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28 October 2019, Volume 38 Issue 5   
  • Climate Change Characteristics in Qinghai-Tibetan Plateau during 1961-2010
  • XU Lijiao;HU Zeyong;ZHAO Ya'nan;HONG Xiaoyu
  • 2019 Vol. 38 (5): 911-919.  DOI:10.7522/j.issn.1000-0534.2018.00137
  • Abstract ( ) HTML PDF (6122KB) ( )
  • Based on 158 station observations of temperature (including average, lowest and highest temperature), precipitation and wind speed in and around Qinghai-Tibetan Plateau (QTP) from 1961 to 2010, the climate change characteristics in QTP were analyzed. The results are as follows:(1) The main body of QTP was getting significantly warmer and wetter, while the wind speed of the plateau was decreasing. But some parts of the eastern QTP were warming and drying. (2) The temperature rise was mainly contributed by the lowest temperature at night. The heating rates varied in different regions and it was higher in the central QTP than that in the east. The average and maximum temperatures had abrupt changes in 1994 and 1997, respectively. The rising rate was obviously accelerated after the mutation. There were quasi-8-year oscillations in all three temperatures, while other shorter-and longer-period oscillations were inconsistent. (3) The spatial distribution of precipitation decreased gradually from southeast to northwest, and there were several abrupt changes, which occurred in 1965, 1977 and 1995, respectively. The change rate of precipitation before and after the abrupt change was obviously different. There are quasi-4-year and quasi-10-year oscillations in precipitation and the wind speed had 18~20 year oscillation. (4) The first load vector of EOF decomposition of the average, the lowest and the highest temperature of QTP showed the same positive value in the whole region, and the center area was located in the area of 94°E97°E, which indicated that the hinterland of QTP was the most sensitive areas of the average, lowest and highest temperature changes. (5) The second load vector of EOF decomposition of average, lowest and highest temperature generally showed that the main body of the plateau was opposite to that of the eastern and northern marginal regions. That is, when the main body of the plateau was heating up (cooling), the eastern and northern fringes were cooling (warming).
  • Study on the Effects of Snow Cover on Heat Transport in Land Surface Processes over Qinghai-Tibetan Plateau
  • WANG Ting;LI Zhaoguo;Lü Shihua;YAO Chuang;MA Cuili
  • 2019 Vol. 38 (5): 920-934.  DOI:10.7522/j.issn.1000-0534.2019.00026
  • Abstract ( ) HTML PDF (22998KB) ( )
  • Based on the long-term snow depth dataset of China (from 1979 to 2016), the distribution and variation characteristics of snow depth and snow days on the Qinghai-Tibetan Plateau (QTP) are analyzed. This study divides the snow cover period into three stages (accumulation, peak and melt). Combined with ERA-Interim monthly average reanalysis data, the relationships between snow cover and surface heat conditions (air, surface and soil temperature) and energy transport (surface net short-wave and net long-wave radiation, sensible and latent heat flux) in the TP are analyzed. The study preliminary discusses the role of snow in the QTP land surface process. The results show that:the snow (depth and days) on the QTP shows a decreasing trend during 1979-2016, but the trend in the Source Region of the Yellow River increases. The most significant decreasing trend appears in the peak snow stage (from January to February). The snow cover on the QTP plays a most important role on surface cooling, the response of deep soil temperature to the snow is hysteretic. The reduction of snow cover inhibits the upward heat transfer of soil, which is not conducive to the formation of frozen soil. The QTP snow cover shows a negative correlation with the sensible heat flux and also the surface heat flux. The negative correlation between snow cover and latent heat flux is weaker than that between snow cover and sensible heat flux. Due to the relatively large bias between QTP snows depth from ERA-Interim and the remote sensing data used in this study (including spatial distribution, climate tendency rate, inter-annual variability and absolute size, etc.), the snow cover shows a low relevant to the surface thermal condition and the surface heat flux. It is necessary to make a further discussion by the land surface model simulation.
  • Analysis of the Distribution Characteristics and Trend of Air Vapor in Qilian Mountains
  • ZHU Biao;ZHANG Qiang;LU Guoyang;LI Danhua;LI Chunhua
  • 2019 Vol. 38 (5): 935-943.  DOI:10.7522/j.issn.1000-0534.2019.00047
  • Abstract ( ) HTML PDF (10570KB) ( )
  • Based on the European center reanalysis data, the sounding data and the data of continental river runoff, the distributions of water-vapor in air and the varying characteristics of annual and inter-annual water-vapor in the Qilian Mountains are analyzed. The results showed that the vertical accumulation of water-vapor content per unit area varies greatly with seasons, being the maximum in summer, fewer in autumn, and the minimum in winter. What different from the past is that under the appropriate weather conditions, the spring water-vapor in air will have better development prospect. Moreover, water-vapor in the east region of Qilian Mountains is much more than that in the west region all the year. There is a low value center of water-vapor in north Qilian Mountains, which was unrecognized because of the low spatial resolution of the old data. The water-vapor of the low value center has a wide difference while the value of summer is six times more than that of winter, the distribution of vapor density is similar. Vertical accumulated water vapor content per unit area shows single-peak pattern, the maximum value appears from June to September, and minus in winter. In recent 37 years, water-vapor in air showed a tendency of increase, which was consistent with the rise tendency of Shulehe river and Heihe river. But the water-vapor content varies with the seasons:summer and autumn water-vapor increased while winter and spring water-vapor decreased.
  • Numerical Simulation of Seasonal Local Climate Effect in Qinghai Lake
  • SU Dongsheng;WEN Lijuan;ZHAO Lin;LI Zhaoguo;DU Juan
  • 2019 Vol. 38 (5): 944-958.  DOI:10.7522/j.issn.1000-0534.2018.00125
  • Abstract ( ) HTML PDF (4228KB) ( )
  • Due to the difference of the thermal properties between water and land, the lake has a significant impact on the local weather and climate, lakes on Qinghai-Tibetan Plateau account for more than half of China's total lake area, the effects of plateau lakes on regional weather and climate cannot be neglected, but studies on the local climate effect of the plateau lake are still insufficient. In this study, two simulation experiments that with and without lake were conducted by using the WRF-FLake dynamic coupling model to study the local climate effect of Qinghai Lake, the largest lake on TP, in a whole year. The results show that coupled model have a good performance on TP lake, Qinghai Lake reduce regional mean air temperature from January to June, while increase it from July to December. Moreover, daily maximum air temperature was decreased from January to September and daily minimum air temperature was increased from June to December, which also reduced the daily variation of air temperature. Qinghai lake have a cold lake effect in the daytime and turns to a warm lake effect in the nighttime. Qinghai lake slightly reduced the amount of precipitation in the lake area from February to June and significantly increased the regional precipitation from July to December, especially in August. The contribution rate of Qinghai lake to local annual precipitation is up to 50%~60% on the lake surface, and 10%~30% on the surrounding land. Qinghai lake increased the maximum amount of precipitation in summer, while has the largest contribution to total precipitation in autumn. The increased precipitation caused by Qinghai lake distribute most from 20:00 (Beijing Time, same below) to 02:00 of nighttime, while least from 14:00 to 20:00 of daytime. Most of them is convective precipitation in summer but not in autumn. During the daytime, the cold lake effect of Qinghai lake produces a sinking and divergent flow on the surface of the lake that inhibit the development of convection and the diffusion of water vapor, leading to a weaken of the lake effect precipitation, while the warm lake effect of Qinghai Lake in the night generate convergence and upward airflow on the lake surface, promote the development of convection and the diffusion of water vapor, strengthen the lake precipitation effect.
  • Analysis of Extreme Temperature Changes in Qilian Mountains in the Past 60 Years
  • Lü Yuemin;LI Zongxing;FENG Qi;LI Yongge;YUAN Ruifeng;GUI Juan;LI Zongjie;ZHANG Baijuan
  • 2019 Vol. 38 (5): 959-970.  DOI:10.7522/j.issn.1000-0534.2018.00135
  • Abstract ( ) HTML PDF (5353KB) ( )
  • Based on the daily maximum, daily minimum and average air temperature data of 24 meteorological stations from 1961 to 2017, 12 extreme air temperature indices recommended by the CCl/CLIVAR climate change monitoring and indices expert group were used to analyze the temporal and spatial variations of extreme air temperature indices in Qilian Mountains and the characteristic of the temporal and spatial variations are explained. The results showed that:The spatial distribution of warm indices increases to the periphery with the central and eastern part of Qilian Mountains as the region with smaller warming range. The spatial distribution of cold indices decreases from the south to the north. In contrast to warm extremes, indices that related to cold extremes showed warmer trend. The warming range of night indices is larger than day indices, which is consistent with the significant decrease of diurnal temperature range. The length of growing season length was significantly longer. The number of ice days and frost days significantly decreased, and the areas with large reduction were concentrated in the south of Qilian Mountains. After 1985, especially during the 1990s, the warming trend of Qilian Mountains accelerated. After 2000, the warming trend slowed down, and after 2010, the warming rate increased significantly. The extreme temperature indices have a good correlation with altitude. The higher altitude, the greater warming of extreme temperature indices. In the high-altitude area (>2500 m), the extreme temperature cold indices changes significantly, while in the low altitude area (< 2500 m), the extreme temperature warm indices changes significantly. The effect of the circulation index of Atlantic multidecadal Oscillation, Tropical Northern Atlantic Index, Tropical Southern Atlantic Index, North Tropical Atlantic SST Index, Caribbean SST Index on the extreme temperature warm index was stronger than that of extreme temperature cold index. Central Tropical Pacific SST mainly affects the extreme temperature cold indices, while South China Sea Summer Monsoon Index mainly affects the extreme temperature warm indices.
  • The Physical Properties and Seeding Potential Analysis of a Low Trough Cold Front Cloud System at Mountain Taihang based on Aircraft Observations
  • SUN Yuwen;DONG Xiaobo;LI Baodong;DUAN Ying;HU Xiangfeng;YANG Yang;Lü Feng;FAN Rong;KANG Zengmei;WANG Jianheng;ZHAO Xiaowei;YANG Yongsheng;FAN Hao;LI Dejun
  • 2019 Vol. 38 (5): 971-982.  DOI:10.7522/j.issn.1000-0534.2018.00112
  • Abstract ( ) HTML PDF (35398KB) ( )
  • A cold front precipitation process caused by low trough occurred in Hebei province on May 22, 2017. The Hebei weather modification office used an airborne particle measurement system to carry out five vertical soundings for the stratiform clouds with embedded convections developed in the eastern Taihang mountain. In this paper, the microphysical structure of stratiform clouds with embedded convections and the conditions for cloud seeding were both analyzed based on the data from aircraft observations, The meteorological radar in Shijiazhuang and the Ka-band cloud radar at Huangsi, Xingtai. The precipitation clouds were found in the southwesterly air current before the low trough as the stratiform clouds with embedded convections were composed of both cold and warm clouds. Our results showed that the clouds were thicker than 5 km and the thicknesses of warm and cold clouds were greater than 2 km and 3 km respectively. The height of 0℃ layer was located at 3577~4004 m, while the temperature at the bottom and top of the clouds were 15.4℃ and -17℃ respectively. A 45 dBZ radar reflectivity was detected indicating as the strongest echo of convection bubble within the clouds. However, to carry out cloud seeding, the strongest radar echo should be less than 40 dBZ and in the seeding area of convective stratiform clouds above 4000 m the radar echo should be less than 30 dBZ. The supercooled water was found in the upper-middle layers of the cold cloud above 5000 m with a content of 0.2 g·m-3. This supercooled water content would be 2~4 times richer than that of stable stratiform clouds would contain. Besides, abundant supercooled water was observed along the initial and development stage of convective bubbles. Since this layer was the key area for ice crystal growth and the temperature varied from -15℃ to -5℃, this cloud was suitable for seeding.
  • Analysis of a Precipitation Phase based on High-Resolution Data Occurredin Shaying River Basin
  • WU Wei;HU Yanping
  • 2019 Vol. 38 (5): 983-992.  DOI:10.7522/j.issn.1000-0534.2018.00128
  • Abstract ( ) HTML PDF (8097KB) ( )
  • Based on the conventional meteorological observation data, NCEP 0.25°×0.25° analysis data and the high-resolution data from the microwave radiometers and the wind profile radars, the precipitation phase of rain and snow process in the Sha-Ying river basin occurred on 21 February 2017 was analyzed using diagnostic and statistical methods. The results showed that the transition of precipitation phase was caused by continuous cooling in the lower layers, which was induced by northerly cold air at cold high bottom below 925 hPa, in the background of the rain and snow weather caused by interaction of the upper air trough and easterly cold air. In the earlier stage of this process, there was a strong warm advection below 700 hPa and a shallow cold advection below 900 hPa. The temperature structure of the whole layer was cold-warm-cold-warm, which led to the ice crystals melting into raindrops while falling. In the medium and latter stages, the strongly development of cold advection led to temperature rapidly decreasing, so the entire temperature layer turned to cold, and the phase state turned to snow. Although there was a warm layer in the local area, the phase was also snow as the warm layer was shallow and the lower cold layer was deep. The height of the 0℃ layer decreased significantly during the rain-snow transition. The 0℃ layer was above the LCL in the rainfall, and fell below the LCL in the snowfall. The bright band echo at 0℃ layer showed a significant change in the precipitation phase transition, whose height gradually decreased. The temperature and humidity profiles, the cloud base height and liquid water from the microwave radiometer all showed significant changes in the rain-snow transition. The liquid water showed rapid increase in the rain-snow transition. The wind profile qualitatively reflected the cold air moving southwards continuously, and the cold lower layer became thicker, led to the increase of precipitation intensity and the change of phase state. The wind profile velocity quantitatively reflected the difference between rainfall and snowfall process. The speed range was 1.5~7.0 m·s-1 in the rainfall, while the speed range in the snowfall was 0.25~1.5 m·s-1. The falling speed decreased obviously during the rain-snow transition, which could be used to monitor and forecast the transitions of precipitation phase.
  • Evaluation of GPM Satellite-based Precipitation Estimates during Three Tropical-related Extreme Rainfall Events
  • XIAO Liusi;ZHANG Asi;MIN Chao;CHEN Sheng
  • 2019 Vol. 38 (5): 993-1003.  DOI:10.7522/j.issn.1000-0534.2018.00143
  • Abstract ( ) HTML PDF (10818KB) ( )
  • Extremely heavy rain storms caused by typhoon usually lead to significant losses in economic infrastructure and human life in urban agglomeration. Accurate precipitation estimation from satellites is of great importance for hydrology, meteorology, climate change, and ecological research due to its extensive spatial coverage, consistent measurements over land and oceanic areas. In this research, gauge observations are used as ground true to evaluated the capacity of near real-time precipitation estimates from Integrated Multi-satellite Retrievals for GPM extent (IMERG_ER, IMERG hereafter) during three heavy rainfall storms. These storms were brought by typhoon Hato, Pakhar and Mawar, which landed Guangdong Province successively in August and September of 2017. Six commonly used skill scores are used for quantitative analysis. These scores include Correlation Coefficient (CC), Relative Bias (RB), Root-Mean-Squared Error (RMSE), Probability of Detection (POD), False Alarm Ratio (FAR) and Critical Success Index (CSI). Results show that:(1) IMERG generally captures overall characteristics of storm-based accumulated precipitation with CC about 0.80, 0.68, and 0.47, respectively, underestimates rainfall in three cases in different degrees with different RB (-12.00%, -47.06% and -29.10%), and show different uncertainties with RMSE about 33.00, 40.03 and 26.40 mm, which may be caused by complex terrain and rapid variation of moisture transport; (2) IMERG's ability on estimation of extreme heavy rain is unstable according to result of CC(0.59, 0.48 and 0.33), RB(2.21%, -43.58% and -25.94%), RMSE(44.34, 51.04 and 40.64 mm) and scatter diagram; (3) IMERG grasps the magnitude of hourly rainfall caused by typhoons themselves, but underestimates precipitation derived from southwest monsoon trough, owing to limitation of PMW's low temporal resolution and IR's low accuracy; (4) IMERG has better value of POD, FAR and CSI in rainfall center. Despite the apparent differences with gauge measurements, the conclusions in this study highlight that IMERG has great potential to provide high-resolution precipitation information around the whole earth area, especially applied to tropical storms. The analysis result shows that bias of heavy rain plays main roles on the whole deviation of typhoon events.
  • Analysis of a Sustained Rainstorm Accompanied by a Plateau Vortex and a Tropical Cyclone
  • HE Guangbi;XIAO Yuhua;SHI Rui
  • 2019 Vol. 38 (5): 1004-1016.  DOI:10.7522/j.issn.1000-0534.2018.00131
  • Abstract ( ) HTML PDF (11628KB) ( )
  • In order to further investigate the mechanism associated with a sustained rainstorm process occurred in Sichuan, Shanxi and Gansu province in late July 2010, analysis were conducted on the circumfluence background and the directly related weather systems, e. g., the plateau vortex, the tropical cyclone, the mesoscale convective and the warm/cold advection together with their interactions. The data used in this study includes MICAPS data, FY-23 radiation brightness temperature, TRMM satellite rainfall product, and NCEP Reanalysis dataset (1°×1°, 6 hours). The results show that:(1) The sustained rainstorm process occurred under favorable conditions when the South Asia High in the upper troposphere changed from a zonal pattern to a meridional pattern, the subtropical high in the middle troposphere shifted from east to west, the landed tropical cyclone moved to the west, the plateau vortex was blocked on the east and the mesoscale convection systems kept reoccurring. (2)The interaction between the plateau vortex and the tropical cyclone decreased the velocity of both systems, enhanced the shear field in the vortex area, therefore a strengthened vortex was maintained by the positive vorticity advection transport. (3) The low vortex provided favorable uplifting conditions for rainstorms to occur and produced strong positive vorticity as well as convergence upward movement during precipitation in the vortex area. The maximum rainfall occurred concurrently with the strongest convergence ascending motion. The positive z-helicity during precipitation process in the lower troposphere helped to maintain low vortex system and sustain precipitation; the position and time of high z-helicity provide certain indicative to the occurring time and location of heavy rainfall. (4) The transport of warm advection in the lower troposphere continuously accumulated energy in the rainstorm area, incurred frequent mesoscale convection system activities and thus resulted in sustained rainfall.
  • Analysis on the Characteristics and Mechanism of a Rare Ocean-effect Snowstorm in the Western Shandong Peninsula
  • ZHENG Yi;YANG Chengfang;GUO Junjian;ZHANG Lei;JIAO Yan
  • 2019 Vol. 38 (5): 1017-1026.  DOI:10.7522/j.issn.1000-0534.2018.00140
  • Abstract ( ) HTML PDF (29380KB) ( )
  • In this study, amount of available observational data were used, including satellites (MODIS and HIMAWARI-8), Doppler radar, profile radar, automatic stations, buoy stations, routine observation data, FNL atmospheric reanalysis data and ERA_Interim reanalysis data. The ocean-effect snowstorm occurring in the western and northern Shandong Peninsula during 25-26, November 2015 was diagnostically analyzed. The results are as follows:(1)In this case, the cold air was strong, the cold vortex was located westward and southward, corresponding to the surface isobaric cyclone bending anomaly, which provided a favorable large-scale background condition for the snowstorm in the western peninsula. (2) There were many snow cloud bands in the snow process, and there may be multiple cloud clusters in each cloud band. The location and development intensity of the cloud belt had a good indication for the snowfall area and amount. (3) Corresponding to the strong snowfall period, the Sea-air temperature difference was around 14℃, there were unstable stratification in the western Shandong Peninsula, the ground convergence line provided the dynamic trigger mechanism, the water vapor accumulated in the early stage and the strong water vapor convergence in the later stage provided sufficient water vapor conditions. The low level convergence area maintaining long time made the snowstorm cloud belts develop strongly and produced "train effect", which was the main cause of the blizzard in the western part of the peninsula. (4) In the course of the blizzard, the western part of the peninsula was superior to the northern part in terms of energy and water vapor, and the dynamic maintenance mechanism was different from the northern part. The convergence of the northwest wind and the northerly wind existed below 900 hPa, which can be used as a reference in the future weather forecast.
  • Study on the Characteristics of Boundary Layer Height in Arid and Semiarid Regions of East Asia and North Africa
  • XU Xiaoran;ZHAO Yanru;HUANG Shan;MAO Wenqian;GUO Yanling;ZHANG Wenyu
  • 2019 Vol. 38 (5): 1038-1047.  DOI:10.7522/j.issn.1000-0534.2018.00144
  • Abstract ( ) HTML PDF (3725KB) ( )
  • The Boundary Layer Height (BLH) of the arid and semiarid regions in East Asia and North Africa (19002010) is compared by using the reanalysis data of ERA-20C of the European center. The result reveals differences of spatial distribution and time variation of different climate zones' BLH in the two regions. It shows that there is a close relationship between the spatial distribution of the BLH and the degree of climate wetting and drying, and is also affected by the altitude and the distribution of rivers and lakes. The BLH in the arid and semiarid-semihumid transition zones is increasing in East Asia and North Africa. The BLH in the extreme arid region, the arid-semiarid transition region and the semiarid region is increasing in East Asia but decreasing in North Africa. Extreme arid regions contributed the least to the overall annual change of BLH in arid and semiarid regions, with 11.05% in East Asia and 3.68% in North Africa. In East Asia, semi-arid regions had the largest contribution of 23.74%, while in North Africa semiarid-semihumid transition zones have the largest contribution of 28.89%. The changes of BLH in both regions contain oscillations with periods of 60 a, 30 a, 10 a, 5~7 a and 2~4 a. In the long-term cyclical changes, the BLH of the two regions are basically in an anti-phase relationship, and in the short time scales, it is in the relationship between the anti-phase and the same phase alternates. In the long-term change of BLH, the BLH of each season in East Asia is increasing in 111 years, while the BLH in North Africa is increasing in winter and decreasing in the other three seasons. Among the interannual changes of BLH, summer dominates the interannual changes of BLH in the whole region, with East Asia contributing 58.50% to inter-annual changes and North Africa contributing 57.52% to inter-annual changes. And the annual change contribution rate of autumn in North Africa is more than twice that of East Asia.
  • Relationships between Boundary Layer Height and Different Disaster Weathers in North-Central Qinghai Province
  • MA Yuancang;LI Yanying;YANG Jiping;ZENG Ting;ZHANG Aiping;ZHANG Chunyan
  • 2019 Vol. 38 (5): 1048-1057.  DOI:10.7522/j.issn.1000-0534.2018.00136
  • Abstract ( ) HTML PDF (2439KB) ( )
  • Using routine data of daily high altitude pressure, temperature and humidity at 07:00 (Beijing Time, after the same) and every 50 m infilling data of daily high altitude pressure, temperature, humidity and wind at 19:00 in 2013-2017, T-logP method and 5 point smooth potential temperature gradient method were used to calculate the boundary layer height (BLH) of four stations in Qinghai, namely Mangya, Golmud, Dulan and Xining, respectively. Based on the surface hourly and daily data from 2006 to 2017, the influence factors and their relationships with disaster weathers were further analyzed. The results showed that the BLHs were higher in the northwest than in the southeast over research region, and higher in the spring of March and May, and the highest in April that was more than 4500 m. The BLH was mainly related to the maximum ground temperature difference, maximum wind speed, daily temperature range and precipitation. The bigger ground temperature difference, the higher the wind speed and the smaller humidity were, the higher the BLH was. In the BLHs of wind and sand, the highest height of dust was 3578 m in March, and that in other wind-sand weather was between 3800~4000 m in April. The longer the dust storm lasted, the higher the BLH was. The sandstorm in the Plateau was mainly concentrated in the afternoon and night from April to June, which was 3100~4200 m from April to May. Precipitation had a great influence on BLH, with the increase of rainfall intensity, the BLH decreased. The maximum height of light rain, moderate rain and heavy rain was 3354, 1855 and 1300 m respectively, further corresponding pressure of the boundary layer was 480~640 hPa of light rain, 590~720 hPa of moderate rain and between 650~710 hPa of heavy rain. The BLH of high temperature reached 5210 m in June and more than 3600 m in JulyAugust, while the thunderstorm decreased from 5050 m in April, 2100 m from May to June and to 1100 m from July to September. The BLH of thunderstorm was lower because more than 95% of thunderstorms were accompanied by precipitation from May to October.
  • The Difference Analysis of Structure between Two Long-Lived Isolated Supercell Storms
  • ZHANG Yujie;YUAN Wenhua;ZHANG Wu
  • 2019 Vol. 38 (5): 1058-1068.  DOI:10.7522/j.issn.1000-0534.2019.00055
  • Abstract ( ) HTML PDF (20542KB) ( )
  • Based on the Doppler weather radar data of Jinan,Shandong Province and Shijiazhuang,Hebei Province,and combined with the weather facts and sounding observation data,we analyzed the evolution characteristics,environmental parameters and airflow structure of two severe disastrous supercell storms on September 15,2013 and May 12,2008 in middle mountainous area of Shandong and Xingtai,Hebei.The results show that:Storms 0915 and 0512 are both generated under strong Northwest Airflow environment,with strong instability and vertical wind shear above moderate intensity.During the peak stage,there are obvious differences in storm parameters,the mean values of storm parameters vertical integrated liquid water based on cells (C-VIL),the maximum reflectivity (DBZM) and the strong center height (HT) of storm 0915 are significantly greater than those of 0512,the intensity of cyclone rotation in storm 0915 is obviously greater than that in storm 0512.The difference between convective available potential energy (CAPE) and vertical wind shear is the key factor leading to the difference between storm parameters and wind rotation intensity.CAPE in 0915 process is greater than 0512,which determines that the maximum updraft velocity in the storm is greater than 0512.0915 process has stronger vertical wind shear,which makes its updraft rotational intensity significantly greater than that of storm 0512.Strong rotational updraft is conducive to the hanging and maintenance of storm nuclei,resulting in stronger hail weather.
  • The Wind Shear Exponent in the Near-Surface Strong Wind in the Coastal Areas of Jiangsu Province
  • CHEN Yan;ZHANG Ning;XU Xiazhen;CHEN Bin;MAI Miao;SUN Jiali
  • 2019 Vol. 38 (5): 1069-1081.  DOI:10.7522/j.issn.1000-0534.2018.00134
  • Abstract ( ) HTML PDF (14528KB) ( )
  • In order to study the characteristics of wind shear exponent under strong wind conditions of Jiangsu Province,the long sequences(from June 1st 2009 to Nov.30th 2012, continuous 42 months),high time resolution(every 10 minutes)gradient wind speed,wind direction,temperature,pressure of 5 wind towers along the coast area are used to analyze the relationship between wind speed and altitude,the time variation of wind shear exponent and the variation law with wind speed.The 7 typhoons and 17 cold wave weather processes with great influence on Jiangsu were selected,and the variation characteristics of wind shear exponent under strong wind conditions were analyzed.The results showed that:(1) The exponential law is well fitted to the vertical variation of wind speed along the coast of Jiangsu Province.The wind shear exponent varies between 0.15 and 0.26 in different surface environments.The wind shear exponent between cut-in speed and cut-out speed of the wind turbine is 0.20,and it is 0.19 when the wind speed of 70 m is 15 m·s-1.The wind shear exponent decreases with increasing height and decreases logarithmically with increasing wind speed.(2) Due to the strong vertical mixing motion caused by the typhoon,the wind shear exponent becomes smaller,with an average of 0.19.When the typhoon center passes,the wind shear exponent and wind speed have an M-shaped variation of increasing-subtracting-re-increasing,with a minimum of 0.05,and the wind direction changes drastically,which is easy to damage the fan blades.(3) The wind shear exponent when the cold wave is affected is 0.22 on average,which is less than the average value of the same period.The wind speed inversion phenomenon is obvious,the probability between 50 m and 100 m exceeds 8%,and the maximum wind speed in the near-surface layer is prone to occur at a height of 50 m.
  • Analysis on Dynamic Condition of Three Wind Speed Fluctuation Events during An Extreme Gale Process in the West of the Hexi Corridor
  • ZHANG Wenjun;LI Jian;YANG Qinghua;TIAN Qingming;WANG Haiyan
  • 2019 Vol. 38 (5): 1082-1090.  DOI:10.7522/j.issn.1000-0534.2018.00129
  • Abstract ( ) HTML PDF (9005KB) ( )
  • Using the data of automatic weather stations,the conventional observation and NCAR/NCEP reanalysis data,the influence system configuration,the characteristics of three wind speed fluctuation and dynamic Condition have been analyzed,In order to provide experience for the prediction of gale in special terrain conditions in Western Hexi corridor.The main results are as follows:With the development and strengthening of blocking anticyclone and Cold vortex abnormal moving southward,cool advection and downward momentum transfer of high low altitude are the key factors for the formation of continued gale in the west of the Hexi Corridor; The first gale fluctuation is mainly related to the ground pressure-swing wind,and the momentum downward transmission plays an important role in the second and third gale fluctuations; The descending motion with convergent flow field at the center and left side of the upper jet stream exit region can effectively transmit the momentum of high altitude below 500 hPa,The momentum exchange in the development of unstable stratification and the vertical motion caused by the thermal and dynamic conditions in the lower layer make the momentum in the middle and lower levels move down to the near ground.During the transit of the high-level trough,the configuration of the negative vorticity advection at high level and positive vorticity advection at low level formed by the forward inclining trough is very beneficial to the momentum spreaded downward from higher level,the greater the vorticity advection gradient in the vertical direction and the lower the gradient of large value center,the more likely it is to cause the occurrence of extreme wind near the surface in the west of the Hexi Corridor.
  • Cause of the Galloping in Anhui Province along the Yangtze River in Early 2018
  • WANG Chuanhui;YAO Yeqing;XIA Lingzhi;YAO Zhenhai;DING Guoxiang;LUO Yan
  • 2019 Vol. 38 (5): 1091-1098.  DOI:10.7522/j.issn.1000-0534.2018.00141
  • Abstract ( ) HTML PDF (5940KB) ( )
  • Meteorological elements in the ice coating galloping of power line process in the region along the Yangtze River of southern Anhui in the early 2018 were analysed,as well as the weather situation lead to ice coating and gale,based on the observation data of 5min ground routine meteorological elements,the daily ice coating data of meteorological ice observation stations,the sounding data from Anqing station by 12 h and the ERA-Interim reanalysis data by 6 h.Results show that:There are varying degrees of wire icing near the dancing position,with strong northeastern wind.The angle between the wind direction and dancing wire is generally above 45 degrees,with stronger turbulence.Freezing rain and strong winds are the direct factors leading to the wire dancing.Accompanied by the wire dancing freezing rain is a typical "over cooling warm rain"; The southwest air flow in front of 700 hPa south branch trough,which maintains the existence of the warm layer,brings ample water vapor,as well as warm temperature advection for the freezing rain weather condition; the cold temperature advection by the northeast air flow under the continental cold high pressure of the 925 hPa makes the surface precipitation in the over cooling state.Strong northeastern wind were observed near dancing wire.Strengthen of cold high pressure caused by the accumulation of cold air after the front over northern China is one of the main factors that lead to the strong northeastern wind in the region along the Yangtze River of Anhui.
  • Environmental Significance of Precipitation Stable Isotopic in Dadongshu Mountain of Middle Qilian Mountains
  • ZHANG Baijuan;LI Zongxing;WANG Yu;FENG Qi;ZOU Haiming;LI Aijun
  • 2019 Vol. 38 (5): 1099-1107.  DOI:10.7522/j.issn.1000-0534.2018.00139
  • Abstract ( ) HTML PDF (1740KB) ( )
  • To investigate the environmental significance of precipitation stable isotopic in Dadongshu Mountain of middle Qilian Mountains,the characteristics of precipitation stable isotopic and the correlations between precipitation stable isotopes and local meteorological factors were analyzed in this paper based on 145 precipitation samples from Dadongshu pass site (4146.8 m) and meteorological data at the same period in 2014.The results showed that:(1) The stable isotopes of precipitation showed a significant inter-annual fluctuations and an obvious seasonal variations.The characteristics of precipitation stable isotopes appears as a high value in Summer and autumn season,and a low value in winter and spring season.(2) Temperature effect of δ18O was significant in all precipitation events.The δ18O increases by 0.62‰ for every 1℃ temperature increasing,while the precipitation effect was not noticeable.A weak precipitation effect of δ18O only appeared in summer precipitation events which can be conclude that the temperature is the mainly factor of precipitation stable isotope evolution in present study area.(3) The δ18O and d-excess in this study area were significantly positively correlated with the averaged vapor pressure.It indicated that the stable isotopes of precipitation is significant effected on the sub-cloud evaporation in this research area.The present study provided a further understand of isotopic hydrology in inland river basins at the Qilian Mountains.
  • Research on Causes of Severely Polluted Weather in Tianjin based on WRF/Chem
  • CAI Ziying;HAN Suqin;QIU Xiaobin;YAO Qing;ZHANG Min;LIU Jinle;WU Bingui;WANG Xuelian
  • 2019 Vol. 38 (5): 1108-1119.  DOI:10.7522/j.issn.1000-0534.2018.00123
  • Abstract ( ) HTML PDF (2570KB) ( )
  • The causes of severely polluted weather in Tianjin from 2014 to 2017 were studied based on WRF/Chem model by decomposing the impact of horizontal transport, turbulent mixing and vertical motion on near-surface air pollution with CO as a tracer.The findings showed that horizontal transport, turbulent mixing and vertical motion of severely polluted weather can be quantitatively described, and attribution analysis was conducted on the values of causes of severely polluted weather based on the above method.For example, the severely polluted weather on January 26, 2017 was mainly caused by decreasing turbulent mixing ability; That on February 12, 2017 by decreasing mixing layer thickness; That on February 16, 2017 by horizontal transmission; That on February 16, 2017 by decreasing downdraft and turbulent mixing capacity and mixing layer thickness.In the analysis, the meteorological conditions that are prone to severely polluted weather are formed as follows:rate of decrease of CO mass concentration per hour caused by turbulent mixing is less than 40%, the rate of increase of CO mass concentration per hour caused by vertical movement more than 1.4%, the mixed layer thickness less than 250 m, and the rate of decrease of surface CO mass concentration per hour caused by horizontal diffusion less than zero.Up to 99 of 116 severely polluted days from 2014 to 2017 met one or more of the above conditions, covering 85% of all the severe pollution processes.Although some failed to meet any of the above conditions, 99% of the processes can be interpreted as per the analysis standard for severely polluted weather.As shown by the analysis, 58% of the processes were caused by two or three meteorological factors which are closely related to weather types, such as the pollution in the rear of high pressure and horizontal transport, the pollution caused by weak high pressure from north and sinking motion.Compared with horizontal transport and the decreasing turbulent mixing capacity, the rise of near-surface air pollutant mass concentration caused by sinking motion is often neglected.However, in some processes, the rise of near-surface air pollutant mass concentration may also be caused by sinking motion, making it an important influencing factor for the formation of severely polluted weather, such as January 1011, 2014.The turbulent diffusion coefficient KZ and the hourly decrease rate of surface CO mass concentration caused by turbulent mixing β show a good power exponential relationship with the near-surface PM2.5 mass concentration, with the correlation coefficients of 0.57 and 0.73 respectively, which can play an active role in the cause analysis and prediction of severe pollution.
  • The Impact of Multi-Scale Meteorological Conditions on PM2.5 Pollution over Ji'nan
  • YIN Chengmei;HE Jianjun;YU Lijuan;JIAO Yang;ZHOU Lechen
  • 2019 Vol. 38 (5): 1120-1128.  DOI:10.7522/j.issn.1000-0534.2019.00018
  • Abstract ( ) HTML PDF (8180KB) ( )
  • Based on long-term air quality and meteorological data,the analysis of the relationship between air pollution and meteorological conditions over Ji'nan is relatively rare.Using air quality monitoring data,meteorological reanalysis data,and meteorological observation data in Ji'nan City from 2010 to 2016, this paper analyzes PM2.5 pollution characteristics,the relation between PM2.5 concentration and 2-m temperature (T),2-m relative humidity (RH),10-m U and V component of wind speed (U and V),10-m wind speed (WS),K index (K),A index (A) and boundary layer height (BLH),and circulation types.Based on the stepwise regression model,the influence of meteorological conditions on the day-to-day variation of PM2.5 concentration was quantified by explained variance.The results recover that there are a significant seasonal and interannual variations in PM2.5 concentration in Ji'nan.The annual average PM2.5 concentration decreases significantly during 2010 to 2016.PM2.5 concentration is positive correlated with T,RH,K and A significantly,while negative correlated with WS and BLH (p < 0.05).The correlations between PM2.5 concentration and U and V component do not pass t-test at 95% confidence interval.The mean PM2.5 concentrations for different circulation types have significant difference.Based on regression model analysis,it is found that meteorological conditions can explain the day-to-day variation of PM2.5 concentration from 10% to 40% in Ji'nan.Obvious seasonal difference of impact of meteorological conditions is detected.