Through analyzing the situation of atmospheric circulation and the variation of meteorological element at the time of dense fog happened on November 10,2005 in Jining,the results indicated that there were abundant wat...Through analyzing the situation of atmospheric circulation and the variation of meteorological element at the time of dense fog happened on November 10,2005 in Jining,the results indicated that there were abundant water vapor,weaker pressure field and wind field,weaker cold air in high altitude,stable stratification in underlying bed and ground was located in the bottom of cold high pressure,all those conditions were beneficial to the generation of dense fog in Jining.展开更多
Using the composite field observational data collected in the area south of the Nanling Mts. and numerical modeling, the seasonal features of dense fog and visibility, fog drop spectrum and physical concept of fog for...Using the composite field observational data collected in the area south of the Nanling Mts. and numerical modeling, the seasonal features of dense fog and visibility, fog drop spectrum and physical concept of fog forming have been analyzed. The occurring frequency of low visibility(≤200 m) is very high with a mean of 24.7%, a maximum of 41.8% from the end of autumn to winter and next spring. The fog processes that occur in the area south of the Nanling Mts. in spring and winter result from the interactions of complicated micro-physical processes, the local terrain, water vapor transportation and the influencing weather system. The fog processes are arisen from advection or windward slope, which is much different from the radiation fog. Cooling condensation due to the air lifted by the local mountain plays an important role in fog formation. Windward slope of the mountain is favorable to the fog formation. Dense fog can occur at lower altitudes in the windward slope of mountain, resulting in the lower visibility. The fog is mainly of small-drop spectrum with smaller number-density than that of urban fog, and its drop spectrum has descending trend in the section of smaller diameter. The inverse relationship between fog water content and visibility is the best among several relationships of micro-variables. In addition to micro-physical processes of fog body itself, the motion of irregular climbing and crossing over hillside while the fog body is being transported by the wind are also important reasons for the fluctuation of micro-physical parameters such as fog water content.展开更多
We use historical materials of monthly foggy days from 84 stations of Shandong Province during the latest decades,analyze the spatial distribution features of mean foggy days during autumn and winter and annual mean f...We use historical materials of monthly foggy days from 84 stations of Shandong Province during the latest decades,analyze the spatial distribution features of mean foggy days during autumn and winter and annual mean foggy days in Shandong.Result shows that foggy weather have strong regional characteristics,there are obvious difference between Shandong inland and coast in terms of the frequency of foggy days,winter and autumn are the peak period of dense fog in the inland of Shandong,however,dense fog is less in coastal area.Take Jinan for example,we have emphatically analyzed the activity change rules of foggy days during autumn and winter since 1952 in the inland,as well as the characteristics of atmospheric circulation during the frequently-occurring year and less frequently-occurring year of dense fog.展开更多
[Objective] The study aimed to discuss the characteristics and forecasting methods of dense fog in Xuzhou City. [Method] Based on the data of dense fog in Xuzhou City from 1960 to 2009, the characteristics and forming...[Objective] The study aimed to discuss the characteristics and forecasting methods of dense fog in Xuzhou City. [Method] Based on the data of dense fog in Xuzhou City from 1960 to 2009, the characteristics and forming conditions of dense fog in the region were analyzed, and then its forecasting methods were introduced, finally corresponding disaster prevention measures were put forward. [ Result] Dense fog might ap- pear in each season, its frequency of occurrence was the highest in December, namely 16.4% ; it was the lowest in June （2.2%）, and the fog las- ted for a short time and was thin. Heavy fog occurred more frequently in winter half year than summer half year, and the frequency of occurrence from October to next February was about 66.7%. In addition, dense fog mostly generated from late midnight to morning, while it appeared less in the afternoon. It shows that dense fog in Xuzhou City is mainly radiation fog instead of advection fog, but the two kinds of fog appeared simultane- ously sometimes. [ Conclusion] The research could provide scientific forecasting methods for the precise prediction of dense fog in Xuzhou City.展开更多
Based on observation data from automatic stations in Lianyungang, visibility and weather situation of dense fog leading to a traffic accident in Lianyungang on April 15, 2012 were analyzed firstly, and then changes of...Based on observation data from automatic stations in Lianyungang, visibility and weather situation of dense fog leading to a traffic accident in Lianyungang on April 15, 2012 were analyzed firstly, and then changes of meteorological factors related to fog appearance and disappearance, such as wind speed, temperature and relative humidity, were discussed. The results showed that wind speed was below 2 m/s when fog occurred, and wind velocity reduced obviously before visibility deceased, appearing a trough. Fog appeared when temperature was neady the minimum, and there was no great change in wind speed, but visibility went up gradually after temperature rose. The longer the duration of the minimum temperature, the longer the duration of the minimum visibility. Moreover, visibility would become low after temperature rose.展开更多
Nonhydrostatic mesoscale WRF and its 3D-Var system are used to study a dense fog event occurring in 13-14 January 2006. Three different observation data sets including GTS （Global Telecommunication System）, AMDAR （...Nonhydrostatic mesoscale WRF and its 3D-Var system are used to study a dense fog event occurring in 13-14 January 2006. Three different observation data sets including GTS （Global Telecommunication System）, AMDAR （Aircraft Meteorological Data Relay） data, and 9210 data are assimilated into the initial analysis fields in experiments. Experiments with three different assimilation time intervals （1, 3, and 6 h） are also carried out. Three experiments with different data sets have all modified the temperature and humidity field of initial fields, and therefore show an obvious positive effect on fog simulation. Further study indicates that the humidity and stability of boundary layer are improved obviously in assimilation experiments, although different data sets make different contribution to the analysis fields. The multi-time assimilation cycle experiments show that the analysis increment in experiment with l-h interval is more realistic than that with 3- and 6-h intervals.展开更多
An extremely dense radiation fog event during 10-11 December 2007 was studied to understand its macro-micro-physics in relation to dynamic and thermodynamic structures of the boundary layer, as well as its structural ...An extremely dense radiation fog event during 10-11 December 2007 was studied to understand its macro-micro-physics in relation to dynamic and thermodynamic structures of the boundary layer, as well as its structural evolution in conjunction with the air-surface exchange of heat and water vapor. The findings are as follows. The extreme radiation fog process was divisible into formation, development, mature, and dissipation phases, depending on microstructure and visibility. This fog event was marked by rapid evolution that occurred after sunrise, when enhanced surface evaporation and cold air intrusion led to a three order of magnitude increase in liquid water content （LWC） in just 20 minutes. The maximum droplet diameter （MDD） increased four-fold during the same period. The fog structure was two-layered, with the top of both the surface-layer and upper-layer components characterized by strong temperature and humidity inversions, and low-level jets existed in the boundary layer above each fog layer. Turbulence intensity, turbulent kinetic energy, and friction velocity differed remarkably from phase to phase： these features increased gradually before the fog formation and decreased during the development phase; during the mature and dissipation phases these characteristics increased and then decreased again. In the development and mature stages, the mean kinetic energy of the lower-level winds decreased pronouncedly, both in the horizontal and vertical directions.展开更多
Based on conventional observation data and NCEP reanalysis data at 10 national basic stations and reference stations of Shaoyang City during 1951-2014,300 cases of typical regional dense fog process appeared in the hi...Based on conventional observation data and NCEP reanalysis data at 10 national basic stations and reference stations of Shaoyang City during 1951-2014,300 cases of typical regional dense fog process appeared in the history were selected. From meteorological factors and weather situation,temporal-spatial distribution characteristics and trend change characteristics of dense fog in Shaoyang were analyzed. The results showed that（ 1） temporal-spatial distribution of dense fog in Shaoyang region was uneven,and interannual variability of fog days had large volatility and bad periodicity; dense fog days in Shaoyang region was obviously more in winter half year and less in summer half year. Dense fog was the most in November and the least in July. Dense fog mostly concentrated during 03： 00-09： 00; appearance time mostly concentrated during 05： 00-07： 30,and dissipation time mostly appeared after 08： 30. Dense fog appeared early and dissipated late in winter half year,and vice verse in summer half year.（ 2） Seen from meteorological factors,ground and 850 h Pa of wind velocity was generally 0-3 m/s,which was all small. Moreover,there existed temperature inversion from ground to 850 h Pa. Relative humidity on dense fog day was larger,and precipitation or cloudy day mostly appeared in prior day.（ 3） There were four kinds of ground weather situation forming dense fog： uniform pressure field type,cold and high pressure bottom type,cold and high pressure rear type,frontal type. Based on grasping change characteristics,rule and formation reason of dense fog,some forecast focus was found.展开更多
文摘Through analyzing the situation of atmospheric circulation and the variation of meteorological element at the time of dense fog happened on November 10,2005 in Jining,the results indicated that there were abundant water vapor,weaker pressure field and wind field,weaker cold air in high altitude,stable stratification in underlying bed and ground was located in the bottom of cold high pressure,all those conditions were beneficial to the generation of dense fog in Jining.
基金Research on the physical structure and visibility of heavy fog in the mountainous region of Nan Ling Mts., a project from the Natural Science Foundation of China (49975001)
文摘Using the composite field observational data collected in the area south of the Nanling Mts. and numerical modeling, the seasonal features of dense fog and visibility, fog drop spectrum and physical concept of fog forming have been analyzed. The occurring frequency of low visibility(≤200 m) is very high with a mean of 24.7%, a maximum of 41.8% from the end of autumn to winter and next spring. The fog processes that occur in the area south of the Nanling Mts. in spring and winter result from the interactions of complicated micro-physical processes, the local terrain, water vapor transportation and the influencing weather system. The fog processes are arisen from advection or windward slope, which is much different from the radiation fog. Cooling condensation due to the air lifted by the local mountain plays an important role in fog formation. Windward slope of the mountain is favorable to the fog formation. Dense fog can occur at lower altitudes in the windward slope of mountain, resulting in the lower visibility. The fog is mainly of small-drop spectrum with smaller number-density than that of urban fog, and its drop spectrum has descending trend in the section of smaller diameter. The inverse relationship between fog water content and visibility is the best among several relationships of micro-variables. In addition to micro-physical processes of fog body itself, the motion of irregular climbing and crossing over hillside while the fog body is being transported by the wind are also important reasons for the fluctuation of micro-physical parameters such as fog water content.
文摘We use historical materials of monthly foggy days from 84 stations of Shandong Province during the latest decades,analyze the spatial distribution features of mean foggy days during autumn and winter and annual mean foggy days in Shandong.Result shows that foggy weather have strong regional characteristics,there are obvious difference between Shandong inland and coast in terms of the frequency of foggy days,winter and autumn are the peak period of dense fog in the inland of Shandong,however,dense fog is less in coastal area.Take Jinan for example,we have emphatically analyzed the activity change rules of foggy days during autumn and winter since 1952 in the inland,as well as the characteristics of atmospheric circulation during the frequently-occurring year and less frequently-occurring year of dense fog.
基金Supported by Special Fund for Forecasters of Jiangsu Provincial Meteorological Bureau (Study on the Forecasting Model of Dense Fog in Xuzhou City Based on SVM Method)
文摘[Objective] The study aimed to discuss the characteristics and forecasting methods of dense fog in Xuzhou City. [Method] Based on the data of dense fog in Xuzhou City from 1960 to 2009, the characteristics and forming conditions of dense fog in the region were analyzed, and then its forecasting methods were introduced, finally corresponding disaster prevention measures were put forward. [ Result] Dense fog might ap- pear in each season, its frequency of occurrence was the highest in December, namely 16.4% ; it was the lowest in June （2.2%）, and the fog las- ted for a short time and was thin. Heavy fog occurred more frequently in winter half year than summer half year, and the frequency of occurrence from October to next February was about 66.7%. In addition, dense fog mostly generated from late midnight to morning, while it appeared less in the afternoon. It shows that dense fog in Xuzhou City is mainly radiation fog instead of advection fog, but the two kinds of fog appeared simultane- ously sometimes. [ Conclusion] The research could provide scientific forecasting methods for the precise prediction of dense fog in Xuzhou City.
基金Supported by the Meteorological Funds for Distinguished YoungScholars in Jiangsu Province,China(Q201104)Special Project for Forecasters in Jiangsu Meteorological Bureau(JSYBY201308)+2 种基金Project of Lianyungang Bureau of Science and Technology(SH1013)Project of Jiangsu Department of Science and Technology(BE2011720)Social Development Projects of Lianyungang Meteorological Bureau(LG200804,LG201205,LG201108,LG201106,LG201002)
文摘Based on observation data from automatic stations in Lianyungang, visibility and weather situation of dense fog leading to a traffic accident in Lianyungang on April 15, 2012 were analyzed firstly, and then changes of meteorological factors related to fog appearance and disappearance, such as wind speed, temperature and relative humidity, were discussed. The results showed that wind speed was below 2 m/s when fog occurred, and wind velocity reduced obviously before visibility deceased, appearing a trough. Fog appeared when temperature was neady the minimum, and there was no great change in wind speed, but visibility went up gradually after temperature rose. The longer the duration of the minimum temperature, the longer the duration of the minimum visibility. Moreover, visibility would become low after temperature rose.
基金Supported by the Ministry of Science and Technology of PRC under Contracts 2006BAC02B01National Natural Science Foundation of China under Grand Nos.40675022 and 60572184.
文摘Nonhydrostatic mesoscale WRF and its 3D-Var system are used to study a dense fog event occurring in 13-14 January 2006. Three different observation data sets including GTS （Global Telecommunication System）, AMDAR （Aircraft Meteorological Data Relay） data, and 9210 data are assimilated into the initial analysis fields in experiments. Experiments with three different assimilation time intervals （1, 3, and 6 h） are also carried out. Three experiments with different data sets have all modified the temperature and humidity field of initial fields, and therefore show an obvious positive effect on fog simulation. Further study indicates that the humidity and stability of boundary layer are improved obviously in assimilation experiments, although different data sets make different contribution to the analysis fields. The multi-time assimilation cycle experiments show that the analysis increment in experiment with l-h interval is more realistic than that with 3- and 6-h intervals.
基金supported jointly by the Key Project of Natural Science Foundation of Jiangsu Province under Grant No BK2007727the Scientific Project for Public Welfare specific to Meteo rologists (GYHY200706026, GYHY200906012)+1 种基金Qinglan Project "cloud fog precipitation and aerosol research innovation group"the National Natural Science Foundation of China (Grant Nos 40775012, 40975085, and 40775010)
文摘An extremely dense radiation fog event during 10-11 December 2007 was studied to understand its macro-micro-physics in relation to dynamic and thermodynamic structures of the boundary layer, as well as its structural evolution in conjunction with the air-surface exchange of heat and water vapor. The findings are as follows. The extreme radiation fog process was divisible into formation, development, mature, and dissipation phases, depending on microstructure and visibility. This fog event was marked by rapid evolution that occurred after sunrise, when enhanced surface evaporation and cold air intrusion led to a three order of magnitude increase in liquid water content （LWC） in just 20 minutes. The maximum droplet diameter （MDD） increased four-fold during the same period. The fog structure was two-layered, with the top of both the surface-layer and upper-layer components characterized by strong temperature and humidity inversions, and low-level jets existed in the boundary layer above each fog layer. Turbulence intensity, turbulent kinetic energy, and friction velocity differed remarkably from phase to phase： these features increased gradually before the fog formation and decreased during the development phase; during the mature and dissipation phases these characteristics increased and then decreased again. In the development and mature stages, the mean kinetic energy of the lower-level winds decreased pronouncedly, both in the horizontal and vertical directions.
文摘Based on conventional observation data and NCEP reanalysis data at 10 national basic stations and reference stations of Shaoyang City during 1951-2014,300 cases of typical regional dense fog process appeared in the history were selected. From meteorological factors and weather situation,temporal-spatial distribution characteristics and trend change characteristics of dense fog in Shaoyang were analyzed. The results showed that（ 1） temporal-spatial distribution of dense fog in Shaoyang region was uneven,and interannual variability of fog days had large volatility and bad periodicity; dense fog days in Shaoyang region was obviously more in winter half year and less in summer half year. Dense fog was the most in November and the least in July. Dense fog mostly concentrated during 03： 00-09： 00; appearance time mostly concentrated during 05： 00-07： 30,and dissipation time mostly appeared after 08： 30. Dense fog appeared early and dissipated late in winter half year,and vice verse in summer half year.（ 2） Seen from meteorological factors,ground and 850 h Pa of wind velocity was generally 0-3 m/s,which was all small. Moreover,there existed temperature inversion from ground to 850 h Pa. Relative humidity on dense fog day was larger,and precipitation or cloudy day mostly appeared in prior day.（ 3） There were four kinds of ground weather situation forming dense fog： uniform pressure field type,cold and high pressure bottom type,cold and high pressure rear type,frontal type. Based on grasping change characteristics,rule and formation reason of dense fog,some forecast focus was found.
