Volume 47,Issue 1,2019 Table of Contents
2019, 47(1):1-9.
Abstract:
Soil moisture plays an important role in studying engineering, agronomic, geological, ecological, biological and hydrological characteristics of the soil mass. Currently, the applicability of soil moisture measurement techniques to the soils of entirely different characteristics and types of moisture content is still a point of debate, no matter where the measurement conducts, either in laboratory or in situ conditions. The advantages and disadvantages of the established and emerging soil moisture measurement techniques are discussed.The limitations and the influences of various soilspecific parameters on the measured soil moisture content are reviewed. Meanwhile, in the meteorological department of China, based on the technique of Frequency Domain Reflectometry, three models, including DZN1, DZN2 and DZN3, are developed. From the beginning of 2009, in the automatic meteorological observation operation of soil moisture in China, the devices performed stablely, and the measurement accuracy and data quality can meet the needs of operation and service. With respect to automatic observation operation in China, this paper provides some reference proposals for operational construction and accurate measurement.
Soil moisture plays an important role in studying engineering, agronomic, geological, ecological, biological and hydrological characteristics of the soil mass. Currently, the applicability of soil moisture measurement techniques to the soils of entirely different characteristics and types of moisture content is still a point of debate, no matter where the measurement conducts, either in laboratory or in situ conditions. The advantages and disadvantages of the established and emerging soil moisture measurement techniques are discussed.The limitations and the influences of various soilspecific parameters on the measured soil moisture content are reviewed. Meanwhile, in the meteorological department of China, based on the technique of Frequency Domain Reflectometry, three models, including DZN1, DZN2 and DZN3, are developed. From the beginning of 2009, in the automatic meteorological observation operation of soil moisture in China, the devices performed stablely, and the measurement accuracy and data quality can meet the needs of operation and service. With respect to automatic observation operation in China, this paper provides some reference proposals for operational construction and accurate measurement.
2019, 47(1):10-18.
Abstract:
Based on data from the polarimetric radar built jointly by the Zhuhai and Macau meteorological service, the performance of two differential reflectivity calibration methods (vertical incident calibration and solar calibration) is analyzed. Using the meteorological echoes （light rainfall and dry snow） as objects during the operational volume scan，the calibration results are verified, and the sources of calibration errors are revealed. The research indicates that, the solar calibration is quite accurate in calibrating the receiving channels of the radar. After the correction of the system differential phase, the reliable and stable differential reflectivity bias of the radar system can be estimated by implying the strict constraints on the differential phase, reflectivity, SNR, and correlation coefficient when filtering the light rain and dry snow. The biases estimated by light rainfall and dry snow are consistent with that by the solar calibration and show a longterm stability during a period of more than two months. Therefore, it can be concluded that light rain and dry snow calibration is suitable for the online monitoring of the differential reflectivity bias. The verification also suggests that the results of vertical incident calibration deviate from the true significantly. Comparing with vertical incident calibrations of Cband radar in Thurnham of UK and the Nanjing University of China, it is considered that the vertical incident calibration of the ZhuhaiMacau radar is biased by the aviation obstruction light and its maintaining window placed at the top of the radome.
Based on data from the polarimetric radar built jointly by the Zhuhai and Macau meteorological service, the performance of two differential reflectivity calibration methods (vertical incident calibration and solar calibration) is analyzed. Using the meteorological echoes （light rainfall and dry snow） as objects during the operational volume scan，the calibration results are verified, and the sources of calibration errors are revealed. The research indicates that, the solar calibration is quite accurate in calibrating the receiving channels of the radar. After the correction of the system differential phase, the reliable and stable differential reflectivity bias of the radar system can be estimated by implying the strict constraints on the differential phase, reflectivity, SNR, and correlation coefficient when filtering the light rain and dry snow. The biases estimated by light rainfall and dry snow are consistent with that by the solar calibration and show a longterm stability during a period of more than two months. Therefore, it can be concluded that light rain and dry snow calibration is suitable for the online monitoring of the differential reflectivity bias. The verification also suggests that the results of vertical incident calibration deviate from the true significantly. Comparing with vertical incident calibrations of Cband radar in Thurnham of UK and the Nanjing University of China, it is considered that the vertical incident calibration of the ZhuhaiMacau radar is biased by the aviation obstruction light and its maintaining window placed at the top of the radome.
2019, 47(1):19-28.
Abstract:
Based on the 6year observation data of the Nanjiao Sband radar in Beijing, the statistical characteristics of radar echoes and their spatial distribution are analyzed. The methods for identifying and correcting the clutter echoes and beam blocking by the statistical results are studied. The results show: (1) The climate characteristics of radar echo intensity probability is a good factor in identifying clutter echoes, and it is also very useful in identifying the radar beam blocking area and degree. Clutter echoes of Beijing are mainly located near the radar center and the piedmont areas of the western Beijing and northwestern Beijing. The radar beam blocking areas are mainly concentrated in the southeast because of the tall buildings and the northwest because of the topography. (2) Using the average vertical profile method with a changeable area, the high elevation echoes can be used to correct lowelevation clutter echoes, which can effectively correct the clutter echoes, and retain the local scale characteristics of echoes. The echo fillin of the beam blocking area is also made by this method, which can keep the continuity between the upper and lowerlevel elevation echoes. (3) The supported method of identifying clutter echoes and beam blocking can reflect the real situation of the local radar, being independent of prior knowledge. Compared with traditional ways, this method is more simple, reusable, and suitable for local weather.
Based on the 6year observation data of the Nanjiao Sband radar in Beijing, the statistical characteristics of radar echoes and their spatial distribution are analyzed. The methods for identifying and correcting the clutter echoes and beam blocking by the statistical results are studied. The results show: (1) The climate characteristics of radar echo intensity probability is a good factor in identifying clutter echoes, and it is also very useful in identifying the radar beam blocking area and degree. Clutter echoes of Beijing are mainly located near the radar center and the piedmont areas of the western Beijing and northwestern Beijing. The radar beam blocking areas are mainly concentrated in the southeast because of the tall buildings and the northwest because of the topography. (2) Using the average vertical profile method with a changeable area, the high elevation echoes can be used to correct lowelevation clutter echoes, which can effectively correct the clutter echoes, and retain the local scale characteristics of echoes. The echo fillin of the beam blocking area is also made by this method, which can keep the continuity between the upper and lowerlevel elevation echoes. (3) The supported method of identifying clutter echoes and beam blocking can reflect the real situation of the local radar, being independent of prior knowledge. Compared with traditional ways, this method is more simple, reusable, and suitable for local weather.
2019, 47(1):29-34.
Abstract:
Based on the nighttime traffic monitoring images, the observation visibility data of nearby automatic stations are chosen as the criteria for whether the image is foggy. The effects of foggy and fogfree environments on light sources, and their imaging are analyzed; and the corresponding features are extracted. A recognition model is established to identify fogs by the method of the support vector machine. Results show that, due to the increase of air extinction coefficient in the presence of fogs, the light from LED electronic display or cars and their reflection in the monitoring image weaken. The image gradient, texture and other parameters are obviously different in foggy and clear weather. The critical success index of the model evaluation result is 0.74, and the false alarm rate is 0.18, which meet the needs of fog monitoring at night.
Based on the nighttime traffic monitoring images, the observation visibility data of nearby automatic stations are chosen as the criteria for whether the image is foggy. The effects of foggy and fogfree environments on light sources, and their imaging are analyzed; and the corresponding features are extracted. A recognition model is established to identify fogs by the method of the support vector machine. Results show that, due to the increase of air extinction coefficient in the presence of fogs, the light from LED electronic display or cars and their reflection in the monitoring image weaken. The image gradient, texture and other parameters are obviously different in foggy and clear weather. The critical success index of the model evaluation result is 0.74, and the false alarm rate is 0.18, which meet the needs of fog monitoring at night.
2019, 47(1):35-40.
Abstract:
Aiming at the problem of longtime consuming and inconvenient maintenance of traditional rainfall measurement, based on the analysis of acoustic signal recognition technology, this paper proposes a rainfall measurement method based on sound recognition to simulate the nonlinearity of frequency domain demarcation and the mechanism of superimposing acoustic signals in the same frequency group in human ears. The Fourier transformed energy spectrum is passed through a Mel filter, and then the MelFrequency Cepstral Coefficients of the rain sounds are extracted as the eigenvector of rain sound signals. On this basis, a threelayer BP neural network is constructed, and the normalized sample data are used for neural network training. Finally, the test samples are used to identify the rainfall. Experimental results show that neural network can effectively identify the amount of rainfall on the basis of a small amount of sample training, which provides a theoretical basis for the application of acoustic signal recognition technology for more accurate rainfall measurement.
Aiming at the problem of longtime consuming and inconvenient maintenance of traditional rainfall measurement, based on the analysis of acoustic signal recognition technology, this paper proposes a rainfall measurement method based on sound recognition to simulate the nonlinearity of frequency domain demarcation and the mechanism of superimposing acoustic signals in the same frequency group in human ears. The Fourier transformed energy spectrum is passed through a Mel filter, and then the MelFrequency Cepstral Coefficients of the rain sounds are extracted as the eigenvector of rain sound signals. On this basis, a threelayer BP neural network is constructed, and the normalized sample data are used for neural network training. Finally, the test samples are used to identify the rainfall. Experimental results show that neural network can effectively identify the amount of rainfall on the basis of a small amount of sample training, which provides a theoretical basis for the application of acoustic signal recognition technology for more accurate rainfall measurement.
2019, 47(1):41-51.
Abstract:
With the development of urbanization, the greater number of cities are built near mountains or valleys. Various characteristics of mountainvalley breezes are shown in different places due to geographical locations and meteorological conditions. Mountainvalley breezes play an important role in local wind regimes and climatic features, and are also related to the evolution of inversion and pollutant concentration. Based on the observation analysis, theory and numerical simulation, the main methods of studying mountainvalley breezes, this study focuses on the achievements of mountainvalley breeze researches in China. The interactions with other mesoscale circulations (landsea breeze, landlake breeze, urban heat island, vegetation breeze, glacier wind circulation) are discussed. Impacts of mountain circulation including mountainvalley breeze on atmospheric pollution are also reviewed. At last, the paper concludes with an outline of mountainvalley breeze researches in China and rises some open questions that need to be further studied and discussed.
With the development of urbanization, the greater number of cities are built near mountains or valleys. Various characteristics of mountainvalley breezes are shown in different places due to geographical locations and meteorological conditions. Mountainvalley breezes play an important role in local wind regimes and climatic features, and are also related to the evolution of inversion and pollutant concentration. Based on the observation analysis, theory and numerical simulation, the main methods of studying mountainvalley breezes, this study focuses on the achievements of mountainvalley breeze researches in China. The interactions with other mesoscale circulations (landsea breeze, landlake breeze, urban heat island, vegetation breeze, glacier wind circulation) are discussed. Impacts of mountain circulation including mountainvalley breeze on atmospheric pollution are also reviewed. At last, the paper concludes with an outline of mountainvalley breeze researches in China and rises some open questions that need to be further studied and discussed.
2019, 47(1):52-61.
Abstract:
Urban heat island circulation is a local circulation which is caused by urban heat islands in the urban boundary layer. It can affect the diffusion of pollutants in urban areas and urban precipitation, so it is the key of urban meteorology researches. In order to carry out the related researches more effectively in the future, the observation analyses and numerical simulations of urban breeze circulation in China over the past 30 years are overviewed in this paper, including the temporal and spatial characteristics, trigger mechanisms and its interaction with other local circulations. Besides, the influence of urban breeze circulation on the horizontal and vertical distribution of pollutants is summarized.
Urban heat island circulation is a local circulation which is caused by urban heat islands in the urban boundary layer. It can affect the diffusion of pollutants in urban areas and urban precipitation, so it is the key of urban meteorology researches. In order to carry out the related researches more effectively in the future, the observation analyses and numerical simulations of urban breeze circulation in China over the past 30 years are overviewed in this paper, including the temporal and spatial characteristics, trigger mechanisms and its interaction with other local circulations. Besides, the influence of urban breeze circulation on the horizontal and vertical distribution of pollutants is summarized.
8 Relationship between East Asian Summer Monsoon Anomaly and Summer Precipitation in Huanghuai Region
2019, 47(1):62-69.
Abstract:
In this paper, the most suitable summer monsoon index is selected to determine the summer monsoon year in the Huanghuai region. Combining with the summer daily precipitation data in recent 55 years, the difference of summer rainfall between strong and weak years and the formation causes are discussed. The main conclusions are as follows： In the strong summer monsoon year, the precipitation in the east is more than that in the west, and in the weak summer monsoon year, on the contrary. Before 1979, the precipitation in the region had a cyclic interannual variation with the periods being 3 to 5 years, but after 1979, the period evolved to 15 years. At the same time, the regional precipitation was characterized by low frequency oscillation. In the strong summer monsoon years, there were 7 to 14day oscillations and two rainy seasons which occurred in early July and late August, respectively; in the weak summer monsoon years, the low frequency oscillations of 10 to 18 day and 25 to 30 days were remarkable, but the main rainy season was not obvious, and precipitation was less. The differences of annual precipitation between strong and weak summer monsoon years are mainly attributed to the different wave trains of the largescale circulation background in the midhigh latitudes of the Eurasia and the difference of water vapor transport in the southerly monsoon. The spring SST anomaly can indicate the precipitation in the Huanghuai region. In La Nina years, the precipitation in the eastern part of the Huanghuai area was more than that in the western part, and in the El Nino years, on the contrary.
In this paper, the most suitable summer monsoon index is selected to determine the summer monsoon year in the Huanghuai region. Combining with the summer daily precipitation data in recent 55 years, the difference of summer rainfall between strong and weak years and the formation causes are discussed. The main conclusions are as follows： In the strong summer monsoon year, the precipitation in the east is more than that in the west, and in the weak summer monsoon year, on the contrary. Before 1979, the precipitation in the region had a cyclic interannual variation with the periods being 3 to 5 years, but after 1979, the period evolved to 15 years. At the same time, the regional precipitation was characterized by low frequency oscillation. In the strong summer monsoon years, there were 7 to 14day oscillations and two rainy seasons which occurred in early July and late August, respectively; in the weak summer monsoon years, the low frequency oscillations of 10 to 18 day and 25 to 30 days were remarkable, but the main rainy season was not obvious, and precipitation was less. The differences of annual precipitation between strong and weak summer monsoon years are mainly attributed to the different wave trains of the largescale circulation background in the midhigh latitudes of the Eurasia and the difference of water vapor transport in the southerly monsoon. The spring SST anomaly can indicate the precipitation in the Huanghuai region. In La Nina years, the precipitation in the eastern part of the Huanghuai area was more than that in the western part, and in the El Nino years, on the contrary.
2019, 47(1):70-78.
Abstract:
The genesis and dissipation mechanisms of three radiationadvection fog events in Chengdu of December 2016 are analyzed, using the data from wind profile radar, microwave radiometers, automatic weather stations, secondlevel sounding data and NCEP/NCAR reanalysis data (1°×1°). The results indicate: (1) the northwest airstream at 500 hPa, maintenance of dry layer at 700 hPa and weak wind below 1.5 km height were beneficial to the rapid radiation cooling near the ground, forming the inversion layer and offering thermal conditions for the formation of the fog. (2) No movement or less movement in vertical direction offered dynamic conditions for the formation and development of fogs. The convergence caused by weak southwest warm and moist air (≤4 m/s) near the ground in Chengdu provided ample water vapor conditions for the formation of the strong fogs. (3) The coexistence of surface inversion layer and dewpoint inverse layer (lower than the height of the inversion layer) better indicates the occurrence of the fogs. (4) In the afternoon, double inversion layers and weak winds near the surface were important reasons for the maintenance of radiationadvection fogs. (5) After the southwest warm and moist air disappeared or water vapor convergence removed out of Chengdu, the disappearance of the nearsurface inversion layer or entrainment of dry air at the top of fogs is the cause of the final disappearance of the radiation advection fogs.
The genesis and dissipation mechanisms of three radiationadvection fog events in Chengdu of December 2016 are analyzed, using the data from wind profile radar, microwave radiometers, automatic weather stations, secondlevel sounding data and NCEP/NCAR reanalysis data (1°×1°). The results indicate: (1) the northwest airstream at 500 hPa, maintenance of dry layer at 700 hPa and weak wind below 1.5 km height were beneficial to the rapid radiation cooling near the ground, forming the inversion layer and offering thermal conditions for the formation of the fog. (2) No movement or less movement in vertical direction offered dynamic conditions for the formation and development of fogs. The convergence caused by weak southwest warm and moist air (≤4 m/s) near the ground in Chengdu provided ample water vapor conditions for the formation of the strong fogs. (3) The coexistence of surface inversion layer and dewpoint inverse layer (lower than the height of the inversion layer) better indicates the occurrence of the fogs. (4) In the afternoon, double inversion layers and weak winds near the surface were important reasons for the maintenance of radiationadvection fogs. (5) After the southwest warm and moist air disappeared or water vapor convergence removed out of Chengdu, the disappearance of the nearsurface inversion layer or entrainment of dry air at the top of fogs is the cause of the final disappearance of the radiation advection fogs.
2019, 47(1):79-88.
Abstract:
The precipitation caused by Typhoon Megi is abnormally enormous with the rainfall in part counties in Wenzhou and Lishui breaking the historical records, which caused a severe disaster. Its causes are analyzed by the use of NCEP 0.5°×0.5° reanalysis data, FY2G satellite data, Doppler radar data, the intensive observation data, and so on. The results show that there were three low jet streams: the southeast jet stream between Megi and subtropical high, the eastward jet stream between Megi and Huabei high, and the southwest jet stream connected with southwest monsoon. The shear and convergence zone consisted of three low jet streams was the area of vapor and instability energy convergence and also the trigger zone of mesoscale convection. The extreme precipitation in Wenzhou and Lishui was triggered by the strong development of continual mesoscale convection. Longtime lowlevel jet streams, particularly abundant vapor transportation and cold air are the main influencing mechanism of Megi extreme precipitation. During the cold air influencing, the precipitation echo with tight structure developed strongly. The echo intensity and precipitation efficiency were obviously stronger than those of the typhoon circulation echo with no cold air influence. The cloudtop blackbody brightness temperature (TBB) has good relationship with typhoon precipitation, which has reference value for operational forecasting.
The precipitation caused by Typhoon Megi is abnormally enormous with the rainfall in part counties in Wenzhou and Lishui breaking the historical records, which caused a severe disaster. Its causes are analyzed by the use of NCEP 0.5°×0.5° reanalysis data, FY2G satellite data, Doppler radar data, the intensive observation data, and so on. The results show that there were three low jet streams: the southeast jet stream between Megi and subtropical high, the eastward jet stream between Megi and Huabei high, and the southwest jet stream connected with southwest monsoon. The shear and convergence zone consisted of three low jet streams was the area of vapor and instability energy convergence and also the trigger zone of mesoscale convection. The extreme precipitation in Wenzhou and Lishui was triggered by the strong development of continual mesoscale convection. Longtime lowlevel jet streams, particularly abundant vapor transportation and cold air are the main influencing mechanism of Megi extreme precipitation. During the cold air influencing, the precipitation echo with tight structure developed strongly. The echo intensity and precipitation efficiency were obviously stronger than those of the typhoon circulation echo with no cold air influence. The cloudtop blackbody brightness temperature (TBB) has good relationship with typhoon precipitation, which has reference value for operational forecasting.
2019, 47(1):89-97.
Abstract:
A microburst process on 12 July 2017 near Ningbo Airport is simulated by the mesoscale numerical model WRFV3.6 and its formation mechanism is analyzed using the data of automatic meteorological stations over Zhejiang Province, automatic observation data collected at the airport and Doppler radar data. The study shows that the microburst was triggered by a strong thunderstorm which was caused by a sea breeze front. The changes of wind, temperature, pressure of the AWOS observation data show the obvious characteristics of microburst. The horizontal wind field structure of the microburst is simulated well in the simulation test. Dragging effect, hail melting during subsidence, continuous evaporation, and cooling of liquid water and rainwater are important reasons for the formation of the microburst. Lowlevel temperature disturbance enhanced vertical motion, and the abnormal increase area of the middle and lowlevel vortex has a good correspondence with the thunderstorm heavy rainfall area.
A microburst process on 12 July 2017 near Ningbo Airport is simulated by the mesoscale numerical model WRFV3.6 and its formation mechanism is analyzed using the data of automatic meteorological stations over Zhejiang Province, automatic observation data collected at the airport and Doppler radar data. The study shows that the microburst was triggered by a strong thunderstorm which was caused by a sea breeze front. The changes of wind, temperature, pressure of the AWOS observation data show the obvious characteristics of microburst. The horizontal wind field structure of the microburst is simulated well in the simulation test. Dragging effect, hail melting during subsidence, continuous evaporation, and cooling of liquid water and rainwater are important reasons for the formation of the microburst. Lowlevel temperature disturbance enhanced vertical motion, and the abnormal increase area of the middle and lowlevel vortex has a good correspondence with the thunderstorm heavy rainfall area.
2019, 47(1):98-105.
Abstract:
Based on the conventional meteorological data, observation data of the Tianjin Observation Tower, radar data, VDRAS data (Variation Doppler Radar Analysis System), and NCEP reanalysis data (ECWMF and National Centre of Environmental Prediction), the causes of the first snow weather process on 20 and 21 November 2016 in Tianjin are analyzed. The results show: the mixed rainsnow storm was produced in the interaction of the upper trough and returnflow cold air; the main sources of water vapor were the southwest warm and humid airflow in front of the trough in the middle and lower troposphere and the returning east winds. The returning east wind absorbed moisture when it passed through the low surface of the Bohai Sea and became wet and cold; the dynamic condition was mainly from the dynamic lifting of the cold return flow, the thickness of the returning easterly increased from 1.5 km to 2 km during precipitation. The nongeostrophic secondary circulation transported the returning water vapor upwards into a source for precipitation, and strengthened the vertical ascending motion of the warm and humid air to provide dynamic conditions. The north wind component wind speed and thickness of the cold air increased sharply. Simultaneously, the conversion of highaltitude cloud water particles to cloud ice particles and the reflow of cold air at the boundary layer were indispensable for the transformation from rain to snow, and the uniform temperature layer and cloud ice particles of 800 to 950 hPa increased greatly and extended to low altitudes. The variation characteristics of the potential thickness of 700 to 850 and 850 to 1000 hPa had good indication value for the discrimination of rain and snow phases.
Based on the conventional meteorological data, observation data of the Tianjin Observation Tower, radar data, VDRAS data (Variation Doppler Radar Analysis System), and NCEP reanalysis data (ECWMF and National Centre of Environmental Prediction), the causes of the first snow weather process on 20 and 21 November 2016 in Tianjin are analyzed. The results show: the mixed rainsnow storm was produced in the interaction of the upper trough and returnflow cold air; the main sources of water vapor were the southwest warm and humid airflow in front of the trough in the middle and lower troposphere and the returning east winds. The returning east wind absorbed moisture when it passed through the low surface of the Bohai Sea and became wet and cold; the dynamic condition was mainly from the dynamic lifting of the cold return flow, the thickness of the returning easterly increased from 1.5 km to 2 km during precipitation. The nongeostrophic secondary circulation transported the returning water vapor upwards into a source for precipitation, and strengthened the vertical ascending motion of the warm and humid air to provide dynamic conditions. The north wind component wind speed and thickness of the cold air increased sharply. Simultaneously, the conversion of highaltitude cloud water particles to cloud ice particles and the reflow of cold air at the boundary layer were indispensable for the transformation from rain to snow, and the uniform temperature layer and cloud ice particles of 800 to 950 hPa increased greatly and extended to low altitudes. The variation characteristics of the potential thickness of 700 to 850 and 850 to 1000 hPa had good indication value for the discrimination of rain and snow phases.
2019, 47(1):106-115.
Abstract:
Based on the routine observations and NCEP reanalysis data (4 times a day), the circulation background, the characteristics of cold air activity, dynamical and water vapor conditions, especially the features of precipitation phase state, and the vertical structure of atmospheric temperature using wetbulb temperature (WBT) are analyzed for the rare cryogenic freezing rain and snow event over Guangdong province in late January 2016. The results show that the primary reason of temperature sudden drop in the north and centralsouth parts of Guangdong Province during this cold wave event is that strong cold air outbroke when the transverse trough swinged southward and the severe cold air moved southward with abnormally strong cold high, frontal zone, cold temperature center and advection in the atmospheric circulation pattern of the transverse trough turning into vertical. The favorable dynamical conditions for the convergence of warm and cold air at 700 hPa and water vapor conditions for the convergence in South China of southwesterly of 700 hPa carrying water vapor from the Bay of Bengal across the north of the IndoChina Peninsula and Beibu Gulf resulted in this weather process. The precipitation phase state was closely related to the intensity of the warm layer (temperature above 0 ℃) and WBT under the favorable circulation, dynamical and water vapor conditions. The warm layer weakened significantly and the subfreezing layer with WBT below 0 ℃ underneath strengthened, leading to the transition of precipitation phase state from rain to solidstate, i.e. snow, sleet and graupel. When the solidstate precipitation appeared, there was no melting effect because of the WBT below 0 ℃ in the middle and lower atmosphere; thus snow or sleet was more likely to be present in the north of Guangdong Province, whereas sleet or graupel was mainly present in the Pearl River Delta, which locates further south due to the existence of a weak warm layer. Therefore, the use of upperair sounding and model forecast sounding data, particularly WBT in the analysis of the vertical structure of atmospheric temperature should be paid more attention during cold wave weather involving precipitation phase state prediction.
Based on the routine observations and NCEP reanalysis data (4 times a day), the circulation background, the characteristics of cold air activity, dynamical and water vapor conditions, especially the features of precipitation phase state, and the vertical structure of atmospheric temperature using wetbulb temperature (WBT) are analyzed for the rare cryogenic freezing rain and snow event over Guangdong province in late January 2016. The results show that the primary reason of temperature sudden drop in the north and centralsouth parts of Guangdong Province during this cold wave event is that strong cold air outbroke when the transverse trough swinged southward and the severe cold air moved southward with abnormally strong cold high, frontal zone, cold temperature center and advection in the atmospheric circulation pattern of the transverse trough turning into vertical. The favorable dynamical conditions for the convergence of warm and cold air at 700 hPa and water vapor conditions for the convergence in South China of southwesterly of 700 hPa carrying water vapor from the Bay of Bengal across the north of the IndoChina Peninsula and Beibu Gulf resulted in this weather process. The precipitation phase state was closely related to the intensity of the warm layer (temperature above 0 ℃) and WBT under the favorable circulation, dynamical and water vapor conditions. The warm layer weakened significantly and the subfreezing layer with WBT below 0 ℃ underneath strengthened, leading to the transition of precipitation phase state from rain to solidstate, i.e. snow, sleet and graupel. When the solidstate precipitation appeared, there was no melting effect because of the WBT below 0 ℃ in the middle and lower atmosphere; thus snow or sleet was more likely to be present in the north of Guangdong Province, whereas sleet or graupel was mainly present in the Pearl River Delta, which locates further south due to the existence of a weak warm layer. Therefore, the use of upperair sounding and model forecast sounding data, particularly WBT in the analysis of the vertical structure of atmospheric temperature should be paid more attention during cold wave weather involving precipitation phase state prediction.
2019, 47(1):116-122.
Abstract:
Based on the observation data of climate and air quality, satellite remote sensing and geographic information data, and relevant urban planning data, the wind environment, the thermal/cold environment and atmospheric environment in Chengdu are comprehensively analyzed. The results of study have been applied to the Chengdu 2049 Urban Strategic Planning. The results show that: (1) The dominant wind direction in Chengdu is northeast, and the wind speed in winter is the smallest. In the urban area, the wind speed is decreasing from northeastern to southwest. The estuaries of the Minjiang River and Jianjiang River in the western Longmen pediment region are two main vents in Chengdu. The wind speed of the centralized urban construction area decreased in the 2000s significantly relative to the speed in the 1980s and 1990s, decreased by 0.5 m/s in the northeast and northwest. (2) The strong heat island and the relative strong heat island area increased from 53.6 km2 in 1992 to 798 km2 in 2014, and the center of heat island presented multipolarization. The highgrade ecocold sources were concentrated in the Longmen Mountain and Longquan Mountain. Highintensity urban construction and slope farmland development are the main reasons for the deterioration of the thermal environment. (3) The atmospheric environment in Chengdu is not good and the spatial distribution of air pollution shows a decreasing trend from the central urban area, the inner suburbs, to the outer suburbs. During the period of 2007 to 2014, the annual mean concentrations of PM10 and NO2 in the urban areas exceeded the Grade II national standards for air quality. (4) The urban climatic analysis map of Chengdu is drawn up, and the urban climatic recommendation map is presented by combining with field investigation, land use status quo and development demands. Finally, the proposals for the 2049 Urban Strategic Planning in Chengdu are put forward.
Based on the observation data of climate and air quality, satellite remote sensing and geographic information data, and relevant urban planning data, the wind environment, the thermal/cold environment and atmospheric environment in Chengdu are comprehensively analyzed. The results of study have been applied to the Chengdu 2049 Urban Strategic Planning. The results show that: (1) The dominant wind direction in Chengdu is northeast, and the wind speed in winter is the smallest. In the urban area, the wind speed is decreasing from northeastern to southwest. The estuaries of the Minjiang River and Jianjiang River in the western Longmen pediment region are two main vents in Chengdu. The wind speed of the centralized urban construction area decreased in the 2000s significantly relative to the speed in the 1980s and 1990s, decreased by 0.5 m/s in the northeast and northwest. (2) The strong heat island and the relative strong heat island area increased from 53.6 km2 in 1992 to 798 km2 in 2014, and the center of heat island presented multipolarization. The highgrade ecocold sources were concentrated in the Longmen Mountain and Longquan Mountain. Highintensity urban construction and slope farmland development are the main reasons for the deterioration of the thermal environment. (3) The atmospheric environment in Chengdu is not good and the spatial distribution of air pollution shows a decreasing trend from the central urban area, the inner suburbs, to the outer suburbs. During the period of 2007 to 2014, the annual mean concentrations of PM10 and NO2 in the urban areas exceeded the Grade II national standards for air quality. (4) The urban climatic analysis map of Chengdu is drawn up, and the urban climatic recommendation map is presented by combining with field investigation, land use status quo and development demands. Finally, the proposals for the 2049 Urban Strategic Planning in Chengdu are put forward.
2019, 47(1):123-128.
Abstract:
To investigate the nucleation performance of biogenic ice nucleus Snomax, a laboratory research was carried out in an isothermal cloud chamber. The nucleation quantity, rate, threshold temperature of Snomax were obtained. The laboratory research results indicate that the nucleation rate of Snomax ranges from 108/g to 1011/g at the temperature range of -4 to -18 ℃, and the ice crystal morphology after Snomax catalysis is seriously influenced by the cloud chamber temperature, super cooled water content, and mass concentration. Besides, the nucleation property of silver iodide (AgI) pyrotechnics was tested at the same conditions. Results show that the nucleation rate of AgI is about 3 to 4 orders of magnitude higher than that of Snomax. But the hydrophilic Snomax is much more nucleatingeffective and environmentalfriendly. In comparison with AgI pyrotechnic, the possible application of Snomax in weather modification is discussed.
To investigate the nucleation performance of biogenic ice nucleus Snomax, a laboratory research was carried out in an isothermal cloud chamber. The nucleation quantity, rate, threshold temperature of Snomax were obtained. The laboratory research results indicate that the nucleation rate of Snomax ranges from 108/g to 1011/g at the temperature range of -4 to -18 ℃, and the ice crystal morphology after Snomax catalysis is seriously influenced by the cloud chamber temperature, super cooled water content, and mass concentration. Besides, the nucleation property of silver iodide (AgI) pyrotechnics was tested at the same conditions. Results show that the nucleation rate of AgI is about 3 to 4 orders of magnitude higher than that of Snomax. But the hydrophilic Snomax is much more nucleatingeffective and environmentalfriendly. In comparison with AgI pyrotechnic, the possible application of Snomax in weather modification is discussed.
2019, 47(1):129-139.
Abstract:
According to the observation data of temperature in Shandong Province, using the data of population grid, land use, and night lights comprehensively, the urban and rural stations are divided. The method of comparative analysis based on the observation data is used to study the influence of urbanization on extreme temperature events in Shandong Province. The results show that: (1) Under the push of urbanization, warm events (except the warm night days) increase, while cold events decrease. The contribution rate of warm index to urbanization impact is 40.66% (high temperature), 19.32% (warm day), 1.02% (warm night), and the urbanization impact contribution rate of cold index is 2.31% (low temperature), 5.72% (cold day), 5.55% (cold night), respectively. The contribution to urbanization impact of warm events (except the warm night days) is greater than that of the cold events; in addition, the contribution of extreme temperature indices calculated by the highest temperature is greater. (2)Urbanization strengthens the average field intensity of warm extreme events. The scopes of the equalstrength warm events become more widely than before, but the intensity and scope of cold events are contrary to the performance of warm events under the influence of urbanization. Urbanization prompts the space difference of the average field distributions of extreme warm and cold events more significantly than before. (3) Urbanization may lead to the variation of mutation time, 1 to 3 years earlier, of extreme temperature indexes. (4) Urbanization may affect the duration of extreme temperature events, especially the index associated with the highest temperature. (5) The asymmetrical influence of urbanization between extreme temperature indexes is of complex and diversity.
According to the observation data of temperature in Shandong Province, using the data of population grid, land use, and night lights comprehensively, the urban and rural stations are divided. The method of comparative analysis based on the observation data is used to study the influence of urbanization on extreme temperature events in Shandong Province. The results show that: (1) Under the push of urbanization, warm events (except the warm night days) increase, while cold events decrease. The contribution rate of warm index to urbanization impact is 40.66% (high temperature), 19.32% (warm day), 1.02% (warm night), and the urbanization impact contribution rate of cold index is 2.31% (low temperature), 5.72% (cold day), 5.55% (cold night), respectively. The contribution to urbanization impact of warm events (except the warm night days) is greater than that of the cold events; in addition, the contribution of extreme temperature indices calculated by the highest temperature is greater. (2)Urbanization strengthens the average field intensity of warm extreme events. The scopes of the equalstrength warm events become more widely than before, but the intensity and scope of cold events are contrary to the performance of warm events under the influence of urbanization. Urbanization prompts the space difference of the average field distributions of extreme warm and cold events more significantly than before. (3) Urbanization may lead to the variation of mutation time, 1 to 3 years earlier, of extreme temperature indexes. (4) Urbanization may affect the duration of extreme temperature events, especially the index associated with the highest temperature. (5) The asymmetrical influence of urbanization between extreme temperature indexes is of complex and diversity.
2019, 47(1):140-146.
Abstract:
The wind events caused by tornadoes from 1956 to 2016 in the BeijingTianjinHebei region are evaluated and classified by means of the expert evaluation method according to the Enhanced Fujita Scale, based on the weather reports, the Handbook of China Meteorological Disasters, the meteorological disaster database, local chronicles in archives centers and other relevant historical documents. The spatialtemporal distribution and disaster characteristics of tornadoes are analyzed through the methods of time series analysis, trend analysis and spatial analysis. The main results show that there were 188 tornadoes confirmed in the BeijingTianjinHebei region from 1956 to 2016. In the spatial distribution, there were two areas where tornadoes occurred mostly: Zhangbei County, Shangyi County, Guyuan County and Kangbao County of Zhangjiakou; the eastern part of BeijingTianjinHebei region, especially the coastal areas of Cangzhou, Tianjin, Tangshan and Qinhuangdao. In the temporal distributions, the highest occurrence frequency of tornadoes was the period of 1985 to 1993 and then tornadoes started to decrease after the 1990s. Tornadoes occurred mostly in summer, which accounts for 81.9%, and occurred mainly from 11:00 to 20:00. As for the 122 tornadoes with detail disaster records, based on the Enhanced Fujita (EF) Scale, the results of expert evaluation and classification are: 1 in EF4, 1 EF3, 14 EF2, 52 EF1 and 54 EF0.
The wind events caused by tornadoes from 1956 to 2016 in the BeijingTianjinHebei region are evaluated and classified by means of the expert evaluation method according to the Enhanced Fujita Scale, based on the weather reports, the Handbook of China Meteorological Disasters, the meteorological disaster database, local chronicles in archives centers and other relevant historical documents. The spatialtemporal distribution and disaster characteristics of tornadoes are analyzed through the methods of time series analysis, trend analysis and spatial analysis. The main results show that there were 188 tornadoes confirmed in the BeijingTianjinHebei region from 1956 to 2016. In the spatial distribution, there were two areas where tornadoes occurred mostly: Zhangbei County, Shangyi County, Guyuan County and Kangbao County of Zhangjiakou; the eastern part of BeijingTianjinHebei region, especially the coastal areas of Cangzhou, Tianjin, Tangshan and Qinhuangdao. In the temporal distributions, the highest occurrence frequency of tornadoes was the period of 1985 to 1993 and then tornadoes started to decrease after the 1990s. Tornadoes occurred mostly in summer, which accounts for 81.9%, and occurred mainly from 11:00 to 20:00. As for the 122 tornadoes with detail disaster records, based on the Enhanced Fujita (EF) Scale, the results of expert evaluation and classification are: 1 in EF4, 1 EF3, 14 EF2, 52 EF1 and 54 EF0.
2019, 47(1):147-153.
Abstract:
According to the topography, geomorphology, middle and small rivers, drainage system of Xiqing District in Tianjin, a rainstorm and flood disaster simulation model of small and mediumsized rivers in Xiqing District of Tianjin is established. The objects of the simulating model are the geomorphology and flow movement of open channels. Using the boundary condition of the model based on the dynamic water levels in 14 secondary rivers, an operational experiment for the risk assessment of flood and waterlog disasters in Xiqing District is carried out. The rainstorm and flood disaster simulation model is used in the experimental research for the rainstorm and flood disaster caused by the rainstorm on 20 July 2016. Four simulation schemes are designed to evaluate the waterlog process caused by the high water level and rainstorm. These simulation results are directly used in contrasting and assessing the actual disaster caused by the rainstorm on 20 July 2016.The experiment results indicate that the model can objectively reflect the waterlog disaster caused by the rainstorm and the river water level variation.
According to the topography, geomorphology, middle and small rivers, drainage system of Xiqing District in Tianjin, a rainstorm and flood disaster simulation model of small and mediumsized rivers in Xiqing District of Tianjin is established. The objects of the simulating model are the geomorphology and flow movement of open channels. Using the boundary condition of the model based on the dynamic water levels in 14 secondary rivers, an operational experiment for the risk assessment of flood and waterlog disasters in Xiqing District is carried out. The rainstorm and flood disaster simulation model is used in the experimental research for the rainstorm and flood disaster caused by the rainstorm on 20 July 2016. Four simulation schemes are designed to evaluate the waterlog process caused by the high water level and rainstorm. These simulation results are directly used in contrasting and assessing the actual disaster caused by the rainstorm on 20 July 2016.The experiment results indicate that the model can objectively reflect the waterlog disaster caused by the rainstorm and the river water level variation.
2019, 47(1):154-162.
Abstract:
By using the climate scenario data from the NorESM1M model, the changes of climatic resources in Northeast China are analyzed. The results show: under the scenarios of RCP2.6 and RCP8.5, the annual average temperature of Northeast China shows a rising trend in the 2020s and 2050s, and the rise is particularly significant in the northern part of Heilongjiang and the Lesser Khingan Mountains. The heat condition, reflected by the ≥10 ℃ accumulated temperatures, is improved, and the most significant increase in accumulated temperature occurs in Heilongjiang Province. The precipitation in the region remains essentially unchanged with a slight increase. Under the influence of increased temperature, the region shows a significant increase in evapotranspiration and a light decrease in humidity in the 2050s. Under the influence of improved heat condition and increased evapotranspiration, the length of the growing period of the region shows an increasing trend, increasing by an average of 12.4 days till the mid21st century.
By using the climate scenario data from the NorESM1M model, the changes of climatic resources in Northeast China are analyzed. The results show: under the scenarios of RCP2.6 and RCP8.5, the annual average temperature of Northeast China shows a rising trend in the 2020s and 2050s, and the rise is particularly significant in the northern part of Heilongjiang and the Lesser Khingan Mountains. The heat condition, reflected by the ≥10 ℃ accumulated temperatures, is improved, and the most significant increase in accumulated temperature occurs in Heilongjiang Province. The precipitation in the region remains essentially unchanged with a slight increase. Under the influence of increased temperature, the region shows a significant increase in evapotranspiration and a light decrease in humidity in the 2050s. Under the influence of improved heat condition and increased evapotranspiration, the length of the growing period of the region shows an increasing trend, increasing by an average of 12.4 days till the mid21st century.
2019, 47(1):163-170.
Abstract:
Based on a drought process in the Hulunbuir prairie from spring to summer in 2017, the monitoring results of various meteorological drought indexes (Pa30, SPI30, SPEI30, CI, MCI) and the Vegetation Status Index from April to September in 2017 are analyzed and compared by using the data of air temperature, precipitation and MODIS NDV of 6 meteorological stations. The results show that meteorological drought indexes (Pa30 and SPI30), which consider only precipitation, fluctuated greatly in April, which cannot reflect the impact of high temperature and other meteorological conditions on drought development. Due to the introduction of meteorological elements in CI and MCI calculation for multiperiods of time and the prolonged light drought while droughts alleviating, and the relatively rapid recovery of vegetation after the increase of precipitation, a large difference between vegetation and monitoring during drought remission are resulted in. The correlation between MCI and VCI in the same and previous periods is the best, and that between SPEI30 and VCI in the first two periods is good, and the correlation between Meteorological Drought Index and VCI, which considers only precipitation, is generally worse. With a longer response time for vegetation, SPEI30 is more suitable for the early warning of prairie ecological droughts.
Based on a drought process in the Hulunbuir prairie from spring to summer in 2017, the monitoring results of various meteorological drought indexes (Pa30, SPI30, SPEI30, CI, MCI) and the Vegetation Status Index from April to September in 2017 are analyzed and compared by using the data of air temperature, precipitation and MODIS NDV of 6 meteorological stations. The results show that meteorological drought indexes (Pa30 and SPI30), which consider only precipitation, fluctuated greatly in April, which cannot reflect the impact of high temperature and other meteorological conditions on drought development. Due to the introduction of meteorological elements in CI and MCI calculation for multiperiods of time and the prolonged light drought while droughts alleviating, and the relatively rapid recovery of vegetation after the increase of precipitation, a large difference between vegetation and monitoring during drought remission are resulted in. The correlation between MCI and VCI in the same and previous periods is the best, and that between SPEI30 and VCI in the first two periods is good, and the correlation between Meteorological Drought Index and VCI, which considers only precipitation, is generally worse. With a longer response time for vegetation, SPEI30 is more suitable for the early warning of prairie ecological droughts.
2019, 47(1):171-178.
Abstract:
According to the information of cyanobacteria bloom on the Taihu Lake retrieved from satellite remote sensing from 2005 to 2017 and the regional meteorological observation data, it is shown that the Taihu Lake cyanobacteria bloom occurred in the daily average temperature range of 0 to 35 ℃, with the highincidence interval being 15.1 to 35 ℃, within which the bloom cyanobacterial area accounts for 90%, and the largescale cyanobacterial bloom (the area of a single cyanobacteria bloom event exceeds 20% of the surface area of the Taihu Lake, 468 km2) accounts for 93%. Within 6 hours before the satellite passing, in the average wind speed being 0.2 to 4.8 m/s, the cyanobacterial bloom can be observed, with the most suitable wind speed range being 05 to 34 m/s, within which the occurrence number of cyanobacterial bloom accounts for 94.7%. The largescale cyanobacterial bloom mainly occurred when the average wind speed was 0 to 20 m/s, accounting for 89%. The wind direction mainly affects the movement and spatial distribution of cyanobacterial bloom. Precipitation generally has a negative impact on the occurrence and development of cyanobacterial bloom. While there occurred was largearea cyanobacteria bloom, the situation that there was small precipitation (<10 mm) in the first 24 hours accounts for 88%, indicating that the moderate disturbance of light rainfall is conducive to the formation of largeareas cyanobacteria blooms. Sufficient sunshine may be one of the conditions for cyanobacterial bloom, but not a necessary condition. On the basis of this, a multivariate regression comprehensive meteorological index model is established, and the fitting result is good, passed the 0.001level significance test.
According to the information of cyanobacteria bloom on the Taihu Lake retrieved from satellite remote sensing from 2005 to 2017 and the regional meteorological observation data, it is shown that the Taihu Lake cyanobacteria bloom occurred in the daily average temperature range of 0 to 35 ℃, with the highincidence interval being 15.1 to 35 ℃, within which the bloom cyanobacterial area accounts for 90%, and the largescale cyanobacterial bloom (the area of a single cyanobacteria bloom event exceeds 20% of the surface area of the Taihu Lake, 468 km2) accounts for 93%. Within 6 hours before the satellite passing, in the average wind speed being 0.2 to 4.8 m/s, the cyanobacterial bloom can be observed, with the most suitable wind speed range being 05 to 34 m/s, within which the occurrence number of cyanobacterial bloom accounts for 94.7%. The largescale cyanobacterial bloom mainly occurred when the average wind speed was 0 to 20 m/s, accounting for 89%. The wind direction mainly affects the movement and spatial distribution of cyanobacterial bloom. Precipitation generally has a negative impact on the occurrence and development of cyanobacterial bloom. While there occurred was largearea cyanobacteria bloom, the situation that there was small precipitation (<10 mm) in the first 24 hours accounts for 88%, indicating that the moderate disturbance of light rainfall is conducive to the formation of largeareas cyanobacteria blooms. Sufficient sunshine may be one of the conditions for cyanobacterial bloom, but not a necessary condition. On the basis of this, a multivariate regression comprehensive meteorological index model is established, and the fitting result is good, passed the 0.001level significance test.
2019, 47(1):179-185.
Abstract:
In order to satisfy the strong operational demand for high spacetime resolution numerical forecast products in the Central China area, the highresolution and rapidrefresh numerical weather prediction model system for Central China was designed and have operated since July 2015. In December 2017, the structural adjustment of this model system was conducted according to the operational needs. As the system has the characteristics of complex processes and numerous steps, a monitoring system, which fully considers the relationship between various model processes and integrates all processes as a whole, is designed and implemented based on ECFLOW technology. The process monitoring system has a beautiful and friendly graphical interface and clear flow structure that can make the operation simple and fault location accurate, which can improve greatly the working efficiency of operation, monitoring, and maintenance.
In order to satisfy the strong operational demand for high spacetime resolution numerical forecast products in the Central China area, the highresolution and rapidrefresh numerical weather prediction model system for Central China was designed and have operated since July 2015. In December 2017, the structural adjustment of this model system was conducted according to the operational needs. As the system has the characteristics of complex processes and numerous steps, a monitoring system, which fully considers the relationship between various model processes and integrates all processes as a whole, is designed and implemented based on ECFLOW technology. The process monitoring system has a beautiful and friendly graphical interface and clear flow structure that can make the operation simple and fault location accurate, which can improve greatly the working efficiency of operation, monitoring, and maintenance.
2019, 47(1):186-190.
Abstract:
In order to improve the technical level of modern agrometeorological service, the quality of agricultural products, and the efficiency of agricultural services, a platform for climate quality certification and traceability of agricultural products is developed based on the J2EE technical framework and the Eclipse development environment. This platform uses a threelayer WEB architecture and the MVC design pattern and designs the components such as the interface layer, system platform infrastructure layer, JSP general architecture framework, business service layer and WEB application layer, which improves the system security, portability and development efficiency effectively. This paper introduces the system architecture, workflow and key technologies in detail. The authentication module adopts the mode of combining platform evaluation with expert evaluation, which improves the reliability of authentication information. The traceability module adopts the AES and RSA hybrid encryption algorithm to generate QR codes, which ensures the security of the traceability system of agricultural products.
In order to improve the technical level of modern agrometeorological service, the quality of agricultural products, and the efficiency of agricultural services, a platform for climate quality certification and traceability of agricultural products is developed based on the J2EE technical framework and the Eclipse development environment. This platform uses a threelayer WEB architecture and the MVC design pattern and designs the components such as the interface layer, system platform infrastructure layer, JSP general architecture framework, business service layer and WEB application layer, which improves the system security, portability and development efficiency effectively. This paper introduces the system architecture, workflow and key technologies in detail. The authentication module adopts the mode of combining platform evaluation with expert evaluation, which improves the reliability of authentication information. The traceability module adopts the AES and RSA hybrid encryption algorithm to generate QR codes, which ensures the security of the traceability system of agricultural products.
External LinksChina Meteorological AdministrationCMA Meteorological Observation CentreChinese Academy of Meteorological SciencesBeijing Meteorological ServiceNational Satellite Meteorological Center
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.