ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 46,Issue 2,2020 Table of Contents
2020, 46(2):145-157.
DOI: 10.7519/j.issn.1000-0526.2020.02.001
Abstract:
Based on the new global surface temperature data set CMST (China merged surface temperature), we systematically evaluated the historical climate simulation results of the 27 global climate models which are participating in the International Coupling Model Comparison Plan Phase 5 (CMIP5) from 1900 to 2017. Historic model simulations for the period of 1900-2005 and projections for the 3 different representative concentration pathways (RCP2.6, RCP4.5, RCP8.5) for 2006-2017. According to the comparison of various parameters in Taylor diagram, 9 models with better simulation results (MT9) are selected to present the models ensemble simulations. Compared with the ensemble average of mean all models (MAM), under any of the three RCPS, MT9 is significantly closer to the observed value (MAM overestimates the temperature change) in both spatial distribution and time variation . On this basis, this paper uses the prediction results of MT9 to analyze the amplitude of Asia surface air temperature rises during 2018-2099. The result showed that MT9 is expected to have smaller temperature warming than those of MAM under all the RCPs in the Asian region, which is about 0.08℃ for RCP 2.6, 1.20℃ for RCP4.5 and 3.54℃ for RCP8.5. These results are all smaller than those from the MAM ensembles, thus are more reasonable. In addition, this paper also analyzed the spatial distribution of the surface temperature anomalies in Asia based on the MT9.
Based on the new global surface temperature data set CMST (China merged surface temperature), we systematically evaluated the historical climate simulation results of the 27 global climate models which are participating in the International Coupling Model Comparison Plan Phase 5 (CMIP5) from 1900 to 2017. Historic model simulations for the period of 1900-2005 and projections for the 3 different representative concentration pathways (RCP2.6, RCP4.5, RCP8.5) for 2006-2017. According to the comparison of various parameters in Taylor diagram, 9 models with better simulation results (MT9) are selected to present the models ensemble simulations. Compared with the ensemble average of mean all models (MAM), under any of the three RCPS, MT9 is significantly closer to the observed value (MAM overestimates the temperature change) in both spatial distribution and time variation . On this basis, this paper uses the prediction results of MT9 to analyze the amplitude of Asia surface air temperature rises during 2018-2099. The result showed that MT9 is expected to have smaller temperature warming than those of MAM under all the RCPs in the Asian region, which is about 0.08℃ for RCP 2.6, 1.20℃ for RCP4.5 and 3.54℃ for RCP8.5. These results are all smaller than those from the MAM ensembles, thus are more reasonable. In addition, this paper also analyzed the spatial distribution of the surface temperature anomalies in Asia based on the MT9.
2020, 46(2):158-168.
DOI: 10.7519/j.issn.10000526.2020.02.002
Abstract:
Mesoscale observations are used to study cases of severe convective weather that occurred near Tianmu Mountain in subtropical high synoptic situation in order to understand the impact of Tianmu Mountain on convective initiation (CI). The results show that, when Zhejiang Province is at the edge of subtropical high, the lowlevel flow is southwesterly and the Froude number is low, the upstream flow passing over the mountains forms a convergence line at the lee side of Huang Mountain and Tianmu Mountain, which factors CI in conjunction of thermal conditions. The thermal effect of the mountain causes cumulus clouds above the mountain area. The distribution of the cumulus clouds is consistent with the orography. Meanwhile, a belt of cumulus clouds forms at the lee side as a result of the convergence line. The convergence line extends tens of kilometers, and the direction changes with the ambient wind direction. Convective cells are initiated at the western end of the convergence line near the mountain. This suggests that CI may occur when the thermalforced cumulus clouds move above the convergence line and continue to develop. In other words, thermal and dynamic effects of the mountain trigger the CI together.
Mesoscale observations are used to study cases of severe convective weather that occurred near Tianmu Mountain in subtropical high synoptic situation in order to understand the impact of Tianmu Mountain on convective initiation (CI). The results show that, when Zhejiang Province is at the edge of subtropical high, the lowlevel flow is southwesterly and the Froude number is low, the upstream flow passing over the mountains forms a convergence line at the lee side of Huang Mountain and Tianmu Mountain, which factors CI in conjunction of thermal conditions. The thermal effect of the mountain causes cumulus clouds above the mountain area. The distribution of the cumulus clouds is consistent with the orography. Meanwhile, a belt of cumulus clouds forms at the lee side as a result of the convergence line. The convergence line extends tens of kilometers, and the direction changes with the ambient wind direction. Convective cells are initiated at the western end of the convergence line near the mountain. This suggests that CI may occur when the thermalforced cumulus clouds move above the convergence line and continue to develop. In other words, thermal and dynamic effects of the mountain trigger the CI together.
2020, 46(2):169-178.
DOI: 10.7519/j.issn.10000526.2020.02.003
Abstract:
The freezing rain distribution, time evolution and circulation characteristics of the two freezing rain processes that occurred in southern Anhui Province from 4 to 7, and from 24 to 27 in January 2018 were analyzed based on the daily observation data and ERAInterim reanalysis data collected four times a day. The results showed that the onset time of the freezing rain can be estimated approximately by the sudden drop of wind speed to 0 m·s-1 and the fixed wind direction from the automatic meteorological stations, which is earlier than human observation. The two processes appeared in the condition of quasistatic weather, but the mechanism for their formation were different. The process during 4-7 January 2018 was of typical “ice melting” mechanism, while the process during 24-27 belonged to typical “supercooled warm rain” mechanism. The surface cold high in the East Asian Continent made the south of Anhui controlled by the northeastern wind during the two freezing rain processes. The cold advection of the northeastern wind developed a cold cushion from the nearsurface to the ground, and the warm advection from the warm wet air in front of the southern branch trough near 750 hPa was the main cause for the maintenance and development of the melting or inversion layer. So, when vertical distribution of highaltitude temperature satisfies the condition for freezing rain, the surface location of 0℃ directly affects the range of freezing rain.
The freezing rain distribution, time evolution and circulation characteristics of the two freezing rain processes that occurred in southern Anhui Province from 4 to 7, and from 24 to 27 in January 2018 were analyzed based on the daily observation data and ERAInterim reanalysis data collected four times a day. The results showed that the onset time of the freezing rain can be estimated approximately by the sudden drop of wind speed to 0 m·s-1 and the fixed wind direction from the automatic meteorological stations, which is earlier than human observation. The two processes appeared in the condition of quasistatic weather, but the mechanism for their formation were different. The process during 4-7 January 2018 was of typical “ice melting” mechanism, while the process during 24-27 belonged to typical “supercooled warm rain” mechanism. The surface cold high in the East Asian Continent made the south of Anhui controlled by the northeastern wind during the two freezing rain processes. The cold advection of the northeastern wind developed a cold cushion from the nearsurface to the ground, and the warm advection from the warm wet air in front of the southern branch trough near 750 hPa was the main cause for the maintenance and development of the melting or inversion layer. So, when vertical distribution of highaltitude temperature satisfies the condition for freezing rain, the surface location of 0℃ directly affects the range of freezing rain.
2020, 46(2):179-188.
DOI: 10.7519/j.issn.10000526.2020.02.004
Abstract:
Based on Jinan Doppler weather radar data, sounding and automatic weather station data, the radar echo characteristics including the effect of cloudstreets on three heavy rainfalls in Shandong Province were analyzed. The results showed as follows. The cloudstreets appear as narrowband echoes oriented in the direction of mean lowlevel wind in lowlevel base reflectivity, the duration is about 6-7 hours, and the intensity is about 5-20 dBz. The main effects of cloudstreets on three heavy precipitations are as follows. First is the triggering mechanism. Cloudstreets can trigger convection cells. Second is the backward propagation mechanism. The new storms triggered by cloudstreets spread to the southwest in turn along the orientation of cloudstreets. This backward propagation characteristic can lead the convective system to move toward west by south direction and lead the severe precipitation area to the southwest direction. Third is enhancing precipitation intensity and duration. The continuous storms triggered by cloudstreets develop northeastward under the action of the pilot airflow, and merge with the main echoes of convective system. Therefore, the main echoes will be strengthened, generating large rain intensity and lasting for a long time, finally resulting in extreme severe rainfall weather. The cloudstreets play an important role in the maintenance and development of the three convective systems and in the generation of extreme severe rainfall. The frequency of thunderstorm triggered in the 18 July process is significantly higher than that of the other two processes, and the main reason is that the convective inhibition energy (CIN) is significantly smaller than the other two processes. Small CIN and lifting condensation level are easier to trigger the outbreak of thunderstorms.
Based on Jinan Doppler weather radar data, sounding and automatic weather station data, the radar echo characteristics including the effect of cloudstreets on three heavy rainfalls in Shandong Province were analyzed. The results showed as follows. The cloudstreets appear as narrowband echoes oriented in the direction of mean lowlevel wind in lowlevel base reflectivity, the duration is about 6-7 hours, and the intensity is about 5-20 dBz. The main effects of cloudstreets on three heavy precipitations are as follows. First is the triggering mechanism. Cloudstreets can trigger convection cells. Second is the backward propagation mechanism. The new storms triggered by cloudstreets spread to the southwest in turn along the orientation of cloudstreets. This backward propagation characteristic can lead the convective system to move toward west by south direction and lead the severe precipitation area to the southwest direction. Third is enhancing precipitation intensity and duration. The continuous storms triggered by cloudstreets develop northeastward under the action of the pilot airflow, and merge with the main echoes of convective system. Therefore, the main echoes will be strengthened, generating large rain intensity and lasting for a long time, finally resulting in extreme severe rainfall weather. The cloudstreets play an important role in the maintenance and development of the three convective systems and in the generation of extreme severe rainfall. The frequency of thunderstorm triggered in the 18 July process is significantly higher than that of the other two processes, and the main reason is that the convective inhibition energy (CIN) is significantly smaller than the other two processes. Small CIN and lifting condensation level are easier to trigger the outbreak of thunderstorms.
2020, 46(2):189-199.
DOI: 10.7519/j.issn.10000526.2020.02.005
Abstract:
Based on the cloudground lightning location data of the National Lightning Monitoring Network from 2010 to 2014, 505 257 thunderstorm systems were obtained by using the thunderstorm identifying and tracking algorithm, and then the occurrence and development characteristics of thunderstorms in central and eastern China were statistically analyzed. Due to the differences in topography and climate, in this paper, we divided the central and eastern part of China into five regions: Northeast China, North China, Central China and East China, Southwest China and South China. We compared the thunderstorm characteristic parameters, including duration, covering range and speed, etc., analyzed the characteristics of environmental physical quantities of thunderstorms, and also discussed the correlation between thunderstorms and topography. The results showed that thunderstorms have the characteristics of strong localization and rapid development. 〖JP2〗The moving speed of more than 70% 〖JP〗thunderstorms is slower than 60 km·h-1, the duration of more than 80% thunderstorms is less than 2 h, and the covering range of more than 90% of thunderstorms is less than 60 km. The thunderstorms in Northeast China tend to move faster, whereas those in Southwest China travel slower and the covering range is even less. The thunderstorms in Central China, East China, and South China have the highest levels of CAPE (convective available potential energy), followed by the Southwest, and the lowest CAPE is found in Northeast China and North China. In comparison, the situation for the vertical wind shear of 0-6 km is on the contrary. Guangdong and Hai nan Provinces are the regions where thunderstorms are most frequently generated. South of Yangtze Ri ver, east of Southwest China, west of South China and the Taihang Mountain regions are prone to have more active thunderstorms. In addition, the generation of thunderstorms is closely related to terrain, thus, the west foot of Sichuan Basin and the Pearl River Delta often see the thunderstorm triggered by the obvious lift of terrain.
Based on the cloudground lightning location data of the National Lightning Monitoring Network from 2010 to 2014, 505 257 thunderstorm systems were obtained by using the thunderstorm identifying and tracking algorithm, and then the occurrence and development characteristics of thunderstorms in central and eastern China were statistically analyzed. Due to the differences in topography and climate, in this paper, we divided the central and eastern part of China into five regions: Northeast China, North China, Central China and East China, Southwest China and South China. We compared the thunderstorm characteristic parameters, including duration, covering range and speed, etc., analyzed the characteristics of environmental physical quantities of thunderstorms, and also discussed the correlation between thunderstorms and topography. The results showed that thunderstorms have the characteristics of strong localization and rapid development. 〖JP2〗The moving speed of more than 70% 〖JP〗thunderstorms is slower than 60 km·h-1, the duration of more than 80% thunderstorms is less than 2 h, and the covering range of more than 90% of thunderstorms is less than 60 km. The thunderstorms in Northeast China tend to move faster, whereas those in Southwest China travel slower and the covering range is even less. The thunderstorms in Central China, East China, and South China have the highest levels of CAPE (convective available potential energy), followed by the Southwest, and the lowest CAPE is found in Northeast China and North China. In comparison, the situation for the vertical wind shear of 0-6 km is on the contrary. Guangdong and Hai nan Provinces are the regions where thunderstorms are most frequently generated. South of Yangtze Ri ver, east of Southwest China, west of South China and the Taihang Mountain regions are prone to have more active thunderstorms. In addition, the generation of thunderstorms is closely related to terrain, thus, the west foot of Sichuan Basin and the Pearl River Delta often see the thunderstorm triggered by the obvious lift of terrain.
2020, 46(2):200-211.
DOI: 10.7519/j.issn.10000526.2020.02.006
Abstract:
Using the denselyobserved hourly precipitation (>1 mm) data of the automatic weather stations (referred to as the all stations) and the national meteorological stations (referred to as the national stations) in Shandong Province from April to October 2008-2017, this paper compares the characteristics of spatiotemporal distribution of extreme shorttime severe precipitation with different resolution data. The results are as follows. The skewed characteristics of hourly precipitation at all stations are more obvious than those of the national stations. For the average state of hourly precipitation, both are representative. However, for the analysis of the extremes of shorttime severe rainfall, the all stations data are more advantageous. It is most reasonable to use the 99.5th percentile of each station as the threshold for extreme shorttime severe precipitation. The spatial distribution characteristics of the 30-45 mm threshold are similar for all stations and national stations. For thresholds above 45 mm, the values and ranges of all stations are both greater than those of the national stations. The extreme shorttime severe precipitation intensity in most parts of the province is concentrated at 40-60 mm·h-1, and the spatial distribution characteristics of all stations and national stations in this interval are similar. Nationalstation data can not reflect the spatial distribution of extreme shorttime severe precipitation with intensity below 40 mm·h-1 and above 60 mm·h-1. The spatial distribution characteristics of extreme shorttime severe precipitation intensity are closely related to geographical location and topographical features. The extreme shorttime precipitation intensity, daily maximum precipitation, summer precipitation and annual precipitation in the southeastern Shandong Province rank first in the province. Although the frequency and intensity of severe precipitation are high in northwestern Shandong, they have no positive correlations with annual precipitation and summer precipitation. The monthly and diurnal variations of the extreme shorttime severe precipitation frequency of all stations are consistent with those of the national stations. However, the nationalstation data can not fully represent the monthly and diurnal variations of the extreme shorttime severe precipitation intensity in the province. The data of all stations can more accurately reflect the time variation features of precipitation in the province.
Using the denselyobserved hourly precipitation (>1 mm) data of the automatic weather stations (referred to as the all stations) and the national meteorological stations (referred to as the national stations) in Shandong Province from April to October 2008-2017, this paper compares the characteristics of spatiotemporal distribution of extreme shorttime severe precipitation with different resolution data. The results are as follows. The skewed characteristics of hourly precipitation at all stations are more obvious than those of the national stations. For the average state of hourly precipitation, both are representative. However, for the analysis of the extremes of shorttime severe rainfall, the all stations data are more advantageous. It is most reasonable to use the 99.5th percentile of each station as the threshold for extreme shorttime severe precipitation. The spatial distribution characteristics of the 30-45 mm threshold are similar for all stations and national stations. For thresholds above 45 mm, the values and ranges of all stations are both greater than those of the national stations. The extreme shorttime severe precipitation intensity in most parts of the province is concentrated at 40-60 mm·h-1, and the spatial distribution characteristics of all stations and national stations in this interval are similar. Nationalstation data can not reflect the spatial distribution of extreme shorttime severe precipitation with intensity below 40 mm·h-1 and above 60 mm·h-1. The spatial distribution characteristics of extreme shorttime severe precipitation intensity are closely related to geographical location and topographical features. The extreme shorttime precipitation intensity, daily maximum precipitation, summer precipitation and annual precipitation in the southeastern Shandong Province rank first in the province. Although the frequency and intensity of severe precipitation are high in northwestern Shandong, they have no positive correlations with annual precipitation and summer precipitation. The monthly and diurnal variations of the extreme shorttime severe precipitation frequency of all stations are consistent with those of the national stations. However, the nationalstation data can not fully represent the monthly and diurnal variations of the extreme shorttime severe precipitation intensity in the province. The data of all stations can more accurately reflect the time variation features of precipitation in the province.
2020, 46(2):212-222.
DOI: 10.7519/j.issn.10000526.2020.02.007
Abstract:
By using data of surface, upper air, lightning location and Doppler weather radar from in Sichuan Basin during 2009-2018, 34 cases of thunderstorm gale processes are counted out. And on the basis of cold air participation and 500 hPa impact system, these thunderstorm gale processes can be divided in to five types: mixed gale (Ⅰ), thunderstorm gale behind deep trough (vortex) (Ⅱ1), trough (shear) moving eastward thunderstorm gale (Ⅱ2), shear thunderstorm gale on west side of subtropical high pressure belt (Ⅱ3), 〖JP2〗and east wind disturbance thunderstorm gale (Ⅱ4). Besides, the radar echo characteristics of thunderstorm gale stations in the five kinds of processes are analyzed statistcally, including convective organization type, radar echo intensity, echo tops, vertical integrated liquid, midaltitude radial convergence, storm moving speed, echo centroid decline, high value area of wind speed at low elevation and divergence. The results show that 82% thunderstorm gale stations have high value areas of wind speed, different types of thunderstorm gale have other different warning indicators, and all these warning indicators can be advanced by more than 10 minutes. Furthermore, when there is midaltitude radial convergence, divergence, high echo intensity with strong gradient or echo type being squall line at station, we should also consider the possibility of strong wind.
By using data of surface, upper air, lightning location and Doppler weather radar from in Sichuan Basin during 2009-2018, 34 cases of thunderstorm gale processes are counted out. And on the basis of cold air participation and 500 hPa impact system, these thunderstorm gale processes can be divided in to five types: mixed gale (Ⅰ), thunderstorm gale behind deep trough (vortex) (Ⅱ1), trough (shear) moving eastward thunderstorm gale (Ⅱ2), shear thunderstorm gale on west side of subtropical high pressure belt (Ⅱ3), 〖JP2〗and east wind disturbance thunderstorm gale (Ⅱ4). Besides, the radar echo characteristics of thunderstorm gale stations in the five kinds of processes are analyzed statistcally, including convective organization type, radar echo intensity, echo tops, vertical integrated liquid, midaltitude radial convergence, storm moving speed, echo centroid decline, high value area of wind speed at low elevation and divergence. The results show that 82% thunderstorm gale stations have high value areas of wind speed, different types of thunderstorm gale have other different warning indicators, and all these warning indicators can be advanced by more than 10 minutes. Furthermore, when there is midaltitude radial convergence, divergence, high echo intensity with strong gradient or echo type being squall line at station, we should also consider the possibility of strong wind.
2020, 46(2):223-233.
DOI: 10.7519/j.issn.10000526.2020.02.008
Abstract:
Based on NCEP/NCAR reanalysis data and conventional meteorological and hydrological observation data, the meteorological and hydrological characteristics of the upper Yangtze River Basin during the severe flooding period from June to July 2018 are analyzed. The results show that three heavy precipitation processes occurred during the flooding period of the upper Yangtze River Basin in 2018, and the precipitation falling areas overlaped highly in the northern part of the upper Yangtze River Basin, causing serious disaster. Largescale circulation analysis shows that the low trough, subtropical high, Okhotsk blocking high and Ural blocking high in middle and high latitudes were stronger than those in the same period in records. The northsouth swing of subtropical high was larger. When the subtropical high jumped northward, it would encounter the cold air behind the trough in the upper Yangtze River Basin, forming a heavy precipitation process. The “saddle” configuration of largescale circulation facilitated the water vapor transport from the Bay of Bengal and the South China Sea to the upper Yangtze River Basin, and the convergence of water vapor in the region and the midlatitude westerly zone formed heavy precipitation. Compared with the historic records, we find that the precipitation in the upper Yangtze River Basin in 2018 was characterized by strong surface intensity, strong extreme precipitation in the northern tributaries and more concentrated raining period. Compared with the rainfall in 2012, the northern 〖JP2〗tributary of the upper〖JP〗 Yangtze River Basin had high water level and long time of exceeding the warning water level. The flood situation of Tuojiang River, Fujiang River and Jialing River was stronger than that of 2012. In 2018, the total precipitation and peak flow of the upper Yangtze River Basin did not exceed the situation in 2012, but the flood disasters caused by the Tuojiiang River, Fujiang River and Jialing River in the north of the upper Yangtze River Basin could exceed 2012.
Based on NCEP/NCAR reanalysis data and conventional meteorological and hydrological observation data, the meteorological and hydrological characteristics of the upper Yangtze River Basin during the severe flooding period from June to July 2018 are analyzed. The results show that three heavy precipitation processes occurred during the flooding period of the upper Yangtze River Basin in 2018, and the precipitation falling areas overlaped highly in the northern part of the upper Yangtze River Basin, causing serious disaster. Largescale circulation analysis shows that the low trough, subtropical high, Okhotsk blocking high and Ural blocking high in middle and high latitudes were stronger than those in the same period in records. The northsouth swing of subtropical high was larger. When the subtropical high jumped northward, it would encounter the cold air behind the trough in the upper Yangtze River Basin, forming a heavy precipitation process. The “saddle” configuration of largescale circulation facilitated the water vapor transport from the Bay of Bengal and the South China Sea to the upper Yangtze River Basin, and the convergence of water vapor in the region and the midlatitude westerly zone formed heavy precipitation. Compared with the historic records, we find that the precipitation in the upper Yangtze River Basin in 2018 was characterized by strong surface intensity, strong extreme precipitation in the northern tributaries and more concentrated raining period. Compared with the rainfall in 2012, the northern 〖JP2〗tributary of the upper〖JP〗 Yangtze River Basin had high water level and long time of exceeding the warning water level. The flood situation of Tuojiang River, Fujiang River and Jialing River was stronger than that of 2012. In 2018, the total precipitation and peak flow of the upper Yangtze River Basin did not exceed the situation in 2012, but the flood disasters caused by the Tuojiiang River, Fujiang River and Jialing River in the north of the upper Yangtze River Basin could exceed 2012.
2020, 46(2):234-244.
DOI: 10.7519/j.issn.10000526.2020.02.009
Abstract:
Taking the beginning dates of flowering (BDF) as the research object, this paper analyzed the spatiotemporal variation trend of the BDF in Jiangsu Province from 1980 to 2016 by using the observation data and synchronous meteorological data. Combined with physiological characteristics of oilseed rape, the meteorological factors significantly related to the initial flowering period were selected, and the effect and sensitivity of meteorological factors were defined by path analysis. Moreover, the regression prediction model of initial flowering period was constructed. The results showed that under the background of climate change, the BDF shows a tendency of advancing year by year, with an average advance of more than three days in regions south of the Huaihe River. There are eight factors, that are significantly positively correlated to the BDF, which include: the beginning date of the daily average temperature (DAT) above 0℃ stably in previous year (X1), the ending date of the DAT above 5℃ stably (X2), the effective accumulated temperature above 0, 5 and 10℃ (X3, X4 and X5), the number of days with daily minimum temperature below 0 or 5 ℃ (X6 and X7) and average minimum temperature (X8) between budding stage and flowering stage (from early February to early March) in current year. The directly effects of X8, X7 and X4 rank the top three, and the relative determination degree of these three factors to the initial flowering period of rape is also ranked among the top three factors to the total contribution rate (TCR) of all factors to the R2 of the regression prediction model, while the direct effect of the remaining five factors are generally weaker than the indirect effect. And the remaining five factors mainly affect the BDF through X4, X7, X8, while X4, X7, X8 also exert some influence through these 5 factors. Removing any factor would change the direct and indirect effects on the BDF. In addition, the regression prediction model constructed by the above eight factors can explain 68.48% of the changes of the BDF (e.g. Gaochun Region), which is also suitable for some other regions. As far as Jiangsu Province is concerned, light and precipitation have little influence on the BDF, while heat condition is the main limiting factor. In a word, the prediction model of the BDF constructed in this paper can better reflect the rule of the BDF and the change of related heat factors.
Taking the beginning dates of flowering (BDF) as the research object, this paper analyzed the spatiotemporal variation trend of the BDF in Jiangsu Province from 1980 to 2016 by using the observation data and synchronous meteorological data. Combined with physiological characteristics of oilseed rape, the meteorological factors significantly related to the initial flowering period were selected, and the effect and sensitivity of meteorological factors were defined by path analysis. Moreover, the regression prediction model of initial flowering period was constructed. The results showed that under the background of climate change, the BDF shows a tendency of advancing year by year, with an average advance of more than three days in regions south of the Huaihe River. There are eight factors, that are significantly positively correlated to the BDF, which include: the beginning date of the daily average temperature (DAT) above 0℃ stably in previous year (X1), the ending date of the DAT above 5℃ stably (X2), the effective accumulated temperature above 0, 5 and 10℃ (X3, X4 and X5), the number of days with daily minimum temperature below 0 or 5 ℃ (X6 and X7) and average minimum temperature (X8) between budding stage and flowering stage (from early February to early March) in current year. The directly effects of X8, X7 and X4 rank the top three, and the relative determination degree of these three factors to the initial flowering period of rape is also ranked among the top three factors to the total contribution rate (TCR) of all factors to the R2 of the regression prediction model, while the direct effect of the remaining five factors are generally weaker than the indirect effect. And the remaining five factors mainly affect the BDF through X4, X7, X8, while X4, X7, X8 also exert some influence through these 5 factors. Removing any factor would change the direct and indirect effects on the BDF. In addition, the regression prediction model constructed by the above eight factors can explain 68.48% of the changes of the BDF (e.g. Gaochun Region), which is also suitable for some other regions. As far as Jiangsu Province is concerned, light and precipitation have little influence on the BDF, while heat condition is the main limiting factor. In a word, the prediction model of the BDF constructed in this paper can better reflect the rule of the BDF and the change of related heat factors.
2020, 46(2):245-256.
DOI: 10.7519/j.issn.10000526.2020.02.010
Abstract:
This paper investigates the tornado detection radar technology and observation research in the United States in the past 20 years. The literature shows that the development targets of the tornado detection radar in the United States are mainly to achieve fast scanning, high spatialtemporal resolution and high precision data acquisition. The purpose has been basically achieved. The volume scanning time of the radar is up to 10 s and the radar is updated. In close range, the resolution can reach 10 meters or even lower, which makes it possible to collect the fine structure and detailed continuous evolution of tornadoes. The development of radar in the United States adopts a variety of technical systems and scanning strategies, and the dual polarization, phased array, atmospheric imaging and other technologies are constantly improved and applied, with good results. Based on advanced radar, the United States has carried out a large number of tornado observation experiments, achieving rich results. The structure and evolution of tornadoes are described more and more precisely and accurately. Many achievements have been transformed into conceptual models, forming important tornado monitoring and forecasting indicators, early warning signals, and implemented in operations, improving the tornado early warning capability. The application of highfrequency and highprecision numerical models for tornado radar data has also significantly shortened the data assimilation period and improved the simulation ability of convective scale systems such as tornadoes. Referring to the successful experience of the United States, China should draw on its technical achievements, select the technical system for radar development as soon as possible, speed up the upgrading of operational radar technology and the development of highperformance tornado detection radar, organize tornado scientific observation experiments, collect fine tornado data, carry out scientific research, and explore the structure and activity regularity of tornadoes in China, providing a scientific support for the construction of tornado monitoring and warning.
This paper investigates the tornado detection radar technology and observation research in the United States in the past 20 years. The literature shows that the development targets of the tornado detection radar in the United States are mainly to achieve fast scanning, high spatialtemporal resolution and high precision data acquisition. The purpose has been basically achieved. The volume scanning time of the radar is up to 10 s and the radar is updated. In close range, the resolution can reach 10 meters or even lower, which makes it possible to collect the fine structure and detailed continuous evolution of tornadoes. The development of radar in the United States adopts a variety of technical systems and scanning strategies, and the dual polarization, phased array, atmospheric imaging and other technologies are constantly improved and applied, with good results. Based on advanced radar, the United States has carried out a large number of tornado observation experiments, achieving rich results. The structure and evolution of tornadoes are described more and more precisely and accurately. Many achievements have been transformed into conceptual models, forming important tornado monitoring and forecasting indicators, early warning signals, and implemented in operations, improving the tornado early warning capability. The application of highfrequency and highprecision numerical models for tornado radar data has also significantly shortened the data assimilation period and improved the simulation ability of convective scale systems such as tornadoes. Referring to the successful experience of the United States, China should draw on its technical achievements, select the technical system for radar development as soon as possible, speed up the upgrading of operational radar technology and the development of highperformance tornado detection radar, organize tornado scientific observation experiments, collect fine tornado data, carry out scientific research, and explore the structure and activity regularity of tornadoes in China, providing a scientific support for the construction of tornado monitoring and warning.
2020, 46(2):257-268.
DOI: 10.7519/j.issn.10000526.2020.02.011
Abstract:
Weather modification operations in China has been carried out since 1958 with silver iodide as the main seeding agent. Whether silver iodide affects the environment has attracted much attention. This paper analyzed the content of silver ions in precipitation, soil and lakes after silver iodide seeding in several countries in the world. The amount of silver iodide used in China was counted, and silver ions in precipitation and in the reservoir were measured. It is found that the silver iodide used for weather modification in China do not affect water resources and the environment.
Weather modification operations in China has been carried out since 1958 with silver iodide as the main seeding agent. Whether silver iodide affects the environment has attracted much attention. This paper analyzed the content of silver ions in precipitation, soil and lakes after silver iodide seeding in several countries in the world. The amount of silver iodide used in China was counted, and silver ions in precipitation and in the reservoir were measured. It is found that the silver iodide used for weather modification in China do not affect water resources and the environment.
2020, 46(2):269-277.
DOI: 10.7519/j.issn.10000526.2020.02.012
Abstract:
The characteristics of heavy rainfall events on the Doppler weather radar velocity images and their early warning indicators in Xining from 2010 to 2016 are analyzed. The results show that the adverse wind region (AWR) on radial velocity images often occurs in the case of heavy rainfall events in Xining. TypeⅠAWR is slightly more for the mixed heavy rainfall and typeⅡAWR is mostly for the convective heavy rainfall during the directly affected heavy rainfall events. The AWR moves mostly northeastward in general. The occurring times of the AWR have certain lead times before the beginning of heavy rainfall events, and heavy rainfall falls near the AWR and its moving path, that is, the AWR is not only a timebased criterion for issuing early warnings of heavy precipitation but also a useful criterion for identifying falling areas of heavy rainfall. When the shear flow field in the AWR is convergent (divergent), it will enhance (weaken) the development of heavy rainfall, and the time of the convergence (divergence) is ahead of schedule the beginning (end) of heavy rainfall. At the time 1 h before the beginning of heavy rainfall, the vertical wind shear is the largest in low level and the smallest in middle level of the mixed heavy rainfall. However, it is obviously large in all the levels during convective heavy rainfall. The changes in wind direction mainly show deep and warm advection for the mixed heavy rainfall, while they are not obvious or there is warm advection in the low and middle levels for the convective heavy rainfall. The maximum echo heights and zero speed layers are higher for the convective heavy rainfall than for the mixed heavy rainfall, but there are smaller differences on the whole for the convective heavy rainfall. The indicators for early warning of heavy rainfall by comprehensive application of the radial velocity are obtained, and the accuracy rate reaches 78.6%.
The characteristics of heavy rainfall events on the Doppler weather radar velocity images and their early warning indicators in Xining from 2010 to 2016 are analyzed. The results show that the adverse wind region (AWR) on radial velocity images often occurs in the case of heavy rainfall events in Xining. TypeⅠAWR is slightly more for the mixed heavy rainfall and typeⅡAWR is mostly for the convective heavy rainfall during the directly affected heavy rainfall events. The AWR moves mostly northeastward in general. The occurring times of the AWR have certain lead times before the beginning of heavy rainfall events, and heavy rainfall falls near the AWR and its moving path, that is, the AWR is not only a timebased criterion for issuing early warnings of heavy precipitation but also a useful criterion for identifying falling areas of heavy rainfall. When the shear flow field in the AWR is convergent (divergent), it will enhance (weaken) the development of heavy rainfall, and the time of the convergence (divergence) is ahead of schedule the beginning (end) of heavy rainfall. At the time 1 h before the beginning of heavy rainfall, the vertical wind shear is the largest in low level and the smallest in middle level of the mixed heavy rainfall. However, it is obviously large in all the levels during convective heavy rainfall. The changes in wind direction mainly show deep and warm advection for the mixed heavy rainfall, while they are not obvious or there is warm advection in the low and middle levels for the convective heavy rainfall. The maximum echo heights and zero speed layers are higher for the convective heavy rainfall than for the mixed heavy rainfall, but there are smaller differences on the whole for the convective heavy rainfall. The indicators for early warning of heavy rainfall by comprehensive application of the radial velocity are obtained, and the accuracy rate reaches 78.6%.
13 Error Analysis on the Assessment Algorithm of Clearance Environment of Weather Radar Based on SRTM
2020, 46(2):278-282.
DOI: 10.7519/j.issn.10000526.2020.02.013
Abstract:
Shuttle Radar Topography Mission (SRTM) data were used to evaluate the clearance environment and the siteselection evaluation efficiency of radar was effectively improved. In this paper, the comparative experiment of weather radar clearance environment assessment is carried out by using manual measurement data and SRTM data. Error analysis of this method suggested that the evaluation algorithm of weather radar clearance environment based on SRTM was matching with the artificial measured data. The calculation error was significantly reduced when corrected with azimuth correction and distance correction algorithms.
Shuttle Radar Topography Mission (SRTM) data were used to evaluate the clearance environment and the siteselection evaluation efficiency of radar was effectively improved. In this paper, the comparative experiment of weather radar clearance environment assessment is carried out by using manual measurement data and SRTM data. Error analysis of this method suggested that the evaluation algorithm of weather radar clearance environment based on SRTM was matching with the artificial measured data. The calculation error was significantly reduced when corrected with azimuth correction and distance correction algorithms.
Mobile website
® 2024 All Rights Reserved
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
ISSN:1000-0526 CN:11-2282/P