ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 36,Issue 6,2010 Table of Contents
2010, 36(6):1-6.
DOI: 10.7519/j.issn.1000-0526.2010.6.001
Abstract:
Because the rainstorm precipitation amounts in the 2003 and 2006 Meiyu seasons are concentrated in the Huaihe Valley and their total precipitation amounts are different, the article has conducted the thorough research in the frontal zone structure by using the average field method. The results can be drawn as follows. (1) There was a clear Meiyu front area while heavy rain occurred, and the rainstorm precipitation amount and the frontal zone intensity are proportional. （2） Rainstorm area was located at the frontal zone, i.e. in the north of the hot and humid areas in the middlelower troposphere, and also north of the lowaltitude jet stream. (3) The shear deformation field of frontogenesis function overlapped with the rainstorm location, and the positive frontogenesis function area was shaped as an erect column and overlapped with the densified area of south wind isotachs. (4) Zonal distribution of the frontogenesis function instructed the rainstorm coverage.
Because the rainstorm precipitation amounts in the 2003 and 2006 Meiyu seasons are concentrated in the Huaihe Valley and their total precipitation amounts are different, the article has conducted the thorough research in the frontal zone structure by using the average field method. The results can be drawn as follows. (1) There was a clear Meiyu front area while heavy rain occurred, and the rainstorm precipitation amount and the frontal zone intensity are proportional. （2） Rainstorm area was located at the frontal zone, i.e. in the north of the hot and humid areas in the middlelower troposphere, and also north of the lowaltitude jet stream. (3) The shear deformation field of frontogenesis function overlapped with the rainstorm location, and the positive frontogenesis function area was shaped as an erect column and overlapped with the densified area of south wind isotachs. (4) Zonal distribution of the frontogenesis function instructed the rainstorm coverage.
2010, 36(6):7-12.
DOI: 10.7519/j.issn.1000-0526.2010.6.002
Abstract:
It is vital to forecast the areal precipitation of the dammed lakes’ upper basines and the upper reaches of the rivers in the situation with the water level rising, which threats to the safety of life and property after the occurrence of the Wenchuan Earthquake. In the paper, it is realized the boundary extractions of the upper basins of Nanba, Tangjiashan, Xiaojiaqiao and Laoyingyan dammed lakes and the upper reaches of Jialing River, Minjiang River, Fujiang River, Tuojiang River and Qingyi River by using the DEM model, river map and the locations of dammed lakes based on the GIS system. The areal precipitation is calculated with the forecasting precipitation data of the weather stations in disastrous areas by the Thiessen polygon method. It is established a method of areal precipitation forecasting technology under the condition of incomplete information of basin characteristics available as well as emergency states, and it provides the technical support for decision making service on hydrometeorology.
It is vital to forecast the areal precipitation of the dammed lakes’ upper basines and the upper reaches of the rivers in the situation with the water level rising, which threats to the safety of life and property after the occurrence of the Wenchuan Earthquake. In the paper, it is realized the boundary extractions of the upper basins of Nanba, Tangjiashan, Xiaojiaqiao and Laoyingyan dammed lakes and the upper reaches of Jialing River, Minjiang River, Fujiang River, Tuojiang River and Qingyi River by using the DEM model, river map and the locations of dammed lakes based on the GIS system. The areal precipitation is calculated with the forecasting precipitation data of the weather stations in disastrous areas by the Thiessen polygon method. It is established a method of areal precipitation forecasting technology under the condition of incomplete information of basin characteristics available as well as emergency states, and it provides the technical support for decision making service on hydrometeorology.
2010, 36(6):13-20.
DOI: 10.7519/j.issn.1000-0526.2010.6.003
Abstract:
By using all the available meteorological observation data, climatic characteristics of sustained fog between 1980 and 2006 in the Pearl River Estuary Region were analyzed. Meanwhile, the circulation characteristics and physical mechanism for sustained fog generation and dissipation were studied through analysing the typical cases. The major conclusions can be drawn as follows: (1) Sustained fog in the Pearl River Estuary Region usually appears from October to May next year, especially in spring; (2) The weather situation when sustained fog happens can be divided into 3 kinds: type A， on the e〖JP2〗ast of low pressure (or inverted trough)； type B， in the rear(or bottom) of high pressure； and type C， in uniform pressure fields; (3) When severe sustained fog happens, the transportation of wetwarm advection, the weak lift motion and convergence of vapor flux at the surface layer and the drywarm cap in the midlower troposphere are the favorable conditions for condensation of vapor and maintenance of temperature inversion, the intrusion of drycold advection accompanied by northerly wind is the main factor for the fog dissipation.
By using all the available meteorological observation data, climatic characteristics of sustained fog between 1980 and 2006 in the Pearl River Estuary Region were analyzed. Meanwhile, the circulation characteristics and physical mechanism for sustained fog generation and dissipation were studied through analysing the typical cases. The major conclusions can be drawn as follows: (1) Sustained fog in the Pearl River Estuary Region usually appears from October to May next year, especially in spring; (2) The weather situation when sustained fog happens can be divided into 3 kinds: type A， on the e〖JP2〗ast of low pressure (or inverted trough)； type B， in the rear(or bottom) of high pressure； and type C， in uniform pressure fields; (3) When severe sustained fog happens, the transportation of wetwarm advection, the weak lift motion and convergence of vapor flux at the surface layer and the drywarm cap in the midlower troposphere are the favorable conditions for condensation of vapor and maintenance of temperature inversion, the intrusion of drycold advection accompanied by northerly wind is the main factor for the fog dissipation.
2010, 36(6):21-28.
DOI: 10.7519/j.issn.1000-0526.2010.6.004
Abstract:
The characteristics of largescale circulation background and meteorological elements in fog events are studied, based on the continuous observations (wind, temperature, relative humidity and visibility) at automatic weather stations along the BeijingTianjinTanggu expressway from October to December in 2007 and the NCEP reanalysis data. It is found that the typical situation of local fog exists in the circulation of downdrafts in upper air and the weak pressure field on the ground; while the systematic fog exists in the region of thermal advection in the lower troposphere and weak pressure field in front of the cold front on the ground. The air temperatures are 9-13 ℃，4-7 ℃ and -6-1 ℃ in October, November and December respectively, during fog events. And humidity is mainly over 90% but partly between 85% and 90% for the visibility of 500-1000 m, with wind direction changefully and wind speed mainly less than 2 m?s-1. The huge differences of the formation and dissipation, duration and the sequence, occurring frequence for fogs at each section of the BeijingTianjinTanggu expressway are also obtained.
The characteristics of largescale circulation background and meteorological elements in fog events are studied, based on the continuous observations (wind, temperature, relative humidity and visibility) at automatic weather stations along the BeijingTianjinTanggu expressway from October to December in 2007 and the NCEP reanalysis data. It is found that the typical situation of local fog exists in the circulation of downdrafts in upper air and the weak pressure field on the ground; while the systematic fog exists in the region of thermal advection in the lower troposphere and weak pressure field in front of the cold front on the ground. The air temperatures are 9-13 ℃，4-7 ℃ and -6-1 ℃ in October, November and December respectively, during fog events. And humidity is mainly over 90% but partly between 85% and 90% for the visibility of 500-1000 m, with wind direction changefully and wind speed mainly less than 2 m?s-1. The huge differences of the formation and dissipation, duration and the sequence, occurring frequence for fogs at each section of the BeijingTianjinTanggu expressway are also obtained.
5 Characteristics Analysis of Severe Convective Weather
in Different Season of North Fujian Province
2010, 36(6):29-34.
DOI: 10.7519/j.issn.1000-0526.2010.6.005
Abstract:
Severe convective weather is one of the main disasters in north Fujian Province. We analyze distinct characteristics of severe convective weather in spring (March-April), flood season (May-June) and typhoon season (July-September), and then find out their climatological characteristics in different season.The results can help the forecast of severe convection weather and provide the basis of artificial hailprevention.
Severe convective weather is one of the main disasters in north Fujian Province. We analyze distinct characteristics of severe convective weather in spring (March-April), flood season (May-June) and typhoon season (July-September), and then find out their climatological characteristics in different season.The results can help the forecast of severe convection weather and provide the basis of artificial hailprevention.
2010, 36(6):35-42.
DOI: 10.7519/j.issn.1000-0526.2010.6.006
Abstract:
Based on the NCEP reanalysis, FY-2 satellite TBB and rainfall data from automatic precipitation stations etc., the two cold front shear processes which occurred in Yunnan on July 2 and 5, 2008 were analyzed. The results show that the cold front shear, range and rainfall between two processes are distinctly different, and that the intensity and movement of cold front sheer affect the intensity of rainfall. Meanwhile, the generation and maintaining of mesoscale system originated in sheer line significantly influence the intensity of rainfall. The YunnanBurma high ridge, plays an important role in vapor transport and convergence. The rainfall intensity differences result in the differences of strength of convection development during two convection processes, and thermal instablility indexes such as pseudoequivalent potential temperature, K index, total energy, CAPE, etc. Could reflect the differences of development of convection. Different conditions lead to different changes of physical fields, which is the main reason for intensity changes of precipitation occurring in cold front sheer system.
Based on the NCEP reanalysis, FY-2 satellite TBB and rainfall data from automatic precipitation stations etc., the two cold front shear processes which occurred in Yunnan on July 2 and 5, 2008 were analyzed. The results show that the cold front shear, range and rainfall between two processes are distinctly different, and that the intensity and movement of cold front sheer affect the intensity of rainfall. Meanwhile, the generation and maintaining of mesoscale system originated in sheer line significantly influence the intensity of rainfall. The YunnanBurma high ridge, plays an important role in vapor transport and convergence. The rainfall intensity differences result in the differences of strength of convection development during two convection processes, and thermal instablility indexes such as pseudoequivalent potential temperature, K index, total energy, CAPE, etc. Could reflect the differences of development of convection. Different conditions lead to different changes of physical fields, which is the main reason for intensity changes of precipitation occurring in cold front sheer system.
2010, 36(6):43-49.
DOI: 10.7519/j.issn.1000-0526.2010.6.007
Abstract:
By using the weather chart, surface densified observation of precipitation, sounding data and NCEP/NCAR reanalysis data (resolution 1°×1°), the largescale persistent severe precipitation in southern North China from 9 to 10 May 2009 is analyzed. Results demonstrate that the severe precipitation is produced when the cold air met with southwest warm wet air. There is southwest current ahead of the trough at 500 hPa. and the northeastsouthwest shear line at the 850 and 700 hPa. The surface cold front turns to stationary front. Then the weak cyclonic wave is formed and moved to southeast and finally disappears. The atmosphere has high temperature and humidity. There are weak convective instability and symmetric instability in middle levels. The invasion of cold air takes place in the lower levels. The cold air meets with warm wet air to form the convergence and updraft on the one hand, and on the other hand, the cold air makes the warm wet air ascended. As a result, the ascending movement has been strengthened and the precipitation is increase. The middlehigh level atmosphere is warm and wet. The level of 0 ℃ is relatively high. The weather mainly is severe precipitation accompanied with thunder and lightning. Owing to the severe warm and wet currents, the cold air weakens during moving to southward and the velocity slows down. The cold air and warm air confront each other for a long time in the lower reaches of the Huanghe River, therefore, the severe precipitation is maintained persistently.
By using the weather chart, surface densified observation of precipitation, sounding data and NCEP/NCAR reanalysis data (resolution 1°×1°), the largescale persistent severe precipitation in southern North China from 9 to 10 May 2009 is analyzed. Results demonstrate that the severe precipitation is produced when the cold air met with southwest warm wet air. There is southwest current ahead of the trough at 500 hPa. and the northeastsouthwest shear line at the 850 and 700 hPa. The surface cold front turns to stationary front. Then the weak cyclonic wave is formed and moved to southeast and finally disappears. The atmosphere has high temperature and humidity. There are weak convective instability and symmetric instability in middle levels. The invasion of cold air takes place in the lower levels. The cold air meets with warm wet air to form the convergence and updraft on the one hand, and on the other hand, the cold air makes the warm wet air ascended. As a result, the ascending movement has been strengthened and the precipitation is increase. The middlehigh level atmosphere is warm and wet. The level of 0 ℃ is relatively high. The weather mainly is severe precipitation accompanied with thunder and lightning. Owing to the severe warm and wet currents, the cold air weakens during moving to southward and the velocity slows down. The cold air and warm air confront each other for a long time in the lower reaches of the Huanghe River, therefore, the severe precipitation is maintained persistently.
2010, 36(6):50-58.
DOI: 10.7519/j.issn.1000-0526.2010.6.008
Abstract:
Based on the conventional data, automatic weather station data, Doppler radar observational data, and FY2C TBB data, together with the conceptual model of the mesoscale convective complex motion，the strongest thunderstorm and rainstorm event in North China area on 18 July 2007 has been analyzed. The results show that the local rainstorm is presented the obvious character of a mesoscale convective system which is produced under the largescale advantageous condition. The strong rainfall occurred at the head of the Lamdbashaped echo， and the falling area of rainstorm is associated with the meso cyclone. The analyses of automatic weather station data illustrate that the rainfall region and moving direction can be found. In addition, the rainstorm occurred at the rightbackside of the MCC and the precipitation intensity is the strongest when the cloud top temperature is the lowest. According to the motion of the mesoβ scale element (MBE)， it can forecast the next region of the rainstorm which provides a new way for the nowcasting of the local rainstorm.
Based on the conventional data, automatic weather station data, Doppler radar observational data, and FY2C TBB data, together with the conceptual model of the mesoscale convective complex motion，the strongest thunderstorm and rainstorm event in North China area on 18 July 2007 has been analyzed. The results show that the local rainstorm is presented the obvious character of a mesoscale convective system which is produced under the largescale advantageous condition. The strong rainfall occurred at the head of the Lamdbashaped echo， and the falling area of rainstorm is associated with the meso cyclone. The analyses of automatic weather station data illustrate that the rainfall region and moving direction can be found. In addition, the rainstorm occurred at the rightbackside of the MCC and the precipitation intensity is the strongest when the cloud top temperature is the lowest. According to the motion of the mesoβ scale element (MBE)， it can forecast the next region of the rainstorm which provides a new way for the nowcasting of the local rainstorm.
2010, 36(6):59-65.
DOI: 10.7519/j.issn.1000-0526.2010.6.009
Abstract:
A typical squall line taking place in Beijing area is analyzed with the Sband Doppler weather radar data and intensive surface AWS observations in Beijing. The results indicate that: (1) meteorological elements show abrupt changes during the influence of the squall line, such as mutation in the wind direction, surge in wind speed, drop of temperature and steep rising of pressure; (2) there is a good relationship among surface vorticity, precipitation and thunderstorm winds. The position of precipitation and the variation of the distance between precipitation and positive vorticity can be used to indicate the future trend of convective cells; (3) surface water vapor flux shows some small scale characteristics, such as suface outflow of thunderstorm, terrain convergence and lowlevel water vapor transport.The combination of positive water vapor flux from thunderstorm’s outflow and terrain convergence has strengthened the convergence and lift in the front of the mountain, this is the main reason for the quickly development of thunderstorm in the front of mountain and subsequently local heavy rain and thunderstorm winds. The surface water vapor flux can be used as an indicator of the future trend for the thunderstorms.
A typical squall line taking place in Beijing area is analyzed with the Sband Doppler weather radar data and intensive surface AWS observations in Beijing. The results indicate that: (1) meteorological elements show abrupt changes during the influence of the squall line, such as mutation in the wind direction, surge in wind speed, drop of temperature and steep rising of pressure; (2) there is a good relationship among surface vorticity, precipitation and thunderstorm winds. The position of precipitation and the variation of the distance between precipitation and positive vorticity can be used to indicate the future trend of convective cells; (3) surface water vapor flux shows some small scale characteristics, such as suface outflow of thunderstorm, terrain convergence and lowlevel water vapor transport.The combination of positive water vapor flux from thunderstorm’s outflow and terrain convergence has strengthened the convergence and lift in the front of the mountain, this is the main reason for the quickly development of thunderstorm in the front of mountain and subsequently local heavy rain and thunderstorm winds. The surface water vapor flux can be used as an indicator of the future trend for the thunderstorms.
2010, 36(6):66-72.
DOI: 10.7519/j.issn.1000-0526.2010.6.010
Abstract:
Based on the 711digital weather radar data of 71 linear MCS cases in Weibei area of Shaanxi Province between May and September from 2000 to 2006, these linear MCS systems were classified into four categories (trailing stratiform (TS), leading stratiform (LS), parallel stratiform (PS) and broken linear MCS). Ｔhe characteristics of each MCS class were statistically analyzed. The results show that linear MCS has the greater frequency of changes, and the broken linear MCS occurs in the most cases; the mean scale of TS MCS is the greatest and that of PS MCS is the least; the dominant moving direction of linear MCS is southeast; the moving speed of linear MCS in different direction has large differences and the mean moving speed of TS MCS which moves southeastward is the fastest. On the other hand, the TS MCS has the most hail probability (62%), and tends to have more severe weather reports, areal hail, heavy disasters than other kinds of MCS.
Based on the 711digital weather radar data of 71 linear MCS cases in Weibei area of Shaanxi Province between May and September from 2000 to 2006, these linear MCS systems were classified into four categories (trailing stratiform (TS), leading stratiform (LS), parallel stratiform (PS) and broken linear MCS). Ｔhe characteristics of each MCS class were statistically analyzed. The results show that linear MCS has the greater frequency of changes, and the broken linear MCS occurs in the most cases; the mean scale of TS MCS is the greatest and that of PS MCS is the least; the dominant moving direction of linear MCS is southeast; the moving speed of linear MCS in different direction has large differences and the mean moving speed of TS MCS which moves southeastward is the fastest. On the other hand, the TS MCS has the most hail probability (62%), and tends to have more severe weather reports, areal hail, heavy disasters than other kinds of MCS.
2010, 36(6):73-78.
DOI: 10.7519/j.issn.1000-0526.2010.6.011
Abstract:
This paper analyzes the characteristics of cloud-to-ground (CG) lightning in rainstorm and hail event that caused by a cold vortex, by using data collected in lightning detection network, Doppler radar and intensive automatic weather stations. The results show that there are dense areas of CG lightning in the process of rainstorm and hail, and the proportion of positive CG lightning in hail is higher than in rainstorm; the negative CG lightning predominates in rainstorm, which is mostly located at the core area of rainstorm and mainly in the radar echo area of above 45 dBz, and its lasting time is equivalent to the duration of rainstorm. The negative CG lightning frequency and its growth rate reach the peak 30-70 min ahead of the area of strong radar echo, and it has a certain prediction significance for shortterm rainstorm forecasting and early warning. In the hail process, negative CG lightning is concentrated in front of hail cloud, and the positive CG lightning is located at the core area of hail cloud, which is consistent with hail area, and the regions of positive and negative CG lightning begin to separate. The total number of CG lightning and the area of strong radar echo have a similar changing trend. Positive CG lightning occurs about 30 min ahead of hail. The total CG lightning and positive CG lightning frequencies are increasing considerably before hail. Hail occurs during the period that the total CG lightning, positive CG lightning and the area of strong radar echo reach the peak and decrease rapidly. The total CG lightning number decreases, but the positive CG lightning increases in the dissipating and weakening phase of hail cloud.
This paper analyzes the characteristics of cloud-to-ground (CG) lightning in rainstorm and hail event that caused by a cold vortex, by using data collected in lightning detection network, Doppler radar and intensive automatic weather stations. The results show that there are dense areas of CG lightning in the process of rainstorm and hail, and the proportion of positive CG lightning in hail is higher than in rainstorm; the negative CG lightning predominates in rainstorm, which is mostly located at the core area of rainstorm and mainly in the radar echo area of above 45 dBz, and its lasting time is equivalent to the duration of rainstorm. The negative CG lightning frequency and its growth rate reach the peak 30-70 min ahead of the area of strong radar echo, and it has a certain prediction significance for shortterm rainstorm forecasting and early warning. In the hail process, negative CG lightning is concentrated in front of hail cloud, and the positive CG lightning is located at the core area of hail cloud, which is consistent with hail area, and the regions of positive and negative CG lightning begin to separate. The total number of CG lightning and the area of strong radar echo have a similar changing trend. Positive CG lightning occurs about 30 min ahead of hail. The total CG lightning and positive CG lightning frequencies are increasing considerably before hail. Hail occurs during the period that the total CG lightning, positive CG lightning and the area of strong radar echo reach the peak and decrease rapidly. The total CG lightning number decreases, but the positive CG lightning increases in the dissipating and weakening phase of hail cloud.
2010, 36(6):79-84.
DOI: 10.7519/j.issn.1000-0526.2010.6.012
Abstract:
The cloud and precipitation mechanism could be studied by investigating the characteristics of precipitation particle.Characteristic analysis of particle concentration, falling velocity as well as their spectrum distribution in different precipitation patterns was made according to 2540 sharing data during 26-28 January 2008 observed by OTT Parsivel laser precipitation particle measuring system installed at the top unobstructed platform of the building of Anhui Qianshan Meterological Station near Dabie Mountains. The results have shown: (1) During the snowstorm, the average number concentration is the largest in the case of sleet, up to 589 per min, and the least is in rain, only 255 per min. (2) The concentrations of snow and freezing rain exhibit a form of double peak, other forms of precipitation are in single peak. (3) Different precipitation particle sizes mainly lay between 0.125-1.00 mm, with the widest spectrum being snow, and the narrowest being drizzle. The mean spectrum of each form of precipitation has a single peak with different peak values. (4) The maximum falling velocity of each form of precipitation is primarily concentrated within 1.0-4.8 m?s-1, 98.68% in drizzle, 98.46% in drizzle with rain, 97.72% in rain, 94.79% in sleet, 93.69% in freezing rain, while 85.83% in snow. (5) The widest mean velocity spectra are in rain and sleet, and the maximum velocity could be up to 9.6 m?s-1. The narrowest velocity spectrum is in drizzle, with its maximum being 5.6 m?s-1. Other velocity spectra appear generally similar. The mean velocity spectrum of each form of precipitaion has a single peak, but their peak positions are different each other.These results provide reference for the investigation on mechanism of icy rain and snow weather, and also provide theoretic basis for weather modification.
The cloud and precipitation mechanism could be studied by investigating the characteristics of precipitation particle.Characteristic analysis of particle concentration, falling velocity as well as their spectrum distribution in different precipitation patterns was made according to 2540 sharing data during 26-28 January 2008 observed by OTT Parsivel laser precipitation particle measuring system installed at the top unobstructed platform of the building of Anhui Qianshan Meterological Station near Dabie Mountains. The results have shown: (1) During the snowstorm, the average number concentration is the largest in the case of sleet, up to 589 per min, and the least is in rain, only 255 per min. (2) The concentrations of snow and freezing rain exhibit a form of double peak, other forms of precipitation are in single peak. (3) Different precipitation particle sizes mainly lay between 0.125-1.00 mm, with the widest spectrum being snow, and the narrowest being drizzle. The mean spectrum of each form of precipitation has a single peak with different peak values. (4) The maximum falling velocity of each form of precipitation is primarily concentrated within 1.0-4.8 m?s-1, 98.68% in drizzle, 98.46% in drizzle with rain, 97.72% in rain, 94.79% in sleet, 93.69% in freezing rain, while 85.83% in snow. (5) The widest mean velocity spectra are in rain and sleet, and the maximum velocity could be up to 9.6 m?s-1. The narrowest velocity spectrum is in drizzle, with its maximum being 5.6 m?s-1. Other velocity spectra appear generally similar. The mean velocity spectrum of each form of precipitaion has a single peak, but their peak positions are different each other.These results provide reference for the investigation on mechanism of icy rain and snow weather, and also provide theoretic basis for weather modification.
2010, 36(6):85-89.
DOI: 10.7519/j.issn.1000-0526.2010.6.013
Abstract:
On the basis of physiological characteristics of early rice and the research results of predecessors, the suitability models about temperature, precipitation and sunshine of early rice are constructed. In order to express synergetic effect of meteorological factors and yield, climatic suitability model of early rice is established. According to different periods of climate suitability of early rice, the climatic suitability index of early rice is constructed by using weighted method. Based on the relation between climatic suitability index and early rice yield, a climatic suitability indicator is set up. And dynamical prediction models of early rice are created by using climatic suitability index at different stages and early rice yield. The results indicate that the method has high prediction accuracy of the bumper or poor harvest trend and the actual yield on both model test and forecasting test and can satisfy the needs of operational services.
On the basis of physiological characteristics of early rice and the research results of predecessors, the suitability models about temperature, precipitation and sunshine of early rice are constructed. In order to express synergetic effect of meteorological factors and yield, climatic suitability model of early rice is established. According to different periods of climate suitability of early rice, the climatic suitability index of early rice is constructed by using weighted method. Based on the relation between climatic suitability index and early rice yield, a climatic suitability indicator is set up. And dynamical prediction models of early rice are created by using climatic suitability index at different stages and early rice yield. The results indicate that the method has high prediction accuracy of the bumper or poor harvest trend and the actual yield on both model test and forecasting test and can satisfy the needs of operational services.
2010, 36(6):90-94.
DOI: 10.7519/j.issn.1000-0526.2010.6.014
Abstract:
The feature of surface layer wind velocity profile and the roughness length determined by the roughness units over nonhomogeneous landform are analyzed by using fivelevel effective wind velocities measured by the 35 m tower measuring system in a neutral stratification atmosphere. The result indicated that: (1) The surface layer wind profile is in logarithmic distribution, with correlation coefficients greater than 0.985, and standard deviations about 0.04. (2) The roughness length is 1.25 m, but it will vary between 0.038-4.903 m when the condition of external fluid changes, which has a negative correlation with wind velocity perfectly, with a correlation coefficient -0.953.
The feature of surface layer wind velocity profile and the roughness length determined by the roughness units over nonhomogeneous landform are analyzed by using fivelevel effective wind velocities measured by the 35 m tower measuring system in a neutral stratification atmosphere. The result indicated that: (1) The surface layer wind profile is in logarithmic distribution, with correlation coefficients greater than 0.985, and standard deviations about 0.04. (2) The roughness length is 1.25 m, but it will vary between 0.038-4.903 m when the condition of external fluid changes, which has a negative correlation with wind velocity perfectly, with a correlation coefficient -0.953.
2010, 36(6):95-100.
DOI: 10.7519/j.issn.1000-0526.2010.6.015
Abstract:
Based on the observed thunderstorm data of Zhengzhou, the climatic characteristics of lightning are analyzed. And based on the sounding data from 2004 to 2006， the environment parameters such as Sweat index， the best lifting index， the 850 hPa pseudoequivalent potential temperature and so on are calculated. The correlations between the single environment parameter and lightning weather in Zhengzhou， as well as correlations between compound parameters and lightning weather have been studied respectively. The result shows that: (1) the single environment parameter has good relationship to the lightning activity when taking value in some extent， but can not reflect the lightning characteristics totally. (2) Multiparameters can reflect the characteristics of lightning activity to some extent. The equation of lightning probability potential forecast is constructed by using multidimensional linear regression， and the significance test of α=0.05 is passed. Using the lightning observed data， the operational results from June to August in 2008 are assessed，and the TS score of the probability forecast reaches 63.6%. The method provides the objective and quantitative reference to the forecast of lightning in Zhengzhou.
Based on the observed thunderstorm data of Zhengzhou, the climatic characteristics of lightning are analyzed. And based on the sounding data from 2004 to 2006， the environment parameters such as Sweat index， the best lifting index， the 850 hPa pseudoequivalent potential temperature and so on are calculated. The correlations between the single environment parameter and lightning weather in Zhengzhou， as well as correlations between compound parameters and lightning weather have been studied respectively. The result shows that: (1) the single environment parameter has good relationship to the lightning activity when taking value in some extent， but can not reflect the lightning characteristics totally. (2) Multiparameters can reflect the characteristics of lightning activity to some extent. The equation of lightning probability potential forecast is constructed by using multidimensional linear regression， and the significance test of α=0.05 is passed. Using the lightning observed data， the operational results from June to August in 2008 are assessed，and the TS score of the probability forecast reaches 63.6%. The method provides the objective and quantitative reference to the forecast of lightning in Zhengzhou.
2010, 36(6):101-104.
DOI: 10.7519/j.issn.1000-0526.2010.6.016
Abstract:
The correlations between synchronized air temperature (Ta) and soil temperature (Ts) at automatic weather stations and the land surface temperature (TLS) retrieved from MODIS are analyzed. The results show that for inhomogeneous land surface the correlation coefficients between TLS) and Ta and Ts are unstable, and the correlation coefficients at different satellite passing through time have a great difference. But there is a stable linear correlation between (Ts-TLS)) and (Ts-Ta), and the correlation coefficients at different satellite passing through time are greater than 0.8. A regression equation of soil temperature depending on TLS) and Tais obtained and its standard error is 4.85 ℃.
The correlations between synchronized air temperature (Ta) and soil temperature (Ts) at automatic weather stations and the land surface temperature (TLS) retrieved from MODIS are analyzed. The results show that for inhomogeneous land surface the correlation coefficients between TLS) and Ta and Ts are unstable, and the correlation coefficients at different satellite passing through time have a great difference. But there is a stable linear correlation between (Ts-TLS)) and (Ts-Ta), and the correlation coefficients at different satellite passing through time are greater than 0.8. A regression equation of soil temperature depending on TLS) and Tais obtained and its standard error is 4.85 ℃.
2010, 36(6):105-111.
DOI: 10.7519/j.issn.1000-0526.2010.6.017
Abstract:
Based on the surface topographic altitude data, FY-2C infrared channel data and cloud cover data from observation stations during 30 April-01 May 2007 from 2000 to 0300 (UTC), an analysis of the relation between the topographic altitude and the clear IR radiance is performed. It is found that the IR brightness temperature of surface is influenced by the change of surface topographic altitudes at nighttime in clear areas. The IR brightness temperature in some clear areas at high altitude is lower than (or equal to) that in other cloudy areas at low altitude. This results in difficulty to process cloud detection using infrared channel data. Therefore, the standard database of clear surface IR brightness temperature at different topographic altitudes is established and used to separate satellite infrared observations into “clear” and “cloudy” categories as a method at nighttime. A case selected randomly shows that 88 percent of satellite observations can be correctly separated for an infrared imagery at nighttime. There are 4 percent of “clear” observations to be incorrectly separated into “cloudy” ones. In addition, 8 percent of “cloudy” observations are incorrectly separated into “clear” category. By the method 92 percent of satellite observations in clear areas can be correctly categorized, but 82 percent in cloudy areas. In order to analyze the operational use of the method the satellite infrared observations at 0000 UTC during 2-5 May 2007 are separated into “clear” and “cloudy” categories based on the standard database from the datasets at 0000 UTC 1 May 2007. The 92 percent of total satellite observations can be correctly separated, and the accuracy is close to, but better than that of cloud detection at 0000 UTC 1 May. The 93 percent of satellite observations in clear areas can be correctly categorized, which results in the better total accuracy, also 92 percent in cloudy areas.
Based on the surface topographic altitude data, FY-2C infrared channel data and cloud cover data from observation stations during 30 April-01 May 2007 from 2000 to 0300 (UTC), an analysis of the relation between the topographic altitude and the clear IR radiance is performed. It is found that the IR brightness temperature of surface is influenced by the change of surface topographic altitudes at nighttime in clear areas. The IR brightness temperature in some clear areas at high altitude is lower than (or equal to) that in other cloudy areas at low altitude. This results in difficulty to process cloud detection using infrared channel data. Therefore, the standard database of clear surface IR brightness temperature at different topographic altitudes is established and used to separate satellite infrared observations into “clear” and “cloudy” categories as a method at nighttime. A case selected randomly shows that 88 percent of satellite observations can be correctly separated for an infrared imagery at nighttime. There are 4 percent of “clear” observations to be incorrectly separated into “cloudy” ones. In addition, 8 percent of “cloudy” observations are incorrectly separated into “clear” category. By the method 92 percent of satellite observations in clear areas can be correctly categorized, but 82 percent in cloudy areas. In order to analyze the operational use of the method the satellite infrared observations at 0000 UTC during 2-5 May 2007 are separated into “clear” and “cloudy” categories based on the standard database from the datasets at 0000 UTC 1 May 2007. The 92 percent of total satellite observations can be correctly separated, and the accuracy is close to, but better than that of cloud detection at 0000 UTC 1 May. The 93 percent of satellite observations in clear areas can be correctly categorized, which results in the better total accuracy, also 92 percent in cloudy areas.
2010, 36(6):112-116.
DOI: 10.7519/j.issn.1000-0526.2010.6.018
Abstract:
This paper describes the principles and methods of monitoring the ionospheric scintillation based on the FY-2 Satellite operational telemetry signals and how the monitor works. The monitor watches realtime satellite signals for scintillation in both amplitude and phase. The telemetry signal from the satellite is one of phase modulation at 1.7 GHz, which is stable in the emission amplitudes and accessible and accurate in the signals loaded. It can be used in the research on ionospheric scintillation in and around China. As the FY-2 Ｓatellite is geostationary and monitors without changes inherent with the motion of the satellite, it is easy to separate the temporal changes from the spatial ones, making it more advantageous than the monitoring with GPS. Designed on the basis of the receivers for broadened cloud imagery that are widely installed across China and with the use of their antenna and channels and high and first intermediate frequencies, the monitoring instrument in question will be readily accepted nationwide and joined in network monitoring. In addition, it will be much more useful due to the availability of signal sources emitting the same frequency in two different directions from the existing networked twin satellites. When combined with the GPSbased dualfrequency scintillation monitors, this monitoring device will also be able to have access to the spectral characteristics of the ionospheric scintillation.
This paper describes the principles and methods of monitoring the ionospheric scintillation based on the FY-2 Satellite operational telemetry signals and how the monitor works. The monitor watches realtime satellite signals for scintillation in both amplitude and phase. The telemetry signal from the satellite is one of phase modulation at 1.7 GHz, which is stable in the emission amplitudes and accessible and accurate in the signals loaded. It can be used in the research on ionospheric scintillation in and around China. As the FY-2 Ｓatellite is geostationary and monitors without changes inherent with the motion of the satellite, it is easy to separate the temporal changes from the spatial ones, making it more advantageous than the monitoring with GPS. Designed on the basis of the receivers for broadened cloud imagery that are widely installed across China and with the use of their antenna and channels and high and first intermediate frequencies, the monitoring instrument in question will be readily accepted nationwide and joined in network monitoring. In addition, it will be much more useful due to the availability of signal sources emitting the same frequency in two different directions from the existing networked twin satellites. When combined with the GPSbased dualfrequency scintillation monitors, this monitoring device will also be able to have access to the spectral characteristics of the ionospheric scintillation.
2010, 36(6):117-121.
DOI: 10.7519/j.issn.1000-0526.2010.6.019
Abstract:
The data of Doppler weather radar are often contaminated by ground clutter. It has a significant effect on the accuracy of the base data estimates (reflectivity, velocity and spectrum width), then it will also affect all ensuing products. Therefore, filtering techniques that attempt to suppress these ground clutter signals are essential for high data quality in all Doppler weather radar systems. Firstly, this dissertation outlines the research background and significance of adaptive Gaussian frequency filter. Secondly, analyzes the characteristics of the ground clutter and weather signals in the Doppler weather radars. Thirdly, describes the theory of the fifthorder elliptic infinite impulse response (IIR) ground clutter filter and the algorithm of adaptive Gaussian frequency filter. In the end, using the data of actual radar echo signals, analyzes the ground clutter suppression performance of the fifthorder elliptic infinite impulse response (IIR) ground clutter filter and adaptive Gaussian frequency filter. Then, analyzes and compares the ground clutter suppression performance of these two methods, gets following results: the ground clutter suppression performance of the adaptive Gaussian frequency filter without clutter filter bypass charts is better than that of the fifthorder elliptic IIR filter with clutter filter bypass charts, and adaptive Gaussian frequency filter satisfies the request of realtime processing.
The data of Doppler weather radar are often contaminated by ground clutter. It has a significant effect on the accuracy of the base data estimates (reflectivity, velocity and spectrum width), then it will also affect all ensuing products. Therefore, filtering techniques that attempt to suppress these ground clutter signals are essential for high data quality in all Doppler weather radar systems. Firstly, this dissertation outlines the research background and significance of adaptive Gaussian frequency filter. Secondly, analyzes the characteristics of the ground clutter and weather signals in the Doppler weather radars. Thirdly, describes the theory of the fifthorder elliptic infinite impulse response (IIR) ground clutter filter and the algorithm of adaptive Gaussian frequency filter. In the end, using the data of actual radar echo signals, analyzes the ground clutter suppression performance of the fifthorder elliptic infinite impulse response (IIR) ground clutter filter and adaptive Gaussian frequency filter. Then, analyzes and compares the ground clutter suppression performance of these two methods, gets following results: the ground clutter suppression performance of the adaptive Gaussian frequency filter without clutter filter bypass charts is better than that of the fifthorder elliptic IIR filter with clutter filter bypass charts, and adaptive Gaussian frequency filter satisfies the request of realtime processing.
2010, 36(6):122-127.
DOI: 10.7519/j.issn.1000-0526.2010.6.020
Abstract:
Based on the data obtained from weather forecaster’s needs and application tracking survey with questionnaire and face to face depthinterview since 2006 to 2008, the benefits of advanced forecast techniques and improved new products, such as B08FDP products provided during Beijing 2008 Olympics period, were assessed. The three main obstacles preventing weather forecasters from truly using B08FDP products, were drawn from weather forecaster’s needs survey and fed back to weather service authority timely in 2006. Weather forecaster’s needs and application of new advanced forecast techniques were contrastively analyzed, results showed that forecasters had a more noticeably enhanced confidence in and increased satisfaction to the new advanced forecast techniques and improved products during 2008 Olympics than that in 2007. It was found that the improved socioeconomic benefits of the improvement of forecast techniques were affected by the forecaster’s skillful and optimal application of advanced forecast techniques. Therefore, it was crucially important to strengthen the training of forecasters, allowing them to be the master of new forecast techniques, and to build up their confidence in and capability of using the techniques in a conscious manner. At last, some suggestions and recommendations were given for improving the using of advanced weather forecast techniques by weather forecasters.
Based on the data obtained from weather forecaster’s needs and application tracking survey with questionnaire and face to face depthinterview since 2006 to 2008, the benefits of advanced forecast techniques and improved new products, such as B08FDP products provided during Beijing 2008 Olympics period, were assessed. The three main obstacles preventing weather forecasters from truly using B08FDP products, were drawn from weather forecaster’s needs survey and fed back to weather service authority timely in 2006. Weather forecaster’s needs and application of new advanced forecast techniques were contrastively analyzed, results showed that forecasters had a more noticeably enhanced confidence in and increased satisfaction to the new advanced forecast techniques and improved products during 2008 Olympics than that in 2007. It was found that the improved socioeconomic benefits of the improvement of forecast techniques were affected by the forecaster’s skillful and optimal application of advanced forecast techniques. Therefore, it was crucially important to strengthen the training of forecasters, allowing them to be the master of new forecast techniques, and to build up their confidence in and capability of using the techniques in a conscious manner. At last, some suggestions and recommendations were given for improving the using of advanced weather forecast techniques by weather forecasters.
2010, 36(6):128-133.
DOI: 10.7519/j.issn.1000-0526.2010.6.021
Abstract:
The following are the main characteristics of the general circulation of atmosphere in March 2010. There were three polar vortex centers in the Northern Hemisphere. The circulation presents a threewave pattern in middlehigh latitudes. The intensity of three main deep troughs is weaker than that of the trough in average conditions. The south branch trough is easterly and weaker than the normal years. The subtropical high shows an eastwest belt figure and stronger than the corresponding time of normal years. The western ridge spot of high extends to the Indian Ocean. The average temperature (3.4 ℃) is equal to the corresponding time of normal years and the average precipitation (32.3 mm) is more than 4.2 mm compared with the corresponding time of normal years during March 2010. There were three cold air processes and seven sand and dust processes in the month.
The following are the main characteristics of the general circulation of atmosphere in March 2010. There were three polar vortex centers in the Northern Hemisphere. The circulation presents a threewave pattern in middlehigh latitudes. The intensity of three main deep troughs is weaker than that of the trough in average conditions. The south branch trough is easterly and weaker than the normal years. The subtropical high shows an eastwest belt figure and stronger than the corresponding time of normal years. The western ridge spot of high extends to the Indian Ocean. The average temperature (3.4 ℃) is equal to the corresponding time of normal years and the average precipitation (32.3 mm) is more than 4.2 mm compared with the corresponding time of normal years during March 2010. There were three cold air processes and seven sand and dust processes in the month.
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