ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 40,Issue 1,2014 Table of Contents
2014, 40(1):1-6.
DOI: 10.7519/j.issn.1000-0526.2014.01.001
Abstract:
This paper discusses the influence of synoptic dynamics (macro process) and cloud physics (micro process) on cloudy configuration changes and evolution of weather phenomenon in deeply wet convection, and their roles in precipitation evolution. The mechanism of thunderstorm’s motion and development is expressed in the light of synoptic dynamics, and precipitation estimation of different characteristic cloud is compared.
This paper discusses the influence of synoptic dynamics (macro process) and cloud physics (micro process) on cloudy configuration changes and evolution of weather phenomenon in deeply wet convection, and their roles in precipitation evolution. The mechanism of thunderstorm’s motion and development is expressed in the light of synoptic dynamics, and precipitation estimation of different characteristic cloud is compared.
2014, 40(1):7-17.
DOI: 10.7519/j.issn.1000-0526.2014.01.002
Abstract:
A brief review of geostationary satellite based convective initiation (CI) including the cloud clusters (CC) identification, the CC tracking technique, the multi spectral cloud top properties of CI, the determination of likelihood for CI and some conclusions are presented. Studies indicate that CI may predict the rain storms more early than ground based radar by choosing carefully the sensitive channels, bands combinations and temporal trends, showing its application potentials for nowcasting forecasts. The knowing CI algorithms basically involve three parts: target identification, tracking technique and CI likelihood detection. The operational algorithms are similar approaches but something different. For example, the Rapidly Developing Thunderstorms algorithm (RDT) considers the vertical cross section of cloud systems while the tracking algorithm is mainly built on the overlapping between cells according to their move and speed. The Forecasting and Tracking the Evolution of Cloud Clusters (ForTraCC) technique concerns active convective systems, presenting the tracking situation including merges and splitting and displaing the ability to forecast the MCS trajectory. The GOES R CI algorithm aims for the next generation satellite’s sounding and observing, using a series of spectral and temporal thresholds to identify CI. While the University of Wisconsin Convective Initiation (UWCI) algorithm utilizes a box averaged approach to monitor cloud top cooling rates of CI. This approach is computationally inexpensive and easily provide to engineering. With some new payloads ongoing launch and more powerful detection abilities, more and more satellite data will be introduced to identify convective cells. Also， computer technique progress will help to solve the complicated problems which may appear in the process of convective tracking, these efforts will improve the accuracy of CI products.
A brief review of geostationary satellite based convective initiation (CI) including the cloud clusters (CC) identification, the CC tracking technique, the multi spectral cloud top properties of CI, the determination of likelihood for CI and some conclusions are presented. Studies indicate that CI may predict the rain storms more early than ground based radar by choosing carefully the sensitive channels, bands combinations and temporal trends, showing its application potentials for nowcasting forecasts. The knowing CI algorithms basically involve three parts: target identification, tracking technique and CI likelihood detection. The operational algorithms are similar approaches but something different. For example, the Rapidly Developing Thunderstorms algorithm (RDT) considers the vertical cross section of cloud systems while the tracking algorithm is mainly built on the overlapping between cells according to their move and speed. The Forecasting and Tracking the Evolution of Cloud Clusters (ForTraCC) technique concerns active convective systems, presenting the tracking situation including merges and splitting and displaing the ability to forecast the MCS trajectory. The GOES R CI algorithm aims for the next generation satellite’s sounding and observing, using a series of spectral and temporal thresholds to identify CI. While the University of Wisconsin Convective Initiation (UWCI) algorithm utilizes a box averaged approach to monitor cloud top cooling rates of CI. This approach is computationally inexpensive and easily provide to engineering. With some new payloads ongoing launch and more powerful detection abilities, more and more satellite data will be introduced to identify convective cells. Also， computer technique progress will help to solve the complicated problems which may appear in the process of convective tracking, these efforts will improve the accuracy of CI products.
2014, 40(1):18-27.
DOI: 10.7519/j.issn.1000-0526.2014.01.003
Abstract:
According to diagnostic precipitation methods of calculating precipitable water, pseudo convection precipitable water, flux and flux divergence of moisture, cloud liquid water and cloud ice crystal, moisture weighted mean wind and condensation function precipitation rate, the continuous torrential rain that occurred over South China in June 2010 was diagnosed for its large scale moisture situation. Meanwhile, under the synoptic system of “upper trough-southwest vortex (SW vortex)-shear line-low level jet”, the extremely severe rainfall seen in Jiangxi, Fujian and Hunan in 19-20 June 2010 was simulated by a three nested, WRF model. The simulation and diagnostic analysis show that the large scale moisture field of the heavy rains in South China is characterized by “positive anomalous in the middle high latitudes-negative anomalous in the middle low latitudes-the subtropical ridge being positive anomaly towards west-anomalous activities of the monsoon trough” in East Asia, which causes the large scale vapor over the Bay of Bengal and the South China Sea to move into the Mainland of China. Many mesoscale rainstorms develop in high value areas of saturated water vapor, cloud water and cloud ice, where wind convergence and ascent motions take place and there are warm humid jet streams in its upstream. Both precipitation rates of condensation function and flux divergence of total water are products of the wind divergence initiating vertical motions, and the precipitation rate of condensation function gradually approaches approximation reasonable for explicit precipitation physical process in model atmosphere along with the improvement of spatial and temporal resolutions. When the model resolution reaches 4 km, rainfalls with the condensation function precipitation rate being 1-3 mm·min-1 can be simulated in the system of “SW vortex-shear line”, and the precipitation rate of collection growth of liquid and/or ice droplets in super saturated clouds can be described by their flux divergences and should be added to the precipitation rate of condensation function. Therefore, synoptic dynamic factors for the mesoscale rainfalls to occcur and develop in the model atmosphere is only the wind divergence field in weather system, for the vertical motions are determined by the divergence field with high spatial and temporal resolution in model atmosphere, so are all of the precipitation rates.
According to diagnostic precipitation methods of calculating precipitable water, pseudo convection precipitable water, flux and flux divergence of moisture, cloud liquid water and cloud ice crystal, moisture weighted mean wind and condensation function precipitation rate, the continuous torrential rain that occurred over South China in June 2010 was diagnosed for its large scale moisture situation. Meanwhile, under the synoptic system of “upper trough-southwest vortex (SW vortex)-shear line-low level jet”, the extremely severe rainfall seen in Jiangxi, Fujian and Hunan in 19-20 June 2010 was simulated by a three nested, WRF model. The simulation and diagnostic analysis show that the large scale moisture field of the heavy rains in South China is characterized by “positive anomalous in the middle high latitudes-negative anomalous in the middle low latitudes-the subtropical ridge being positive anomaly towards west-anomalous activities of the monsoon trough” in East Asia, which causes the large scale vapor over the Bay of Bengal and the South China Sea to move into the Mainland of China. Many mesoscale rainstorms develop in high value areas of saturated water vapor, cloud water and cloud ice, where wind convergence and ascent motions take place and there are warm humid jet streams in its upstream. Both precipitation rates of condensation function and flux divergence of total water are products of the wind divergence initiating vertical motions, and the precipitation rate of condensation function gradually approaches approximation reasonable for explicit precipitation physical process in model atmosphere along with the improvement of spatial and temporal resolutions. When the model resolution reaches 4 km, rainfalls with the condensation function precipitation rate being 1-3 mm·min-1 can be simulated in the system of “SW vortex-shear line”, and the precipitation rate of collection growth of liquid and/or ice droplets in super saturated clouds can be described by their flux divergences and should be added to the precipitation rate of condensation function. Therefore, synoptic dynamic factors for the mesoscale rainfalls to occcur and develop in the model atmosphere is only the wind divergence field in weather system, for the vertical motions are determined by the divergence field with high spatial and temporal resolution in model atmosphere, so are all of the precipitation rates.
2014, 40(1):28-37.
DOI: 10.7519/j.issn.1000-0526.2014.01.004
Abstract:
The rainstorm with rainfall 226 mm in 6 h in the downstream of Changjiang River Valley on 27 July 2009 is simulated by WRF model. According to the model output, the diagnostic analysis is done for the shallow low vortex rainstorm event to investigate the development mechanism of the system. The results show that the low vortex locates at forepart of westerlies trough, existing only in the low level of troposphere. The dynamic structure and temperature moisture features all show that the vortex is a shallow system. The low vortex rainfall mainly happens near the warm shear line of the east part of the vortex. Two moisture source regions are in the South China Sea and the East Sea, and the thick moisture convergence is up to 600 hPa. The low vortex has strong baroclinic structure features. The analysis of vorticity equation shows that the divergence and convergence of wind field contribute mainly to the positive vorticity change rate, and the 3D wind shear distribution has an important correlation with vorticity. The dynamics of terrain obstruct makes the low vortex strengthened at leeward slope. The jets at high and low levels and the latent heat of condensation are helpful to the intensification of the low vortex and the torrential rainfall and the eastward motion. The wet isentropic surface perpendicular to the vortex surface means the low vortex is at mature stage, which predicts the rainfall is to weaken soon. When the developing condition of slantwise vorticity (Cd>0) keeps strengthening, it indicates that the combined result of baroclinicity, stability and wind vertical shear is also an important impact factor for the shallow low vortex developing and moving.
The rainstorm with rainfall 226 mm in 6 h in the downstream of Changjiang River Valley on 27 July 2009 is simulated by WRF model. According to the model output, the diagnostic analysis is done for the shallow low vortex rainstorm event to investigate the development mechanism of the system. The results show that the low vortex locates at forepart of westerlies trough, existing only in the low level of troposphere. The dynamic structure and temperature moisture features all show that the vortex is a shallow system. The low vortex rainfall mainly happens near the warm shear line of the east part of the vortex. Two moisture source regions are in the South China Sea and the East Sea, and the thick moisture convergence is up to 600 hPa. The low vortex has strong baroclinic structure features. The analysis of vorticity equation shows that the divergence and convergence of wind field contribute mainly to the positive vorticity change rate, and the 3D wind shear distribution has an important correlation with vorticity. The dynamics of terrain obstruct makes the low vortex strengthened at leeward slope. The jets at high and low levels and the latent heat of condensation are helpful to the intensification of the low vortex and the torrential rainfall and the eastward motion. The wet isentropic surface perpendicular to the vortex surface means the low vortex is at mature stage, which predicts the rainfall is to weaken soon. When the developing condition of slantwise vorticity (Cd>0) keeps strengthening, it indicates that the combined result of baroclinicity, stability and wind vertical shear is also an important impact factor for the shallow low vortex developing and moving.
2014, 40(1):38-47.
DOI: 10.7519/j.issn.1000-0526.2014.01.005
Abstract:
Using mesoscale WRF model, conventional meteorological data and NCEP/NCAR reanalysis data, the severe rainstorm process from 28 to 30 August in Henan Province is simulated and diagnosed with the equation of potential vorticity budget. Using the simulation results, this paper diagnoses the rainstorm by the potential vorticity and potential vorticity budget. The results show that WRF model has good simulation results to severe rainstorm. The simulated intensity and location of the rainstorm is well consistent with the observation. Potential vorticity can reflect the main dynamic and thermodynamic characteristics of the rainstorm. High potential vorticity value area has a better correlation with the rainstorm center, which is located in the southeast of the high potential vorticity area. The various items of potential vorticity budget can well show the main dynamic and thermodynamic characteristics of the rainstorm. The potential vorticity in the low middle atmosphere increases locally with the large value area corresponding to the rainstorm center in the process of rainstorm developing. Among the items of the potential vorticity budget, the latent heat and the horizontal advection and vertical transportation and friction are the main contribution items, of which the horizontal advection and the latent heat contribute positively to the local changes of potential vorticity. The latent heat makes the potential vorticity gradually increase. The horizontal advection is helpful for the potential vorticity to gather to the convergence zone of the flow field. The vertical transportation and friction make the negative contribution to the local changes of potential vorticity. The vertical transportation can transfer the potential vorticity from the lower to the high level and reduce the low level potential vorticity. Under the influence of the friction, the potential vorticity in low level is dissipatived and reduced.
Using mesoscale WRF model, conventional meteorological data and NCEP/NCAR reanalysis data, the severe rainstorm process from 28 to 30 August in Henan Province is simulated and diagnosed with the equation of potential vorticity budget. Using the simulation results, this paper diagnoses the rainstorm by the potential vorticity and potential vorticity budget. The results show that WRF model has good simulation results to severe rainstorm. The simulated intensity and location of the rainstorm is well consistent with the observation. Potential vorticity can reflect the main dynamic and thermodynamic characteristics of the rainstorm. High potential vorticity value area has a better correlation with the rainstorm center, which is located in the southeast of the high potential vorticity area. The various items of potential vorticity budget can well show the main dynamic and thermodynamic characteristics of the rainstorm. The potential vorticity in the low middle atmosphere increases locally with the large value area corresponding to the rainstorm center in the process of rainstorm developing. Among the items of the potential vorticity budget, the latent heat and the horizontal advection and vertical transportation and friction are the main contribution items, of which the horizontal advection and the latent heat contribute positively to the local changes of potential vorticity. The latent heat makes the potential vorticity gradually increase. The horizontal advection is helpful for the potential vorticity to gather to the convergence zone of the flow field. The vertical transportation and friction make the negative contribution to the local changes of potential vorticity. The vertical transportation can transfer the potential vorticity from the lower to the high level and reduce the low level potential vorticity. Under the influence of the friction, the potential vorticity in low level is dissipatived and reduced.
2014, 40(1):48-58.
DOI: 10.7519/j.issn.1000-0526.2014.01.006
Abstract:
The conventional observation, new generation weather radar, lightning locating monitoring and NCEP 1°×1° analysis data are used to analyze the synoptic causes of the elevated thunderstorm in early spring of 2012 that was accompanied by a variety of weather phenomena and a flow configuration model of the elevated thunderstorm is established. The results showed that: (1) the elevated thunderstorm occurs in the circulation situation of warm trough moving eastward and developing in middle latitudes. The near neutral conditions instability stratification above the top of the boundary layer (biased in favor of weak conditional instability), which is in the forcing effect of positive vorticity advection in front of trough and warm and wet advection at low levels, makes a larger range of strong upward motion above 700 hPa so that easterly winds in the rear of surface cold high has a role of cooling cushion on the production of the elevated convection. (2) There is a strong inverse temperature layer in the lower atmosphere where elevated thunderstorm exists. The warm and wet southwest low level jet in front of temperature ridge at 700 hPa provides ample moisture and energy for production of an elevated thunderstorm, causing weak conditions with unstable stratification and higher dew point above the top of low level temperature inversion. The combination of the two leads to the weak and most unstable convective available potential energy MUCAPE, whose value is between 10 and 50 J·kg-1. The elevated convection is caused by uplift of warm and wet block near and above the top of the inversion layer, corresponding to 1.0-3.0 m·s-1 maximum updrafts within thunderstorms. (3) The elevated thunderstorm occurs in strong baroclinic environment, where there is a strong dynamic instability, in the lower level 0-6 km and 0-3 km vertical wind shear values are (3.0-3.7)×10-3 s-1 and (5.0-5.3)×10-3 s-1 respectiveny. (4) The -10℃ and -20℃ layers in this process are respectively in the height of 5 km and 6.5 km, and the height of weak convective cloud top is more in the 6-8 km or above, exceeding the height of the freezing level and easily leading to the occurence of lightning. (5) From the flow configuration model, warm trough at high altitude, the strongly developed temperature ridge at middle and high layer, the warm and wet southwest low level jet at 700 hPa and cold boundary center, cold temperature trough, surface cold high pressure etc., make up a noteworthy affecting system. When these weather systems are favorable for configuration, the low level temperature inversion, the establishment of weak condition unstable stratification at middle layer and the likelihood of elevated thunderstorms should be concerned.
The conventional observation, new generation weather radar, lightning locating monitoring and NCEP 1°×1° analysis data are used to analyze the synoptic causes of the elevated thunderstorm in early spring of 2012 that was accompanied by a variety of weather phenomena and a flow configuration model of the elevated thunderstorm is established. The results showed that: (1) the elevated thunderstorm occurs in the circulation situation of warm trough moving eastward and developing in middle latitudes. The near neutral conditions instability stratification above the top of the boundary layer (biased in favor of weak conditional instability), which is in the forcing effect of positive vorticity advection in front of trough and warm and wet advection at low levels, makes a larger range of strong upward motion above 700 hPa so that easterly winds in the rear of surface cold high has a role of cooling cushion on the production of the elevated convection. (2) There is a strong inverse temperature layer in the lower atmosphere where elevated thunderstorm exists. The warm and wet southwest low level jet in front of temperature ridge at 700 hPa provides ample moisture and energy for production of an elevated thunderstorm, causing weak conditions with unstable stratification and higher dew point above the top of low level temperature inversion. The combination of the two leads to the weak and most unstable convective available potential energy MUCAPE, whose value is between 10 and 50 J·kg-1. The elevated convection is caused by uplift of warm and wet block near and above the top of the inversion layer, corresponding to 1.0-3.0 m·s-1 maximum updrafts within thunderstorms. (3) The elevated thunderstorm occurs in strong baroclinic environment, where there is a strong dynamic instability, in the lower level 0-6 km and 0-3 km vertical wind shear values are (3.0-3.7)×10-3 s-1 and (5.0-5.3)×10-3 s-1 respectiveny. (4) The -10℃ and -20℃ layers in this process are respectively in the height of 5 km and 6.5 km, and the height of weak convective cloud top is more in the 6-8 km or above, exceeding the height of the freezing level and easily leading to the occurence of lightning. (5) From the flow configuration model, warm trough at high altitude, the strongly developed temperature ridge at middle and high layer, the warm and wet southwest low level jet at 700 hPa and cold boundary center, cold temperature trough, surface cold high pressure etc., make up a noteworthy affecting system. When these weather systems are favorable for configuration, the low level temperature inversion, the establishment of weak condition unstable stratification at middle layer and the likelihood of elevated thunderstorms should be concerned.
2014, 40(1):59-65.
DOI: 10.7519/j.issn.1000-0526.2014.01.007
Abstract:
To better study microphysical characteristics during snowfall process, drop size spectra were collected with an optical disdrometer during the snowstorm event in 11-12 November 2009 in the southern mountainous area of Jinan. The characteristics of the microphysical parameters, the drop size distribution and speed spectral distribution are investigated. It is found that: (1) during the snowstorm, precipitation intensity and number concentration, maximum diameter, and the radar reflectivity factor have positive linear correlations; the precipitation intensity and the maximum diameter has a close relationship; precipitation intensity is decided by the maximum diameter. (2) In the snow process, the spectrum type distributions are of unimodal and index distributions, and the peak value of number concentration is focuses around 0.5 mm. The concentration distribution of each particle size file is inhomogeneous. (3) The velocity spectra are mainly single peak distributions, and the terminal velocity essentially lies in the range of 0.375-2 m·s-1, which almost has no change with the increase of diameter.
To better study microphysical characteristics during snowfall process, drop size spectra were collected with an optical disdrometer during the snowstorm event in 11-12 November 2009 in the southern mountainous area of Jinan. The characteristics of the microphysical parameters, the drop size distribution and speed spectral distribution are investigated. It is found that: (1) during the snowstorm, precipitation intensity and number concentration, maximum diameter, and the radar reflectivity factor have positive linear correlations; the precipitation intensity and the maximum diameter has a close relationship; precipitation intensity is decided by the maximum diameter. (2) In the snow process, the spectrum type distributions are of unimodal and index distributions, and the peak value of number concentration is focuses around 0.5 mm. The concentration distribution of each particle size file is inhomogeneous. (3) The velocity spectra are mainly single peak distributions, and the terminal velocity essentially lies in the range of 0.375-2 m·s-1, which almost has no change with the increase of diameter.
2014, 40(1):66-75.
DOI: 10.7519/j.issn.1000-0526.2014.01.008
Abstract:
Using self adaption Kalman filter method, bias correction of surface parameter products of large scale numerical prediction system are done. Through studying the appreciated method of obtaining bias correction coefficient, the filter method is improved and the forecasts of large scale model parameters such as 2 m temperature and 10 m wind are improved accordingly. Based on corrected large scale model forecast field and high resolution observatory field, downscaling vector function is obtained, and refined statistical downscaling meteorological parameter forecasts are created and it is an effective way to do high resolution meteorological parameter forecasts.
Using self adaption Kalman filter method, bias correction of surface parameter products of large scale numerical prediction system are done. Through studying the appreciated method of obtaining bias correction coefficient, the filter method is improved and the forecasts of large scale model parameters such as 2 m temperature and 10 m wind are improved accordingly. Based on corrected large scale model forecast field and high resolution observatory field, downscaling vector function is obtained, and refined statistical downscaling meteorological parameter forecasts are created and it is an effective way to do high resolution meteorological parameter forecasts.
2014, 40(1):76-85.
DOI: 10.7519/j.issn.1000-0526.2014.01.009
Abstract:
In order to evaluate the improvement of the GPS/PWV data assimilation to the initial humidity field and precipitation forecast field of numerical model, a series of assimilation experiments were performed using the LAPS (Local Analysis and Prediction System) and WRF (Weather Research and Forecasting) model. One heavy rainfall process in Hubei Area was taken as the experimental research object. The result shows that the assimilation of GPS/PWV is effective in reducing the error of PW in the LAPS humidity field, however its impact on potential height and wind fields is not so notable. The impacts of GPS/PWV are greater than radar data by comparing the total precipitable water analyzed by LAPS in different schemes. Different weather forecast scores show that the initial moisture field in WRF is significantly improved by using GPS/PWV data, and the improved moisture field in initial condition leads to positive effect on the forecast of rainfall.
In order to evaluate the improvement of the GPS/PWV data assimilation to the initial humidity field and precipitation forecast field of numerical model, a series of assimilation experiments were performed using the LAPS (Local Analysis and Prediction System) and WRF (Weather Research and Forecasting) model. One heavy rainfall process in Hubei Area was taken as the experimental research object. The result shows that the assimilation of GPS/PWV is effective in reducing the error of PW in the LAPS humidity field, however its impact on potential height and wind fields is not so notable. The impacts of GPS/PWV are greater than radar data by comparing the total precipitable water analyzed by LAPS in different schemes. Different weather forecast scores show that the initial moisture field in WRF is significantly improved by using GPS/PWV data, and the improved moisture field in initial condition leads to positive effect on the forecast of rainfall.
2014, 40(1):86-93.
DOI: 10.7519/j.issn.1000-0526.2014.01.010
Abstract:
Using the conventional observation data, daily precipitation data of manual observation and automatic observation in Hubei Province, NCEP reanalysis data of 0.5°×0.5°, this paper analyzed the effect of frontogenesis function in three intensest rainstorm processes which occurred during the Meiyu period of Hubei Province in June 2011. The results are as follows: (1) The Meiyu process in Hubei in 2011 is of the single blocking high type, presenting three different types of rainstorm processes, during which the frontogenesis appears in the mid level of atmosphere. (2) The frontogenesis of middle atmosphere is mainly triggered by vertical frontogenesis, which is advantageous to the convective precipitation. The frontogenesis of low level is attributed to the horizontal frontogenesis, which was helpful to convey water vapour and convergence lifting. (3) When the middle level frontogenesis occurs after the low level, there will be the long time heavy rain; when the middle level frontogenesis occurs before the low level, there will be short time heavy rain. (4) The vertical frontolysis in low level and the horizontal frontogenesis counteract each other, indicating that the convection in the low level is stable, and the horizontal convergence is not strong, which is not advantageous to occurrence of heavy rains.
Using the conventional observation data, daily precipitation data of manual observation and automatic observation in Hubei Province, NCEP reanalysis data of 0.5°×0.5°, this paper analyzed the effect of frontogenesis function in three intensest rainstorm processes which occurred during the Meiyu period of Hubei Province in June 2011. The results are as follows: (1) The Meiyu process in Hubei in 2011 is of the single blocking high type, presenting three different types of rainstorm processes, during which the frontogenesis appears in the mid level of atmosphere. (2) The frontogenesis of middle atmosphere is mainly triggered by vertical frontogenesis, which is advantageous to the convective precipitation. The frontogenesis of low level is attributed to the horizontal frontogenesis, which was helpful to convey water vapour and convergence lifting. (3) When the middle level frontogenesis occurs after the low level, there will be the long time heavy rain; when the middle level frontogenesis occurs before the low level, there will be short time heavy rain. (4) The vertical frontolysis in low level and the horizontal frontogenesis counteract each other, indicating that the convection in the low level is stable, and the horizontal convergence is not strong, which is not advantageous to occurrence of heavy rains.
2014, 40(1):94-100.
DOI: 10.7519/j.issn.1000-0526.2014.01.011
Abstract:
Based on a homogenized surface temperature dataset of 20 meteorological stations in Beijing, the urbanization effect on seasonal and annual daily minimum temperature, mean temperature and maximum temperature in Beijing during 1978-2008 is evaluated in this paper. The results show that for the annual minimum, mean and maximum temperatures, their spatial distributions show an increasing trend in Beijing area from north to south and from west to east, and there exists an obvious heat island for the annual maximum air temperature. This region is undergoing rapid increases in the minimum, mean and maximum temperatures. Regarding the minimum and daily mean temperatures the most affected stations are located in urban area and near suburban area, while for the maximum temperature the most affected stations are located in the middle zone from north to south in Beijing Area. The effect of urbanization on temperature increase is the most obvious in Beijing Observatory Station, followed by the effect on urban area stations and all the weather stations. In autumn, the urbanization effect on the minimum and daily mean temperature is more significant and in summer, the urbanization effect on maximum is more significant.
Based on a homogenized surface temperature dataset of 20 meteorological stations in Beijing, the urbanization effect on seasonal and annual daily minimum temperature, mean temperature and maximum temperature in Beijing during 1978-2008 is evaluated in this paper. The results show that for the annual minimum, mean and maximum temperatures, their spatial distributions show an increasing trend in Beijing area from north to south and from west to east, and there exists an obvious heat island for the annual maximum air temperature. This region is undergoing rapid increases in the minimum, mean and maximum temperatures. Regarding the minimum and daily mean temperatures the most affected stations are located in urban area and near suburban area, while for the maximum temperature the most affected stations are located in the middle zone from north to south in Beijing Area. The effect of urbanization on temperature increase is the most obvious in Beijing Observatory Station, followed by the effect on urban area stations and all the weather stations. In autumn, the urbanization effect on the minimum and daily mean temperature is more significant and in summer, the urbanization effect on maximum is more significant.
12 Research and Application of Flash Flood Early Warning Method Based on Dynamic Critical Precipitation
2014, 40(1):101-107.
DOI: 10.7519/j.issn.1000-0526.2014.01.012
Abstract:
A flash flood early warning method based on dynamic critical precipitation is proposed in this paper. The method calculates soil moisture saturation using the Xin’anjiang model, then sets up forewarning discriminant functions for three time scales, 6 h, 12 h and 24 h, using Widrow Hoff algorithm of minimum mean square error criteria, and based on soil moisture saturation and maximum 6 h, 12 h and 24 h precipitation before each flood event. With this method, together with rainfall data of the 17 flood events occurring during the period from 2003 to 2009, wich are obtained at precipitation stations in Pihe Basin parameters for the model are calibrated and the method is applied in 10 historical flash flood events to verify the three time scale forewarning discriminent functions. The correct forecast rate is over 70%, demonstrating that the method is reliable and can be used to flash flood forecasting and early warning.
A flash flood early warning method based on dynamic critical precipitation is proposed in this paper. The method calculates soil moisture saturation using the Xin’anjiang model, then sets up forewarning discriminant functions for three time scales, 6 h, 12 h and 24 h, using Widrow Hoff algorithm of minimum mean square error criteria, and based on soil moisture saturation and maximum 6 h, 12 h and 24 h precipitation before each flood event. With this method, together with rainfall data of the 17 flood events occurring during the period from 2003 to 2009, wich are obtained at precipitation stations in Pihe Basin parameters for the model are calibrated and the method is applied in 10 historical flash flood events to verify the three time scale forewarning discriminent functions. The correct forecast rate is over 70%, demonstrating that the method is reliable and can be used to flash flood forecasting and early warning.
2014, 40(1):108-113.
DOI: 10.7519/j.issn.1000-0526.2014.01.013
Abstract:
Based on daily emergency case data of cerebrovascular disease in Beijing during 2006-2010, which are obtained from the Beijing urgent care centre (120). The association between the daily meteorological factors and hospital emergency visits for cerebrovascular disease in different seasons in Beijing is explored. Then we choose meteorological factors with regression method so as to obtain the forecast factors which are finally used to build forecast models in different seasons based on the ANN (artificial neural network) method, and the daily hospital visit numbers are divided into four grades by using multiple regression probability grade analysis. The results show that: (1) There are obvious seasonal and diurnal variations in the number of acute cerebrovascular disease, the number of cases is significantly higher in spring and winter than in summer and autumn, and concentrate mainly in 09:00-14:00 BT. (2) The meteorological factors have obvious hysteresis to induce the recurrence of cerebrovascular disease. In addition, statistical results show that the condition of high temperature and humidity weather in summer or cold air activity in winter and autumn may aggravate disease. (3) The models in spring, autumn and winter are used to forecast daily disease grade of new samples, the test results show the complete accuracy exceeds 30%; If the difference between the forecasted grade and actual grade is no more than 1, the accuracy exceeds 60%. The research results offer scientific reference for preventing the development of cerebrovascular disease and scheduling such emergency measures as 120 emergency vehicles.
Based on daily emergency case data of cerebrovascular disease in Beijing during 2006-2010, which are obtained from the Beijing urgent care centre (120). The association between the daily meteorological factors and hospital emergency visits for cerebrovascular disease in different seasons in Beijing is explored. Then we choose meteorological factors with regression method so as to obtain the forecast factors which are finally used to build forecast models in different seasons based on the ANN (artificial neural network) method, and the daily hospital visit numbers are divided into four grades by using multiple regression probability grade analysis. The results show that: (1) There are obvious seasonal and diurnal variations in the number of acute cerebrovascular disease, the number of cases is significantly higher in spring and winter than in summer and autumn, and concentrate mainly in 09:00-14:00 BT. (2) The meteorological factors have obvious hysteresis to induce the recurrence of cerebrovascular disease. In addition, statistical results show that the condition of high temperature and humidity weather in summer or cold air activity in winter and autumn may aggravate disease. (3) The models in spring, autumn and winter are used to forecast daily disease grade of new samples, the test results show the complete accuracy exceeds 30%; If the difference between the forecasted grade and actual grade is no more than 1, the accuracy exceeds 60%. The research results offer scientific reference for preventing the development of cerebrovascular disease and scheduling such emergency measures as 120 emergency vehicles.
2014, 40(1):114-118.
DOI: 10.7519/j.issn.1000-0526.2014.01.014
Abstract:
Based on historic visibility data of 12 stations and observed data of visibility, relative humidity, and aerosol during 2009-2011 in Tianjin, the basic characteristics of low visibility is analyzed. In addition, the atmospheric chemical model of WRF Chem is used to simulate the atmospheric horizontal visibility from October 2010 to January 2011 in Tianjin. The results show that low visibility mainly happens in every November to the next January. The atmospheric horizontal visibility can be better calculated on the basis of acquisition of PM2.5, PM10 and the relative humidity. And the use of WRF Chem atmospheric chemical model and fitting formula, the visibility can be effectively simulated and forecasted.
Based on historic visibility data of 12 stations and observed data of visibility, relative humidity, and aerosol during 2009-2011 in Tianjin, the basic characteristics of low visibility is analyzed. In addition, the atmospheric chemical model of WRF Chem is used to simulate the atmospheric horizontal visibility from October 2010 to January 2011 in Tianjin. The results show that low visibility mainly happens in every November to the next January. The atmospheric horizontal visibility can be better calculated on the basis of acquisition of PM2.5, PM10 and the relative humidity. And the use of WRF Chem atmospheric chemical model and fitting formula, the visibility can be effectively simulated and forecasted.
2014, 40(1):119-125.
DOI: 10.7519/j.issn.1000-0526.2014.01.015
Abstract:
In summer 2013, the mean precipitation in China is 339.9 mm, 4.5% more than normal. The precipitation is more than normal in North China and Northeast China and less than normal in the regions from Huanghuai to northern Jiangnan, which shows the North more and south less situation. Meanwhile, the summer average temperature in China is 21.7℃, which is 0.7℃ above normal and equal to the highest record in 2006 and 2011. Temperature in the regions from Huanghuai to Northern Jiangnan is extremely higher than normal and extreme high temperature events continually happened in these regions. In addition, possible causations for more precipitation in Northern China and extremely warmer in South China is also analyzed. The results show that the area from southeastern Europe to Northern part of East Asia is controlled by the weak East Asia trough which is not good for the cold air to move south into South China. The East Asia summer monsoon is stronger than normal and the West Pacific subtropical high (briefly subtropical high) is more northern than normal, which is good for low latitude warm and humid water vapor to transport to North China. The warm and cold airs converge in North China and Northeast China, forming the water vapor convergence and finally causing more precipitation in these regions. Meanwhile, subtropical high frequently strengthens and west expands, making the most part of southern China is always controlled by the west part of subtropical high. This circulation anomaly causes stronger downward air movement, weaker convection and less precipitation in these regions, then finally resulting in the extreme high temperature event in southern China.
In summer 2013, the mean precipitation in China is 339.9 mm, 4.5% more than normal. The precipitation is more than normal in North China and Northeast China and less than normal in the regions from Huanghuai to northern Jiangnan, which shows the North more and south less situation. Meanwhile, the summer average temperature in China is 21.7℃, which is 0.7℃ above normal and equal to the highest record in 2006 and 2011. Temperature in the regions from Huanghuai to Northern Jiangnan is extremely higher than normal and extreme high temperature events continually happened in these regions. In addition, possible causations for more precipitation in Northern China and extremely warmer in South China is also analyzed. The results show that the area from southeastern Europe to Northern part of East Asia is controlled by the weak East Asia trough which is not good for the cold air to move south into South China. The East Asia summer monsoon is stronger than normal and the West Pacific subtropical high (briefly subtropical high) is more northern than normal, which is good for low latitude warm and humid water vapor to transport to North China. The warm and cold airs converge in North China and Northeast China, forming the water vapor convergence and finally causing more precipitation in these regions. Meanwhile, subtropical high frequently strengthens and west expands, making the most part of southern China is always controlled by the west part of subtropical high. This circulation anomaly causes stronger downward air movement, weaker convection and less precipitation in these regions, then finally resulting in the extreme high temperature event in southern China.
2014, 40(1):126-131.
DOI: 10.7519/j.issn.1000-0526.2014.01.016
Abstract:
The following are the main characteristics of the general atmospheric circulation in October 2013. There is one strong polar vortex center over the Northern Hemisphere. The circulation presents a four wave pattern in middle high latitudes. The meridional circulation is more obvious, the south branch trough and the West Pacific subtropical high are stronger than normal years. The monthly mean precipitation is 30.8 mm, 14% less than normal. The monthly mean temperature is 11.1℃, which is 0.8℃ lower than normal years. There are four cold air processes affecting China during this month. Typhoon Fitow makes landfall in southern part of East China and northern part of South China, bringing a severe rainfall process. The autumn drought across the central part of Jiangnan Region and Henan Province continues or develops. Besides, most parts of the central and eastern China suffers from fog and haze events.
The following are the main characteristics of the general atmospheric circulation in October 2013. There is one strong polar vortex center over the Northern Hemisphere. The circulation presents a four wave pattern in middle high latitudes. The meridional circulation is more obvious, the south branch trough and the West Pacific subtropical high are stronger than normal years. The monthly mean precipitation is 30.8 mm, 14% less than normal. The monthly mean temperature is 11.1℃, which is 0.8℃ lower than normal years. There are four cold air processes affecting China during this month. Typhoon Fitow makes landfall in southern part of East China and northern part of South China, bringing a severe rainfall process. The autumn drought across the central part of Jiangnan Region and Henan Province continues or develops. Besides, most parts of the central and eastern China suffers from fog and haze events.
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ISSN:1000-0526 CN:11-2282/P