ISSN 1000-0526
CN 11-2282/P

Volume 46,Issue 4,2020 Table of Contents

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  • 1  Analysis of Two Successive RainstormInduced LongLived Mesoscale Convective Systems Struck Pearl River Estuary During 8-9 May 2014
    CHEN Tao ZHANG Fanghua FU Jiaolan YU Chao
    2020, 46(4):449-461. DOI: 10.7519/j.issn.1000-0526.2020.04.001
    [Abstract](1133) [HTML](279) [PDF 14.74 M](1393)
    Two successive longlived mesoscale convective systems (MCSA1, MCSA2) struck Pearl River Estuary of South China during 8-9 May 2014, and induced extreme precipitation over the region. From noon of 8 May MCSA1 sustained over than 11 h on land of South China, with slowly moving towards southeast from east of Guangxi to Pearl River Estuary in Guangdong. The successive MCSA2 sustained more than 9 h, inducing rainfall of more than 400 mm along the coast of the Pearl River Estuary from early morning to noon of 9 May. Weak cold surface layer sustained in the south of South China with weak surface temperature gradience on the morning of 8 May before the convection burst. The initialization of convection was connected with strengthening of surface south 〖JP2〗wind and topographic lifting near noon of 8 May. MCSA1 evolved from〖JP〗 training line/adjoining stratiform (TL/AS) to mesoscale vortex in convective organization under weak baroclinic environment. With propagation of surface cool pool due to MCSA1’s precipitation in the early night of 8 May, surface temperature boundary and wind convergence zone was pushed to the southwest coast of Guangdong. In the late night of 8 May MCSA1 moved out of land, then MCSA2 was developing adjointly to the remnant cool pool boundary induced by MCSA1 with lowlevel southwest wind enhancing in the early morning of 9 May. MCSA2 was composed by multiple parallel mesoβ scale linetype convective systems, the extreme rainfall was related with quasistationary cool pool boundary, trainmoving cells in mesoβ scale linetype convective systems with high precipitation efficiency. From late night of 8 May to morning of 9 May, the balance between cool pool outflow and lowlevel vertical shear could sustain upright convective cells of MCSA2. In conclusion, with carefully researching on convective feedback to boundary and surface layer, the forecast skills could be improved for heavy rainfall events in weak synopticforcing environment during the prerainy season in South China.
    2  Influence of Radar Data Assimilation on the Numerical Simulation of a Rare Squall Line in Zhejiang Province in Early Spring
    CHEN Feng DONG Meiying SU Tao JI Chunxiao
    2020, 46(4):462-477. DOI: 10.7519/j.issn.1000-0526.2020.04.002
    [Abstract](907) [HTML](203) [PDF 16.77 M](1257)
    The impact of radar data assimilation on the numerical simulation of a rare squall line in Zhejiang Province on 4 March 2018 was studied in this paper. The weather research and forecasting (WRF) model and the gridpoint statistical interpolation three-dimensional variational (GSI-3DVar) data assimilation system were used. In this study, multiple-Doppler radar data assimilation was applied to initialize a squall-line convective system, and its impact on the simulation was evaluated and discussed. The results showed as follows. Radar data (especially the radar reflectivity) effectively improve the simulation of the 〖JP2〗boundary layer〖JP〗 characteristics of the squall line, which further improves the simulation effect of the composite reflectivity, precipitation and wind process of the squall line. Radar reflectivity assimilation, which directly adjusts the hydrometeors, improves the precipitation simulation in the storm and its induced evaporative cooling and forms a more intense cold pool close to reality, thus improving the simulation of the squall line. The radar reflectivity assimilation〖JP2〗 has a greater contribution than the radial velocity assimilation. Relative to assimilating radar data in non-critical areas, assimilating the small and medium-scale information carried by radar observations in key areas is more important for improving the simulation of the squall line.
    3  Mechanism of a Rare Night Sudden Intense Warming Event in Beijing and Surrounding Area
    LUO Ran ZHENG Yongguang CHEN Min
    2020, 46(4):478-489. DOI: 10.7519/j.issn.1000-0526.2020.04.003
    [Abstract](901) [HTML](905) [PDF 5.95 M](1440)
    Surface temperature normally decreases after sunset, but a great many night sudden intense warming events were observed in winter in Beijing and the surrounding area, and the intense rise in temperature could be higher than 10 ℃ per hour. Such sudden warming events are aften 〖JP2〗followed by rapid tempera〖JP〗ture dropping, which would cause great difficulty in forecasting. This paper detailedly analyzes a rare intense night warming event with the increase range of 12 ℃·h-1, which was caused by a cold front passing through Beijing and surrounding area over the night of 26 November 2010. Compared with the statistical climatological results, the heating intensity and affected area this time are extreme rarely seen. The analysis is based on the data of automatic weather stations, conventional surface stations and rawinsonde, meteorological observation tower, stationary meteorological satellite, and wind profiler, as well as the reanalysis data of NCEP. The results show that, during the event, there was significant cold advection in the lower troposphere, and significantly strong downward motion in the middle and lower troposphere illustrated by diagnosed vertical velocity and the data from the satellite and the wind profiler. The temporal evolution of both the meteorological tower observations and soundings in Beijing indicates that strong turbulence existed in the boundary layer. Therefore, this rare warming event was caused by the significant surface potential temperature differences between the plateau and the plain, the strong downward adiabatic warming and the intense turbulent mixing with strong boundary layer jet. The estimation shows that the turbulent mechanical mixing associated with the lowlevel jet could cause about 8℃ increase in temperature. Finally, the conceptual model of this event is presented.
    4  Analysis of Mesoscale Characteristics of Torrential Rainfall in Hubei Province During 18-20 July 2016
    ZHAO Xianting WANG Xiaofang WANG Jue WANG Xiaokang XIAO Yanjiao LENG Liang FU Zhikang
    2020, 46(4):490-502. DOI: 10.7519/j.issn.1000-0526.2020.04.004
    [Abstract](1015) [HTML](1088) [PDF 12.84 M](2092)
    Based on various conventional and unconventional data, precipitation characteristics, generation and development of the mesoscale convective system (MCS) and environment conditions of the torrential rainfall in Hubei Province during 18-20 July 2016 are analyzed in this paper. The results show that this torrential rainfall process was highly extreme. The process consisted of warm area precipitation in the south of Meiyu front and Meiyu frontal precipitation. There were extreme water vapor conditions in the two periods. In the first stage, the primary convective monomers were triggered by the convergence of the ground wind field. The southwest lowlevel jet showed pulsation. The thickening of the wet layer promoted the development of strong thunderstorm. The new monomers formed in the upper reaches of thunderstorms, and rapidly merged into strong thunderstorm. The backward propagation was one of the important reasons for its stable and moveless. In the strong phase, the strong thunderstorm had the characteristics of warm cloud and low center of mass. The configuration of vertical wind shear in the low layer and the northerly outflow of thunderstorm and the appearance of mesocyclone both promoted the upward movement, causing the long-term maintenance of the strong thunderstorm. It caused high intensity precipitation at Maliang Station for several hours. In the second stage, the line-parallel layer-mean wind component was bigger than the line-perpendicular, which promoted the formation of northeast-southwest parallel stratiform MCS. It had the characteristics of multiple monomers arranged in sequence, and the nascent monomers were continuously generated under the effect of the ground convergence line on the southwest side of the system. Their development made the parallel stratiform MCS enhanced and maintained. The Maliang Station was affected by the parallel stratiform MCS convection line and the northwest side layered echo, and the hourly precipitation was significantly weaker than in the first stage.
    5  Characteristics of Extreme Precipitation Weather Situation and Physical Quantity Anomaly in Central China
    ZHONG Min CHE Qin ZHANG Mengmeng DONG Liangpeng ZHANG Pingping CHEN Xuan
    2020, 46(4):503-516. DOI: 10.7519/j.issn.1000-0526.2020.04.005
    [Abstract](868) [HTML](705) [PDF 14.92 M](1728)
    This paper selects 139 extreme precipitation cases from 1960 to 2012 to study the characteristics of precipitation, weather situation and physical quantity anomaly. The findings indicate that, the extreme precipitation in central China mainly occurs in four different weather situations, namely, the zonal type, the meridional type, the typhoon and cold trough combined type and the short wave trough with warm shear type. The proportions of cases are 42.4%, 30.2%, 17.3% and 10.1%, respectively. The typhoon and cold trough combined type stands on the top in the four types of heavy rain stations, extreme precipitation stations and the extreme rainfall, followed by the zonal type and the meridional type, while the short wave trough with warm shear type is the lowest. The anomaly ratios of low-level water vapor convergence, mid-low-level rising velocity, low-level wind convergence and cyclonic vorticity, high-level wind divergence and atmospheric precipitable water exceeding 50% are the common features of extreme precipitation anomalies. The individual characteristics are that the anomaly ratio of 500 hPa specific humidity in the zonal type is higher, the anomaly ratio of warm advection in the meridional type is higher, the anomaly ratio of 500 hPa positive vorticity advection and specific humidity in the typhoon and cold trough combined type is higher. Moreover, in the short wave trough with warm shear type, the abnormal physical quantity is more concentrated in the boundary layer, and the abnormal proportion of atmospheric precipitable water is low. In addition, besides paying attention to the degree of abnormal physical quantities, the duration of precipitation is also one of the important factors in extreme precipitation prediction.
    6  Statistical Analysis of Track and Intensity Variations of Tropical Cyclone Landing Mainland After Passing Through Taiwan
    XING Rui XU Jing LIN Han
    2020, 46(4):517-527. DOI: 10.7519/j.issn.1000-0526.2020.04.006
    [Abstract](690) [HTML](435) [PDF 1.76 M](1420)
    The track, intensity and structure of the tropical cyclone (TC) in Taiwan Strait become more complex because of the complicated underlying surface and the influence of the middle and low latitude weather system after TC crossing Taiwan. Thus, it is difficult to forecast the precise position and intensity of TC landing mainland. In this paper, the track and intensity variation characteristics of 81 TCs landing Taiwan and mainland from 1949 to 2017 were analyzed, and the TC positions and intensities in the best track datasets 〖JP2〗of Shanghai Typhoon Institute (CMA/STI), American Joint Typhoon Warning Center (JTWC)〖JP〗 and Tokyo Regional Typhoon Center (RSMC-Tokyo) were compared and analyzed. The results show that most of the TCs weakened except that a few strengthened in the strait. The track deflections are obtained in most TCs in strait, compared with tracks of TC before landing Taiwan Island, but the deflection orientations are different in the three best track datasets. It is more difficult to determine the TC center and intensity because the TC structure is broken down when passing through Taiwan Island. As a result, TC center and intensity records are very different in the three best track datasets. The position and intensity uncertainties of TC increase the difficulty in monitoring and forecasting TC track and intensity.
    7  Analysis of Aerosol Optical and Microphysical Properties in Central Part of Huaihe River Basin Based on Remote Sensing Measurement
    FAN Wei QIU Kangjun LING Xinfeng HUANG Yong
    2020, 46(4):528-537. DOI: 10.7519/j.issn.1000-0526.2020.04.007
    [Abstract](584) [HTML](377) [PDF 2.23 M](1225)
    Using the whole year’s sun-sky radiometer CE318 data in 2017 observed by National Climatology Observatory in Shouxian County set by China Meteorological Administration, the aerosol optical and microphysical characteristics in the local area were analyzed. The results show as follows. The aerosol optical depth is the highest in spring, similarly lowest in summer and autumn, and in winter it is between them. AE data are concentrated in the range of 0.9-1.5, mainly in the form of fine mode particles. The aerosol volume size distributions in four seasons are basically similar, and there are both fine and coarse mode particles. The real part of the refraction index of aerosol in summer is the smallest, indicating that the water vapor content in summer is the largest, and the real part has no obvious relation with the wavelength, while the imaginary part has. The single scattering albedo is above 80%, and the scattering effect of aerosol is obvious. Non-spherical particles dominate and are most abundant in spring. These findings have great significance for mastering aerosols characteristics, for researching the atmospheric radiation, climate change and air quality monitoring, and for improving the calculation accuracy of atmospheric radiation transfer model in specific regions in central part of Huaihe River Basin.
    8  Global Major Weather and Climate Events in 2019 and the Possible Causes
    YIN Yizhou LI Duo SUN Shao WANG Guofu KE Zongjian
    2020, 46(4):538-546. DOI: 10.7519/j.issn.1000-0526.2020.04.008
    [Abstract](791) [HTML](329) [PDF 3.74 M](1113)
    The global concentration of major greenhouse gases continued to rise in 2019, and the global average〖JP〗 temperature in 2019 was 1.1 (±0.1)℃ higher than the preindustrial level, being the second warmest year on record. The ocean heat content and sea level height have reached new high levels, while the seaice extent was at a lowlevel. Many significant weather and climate events occurred in 2019, including torrential rains and floods in many places, droughts in Australia and many countries in Asia and Europe, frequent extreme tropical cyclones, unusually high temperature and heat waves in Europe and Australia, cold and heavy snowstorms in North America and Europe, as well as severe convective weather in many regions. The positive phase of the Indian Ocean dipole (IOD), the continuous warming of the sea surface temperature in the equatorial central Pacific and the control of the subtropical high pressure system were the main causes of high temperature and little rain in Australia, resulting in serious forest fires. The continuous heavy rainfall in India from July to August was mainly due to the abnormally strong positive phase of IOD and the tropical depression with unusually long duration.
    9  Climatic Characteristics and Major Meteorological Events over China in 2019
    LI Ying ZENG Hongling WANG Guofu WANG Zunya CHEN Xianyan ZOU Xukai SHI Shuai JIANG Yundi ZHAO Lin ZHOU Bing CUI Tong ZHOU Xingyan SUN Shao WANG Youmin ZHU Xiaojin DAI Tanlong ZHANG Yingxian CAI Wenyue ZHONG Hailing GUO Yanjun LIU Yanju DING Ting ZHI Rong
    2020, 46(4):547-555. DOI: 10.7519/j.issn.1000-0526.2020.04.009
    [Abstract](945) [HTML](940) [PDF 2.88 M](1634)
    The general feature of China’s climate in 2019 was warm and wet. The annual mean temperature was 0.79℃ higher than normal, becoming the fifth warmest year since 1951. The temperatures in all the four seasons were above normal, and obviously warmer in spring and autumn. The annual mean precipitation over China was 645.5 mm with 2.5% above normal. The seasonal precipitations in winter, spring and summer were above normal, but below normal in autumn. The prerainy season in South China started earlier and ended later than normal, resulting in the longest rainy period and the second largest amount of precipitation since 1961. However, the onset and end of the rainy season in Southwest China were both later than the climatological dates, and the precipitation amount was deficient there. The Meiyu season started later but ended earlier than normal, leading to less precipitation during the rainy period. The rainy season in North China started later and ended at the time near normal, so the rainfall was less. Both the autumn rain in West China and the rainy 〖JP2〗season in Northeast China started early but ended late, contributing more rainfall. In 2019, the generated typhoons were more than normal, but the landing typhoons were not so many, of which only “Lekima” brought serious damages. As for other meteorological disasters, such as rainstorm, floods, droughts, severe convection, cold freezing and snow disaster as well as sanddust storms, were all mild relatively.
    10  Overview of Climate Prediction for the Summer 2019 and the Precursory Signals
    DING Ting HAN Rongqing GAO Hui
    2020, 46(4):556-565. DOI: 10.7519/j.issn.1000-0526.2020.04.010
    [Abstract](700) [HTML](682) [PDF 4.45 M](1503)
    In summer 2019, precipitation in south of China was above normal, but below normal in north of China. Much more precipitation was found in Northeast China and the south of the Yangtze River. The precipitation above normal in the south of the Yangtze River, the east of Southwest China, the east of Northeast China, the central part of the Northwest China, and the precipitation below normal in central and northeastern Inner Mongolia were well predicted in March. The updated forecast released in May predicted the main rainy centers in southern China would move southward, and this corrected forecast is more consistent with the observation. The prediction for July-August released in June modified the precipitation prediction trend for Northeast China, and accurately predicted the characteristics〖JP2〗 of much more precipi〖JP〗tation in this region. The predictions on the onset of the South China Sea summer monsoon, the rainy season in Southwest China, Meiyu, and the rainy season in North China were predicted well. However, there were deficiencies in the precipitation prediction in summer 2019. The prediction of precipitation anomaly along the middle and lower reaches of the Yangtze River was wrong. The range and the anomaly degree of the precipitation above normal in Northeast China were underestimated. In addition, this paper preliminarily analyzes the failure of the snow area anomaly of QinghaiTibetan Plateau, the El Ni〖AKn~D〗o event and the tropical Indian Ocean warming in winter 2018-2019 indicating the precipitation anomaly in the middle and lower reaches of the Yangtze River. The externalforcing factors and the associated atmospheric circulation between 2018 and 2019 are compared. It is pointed out that the research on the complexity of the mismatch and asymmetry between the summer precipitation and the traditional impact factors needs to be further carried out.
    11  Features and Possible Causes of the Climatic Anormaly in China in Autumn 2019
    SUN Linhai WANG Yongguang
    2020, 46(4):566-574. DOI: 10.7519/j.issn.1000-0526.2020.04.011
    [Abstract](671) [HTML](181) [PDF 5.43 M](2065)
    During the autumn of 2019, the surface air temperatures were above normal in most areas in China, and it was the third warmest in the same period after 1961. The distribution of precipitation over China was more in the west and north, and less in the east and south of China. By analyzing the causes for the climatic anomaly, we found that in autumn, activities of ridges and troughs in middle and high latitudes of Eurasia were seen frequently, the cold air activity was near normal, and the western Pacific subtropical high (WPSH) was stronger and more northwestward than normal. The western part of WPSH was located over the west of the South China Sea, which was conducive to the southwest water vapor transportation to the western part of China. The northeast 〖JP2〗of the Philippines was under the control of strong cyclonic anomaly〖JP〗 circulation, making the southern part of China controlled by the northerly air flow and resulting in poor water vapor condition. Further studies show that the sea surface temperature (SST) anomaly was the major external forcing factor for the climatic anomalies in the autumn of 2019. In July 2019, the weak central Pacific type El Ni〖AKn~D〗o event ended, and the autumn SST distribution was inclined to the central type. The subtropical circulation in East Asia showed a clear response.
    12  Analysis of January 2020 Atmospheric Circulation and Weather
    JIANG Qi GUI Hailin XU Ran
    2020, 46(4):575-580. DOI: 10.7519/j.issn.1000-0526.2020.04.012
    [Abstract](733) [HTML](883) [PDF 5.26 M](1451)
    The following are the main characteristics of the general circulation of atmosphere in January 2020. There were two polar vortex centers in the Northern Hemisphere. The location of the East Asian trough was more eastward and northward than that in the same period of normal years, and the strength was weak. The monthly mean precipitation (23.3 mm) was 77% above normal, which is the second in January since 1961. The average temperature (-3.6℃) was 1.4℃ higher than in the normal years, and the cold air processes were weak. The foghaze weather in the central and eastern part of China occurred frequently and there were three largescale continuous foghaze processes, respectively in 3-5, 16-18 and 22-28 January. In addition, four precipitation processes appeared in the month.

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