ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 40,Issue 10,2014 Table of Contents
2014, 40(10):1165-1173.
DOI: 10.7519/j.issn.1000-0526.2014.10.001
Abstract:
Based on the data observed from an intensive GPS sounding experiment and the comprehensive measurements of boundary layer in Dali of Yunnan Province during March, May and July 2008, the heights of CBL (convective boundary layer) and SBL(stable boundary layer) are calculated with approaches of temperature gradient and inversion layer strength and sensible heat flux, latent heat flux, turbulent kinetic energy, shear item and buoyancy item are obtained with eddy correlation method. The apparent heat source Q1, which is calculated from the NCEP reanalysis data, presents the similar diurnal cycles to the turbulent energy components and turbulent flux, reflecting a close connection of the plateau’s heat source variations with the diurnal changes in turbulent transport of hydrothermal process in the underlying surface. The comprehensive analysis on the vertical profiles of variables about turbulence and thermodynamics reveals the significant correlations among sensible heat flux, latent heat flux, apparent heat source and buoyancy item, implying an important contribution of thermodynamic turbulence transport to the Q1 in the near surface layer over the southeastern edges of the Tibetan Plateau. The buoyancy item and turbulent energy play an important role in formation of the near surface Q1, vortex dynamics, thermodynamic mixing structure. The lower layer Q1 and moisture sink are closely associated with the boundary layer height. This comprehensive analysis describs a physical linkage of thermodynamic turbulence transport with atmospheric heat source, vortex dynamical process and thermodynamic mixing layer structure to understand the interaction of turbulence convection and atmospheric thermodynamic process in the active convection region over the southeastern edges of the Tibetan Plateau.
Based on the data observed from an intensive GPS sounding experiment and the comprehensive measurements of boundary layer in Dali of Yunnan Province during March, May and July 2008, the heights of CBL (convective boundary layer) and SBL(stable boundary layer) are calculated with approaches of temperature gradient and inversion layer strength and sensible heat flux, latent heat flux, turbulent kinetic energy, shear item and buoyancy item are obtained with eddy correlation method. The apparent heat source Q1, which is calculated from the NCEP reanalysis data, presents the similar diurnal cycles to the turbulent energy components and turbulent flux, reflecting a close connection of the plateau’s heat source variations with the diurnal changes in turbulent transport of hydrothermal process in the underlying surface. The comprehensive analysis on the vertical profiles of variables about turbulence and thermodynamics reveals the significant correlations among sensible heat flux, latent heat flux, apparent heat source and buoyancy item, implying an important contribution of thermodynamic turbulence transport to the Q1 in the near surface layer over the southeastern edges of the Tibetan Plateau. The buoyancy item and turbulent energy play an important role in formation of the near surface Q1, vortex dynamics, thermodynamic mixing structure. The lower layer Q1 and moisture sink are closely associated with the boundary layer height. This comprehensive analysis describs a physical linkage of thermodynamic turbulence transport with atmospheric heat source, vortex dynamical process and thermodynamic mixing layer structure to understand the interaction of turbulence convection and atmospheric thermodynamic process in the active convection region over the southeastern edges of the Tibetan Plateau.
2014, 40(10):1174-1182.
DOI: 10.7519/j.issn.1000-0526.2014.10.002
Abstract:
Based on the rain gauge data from automatic weather stations, conventional observations and NCEP analysis data, the extreme rainstorm that hit Suining City from 30 June to 2 July 2013 and the relationship between the extreme rainstorm and the LLJ evolution are studied primarily. This extrem event was caused by the coupling interaction between plateau and southwest vortexes. The results show that the high level vortex development is strengthened when the coupling interaction occurs between plateau and southwest vortexes, stimulating the generation of rainstorms in Suining City. Jet stream provides unstable energy for the development of high level vortex. Ultra low level jet and low level jet cannot cause a strong rainfall immediately, and sometimes severe rainfall process may occur two hours later. The degree of increase in the low level jet index (I) and the intensity of rainfall have a direct proportional relationship.
Based on the rain gauge data from automatic weather stations, conventional observations and NCEP analysis data, the extreme rainstorm that hit Suining City from 30 June to 2 July 2013 and the relationship between the extreme rainstorm and the LLJ evolution are studied primarily. This extrem event was caused by the coupling interaction between plateau and southwest vortexes. The results show that the high level vortex development is strengthened when the coupling interaction occurs between plateau and southwest vortexes, stimulating the generation of rainstorms in Suining City. Jet stream provides unstable energy for the development of high level vortex. Ultra low level jet and low level jet cannot cause a strong rainfall immediately, and sometimes severe rainfall process may occur two hours later. The degree of increase in the low level jet index (I) and the intensity of rainfall have a direct proportional relationship.
2014, 40(10):1183-1193.
DOI: 10.7519/j.issn.1000-0526.2014.10.003
Abstract:
MICAPS data, Doppler radar data, NCEP data, etc. are used to analyze the characteristics and causes of a meso β scale flood causing rainstorm on Loess Plateau from 20:00 BT 26 to 20:00 BT 27 July 2012. The results show that the activity of low energy ratio tongue in the surface layer is one of the trigger mechanisms for the two severe raifalls. The two periods of torrential rains both correspond to the establishment of easterly winds relative to storm airflow faster than 20 m·s-1 that is adjacent to the north of the storm zone within 1 km of the boundary layer, while easterly winds relative to storm airflow within 1 km of the boundary layer close to the north of the storm zone get weakened and vanished, or the range drastically reduces, causing the severe precipitation to lesson or stop correspondingly. Analysis on vorticity revenue and expenditure shows that before the first rainstorm the dominant factor is horizontal advection item in the formation of strong negative vorticity revenue and expenditure near 300 hPa. Before the second rainstorm, the dominant factors are twisting item and vertical transportation item in the formation of strong positive vorticity revenue and expenditure in the 450-300 hPa at the same time. Analysis on apparent heat source and apparent moisture sink shows that before the first rainstorm, the appearance of apparent heat source near 300 hPa is quite strong cooling layer. Before the second rainstorm, positive heating layer is formed for the apparent moisture sink is much larger than the apparent heat source in the 800-500 hPa. The formation of strong heating layer whose peak is close to 11 K·(6 h)-1 for the heat source is much larger than apparent moisture sink in the 500-200 hPa. Due to the role of the apparent heat source, cooling layer is formed in 200-130 hPa.
MICAPS data, Doppler radar data, NCEP data, etc. are used to analyze the characteristics and causes of a meso β scale flood causing rainstorm on Loess Plateau from 20:00 BT 26 to 20:00 BT 27 July 2012. The results show that the activity of low energy ratio tongue in the surface layer is one of the trigger mechanisms for the two severe raifalls. The two periods of torrential rains both correspond to the establishment of easterly winds relative to storm airflow faster than 20 m·s-1 that is adjacent to the north of the storm zone within 1 km of the boundary layer, while easterly winds relative to storm airflow within 1 km of the boundary layer close to the north of the storm zone get weakened and vanished, or the range drastically reduces, causing the severe precipitation to lesson or stop correspondingly. Analysis on vorticity revenue and expenditure shows that before the first rainstorm the dominant factor is horizontal advection item in the formation of strong negative vorticity revenue and expenditure near 300 hPa. Before the second rainstorm, the dominant factors are twisting item and vertical transportation item in the formation of strong positive vorticity revenue and expenditure in the 450-300 hPa at the same time. Analysis on apparent heat source and apparent moisture sink shows that before the first rainstorm, the appearance of apparent heat source near 300 hPa is quite strong cooling layer. Before the second rainstorm, positive heating layer is formed for the apparent moisture sink is much larger than the apparent heat source in the 800-500 hPa. The formation of strong heating layer whose peak is close to 11 K·(6 h)-1 for the heat source is much larger than apparent moisture sink in the 500-200 hPa. Due to the role of the apparent heat source, cooling layer is formed in 200-130 hPa.
2014, 40(10):1194-1206.
DOI: 10.7519/j.issn.1000-0526.2014.10.004
Abstract:
Based on Doppler radar data, sounding data and precipitation data, 537 flash heavy rain processes in Puer and Xishuangbanna are analyzed. Three short time severe precipitation models are established, including the flash heavy rain into the low centroid and weak convergence type, the low centroid and convergence type and the high centroid type. In addition, comparative analysis is carried out on the features of intensity, velocity, life cycle, vertical wind shear and interrelationships of convergence and heavy rainfall duration, shear line in convergence zone and precipitation intensity, DVIL and precipitations of different types. Then the warning methods are derived as follows: if meeting the following conditions, it is a highly possible to see flash heavy rains. First, in the case of a lower centroid of echo in heavy precipitation, if echo intensity is 40-45 dBz and not inclined, echo intensity remains unchanged by vertical direction, H40 dBz≥H0, overall length by velocity of echo intensity about 40 dBz is more than or equal to 0.67 h in 0℃ layer, we can give warning time of 30-40 min before flash heavy rainfall. Second, in the case of a high centroid of echo in heavy precipitation, if the intensity of echo is uniform (40-45 dBz), the width of echo is greater than or equal to 3 km on the edge of strong echo, overall length by velocity of echo intensity about 40 dBz is more than or equal to 0.47 h in 0℃ layer, we can give warning time of about 28 min before flash heavy rainfall. Finally, the genesis for flash heavy rains is discussed.
Based on Doppler radar data, sounding data and precipitation data, 537 flash heavy rain processes in Puer and Xishuangbanna are analyzed. Three short time severe precipitation models are established, including the flash heavy rain into the low centroid and weak convergence type, the low centroid and convergence type and the high centroid type. In addition, comparative analysis is carried out on the features of intensity, velocity, life cycle, vertical wind shear and interrelationships of convergence and heavy rainfall duration, shear line in convergence zone and precipitation intensity, DVIL and precipitations of different types. Then the warning methods are derived as follows: if meeting the following conditions, it is a highly possible to see flash heavy rains. First, in the case of a lower centroid of echo in heavy precipitation, if echo intensity is 40-45 dBz and not inclined, echo intensity remains unchanged by vertical direction, H40 dBz≥H0, overall length by velocity of echo intensity about 40 dBz is more than or equal to 0.67 h in 0℃ layer, we can give warning time of 30-40 min before flash heavy rainfall. Second, in the case of a high centroid of echo in heavy precipitation, if the intensity of echo is uniform (40-45 dBz), the width of echo is greater than or equal to 3 km on the edge of strong echo, overall length by velocity of echo intensity about 40 dBz is more than or equal to 0.47 h in 0℃ layer, we can give warning time of about 28 min before flash heavy rainfall. Finally, the genesis for flash heavy rains is discussed.
2014, 40(10):1207-1215.
DOI: 10.7519/j.issn.1000-0526.2014.10.005
Abstract:
Using the daily maximum, minimum and mean temperature data from 733 stations of 10 provinces (cities) in Southern China from 1960 to 2013, the extremely high temperature of 2013 in Southern China was deeply analyzed. The results showed that the high temperature in summer of 2013 in Southern China has significant characteristics of clustering, covering the middle and lower reaches of the Yangtze River and Chongqing areas. The high temperature has the feature of persistence, which is constituted of four high temperature processes mainly. The third time of high temperature from 22 July to 21 August is the strongest and broadest. Further analysis on the regional extreme temperatures showed that the average temperature, the average maximum temperature, and the average minimum temperature all have broken the records in the late 50 years. The time and intensity of average high temperature exceeds the extreme value in history. The extreme value scope of high temperature time and high temperature strength expand to the north, and the values of high temperature center exceed the historical records. The frequency of extremely high temperature events in 2013 has broken the historical records, and is extremely outstanding in August.
Using the daily maximum, minimum and mean temperature data from 733 stations of 10 provinces (cities) in Southern China from 1960 to 2013, the extremely high temperature of 2013 in Southern China was deeply analyzed. The results showed that the high temperature in summer of 2013 in Southern China has significant characteristics of clustering, covering the middle and lower reaches of the Yangtze River and Chongqing areas. The high temperature has the feature of persistence, which is constituted of four high temperature processes mainly. The third time of high temperature from 22 July to 21 August is the strongest and broadest. Further analysis on the regional extreme temperatures showed that the average temperature, the average maximum temperature, and the average minimum temperature all have broken the records in the late 50 years. The time and intensity of average high temperature exceeds the extreme value in history. The extreme value scope of high temperature time and high temperature strength expand to the north, and the values of high temperature center exceed the historical records. The frequency of extremely high temperature events in 2013 has broken the historical records, and is extremely outstanding in August.
2014, 40(10):1216-1229.
DOI: 10.7519/j.issn.1000-0526.2014.10.006
Abstract:
Severe droughts occurred in Southwest China continuously in 4 years’ autumn, winter, spring beginning from 2009. Because of the long duration, large scope and heavy degrees, the drought has caused huge economic losses, seriously impacting on agroforestry production and people’s life in arid zones. In this paper, the causes of the continuous drought are analyzed from the impacts of the anomalies of large scale atmospheric circulation, water vapor transportation, the Pacific and Indian Ocean SST, stratospheric polar vortex strength by analyzing a variety of data. The results show that the common backgrounds of the 4 years’ continuous drought are weaker south branch trough, less water vapor transport over the Bay of Bengal and easterly cold air mass caused by AO negative anomalies which are produced by abnormal wave activities during weak polar vortex. The abnormal changes of tropical SST during the drought over Southwest China play important roles in blocking water vapor transport over the Bay of Bengal and South China Sea. In the La Nina event, the effect of the tropical Indian Ocean SST changes in winter and spring is more outstanding. The phase of AO is always changed by the dynamic couple between stratosphere and troposphere in winter and spring, and the intensity and duration of the abnormally negative phase of AO have significant effects on the drought that occurred in Southwest China in the autumn, winter and spring of 4 consecutive years.
Severe droughts occurred in Southwest China continuously in 4 years’ autumn, winter, spring beginning from 2009. Because of the long duration, large scope and heavy degrees, the drought has caused huge economic losses, seriously impacting on agroforestry production and people’s life in arid zones. In this paper, the causes of the continuous drought are analyzed from the impacts of the anomalies of large scale atmospheric circulation, water vapor transportation, the Pacific and Indian Ocean SST, stratospheric polar vortex strength by analyzing a variety of data. The results show that the common backgrounds of the 4 years’ continuous drought are weaker south branch trough, less water vapor transport over the Bay of Bengal and easterly cold air mass caused by AO negative anomalies which are produced by abnormal wave activities during weak polar vortex. The abnormal changes of tropical SST during the drought over Southwest China play important roles in blocking water vapor transport over the Bay of Bengal and South China Sea. In the La Nina event, the effect of the tropical Indian Ocean SST changes in winter and spring is more outstanding. The phase of AO is always changed by the dynamic couple between stratosphere and troposphere in winter and spring, and the intensity and duration of the abnormally negative phase of AO have significant effects on the drought that occurred in Southwest China in the autumn, winter and spring of 4 consecutive years.
2014, 40(10):1230-1239.
DOI: 10.7519/j.issn.1000-0526.2014.10.007
Abstract:
Based on the monthly temperature data of 192 observational stations in South China, NCEP/NCAR reanalysis monthly temperature data and ENSO monitoring data by NCC, the relationship between winter temperature in South China and ENSO is studied by using the methods of correlation analysis, composition analysis and so on. The results show that the response of the winter temperature in South China to La Ni〖AKn~D〗a event is more obvious than to El Ni〖AKn~D〗o event. In La Ni〖AKn~D〗a year, the winter temperature in South China is lower than in normal years. The significantly low temperature appears in extremely strong La Ni〖AKn~D〗a years, but the temperature is high obviously in central pattern La Ni〖AKn~D〗a events. The winter temperature in South China is mainly lower (higher) than that in normal years when La Ni〖AKn~D〗a (El Ni〖AKn~D〗o) event is in east pattern, and the peak months of Nino SSTA are in autumn and winter. In La Ni〖AKn~D〗a years, there is an abnormal cyclone circulation in the Pacific subtropical high and abnormal north wind in the low troposphere. North Pacific high, Ural Mountains high ridge and the south of East Asia trough also become strong, the West Pacific subtropical high becomes weak in the middle troposphere. The meridional circulation in middle high latitude in East Asia is evident. East Asian winter monsoon is strong in case of La Ni〖AKn~D〗a events, the winter temperature in most regions of China including South China is lower than that in normal years, and vice versa. There are significant interdecadal differences of the effect of El Ni〖AKn~D〗o event on the winter temperature in South China. SST variation obviously corresponding to interdecadal variation of the winter temperature in South China is found in North Pacific, and the relationship between the variation and ENSO is not obvious.
Based on the monthly temperature data of 192 observational stations in South China, NCEP/NCAR reanalysis monthly temperature data and ENSO monitoring data by NCC, the relationship between winter temperature in South China and ENSO is studied by using the methods of correlation analysis, composition analysis and so on. The results show that the response of the winter temperature in South China to La Ni〖AKn~D〗a event is more obvious than to El Ni〖AKn~D〗o event. In La Ni〖AKn~D〗a year, the winter temperature in South China is lower than in normal years. The significantly low temperature appears in extremely strong La Ni〖AKn~D〗a years, but the temperature is high obviously in central pattern La Ni〖AKn~D〗a events. The winter temperature in South China is mainly lower (higher) than that in normal years when La Ni〖AKn~D〗a (El Ni〖AKn~D〗o) event is in east pattern, and the peak months of Nino SSTA are in autumn and winter. In La Ni〖AKn~D〗a years, there is an abnormal cyclone circulation in the Pacific subtropical high and abnormal north wind in the low troposphere. North Pacific high, Ural Mountains high ridge and the south of East Asia trough also become strong, the West Pacific subtropical high becomes weak in the middle troposphere. The meridional circulation in middle high latitude in East Asia is evident. East Asian winter monsoon is strong in case of La Ni〖AKn~D〗a events, the winter temperature in most regions of China including South China is lower than that in normal years, and vice versa. There are significant interdecadal differences of the effect of El Ni〖AKn~D〗o event on the winter temperature in South China. SST variation obviously corresponding to interdecadal variation of the winter temperature in South China is found in North Pacific, and the relationship between the variation and ENSO is not obvious.
2014, 40(10):1240-1247.
DOI: 10.7519/j.issn.1000-0526.2014.10.008
Abstract:
The 10 m wind from QuikSCAT and ASCAT orbital data were compared with buoy wind data in the northern South China Sea. The results show that the two satellite data have a good applicability in the northern South China Sea. The QuikSCAT inversion wind speed is 0.46 m·s-1 higher than the buoy wind and ASCAT inversion wind speed is 0.45 m·s-1 higher than buoy wind speed in the offshore sea, though it is 0.07 m·s-1 in the open sea. The absolute error ＜30° of QuikSCAT satellite inversion wind exceeds 50％.The absolute error ＜30° of ASCAT satellite inversion wind passes 56％ in the offshore sea and gets to 64％ in the open sea. When the wind speed is small, satellite inversion wind speed is bigger, when the wind speed is fast, satellite wind speed is slower than the buoy wind. The error in the morning is bigger than that in the evening. But under the condition of 5-10 m·s-1 wind speed, the consistency of the two satellite wind data is better. The offshore wind power resource simulated by WRF model is perhaps overrated. Satellite data may be a beneficial supplement for assessing offshore wind power resource. The satellite inversion wind error analysis also provides a reference for the data assimilation of satellite inversion wind field.
The 10 m wind from QuikSCAT and ASCAT orbital data were compared with buoy wind data in the northern South China Sea. The results show that the two satellite data have a good applicability in the northern South China Sea. The QuikSCAT inversion wind speed is 0.46 m·s-1 higher than the buoy wind and ASCAT inversion wind speed is 0.45 m·s-1 higher than buoy wind speed in the offshore sea, though it is 0.07 m·s-1 in the open sea. The absolute error ＜30° of QuikSCAT satellite inversion wind exceeds 50％.The absolute error ＜30° of ASCAT satellite inversion wind passes 56％ in the offshore sea and gets to 64％ in the open sea. When the wind speed is small, satellite inversion wind speed is bigger, when the wind speed is fast, satellite wind speed is slower than the buoy wind. The error in the morning is bigger than that in the evening. But under the condition of 5-10 m·s-1 wind speed, the consistency of the two satellite wind data is better. The offshore wind power resource simulated by WRF model is perhaps overrated. Satellite data may be a beneficial supplement for assessing offshore wind power resource. The satellite inversion wind error analysis also provides a reference for the data assimilation of satellite inversion wind field.
2014, 40(10):1247-1258.
DOI: 10.7519/j.issn.1000-0526.2014.10.009
Abstract:
A nowcasting method based on blending Doppler weather radar data and mesoscale numerical weather prediction (NWP) model products is presented. The method is as follows: Firstly, by using correlation analysis, position errors are calculated between radar precipitation estimate and precipitation estimated from reflectivity factor from the output of NWP model in this same time, and thus displacement deviation vectors fields are obtained. Then, displacement deviation vector fields are partitioned with human computer interaction and each deviation vector field gets smoothed, so the average displacement deviation vector of each partition is obtained. Finally, the trend variation characteristic of average displacement deviation vector of each partition with time is established by using least square method to linearly fit the continuous time multiple average displacement deviation vectors for each partition, and according to the trend, spatial position deviation of precipitation estimated from reflectivity factor from the output of NWP model is corrected in the future periods. The method was once applied to three severe prceipitation cases in the summers of 2012 and 2013 that happened in the west of Chongqing and the east of Sichuan. The nowcasting verification results show that for the 0-2 h nowcasting, the performance of blending forecasts is generally superior to model forecasts. Compared with quantitative precipitation forecast (QPF) of radar based extrapolation, the performance of radar based extrapolation QPF is superior to blending forecasts in the first hour but the performance of blending forecasts is superior to radar based extrapolation QPF in the second hour.
A nowcasting method based on blending Doppler weather radar data and mesoscale numerical weather prediction (NWP) model products is presented. The method is as follows: Firstly, by using correlation analysis, position errors are calculated between radar precipitation estimate and precipitation estimated from reflectivity factor from the output of NWP model in this same time, and thus displacement deviation vectors fields are obtained. Then, displacement deviation vector fields are partitioned with human computer interaction and each deviation vector field gets smoothed, so the average displacement deviation vector of each partition is obtained. Finally, the trend variation characteristic of average displacement deviation vector of each partition with time is established by using least square method to linearly fit the continuous time multiple average displacement deviation vectors for each partition, and according to the trend, spatial position deviation of precipitation estimated from reflectivity factor from the output of NWP model is corrected in the future periods. The method was once applied to three severe prceipitation cases in the summers of 2012 and 2013 that happened in the west of Chongqing and the east of Sichuan. The nowcasting verification results show that for the 0-2 h nowcasting, the performance of blending forecasts is generally superior to model forecasts. Compared with quantitative precipitation forecast (QPF) of radar based extrapolation, the performance of radar based extrapolation QPF is superior to blending forecasts in the first hour but the performance of blending forecasts is superior to radar based extrapolation QPF in the second hour.
2014, 40(10):1259-1265.
DOI: 10.7519/j.issn.1000-0526.2014.10.010
Abstract:
The macro and micro structures of the weather process in which surface rain turns into snow are analyzed in this paper by using the data obtained from wind profile radar on 3 November 2012 in Yanqing of Beijing. The results show that the products of intensity and velocity field of wind profile radar are good for diagnosing and distinguishing the evolution of precipitation phase change from rainfall into snowfall. Features of reflectivity, signal to noise ratio (SNR), spectral width and other factors are discontinuous before raining, bright band appears in the 800-1000 m height when surface rainfall is seen, but with bright band disappearing, rainfall turns into snow. In the surface rainfall stage, the figure of the echo intensity spectra has a clear hierarchical structure, showing solid particles above 1300 m height and liquid below 700 m height, respectively. So, close relations are found between stratification height and temperature. Generally, there is a melting layer with temperature of 274-275 K, and with the most significant change of echo intensity spectra. In addition, statistics of radial velocity and SNR of the stratus precipitation in the recent 3 years show that, radial velocity ranges within 3-6 m·s-1 and SNR is in 15-25 dB when raining; but in the process of snowing they are 0-1.5 m·s-1 and 3-15 dB respectively.
The macro and micro structures of the weather process in which surface rain turns into snow are analyzed in this paper by using the data obtained from wind profile radar on 3 November 2012 in Yanqing of Beijing. The results show that the products of intensity and velocity field of wind profile radar are good for diagnosing and distinguishing the evolution of precipitation phase change from rainfall into snowfall. Features of reflectivity, signal to noise ratio (SNR), spectral width and other factors are discontinuous before raining, bright band appears in the 800-1000 m height when surface rainfall is seen, but with bright band disappearing, rainfall turns into snow. In the surface rainfall stage, the figure of the echo intensity spectra has a clear hierarchical structure, showing solid particles above 1300 m height and liquid below 700 m height, respectively. So, close relations are found between stratification height and temperature. Generally, there is a melting layer with temperature of 274-275 K, and with the most significant change of echo intensity spectra. In addition, statistics of radial velocity and SNR of the stratus precipitation in the recent 3 years show that, radial velocity ranges within 3-6 m·s-1 and SNR is in 15-25 dB when raining; but in the process of snowing they are 0-1.5 m·s-1 and 3-15 dB respectively.
2014, 40(10):1266-1270.
DOI: 10.7519/j.issn.1000-0526.2014.10.011
Abstract:
Spatial positioning error causes false echoes and affects the reliability of radar observation data, resulting in interference on forecasts directly. Our project team acquired 17 cases from the nationwide CINRAD/SA radar stations. Combining with flow direction of antenna servo system signal and parameter characteristics of key components, this paper gradually analyzes the factors conducing spatial positioning error and summarizes the method of diagnosing such problems. Finally, three representative cases are analyzed, which provides guidance for removing such malfunction quickly.
Spatial positioning error causes false echoes and affects the reliability of radar observation data, resulting in interference on forecasts directly. Our project team acquired 17 cases from the nationwide CINRAD/SA radar stations. Combining with flow direction of antenna servo system signal and parameter characteristics of key components, this paper gradually analyzes the factors conducing spatial positioning error and summarizes the method of diagnosing such problems. Finally, three representative cases are analyzed, which provides guidance for removing such malfunction quickly.
2014, 40(10):1271-1278.
DOI: 10.7519/j.issn.1000-0526.2014.10.012
Abstract:
Through statistics and analysis of 40 precipitation processes （≥5 mm） from 1975 to 2004 in Dalian, four kinds of main precipitation weather situation were summarized in the paper, including large trough style, middle latitude system style, north vortex style and south vortex style. At the same time, 22 Doppler radar samples of rainfall processes (≥5 mm) from June to October, 2003 were analyzed. It is summed up that the main precipitation clouds in Dalian are stratus cloud and stratocumulus cloud, and the stratocumulus cloud is more than the stratus cloud, which indicates that the method of rocket rain enhancement operation is more suitable in Dalian. Then the radar operation warning and decision criterion index model is set up and the method is discussed to determine the operation target area by natural rainfall area and social water requirement analysis. According to the weight analysis of radar warning decision index, the paper focuses on the study of the vehicle second scheduling schemes and work flows, which can be a scientific and efficient guarantee for rocket precipitation enhancement operations.
Through statistics and analysis of 40 precipitation processes （≥5 mm） from 1975 to 2004 in Dalian, four kinds of main precipitation weather situation were summarized in the paper, including large trough style, middle latitude system style, north vortex style and south vortex style. At the same time, 22 Doppler radar samples of rainfall processes (≥5 mm) from June to October, 2003 were analyzed. It is summed up that the main precipitation clouds in Dalian are stratus cloud and stratocumulus cloud, and the stratocumulus cloud is more than the stratus cloud, which indicates that the method of rocket rain enhancement operation is more suitable in Dalian. Then the radar operation warning and decision criterion index model is set up and the method is discussed to determine the operation target area by natural rainfall area and social water requirement analysis. According to the weight analysis of radar warning decision index, the paper focuses on the study of the vehicle second scheduling schemes and work flows, which can be a scientific and efficient guarantee for rocket precipitation enhancement operations.
2014, 40(10):1279-1285.
DOI: 10.7519/j.issn.1000-0526.2014.10.013
Abstract:
During the spring of 2014, the air temperature over most China was above normal and tied for the second highest with the spring of 2013 during the corresponding period in history since 1961. The mean precipitation over China was slightly above normal, with significantly more precipitation over the Northeast China. Analysis shows that more precipitation in Northeast China occurred during 2-28 May, which was mainly caused by the active Northeast cold vortex (NECV). The NECV led to more cold air activities and also brought abundant water vapor from the Sea of Japan to Northeast China. Meanwhile, the intensified western Pacific subtropical high (WPSH), whose high ridge extended more westward, also brought more moisture from the western Pacific to Northeast China. In 2014, the South China Sea summer monsoon broke out on the 2 pentad of June, about 3 pentads later than normal, becoming one of the latest summer monsoons in history. The persistently strong and westward WPSH from late April to the end of May directly resulted in the later monsoon onset. Further analysis suggested that the strong and westward WPSH was possibly caused by the rapid warming over the tropical Indian Ocean.
During the spring of 2014, the air temperature over most China was above normal and tied for the second highest with the spring of 2013 during the corresponding period in history since 1961. The mean precipitation over China was slightly above normal, with significantly more precipitation over the Northeast China. Analysis shows that more precipitation in Northeast China occurred during 2-28 May, which was mainly caused by the active Northeast cold vortex (NECV). The NECV led to more cold air activities and also brought abundant water vapor from the Sea of Japan to Northeast China. Meanwhile, the intensified western Pacific subtropical high (WPSH), whose high ridge extended more westward, also brought more moisture from the western Pacific to Northeast China. In 2014, the South China Sea summer monsoon broke out on the 2 pentad of June, about 3 pentads later than normal, becoming one of the latest summer monsoons in history. The persistently strong and westward WPSH from late April to the end of May directly resulted in the later monsoon onset. Further analysis suggested that the strong and westward WPSH was possibly caused by the rapid warming over the tropical Indian Ocean.
2014, 40(10):1286-1292.
DOI: 10.7519/j.issn.1000-0526.2014.10.014
Abstract:
The main characteristics of the general atmospheric circulation in July 2014 are listed as follows: there is one polar vortex center in the Northern Hemisphere. In the mid high latitudes, the circulation presents a five wave pattern among which the troughs near Balkhash Lake and in the East Asia are stronger than their climatological mean. The subtropical high shows the distribution of east west belt and its intensity is equivalent to its average state during the corresponding time of the normal years. Meanwhile, monthly mean precipitation amount is 115.0 mm, which is 4.6% less than its climatological mean (120.6 mm). Monthly mean temperature is 22.3℃, higher than its climatological mean (21.9℃). There are 8 severe rainfall events with extreme precipitation records observed at some stations in China. Five tropical cyclones are active over the northwestern Pacific Ocean and the South China Sea, and two of them land China. Long lasting high temperature events occur in South China and Yangtze River region while extreme high temperature events happen at 87 stations and extreme heavy rainfall events at 74 stations in China.
The main characteristics of the general atmospheric circulation in July 2014 are listed as follows: there is one polar vortex center in the Northern Hemisphere. In the mid high latitudes, the circulation presents a five wave pattern among which the troughs near Balkhash Lake and in the East Asia are stronger than their climatological mean. The subtropical high shows the distribution of east west belt and its intensity is equivalent to its average state during the corresponding time of the normal years. Meanwhile, monthly mean precipitation amount is 115.0 mm, which is 4.6% less than its climatological mean (120.6 mm). Monthly mean temperature is 22.3℃, higher than its climatological mean (21.9℃). There are 8 severe rainfall events with extreme precipitation records observed at some stations in China. Five tropical cyclones are active over the northwestern Pacific Ocean and the South China Sea, and two of them land China. Long lasting high temperature events occur in South China and Yangtze River region while extreme high temperature events happen at 87 stations and extreme heavy rainfall events at 74 stations in China.
Mobile website
® 2024 All Rights Reserved
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
ISSN:1000-0526 CN:11-2282/P