which includes that in the North Pole and the Sorth Pole, a general forecast equation of spline format of space-time second-order differential remainder is derived, then obtain the hydrostatic pressure and temperature forecast eqations of conservation of the atmospheric mass. Based on uniform latitude-longitude grid, we harmonize two quasi-uniform ones, which must be quasi-uniform latitude space, and on which cubic spline function transformation (transformation=fitting+interpolation) must be done for variables of pressure, temperature, moisture, winds and general Newtonian force acting to unit air mass on rotating earth (acceleration), which made all of them second-order derivative, to solve the track of an upstream point, but the upstream air parcel goes alone just "cubic path" of fitting their slopes, curvatures and torsions of the variable fields to "bicubic surface in horizontal + cubic spline in vertical". It is with a path of uniform acceleration motion to forecast wind field, and with fitting splines to the paths of the 3D hydrostatic advection and getting its implicit average divergence in one time step, to forecast increments of pressure and temperature fields in the adiabatic process. We give two integration cases that testify to the dynamic core of global spline model.
  • Comparative Analysis of SAFIR and ADTD Lightning Location Data over Beijing and Its Circumjacent Regions
  • LI Jingxiao;GUO Fengxia;HU Haibo;LI Rujian;QIAN Muhui;XIAO Wenan
  • 2017 Vol. 36 (4): 1115-1126.  DOI:10.7522/j.issn.1000-0534.2016.00132
  • Abstract ( ) HTML PDF (1060KB) ( )
  • The data of lightning location system is very important in scientific research and business of lightning protection. The characteristics of temporal, spatial and current distribution could be analyzed from the lightning location system and the characteristics could provide some guidance for the rational design of lightning protection project or lightning physics research.However, there are some differences in detection results between the different systems. The detection performances of the lightning location system are well known by comparing and analyzing the results of the different systems. Therefore the observation data of SAFIR system and ADTD system were compared and analyzed over Beijing and its surrounding areas in 2008. The results showed:The frequency of positive and negative CG (Cloud-to-Ground) lightning detected by SAFIR were both less than those detected by ADTD. However, the characteristics of the daily variation, the monthly variation of positive CG lightning and negative CG lightning were essentially similar respectively. The percentage of positive CG lightning frequency accounting for total lightning detected by SAFIR was higher than that detected by ADTD. The high value area of CG lightning of the SAFIR system was mainly distributed in the south, while the ADTD system's was mainly distributed in the north. The distributions of low value area of CG lightning were basically the same. The positive and negative CG lightning current intensity of SAFIR system was less than that of ADTD system. More concretely, the positive CG lightning current intensity of the former was 25 kA less than the latter, and meanwhile the negative CG lightning of the former was 10 kA less than the latter. The diurnal variation and the monthly variation characteristics of the current intensity of the two systems were basically similar. The cumulative probability distribution of negative CG lightning current by ADTD was consistent with that of the IEEE working group. The spatial distribution of current intensity of the positive CG lightning in the SAFIR system was relatively concentrated, however the ADTD system's was relatively dispersed. On the whole, the temporal distribution characteristics of the lightning detected by the two systems were similar, but the characteristics of the frequency and intensity distribution were different. The different reasons still need further study. Combining with the relevant literature, the different reasons might be related to the CG lightning waveform criterion and threshold selection, time resolution of location system itself, the installation location environment, the maintenance and calibration of the system and so on. Finally, it was preliminarily concluded that the performance of detecting CG lightning from ADTD system was relatively reliable over Beijing and its surrounding areas in 2008.
  • Review on Study of Atmospheric Boundary Layer and Wind Power Generation Interaction
  • ZHANG Shuangyi;HU Fei
  • 2017 Vol. 36 (4): 1127-1137.  DOI:10.7522/j.issn.1000-0534.2016.00095
  • Abstract ( ) HTML PDF (666KB) ( )
  • Atmospheric boundary layer (ABL) and wind power generation (WPG) interaction has become one of the hottest research subjects in recent years, and its study has both important scientific significance and high industrial value. Beginning with introduction of WPG's fundamentals and theories, this paper describes and discusses principles and mechanisms of ABL and WPG interaction, and also summarizes and concludes the latest study progresses in the field. The influence of ABL on WPG is mainly concerned with two aspects:The wind turbine's output power and mechanical load, which play key roles in the wind turbine's energy production and structural integrity. The Wind turbine's output power and mechanical load generally increase with wind speed, and they also were found to be affected by structure and characteristic of ABL's ground wind field in recent studies. Due to wildly existence of wind shear phenomena in ABL, the wind turbine's output power is decreased and mechanical load is increased. Turbulence phenomena have both positive influence on the wind turbine's output power in low wind speed section, and negative influence in high wind speed section. However, the wind turbine's mechanical load monotonically increases with turbulence intensity increasing. ABL's stratification stability has significant diurnal variation, along with changing ground wind field's structure and characteristic (such as wind shear and turbulence), and accordingly affects wind turbines' output power and mechanical load characteristics. The mechanisms of ABL's influence on WPG need to be further investigated, and the mathematic-physical models for practical engineering need to be established. The wind turbine absorbs wind energy by blades and rotor rotating, which accordingly exerts perturbation effect on the air flow. As a consequence, the downwind area's wind speed is decreased and turbulence is increased, and both of them were found having complex space distributions in latest studies. The so-called "wake effect" not only has negative influences on the wind turbine's output power and mechanical load, but also can change local meteorological elements and weather processes. Large scale wind farms or wind power bases, which extend tens of kilometers and planting hundreds of wind turbines, can produce huge perturbation effect and then change the whole structure and characteristic of ABL. The inner boundary layer model of "infinite" wind farm was developed to estimate ground wind field's wind speed and turbulence properties in large scale wind farms' affection scenario. The model was applied not only in wind energy industry for calculation of wind turbines' output power and mechanical load, but also in atmospheric science study for assessment impact of today's world-wide rapid growth of WPG on local and global climate-environment change.
  • Advances on Research of Yangtze-Huaihe Shear Line
  • YAO Xiuping;SUN Jianyuan;MA Jiali
  • 2017 Vol. 36 (4): 1138-1151.  DOI:10.7522/j.issn.1000-0534.2017.00015
  • Abstract ( ) HTML PDF (605KB) ( )
  • The Yangtze-Huaihe shear line is a specific weather system in the East China, which is closely related to the heavy rain during the Meiyu period. Therefore, a comprehensive understanding of the Yangtze-Huaihe shear line is significant to improve the ability of weather forecast in East China. This paper reviews the recent advances on the researches of the Yangtze-Huaihe shear line related to the definition, classification, structure, mechanism of formation and development, the impacts and the interaction with other weather systems. The shear lines, including warm shear line, cold shear line, quasi-static shear line and vortex shear line have differences as for the weather systems distribution of different levels. The position and intensity of other systems have strong impact on the formation and development of shear line and shear line torrential rain. The diversity of the structure and the multi-scale property about the Yangtze-Huaihe shear line are released focusing on the classical definition and the operational needs. Moreover, the further investigation aspects, such as 3-dimensional dynamical structure, thermal structure and other multiformity feature, associated with the Yangtze-Huaihe shear line are given under the background of the increasing observational dataset.