ISSN 1000-0526
CN 11-2282/P

Volume 44,Issue 2,2018 Table of Contents

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  • 1  Comparison Analysis of Circulation Features of Different Moving Tracks of Long-Life-Cycle Plateau Vortexes Moving out of the Plateau
    SHI Rui HE Guangbi
    2018, 44(2):213-221. DOI: 10.7519/j.issn.1000-0526.2018.02.001
    [Abstract](965) [HTML](128) [PDF 3.67 M](1123)
    Using the upper-air observation data and the corresponding daily average NCEP reanalysis data, this paper first statistically analyzed the plateau vortexes which could live 3 days or longer after moving out of Tibetan Plateau in summer from 2000 to 2010. According to their different moving track, the vortexes were divided into three groups which are moving eastward, northeastward and southeastward. The results show that in July long-life-cycle vortexes moving out of the plateau move eastward far more than northeastward and southeastward, and the vortexes moving southeastward are more than those moving northeastward. However, in August, the vortexes moving southeastward are far more than those moving northeastward and eastward. Then by selecting the cases of different moving tracks, we analyzed the general circulation in the mid-upper troposphere, pointing out the common features and differences of the general circulation and temperature advection at 500 hPa and the circulation at 200 hPa. The findings indicate that the position and shape of West Pacific subtropical high influence the long-life-cycle plateau vortex moving out of the plateau at 500 hPa significantly, and the strength of the subtropical high decreases in the order of the tracks moving eastward, northeastward and southeastward. The southeastward track over the IndianBurma Region is affected by monsoon depression while the eastward and northeastward tracks are affected by the Indian monsoon trough, namely to south of 25°N of the southeastward track there is a relatively lower geopotential height which is favorable for the plateau vortex to move southward. Under the 200 hPa circulation background, the eastern end of the 1252 dagpm South Asia high is by west in the order of eastward, northeastward and southeastward tracks. For the eastward track cases, the eastern end of South Asia high is obviously by east, causing the westerly flow to guide the plateau vortex to move eastward. And for the southeastward track cases, the northern boundary of the South Asia high over the Tibetan Plateau and north-west flow after high trough at 110°E guide the plateau vortex to move southeastward. Cold air is also an important factor for the development of these long-life-cycle plateau vortexes. The corresponding relationship exists between the moving direction of the temperature advection zone and the moving tracks of long-life-cycle plateau vortexes moving out of the plateau.
    2  Statistical Characteristics of CG Flashes and Comparison to Radar Echoes in Different Types of Severe Convections in Jiangxi Province
    ZHI Shulin LI Jie CHEN Juan
    2018, 44(2):222-232. DOI: 10.7519/j.issn.1000-0526.2018.02.002
    [Abstract](1086) [HTML](246) [PDF 1.11 M](1248)
    Based on the data from cloud-to-ground (CG) lightning detection network with 11 ADTD equipment, doppler radar, sounding, AWS data and important weather reports in Jiangxi Province during 2004-2014, severe convective weather events in these years are divided into three types: the short-time heavy rainfall, the thunderstorm gale or hail with and without short-time heavy rainfall. The characteristics of the CG flashes and their relations to radar echoes are analyzed statistically. The results show that: (1) The short-time heavy rainfall, thunderstorm gale and hail in Jiangxi occur mainly from May to August, July to August and March respectively. The stations with short-time heavy rainfall are much more than those with thunderstorm gale or hail. The thunderstorm gale or hail weather accompanied by short-time heavy rainfall often occurs in most seasons in addition to early spring and middle summer. (2) The more short-time heavy rainfall intensity is the more northern its position, and the more severe the CG flashes are. There are obvious seasonal differences of CG flash totals with different hourly rainfall: In March and April, the CG flashes are most evident with hourly rainfall of 50-55 mm, while in May, June and July, the CG flashes increase with hourly rainfall, reaching the top with hourly rainfall of 55-60 mm. In August and September, the most evident is the events with the hourly rainfall of 40-45 mm. (3) From March to May, CG flashes seen 30 min before hail without short-time heavy rainfall have no significant differences compared with those of thunderstorm gale, yet the average intensity of thunderstorm gale is higher than that of hail weather. From June to September, CG flashes in thunderstorm gales are 2-4 times more than that of hail, the average intensity of the flashes is higher than the former, and the intensity of +CGs is also slightly more intense. (4) The +CGs and -CGs with short-time heavy rainfall occurrence are separately in August and June. For the total CGs one hour before the severe weather happens, the seasonal change of that with hail is not evident, but it turns contrary to thunderstorm gales, more evident in summer than in spring. Also, there is a positive correlation between the hail CG flash totals and hail diameters. (5) From March to August, the CG flashes of thunderstorm gale or hail accompanied with short-time heavy rainfall are much higher than that without short-time heavy rainfall, while the average intensity of the former is much higher than the latter. (6) Before the severe convections take place, the negative CG flashes frequency is more evident than the positive one, but its intensity is lower than the latter. The higher the echo of reflectivity above 45 dBz extends, the more the CG flash totals are, but the average intensity change is not obvious.
    3  Spatio-Temporal Variation of Snow Depth on Tibetan Plateau over the Last 30 Years
    CHU Duo LUOSANG Quzhen LIN Zhiqiang YANG Yong
    2018, 44(2):233-243. DOI: 10.7519/j.issn.1000-0526.2018.02.003
    [Abstract](1017) [HTML](2194) [PDF 5.09 M](1478)
    Under the context of global warming, understanding of spatio-temporal variation of snow depth on the Tibetan Plateau (TP) is particularly important because climate observations in high-altitude regions have shown more sensitivity to climate change. The snow depth on the TP, as one of key components of cryosphere, is related to water availability downstream of major river basins in Asia and its anomalies may potentially affect subsequently regional weather/climate and monsoon systems over eastern and southern Asia through mechanical forcing and changing surface heat and moisture fluxes. Therefore, in this study, the spatio-temporal variation of snow depth on the TP is analyzed using observation data from 94 meteorological stations for the period from 1981 to 2010. The main results are as follows. (1) The highest snow depth record mainly takes place in the southern Himalayas Mountains and the lowest snow depth is found in dry-warm valleys in southern TP and Qaidam Basin in the northern TP. (2) There is a significant decreasing trend in annual mean maximum snow depth on the TP with a rate of 0.55 cm every 10 years in the last 30 years and abrupt climate change of snow depth from high to low occurs around 1997. (3) On seasonal scales, mean maximum snow depth in spring also has a very significant decreasing trend at a rate of 0.47 cm every 10 years, and abrupt climate change of snow depth in spring from high to low occurs around 1998. In autumn and winter, the decreasing trend in mean maximum snow depth is not noticeable. At a specific station, the changing trend of snow depth varies from region to region. In autumn, snow depth decreases at 56% stations but increases at 31% stations on the TP. In winter, the decrease in snow depth occurs at 61% stations and stations with higher decreasing rate are primarily distributed in the southwestern TP while the increasing trend of snow depth is found at 31% stations, which are mainly located in eastern part of the TP. In summer, snow cover on the TP is very scarce, primarily distributed in alpine region of high altitude and latitudes. Over the last 30 years, the decreasing trend of snow depth in summer is also significant.
    4  Design and Verification of Quality Control Methods for Automatic Soil Moisture Observation Data in China
    WANG Jiaqiang ZHAO Yufei REN Zhihua GAO Jing
    2018, 44(2):244-257. DOI: 10.7519/j.issn.1000-0526.2018.02.004
    [Abstract](985) [HTML](300) [PDF 12.59 M](1209)
    Soil moisture data play a key role in the study of climate change and agricultural drought monitoring, agricultural weather forecast and service. In order to effectively eliminate the abnormal data in observations, this paper puts forward a set of quality control (QC) methods which could be applied to the data of automatic soil moisture observation station (ASMOS) in China. First, based on the data of ASMOS 2014 in China, the abnormal data are divided into four categories according to their characters. Secondly, under the consideration of three aspects: threshold value check, internal consistency check, time consistency check, the QC methods are designed, which include abnormal extreme check, abnormal increase check, abnormal decrease check and abnormal constant check. Finally, the QC methods are verified by using the data of ASMOS and soil volumetric water content products of CMA Land Data Assimilation System (CLDASV2.0) in China in 2014-2015. The results show that: (1) the four kinds QC methods can effectively identify the four types of abnormal data. (2) The results from the four kinds QC methods are in good agreement in temporal continuity and spatial distribution. (3) The QC methods can effectively reduce the root mean square error (RMSE) between observation and the CLDAS data. At present, the methods have been applied to the Meteorological Data Processing Service System.
    5  Climatology of Cold Season Elevated Convection in Northern China
    LIU Zhouyang YU Xiaoding WANG Xiuming ZHOU Xiaogang
    2018, 44(2):258-267. DOI: 10.7519/j.issn.1000-0526.2018.02.005
    [Abstract](1309) [HTML](335) [PDF 2.90 M](1257)
    Conventional surface observation, soundings, comprehensive monitoring data of severe convective weather and NCEP analysis data are used to investigate statistically the spatiotemporal distribution, frontal characteristics and instability mechanisms of cold season (except June, July and August) elevated convections in northern China (32.5°-53.5°N, 105°-135°E) during a 16y period from 2000 to 2015.The events are concentrated in south central Hebei, western Shandong and north central Henan. The annual frequency distribution of elevated convections is bimodal, with a primary peak in February and a secondary peak in November. Cold front is the primary frontal system dominating the events. There exists thick cold surface air and strong temperature inversion when elevated convection occurs and more than half the events are triggered over the inversions with a temperature difference greater than 6℃. In addition, strong vertical wind shear (20-30 m·s-1) is frequently observed which is conductive of symmetric instability. The result further shows that conditional symmetric instability and frontogenetic forcing are the dominant mechanisms generating cold season elevated convections.
    6  Analysis and Application of the Test Method of Reflectivity  Difference Between Adjacent Radars
    ZHANG Lin YANG Hongping PEI Chong GAO Yuchun
    2018, 44(2):268-276. DOI: 10.7519/j.issn.1000-0526.2018.02.006
    [Abstract](1036) [HTML](200) [PDF 4.70 M](1197)
    In this paper, one method is proposed to test the echo difference between two adjacent radars’ overlap areas. The reasons of the difference can be divided into external and internal factors. The external factors include occlusion, ground/AP clutters, atmospheric attenuation, etc. and all of these external fact-ors are removed by this method. The spatio-temporal consistency is matched according to the relationship between raindrop diameter and falling speed. Then, the reflectivity factors between two radars are compared. If significant difference still exists, it is due to some internal factors. In addition, the paper also discusses two cases, one is the malfunction of frequency source in Zhengzhou Weather Radar, and the other is the squall line in Guangdong Province. Based on the two cases, the method is proved to be able to test the reflectivity difference effectively. Thus, this method could have high application values in weather radar real-time monitoring operation. If reflectivity factor of one radar differs from other radars nearby, the information can be quickly transferred to the maintenance workers so that they can check and solve the problem in time.
    7  Verification and Analysis on Tropical Cyclone Ensemble Forecast of European Centre for Medium-Range Weather Forecasts from 2009 to 2015
    YANG Guojie SHA Tianyang CHENG Zhengquan
    2018, 44(2):277-283. DOI: 10.7519/j.issn.1000-0526.2018.02.007
    [Abstract](871) [HTML](569) [PDF 2.19 M](1161)
    The verification and analysis on tropical cyclone (TC) ensemble forecast of European Centre for Medium-Range Weather Forecasts (ECMWF) over western North Pacific in 2009-2015 are given from four aspects. The results show that the capability of ensemble forecast on TC tracks has been improving annually, but the intensity forecasting is always weak. The stronger the TCs are, the more accurate the ensemble forecasts of TC moving speed and moving direction are, though the forecasted speed is slow and the forecasted direction turning leftwards exists, whereas the forecasted intensity is weaker. On the other hand, the steering flow of TCs is classified into three grades. When the steering flow is weak, the TC moves slowly, and the direction forecasting is uncertain; when the steering flow is strong, the TC moving direction forecasting is reliable, but the speed forecasting is not good enough. As to the TCs over South China Sea classified according to three different types of tracks, the speed and direction ensemble forecasting errors would be small in westerly and northwesterly tracks, but would be large in westerly to northerly tracks. For the TC with westerly to northerly tracks, the direction forecasting has large spread before turning northerly, while the moving direction would be stable after turning northerly.
    8  Analysis of the Characteristics and Forecast Difficulties of Typhoons in Western North Pacific in 2016
    GAO Shuanzhu DONG Lin XU Yinglong QIAN Qifeng
    2018, 44(2):284-293. DOI: 10.7519/j.issn.1000-0526.2018.02.008
    [Abstract](1283) [HTML](296) [PDF 4.29 M](1503)
    The characteristics of typhoons in western North Pacific in 2016 are analyzed by using the besttrack data, the CMA operational forecast data and ECMWF NWP and EPS products. The results show that no typhoon formed in the first half year but many were seen in the midsummer and autumn. This phenomenon was related to the conversion from El Ni〖AKn~D〗o to La Ni〖AKn~D〗a of the eastern equatorial Pacific SST. In some cases, the TC track forecast errors for long leadtime are extremely large, which attributes to the large spread of EPS. To improve the TC track forecasting skill, the regularity of systematic bias of numerical models could be found. The TC intensity forecast error for 24 h is larger than 5 m·s-1, which is unusual for the past decade. For individual cases, the extreme errors are 20-26 m·s-1. Almost no improvement in the TC intensity forecast skill over the recent decades. The main reason is the lack of reliable objective intensity forecasting technique. The qualitative analysis of the intensity change is not enough in the operation. So, it is urgent to establish a quantitative and fine forecast method on TC intensity to improve the TC forecast skill.
    9  Interannual Variation of Heat Wave Frequency Persistence over China and the Associated Atmospheric Circulation Anomaly
    NIE Yu HAN Zhenyu HAN Rongqing DING Ting
    2018, 44(2):294-303. DOI: 10.7519/j.issn.1000-0526.2018.02.009
    [Abstract](643) [HTML](411) [PDF 4.06 M](1255)
    Using the NCEP/NCAR reanalysis data and observation data, the variation of the heat wave frequency over China in summer during 1960-2015 is investigated. It is found that the most frequent heat wave in China is located in southeastern China and Xinjiang. Through the empirical orthogonal function analysis, the dominant modes of heat wave frequency over the above two regions are further analyzed. Examination on the atmospheric circulation anomaly and the sea surface temperature in the previous season shows that prevalence of the heat wave over southeastern China is attributed to the warming in Indian Ocean during previous months. The heat wave over Xinjiang is mainly due to the strong midlatitude warming over Pacific, Black Sea and Caspian Sea.
    10  Improvement and Application Analysis of the Comprehensive Grade  Evaluation Model of Typhoon Disaster
    WANG Xiurong ZHANG Lisheng LI Weibang
    2018, 44(2):304-312. DOI: 10.7519/j.issn.1000-0526.2018.02.010
    [Abstract](765) [HTML](212) [PDF 949.16 K](1127)
    This paper firstly discusses about the improvement of typhoon disaster comprehensive evaluating model established by Wang Xiurong et al. in 2010. First, the function optimization of damaged buildings index is redefined; second, the influence of inflation on the direct economic loss index is wiped off; third, the weight coefficient of four indicators is optimized, including the death toll of the original model, the direct economic loss, the number of damaged houses, and the flooded crops area. In the second part of this paper, the improved model is used to evaluate the historical typhoon disasters in China from 2000 to 2015 comprehensively and sort all the historical typhoon disasters from high to low based on the results. At the same time, the results are compared with the original model to evaluate the effectiveness of the improved model. Finally, the application and test analysis prove that the improved evaluation model highlights the peopleoriented concept of disaster prevention, reducing the impact of inflation on the direct economic loss index. Compared with the original model, it has a better level of recognition, and its assessment of disaster grade results is more in line with the actual disaster, having a good evaluation function. Thus, it could be applied to relevant operations of meteorological services to quickly evaluate the typhoon disaster comprehensive grades or historical sorting.
    11  Impact Analysis of a Taihang Mountain Fohn on Haze Intensity
    YANG Xiaoliang YANG Min LI Jiangbo ZHANG Shan
    2018, 44(2):313-319. DOI: 10.7519/j.issn.1000-0526.2018.02.011
    [Abstract](1006) [HTML](1186) [PDF 3.20 M](1287)
    Utilizing the NCEP reanalysis data, and the every 5 minute data of ground automatic weather station, laser radar, wind profiler and microwave radiometer, we analyzed the changes of haze intensity in a typical fohn process in Shijiazhuang during the winter of 2015. The results show that the east of Taihang Mountain experienced obvious fohn due to the topographic trough over North China with static and stable weather situation. The fohn led to a rapid decline in humidity, which might cause the rapid rising of horizontal visibility, the decline of PM2.5 concentration and the weakening of haze intensity. Laser radar could visually reflect the changes of boundary layer structure and the concentration of pollutants before and after the fohn. By using the wind profile, we learned that the changes of wind direction (may vary a lot) and speed (may be larger) are obvious below 300 m, which proves the strong pulsation of wind. The horizontal and vertical scales of fohn are 25 km and 1 km, respectively.
    12  Impact of the Reduced Observation of Russia Radiosonde on GRAPES Model
    TIAN Weihong
    2018, 44(2):320-325. DOI: 10.7519/j.issn.1000-0526.2018.02.012
    [Abstract](647) [HTML](117) [PDF 3.86 M](990)
    The radiosonde observation is one of the most important data in the data assimilation system. The Russia radiosonde observation was adjusted in January 2015, and reduced some observations at 0000 UTC and 1200 UTC. In order to verify the effect on GRAPES model, the impact experiment was carried out. The observation was retrieved from National Meteorological Information Centre of China Meteorological Adminisration (NMIC/CMA) database. The GRAPES wind analysis of Russia Region became worse because of the Russia radiosonde adjustment, but the impact on the other regions was not so much. The height analysis became a little better in Russia and East Asian Regions, which may be related to the height observation quality. From the changes of anomaly correlation coefficient of the 500 hPa height forecast, the adjustment has positive effect on the forecast for East Asia.
    13  Performance Verification of MediumRange Forecasting by T639, ECMWF and Japan Models from September to November 2017
    YIN Shan REN Hongchang
    2018, 44(2):326-333. DOI: 10.7519/j.issn.1000-0526.2018.02.013
    [Abstract](801) [HTML](104) [PDF 5.65 M](1006)
    The mediumrange forecasting performances of T639, ECMWF and Japan (JP) models from September to November 2017 are verified and compared. The results show that all the three models could predict the variation and adjustment of the atmospheric circulation over Asian middle and high latitudes well. The ECMWF model has good performance in predicting activities of the western Pacific subtropical high (WPSH) while the T639 model predicts the position of WPSH further north. For temperature at 850 hPa, mean forecast error by ECMWF model is smaller than by other two models. The T639 (JP) model gives lower (higher) temperature forecast than the observation respectively. As far as Typhoon Mawar is concerned, all the three models predict its position more northwest and strength weaker. However, the ECMWF model could show the direction change of this typhoon. The ECMWF model performs much better in forecasting the intensity of cold high pressure during a cold air process while the T639 and Japan models create greater errors.
    14  Analysis of the November 2017 Atmospheric Circulation and Weather
    YOU Yuan MA Xuekuan LI Siteng
    2018, 44(2):334-340. DOI: 10.7519/j.issn.1000-0526.2018.02.014
    [Abstract](715) [HTML](146) [PDF 2.81 M](1088)
    The main characteristics of the general atmospheric circulation in November 2017 are as follows. There are two polar vortex centers in the Northern Hemisphere. The circulation in Eurasian middlehigh latitudes showed a fourwave pattern. The East Asia major trough was stronger than normal.The northwestern Pacific subtropical high was stronger than normal, located more westward. The south branch trough was located around 90°E averagely. The monthly mean precipitation amount was 15.9 mm, which is 15.3% less than normal. In November, precipitation was characterized by more rainy days in the south of the Yangtze River and Southern China. Torrential rainfall events occurred over 58 stations, and the daily rainfall amount of 12 stations exceeded the maximum records in November. Meanwhile, the monthly mean temperature was 3.6℃, which is 0.7℃ higher than normal. The daily maximum air temperature at 55 stations exceeded the historic high in November, and the daily minimum air temperature of 7 stations broke the lowest value in autumn in history. Four waves of strong cold air processes, three major rainfall processes and one foghaze weather events occurred during this month.

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