ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 51,Issue 6,2025 Table of Contents
2025, 51(6):645-659.
DOI: 10.7519/j.issn.1000-0526.2024.122602
Abstract:
This study investigates the evolution mechanism of a long-life convective-scale updraft in outer rainband of numerically simulated sheared tropical cyclone (TC). The updraft originates from the down-shear right quadrant of outer rainband within a sheared TC with a lifespan of 2.5 h. This updraft undergoes two strengthening processes and displays complex evolutionary characteristics with two peaks in vertical mass transport. The results show that strong localized vertical wind shear and low-level high-value equivalent potential temperature are the main favorable ambient factors for an updraft long lifespan. The strengthening and weakening of neighboring convective cells lead to different responses to updraft intensity by adjusting the variation of local equivalent potential temperature. The vertical momentum budget suggests that an updraft grows when it is dominated by positive buoyancy pressure gradient acceleration and positive thermal buoyancy, but there exist differences between the two strengthening mechanisms. In the first strengthening stage, the development of neighboring convective cells causes the rise in the equivalent potential temperature at lower levels. Moreover, the increase in updraft tilt and the latent heating lead to a significant increase in thermal buoyancy, resulting in a larger vertical velocity. In the early second strengthening stage, the occurrence and development of new convective cells in the vicinity of the focused updraft induce the rise in localized equivalent potential temperature. Subsequently, however, the mature and dissipation of these neighboring convective cells lead to the strengthened downward motion and the decreased localized equivalent potential temperature, which makes smaller thermal buoyancy and smaller vertical velocity. Analogous to the weakening mechanism of convective cells in mid-latitudes, during the weakening phase, the focused updraft exhibits a decrease in tilt, and then forces a downdraft directly beneath it. This downdraft and downdrafts of neighboring convective cells carry low-value equivalent potential temperature toward the lower layers, forming a surface cold pool. Consequently, thermal buoyancy tends to decrease suppressing the growth of the focused updraft. In addition, the negative contribution of water loading is harmful to the development of the focused updraft. The imbalance among thermal buoyancy, buoyancy pressure gradient acceleration, and water loading constitutes the primary physical mechanism responsible for the prolonged evolution of updraft. At the same time, a tilted updraft structure can also influence the development of updraft.
This study investigates the evolution mechanism of a long-life convective-scale updraft in outer rainband of numerically simulated sheared tropical cyclone (TC). The updraft originates from the down-shear right quadrant of outer rainband within a sheared TC with a lifespan of 2.5 h. This updraft undergoes two strengthening processes and displays complex evolutionary characteristics with two peaks in vertical mass transport. The results show that strong localized vertical wind shear and low-level high-value equivalent potential temperature are the main favorable ambient factors for an updraft long lifespan. The strengthening and weakening of neighboring convective cells lead to different responses to updraft intensity by adjusting the variation of local equivalent potential temperature. The vertical momentum budget suggests that an updraft grows when it is dominated by positive buoyancy pressure gradient acceleration and positive thermal buoyancy, but there exist differences between the two strengthening mechanisms. In the first strengthening stage, the development of neighboring convective cells causes the rise in the equivalent potential temperature at lower levels. Moreover, the increase in updraft tilt and the latent heating lead to a significant increase in thermal buoyancy, resulting in a larger vertical velocity. In the early second strengthening stage, the occurrence and development of new convective cells in the vicinity of the focused updraft induce the rise in localized equivalent potential temperature. Subsequently, however, the mature and dissipation of these neighboring convective cells lead to the strengthened downward motion and the decreased localized equivalent potential temperature, which makes smaller thermal buoyancy and smaller vertical velocity. Analogous to the weakening mechanism of convective cells in mid-latitudes, during the weakening phase, the focused updraft exhibits a decrease in tilt, and then forces a downdraft directly beneath it. This downdraft and downdrafts of neighboring convective cells carry low-value equivalent potential temperature toward the lower layers, forming a surface cold pool. Consequently, thermal buoyancy tends to decrease suppressing the growth of the focused updraft. In addition, the negative contribution of water loading is harmful to the development of the focused updraft. The imbalance among thermal buoyancy, buoyancy pressure gradient acceleration, and water loading constitutes the primary physical mechanism responsible for the prolonged evolution of updraft. At the same time, a tilted updraft structure can also influence the development of updraft.
2025, 51(6):660-674.
DOI: 10.7519/j.issn.1000-0526.2025.011604
Abstract:
Targeting the extremely severe rainstorms caused by three landfall typhoons in Fujian, i.e. Haikui (No.2311), Doksuri (No.2305) and Megi (No.1617), 〖JP2〗and employing the multi-source data including the surface automatic weather station data, the best typhoon track data and the ERA5 and GDAS reanalysis data, as well as the HYSPLIT 5.0 trajectory model which was built by the Lagrangian method, this article quantitatively analyzes the cold air and water vapor transport pathways and their contribution rates from different sources. Besides, the impacts of cold air intensity, warm-cold interaction mechanism and water vapor transport on the extreme rainfall are compared. The results show that variations in cold air inten-sity, pathways and water vapor transport in the lower troposphere led to the differences in the rainfall area and intensity of the typhoon extreme rainfall events. Under the influence of the denatured cold air from Mongolia, the extreme rainfall triggered by Typhoon Haikui exhibited a zonal distribution pattern aligned with the easterly wind. For Typhoon Megi, it had the weak cold airs from the eastern and western pathways originated respectively from the east and central regions of West Siberia. Influenced by the weak cold airs, the extreme rainfall area was distributed along the typhoon inverted trough in the meridional direction. In contrast, there was no cold air invading the peripheral circulation of Typhoon Doksuri, but driven by the persistent “train effect” in the rainband behind the typhoon, extreme rainfall area of “Doksuri” presented a meridional distribution pattern along a southwesterly jet. The analysis on water vapor transport reveals that the water vapor supplies for “Haikui” and “Doksuri” were mainly from the South China Sea and western Pacific channels, with water vapor contribution rates of 90.4% and 100%, respectively, which resulted in the exceptionally intense rainfall events. However, for Typhoon Megi, the low moisture contributions (25.5%) from the South China Sea and western Pacific were the major reasons for the lowest rainfall intensity among the three typhoons, but the much broader cold air influence expanded the affected-area of the extremely heavy rainfall.
Targeting the extremely severe rainstorms caused by three landfall typhoons in Fujian, i.e. Haikui (No.2311), Doksuri (No.2305) and Megi (No.1617), 〖JP2〗and employing the multi-source data including the surface automatic weather station data, the best typhoon track data and the ERA5 and GDAS reanalysis data, as well as the HYSPLIT 5.0 trajectory model which was built by the Lagrangian method, this article quantitatively analyzes the cold air and water vapor transport pathways and their contribution rates from different sources. Besides, the impacts of cold air intensity, warm-cold interaction mechanism and water vapor transport on the extreme rainfall are compared. The results show that variations in cold air inten-sity, pathways and water vapor transport in the lower troposphere led to the differences in the rainfall area and intensity of the typhoon extreme rainfall events. Under the influence of the denatured cold air from Mongolia, the extreme rainfall triggered by Typhoon Haikui exhibited a zonal distribution pattern aligned with the easterly wind. For Typhoon Megi, it had the weak cold airs from the eastern and western pathways originated respectively from the east and central regions of West Siberia. Influenced by the weak cold airs, the extreme rainfall area was distributed along the typhoon inverted trough in the meridional direction. In contrast, there was no cold air invading the peripheral circulation of Typhoon Doksuri, but driven by the persistent “train effect” in the rainband behind the typhoon, extreme rainfall area of “Doksuri” presented a meridional distribution pattern along a southwesterly jet. The analysis on water vapor transport reveals that the water vapor supplies for “Haikui” and “Doksuri” were mainly from the South China Sea and western Pacific channels, with water vapor contribution rates of 90.4% and 100%, respectively, which resulted in the exceptionally intense rainfall events. However, for Typhoon Megi, the low moisture contributions (25.5%) from the South China Sea and western Pacific were the major reasons for the lowest rainfall intensity among the three typhoons, but the much broader cold air influence expanded the affected-area of the extremely heavy rainfall.
2025, 51(6):675-685.
DOI: 10.7519/j.issn.1000-0526.2025.020101
Abstract:
A statistical analysis of the characteristic of typhoon track deflection relative to the steering flow in East China is conducted with the CMA tropical cyclone best track dataset and the ECMWF ERA5 reanalysis data from 1950 to 2022. The results show that 85.2% of 54 landfall typhoons’ tracks deviate to the left of the steering flow at the time of landfall, and the coastal terrain can produce an averaged deflection angle of about 6°-7° from the steering flow. The deflection angle between the typhoon tracks and the steering flow at the landfall time has a good correspondence with the thermal asymmetry parameters. Generally, a cyclone with a nearly thermal symmetric structure at the time of landfall corresponds to a smaller deflection angle, while the obvious thermal asymmetric structure would increase the possibility of a large deflection angle. The coastal terrain is prone to triggering asymmetric convection on the left side of the cyclone near the landfall, affecting the distribution of thermal structure and causing the typhoon tracks to deviate to the left of the steering flow. The development of convection on the left side of the cyclone can sometimes decrease the thermal asymmetry parameter at the time of landfall. So, more attention should be paid to the evolution of thermal asymmetry near the landfall instead of the asymmetry itself for more accurate prediction of typhoon track deflection.
A statistical analysis of the characteristic of typhoon track deflection relative to the steering flow in East China is conducted with the CMA tropical cyclone best track dataset and the ECMWF ERA5 reanalysis data from 1950 to 2022. The results show that 85.2% of 54 landfall typhoons’ tracks deviate to the left of the steering flow at the time of landfall, and the coastal terrain can produce an averaged deflection angle of about 6°-7° from the steering flow. The deflection angle between the typhoon tracks and the steering flow at the landfall time has a good correspondence with the thermal asymmetry parameters. Generally, a cyclone with a nearly thermal symmetric structure at the time of landfall corresponds to a smaller deflection angle, while the obvious thermal asymmetric structure would increase the possibility of a large deflection angle. The coastal terrain is prone to triggering asymmetric convection on the left side of the cyclone near the landfall, affecting the distribution of thermal structure and causing the typhoon tracks to deviate to the left of the steering flow. The development of convection on the left side of the cyclone can sometimes decrease the thermal asymmetry parameter at the time of landfall. So, more attention should be paid to the evolution of thermal asymmetry near the landfall instead of the asymmetry itself for more accurate prediction of typhoon track deflection.
2025, 51(6):686-699.
DOI: 10.7519/j.issn.1000-0526.2025.012301
Abstract:
An extreme torrential rain event caused by highly organized severe rainfall mesoscale convection system (MCS) occurred in Yichang on 22 April 2018. Based on conventional observation data, observation data from regional automatic weather stations, radar data and ERA5 reanalysis data, we analyze the organizational characteristics and formation mechanism of extreme severe rainfall MCS. The results are as follows. This extreme torrential rain event occurred under the background of weak forcing at high level and weak forcing turning into strong forcing at low level, accompanied by strong frontogenesis. High temperature, high humidity and extremely unstable atmospheric environment were conducive to the occurrence of the extreme severe rainfall. The warm and wet easterly air at low level was forced to lift by the C-pattern terrain in the east of Yichang, triggering the severe rainfall echoes in the transition area from mountain to plain. The warm and wet southeasterly or easterly wind at top of the boundary-layer reverted warm trough caused the dispersed flocculent convection in the plain area from Yidu to Gongan. The organization of extreme severe rainfall MCS experienced merging stage and vortex stage. Under the influence of weak synoptic-scale forcing, MCS in the mountain-to-plain transition area spread to southeast along the low-lying terrain, and merged along three paths with the warm area flocculent echoes from the plain to north. The east-west MCS formed by the low-level east-west frontal zone and the surface convergence line moved toward west under the guidance of the middle and low level easterly jet, and continuously merged with the south-north MCS in the mountain-to-plain transition area peristently, resulting in the heaviest precipitation stage.The mesoscale cyclonic circulation, composed of MCS cold outflow and ambient airflow, and the latent heat of severe rainfall that heated the middle atmosphere favored the organization, development and strengthening of vortex MCS. The water vapor energy transport of the low-level warm and wet easterly jet was beneficial to the long-time maintenance of the vortex MCS. The extreme severe rainfall mainly occurred in the merging stage and the long-time vortex stage of MCS. Synoptic-scale system forcing, low-level strong frontogenesis, mesoscale topography and positive feedback of mesoscale weather system were the important causes of the formation for this extreme severe rainfall.
An extreme torrential rain event caused by highly organized severe rainfall mesoscale convection system (MCS) occurred in Yichang on 22 April 2018. Based on conventional observation data, observation data from regional automatic weather stations, radar data and ERA5 reanalysis data, we analyze the organizational characteristics and formation mechanism of extreme severe rainfall MCS. The results are as follows. This extreme torrential rain event occurred under the background of weak forcing at high level and weak forcing turning into strong forcing at low level, accompanied by strong frontogenesis. High temperature, high humidity and extremely unstable atmospheric environment were conducive to the occurrence of the extreme severe rainfall. The warm and wet easterly air at low level was forced to lift by the C-pattern terrain in the east of Yichang, triggering the severe rainfall echoes in the transition area from mountain to plain. The warm and wet southeasterly or easterly wind at top of the boundary-layer reverted warm trough caused the dispersed flocculent convection in the plain area from Yidu to Gongan. The organization of extreme severe rainfall MCS experienced merging stage and vortex stage. Under the influence of weak synoptic-scale forcing, MCS in the mountain-to-plain transition area spread to southeast along the low-lying terrain, and merged along three paths with the warm area flocculent echoes from the plain to north. The east-west MCS formed by the low-level east-west frontal zone and the surface convergence line moved toward west under the guidance of the middle and low level easterly jet, and continuously merged with the south-north MCS in the mountain-to-plain transition area peristently, resulting in the heaviest precipitation stage.The mesoscale cyclonic circulation, composed of MCS cold outflow and ambient airflow, and the latent heat of severe rainfall that heated the middle atmosphere favored the organization, development and strengthening of vortex MCS. The water vapor energy transport of the low-level warm and wet easterly jet was beneficial to the long-time maintenance of the vortex MCS. The extreme severe rainfall mainly occurred in the merging stage and the long-time vortex stage of MCS. Synoptic-scale system forcing, low-level strong frontogenesis, mesoscale topography and positive feedback of mesoscale weather system were the important causes of the formation for this extreme severe rainfall.
2025, 51(6):700-710.
DOI: 10.7519/j.issn.1000-0526.2025.010203
Abstract:
By using ERA5 reanalysis data, and the surface automatic weather station, lightning locator, S-band dual-polarization radar and X-band phased array radar data, we analyze the ambient conditions and severe storm structure of the elevated thunderstorm that triggered localized hail in Zhejiang Province on 21 February 2024. The results show that the thunderstorm developed in front of the high-altitude southern trough and behind the surface cold front. The stratification configuration was “cold and wet-warm and wet-cold and dry” from bottom to top, and the low-level stratification was neutral and stable, so it was a typical elevated thunderstorm. During the process of thunderstorm activity, there were convective instability and symmetric instability in the middle layer, and the warm and wet air climbed along the cold air cushion, rapidly creating deep and strong vertical convection on the top of the inversion layer.The updraft center was in the middle troposphere behind the front. The storm moved on the side of the cold air, and the forward unstable area led to the continuous development of the storm. With the increasing height of the centroid and the strengthening updraft, the intracloud lightning above the 0℃ layer occurred much more frequently, causing the increase of solid hydrocondensate particles, which was conducive to the formation of hail. The dense area of intracloud lightning showed a good consistency with the hail falling area. The X-band phased array radar showed that the core of horizontal reflectivity factor of the hail cell was initially located above the 0℃ layer. The solid hydrocondensate particles in the core partially melt when passing through the warm and wet layer during their falling down, and then rapidly cooled down when through the cold cushion, partially frozen. In the end, they fell to the surface as rain mixed with hail.
By using ERA5 reanalysis data, and the surface automatic weather station, lightning locator, S-band dual-polarization radar and X-band phased array radar data, we analyze the ambient conditions and severe storm structure of the elevated thunderstorm that triggered localized hail in Zhejiang Province on 21 February 2024. The results show that the thunderstorm developed in front of the high-altitude southern trough and behind the surface cold front. The stratification configuration was “cold and wet-warm and wet-cold and dry” from bottom to top, and the low-level stratification was neutral and stable, so it was a typical elevated thunderstorm. During the process of thunderstorm activity, there were convective instability and symmetric instability in the middle layer, and the warm and wet air climbed along the cold air cushion, rapidly creating deep and strong vertical convection on the top of the inversion layer.The updraft center was in the middle troposphere behind the front. The storm moved on the side of the cold air, and the forward unstable area led to the continuous development of the storm. With the increasing height of the centroid and the strengthening updraft, the intracloud lightning above the 0℃ layer occurred much more frequently, causing the increase of solid hydrocondensate particles, which was conducive to the formation of hail. The dense area of intracloud lightning showed a good consistency with the hail falling area. The X-band phased array radar showed that the core of horizontal reflectivity factor of the hail cell was initially located above the 0℃ layer. The solid hydrocondensate particles in the core partially melt when passing through the warm and wet layer during their falling down, and then rapidly cooled down when through the cold cushion, partially frozen. In the end, they fell to the surface as rain mixed with hail.
2025, 51(6):711-723.
DOI: 10.7519/j.issn.1000-0526.2025.032001
Abstract:
Using autumn precipitation data from 373 meteorological observation stations in West China from 1961 to 2022 and ERA5 daily reanalysis data provided by the European Centre for Medium-Range Weather Forecasts， this article analyzes the latest changes in the characteristics of both persistent and non-persistent types of extreme precipitation events during the autumn rain period in West China. At the same time, the circulation characteristics and differences of these two types of events are disussed from the perspective of the major atmospheric circulation systems. The results are as follows. The persistent extreme precipitation events show an increasing trend in precipitation amount, frequency and intensity, and contribute more to total autumn precipitation in West China over the past 62 years. In contrast, the non-persistent extreme precipitation events have a decrease in precipitation amount, with no significant change in precipitation intensity, frequency and contribution to total precipitation. When the two types of extreme precipitation events occur, the circulation pattern in the mid-high latitudes of the Northern Hemisphere of Eurasia typically consists of two troughs and a ridge, with the positions of the troughs and ridge being essentially consistent, but they have considerable differences in intensity. During persistent (non-persistent) extreme precipitation events, the trough north of Black Sea and Caspian Sea, the ridge north of Lakes Balkhash and Baikal, and the trough north and east of the Sea of Okhotsk are stronger (weaker). In the low-latitude areas, the Indo-Burma trough is stronger (relatively weaker), and the position of the Western Pacific subtropical high is more northward and westward (relatively southward and eastward). In the process of persistent extreme precipitation events during the autumn rain period in West China, in addition to the highly favorable background of large-scale circulation in the middle and lower troposphere, the northern boundary of the South Asian high retreats southward and eastward earlier, and the subtropical westerly jet stream builds up and develops. Therefore, early attention and monitoring of changes in the moving path and pattern of the South Asian high and changes in the subtropical westerly jet stream, can provide precursor information for early prediction of persistent extreme precipitation events.
Using autumn precipitation data from 373 meteorological observation stations in West China from 1961 to 2022 and ERA5 daily reanalysis data provided by the European Centre for Medium-Range Weather Forecasts， this article analyzes the latest changes in the characteristics of both persistent and non-persistent types of extreme precipitation events during the autumn rain period in West China. At the same time, the circulation characteristics and differences of these two types of events are disussed from the perspective of the major atmospheric circulation systems. The results are as follows. The persistent extreme precipitation events show an increasing trend in precipitation amount, frequency and intensity, and contribute more to total autumn precipitation in West China over the past 62 years. In contrast, the non-persistent extreme precipitation events have a decrease in precipitation amount, with no significant change in precipitation intensity, frequency and contribution to total precipitation. When the two types of extreme precipitation events occur, the circulation pattern in the mid-high latitudes of the Northern Hemisphere of Eurasia typically consists of two troughs and a ridge, with the positions of the troughs and ridge being essentially consistent, but they have considerable differences in intensity. During persistent (non-persistent) extreme precipitation events, the trough north of Black Sea and Caspian Sea, the ridge north of Lakes Balkhash and Baikal, and the trough north and east of the Sea of Okhotsk are stronger (weaker). In the low-latitude areas, the Indo-Burma trough is stronger (relatively weaker), and the position of the Western Pacific subtropical high is more northward and westward (relatively southward and eastward). In the process of persistent extreme precipitation events during the autumn rain period in West China, in addition to the highly favorable background of large-scale circulation in the middle and lower troposphere, the northern boundary of the South Asian high retreats southward and eastward earlier, and the subtropical westerly jet stream builds up and develops. Therefore, early attention and monitoring of changes in the moving path and pattern of the South Asian high and changes in the subtropical westerly jet stream, can provide precursor information for early prediction of persistent extreme precipitation events.
2025, 51(6):724-734.
DOI: 10.7519/j.issn.1000-0526.2025.011301
Abstract:
Based on the prediction results of Beijing Climate Center-Climate Prediction System version 3-Subseasonal to Seasonal version 2 (BCC-CPSv3-S2Sv2), various evaluation and test methods are used to test the prediction effect of the model in the flood season across the Yangtze River Basin, and to evaluate the prediction skills of subseasonal daily/dekad precipitation in the flood season in the Yangtze River Basin. The model error characteristics and the available prediction lead time of model precipitation are analyzed. The results show that the model systematically overestimates the precipitation in flood season in the Yangtze River Basin as a whole, and its prediction skill in the middle and lower reaches of the Yangtze River is higher than that in the upper reaches of the Yangtze River. The dekad prediction skill of the model is improved with the initial time approaching, but the BS predicted 5 d ahead is better than that predicted 1 d ahead. The effective prediction time of the model for the daily quantitative prediction in the flood season in the Yangtze River Basin is about ten days, and its qualitative prediction of the precipitation anomaly in the flood season is similar. The skill of model prediction 1 dekad ahead is obviously higher than that 2 dekads ahead. The analysis results of the probabilistic prediction of precipitation anomalies during the flood season show that the prediction 2 to 3 dekads ahead also has some reference values. In addition, the prediction skill of model under less rain scenario is better than that under excessive rain scenario. There is still much room for improving the prediction capability for the moderate rainfall and above.
Based on the prediction results of Beijing Climate Center-Climate Prediction System version 3-Subseasonal to Seasonal version 2 (BCC-CPSv3-S2Sv2), various evaluation and test methods are used to test the prediction effect of the model in the flood season across the Yangtze River Basin, and to evaluate the prediction skills of subseasonal daily/dekad precipitation in the flood season in the Yangtze River Basin. The model error characteristics and the available prediction lead time of model precipitation are analyzed. The results show that the model systematically overestimates the precipitation in flood season in the Yangtze River Basin as a whole, and its prediction skill in the middle and lower reaches of the Yangtze River is higher than that in the upper reaches of the Yangtze River. The dekad prediction skill of the model is improved with the initial time approaching, but the BS predicted 5 d ahead is better than that predicted 1 d ahead. The effective prediction time of the model for the daily quantitative prediction in the flood season in the Yangtze River Basin is about ten days, and its qualitative prediction of the precipitation anomaly in the flood season is similar. The skill of model prediction 1 dekad ahead is obviously higher than that 2 dekads ahead. The analysis results of the probabilistic prediction of precipitation anomalies during the flood season show that the prediction 2 to 3 dekads ahead also has some reference values. In addition, the prediction skill of model under less rain scenario is better than that under excessive rain scenario. There is still much room for improving the prediction capability for the moderate rainfall and above.
2025, 51(6):735-743.
DOI: 10.7519/j.issn.1000-0526.2025.021401
Abstract:
Multiple key factors affect the accuracy of weather radar reflectivity factor measurement. Among them, radar transmission power is the key variable that is most prone to fluctuation in radar performance parameters, affecting the accuracy of radar measurement. The dynamic range of the receiver is a key indicator for measuring the stability of the receiving channel, and directly impacts the measurement results of reflectivity factor. An excellent weather radar system should have functions such as online monitoring, calibration and correction of key performance parameters. This paper statistically analyzes data samples collected over the years 2020-2024 from 12 networked CINRAD/SA-D radars in Guangdong, and tests the effectiveness of CINRAD/SA-D radar reflectivity factor calibration and online correction. The necessity of offline calibration of networked radar is demonstrated through the comparison and stability analysis of key performance parameters. Additionally, the first volume scan data collected when the radar is powered on can easily have quality problems, which should be paid attention to in radar maintenance and data application. So, we recommend that the mechanism and flow of this kind of weather radar reflectivity factor calibration be used for the phased array weather radars.
Multiple key factors affect the accuracy of weather radar reflectivity factor measurement. Among them, radar transmission power is the key variable that is most prone to fluctuation in radar performance parameters, affecting the accuracy of radar measurement. The dynamic range of the receiver is a key indicator for measuring the stability of the receiving channel, and directly impacts the measurement results of reflectivity factor. An excellent weather radar system should have functions such as online monitoring, calibration and correction of key performance parameters. This paper statistically analyzes data samples collected over the years 2020-2024 from 12 networked CINRAD/SA-D radars in Guangdong, and tests the effectiveness of CINRAD/SA-D radar reflectivity factor calibration and online correction. The necessity of offline calibration of networked radar is demonstrated through the comparison and stability analysis of key performance parameters. Additionally, the first volume scan data collected when the radar is powered on can easily have quality problems, which should be paid attention to in radar maintenance and data application. So, we recommend that the mechanism and flow of this kind of weather radar reflectivity factor calibration be used for the phased array weather radars.
2025, 51(6):744-755.
DOI: 10.7519/j.issn.1000-0526.2024.111501
Abstract:
A meteorological early warning method for mountain torrent disasters is proposed using the fuzzy evaluation method in this paper. The method is based on the dynamic critical rainfall for mountain torrent early warning that considers soil water content saturation, then a correspondence between meteorological warning levels and fuzzy scores for mountain torrent disasters is established based on the fuzzy evaluation method. Equal weight averaging and weighting algorithms constructed based on the coefficient of determination or the relative error of peak flow are respectively adopted. With this method, together with the comprehensive fuzzy scores for meteorological warning calculated by using the precipitation forecasts from CMA-MESO, CMA-SH9, CMA-BJ and intelligent grid forecasting， the meteorological early warning level is determined. The results show that the hit rate of the meteorological early warning results based on the fuzzy evaluation method is comparable to that of the CMA-BJ and higher than other models, the miss rate and false alarm rate are also comparable to those of the CMA-BJ and lower than other models, the TS scores are all higher than those of other models, through the application and verification of the mountain torrent disaster in Hengshui of Anyang River from 17 to 22 July 2021. This method can extend the lead time of mountain torrent prediction and improve the accuracy of early warning.
A meteorological early warning method for mountain torrent disasters is proposed using the fuzzy evaluation method in this paper. The method is based on the dynamic critical rainfall for mountain torrent early warning that considers soil water content saturation, then a correspondence between meteorological warning levels and fuzzy scores for mountain torrent disasters is established based on the fuzzy evaluation method. Equal weight averaging and weighting algorithms constructed based on the coefficient of determination or the relative error of peak flow are respectively adopted. With this method, together with the comprehensive fuzzy scores for meteorological warning calculated by using the precipitation forecasts from CMA-MESO, CMA-SH9, CMA-BJ and intelligent grid forecasting， the meteorological early warning level is determined. The results show that the hit rate of the meteorological early warning results based on the fuzzy evaluation method is comparable to that of the CMA-BJ and higher than other models, the miss rate and false alarm rate are also comparable to those of the CMA-BJ and lower than other models, the TS scores are all higher than those of other models, through the application and verification of the mountain torrent disaster in Hengshui of Anyang River from 17 to 22 July 2021. This method can extend the lead time of mountain torrent prediction and improve the accuracy of early warning.
2025, 51(6):756-762.
DOI: 10.7519/j.issn.1000-0526.2024.102401
Abstract:
The data of asthmatic children in the Maternity and Child Health Care Hospital of Inner Mongolia Autonomous Region and meteorological elements from 2020 to 2022 and the distributed lag nonlinear model (DLNM) are used to explore the influence of meteorological elements on outpatient and emergency visits of asthmatic children in Hohhot during 2020－2022. The results show that the average monthly number of visits of asthmatic children in the Maternity and Child Health Care Hospital of Inner Mongolia Autonomous Region was 36.17 from 2020 to 2022, and the visits of children with asthma in three years occurred roughly in three peak periods, from December to next January, May to June and August to September, respectively. The Pearson relation analysis reveals that the number of monthly visits of asthmatic children to the hospital was positively associated with temperature and precipitation. The DLNM shows a hazard effect of precipitation on increased clinic visits of asthmatic children, reaching a maximum at the lag order 1, that is, the number of asthmatic children in outpatient and emergency department increases with the increased temperature and precipitation. Precipitation has the risk of lagging outpatient and emergency visits for children with asthma.
The data of asthmatic children in the Maternity and Child Health Care Hospital of Inner Mongolia Autonomous Region and meteorological elements from 2020 to 2022 and the distributed lag nonlinear model (DLNM) are used to explore the influence of meteorological elements on outpatient and emergency visits of asthmatic children in Hohhot during 2020－2022. The results show that the average monthly number of visits of asthmatic children in the Maternity and Child Health Care Hospital of Inner Mongolia Autonomous Region was 36.17 from 2020 to 2022, and the visits of children with asthma in three years occurred roughly in three peak periods, from December to next January, May to June and August to September, respectively. The Pearson relation analysis reveals that the number of monthly visits of asthmatic children to the hospital was positively associated with temperature and precipitation. The DLNM shows a hazard effect of precipitation on increased clinic visits of asthmatic children, reaching a maximum at the lag order 1, that is, the number of asthmatic children in outpatient and emergency department increases with the increased temperature and precipitation. Precipitation has the risk of lagging outpatient and emergency visits for children with asthma.
2025, 51(6):763-772.
DOI: 10.7519/j.issn.1000-0526.2025.061701
Abstract:
The main characteristics of the general atmospheric circulation in March 2025 are as follows: The Northern Hemisphere polar vortex exhibited a multi-type distribution with enhanced intensity. The mid-high latitude circulation presented a four-wave pattern, while the Asian circulation remained relatively zonal. The southern branch trough was stronger than normal. The national average temperature was 5.3℃, 0.5℃ higher than that in the same period of years. The national average precipitation was 28.3 mm, 3.7% lower than normal overall. The precipitation was mainly concentrated in the Yellow River and Huaihe River (Huanghuai) Region, the area south of the Yangtze River Region, South China and other places, while northern China received more precipitation than normal. During the month, there were two heavy precipitation events, three severe convections, two cold air episodes and four sand-dust weather processes in total. Among them, the cold air processes featured a wide range of impacts and a large cooling range. At the beginning of March, influenced by a cold wave, a severe snowstorm occurred in Shandong and the first severe convective weather event of the year took place in the Jiangnan and South China regions. Afterwards the sand-dust process at the end of the month incurred widespread strong sandstorm weather.
The main characteristics of the general atmospheric circulation in March 2025 are as follows: The Northern Hemisphere polar vortex exhibited a multi-type distribution with enhanced intensity. The mid-high latitude circulation presented a four-wave pattern, while the Asian circulation remained relatively zonal. The southern branch trough was stronger than normal. The national average temperature was 5.3℃, 0.5℃ higher than that in the same period of years. The national average precipitation was 28.3 mm, 3.7% lower than normal overall. The precipitation was mainly concentrated in the Yellow River and Huaihe River (Huanghuai) Region, the area south of the Yangtze River Region, South China and other places, while northern China received more precipitation than normal. During the month, there were two heavy precipitation events, three severe convections, two cold air episodes and four sand-dust weather processes in total. Among them, the cold air processes featured a wide range of impacts and a large cooling range. At the beginning of March, influenced by a cold wave, a severe snowstorm occurred in Shandong and the first severe convective weather event of the year took place in the Jiangnan and South China regions. Afterwards the sand-dust process at the end of the month incurred widespread strong sandstorm weather.
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ISSN:1000-0526 CN:11-2282/P