ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 40,Issue 12,2014 Table of Contents
MAO Dongyan
,
ZHU Wenjian
,
FAN Liqiang
,
CAI Xuewei
,
ZHANG Tao
,
CHEN Jing
,
HUANG Liping
,
WANG Yu
2014, 40(12):1429-1438.
DOI: 10.7519/j.issn.1000-0526.2014.12.001
Abstract:
The synoptic verification is conducted for the GRAPES_MESO V3.3 updated in June 2013. The results indicate that the model can forecast the physical conditions well, including the water vapor, the instability and the vertical wind shear, but the forecast accuracy is different from August to October. For some of the physical conditions that reach a given threshold, the model can forecast better. Moreover, the initiation and development of the rainstorm and convective weather can be reflected well, especially the details from the high resolution products, but not very good for the rainstorm that is extreme or affected by the topography.
The synoptic verification is conducted for the GRAPES_MESO V3.3 updated in June 2013. The results indicate that the model can forecast the physical conditions well, including the water vapor, the instability and the vertical wind shear, but the forecast accuracy is different from August to October. For some of the physical conditions that reach a given threshold, the model can forecast better. Moreover, the initiation and development of the rainstorm and convective weather can be reflected well, especially the details from the high resolution products, but not very good for the rainstorm that is extreme or affected by the topography.
2014, 40(12):1439-1445.
DOI: 10.7519/j.issn.1000-0526.2014.12.002
Abstract:
Using the conventional observation data, NCEP reanalysis data, two cases of spring torrential rains in Shandong Peninsula are studied. The results show that the rainfall caused by spring Huang Huai cyclone in Shandong Peninsula is concentrated in the northern part of the cyclone and mainly located in the northeast air stream. The northerly extent of rainfall areas are related with synoptic backward extent and the existence of the high pressure in Northeast China. When the synoptic system is obviously backward and the frontal slope is small, warm air stream along the front climbs north further and the rainfall moves northerly. If there is a high pressure in Northeast China, northeasterly wind at the southern side of the high invades the vortex at 850 hPa joined by the southeasterly wind. The asymptotic convergence in the northern part of the vortex generates the rainfall. Furthermore, the formation of cold northeasterly air stream is favorable for the climbing of warm air northward. In operation, it is necessary to analyze the spatial structure of the system and the impact of the surrounding temperature field comprehensively.
Using the conventional observation data, NCEP reanalysis data, two cases of spring torrential rains in Shandong Peninsula are studied. The results show that the rainfall caused by spring Huang Huai cyclone in Shandong Peninsula is concentrated in the northern part of the cyclone and mainly located in the northeast air stream. The northerly extent of rainfall areas are related with synoptic backward extent and the existence of the high pressure in Northeast China. When the synoptic system is obviously backward and the frontal slope is small, warm air stream along the front climbs north further and the rainfall moves northerly. If there is a high pressure in Northeast China, northeasterly wind at the southern side of the high invades the vortex at 850 hPa joined by the southeasterly wind. The asymptotic convergence in the northern part of the vortex generates the rainfall. Furthermore, the formation of cold northeasterly air stream is favorable for the climbing of warm air northward. In operation, it is necessary to analyze the spatial structure of the system and the impact of the surrounding temperature field comprehensively.
2014, 40(12):1446-1454.
DOI: 10.7519/j.issn.1000-0526.2014.12.003
Abstract:
Based on conventional observations and NCEP 1°×1° reanalysis data, causes and precipitation type of the rain and snow weather process in North China during 3-4 November 2012 are analyzed. The results show that the deep low vortex and surface cyclone are the systems that directly impact the process. The southeast low level jet transporting the abundant moisture from the eastern sea leads to the atmospheric precipitable water over the entire rain and snow storm area, exceeding the average of the month. The high level divergence systems superimposed on the low level convergence systems of the vortex and the cyclone provide a strong and lasting upward movement for the severe rain and snow storm. The heavy rain area and the blizzard region respectively stand for the convection instability stratification and the conditional symmetric instability stratification, and the frontogenesis favours the heavy snow storm. The environmental conditions of the snowflake formation and growth, and the melting of the snowflakes falling are equally important in determining the precipitation type. The combinations of the two reasons mentioned above ensure the emergence of snow on the ground surface.
Based on conventional observations and NCEP 1°×1° reanalysis data, causes and precipitation type of the rain and snow weather process in North China during 3-4 November 2012 are analyzed. The results show that the deep low vortex and surface cyclone are the systems that directly impact the process. The southeast low level jet transporting the abundant moisture from the eastern sea leads to the atmospheric precipitable water over the entire rain and snow storm area, exceeding the average of the month. The high level divergence systems superimposed on the low level convergence systems of the vortex and the cyclone provide a strong and lasting upward movement for the severe rain and snow storm. The heavy rain area and the blizzard region respectively stand for the convection instability stratification and the conditional symmetric instability stratification, and the frontogenesis favours the heavy snow storm. The environmental conditions of the snowflake formation and growth, and the melting of the snowflakes falling are equally important in determining the precipitation type. The combinations of the two reasons mentioned above ensure the emergence of snow on the ground surface.
2014, 40(12):1450-1506.
DOI: 10.7519/j.issn.1000-0526.2014.12.008
Abstract:
Using conventional sounding data, surface observation data, NCEP 1.0×1.0 reanalysis data and Doppler radar data, three times of rain and snow processes in Hunan in early February 2014 are analyzed. The results show that (1) the first process is a freezing rain process in southern Hunan, which is characterized by obvious inversion layer between 700 hPa and 850 hPa. The temperature at 700 hPa is above 0℃, but at 850 hPa and 925 hPa it is below -4℃ while the ground temperature is below 0℃. From the perspective of main system configuration, strong southwest jet at 700 hPa plays an important role in water vapor transmission and the formation of melting layer. A stationary front and deep cold pad which is comprised of the cold air blocked by Nanling Mountains, are the causes for the long lasting southern Hunan freezing rain. (2) The second and third processes are snow based processes with surface temperature around 0℃, and the temperature above surface is lower than 0℃. (3) The third process of rain/snow is the heaviest. Warm moist air rises along the front, and low level cold air results in this severe rain and snow process. Radar echo of this process has the characteristics of mixed echo of cumulus and stratus as well as low centroid high efficient precipitation feature.
Using conventional sounding data, surface observation data, NCEP 1.0×1.0 reanalysis data and Doppler radar data, three times of rain and snow processes in Hunan in early February 2014 are analyzed. The results show that (1) the first process is a freezing rain process in southern Hunan, which is characterized by obvious inversion layer between 700 hPa and 850 hPa. The temperature at 700 hPa is above 0℃, but at 850 hPa and 925 hPa it is below -4℃ while the ground temperature is below 0℃. From the perspective of main system configuration, strong southwest jet at 700 hPa plays an important role in water vapor transmission and the formation of melting layer. A stationary front and deep cold pad which is comprised of the cold air blocked by Nanling Mountains, are the causes for the long lasting southern Hunan freezing rain. (2) The second and third processes are snow based processes with surface temperature around 0℃, and the temperature above surface is lower than 0℃. (3) The third process of rain/snow is the heaviest. Warm moist air rises along the front, and low level cold air results in this severe rain and snow process. Radar echo of this process has the characteristics of mixed echo of cumulus and stratus as well as low centroid high efficient precipitation feature.
2014, 40(12):1455-1463.
DOI: 10.7519/j.issn.1000-0526.2014.12.004
Abstract:
A severe typical warm sector torrential rain with the obvious mesoscale characteristics of long lasting and concentrating precipitation area attacked Huanghuai Region on July 7 2012. The formation of the warm sector torrential rain induced by the Huanghuai warm wind shear line is discussed based on conventional and unconventional observation data and NCEP analysis data. The results showed that the whole troposphere with high humidity is beneficial to weaken the lifting condition, enhance precipitation efficiency and formation of quasi stationary mesoscale convective systems. Vertical wind shear in low troposphere and extra low altitude jet flow are likely to play an important role in triggering and maintaining the convection. Subsynoptic and mesoscale lift conditions such as surface wind convergence line, shear line at 850 hPa or 925 hPa and wind convergence brought by the low level jet can lead to the torrential rain. Meanwhile, the radar echo represents the backward propagation, train effects and tropical heavy rainfall characteristics.
A severe typical warm sector torrential rain with the obvious mesoscale characteristics of long lasting and concentrating precipitation area attacked Huanghuai Region on July 7 2012. The formation of the warm sector torrential rain induced by the Huanghuai warm wind shear line is discussed based on conventional and unconventional observation data and NCEP analysis data. The results showed that the whole troposphere with high humidity is beneficial to weaken the lifting condition, enhance precipitation efficiency and formation of quasi stationary mesoscale convective systems. Vertical wind shear in low troposphere and extra low altitude jet flow are likely to play an important role in triggering and maintaining the convection. Subsynoptic and mesoscale lift conditions such as surface wind convergence line, shear line at 850 hPa or 925 hPa and wind convergence brought by the low level jet can lead to the torrential rain. Meanwhile, the radar echo represents the backward propagation, train effects and tropical heavy rainfall characteristics.
2014, 40(12):1464-1480.
DOI: 10.7519/j.issn.1000-0526.2014.12.005
Abstract:
NCEP reanalysis data (horizontal resolution of 1°×1°, vertical level 26 layers) and a variety of conventional observation data and real time typhoon positioning data from Central Meteorological Observatory are used to analyze the features of No.1330 typhoon Haiyan. The weather analysis and dynamic diagnostic methods are used to explore “Haiyan” dynamic mechanism of strengthing development and fast moving, and to excavate forecast key points to raise the capability of Central Meteorological Observatory in forecasting similar typhoons in the future. The main conclusions of this paper are: (1) “Haiyan” continues to strengthen and keeps strength before landing Philippines in the simultaneously strengthening of the subtropical westerly jet in the course southward and the easterly wind located in the south side of subtropical high. (2) The strengthening of subtropical westerly jet in the course southward is an important cause for the strengthening of the subtropical high and the easterly wind in the south side of the subtropical high in all tropospheric layers. (3) The distribution of “Haiyan” horizontal wind speed is obviously asymmetric, showing the easterly is greater than the westerly, the southerly is greater than the northerly, and the characteristics of the zonal wind asymmetry is more pronounced. The enhancement of shear positive vorticity caused by the asymmetry of the zonal wind and meridional wind may be the important cause for the intense development of “Haiyan” before its landing Phillppine. (4) The enhancement of horizontal convergence in the lower troposphere and the existence of vertical meridional circulation may be another important cause. (5) The main dynamic mechanism of the continuously strengthening of Typhoon Haiyan is horizontal convergence in lower troposphere and tropospheric vorticity increase significantly in inner core and the enhancement of divergence in upper troposphere and the decrease of wind shear in its environmental area. (6) For typhoon in autumn and winter, in addition to the western Pacific subtropical high, westerly trough, the lower troposphere easterly winds, cross equatorial flow, it is important to pay attention to the changes in the upper troposphere subtropical westerly jet stream, especially to the westward typhoon. The strengthening of the subtropical westerly jet may cause typhoon movement to accelerate significantly and intensify. Furthermore upper troposphere not only impacts the change of high level outflow of typhoon, but also plays some guiding roles in typhoon movement as well as the upper circulations.
NCEP reanalysis data (horizontal resolution of 1°×1°, vertical level 26 layers) and a variety of conventional observation data and real time typhoon positioning data from Central Meteorological Observatory are used to analyze the features of No.1330 typhoon Haiyan. The weather analysis and dynamic diagnostic methods are used to explore “Haiyan” dynamic mechanism of strengthing development and fast moving, and to excavate forecast key points to raise the capability of Central Meteorological Observatory in forecasting similar typhoons in the future. The main conclusions of this paper are: (1) “Haiyan” continues to strengthen and keeps strength before landing Philippines in the simultaneously strengthening of the subtropical westerly jet in the course southward and the easterly wind located in the south side of subtropical high. (2) The strengthening of subtropical westerly jet in the course southward is an important cause for the strengthening of the subtropical high and the easterly wind in the south side of the subtropical high in all tropospheric layers. (3) The distribution of “Haiyan” horizontal wind speed is obviously asymmetric, showing the easterly is greater than the westerly, the southerly is greater than the northerly, and the characteristics of the zonal wind asymmetry is more pronounced. The enhancement of shear positive vorticity caused by the asymmetry of the zonal wind and meridional wind may be the important cause for the intense development of “Haiyan” before its landing Phillppine. (4) The enhancement of horizontal convergence in the lower troposphere and the existence of vertical meridional circulation may be another important cause. (5) The main dynamic mechanism of the continuously strengthening of Typhoon Haiyan is horizontal convergence in lower troposphere and tropospheric vorticity increase significantly in inner core and the enhancement of divergence in upper troposphere and the decrease of wind shear in its environmental area. (6) For typhoon in autumn and winter, in addition to the western Pacific subtropical high, westerly trough, the lower troposphere easterly winds, cross equatorial flow, it is important to pay attention to the changes in the upper troposphere subtropical westerly jet stream, especially to the westward typhoon. The strengthening of the subtropical westerly jet may cause typhoon movement to accelerate significantly and intensify. Furthermore upper troposphere not only impacts the change of high level outflow of typhoon, but also plays some guiding roles in typhoon movement as well as the upper circulations.
2014, 40(12):1481-1490.
DOI: 10.7519/j.issn.1000-0526.2014.12.006
Abstract:
Based on 2.5°×2.5° NCEP/NCAR reanalysis data and the improved local meridional circulation model, quantitative diagnosis for the mechanism was performed on a continuous autumn rain event in Henan Province from 5 to 19 September 2011, and evolution characteristics of the main physical factors for the continuous autumn rain event were proposed by means of lag correlation analysis of the upward branch of a local meridional circulation and precipitation over Henan. The results showed that, (1) latent heating, average meridional temperature advection, zonal advection of westerly momentum and average zonal temperature advection are the main physical factors which caused the continuous rainy weather to occur over Henan Province in September 2011. (2) The latent heating and average zonal temperature advection are the main physical factors for the start of the rainy weather; zonal advection of average westerly momentum and average meridional temperature advection as well as average zonal temperature advection are the physical factors for the continuous rainy weather; latent heating, zonal advection of average westerly momentum, average meridional temperature advection and average zonal temperature advection are also the main physical factors for the continous rainy weather ending.
Based on 2.5°×2.5° NCEP/NCAR reanalysis data and the improved local meridional circulation model, quantitative diagnosis for the mechanism was performed on a continuous autumn rain event in Henan Province from 5 to 19 September 2011, and evolution characteristics of the main physical factors for the continuous autumn rain event were proposed by means of lag correlation analysis of the upward branch of a local meridional circulation and precipitation over Henan. The results showed that, (1) latent heating, average meridional temperature advection, zonal advection of westerly momentum and average zonal temperature advection are the main physical factors which caused the continuous rainy weather to occur over Henan Province in September 2011. (2) The latent heating and average zonal temperature advection are the main physical factors for the start of the rainy weather; zonal advection of average westerly momentum and average meridional temperature advection as well as average zonal temperature advection are the physical factors for the continuous rainy weather; latent heating, zonal advection of average westerly momentum, average meridional temperature advection and average zonal temperature advection are also the main physical factors for the continous rainy weather ending.
2014, 40(12):1491-1499.
DOI: 10.7519/j.issn.1000-0526.2014.12.007
Abstract:
A squall line storm that stroke Guangxi severely in 27-28 March 2013 was traced and alerted based on various observation data collected by conventional meteorological radar, and automatic meteorological stations, etc. This paper particularly analyzes the large scale circulation weather background, the characteristics of radar echo and formation mechanism of gale. The results show that this squall line is caused by the cold trough of high altitude and high pressure of ground. The good thermal and dynamic conditions over Guangxi are demonstrated on graphs of equivalent potential temperature and T logp. Initial convection is triggered by the ground convergence line. Surface pressure field of matured squall line has the mesoscale features including thunderstorm high, depression before and after the squall. Disastrous weathers such as gale of squall usually appear in the area of big values of barometric gradient and the split part of squall line before ground high pressure. On the other hand, the information of radar, including midaltitude radial convergence (MARC), reflectivity core and middle level greatest speed gradually decrease and the transition of the low level wind show vertical wind profile chart, which could be well in indicating ground wind. Drag effect of precipitation particles and the fast moving squall line have certain effect on generation and growth of ground gale.
A squall line storm that stroke Guangxi severely in 27-28 March 2013 was traced and alerted based on various observation data collected by conventional meteorological radar, and automatic meteorological stations, etc. This paper particularly analyzes the large scale circulation weather background, the characteristics of radar echo and formation mechanism of gale. The results show that this squall line is caused by the cold trough of high altitude and high pressure of ground. The good thermal and dynamic conditions over Guangxi are demonstrated on graphs of equivalent potential temperature and T logp. Initial convection is triggered by the ground convergence line. Surface pressure field of matured squall line has the mesoscale features including thunderstorm high, depression before and after the squall. Disastrous weathers such as gale of squall usually appear in the area of big values of barometric gradient and the split part of squall line before ground high pressure. On the other hand, the information of radar, including midaltitude radial convergence (MARC), reflectivity core and middle level greatest speed gradually decrease and the transition of the low level wind show vertical wind profile chart, which could be well in indicating ground wind. Drag effect of precipitation particles and the fast moving squall line have certain effect on generation and growth of ground gale.
2014, 40(12):1507-1512.
DOI: 10.7519/j.issn.1000-0526.2014.12.009
Abstract:
Severe Typhoon Utor (No.1311) brings sustained heavy rainfall with extremely strong convective storms to Guangdong after it makes landfall. Based on the observation and the NCAR FNL data, characteristics of large scale circulation, especially of the atmospheric stratification during the extreme event are studied. It is found that, the maintenance of the instable stratification is mainly due to the warm advection to Guangdong transferred by the low level jet. Further study reveals a truth that, the low level jet, originally cold over the sea, is warmed and blows to Guangdong when it moves across a warm air mass, which is forced from the land to the upstream region of Guangdong by the outer circulation of “Utor” while it is approaching Guangdong. The result of temperature diagnosis function confirms it. Similar phenomena are found in many cases which result in sustained torrential rain events after typhoons land. Therefore, the variation of the temperature field and the low level jet caused by the landfall of typhoon should be paid more attention to in forecasting operations.
Severe Typhoon Utor (No.1311) brings sustained heavy rainfall with extremely strong convective storms to Guangdong after it makes landfall. Based on the observation and the NCAR FNL data, characteristics of large scale circulation, especially of the atmospheric stratification during the extreme event are studied. It is found that, the maintenance of the instable stratification is mainly due to the warm advection to Guangdong transferred by the low level jet. Further study reveals a truth that, the low level jet, originally cold over the sea, is warmed and blows to Guangdong when it moves across a warm air mass, which is forced from the land to the upstream region of Guangdong by the outer circulation of “Utor” while it is approaching Guangdong. The result of temperature diagnosis function confirms it. Similar phenomena are found in many cases which result in sustained torrential rain events after typhoons land. Therefore, the variation of the temperature field and the low level jet caused by the landfall of typhoon should be paid more attention to in forecasting operations.
2014, 40(12):1513-1521.
DOI: 10.7519/j.issn.1000-0526.2014.12.010
Abstract:
Using the boundary layer wind profile radar (WPR), a stratiform cloud precipitation event was observed and studied, which occurred in Bayinbluke in the central part of Tianshan Mountain from 22:00 BT 8 August to 04:00 BT 9 August 2012. The spectral parameters were obtained by calculating the data of vertical velocity power spectrum. The height of 0℃ layer evaluated by the change characteristics of spectral parameters is from 1100 m to 1900 m. By analyzing raindrop size distributions from 600 m to 1100 m, it is found that different size reflectivity depends on the concentrations of mid sized particles and large sized particles. The tempol and spatial trends of rainfall intensity and water content evaluated by raindrop size distributions are the same as the trend of reflectivity evaluated by the power spectral density. By analyzing the relationship between raindrop intensity and reflectivity, the equation is established: Z=76.5I1.6.
Using the boundary layer wind profile radar (WPR), a stratiform cloud precipitation event was observed and studied, which occurred in Bayinbluke in the central part of Tianshan Mountain from 22:00 BT 8 August to 04:00 BT 9 August 2012. The spectral parameters were obtained by calculating the data of vertical velocity power spectrum. The height of 0℃ layer evaluated by the change characteristics of spectral parameters is from 1100 m to 1900 m. By analyzing raindrop size distributions from 600 m to 1100 m, it is found that different size reflectivity depends on the concentrations of mid sized particles and large sized particles. The tempol and spatial trends of rainfall intensity and water content evaluated by raindrop size distributions are the same as the trend of reflectivity evaluated by the power spectral density. By analyzing the relationship between raindrop intensity and reflectivity, the equation is established: Z=76.5I1.6.
2014, 40(12):1522-1529.
DOI: 10.7519/j.issn.1000-0526.2014.12.011
Abstract:
The WRF model system is utilized to simulating the fog event seen in North China in 22-23 January 2013. Three numerical simulation experiments about PBL schemes, Microphysics schemes, and LSM schemes are designed, and their simulative effects are evaluated by comparing with surface observations. The result shows that the most suitable parameterizations are TEMF PBL, Goddard Microphysics and RUC LSM. It also reveals that WRF model shows better capability in simulating surface wind than other surface elements, and the combination of 10 m relative humidity and 10 m liquid water content (LWC) can effectively improve the accuracy in fog identification.
The WRF model system is utilized to simulating the fog event seen in North China in 22-23 January 2013. Three numerical simulation experiments about PBL schemes, Microphysics schemes, and LSM schemes are designed, and their simulative effects are evaluated by comparing with surface observations. The result shows that the most suitable parameterizations are TEMF PBL, Goddard Microphysics and RUC LSM. It also reveals that WRF model shows better capability in simulating surface wind than other surface elements, and the combination of 10 m relative humidity and 10 m liquid water content (LWC) can effectively improve the accuracy in fog identification.
12 Application of Doppler Radar Wind Field Retrieval Technique to Southwest Vortex Rainstorm Process
2014, 40(12):1530-1538.
DOI: 10.7519/j.issn.1000-0526.2014.12.012
Abstract:
Horizontal wind fields in different heights were retrieved for two local severe rainfall processes within the southwest vortexes which occurred in Chongqing in 2010 and 2013, respectively, using Doppler weather radar 4DVar (four dimensional variation) assimilation technique. Local circulation patterns which are prone to local intense rainfalls are also analyzed. The results show that the position and evolution of low level jet streams, low level convergence lines and local cyclonic vortices can be accurately denoted by retrieved wind fields. The evolution of convergence lines and the intensity and transfer of low level jet streams are indicative of heavy precipitation. The deeper the local cyclonic vortex is, the greater the intensity and extension of local intense rainfall become. Coupling in cyclonic vortexes of different heights can be prone to intensification of low level jet stream and transportation of moisture.
Horizontal wind fields in different heights were retrieved for two local severe rainfall processes within the southwest vortexes which occurred in Chongqing in 2010 and 2013, respectively, using Doppler weather radar 4DVar (four dimensional variation) assimilation technique. Local circulation patterns which are prone to local intense rainfalls are also analyzed. The results show that the position and evolution of low level jet streams, low level convergence lines and local cyclonic vortices can be accurately denoted by retrieved wind fields. The evolution of convergence lines and the intensity and transfer of low level jet streams are indicative of heavy precipitation. The deeper the local cyclonic vortex is, the greater the intensity and extension of local intense rainfall become. Coupling in cyclonic vortexes of different heights can be prone to intensification of low level jet stream and transportation of moisture.
2014, 40(12):1539-1548.
DOI: 10.7519/j.issn.1000-0526.2014.12.013
Abstract:
Using radar and intensive AWS (automatic meteorological station) data as well as VDRAS data whose temporal resolution is 12 min, horizontal and vertical resolutions are respectively 3 km and 1 km or so, the dynamical and thermodynamic processes of thunderstorm systems that are impacted by sea breeze convergence lines are investigated by analyzing the two cases triggered by pure sea breeze convergence line and by the merged sea breeze convergence and existing thunderstorm system. The results showed that: (1) When the environmental wind system is very weak, the moving sea breeze speed of Tianjin coastal sea breeze into the inland is about 15-18 km·h-1, and, after the leaving of sea breeze, temperature there decreases and humidity increases. (2) The sea breeze convergence line cooperates with the surface highly unstable region, triggering and strengthening the thunderstorm system, so that the thunderstorm warning can be 2 h in advance. (3) Thunderstorm cell forms near the sea breeze convergence line, which corresponds to the mesoscale vertical circulation in the frontal surface (to the sea side) of the tilting sea breeze front. (4) After sea breeze convergence line merges with the thunderstorm, the severely development of the thunderstorm is attributed to the accumulated water vapor near the sea breeze and the large zone of convergent updraft.
Using radar and intensive AWS (automatic meteorological station) data as well as VDRAS data whose temporal resolution is 12 min, horizontal and vertical resolutions are respectively 3 km and 1 km or so, the dynamical and thermodynamic processes of thunderstorm systems that are impacted by sea breeze convergence lines are investigated by analyzing the two cases triggered by pure sea breeze convergence line and by the merged sea breeze convergence and existing thunderstorm system. The results showed that: (1) When the environmental wind system is very weak, the moving sea breeze speed of Tianjin coastal sea breeze into the inland is about 15-18 km·h-1, and, after the leaving of sea breeze, temperature there decreases and humidity increases. (2) The sea breeze convergence line cooperates with the surface highly unstable region, triggering and strengthening the thunderstorm system, so that the thunderstorm warning can be 2 h in advance. (3) Thunderstorm cell forms near the sea breeze convergence line, which corresponds to the mesoscale vertical circulation in the frontal surface (to the sea side) of the tilting sea breeze front. (4) After sea breeze convergence line merges with the thunderstorm, the severely development of the thunderstorm is attributed to the accumulated water vapor near the sea breeze and the large zone of convergent updraft.
2014, 40(12):1549-1557.
DOI: 10.7519/j.issn.1000-0526.2014.12.014
Abstract:
Operational positioning, track and intensity forecast errors of tropical cyclones (TCs) over western North Pacific in 2013 are evaluated on the basis of CMA/STI’s Best track dataset. Meanwhile, the systematic biases of both global and regional models in track and intensity forecasts are analyzed. The results show that the performance of TC positioning is a little better than that in previous years, with an average error by all methods is 21.7 km. The average track forecast errors by the subjective methods of each province or autonomous regions are 80.2 km (24 h), 143.3 km (48 h) and 221.7 km (72 h), which are reduced by 13.9%, 13.4% and 20.9% compared to those in 2012. And the 24 h track forecast error of National Meteorological Centre (NMC) of CMA is less than 90 km for the first time. Global and regional models have steady improvement in the performance of track forecast, however, the models also display specific systematic biases. The overall performance of statistical forecast method is still better than numerical prediction method in intensity forecast. In the numerical prediction methods, the performance of regional models is slightly better than global models. Some global and regional models also have systematic biases in intensity prediction. The subjective methods predict well the 24 h landfall location of Typhoon 1308 “Cimaron”, but are not so good for Typhoon 1306 “Rumbia”, Typhoon 1311 “Utor”, Typhoon 1312 “Trami” and Typhoon 1323 “Fitow”.
Operational positioning, track and intensity forecast errors of tropical cyclones (TCs) over western North Pacific in 2013 are evaluated on the basis of CMA/STI’s Best track dataset. Meanwhile, the systematic biases of both global and regional models in track and intensity forecasts are analyzed. The results show that the performance of TC positioning is a little better than that in previous years, with an average error by all methods is 21.7 km. The average track forecast errors by the subjective methods of each province or autonomous regions are 80.2 km (24 h), 143.3 km (48 h) and 221.7 km (72 h), which are reduced by 13.9%, 13.4% and 20.9% compared to those in 2012. And the 24 h track forecast error of National Meteorological Centre (NMC) of CMA is less than 90 km for the first time. Global and regional models have steady improvement in the performance of track forecast, however, the models also display specific systematic biases. The overall performance of statistical forecast method is still better than numerical prediction method in intensity forecast. In the numerical prediction methods, the performance of regional models is slightly better than global models. Some global and regional models also have systematic biases in intensity prediction. The subjective methods predict well the 24 h landfall location of Typhoon 1308 “Cimaron”, but are not so good for Typhoon 1306 “Rumbia”, Typhoon 1311 “Utor”, Typhoon 1312 “Trami” and Typhoon 1323 “Fitow”.
2014, 40(12):1558-1564.
DOI: 10.7519/j.issn.1000-0526.2014.12.015
Abstract:
The main characteristics of the general atmospheric circulation in September 2014 are as follows: There is one polar vortex center in the Northern Hemisphere. In the middle high latitudes, the circulation presents a six wave pattern. The subtropical high is almost the same as its climatological mean. Meanwhile, monthly mean precipitation amount is 80.7 mm, which is 23.6% more than its climatological mean (65.3 mm). Monthly mean temperature is 17.1℃, which is a little higher than its climatological mean (16.6℃). There were 6 heavy rainfall events in this month. Extreme continuous rainfall events have occurred at 113 stations in northeast part of Sichuan Basin, central and south part of Shaanxi, Henan and other places, with extreme continuous precipitation events observed at 96 stations in central and south part of Shaanxi, southwest part of Shanxi, western part of Henan and northeast part of Sichuan. Typhoon “Kalmaegl” and “Fung wong” have landed in China successively in this month; continuous rainfall process occurred in West China, most part of Huang Huai Area, southwest part of North China and other places; the drought of Gansu, Shaanxi and Henan in the early time is released.
The main characteristics of the general atmospheric circulation in September 2014 are as follows: There is one polar vortex center in the Northern Hemisphere. In the middle high latitudes, the circulation presents a six wave pattern. The subtropical high is almost the same as its climatological mean. Meanwhile, monthly mean precipitation amount is 80.7 mm, which is 23.6% more than its climatological mean (65.3 mm). Monthly mean temperature is 17.1℃, which is a little higher than its climatological mean (16.6℃). There were 6 heavy rainfall events in this month. Extreme continuous rainfall events have occurred at 113 stations in northeast part of Sichuan Basin, central and south part of Shaanxi, Henan and other places, with extreme continuous precipitation events observed at 96 stations in central and south part of Shaanxi, southwest part of Shanxi, western part of Henan and northeast part of Sichuan. Typhoon “Kalmaegl” and “Fung wong” have landed in China successively in this month; continuous rainfall process occurred in West China, most part of Huang Huai Area, southwest part of North China and other places; the drought of Gansu, Shaanxi and Henan in the early time is released.
Mobile website
® 2024 All Rights Reserved
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
ISSN:1000-0526 CN:11-2282/P