ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 41,Issue 12,2015 Table of Contents
2015, 41(12):1433-1446.
DOI: 10.7519/j.issn.1000-0526.2015.12.001
Abstract:
The paper focuses on analysis of temporal evolution characteristics of thermodynamical structure and stormrelated environment in different positions of a squall line that occurred in BeijingTianjinHebei Region on 30-31 July 2013. The study is based on rapidrefresh 4DVar (RR4DVar) analysis system using 6 CINRAD radar observations combined with regional 700 automatic weather stations. The results indicate that the storm develops under favorable weather conditions. When the squall line forms there is strong warm and wet air convergence, rising motion, strong middlelevel vertical wind shear, and positive and negative vorticity approximately balanced in front of middle and southern sections, which contribute to the organization and development of middle and southern sections. In comparison, the front of northern section is under the influence of weak middlelevel vertical wind shear and divergence and sinking movement, which is not favorable for the development of northern section. As the squall line spreads down from the mountain, the front parts of middle and southern sections are under the control of relatively strong middlelevel vertical wind shear, thus strong warm and wet air convergence result in strong dynamic lifting. Also the warm and wet flow is stably conveyed to the ascending area in storm. All these are beneficial to newborn convective cells and high organization of middle and southern sections. During the squall line evolves into the bow echo, strong middlelevel vertical wind shear, outflow boundary and cold pool dominate the middle section. Moreover, the terrain forcing effect is extremely significant. These all are conductive to the convergence and aloft motion of lowlevel warm and wet airflow southerly in front of the bow echo, which are the main causes for the quick enhancement of bow echo and stable maintenance during the squall line down the mountain.
The paper focuses on analysis of temporal evolution characteristics of thermodynamical structure and stormrelated environment in different positions of a squall line that occurred in BeijingTianjinHebei Region on 30-31 July 2013. The study is based on rapidrefresh 4DVar (RR4DVar) analysis system using 6 CINRAD radar observations combined with regional 700 automatic weather stations. The results indicate that the storm develops under favorable weather conditions. When the squall line forms there is strong warm and wet air convergence, rising motion, strong middlelevel vertical wind shear, and positive and negative vorticity approximately balanced in front of middle and southern sections, which contribute to the organization and development of middle and southern sections. In comparison, the front of northern section is under the influence of weak middlelevel vertical wind shear and divergence and sinking movement, which is not favorable for the development of northern section. As the squall line spreads down from the mountain, the front parts of middle and southern sections are under the control of relatively strong middlelevel vertical wind shear, thus strong warm and wet air convergence result in strong dynamic lifting. Also the warm and wet flow is stably conveyed to the ascending area in storm. All these are beneficial to newborn convective cells and high organization of middle and southern sections. During the squall line evolves into the bow echo, strong middlelevel vertical wind shear, outflow boundary and cold pool dominate the middle section. Moreover, the terrain forcing effect is extremely significant. These all are conductive to the convergence and aloft motion of lowlevel warm and wet airflow southerly in front of the bow echo, which are the main causes for the quick enhancement of bow echo and stable maintenance during the squall line down the mountain.
2015, 41(12):1447-1455.
DOI: 10.7519/j.issn.1000-0526.2015.12.002
Abstract:
Using the mesoscale TJWRF model data and encryption automatic weather station (AWS) data, etc., we analyze the distribution characteristics of Tianjin urban heat island circulation and sea breeze circulation as well as the interaction of them. Through several typical weather cases (Local strong thunderstorms seen in urban areas and the weather without any processes affected by the sea breeze), the trigger mechanism of the interaction between urban heat island circulation and sea breeze circulation for local thunderstorms is analyzed. The results show that the extended height of urban heat island circulation is near 800 hPa, spatial extention is about 20 km, and the upward motion is obvious. The extended height of sea breeze circulation is near 800-750 hPa and spatial extention is about 40-60 km. The stretch height of the sea breeze front is about 950-900 hPa in the forefront of the sea breeze circulation, and the upward speed is 0.2 m·s-1 on average, slightly stronger than the heat island circulation. The sea breeze can weaken the urban heat island effect while the urban heat island can block the sea breeze circulation. With the sea breeze circulation pushed near to the urban, the sea breeze circulation and the urban heat island circulation encounter, then the two circulations get superimposed and the upward motion is significantly strengthened, causing the maximum upward speed to go up to 0.6 m·s-1. Under the favorable weather conditions the local severe thunderstorms can be triggered.
Using the mesoscale TJWRF model data and encryption automatic weather station (AWS) data, etc., we analyze the distribution characteristics of Tianjin urban heat island circulation and sea breeze circulation as well as the interaction of them. Through several typical weather cases (Local strong thunderstorms seen in urban areas and the weather without any processes affected by the sea breeze), the trigger mechanism of the interaction between urban heat island circulation and sea breeze circulation for local thunderstorms is analyzed. The results show that the extended height of urban heat island circulation is near 800 hPa, spatial extention is about 20 km, and the upward motion is obvious. The extended height of sea breeze circulation is near 800-750 hPa and spatial extention is about 40-60 km. The stretch height of the sea breeze front is about 950-900 hPa in the forefront of the sea breeze circulation, and the upward speed is 0.2 m·s-1 on average, slightly stronger than the heat island circulation. The sea breeze can weaken the urban heat island effect while the urban heat island can block the sea breeze circulation. With the sea breeze circulation pushed near to the urban, the sea breeze circulation and the urban heat island circulation encounter, then the two circulations get superimposed and the upward motion is significantly strengthened, causing the maximum upward speed to go up to 0.6 m·s-1. Under the favorable weather conditions the local severe thunderstorms can be triggered.
2015, 41(12):1456-1465.
DOI: 10.7519/j.issn.1000-0526.2015.12.003
Abstract:
Based on the conventional observation data, automatic station data, Doppler radar data and NCEP 1°×1° reanalysis data, the convection cells that formed and developed in the lower troposphere in the easterly airflow are analyzed and the local shortterm severe precipitation in Nanjing during YOG (Youth Olympic Games) opening ceremony caused by the convection cells is also studied. Moreover, the formation mechanism of the convection in the shallow layer of the easterly airflow, the radar characteristics and the reasons of the convection cells reversely moving in the precipitation cloud system during the rainfall are discussed. The results show that the lower troposphere over Nanjing blows easterly wind while the middleabove layer is dominated by the southwesterly wind. The transition zone between them corresponds to a dry layer which was formed by dry air carried by a northerly air in the middle troposphere. The overlapping of the dry layer on the shallow easterly warm airflow promotes the development of the convective unstable stratification in the mid and low troposphere. Local convergence by the surface wind disturbance and surface nonfrontogenesis baroclinic zone inspires the formation of the convection in the easterly airflow. The structures of the two kinds of reversely propagating convective cells in the precipitation echo have obvious differences. The barycenter height, vertical extension thickness and the prevailing background wind in the layer determine the propagation and movement of the convective cells.
Based on the conventional observation data, automatic station data, Doppler radar data and NCEP 1°×1° reanalysis data, the convection cells that formed and developed in the lower troposphere in the easterly airflow are analyzed and the local shortterm severe precipitation in Nanjing during YOG (Youth Olympic Games) opening ceremony caused by the convection cells is also studied. Moreover, the formation mechanism of the convection in the shallow layer of the easterly airflow, the radar characteristics and the reasons of the convection cells reversely moving in the precipitation cloud system during the rainfall are discussed. The results show that the lower troposphere over Nanjing blows easterly wind while the middleabove layer is dominated by the southwesterly wind. The transition zone between them corresponds to a dry layer which was formed by dry air carried by a northerly air in the middle troposphere. The overlapping of the dry layer on the shallow easterly warm airflow promotes the development of the convective unstable stratification in the mid and low troposphere. Local convergence by the surface wind disturbance and surface nonfrontogenesis baroclinic zone inspires the formation of the convection in the easterly airflow. The structures of the two kinds of reversely propagating convective cells in the precipitation echo have obvious differences. The barycenter height, vertical extension thickness and the prevailing background wind in the layer determine the propagation and movement of the convective cells.
2015, 41(12):1466-1476.
DOI: 10.7519/j.issn.1000-0526.2015.12.004
Abstract:
Cold vortex is firstly defined in this paper. And then 65 cold vortexes are identified from April to September of 2009-2013 based on the definition. Their spatiotemporal distributions are studied. The monthly variation of cold vortexes is obvious, and the most of them occur in July, mainly from the east of Lake Baikal and Mongolia to the northwest of Northeast China. Most cold vortexes live for more than 3 days. Hourly rainfall data of automatic weather station are used to analyze the characteristics of the severe shorttime precipitation under the background of cold vortex and its relations with cold vortex. The results show that severe shorttime precipitation accompanying cold vortex mainly occurs in the southeast of Hebei, Beijing, Tianjin and the Northeast Plain in July. Besides, such events are often seen from afternoon to evening. Severe shorttime precipitation can occur in any phases of cold vortexes, mainly during the developing phases. Besides, it is located mainly in the southeast and southwest of vortex center. And the distribution of severe shorttime precipitation is different in different cold vortexes.
Cold vortex is firstly defined in this paper. And then 65 cold vortexes are identified from April to September of 2009-2013 based on the definition. Their spatiotemporal distributions are studied. The monthly variation of cold vortexes is obvious, and the most of them occur in July, mainly from the east of Lake Baikal and Mongolia to the northwest of Northeast China. Most cold vortexes live for more than 3 days. Hourly rainfall data of automatic weather station are used to analyze the characteristics of the severe shorttime precipitation under the background of cold vortex and its relations with cold vortex. The results show that severe shorttime precipitation accompanying cold vortex mainly occurs in the southeast of Hebei, Beijing, Tianjin and the Northeast Plain in July. Besides, such events are often seen from afternoon to evening. Severe shorttime precipitation can occur in any phases of cold vortexes, mainly during the developing phases. Besides, it is located mainly in the southeast and southwest of vortex center. And the distribution of severe shorttime precipitation is different in different cold vortexes.
2015, 41(12):1477-1487.
DOI: 10.7519/j.issn.1000-0526.2015.12.005
Abstract:
Using intensive surface observation, NCEP/CFSR 0.5°×0.5° reanalysis data and 0.01°×0.01° global terrain data etc., the contrast role and characteristics of the easterly air stream in two convection rainstorms in the terrain transition zone of Western Sichuan Plateau in the summer of 2013 was analyzed in this paper. The activity characteristics, vertical structure and temperature and humidity characteristics, and the role in the two convective rainstorms were focused on. The results showed that: (1) The easterly activity on 3 July 2013 is below 850 hPa, lasting for about 20 h with wind speed averaged 2 m·s-1 in Sichuan Basin, while easterly activity on 6 August is below 700 hPa, also with duration 20 h but wind speed is about 4 m·s-1. Both of the two processes are composed of westerly trough moving eastward and the effect of terrain, which induce the easterly air stream. The easterly airflow forms about 12 h earlier than convective precipitation appears. (2) The easterly flows of the two processes have high equivalent potential temperature property with the dry cold air activities in the midupper troposphere, thus, forming the favorable convective unstable stratification. In contrast, after the height and wind speed of the easterly flow in the later process is obviously enhanced, much stronger lowlevel vertical wind shear is formed together with the west wind, and the local concentration characteristics of the warmwet energy is more significant, more beneficial for the sustained delivery of water vapor and energy. So the induced convective precipitation is more intensive. (3) The undulated easterly air stream, convergence center and cyclonic vorticity center are poorly related in the previous process, except when the easterly wind forces the uplift and inspires convection making the rainfall near the terrain. However, the straight easterly air stream has good relations with the convergent center and vorticity center during the second process, with almost equivalent scales. Therefore, severe convection intensifies to larger ranges and the extremely heavy rains develop to the west of the basin along the terrain.
Using intensive surface observation, NCEP/CFSR 0.5°×0.5° reanalysis data and 0.01°×0.01° global terrain data etc., the contrast role and characteristics of the easterly air stream in two convection rainstorms in the terrain transition zone of Western Sichuan Plateau in the summer of 2013 was analyzed in this paper. The activity characteristics, vertical structure and temperature and humidity characteristics, and the role in the two convective rainstorms were focused on. The results showed that: (1) The easterly activity on 3 July 2013 is below 850 hPa, lasting for about 20 h with wind speed averaged 2 m·s-1 in Sichuan Basin, while easterly activity on 6 August is below 700 hPa, also with duration 20 h but wind speed is about 4 m·s-1. Both of the two processes are composed of westerly trough moving eastward and the effect of terrain, which induce the easterly air stream. The easterly airflow forms about 12 h earlier than convective precipitation appears. (2) The easterly flows of the two processes have high equivalent potential temperature property with the dry cold air activities in the midupper troposphere, thus, forming the favorable convective unstable stratification. In contrast, after the height and wind speed of the easterly flow in the later process is obviously enhanced, much stronger lowlevel vertical wind shear is formed together with the west wind, and the local concentration characteristics of the warmwet energy is more significant, more beneficial for the sustained delivery of water vapor and energy. So the induced convective precipitation is more intensive. (3) The undulated easterly air stream, convergence center and cyclonic vorticity center are poorly related in the previous process, except when the easterly wind forces the uplift and inspires convection making the rainfall near the terrain. However, the straight easterly air stream has good relations with the convergent center and vorticity center during the second process, with almost equivalent scales. Therefore, severe convection intensifies to larger ranges and the extremely heavy rains develop to the west of the basin along the terrain.
2015, 41(12):1488-1493.
DOI: 10.7519/j.issn.1000-0526.2015.12.006
Abstract:
The spatiotemporal distribution of freezing rain in Beijing is analyzed by using the surface observation data and sounding data from 1 January 1955 to 30 April 2013. The temperaturehumidity structure and the formation mechanism type of freezing rain are studied using the sounding data. Comparative analysis of the temperaturehumidity structure and its difference from freezing rain, rainfall, sleet and snow is done using the observation data collected from November to April in 2000-2013. The results show that freezing rain is prone to occur in the northeast and southeast of Beijing, from November to the next April, of which about 86.4% is warmrain mechanism. The temperature stratification curve under 850 hPa is nearly in vertical and the temperature is below 0℃, which is the main characteristics of Beijing regional freezing rain. The main difference between sleet and freezing rain is the temperature under 850 hPa, the temperature of sleet is higher than the freezing rain.
The spatiotemporal distribution of freezing rain in Beijing is analyzed by using the surface observation data and sounding data from 1 January 1955 to 30 April 2013. The temperaturehumidity structure and the formation mechanism type of freezing rain are studied using the sounding data. Comparative analysis of the temperaturehumidity structure and its difference from freezing rain, rainfall, sleet and snow is done using the observation data collected from November to April in 2000-2013. The results show that freezing rain is prone to occur in the northeast and southeast of Beijing, from November to the next April, of which about 86.4% is warmrain mechanism. The temperature stratification curve under 850 hPa is nearly in vertical and the temperature is below 0℃, which is the main characteristics of Beijing regional freezing rain. The main difference between sleet and freezing rain is the temperature under 850 hPa, the temperature of sleet is higher than the freezing rain.
2015, 41(12):1494-1502.
DOI: 10.7519/j.issn.1000-0526.2015.12.007
Abstract:
To assimilate wind profiler data into operational numerical weather model, this paper analyzes the wind profiler product quality characteristic for data assimilation. Quality analysis is the basic work of this kind of data quality control and assimilation. Therefore, this paper analyzes the quality characteristics of the wind profile radar wind product through comparing the data and numerical model background field, and using the sounding and rainfall data. And the wind product used in this article is from the Meteorological Data Storage System (MDSS) in National Meteorological Information Centre. The findings show that average hourly sample wind is better than realtime sample wind for data assimilation application. There are lots of wind profile radar wind products existing above the effective detection height. And the bias of these data against numerical background is abnormally large. The bias between wind profiler and model background for PA Mode radar is the smallest, the second smallest is that for PB Mode and the biggest bias is for LC Mode within the effective detection height range, where there is no bias between wind profiler data and the numerical prediction background. The amount of data under one standard deviation is more than 89%, two standard deviations of the data reach more than 97%, three standard deviations of the data is above 98%. Meanwhile, precipitation is an important factor affecting the data quality, so when applying the radar product, the precipictation data should be analyzed carefully for as quality contiol.
To assimilate wind profiler data into operational numerical weather model, this paper analyzes the wind profiler product quality characteristic for data assimilation. Quality analysis is the basic work of this kind of data quality control and assimilation. Therefore, this paper analyzes the quality characteristics of the wind profile radar wind product through comparing the data and numerical model background field, and using the sounding and rainfall data. And the wind product used in this article is from the Meteorological Data Storage System (MDSS) in National Meteorological Information Centre. The findings show that average hourly sample wind is better than realtime sample wind for data assimilation application. There are lots of wind profile radar wind products existing above the effective detection height. And the bias of these data against numerical background is abnormally large. The bias between wind profiler and model background for PA Mode radar is the smallest, the second smallest is that for PB Mode and the biggest bias is for LC Mode within the effective detection height range, where there is no bias between wind profiler data and the numerical prediction background. The amount of data under one standard deviation is more than 89%, two standard deviations of the data reach more than 97%, three standard deviations of the data is above 98%. Meanwhile, precipitation is an important factor affecting the data quality, so when applying the radar product, the precipictation data should be analyzed carefully for as quality contiol.
8 Daily Precipitation Probability Forecast Based on Climatic Region
over HuangHuai Region in Summer
2015, 41(12):1503-1513.
DOI: 10.7519/j.issn.1000-0526.2015.12.008
Abstract:
Based on the rain gauge of summer daily precipitation over HuangHuai Region from 1961 to 2010, the REOF method and ttest are employed to divide the HuangHuai Region into five areas. The ttest of the five areas shows that the five areas have the significant differences, which illustrates the correctness of the division. Based on this, the summer probability regression prediction equations of the five representative sites in the five areas are established using the daily rain gauge data and the daily precipitation reforecast products of CFSv2 numerical model from June to August during 1999-2007, and related verification was carried out by the deterministic and probabilistic way. The deterministic verification of precipitation probability forecast equations established by five representative stations shows that the Threat Score of logistic regression precipitation probability equations is higher than that of the CFSv2 model and the ensemble average of T213 ensemble prediction, the false alarms rate is lower than that of the CFSv2 model and the average of T213 ensemble forecast, but the missing rate of logistic regression is slightly higher. In this paper, the probabilistic forecast verification of precipitation probability forecast equations shows that the Brier Score of logistic regression is lower than 0.2, which is much lower than that of the probability of forecast of T213 ensemble forecast. This implies that the logistic regression has higher reliability. The Brier Score Skills of the logistic regression precipitation probability forecast equations for five stations are bigger than 0.0, which means the prediction skills of precipitation probability forecast for the five representative stations are higher than those of climatical probability, higher than those of the T213 ensemble forecast. Therefore, logistic regression precipitation probability equation based on the partition is an effective and feasible method.
Based on the rain gauge of summer daily precipitation over HuangHuai Region from 1961 to 2010, the REOF method and ttest are employed to divide the HuangHuai Region into five areas. The ttest of the five areas shows that the five areas have the significant differences, which illustrates the correctness of the division. Based on this, the summer probability regression prediction equations of the five representative sites in the five areas are established using the daily rain gauge data and the daily precipitation reforecast products of CFSv2 numerical model from June to August during 1999-2007, and related verification was carried out by the deterministic and probabilistic way. The deterministic verification of precipitation probability forecast equations established by five representative stations shows that the Threat Score of logistic regression precipitation probability equations is higher than that of the CFSv2 model and the ensemble average of T213 ensemble prediction, the false alarms rate is lower than that of the CFSv2 model and the average of T213 ensemble forecast, but the missing rate of logistic regression is slightly higher. In this paper, the probabilistic forecast verification of precipitation probability forecast equations shows that the Brier Score of logistic regression is lower than 0.2, which is much lower than that of the probability of forecast of T213 ensemble forecast. This implies that the logistic regression has higher reliability. The Brier Score Skills of the logistic regression precipitation probability forecast equations for five stations are bigger than 0.0, which means the prediction skills of precipitation probability forecast for the five representative stations are higher than those of climatical probability, higher than those of the T213 ensemble forecast. Therefore, logistic regression precipitation probability equation based on the partition is an effective and feasible method.
2015, 41(12):1514-1524.
DOI: 10.7519/j.issn.1000-0526.2015.12.009
Abstract:
By using NCEP daily reanalysis data and surface weather data of 7 counties in Ningbo over 2001-2012, and LambJenkinson objective classification method and statistical method, we analyzed the regular pattern of regional haze events in Ningbo and corresponding atmospheric circulation characteristics. The results show that the regional haze in Ningbo has a seasonal distribution feature, and winter is the period with most frequent haze, while in summer haze is the least. There are about 15 times on annual average. Jumpily increasing of the regional haze in 2011 and 2012 is closely related to atmospheric circulation. The circulation for regional haze is divided into four types: Type A, Type AN, Type AS and Type C, accounting for 65.9%, 12.3%, 6.7% and 4.7% respectively. Type A mainly occurs in autumn and winter with stable and straight circulation. Type AN occurs in winter with significantly increasing meridional circulation. Type AS occurs in spring and autumn during the changing intervals of cold air and warm air. Type C occurs in spring and summer with significantly strengthened western Pacific high pressure and weak lowpressure ambient field on the ground. Cyclonic circulation at 500 hPa, west airflow and gentle breeze at 850 hPa in eastern coast are helpful for the occurrence of regional haze in Ningbo. On the contrary, anticyclonic circulation at 500 hPa and strong partial south airflow at 850 hPa suppress the haze. When Type A circulation occurs with weak cold air or static and stable air condition, the probability of continuous haze days and severe haze event increases.
By using NCEP daily reanalysis data and surface weather data of 7 counties in Ningbo over 2001-2012, and LambJenkinson objective classification method and statistical method, we analyzed the regular pattern of regional haze events in Ningbo and corresponding atmospheric circulation characteristics. The results show that the regional haze in Ningbo has a seasonal distribution feature, and winter is the period with most frequent haze, while in summer haze is the least. There are about 15 times on annual average. Jumpily increasing of the regional haze in 2011 and 2012 is closely related to atmospheric circulation. The circulation for regional haze is divided into four types: Type A, Type AN, Type AS and Type C, accounting for 65.9%, 12.3%, 6.7% and 4.7% respectively. Type A mainly occurs in autumn and winter with stable and straight circulation. Type AN occurs in winter with significantly increasing meridional circulation. Type AS occurs in spring and autumn during the changing intervals of cold air and warm air. Type C occurs in spring and summer with significantly strengthened western Pacific high pressure and weak lowpressure ambient field on the ground. Cyclonic circulation at 500 hPa, west airflow and gentle breeze at 850 hPa in eastern coast are helpful for the occurrence of regional haze in Ningbo. On the contrary, anticyclonic circulation at 500 hPa and strong partial south airflow at 850 hPa suppress the haze. When Type A circulation occurs with weak cold air or static and stable air condition, the probability of continuous haze days and severe haze event increases.
2015, 41(12):1525-1530.
DOI: 10.7519/j.issn.1000-0526.2015.12.010
Abstract:
One fog and haze weather process was detected by an atmosphere fineparticle lidar and instruments of Beijing Weather Observatory. Combining the changes of surface observation and highlevel weather elements, this paper analyzes the meteorological conditions for the maintenance of this foghaze event. First, temperature continues to rise, humidity is above 50%, wind speed is basically below 2 m·s-1, such conditions of high humidity, light wind are not conducive to rapid spread of particulate matter. Second, persistence of inversion layer and weakened atmospheric convection prevents the diffusion of particles to high altitude causing massive accumulation of particulate matter. The above two main reasons result in persistence of the fog and haze process. The fog and haze process is eventually dissipated by the rain erosion to particulate matter, the role of wet deposition and the increase of surface wind arrival. From detection results of atmosphere fine particle lidar we found the fog and haze vertical height reduces very quickly. The detection results of the fine particle lidar and ground instruments are basically the same. However, comparing the detection results of the fine particle lidar and the Lband sounding radar, under the saturated vapor condition, the foghaze height detected by the fine particle lidar is lower.
One fog and haze weather process was detected by an atmosphere fineparticle lidar and instruments of Beijing Weather Observatory. Combining the changes of surface observation and highlevel weather elements, this paper analyzes the meteorological conditions for the maintenance of this foghaze event. First, temperature continues to rise, humidity is above 50%, wind speed is basically below 2 m·s-1, such conditions of high humidity, light wind are not conducive to rapid spread of particulate matter. Second, persistence of inversion layer and weakened atmospheric convection prevents the diffusion of particles to high altitude causing massive accumulation of particulate matter. The above two main reasons result in persistence of the fog and haze process. The fog and haze process is eventually dissipated by the rain erosion to particulate matter, the role of wet deposition and the increase of surface wind arrival. From detection results of atmosphere fine particle lidar we found the fog and haze vertical height reduces very quickly. The detection results of the fine particle lidar and ground instruments are basically the same. However, comparing the detection results of the fine particle lidar and the Lband sounding radar, under the saturated vapor condition, the foghaze height detected by the fine particle lidar is lower.
11 Analysis of Suspected Temperature Observations from
Urban Areas in Particular Weather Conditions
2015, 41(12):1531-1537.
DOI: 10.7519/j.issn.1000-0526.2015.12.011
Abstract:
Temperature observations, especially those observations from highly urbanized areas, are most likely to fail persistence test and step test when basic quality assurance (QA) procedures are applied. According to WMO, doubtful data from the persistence test and the step test are called dead band suspected data and inconsistent suspected data. Studying these suspected observations may contribute to validating important doubtful data and improving the performance of temperature QA system. Basic QA procedures are applied to hourly temperature observations at 18 automatic weather stations in a highly urbanized area (Shanghai Expo) collected from May 2010 to April 2011. The distribution of suspected data and possible causes are investigated. The results show that temperature dead band suspected cases occur mostly at isolated stations in the winter evening. They are more likely observed at shielded and blocked stations in cloudy weather. The sensible heat flux is low in these situations, which may be the reason that temperature keeps the same value for several hours, even lasting for 11 h at most. In addition, the temperature inconsistent suspected cases can be grouped into two subsets: temperature jump cases and temperature slump cases. The temperature jump cases mostly occur around sunrise in autumn and winter while the slump cases mainly are found in the afternoon or evening of springsummer season. Moreover, the temperature jump cases appear at isolated stations, but temperature slump cases cooccur at different observing sites. The occurrence of these cases is closely related to weather conditions. As solar altitude increases at sunrise, the sheltered stations are suddenly exposed to the sun and warm up dramatically. Similarly, temperature goes down rapidly around sunset at the sheltered stations and temperature slump cases occur. In addition, the shorttime heavy precipitation also causes dramatically cooling at stations. Therefore, these suspected data are reasonable. They might be important observations in studying extreme weather events as well as environment effects on temperature. Multiple crosschecks are required when some samples fail in the basic QA test.
Temperature observations, especially those observations from highly urbanized areas, are most likely to fail persistence test and step test when basic quality assurance (QA) procedures are applied. According to WMO, doubtful data from the persistence test and the step test are called dead band suspected data and inconsistent suspected data. Studying these suspected observations may contribute to validating important doubtful data and improving the performance of temperature QA system. Basic QA procedures are applied to hourly temperature observations at 18 automatic weather stations in a highly urbanized area (Shanghai Expo) collected from May 2010 to April 2011. The distribution of suspected data and possible causes are investigated. The results show that temperature dead band suspected cases occur mostly at isolated stations in the winter evening. They are more likely observed at shielded and blocked stations in cloudy weather. The sensible heat flux is low in these situations, which may be the reason that temperature keeps the same value for several hours, even lasting for 11 h at most. In addition, the temperature inconsistent suspected cases can be grouped into two subsets: temperature jump cases and temperature slump cases. The temperature jump cases mostly occur around sunrise in autumn and winter while the slump cases mainly are found in the afternoon or evening of springsummer season. Moreover, the temperature jump cases appear at isolated stations, but temperature slump cases cooccur at different observing sites. The occurrence of these cases is closely related to weather conditions. As solar altitude increases at sunrise, the sheltered stations are suddenly exposed to the sun and warm up dramatically. Similarly, temperature goes down rapidly around sunset at the sheltered stations and temperature slump cases occur. In addition, the shorttime heavy precipitation also causes dramatically cooling at stations. Therefore, these suspected data are reasonable. They might be important observations in studying extreme weather events as well as environment effects on temperature. Multiple crosschecks are required when some samples fail in the basic QA test.
2015, 41(12):1538-1544.
DOI: 10.7519/j.issn.1000-0526.2015.12.012
Abstract:
By using the agrometeorological data in Jiangsu Province, and the statistical analysis method, this research reveals that there is a significant positive correlation between the suitable transplanting date of rice and the effective accumulated temperature larger than 10 degrees celsius during the period of seeding and transplanting. This means that the suitable transplanting date of rice could be determined by the effective accumulated temperature. According to the principle of airsea interaction， the concept of teleconnection and through seeking for the forecast factors of SST for the effective accumulated temperature, the high correlated SST predictors are selected by using the optimal relevant technique and spatial topologic analysis method. Then, the stability and independence test is carried out so as to ensure the reliability of the SST predictors. Moreover, the longterm prediction model of the suitable transplanting date of rice is established. Furthermore, through the historical fitting and forecast verification, the result of the prediction model is found reasonable. The suitable transplanting date can be predicted by the model at least two weeks in advance. So, the prediction results could give some guidance for agriculture.
By using the agrometeorological data in Jiangsu Province, and the statistical analysis method, this research reveals that there is a significant positive correlation between the suitable transplanting date of rice and the effective accumulated temperature larger than 10 degrees celsius during the period of seeding and transplanting. This means that the suitable transplanting date of rice could be determined by the effective accumulated temperature. According to the principle of airsea interaction， the concept of teleconnection and through seeking for the forecast factors of SST for the effective accumulated temperature, the high correlated SST predictors are selected by using the optimal relevant technique and spatial topologic analysis method. Then, the stability and independence test is carried out so as to ensure the reliability of the SST predictors. Moreover, the longterm prediction model of the suitable transplanting date of rice is established. Furthermore, through the historical fitting and forecast verification, the result of the prediction model is found reasonable. The suitable transplanting date can be predicted by the model at least two weeks in advance. So, the prediction results could give some guidance for agriculture.
2015, 41(12):1545-1553.
DOI: 10.7519/j.issn.1000-0526.2015.12.013
Abstract:
Precipitation measurement of using microwave link is the latest technology of precipitation measurement. Microwave has direct effect on near surface atmosphere, so it has advantages of high spatial and temporal resolution. This paper summarizes the development status and technical difficulties of the precipitation measurement using the microwave link. Combined with the practical application of microwave communications, it analyzes the basis for frequency band selection, factors to be considered for signal attenuation measurement and detailed rain attenuation forward modeling. It also points out that accurate recognition of precipitation initiation time and area rainfall retrieval algorithms are two key technologies for its practical application. In a word, this paper provides a reference for further studies on the precipitation measurement method by microwave link.
Precipitation measurement of using microwave link is the latest technology of precipitation measurement. Microwave has direct effect on near surface atmosphere, so it has advantages of high spatial and temporal resolution. This paper summarizes the development status and technical difficulties of the precipitation measurement using the microwave link. Combined with the practical application of microwave communications, it analyzes the basis for frequency band selection, factors to be considered for signal attenuation measurement and detailed rain attenuation forward modeling. It also points out that accurate recognition of precipitation initiation time and area rainfall retrieval algorithms are two key technologies for its practical application. In a word, this paper provides a reference for further studies on the precipitation measurement method by microwave link.
2015, 41(12):1554-1561.
DOI: 10.7519/j.issn.1000-0526.2015.12.014
Abstract:
The location, track, landfall point and intensity forecast error of tropical cyclones (TCs) over Western North Pacific in 2014 are evaluated on the basis of CMA/STI’s “Besttrack” dataset. The results show that the performance of TC positioning is a little worse than in 2013, with an average error by all methods being 25.3 km. The average track forecast errors of CMA subjective method are 84.3 km (24 h), 145.6 km (48 h) and 205.4 km (72 h), 280.2 km (96 h) and 415.3 km (120 h), respectively. A huge reduction on track forecast was made at large lead time compared to 2013. Meanwhile, global model’s average track forecast errors are 88.1 km (24 h), 159.6 km (48 h), 253.9 km (72 h), 393.6 km (96 h) and 572.1 km (120 h), and the average errors for regional models are 97.4 km (24 h), 188.2 km (48 h), and 302.7 km (72 h). The overall performance of statistical forecast method is still better than numerical prediction method in intensity forecast, while in the numerical prediction methods, the performance of regional models is slightly better than that of global models.
The location, track, landfall point and intensity forecast error of tropical cyclones (TCs) over Western North Pacific in 2014 are evaluated on the basis of CMA/STI’s “Besttrack” dataset. The results show that the performance of TC positioning is a little worse than in 2013, with an average error by all methods being 25.3 km. The average track forecast errors of CMA subjective method are 84.3 km (24 h), 145.6 km (48 h) and 205.4 km (72 h), 280.2 km (96 h) and 415.3 km (120 h), respectively. A huge reduction on track forecast was made at large lead time compared to 2013. Meanwhile, global model’s average track forecast errors are 88.1 km (24 h), 159.6 km (48 h), 253.9 km (72 h), 393.6 km (96 h) and 572.1 km (120 h), and the average errors for regional models are 97.4 km (24 h), 188.2 km (48 h), and 302.7 km (72 h). The overall performance of statistical forecast method is still better than numerical prediction method in intensity forecast, while in the numerical prediction methods, the performance of regional models is slightly better than that of global models.
2015, 41(12):1562-1567.
DOI: 10.7519/j.issn.1000-0526.2015.12.015
Abstract:
The main characteristics of the general atmospheric circulation in September 2015 are as follows. There was one polar vortex center in the Northern Hemisphere. In the middlehigh latitudes, the circulation presented a threewave pattern. The subtropical high lay westwards and got broken in the middle. Meanwhile, monthly mean precipitation amount was 72.4 mm, which is 14.0% more than its climatological mean (65.3 mm). Monthly mean temperature was 16.9℃, a little bit higher than its climatological mean (16.6℃). There were 6 heavy rainfall events with extreme continuous precipitation events observed at 24 stations in China. Four typhoons were generated over the western North Pacific and the South China Sea, and one typhoon came from the Middle Pacific (No. 1517 Kilo), Typhoon Dujuan (No. 1521) landing China twice. The drought of eastern part of Northwest Region and the middle of Inner Mongolia got relieved, while in most of Huanghuai Region, Liaoning and other places, the drought developed continuously. In addition, many places were attacked by thunderstorms, hail and other severe convective weather in September 2015.
The main characteristics of the general atmospheric circulation in September 2015 are as follows. There was one polar vortex center in the Northern Hemisphere. In the middlehigh latitudes, the circulation presented a threewave pattern. The subtropical high lay westwards and got broken in the middle. Meanwhile, monthly mean precipitation amount was 72.4 mm, which is 14.0% more than its climatological mean (65.3 mm). Monthly mean temperature was 16.9℃, a little bit higher than its climatological mean (16.6℃). There were 6 heavy rainfall events with extreme continuous precipitation events observed at 24 stations in China. Four typhoons were generated over the western North Pacific and the South China Sea, and one typhoon came from the Middle Pacific (No. 1517 Kilo), Typhoon Dujuan (No. 1521) landing China twice. The drought of eastern part of Northwest Region and the middle of Inner Mongolia got relieved, while in most of Huanghuai Region, Liaoning and other places, the drought developed continuously. In addition, many places were attacked by thunderstorms, hail and other severe convective weather in September 2015.
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ISSN:1000-0526 CN:11-2282/P