ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 44,Issue 5,2018 Table of Contents
2018, 44(5):597-611.
DOI: 10.7519/j.issn.1000-0526.2018.05.001
Abstract:
In this paper, observations from CloudSat satellite dataset from 2012 to 2014 are used to analyze the vertical structure and microphysical features of typhoon cloud in western Pacific with the six kinds of intensities and radial distances from the center. The main conclusions are summarized as follows: (1) The occurrence frequency of singlelayer cloud dominates and doublelayer cloud is relatively more common in the multilayer cloud. With the increasing intensity of typhoon, the singlelayer cloud is thicker inside the radial distance 250 km, but thinner and mostly concentrated in the range of 7-15 km out of the radial distance 450 km. Similarly, the bottom and top layer clouds of doublelayer are thicker, the distance between them is narrow inside the 250 km range, and the feature out of the 450 km range is inversed. (2) The occurrence frequencies of deep convective clouds, cirrus, and altostratus are higher, compared to other clouds, the distributions have obvious changes with the changes of typhoon intensities and the radial distance. (3) The radar reflectivity becomes stronger above the 5 km in the stage of mature typhoon. Meanwhile, there are obvious columnar radar reflectivity areas out of 450 km. (4) The liquid water and ice water contents near the center of typhoon are increased with the change of typhoon intensities. In addition, the high value area of ice water content is always concentrated near 10 km in the outer cloud bands. The distribution of liquid droplet number concentration is consistent with the liquid water content. However, the high value area of ice water content is below the high area of ice droplet number concentration.
In this paper, observations from CloudSat satellite dataset from 2012 to 2014 are used to analyze the vertical structure and microphysical features of typhoon cloud in western Pacific with the six kinds of intensities and radial distances from the center. The main conclusions are summarized as follows: (1) The occurrence frequency of singlelayer cloud dominates and doublelayer cloud is relatively more common in the multilayer cloud. With the increasing intensity of typhoon, the singlelayer cloud is thicker inside the radial distance 250 km, but thinner and mostly concentrated in the range of 7-15 km out of the radial distance 450 km. Similarly, the bottom and top layer clouds of doublelayer are thicker, the distance between them is narrow inside the 250 km range, and the feature out of the 450 km range is inversed. (2) The occurrence frequencies of deep convective clouds, cirrus, and altostratus are higher, compared to other clouds, the distributions have obvious changes with the changes of typhoon intensities and the radial distance. (3) The radar reflectivity becomes stronger above the 5 km in the stage of mature typhoon. Meanwhile, there are obvious columnar radar reflectivity areas out of 450 km. (4) The liquid water and ice water contents near the center of typhoon are increased with the change of typhoon intensities. In addition, the high value area of ice water content is always concentrated near 10 km in the outer cloud bands. The distribution of liquid droplet number concentration is consistent with the liquid water content. However, the high value area of ice water content is below the high area of ice droplet number concentration.
2018, 44(5):612-620.
DOI: 10.7519/j.issn.1000-0526.2018.05.002
Abstract:
Based on the 0.5° reanalysis data of National Centers for Environmental Prediction (NCEP) and typhoon best track data from China Meteorological Administration-Shanghai Typhoon Institute (CMA-STI), the warm-core structure of upper level in typhoons making landfall in China during 1979-2010 are diagnosed. The results of this study are shown as follows. (1) The intensity of landing typhoon cases always strengthens at the moment of 18 h before landing. (2) The structure of warm-core shows a remarkable asymmetry during landing, and the area of the onshore part is more remarkable. In the coastline region before landing, the warm-core structure is slightly asymmetrical in both left and right sides. And the left half of landing typhoons will go on developing until landing, and vice versa. (3) The distribution of warm-core temperature gradient is non-uniform. The closer to the periphery, the bigger the temperature gradient is. And in the inner core area, the temperature gradient is much smaller. When the intensity of warm-core changes, the change rate of central temperature is increased. (4) The warm-core intensity would decay more tempestuously in vertical direction in the landing process. (5) The several calculation methods proposed in this paper for the typhoon warm-core feature are relatively simple, and the physical meaning is very clear as well. When data is not complete or computational time requirements of operational forecast is higher, it can provide relatively better quantified reference, and especially help understand the relationship between typhoon warm-core structure and variation of typhoon intensity. Thus, it could have practical application values.
Based on the 0.5° reanalysis data of National Centers for Environmental Prediction (NCEP) and typhoon best track data from China Meteorological Administration-Shanghai Typhoon Institute (CMA-STI), the warm-core structure of upper level in typhoons making landfall in China during 1979-2010 are diagnosed. The results of this study are shown as follows. (1) The intensity of landing typhoon cases always strengthens at the moment of 18 h before landing. (2) The structure of warm-core shows a remarkable asymmetry during landing, and the area of the onshore part is more remarkable. In the coastline region before landing, the warm-core structure is slightly asymmetrical in both left and right sides. And the left half of landing typhoons will go on developing until landing, and vice versa. (3) The distribution of warm-core temperature gradient is non-uniform. The closer to the periphery, the bigger the temperature gradient is. And in the inner core area, the temperature gradient is much smaller. When the intensity of warm-core changes, the change rate of central temperature is increased. (4) The warm-core intensity would decay more tempestuously in vertical direction in the landing process. (5) The several calculation methods proposed in this paper for the typhoon warm-core feature are relatively simple, and the physical meaning is very clear as well. When data is not complete or computational time requirements of operational forecast is higher, it can provide relatively better quantified reference, and especially help understand the relationship between typhoon warm-core structure and variation of typhoon intensity. Thus, it could have practical application values.
2018, 44(5):621-633.
DOI: 10.7519/j.issn.1000-0526.2018.05.003
Abstract:
To improve the effect of the numerical simulation and forecasting of heavy rains, it is very important to introduce the meso- and small-scale information in the assimilation analysis of initial values. For enhancing the introduction of meso- and small-scale information in the regional GRAPES 3Dvar system, climatic background error sample was used in this paper to estimate the level covariate correlation scale of variable error, and then statistical result fitting was performed with recursive filter of the feature scales of three different levels, thus replacing the original single-scaled recursive filtering. The new scheme was used to assimilate and forecast the rainstorms in the Jianghan Plain during 1-2 June, 2015, and the research results showed that power spectrum attenuation in the new scheme is slower. Through single point test and field analysis, we found that the new assimilation scheme introduces more meso-α scale information. In the report of the rainstorm, it was found that, with the adoption of the new scheme, the moisture field, divergence field and vorticity field are much closer to the observation values when measured in the analysis field and forecasting field. So the precipitation forecasting skill is improved obviously. By analyzing the energy spectrum, it was learned that the new scheme could reflect more meso-α scale information and the new scheme has positive effect on the forecasting of rainstorms in the Jianghan Plain area. In meso-α scale, there are some favorable factors for rainfall, such as lower convergence, upper divergence and increased humidity. Based on individual cases of rainstorm, batch experiments for 16 days were completed, and the result showed that the new scheme could improve precipitation forecasting skill, which is consistent with the results of cases study.
To improve the effect of the numerical simulation and forecasting of heavy rains, it is very important to introduce the meso- and small-scale information in the assimilation analysis of initial values. For enhancing the introduction of meso- and small-scale information in the regional GRAPES 3Dvar system, climatic background error sample was used in this paper to estimate the level covariate correlation scale of variable error, and then statistical result fitting was performed with recursive filter of the feature scales of three different levels, thus replacing the original single-scaled recursive filtering. The new scheme was used to assimilate and forecast the rainstorms in the Jianghan Plain during 1-2 June, 2015, and the research results showed that power spectrum attenuation in the new scheme is slower. Through single point test and field analysis, we found that the new assimilation scheme introduces more meso-α scale information. In the report of the rainstorm, it was found that, with the adoption of the new scheme, the moisture field, divergence field and vorticity field are much closer to the observation values when measured in the analysis field and forecasting field. So the precipitation forecasting skill is improved obviously. By analyzing the energy spectrum, it was learned that the new scheme could reflect more meso-α scale information and the new scheme has positive effect on the forecasting of rainstorms in the Jianghan Plain area. In meso-α scale, there are some favorable factors for rainfall, such as lower convergence, upper divergence and increased humidity. Based on individual cases of rainstorm, batch experiments for 16 days were completed, and the result showed that the new scheme could improve precipitation forecasting skill, which is consistent with the results of cases study.
2018, 44(5):634-644.
DOI: 10.7519/j.issn.1000-0526.2018.05.004
Abstract:
By using the precipitation data of the US Global Precipitation Climate Center (GPCC) and the outputs of six Chinese climate models ［BCC_CSM1.1, BCC_CSM1.1(m), BNU-ESM model, FGOALS-s2, FGOALS-g2 and FIO-ESM］ participating in the historical simulations of Coupled Model Intercomparison Project Phase 5 (CMIP5) as well as the methods featuring the relative and absolute magnitudes of precipitation variability, this paper evaluated the capabilities of the six models quantitatively to capture the interannual and interdecadal variations of global precipitation. The research results showed that the interannual variance of observational precipitation generally accounts for 65%-80% of the total variance, and the interdecadal variance accounts for 10%-35% of the total variance. In the CMIP5 simulations, the interannual variance of the ensemble mean precipitation of the six models is generally stronger than observation, accounting for over 70% of the total variance, while the variance of the interdecadal component contributes less to the total variance (about 10%-20%). Compared with observation, the variability of the globally averaged total, interannual and interdecadal precipitations were underestimated, the contribution of interannual precipitation to total precipitation was overestimated, and the contribution of interdecadal precipitation to total precipitation was underestimated by the models. The interdecadal precipitation in East Asia and Australia was well simulated by the six models, and the ratio between simulated and observed interdecadal precipitation variance is about 1. For Africa, South America and Maritime Continent areas, the simulated interdecadal precipitation variability of BCC_CSM1.1 model is the closest to observation, and for Eurasia and North America, the simulated interdecadal precipitation variability of BNU-ESM model is also close to observation. In Eurasia, the ratio between interannual and interdecadal precipitation variances simulated by BCC_CSM1.1 model is the closest to observation, so did the FGOALS-s2 model in Africa and America. The results of this study would help to understand the current simulation ability of the six Chinese climate models and to improve the models in the future.
By using the precipitation data of the US Global Precipitation Climate Center (GPCC) and the outputs of six Chinese climate models ［BCC_CSM1.1, BCC_CSM1.1(m), BNU-ESM model, FGOALS-s2, FGOALS-g2 and FIO-ESM］ participating in the historical simulations of Coupled Model Intercomparison Project Phase 5 (CMIP5) as well as the methods featuring the relative and absolute magnitudes of precipitation variability, this paper evaluated the capabilities of the six models quantitatively to capture the interannual and interdecadal variations of global precipitation. The research results showed that the interannual variance of observational precipitation generally accounts for 65%-80% of the total variance, and the interdecadal variance accounts for 10%-35% of the total variance. In the CMIP5 simulations, the interannual variance of the ensemble mean precipitation of the six models is generally stronger than observation, accounting for over 70% of the total variance, while the variance of the interdecadal component contributes less to the total variance (about 10%-20%). Compared with observation, the variability of the globally averaged total, interannual and interdecadal precipitations were underestimated, the contribution of interannual precipitation to total precipitation was overestimated, and the contribution of interdecadal precipitation to total precipitation was underestimated by the models. The interdecadal precipitation in East Asia and Australia was well simulated by the six models, and the ratio between simulated and observed interdecadal precipitation variance is about 1. For Africa, South America and Maritime Continent areas, the simulated interdecadal precipitation variability of BCC_CSM1.1 model is the closest to observation, and for Eurasia and North America, the simulated interdecadal precipitation variability of BNU-ESM model is also close to observation. In Eurasia, the ratio between interannual and interdecadal precipitation variances simulated by BCC_CSM1.1 model is the closest to observation, so did the FGOALS-s2 model in Africa and America. The results of this study would help to understand the current simulation ability of the six Chinese climate models and to improve the models in the future.
2018, 44(5):645-654.
DOI: 10.7519/j.issn.1000-0526.2018.05.005
Abstract:
Based on the NCEP/NCAR reanalysis data, conventional observation data, Doppler radar data, meteorological satellite data and ground lightning observation data, the synoptic causes and the mesoscale weather system characteristics of a severe convective rainstorm which occurred in Yunnan on 6 June 2014 are investigated. The results indicate that the forward-tilted trough at 500 hPa, the shear line at 700 hPa and the ground cold front were the crucial synoptic scale systems in this case. High energy and high humidity convective unstable stratification, and obviously vertical wind direction shear were the favorable conditions for the formation of severe convective weather. Many meso-β scale convective systems occurred and developed in the Q vector convergence field. Short-time heavy rainfall often appears around the area with the densest black body temperature (TBB) contour by the side of meso-β scale convective systems moving direction. The variation of rainfall intensity is closely related to the variation of TBB contour gradient. By analyzing the Doppler radar and ground lightning data, we found that meso-γ scale convective system was the direct influence system for the severe convective rainstorm in this case. Thunderstorm usually occurs in area where the echo intensity is between 35-45 dBz and the echo height is more than 10 km. The mesoscale convergence line and the densest negative lightning flash area near the second kind of meso-γ scale convergence zone correspond to short-time heavy rainfall and thunderstorm weather.
Based on the NCEP/NCAR reanalysis data, conventional observation data, Doppler radar data, meteorological satellite data and ground lightning observation data, the synoptic causes and the mesoscale weather system characteristics of a severe convective rainstorm which occurred in Yunnan on 6 June 2014 are investigated. The results indicate that the forward-tilted trough at 500 hPa, the shear line at 700 hPa and the ground cold front were the crucial synoptic scale systems in this case. High energy and high humidity convective unstable stratification, and obviously vertical wind direction shear were the favorable conditions for the formation of severe convective weather. Many meso-β scale convective systems occurred and developed in the Q vector convergence field. Short-time heavy rainfall often appears around the area with the densest black body temperature (TBB) contour by the side of meso-β scale convective systems moving direction. The variation of rainfall intensity is closely related to the variation of TBB contour gradient. By analyzing the Doppler radar and ground lightning data, we found that meso-γ scale convective system was the direct influence system for the severe convective rainstorm in this case. Thunderstorm usually occurs in area where the echo intensity is between 35-45 dBz and the echo height is more than 10 km. The mesoscale convergence line and the densest negative lightning flash area near the second kind of meso-γ scale convergence zone correspond to short-time heavy rainfall and thunderstorm weather.
LI Hongbin
,
FU Yu
,
ZHANG Jingxuan
,
HE Yang
,
PU Wenyao
,
XIA Wei
,
ZHAO Fansheng
,
ZHOU Deping
,
ZHANG Diangang
2018, 44(5):655-664.
DOI: 10.7519/j.issn.1000-0526.2018.05.006
Abstract:
Precipitation (5 mm) characteristics and NCEP/NCAR reanalysis data of a pollution process in Dalian on 16 November 2015 were analyzed. The results showed that the synoptic situation was the typical highlevel trough before the precipitation in Dalian in autumn and winter. The atmospheric stratifications were stable with inversion layers during the early stage of pollution and the late stage of precipitation. There was ascending motion before the precipitation for more than 10 hours, which means the fine particles (PM2.5) around the surface could be transported into the upper air continually with the rising air, and part of the particles would transform into ice nuclei as supplement of ice nucleus in the precipitating cloud. In addition, three more processes of precipitation (<5 mm) in Dalian in autumn and winter during 2015-2016 were analyzed. Cloud liquid water content, amount of precipitation and concentration of fine particles (PM2.5) were discussed in detail. The results showed that there are less ice nuclei leading to smaller rainfall with low concentration of PM2.5, which is suitable for artificial precipitation operation to increase the ice nuclei in clouds and the surface precipitation. Otherwise, there are more or overdosed ice nuclei leading to sufficient precipitation or lower precipitation with high concentration of PM2.5, especially during the air pollution episode. In such cases during artificial precipitation operation working dose or times should be reduced according to the actual situation. Comprehensive analysis also showed that there are two kinds of pollution sources in Dalian. One is local source, and the other is external source. A certain amount of precipitation could reduce pollution through wet deposition by local source, with no obvious effect by external source.
Precipitation (5 mm) characteristics and NCEP/NCAR reanalysis data of a pollution process in Dalian on 16 November 2015 were analyzed. The results showed that the synoptic situation was the typical highlevel trough before the precipitation in Dalian in autumn and winter. The atmospheric stratifications were stable with inversion layers during the early stage of pollution and the late stage of precipitation. There was ascending motion before the precipitation for more than 10 hours, which means the fine particles (PM2.5) around the surface could be transported into the upper air continually with the rising air, and part of the particles would transform into ice nuclei as supplement of ice nucleus in the precipitating cloud. In addition, three more processes of precipitation (<5 mm) in Dalian in autumn and winter during 2015-2016 were analyzed. Cloud liquid water content, amount of precipitation and concentration of fine particles (PM2.5) were discussed in detail. The results showed that there are less ice nuclei leading to smaller rainfall with low concentration of PM2.5, which is suitable for artificial precipitation operation to increase the ice nuclei in clouds and the surface precipitation. Otherwise, there are more or overdosed ice nuclei leading to sufficient precipitation or lower precipitation with high concentration of PM2.5, especially during the air pollution episode. In such cases during artificial precipitation operation working dose or times should be reduced according to the actual situation. Comprehensive analysis also showed that there are two kinds of pollution sources in Dalian. One is local source, and the other is external source. A certain amount of precipitation could reduce pollution through wet deposition by local source, with no obvious effect by external source.
2018, 44(5):665-675.
DOI: 10.7519/j.issn.1000-0526.2018.05.007
Abstract:
In contrast to the new generation weather radar, dual-polarization weather radar can transmit both of horizontal and vertical electromagnetic waves, and collect more information to differentiate between precipitation and non-precipitation radar echoes. Identifying and removing non-precipitation echoes in radar reflectivity fields are one critical step in radar-based quantitative precipitation estimation. In this paper, according to the observed variables and characteristics of non-precipitation, an algorithm of quality control for S-band polarization weather radar data is developed, tested and evaluated by employing the WSR-88D polarization weather radar in Shanghai. The results demonstrate that the algorithm could identify more than 93% non-precipitation, and the precipitation echo error is only 3.82%.
In contrast to the new generation weather radar, dual-polarization weather radar can transmit both of horizontal and vertical electromagnetic waves, and collect more information to differentiate between precipitation and non-precipitation radar echoes. Identifying and removing non-precipitation echoes in radar reflectivity fields are one critical step in radar-based quantitative precipitation estimation. In this paper, according to the observed variables and characteristics of non-precipitation, an algorithm of quality control for S-band polarization weather radar data is developed, tested and evaluated by employing the WSR-88D polarization weather radar in Shanghai. The results demonstrate that the algorithm could identify more than 93% non-precipitation, and the precipitation echo error is only 3.82%.
2018, 44(5):676-683.
DOI: 10.7519/j.issn.1000-0526.2018.05.008
Abstract:
Based on the visibility observation data from meteorological stations in China during 1980-2014 and the community economy and traffic disaster data of China, the index system and corresponding weight of low visibility disasters risk assessment on highway in China are established by using the methods of analytic hierarchy process (AHP), expert scoring and entropy weight. And the region division of low visibility risk is also carried out. The results indicate that the highways in eastern China, northern Xinjiang and south of the Xinjiang Basin are in high risk of low visibility disaster, while those in midwest of China are in low risk. Using the method of AHP to do the risk assessment of low visibility on highway could reduce the influence of subjective factors effectively and make the assessment result more scientific and reasonable.
Based on the visibility observation data from meteorological stations in China during 1980-2014 and the community economy and traffic disaster data of China, the index system and corresponding weight of low visibility disasters risk assessment on highway in China are established by using the methods of analytic hierarchy process (AHP), expert scoring and entropy weight. And the region division of low visibility risk is also carried out. The results indicate that the highways in eastern China, northern Xinjiang and south of the Xinjiang Basin are in high risk of low visibility disaster, while those in midwest of China are in low risk. Using the method of AHP to do the risk assessment of low visibility on highway could reduce the influence of subjective factors effectively and make the assessment result more scientific and reasonable.
9 Research on Relationship Between Highway Traffic Blocking Induced by Waterlogging and Precipitation
2018, 44(5):684-691.
DOI: 10.7519/j.issn.1000-0526.2018.05.009
Abstract:
Based on the 2011-2013 official records of nationwide highway traffic blocking induced by surface water, this study analyzes the spatiotemporal characteristics of highway traffic blocking induced by waterlogging, and investigates the correlation between highway waterlogging and precipitation in different durations. From the aspect of time, the yearly blocking is mainly recorded from May to September, especially in July; the daily blocking mainly occurs in 07:00-14:00, and next in 16:00-20:00. The highway waterlogging blocking is highly related to the precipitation in the latest 24 h, and the correlation between the highway traffic blocking by waterbogging and rainfall with different intensities varies among the regions. The correlation between the precipitation factor after dealing with cube root and the frequency of highway traffic blocking by waterlogging accords with the Gaussian distribution. From the aspect of space, the concerned blocking in Region 1 is closely related to hourly maximum precipitation factor with correlation coefficient over 0.91; the ones in Region 2 and Region 3 are closely related to 6 h maximum precipitation factor with correlation coefficient over 0.8; and the ones in Region 4 are closely related to 24 h maximum precipitation factor with correlation coefficient about 0.75. However, no matter in which region the highway traffic blocking induced by waterlogging occurs, the characteristics of precipitation are greatly different, so we can only estimate the risk probability of highway traffic blocking induced by waterlogging from the specific precipitation forecast.
Based on the 2011-2013 official records of nationwide highway traffic blocking induced by surface water, this study analyzes the spatiotemporal characteristics of highway traffic blocking induced by waterlogging, and investigates the correlation between highway waterlogging and precipitation in different durations. From the aspect of time, the yearly blocking is mainly recorded from May to September, especially in July; the daily blocking mainly occurs in 07:00-14:00, and next in 16:00-20:00. The highway waterlogging blocking is highly related to the precipitation in the latest 24 h, and the correlation between the highway traffic blocking by waterbogging and rainfall with different intensities varies among the regions. The correlation between the precipitation factor after dealing with cube root and the frequency of highway traffic blocking by waterlogging accords with the Gaussian distribution. From the aspect of space, the concerned blocking in Region 1 is closely related to hourly maximum precipitation factor with correlation coefficient over 0.91; the ones in Region 2 and Region 3 are closely related to 6 h maximum precipitation factor with correlation coefficient over 0.8; and the ones in Region 4 are closely related to 24 h maximum precipitation factor with correlation coefficient about 0.75. However, no matter in which region the highway traffic blocking induced by waterlogging occurs, the characteristics of precipitation are greatly different, so we can only estimate the risk probability of highway traffic blocking induced by waterlogging from the specific precipitation forecast.
2018, 44(5):692-698.
DOI: 10.7519/j.issn.1000-0526.2018.05.010
Abstract:
The high quality of meteorological graphic products is important for the public meteorological service (PMS) in the time of media convergence. Based on the techniques of parallel computing and big data, message-driven making system of meteorological graphic products was developed, namely WeatherStudio. After analyzing the common problems of making graphical products for PMS, this paper discussed the advantages of the message-driven product making system, and then focused on the overall structure and main functions of WeatherStudio based on the message and timing driven techniques. Finally, the application of WeatherStudio in the expressway meteorological disaster risk early warning service shows its potential prospect.
The high quality of meteorological graphic products is important for the public meteorological service (PMS) in the time of media convergence. Based on the techniques of parallel computing and big data, message-driven making system of meteorological graphic products was developed, namely WeatherStudio. After analyzing the common problems of making graphical products for PMS, this paper discussed the advantages of the message-driven product making system, and then focused on the overall structure and main functions of WeatherStudio based on the message and timing driven techniques. Finally, the application of WeatherStudio in the expressway meteorological disaster risk early warning service shows its potential prospect.
2018, 44(5):699-703.
DOI: 10.7519/j.issn.1000-0526.2018.05.011
Abstract:
Based on the daily and hourly precipitation data of 2341 meteorological observation stations from 1961 to 2016, this paper analyzed the precipitation extreme features in China in the 2016 flood season and also did comparison with the situation in 1998. The main results are as follows. The average precipitation in 2016 is the most since 1961, and the accumulated rainfall of 140 stations exceeded historical records, with 112 stations having the second historical maximum values. These stations are 54 and 47 more respectively than the stations in 1998. The extreme precipitation in 1998 mainly occurred in Northeast China and the middle and upper reaches of the Yangtze River, but in 2016 it occurred mainly in East China and was more concentrated. Totally, 6972 stations had torrential rains, of which extremely heavy rains occurred at 1251 stations, which are the most since 1961. The largescale torrential rains happened 44 times, lasting for 90 days and showing the characteristics of being intense in middle, and weak before and after the torrential rain processes. There were extreme events of daily precipitation at 417 stations, of which 88 stations broke the historic records. The hourly maximum precipitation at 113 stations broke the historical records, with 29 stations more than in 1998. The spatial distribution of daily precipitation extremes was mainly in East China and North China in 2016, but in central China in 1998. The hourly record precipitation was mainly in western China in 2016, while it concentrated in eastern China in 1998.
Based on the daily and hourly precipitation data of 2341 meteorological observation stations from 1961 to 2016, this paper analyzed the precipitation extreme features in China in the 2016 flood season and also did comparison with the situation in 1998. The main results are as follows. The average precipitation in 2016 is the most since 1961, and the accumulated rainfall of 140 stations exceeded historical records, with 112 stations having the second historical maximum values. These stations are 54 and 47 more respectively than the stations in 1998. The extreme precipitation in 1998 mainly occurred in Northeast China and the middle and upper reaches of the Yangtze River, but in 2016 it occurred mainly in East China and was more concentrated. Totally, 6972 stations had torrential rains, of which extremely heavy rains occurred at 1251 stations, which are the most since 1961. The largescale torrential rains happened 44 times, lasting for 90 days and showing the characteristics of being intense in middle, and weak before and after the torrential rain processes. There were extreme events of daily precipitation at 417 stations, of which 88 stations broke the historic records. The hourly maximum precipitation at 113 stations broke the historical records, with 29 stations more than in 1998. The spatial distribution of daily precipitation extremes was mainly in East China and North China in 2016, but in central China in 1998. The hourly record precipitation was mainly in western China in 2016, while it concentrated in eastern China in 1998.
2018, 44(5):704-712.
DOI: 10.7519/j.issn.1000-0526.2018.05.012
Abstract:
In this paper, conventional meteorological observations and observed hourly PM2.5 concentration are analyzed to study the pollution events in Shanghai during the recent three years. Two predominant categories of weather systems, which are defined as cold air transport type and stagnant meteorological situation type, led to severe pollution events in Shanghai. In order to better describe the two types and make a good indication in forecasting operation, the meteorological air pollution index is created, based on the ventilation index and the retention index which respectively reflects atmospheric vertical and horizontal diffusion conditions. The air pollution diffusion index has linear positive correlation with PM2.5 concentration, with a correlation coefficient of 0.525 after a significant test. This index is greatly superior to the single ventilation index or retention index. Moreover, based on historical pollution events, the transport intensity index is modified for the pollution caused by cold air regional transport. The emission parameter in the equation is changed into upstream observed PM2.5 concentration. The backcalculation test suggests that the modified transport intensity index has positive correlation with the Shanghai PM2.5 concentration, which shows a good indication to the pollution events caused by regional transport of cold airs.
In this paper, conventional meteorological observations and observed hourly PM2.5 concentration are analyzed to study the pollution events in Shanghai during the recent three years. Two predominant categories of weather systems, which are defined as cold air transport type and stagnant meteorological situation type, led to severe pollution events in Shanghai. In order to better describe the two types and make a good indication in forecasting operation, the meteorological air pollution index is created, based on the ventilation index and the retention index which respectively reflects atmospheric vertical and horizontal diffusion conditions. The air pollution diffusion index has linear positive correlation with PM2.5 concentration, with a correlation coefficient of 0.525 after a significant test. This index is greatly superior to the single ventilation index or retention index. Moreover, based on historical pollution events, the transport intensity index is modified for the pollution caused by cold air regional transport. The emission parameter in the equation is changed into upstream observed PM2.5 concentration. The backcalculation test suggests that the modified transport intensity index has positive correlation with the Shanghai PM2.5 concentration, which shows a good indication to the pollution events caused by regional transport of cold airs.
2018, 44(5):713-718.
DOI: 10.7519/j.issn.1000-0526.2018.05.013
Abstract:
The performance of medium-range forecasts by the models of T639, ECMWF and Japan (JP) from December 2017 to February 2018 are verified and compared. The results show that all the three models can predict the variation and adjustment of the atmospheric circulation over Asian middle and high latitudes well, of which ECMWF model performs the best. The three models perform also well in predicting the transitions of temperature at 850 hPa, and they all have smaller biases in temperature forecasts for southern China than for northern China. The T639 model has an overall low biases in the temperature forecast of northern China while the JP model has higher temperature forecasts for southern China. The ECMWF forecast has the best effect comprehensively. The T639 model forecasts the intensity of cold high-pressure center better than the ECMWF and JP models. The ECMWF model predicts the location of the high-pressure center weakly and by east, T639 and JP models also have obvious biases in the location forecast of high-pressure center.
The performance of medium-range forecasts by the models of T639, ECMWF and Japan (JP) from December 2017 to February 2018 are verified and compared. The results show that all the three models can predict the variation and adjustment of the atmospheric circulation over Asian middle and high latitudes well, of which ECMWF model performs the best. The three models perform also well in predicting the transitions of temperature at 850 hPa, and they all have smaller biases in temperature forecasts for southern China than for northern China. The T639 model has an overall low biases in the temperature forecast of northern China while the JP model has higher temperature forecasts for southern China. The ECMWF forecast has the best effect comprehensively. The T639 model forecasts the intensity of cold high-pressure center better than the ECMWF and JP models. The ECMWF model predicts the location of the high-pressure center weakly and by east, T639 and JP models also have obvious biases in the location forecast of high-pressure center.
2018, 44(5):719-724.
DOI: 10.7519/j.issn.1000-0526.2018.05.014
Abstract:
The main characteristics of the general atmospheric circulation in February 2018 are as follows. There were two polar vortex centers in the Northern Hemisphere and the stronger one was in the Western Hemisphere. The circulation at middle-high latitudes of the Eurasian showed a three-wave pattern, and the degree of meridionality was lower than normal. The western Pacific subtropical high was close to the climatological normal, and the Bay of Bengal trough was weaker than normal. Cold air processes attacked China frequently in February. The cold air was stronger in early February, once across the whole country and another time over northern China. The monthly mean temperature was -2.0℃, lower than normal by 0.3℃. The amount of precipitation in first half of the month was less than normal, while continuous rainfall happened in the second half of the month. Also, a snowstorm event hit Northeast China at the end of the month. The monthly mean precipitation amount was 8.1 mm, 53% less than normal. In addition, the severe long-time fog event appeared at Qiongzhou Strait and sand-dust weather appeared in Northwest China firstly this year.
The main characteristics of the general atmospheric circulation in February 2018 are as follows. There were two polar vortex centers in the Northern Hemisphere and the stronger one was in the Western Hemisphere. The circulation at middle-high latitudes of the Eurasian showed a three-wave pattern, and the degree of meridionality was lower than normal. The western Pacific subtropical high was close to the climatological normal, and the Bay of Bengal trough was weaker than normal. Cold air processes attacked China frequently in February. The cold air was stronger in early February, once across the whole country and another time over northern China. The monthly mean temperature was -2.0℃, lower than normal by 0.3℃. The amount of precipitation in first half of the month was less than normal, while continuous rainfall happened in the second half of the month. Also, a snowstorm event hit Northeast China at the end of the month. The monthly mean precipitation amount was 8.1 mm, 53% less than normal. In addition, the severe long-time fog event appeared at Qiongzhou Strait and sand-dust weather appeared in Northwest China firstly this year.
Mobile website
® 2024 All Rights Reserved
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
ISSN:1000-0526 CN:11-2282/P