ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 39,Issue 12,2013 Table of Contents
CHEN Guichuan
,
CHEN Yun
,
ZHANG Yong
,
CHEN Peng
,
WANG Huan
,
LI Zhongju
,
LIU Nian
,
ZHAI Danhua
,
LONG Meixi
2013, 39(12):1529-1541.
DOI: 10.7519/j.issn.1000-0526.2013.12.001
Abstract:
Based on conventional observation data, ECMWF analysis field data, regional automatic station data, Doppler radar data, and the products of SWAN etc. the southwest vortex rainstorm process on 21 July 2012 and extreme short time severe rainfall observed at Panlong Station in the process are analyzed. The results indicate that: the rainstorm is triggered by surface cold air which contributes to the development of convergence ascent movement in the east of the southwest vortex and upper level divergence with the backgroud of northern trough and southern vortex. The intrusion of cold air from the west of the southwest vortex, which is also the important factor for the formation of surface convergence line, is the direct cause of the formation of 925 hPa cold front with “S” pattern. Extreme short time severe rainfall occurs in the north to the middle part of mesoscale rainbelt that is in the east of southwest vortex combining with surface convergence line, and meanwhile, TBB reaches the lowest in the center of MCC when the rainfall is the most intensive. The radar echoes show that the intersection of air in the two sides of southwest vortex advances the formation of β meso scale cyclonic circulation. The low level jet stream provides plenty of water vapor and energy conditions for the severe precipitation and reinforces vertical wind shear between middle and lower levels, contributing to the development and sustainment of heavy precipitation supercell storm. The extreme short time precipitation of Panlong Station results from the sustainable development of meso β scale cyclonic circulation associated with deep meso cyclone near the center of meso β scale cyclonic circulation in southwest vortex.
Based on conventional observation data, ECMWF analysis field data, regional automatic station data, Doppler radar data, and the products of SWAN etc. the southwest vortex rainstorm process on 21 July 2012 and extreme short time severe rainfall observed at Panlong Station in the process are analyzed. The results indicate that: the rainstorm is triggered by surface cold air which contributes to the development of convergence ascent movement in the east of the southwest vortex and upper level divergence with the backgroud of northern trough and southern vortex. The intrusion of cold air from the west of the southwest vortex, which is also the important factor for the formation of surface convergence line, is the direct cause of the formation of 925 hPa cold front with “S” pattern. Extreme short time severe rainfall occurs in the north to the middle part of mesoscale rainbelt that is in the east of southwest vortex combining with surface convergence line, and meanwhile, TBB reaches the lowest in the center of MCC when the rainfall is the most intensive. The radar echoes show that the intersection of air in the two sides of southwest vortex advances the formation of β meso scale cyclonic circulation. The low level jet stream provides plenty of water vapor and energy conditions for the severe precipitation and reinforces vertical wind shear between middle and lower levels, contributing to the development and sustainment of heavy precipitation supercell storm. The extreme short time precipitation of Panlong Station results from the sustainable development of meso β scale cyclonic circulation associated with deep meso cyclone near the center of meso β scale cyclonic circulation in southwest vortex.
2013, 39(12):1542-1549.
DOI: 10.7519/j.issn.1000-0526.2013.12.002
Abstract:
This paper diagnostically analyzes the 721 Beijing rainstorm weather process caused by eastward shift of Hetao cyclone. The results show that: Hetao cyclone is the main impact system on the rainstorm in Beijing on 21 July 2012, and the forcing effect of upper divergence zone and the trend of lower troposphere frontal zone “guide” the Hetao cyclone to change the conventional path to the north, forcing its eastward shift and directly affecting the region of Hebei and Beijing. In the process of Hetao cyclone’s moving eastward along the frontal zone, the warm heart barotropic cyclones change to be baroclinic cyclones. Meanwhile, the potential energy of frontal zone is changed into kinetic energy to promote the rapid development of the Hetao cyclone, forming a positive feedback effect, and making the intensity of precipitation continuously enhance from west to east. The effects of the Hetao cyclone in the Beijing rainstorm are dynamic lifting, enhancing water vapor transport and triggering unstable energy. In the afternoon, warm front of the Hetao cyclone triggers the release of potential instability energy, generating strong convective system, forming mesoscale convective complexes (MCC) in the Beijing area, and finally, intensifying the precipitation further more. There are the main causes of the severe torrential rains in Beijing on 21 July. In addition, the topographic lifting in the southeast airflow strengthens the rainstorm as well. Therefore, this severe rainstorm is caused by a variety of superimposed favorable factors.
This paper diagnostically analyzes the 721 Beijing rainstorm weather process caused by eastward shift of Hetao cyclone. The results show that: Hetao cyclone is the main impact system on the rainstorm in Beijing on 21 July 2012, and the forcing effect of upper divergence zone and the trend of lower troposphere frontal zone “guide” the Hetao cyclone to change the conventional path to the north, forcing its eastward shift and directly affecting the region of Hebei and Beijing. In the process of Hetao cyclone’s moving eastward along the frontal zone, the warm heart barotropic cyclones change to be baroclinic cyclones. Meanwhile, the potential energy of frontal zone is changed into kinetic energy to promote the rapid development of the Hetao cyclone, forming a positive feedback effect, and making the intensity of precipitation continuously enhance from west to east. The effects of the Hetao cyclone in the Beijing rainstorm are dynamic lifting, enhancing water vapor transport and triggering unstable energy. In the afternoon, warm front of the Hetao cyclone triggers the release of potential instability energy, generating strong convective system, forming mesoscale convective complexes (MCC) in the Beijing area, and finally, intensifying the precipitation further more. There are the main causes of the severe torrential rains in Beijing on 21 July. In addition, the topographic lifting in the southeast airflow strengthens the rainstorm as well. Therefore, this severe rainstorm is caused by a variety of superimposed favorable factors.
YANG Xiaoxia
,
WU Wei
,
JIANG Peng
,
XU Juan
,
HU Shunqi
,
DIAO Xiuguang
,
GAO Liuxi
,
WANG Wenqing
,
HUA Wenli
2013, 39(12):1550-1560.
DOI: 10.7519/j.issn.1000-0526.2013.12.003
Abstract:
By using dense convective observational data, satellite images, radar data and NCEP/NCAR (1°×1°) reanalysis data, the weather systems for the three extreme heavy rainfalls are diagnosed and analyzed. The results show that westerly trough at 500 hPa and low level warm shear line are the main impact system for the three heavy rainfalls. Before the rainfalls, high temperature, high humidity and convection instability exist in lower atmosphere. The ascending movement caused by convergence of low level shear line and the warm and wet advection and the surface wind convergence line trigger the release of convection instability energy, producing strong convection and extreme rainfall. The strong vertical wind shear makes convection systematically develop. During the heavy rainfalls dry and cold airs invade from middle upper level so that convection instability gets intensified. On the other hand, the dry and cold airs with high potential vortex intruding from middle upper level induce mesoscale vortex to develop in low level atmosphere so that convergence and ascending movement increase. That the warm and wet airs in low level helically converge and encounter the dry and cold airs from middle higher level, so the water vapour condensation and rain intensity increase. The periods when the dry and cold airs intrude from middle higher level correspond with the periods of extremely strong rains. Terrain plays an important part in local and short time extreme heavy rainfalls. The position and intensity for 500 hPa westerly trough and 850 hPa warm shear line are different and the intensity and tracks of the dry and cold airs at upper level are different, the convective cloud’s development, evolution, movement and internal structure are different, causing the difference of rainstorm areas and intensity.
By using dense convective observational data, satellite images, radar data and NCEP/NCAR (1°×1°) reanalysis data, the weather systems for the three extreme heavy rainfalls are diagnosed and analyzed. The results show that westerly trough at 500 hPa and low level warm shear line are the main impact system for the three heavy rainfalls. Before the rainfalls, high temperature, high humidity and convection instability exist in lower atmosphere. The ascending movement caused by convergence of low level shear line and the warm and wet advection and the surface wind convergence line trigger the release of convection instability energy, producing strong convection and extreme rainfall. The strong vertical wind shear makes convection systematically develop. During the heavy rainfalls dry and cold airs invade from middle upper level so that convection instability gets intensified. On the other hand, the dry and cold airs with high potential vortex intruding from middle upper level induce mesoscale vortex to develop in low level atmosphere so that convergence and ascending movement increase. That the warm and wet airs in low level helically converge and encounter the dry and cold airs from middle higher level, so the water vapour condensation and rain intensity increase. The periods when the dry and cold airs intrude from middle higher level correspond with the periods of extremely strong rains. Terrain plays an important part in local and short time extreme heavy rainfalls. The position and intensity for 500 hPa westerly trough and 850 hPa warm shear line are different and the intensity and tracks of the dry and cold airs at upper level are different, the convective cloud’s development, evolution, movement and internal structure are different, causing the difference of rainstorm areas and intensity.
2013, 39(12):1561-1569.
DOI: 10.7519/j.issn.1000-0526.2013.12.004
Abstract:
Based on various conventional observations and the NCEP reanalysis data, the associated thermodynamics, dynamic mechanisms, instability mechanism and the features of satellite images for the occurrence and evolution of severe rainstorm caused by typhoon Bolaven (1215) and cold air in central Heilongjiang are analyzed. The results suggested that the severe rainstorm results from the interaction of middle and low latitude circulation systems. The southeastward advance of cold air greatly enhances the baroclinicity, in favor of the development of baroclinic disturbances. During this rain storm process, the co existing of instability in the low troposphere and moist symmetry instability in the middle troposphere provides a powerful ambient condition for the occurrence of this rainstorm. The positive vortex tube in the mid low layer of the atmosphere drives the development of convection. Strong convergence at low levels and divergence at high levels, and mesoscale circulation provides dynamic conditions. The southerly and southeast jet in the east side of typhoon center provides abundant moisture and thermodynamic conditions. In addition, the terrain helps to increase the intensity of the rainstorm as well.
Based on various conventional observations and the NCEP reanalysis data, the associated thermodynamics, dynamic mechanisms, instability mechanism and the features of satellite images for the occurrence and evolution of severe rainstorm caused by typhoon Bolaven (1215) and cold air in central Heilongjiang are analyzed. The results suggested that the severe rainstorm results from the interaction of middle and low latitude circulation systems. The southeastward advance of cold air greatly enhances the baroclinicity, in favor of the development of baroclinic disturbances. During this rain storm process, the co existing of instability in the low troposphere and moist symmetry instability in the middle troposphere provides a powerful ambient condition for the occurrence of this rainstorm. The positive vortex tube in the mid low layer of the atmosphere drives the development of convection. Strong convergence at low levels and divergence at high levels, and mesoscale circulation provides dynamic conditions. The southerly and southeast jet in the east side of typhoon center provides abundant moisture and thermodynamic conditions. In addition, the terrain helps to increase the intensity of the rainstorm as well.
2013, 39(12):1570-1579.
DOI: 10.7519/j.issn.1000-0526.2013.12.005
Abstract:
Cold vortex is firstly defined. Using synoptic chart from April to September during 2000-2011, the sptio temporal distribution and life characteristics of cold vortex are studied. Besides, disaster weather data from 176 stations in Beijing Tianjin Hebei region from April to September during 2000-2011 and NCEP 1°×1° reanalysis data are used to analyze the sptio temporal distribution characteristics of continuous hailfall of Beijing, Tianjin, Hebei Region and its relations with cold vortex. The results show that the number of cold vortexes is increasing, which mainly occur from Northeast China to the east of Lake Baikal, and long lived cold vortexes account for 70%. It is the long lived vortex that causes the continuous haifall in the Beijing Tianjin Hebei Region and the continuous hail in the context of cold vortex exhibits significant diurnal variation, appearing more in mountains than on plains, more in the north than in the south. Continuous hail mainly occurs in the south of vortex center, and can occur in any stages of cold vortex. The distance between continuous hail and cold vortex is about 200-1200 km. The continuous hailfalls are mainly affected by the cold vortex and its rear transverse trough, and occur in different position corresponding to cold vortex with different speeds.
Cold vortex is firstly defined. Using synoptic chart from April to September during 2000-2011, the sptio temporal distribution and life characteristics of cold vortex are studied. Besides, disaster weather data from 176 stations in Beijing Tianjin Hebei region from April to September during 2000-2011 and NCEP 1°×1° reanalysis data are used to analyze the sptio temporal distribution characteristics of continuous hailfall of Beijing, Tianjin, Hebei Region and its relations with cold vortex. The results show that the number of cold vortexes is increasing, which mainly occur from Northeast China to the east of Lake Baikal, and long lived cold vortexes account for 70%. It is the long lived vortex that causes the continuous haifall in the Beijing Tianjin Hebei Region and the continuous hail in the context of cold vortex exhibits significant diurnal variation, appearing more in mountains than on plains, more in the north than in the south. Continuous hail mainly occurs in the south of vortex center, and can occur in any stages of cold vortex. The distance between continuous hail and cold vortex is about 200-1200 km. The continuous hailfalls are mainly affected by the cold vortex and its rear transverse trough, and occur in different position corresponding to cold vortex with different speeds.
2013, 39(12):1580-1590.
DOI: 10.7519/j.issn.1000-0526.2013.12.006
Abstract:
Based on the routine observational data, FY2C TBB data, radar data, NCEP reanalysis data and LAPS analysis data, a comparative analysis on mesoscale characteristics of two torrential rain processes in Hunan Province in June 2011 was analyzed. The results show that: The two processes belong to the type of low vortex and cold trough rainstorm, but their mesoscale characteristics, precipitation nature and environmental conditions are different. The rainstorm on 9 June 2011 is generated by a meso β scale low vortex, which is stable and immobile during the process. The satellite image manifests a mesoscale convective cloud cluster which develops severely, and the radar echoes are convective precipitation echoes in the earlier stage and transform to convective stratiform mixed clouds echoes in the later stage. In comparison, the rainstorm on 13 June 2011 is mainly produced by mesoscale convective shear lines which maintain for a long time and move slowly. The satellite images show it a convective cloud band that exits for a long time, and the radar echoes are convective stratiform mixed clouds echoes. The establishment of vapour transfer channels and strong convergence of water vapor in the middle and low troposphere provide favorable conditions for the mesoscale convective system. The two severe rainstorms both occur in the unstable stratifications with high temperature and humidity and strong ascending motions. The ascending movements caused by the dynamic forcing in the frontal zone enhance upward transfer of energy and water vapor from low levels. The obvious compensation descending airflows appear on the north and south sides of the deep vertical motion in the first process, but in the second process, the ascending motion is inclined, and the compensation descending airflows only appear on the south side.
Based on the routine observational data, FY2C TBB data, radar data, NCEP reanalysis data and LAPS analysis data, a comparative analysis on mesoscale characteristics of two torrential rain processes in Hunan Province in June 2011 was analyzed. The results show that: The two processes belong to the type of low vortex and cold trough rainstorm, but their mesoscale characteristics, precipitation nature and environmental conditions are different. The rainstorm on 9 June 2011 is generated by a meso β scale low vortex, which is stable and immobile during the process. The satellite image manifests a mesoscale convective cloud cluster which develops severely, and the radar echoes are convective precipitation echoes in the earlier stage and transform to convective stratiform mixed clouds echoes in the later stage. In comparison, the rainstorm on 13 June 2011 is mainly produced by mesoscale convective shear lines which maintain for a long time and move slowly. The satellite images show it a convective cloud band that exits for a long time, and the radar echoes are convective stratiform mixed clouds echoes. The establishment of vapour transfer channels and strong convergence of water vapor in the middle and low troposphere provide favorable conditions for the mesoscale convective system. The two severe rainstorms both occur in the unstable stratifications with high temperature and humidity and strong ascending motions. The ascending movements caused by the dynamic forcing in the frontal zone enhance upward transfer of energy and water vapor from low levels. The obvious compensation descending airflows appear on the north and south sides of the deep vertical motion in the first process, but in the second process, the ascending motion is inclined, and the compensation descending airflows only appear on the south side.
2013, 39(12):1591-1599.
DOI: 10.7519/j.issn.1000-0526.2013.12.007
Abstract:
Using NCEP reanalysis data, conventional weather data and Doppler radar data, the characteristics of the synoptic and mesoscale meteorological background are analyzed for a torrential rainfall over Xiaoshipeng Town of Yingkou City in Liaoning Province. The results show that the Pacific subtropical high extends to the west, a strong tropical storm Muifa moves to the northwest after it lands; the southwest airflow at the east side of the tropical storm transports abundant water vapor to Liaoning, and the weak cold air of Baikal Lake moves south along the ridge before the northwest flow impacts Liaoning. Besides the existence of a deep wet layer, a narrow CAPE zone and a relative weak vertical wind sheer are beneficial to severe convective rainfall. The new mesoscale convective cells are generated continuously during the heavy rainfall. There exists a maximum wind speed zone of 24 m·s-1 in the lower layer and a strong radar echo with 35 dBz above 5 km. And the variation of the low level southwest jet is in step with the variation of rainfall intensity. The cyclonic convergence of the warm moist air in the mid low level triggers and strengthens convection. The nonstop generation of mesoscale severe convective cells and the water vapor transport from the low level northwest jet push the radar echo to above 40 dBz, lasting for more than 5 hours. In addition, the valley torrain has great influence on the torrential rain as well.
Using NCEP reanalysis data, conventional weather data and Doppler radar data, the characteristics of the synoptic and mesoscale meteorological background are analyzed for a torrential rainfall over Xiaoshipeng Town of Yingkou City in Liaoning Province. The results show that the Pacific subtropical high extends to the west, a strong tropical storm Muifa moves to the northwest after it lands; the southwest airflow at the east side of the tropical storm transports abundant water vapor to Liaoning, and the weak cold air of Baikal Lake moves south along the ridge before the northwest flow impacts Liaoning. Besides the existence of a deep wet layer, a narrow CAPE zone and a relative weak vertical wind sheer are beneficial to severe convective rainfall. The new mesoscale convective cells are generated continuously during the heavy rainfall. There exists a maximum wind speed zone of 24 m·s-1 in the lower layer and a strong radar echo with 35 dBz above 5 km. And the variation of the low level southwest jet is in step with the variation of rainfall intensity. The cyclonic convergence of the warm moist air in the mid low level triggers and strengthens convection. The nonstop generation of mesoscale severe convective cells and the water vapor transport from the low level northwest jet push the radar echo to above 40 dBz, lasting for more than 5 hours. In addition, the valley torrain has great influence on the torrential rain as well.
2013, 39(12):1600-1608.
DOI: 10.7519/j.issn.1000-0526.2013.12.008
Abstract:
There are 3.2 tropical cyclones (TCs) entering into the East China Sea on average every year. Recurvature or landfall of these TCs will make different effects. The comparative analysis on the situations and physical fields of recurving TCs and landfalling TCs shows that in the case of recurving TCs, subtropical high is weak and the east part of it is in massive shape; westerly belt is strong and close to TC; the middle and upper level westerly jets are significant and get intensified as they move eastward; the upper level divergence at the northeast of TC enhances while notable positive vorticity advection is found in the middle and low levels of TC with clear advection center. However, in the case of landfalling TCs, subtropical high is strong and in broad belt shape; westerly belt is weak and distant from TC; westerly jet is not notable and is not intensified; the upper level jet center is located in the northwest and north of TC; no remarkable upper level divergence occurs in the northeast of TC and the middle and low level positive vorticity advection is located in the northwest and north of TC with no notable advection center. The characteristics above can be seen 72 hours before the recurvature or landfall of TCs, and get much clearer in 48 hours before the events.
There are 3.2 tropical cyclones (TCs) entering into the East China Sea on average every year. Recurvature or landfall of these TCs will make different effects. The comparative analysis on the situations and physical fields of recurving TCs and landfalling TCs shows that in the case of recurving TCs, subtropical high is weak and the east part of it is in massive shape; westerly belt is strong and close to TC; the middle and upper level westerly jets are significant and get intensified as they move eastward; the upper level divergence at the northeast of TC enhances while notable positive vorticity advection is found in the middle and low levels of TC with clear advection center. However, in the case of landfalling TCs, subtropical high is strong and in broad belt shape; westerly belt is weak and distant from TC; westerly jet is not notable and is not intensified; the upper level jet center is located in the northwest and north of TC; no remarkable upper level divergence occurs in the northeast of TC and the middle and low level positive vorticity advection is located in the northwest and north of TC with no notable advection center. The characteristics above can be seen 72 hours before the recurvature or landfall of TCs, and get much clearer in 48 hours before the events.
2013, 39(12):1609-1615.
DOI: 10.7519/j.issn.1000-0526.2013.12.009
Abstract:
In this paper the suitability of Euclidean distance, similar disparity, similarity coefficient, correlation coefficient and best similarity coefficient used as a similarity measure in meteorological grid dataset is discussed. The results show that some special systems’ position and intensity cannot be expressed correctly by distance algorithm. But using similar disparity, similarity coefficient, correlation coefficient and best similarity coefficient, two meteorological grid datasets’ spatial distribution and the change trend are considered separately, so the similar ambient field can be found in the long history dataset, which can be applied in operation. In order to evaluate the similarity measures’ operational application, the similar ambient field corresponding to tropical cyclone (TC) track’s motion quantity is referenced in current source TC track forecast. The results show that 24 h moving direction forecast accuracy is better than that of 24 h track forecast and the similar disparity is better than other algorithm in track forecast, but the best similarity coefficient is better than other algorithm in moving direction forecast. By the query of similar ambient field, a similar TC ensemble corresponding to similar ambient field is found, which can be referenced in TC operational, forecast or research.
In this paper the suitability of Euclidean distance, similar disparity, similarity coefficient, correlation coefficient and best similarity coefficient used as a similarity measure in meteorological grid dataset is discussed. The results show that some special systems’ position and intensity cannot be expressed correctly by distance algorithm. But using similar disparity, similarity coefficient, correlation coefficient and best similarity coefficient, two meteorological grid datasets’ spatial distribution and the change trend are considered separately, so the similar ambient field can be found in the long history dataset, which can be applied in operation. In order to evaluate the similarity measures’ operational application, the similar ambient field corresponding to tropical cyclone (TC) track’s motion quantity is referenced in current source TC track forecast. The results show that 24 h moving direction forecast accuracy is better than that of 24 h track forecast and the similar disparity is better than other algorithm in track forecast, but the best similarity coefficient is better than other algorithm in moving direction forecast. By the query of similar ambient field, a similar TC ensemble corresponding to similar ambient field is found, which can be referenced in TC operational, forecast or research.
2013, 39(12):1616-1625.
DOI: 10.7519/j.issn.1000-0526.2013.12.010
Abstract:
The spring (March to May) precipitation of 18 stations over South China during the period of 1951-2007 are analyzed by using the method of EOF analysis. The results show that the spatial distribution of spring precipitation over South China shows 4 main patterns that are the consistency of the whole region, anti phase between east and west, anti phase between north and south, anti phase between northeast and southwest etc. The second eigenvector of the spring rainfall in South China mainly reflects the zonal distribution of non uniform, so the spring rainfall pattern in South China are divided into the type of west flood and east drought, east flood and west drought. The characteristics of its associated atmospheric circulation background in the zonal distribution of spring precipitation anomalies years are analyzed by using NCEP reanalysis data, and the results show that, in the west flood and east drought years, an positive anomaly center of sea level pressure field and height field at 850 hPa is located in the northwest of South China, which is beneficial to the cold air down south. A negative anomalous sea level pressure and height at 850 hPa appear in the south of this positive center, and there presents a positive anomalous sea level pressure and height at 850 hPa in the east of South China and its eastern sea area. An southeast wind anomaly occurs in the west of South China, while there is an anomalous northeast wind in the east of South China. The wind field and water vapor transport field present abnormal convergence in the west of South China, but in the east of South China they perform an abnormal divergence, causing more precipitation in the west of South China but less precipitation in the east of South China. In the meantime, vorticity field at 850 hPa, divergence field at 200 hPa, vertical velocity field at 850 hPa and temperature field at 1000 hPa all show the circulation situation that is favorable for increase of precipitation in the west of South China and decrease of precipitation in the east of South China. In the west drought and east flood years, the situation is basically opposite.
The spring (March to May) precipitation of 18 stations over South China during the period of 1951-2007 are analyzed by using the method of EOF analysis. The results show that the spatial distribution of spring precipitation over South China shows 4 main patterns that are the consistency of the whole region, anti phase between east and west, anti phase between north and south, anti phase between northeast and southwest etc. The second eigenvector of the spring rainfall in South China mainly reflects the zonal distribution of non uniform, so the spring rainfall pattern in South China are divided into the type of west flood and east drought, east flood and west drought. The characteristics of its associated atmospheric circulation background in the zonal distribution of spring precipitation anomalies years are analyzed by using NCEP reanalysis data, and the results show that, in the west flood and east drought years, an positive anomaly center of sea level pressure field and height field at 850 hPa is located in the northwest of South China, which is beneficial to the cold air down south. A negative anomalous sea level pressure and height at 850 hPa appear in the south of this positive center, and there presents a positive anomalous sea level pressure and height at 850 hPa in the east of South China and its eastern sea area. An southeast wind anomaly occurs in the west of South China, while there is an anomalous northeast wind in the east of South China. The wind field and water vapor transport field present abnormal convergence in the west of South China, but in the east of South China they perform an abnormal divergence, causing more precipitation in the west of South China but less precipitation in the east of South China. In the meantime, vorticity field at 850 hPa, divergence field at 200 hPa, vertical velocity field at 850 hPa and temperature field at 1000 hPa all show the circulation situation that is favorable for increase of precipitation in the west of South China and decrease of precipitation in the east of South China. In the west drought and east flood years, the situation is basically opposite.
2013, 39(12):1626-1634.
DOI: 10.7519/j.issn.1000-0526.2013.12.011
Abstract:
Quality control (QC) of radiosonde data is the important guarantee for radiosonde data assimilation in numerical model. As the numerical model resolution is getting higher and higher, the drift distance with height of radiosonde balloon needs to be considered in data assimilation. In this paper, temperature characteristics of radiosonde observation from 119 radiosonde stations are analyzed by comparing with T639 model analysis field (0.28125°×0.28125°) and temperature profile of the COSMIC radio occultation. Meanwhile, a bi weight mean quality control method for radiosonde temperature is studied combining the drift information and the error sources of radiosonde temperature. The results show that the drift distance of radiosonde balloon increases with height. The maximum drift rate appears in the range of 300-100 hPa. The bi weight mean quality control method ensures the data quality after the quality control. The temperature error sources and drift information affect the results of quality control. The amount of outliers at high levels above 300 hPa is reduced when the error source is considered. The outliers of the maximum drift rate levels are reduced when the drift information is considered. The elevation differences between the model terrain and radiosonde sites have impacts on the background consistent check. When the height of radiosonde sites is lower than model terrain, some outliers at low levels will appear. And there is a positive correlation between outliers and elevation difference, the larger elevation difference is, the more outliers there are.
Quality control (QC) of radiosonde data is the important guarantee for radiosonde data assimilation in numerical model. As the numerical model resolution is getting higher and higher, the drift distance with height of radiosonde balloon needs to be considered in data assimilation. In this paper, temperature characteristics of radiosonde observation from 119 radiosonde stations are analyzed by comparing with T639 model analysis field (0.28125°×0.28125°) and temperature profile of the COSMIC radio occultation. Meanwhile, a bi weight mean quality control method for radiosonde temperature is studied combining the drift information and the error sources of radiosonde temperature. The results show that the drift distance of radiosonde balloon increases with height. The maximum drift rate appears in the range of 300-100 hPa. The bi weight mean quality control method ensures the data quality after the quality control. The temperature error sources and drift information affect the results of quality control. The amount of outliers at high levels above 300 hPa is reduced when the error source is considered. The outliers of the maximum drift rate levels are reduced when the drift information is considered. The elevation differences between the model terrain and radiosonde sites have impacts on the background consistent check. When the height of radiosonde sites is lower than model terrain, some outliers at low levels will appear. And there is a positive correlation between outliers and elevation difference, the larger elevation difference is, the more outliers there are.
2013, 39(12):1635-1641.
DOI: 10.7519/j.issn.1000-0526.2013.12.012
Abstract:
Based on the summer precipitation data of 20 stations in Beijing and its urban development statistical data during 1971-2010, and defining the 95th percentile as the threshold of extreme precipitation for each station, the characteristics of the spatio temporal distribution and the linear trend of extreme precipitation events with different durations and city effect of local precipitation are analyzed. The results indicate that the extreme precipitation event frequency shows a gradual decreasing trend from west to east, which is remarkably different from the precipitation distribution. There exist distinctive spatial differences in the distributive features and changes of the threshold values, frequencies, and rainfall of extreme precipitation events. The averaged intensity and frequency of extreme precipitation in Beijing Area show a descending trend in the past 40 years and have significant difference at interannual and interdecadal changes. The impact of urbanization on the intensity and frequency of extreme precipitation has become more and more apparent. Urbanization can not only enhance rain island effect but also make an influence on precipitation in downwind areas; moreover, urbanization can also increase the intensity and frequency of local extreme precipitation.
Based on the summer precipitation data of 20 stations in Beijing and its urban development statistical data during 1971-2010, and defining the 95th percentile as the threshold of extreme precipitation for each station, the characteristics of the spatio temporal distribution and the linear trend of extreme precipitation events with different durations and city effect of local precipitation are analyzed. The results indicate that the extreme precipitation event frequency shows a gradual decreasing trend from west to east, which is remarkably different from the precipitation distribution. There exist distinctive spatial differences in the distributive features and changes of the threshold values, frequencies, and rainfall of extreme precipitation events. The averaged intensity and frequency of extreme precipitation in Beijing Area show a descending trend in the past 40 years and have significant difference at interannual and interdecadal changes. The impact of urbanization on the intensity and frequency of extreme precipitation has become more and more apparent. Urbanization can not only enhance rain island effect but also make an influence on precipitation in downwind areas; moreover, urbanization can also increase the intensity and frequency of local extreme precipitation.
2013, 39(12):1642-1648.
DOI: 10.7519/j.issn.1000-0526.2013.12.013
Abstract:
This paper focuses on critical hazard rainfall of valleys that only has water level records but no water flow records. After statistically analysing the water stage data and the rainfall data during floods of recent years, this paper gets the relationship between rainfall and floods. With this relationship and water level records of historical floods, the critical hazard rainfall of valleys is obtained. Furthermore, this paper estimates the risk levels of each critical rainfall by simulating submergence with submergence model. By contrasting the simulated result to history records of some serious floods, the rainfall threshold got from statistic is proved to be reasonable. Due to the clear submerging depth and blurry occurrence time of flood records, the rainfall threshold obtained still needs to be verified. Although the occurring time of the estimated hazards disaccords with reality, the low level risk rainfall threshold got verified in rainy season of 2012. It can be used to predict a low risk rainfall flood by lowering the risk critical rainfall reasonably. For other levels of risk rainfall, verification is very necessary once new flood examples are collected.
This paper focuses on critical hazard rainfall of valleys that only has water level records but no water flow records. After statistically analysing the water stage data and the rainfall data during floods of recent years, this paper gets the relationship between rainfall and floods. With this relationship and water level records of historical floods, the critical hazard rainfall of valleys is obtained. Furthermore, this paper estimates the risk levels of each critical rainfall by simulating submergence with submergence model. By contrasting the simulated result to history records of some serious floods, the rainfall threshold got from statistic is proved to be reasonable. Due to the clear submerging depth and blurry occurrence time of flood records, the rainfall threshold obtained still needs to be verified. Although the occurring time of the estimated hazards disaccords with reality, the low level risk rainfall threshold got verified in rainy season of 2012. It can be used to predict a low risk rainfall flood by lowering the risk critical rainfall reasonably. For other levels of risk rainfall, verification is very necessary once new flood examples are collected.
2013, 39(12):1649-1655.
DOI: 10.7519/j.issn.1000-0526.2013.12.014
Abstract:
In recent years, in the context of climate change and extreme climate events, drought agro meteorological disasters which occur frequently has taken a serious threat for our food production and agricultural sustainable development. Selecting or building suitable agricultural drought disaster risk indicators for drought risk zoning, and on this basis, determining premium rates is very valuable in enriching agricultural insurance model and promoting the stability and development of the agricultural insurance business. Based on the natural water deficit rate index, precipitation anomalies of the percentage rate and drought index, this paper builds drought comprehensive risk index, and carries out drought risk zoning study. Then, using the revised premium rate, the premium ratemaking model applicable to the study area is worked out so as to search for a more comprehensive improvement of the current agricultural insurance business insurance model, and achieve the sustainable and healthy development of the winter wheat agricultural insurance.
In recent years, in the context of climate change and extreme climate events, drought agro meteorological disasters which occur frequently has taken a serious threat for our food production and agricultural sustainable development. Selecting or building suitable agricultural drought disaster risk indicators for drought risk zoning, and on this basis, determining premium rates is very valuable in enriching agricultural insurance model and promoting the stability and development of the agricultural insurance business. Based on the natural water deficit rate index, precipitation anomalies of the percentage rate and drought index, this paper builds drought comprehensive risk index, and carries out drought risk zoning study. Then, using the revised premium rate, the premium ratemaking model applicable to the study area is worked out so as to search for a more comprehensive improvement of the current agricultural insurance business insurance model, and achieve the sustainable and healthy development of the winter wheat agricultural insurance.
2013, 39(12):1656-1662.
DOI: 10.7519/j.issn.1000-0526.2013.12.015
Abstract:
By using monthly precipitation data of 30 meteorological stations within the apple production area in Shaanxi Province from 1961 to 2010, the standardized precipitation index SPI3, SPI6, SPI9 and SPI12 were calculated. Results show that annual SPI12, spring summer autumn SPI9 and autumn SPI3 have a significant linear downward trend (P<0.05) and drought intensity tends to increase. The frequency of light drought, mild drought, severe drought and extreme drought in the study area are 16%, 6%, 4% and 0% correspondingly. Kriging interpolation method is used to draw drought frequency distribution map based on SPI value of the stations in the study area. The spatial distribution of annual drought frequency shows that four high drought frequency areas distribute with certain intervals from south to north and the drought frequency in Guanzhong Area is the highest. The spatial distribution of spring summer autumn drought frequency has a similar regulation with the frequency of annual drought. The distribution of winter spring drought frequency generally shows the trend of being higher in south than in north. The distribution of winter spring drought frequency shows that the frequency in middle is higher than in the both sides. The drought frequency in Guanzhong Area is the highest in spring, while that in the east of Weibei Area is the highest in the other seasons. In addition, 76.4% apple orchards do not have irrigation facilities, so this research is of some significance for establishing targeted drought relief measures and emergency preplans.
By using monthly precipitation data of 30 meteorological stations within the apple production area in Shaanxi Province from 1961 to 2010, the standardized precipitation index SPI3, SPI6, SPI9 and SPI12 were calculated. Results show that annual SPI12, spring summer autumn SPI9 and autumn SPI3 have a significant linear downward trend (P<0.05) and drought intensity tends to increase. The frequency of light drought, mild drought, severe drought and extreme drought in the study area are 16%, 6%, 4% and 0% correspondingly. Kriging interpolation method is used to draw drought frequency distribution map based on SPI value of the stations in the study area. The spatial distribution of annual drought frequency shows that four high drought frequency areas distribute with certain intervals from south to north and the drought frequency in Guanzhong Area is the highest. The spatial distribution of spring summer autumn drought frequency has a similar regulation with the frequency of annual drought. The distribution of winter spring drought frequency generally shows the trend of being higher in south than in north. The distribution of winter spring drought frequency shows that the frequency in middle is higher than in the both sides. The drought frequency in Guanzhong Area is the highest in spring, while that in the east of Weibei Area is the highest in the other seasons. In addition, 76.4% apple orchards do not have irrigation facilities, so this research is of some significance for establishing targeted drought relief measures and emergency preplans.
2013, 39(12):1663-1670.
DOI: 10.7519/j.issn.1000-0526.2013.12.016
Abstract:
The main characteristics of the general atmospheric circulation in September 2013 are as follows. The polar vortex stretches and splits with its main body located at Western Hemisphere and blocking emerging to the north of Caspian Sea. The Northwest Pacific subtropical high is stronger and more westward extended than normal. The monthly mean precipitation amount is 69.3 mm, which is 6.1% more than normal. There are a series of notable autumn rainfall processes over western China while moderate to severe drought appears in northern Henan with precipitation less than 20% of normal. The monthly mean temperature is 16.8℃, being 0.2℃ higher than normal. There are 2 large range heavy rainfall processes over China, and one of them is related with tropical cyclone. There are 8 tropical cyclones generated in the Northwest Pacific, among which Usagi (1319) is the strongest typhoon that lands at the east coast of Guangdong Province in the recent 40 years. 17 provinces (regions, cities) suffer from severe wind and hail disasters. Central and eastern China is hit by haze.
The main characteristics of the general atmospheric circulation in September 2013 are as follows. The polar vortex stretches and splits with its main body located at Western Hemisphere and blocking emerging to the north of Caspian Sea. The Northwest Pacific subtropical high is stronger and more westward extended than normal. The monthly mean precipitation amount is 69.3 mm, which is 6.1% more than normal. There are a series of notable autumn rainfall processes over western China while moderate to severe drought appears in northern Henan with precipitation less than 20% of normal. The monthly mean temperature is 16.8℃, being 0.2℃ higher than normal. There are 2 large range heavy rainfall processes over China, and one of them is related with tropical cyclone. There are 8 tropical cyclones generated in the Northwest Pacific, among which Usagi (1319) is the strongest typhoon that lands at the east coast of Guangdong Province in the recent 40 years. 17 provinces (regions, cities) suffer from severe wind and hail disasters. Central and eastern China is hit by haze.
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ISSN:1000-0526 CN:11-2282/P