ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 51,Issue 2,2025 Table of Contents
2025, 51(2):129-142.
DOI: 10.7519/j.issn.1000-0526.2024.122201
Abstract:
The fuzzy logic method has been widely used and continuously improved in the classification and recognition of echoes such as ground clutter of weather radars, and has become the mainstream technology type for non-precipitation echo recognition processing of operational weather radar systems in various countries. This paper introduces the basic principle of fuzzy logic method for clutter recognition, sorts out the evolution and application of fuzzy logic method in ground clutter recognition of weather radar, and then looks into the future’s development direction and application value of this field so as to provide some references for further promoting the development of ground clutter recognition and suppression technology of weather radar.
The fuzzy logic method has been widely used and continuously improved in the classification and recognition of echoes such as ground clutter of weather radars, and has become the mainstream technology type for non-precipitation echo recognition processing of operational weather radar systems in various countries. This paper introduces the basic principle of fuzzy logic method for clutter recognition, sorts out the evolution and application of fuzzy logic method in ground clutter recognition of weather radar, and then looks into the future’s development direction and application value of this field so as to provide some references for further promoting the development of ground clutter recognition and suppression technology of weather radar.
2025, 51(2):143-152.
DOI: 10.7519/j.issn.1000-0526.2024.071501
Abstract:
Observational researches of aerosols and cloud microphysics have been carried out by means of aircraft carrying cloud physics detection instruments for many years in Hebei Province, China. A series of research results have been obtained and published in the fields of aerosols, cloud condensation nuclei (CCN), clouds and precipitation macro and micro structure characteristics, especially some weather modification catalytic experiments by aircraft. In this paper, the research progresses of aerosols and cloud precipitation physical observations over Hebei Province in the recent 20 years are systematically summarized. The microphysical characteristics of aerosols, CCN and clouds, such as vertical structure, spatial distribution and seasonal variation, are summarized. Four observation field campaigns for aircraft precipitation enhancement operation and the effect test are introduced in detail. The physical evidence of macro and micro physical characteristic changes in the supercooled water area before and after cloud catalysis is objectively demonstrated. In addition, the future development direction is put forward on the basis of summarizing a large number of research results, with some suggestions for aerosol-cloud physical aircraft observation and weather modification activities through aircraft catalysis in North China.
Observational researches of aerosols and cloud microphysics have been carried out by means of aircraft carrying cloud physics detection instruments for many years in Hebei Province, China. A series of research results have been obtained and published in the fields of aerosols, cloud condensation nuclei (CCN), clouds and precipitation macro and micro structure characteristics, especially some weather modification catalytic experiments by aircraft. In this paper, the research progresses of aerosols and cloud precipitation physical observations over Hebei Province in the recent 20 years are systematically summarized. The microphysical characteristics of aerosols, CCN and clouds, such as vertical structure, spatial distribution and seasonal variation, are summarized. Four observation field campaigns for aircraft precipitation enhancement operation and the effect test are introduced in detail. The physical evidence of macro and micro physical characteristic changes in the supercooled water area before and after cloud catalysis is objectively demonstrated. In addition, the future development direction is put forward on the basis of summarizing a large number of research results, with some suggestions for aerosol-cloud physical aircraft observation and weather modification activities through aircraft catalysis in North China.
2025, 51(2):153-166.
DOI: 10.7519/j.issn.1000-0526.2024.122202
Abstract:
The CMA Earth System Modeling and Prediction Centre is currently developing a regional ensemble prediction system with a horizontal resolution of 3 km. In view of the intricate terrain and meteorological conditions in Southwest China, coupled with the limited efficacy of the precipitation forecast products from the CMA regional model in this particular area, it is intended to place a significant emphasis on the impact of enhancing the horizontal resolution of the CMA regional ensemble prediction system on the precipitation forecast performance for the southwestern region during the research and development phase. Considering the aforementioned, this study, grounded in the CMA regional ensemble prediction system, has formulated two ensemble forecast tests with horizontal resolutions of 3 km and 10 km, respectively. Focusing on the recurrent precipitation events in the western Sichuan Basin during August 2020, a 25-day continuous test was executed. The experimental results were subsequently evaluated and comparatively analyzed. The findings reveal that the augmentation of horizontal resolution contributes significantly to the escalation of perturbation energy within the vertical layers of the troposphere, and it facilitates a more precise delineation of the forecast uncertainties associated with mesoscale and smaller-scale waves. Evaluation based on isobaric surfaces and ground meteorological parameters demonstrates that increasing the horizontal resolution helps to amplify the ensemble spread, improve the probabilistic forecasting skill for wind field, temperature and precipitation, and elevate the precision of precipitation forecases. Nonetheless, the 3 km ensemble prediction system still faces the problem of insufficient ensemble spread. The analysis of a heavy rainfall event shows that increasing the horizontal resolution facilitates more detailed simulation of multi-scale terrain and more accurate depiction of water vapor and dynamic structure in the rainstorm area, which in turn elevates the forecast performance for this event.
The CMA Earth System Modeling and Prediction Centre is currently developing a regional ensemble prediction system with a horizontal resolution of 3 km. In view of the intricate terrain and meteorological conditions in Southwest China, coupled with the limited efficacy of the precipitation forecast products from the CMA regional model in this particular area, it is intended to place a significant emphasis on the impact of enhancing the horizontal resolution of the CMA regional ensemble prediction system on the precipitation forecast performance for the southwestern region during the research and development phase. Considering the aforementioned, this study, grounded in the CMA regional ensemble prediction system, has formulated two ensemble forecast tests with horizontal resolutions of 3 km and 10 km, respectively. Focusing on the recurrent precipitation events in the western Sichuan Basin during August 2020, a 25-day continuous test was executed. The experimental results were subsequently evaluated and comparatively analyzed. The findings reveal that the augmentation of horizontal resolution contributes significantly to the escalation of perturbation energy within the vertical layers of the troposphere, and it facilitates a more precise delineation of the forecast uncertainties associated with mesoscale and smaller-scale waves. Evaluation based on isobaric surfaces and ground meteorological parameters demonstrates that increasing the horizontal resolution helps to amplify the ensemble spread, improve the probabilistic forecasting skill for wind field, temperature and precipitation, and elevate the precision of precipitation forecases. Nonetheless, the 3 km ensemble prediction system still faces the problem of insufficient ensemble spread. The analysis of a heavy rainfall event shows that increasing the horizontal resolution facilitates more detailed simulation of multi-scale terrain and more accurate depiction of water vapor and dynamic structure in the rainstorm area, which in turn elevates the forecast performance for this event.
2025, 51(2):167-181.
DOI: 10.7519/j.issn.1000-0526.2024.093001
Abstract:
The standard precipitation verificaiton method and the MODE （Method for Object-Based Diagnostic Evaluation） spatial method are applied to evaluate the performance of the CMA-MESO and CMA-SH9 models in predicting precipitation in eastern China in 2021 in this article. The results show that the two models have relatively high prediction skills for the second and third seasons of 2021, while the prediction skills for the first and fourth seasons are relatively low. The regional numerical models have good application potential in warm season precipitation forecasting. Based on the ETS and BIAS of the four seasons, the overall precipitation prediction skills of the CMA-MESO model in the third season are higher than those of the CMA-SH9 model, while in other seaons, the CMA-SH9 model has relatively higher prediction skills. Both models show a higher BIAS and a higher false alarm ratio in each season. Improving the shortcomings of these two aspects is an important means to enhance the precipitaiton prediction skills of regional models. The spatial verification results of torrential rain for four seasons show that CMA-MESO and CMA-SH9 models have relatively better forecasting abilities for the second and third seasons, and both of them tend to overestimate the object area of torrential rain. The CMA-SH9 model tends to overestimate the object quantile intensities of torrential rainfall in four seasons compared to observations, whereas the CMA-MESO model shows closer agreement with observations, exhibiting an overestimation only in the first season. Spatial verification of the MODE for the July 2021 severe torrential rain in Henan and Typhoon In-Fa reveals that both the CMA-MESO and CMA-SH9 models exhibit a tendency to overestimate the affected area for intense precipitation exceeding heavy torrential rain levels. Nonetheless, these models continue to underpredict the maxima of rainfall, with the CMA-SH9 model outputs more closely aligned with the observed extreme values.
The standard precipitation verificaiton method and the MODE （Method for Object-Based Diagnostic Evaluation） spatial method are applied to evaluate the performance of the CMA-MESO and CMA-SH9 models in predicting precipitation in eastern China in 2021 in this article. The results show that the two models have relatively high prediction skills for the second and third seasons of 2021, while the prediction skills for the first and fourth seasons are relatively low. The regional numerical models have good application potential in warm season precipitation forecasting. Based on the ETS and BIAS of the four seasons, the overall precipitation prediction skills of the CMA-MESO model in the third season are higher than those of the CMA-SH9 model, while in other seaons, the CMA-SH9 model has relatively higher prediction skills. Both models show a higher BIAS and a higher false alarm ratio in each season. Improving the shortcomings of these two aspects is an important means to enhance the precipitaiton prediction skills of regional models. The spatial verification results of torrential rain for four seasons show that CMA-MESO and CMA-SH9 models have relatively better forecasting abilities for the second and third seasons, and both of them tend to overestimate the object area of torrential rain. The CMA-SH9 model tends to overestimate the object quantile intensities of torrential rainfall in four seasons compared to observations, whereas the CMA-MESO model shows closer agreement with observations, exhibiting an overestimation only in the first season. Spatial verification of the MODE for the July 2021 severe torrential rain in Henan and Typhoon In-Fa reveals that both the CMA-MESO and CMA-SH9 models exhibit a tendency to overestimate the affected area for intense precipitation exceeding heavy torrential rain levels. Nonetheless, these models continue to underpredict the maxima of rainfall, with the CMA-SH9 model outputs more closely aligned with the observed extreme values.
2025, 51(2):182-190.
DOI: 10.7519/j.issn.1000-0526.2024.111802
Abstract:
This study employs the high-resolution operational model CMA-MESO to simulate a convective cloud precipitation process in Shandong Province by using a double-moment microphysical scheme with/without hail. The mechanism of hail microphysical effect on convective cloud precipitation and the predictive ability of this model in forecasting hail cloud precipitation are comparatively analyzed. The results show that the CMA-MESO model can simulate this convective precipitation process well. Compared with observations, the squall line life cycle in the model results is similar to the observation, and the distribution and magnitude of precipitation are close to the observation, too. The average liquid water and ice water path of the control group (without hail) in the simulated area is larger than that of the experimental group (including hail). The rising speed of the convective core area in the experimental group slightly increases during convective development but decreases at other times. When hail occurs, the melting and heat absorption in the experimental group is stronger than in the control group. This might be due to the stronger falling speed of hail compared to that of other water condensates, which suppresses the development of convection during the falling process of hail. In addition, increasing the hail amount can affect convective precipitation. The proportion of moderate rain ［1-10 mm·(24 h)-1］ area to the total precipita-tion area in the experimental group decreases, while the proportion of heavy rain and above ［>10 mm·(24 h)-1］ area to the total precipitation area slightly increases. In terms of precipitation amount, with the increased hail, there is no significant change in the intensity of medium-to-light precipitation, but the intensity of heavy rain and above increases.
This study employs the high-resolution operational model CMA-MESO to simulate a convective cloud precipitation process in Shandong Province by using a double-moment microphysical scheme with/without hail. The mechanism of hail microphysical effect on convective cloud precipitation and the predictive ability of this model in forecasting hail cloud precipitation are comparatively analyzed. The results show that the CMA-MESO model can simulate this convective precipitation process well. Compared with observations, the squall line life cycle in the model results is similar to the observation, and the distribution and magnitude of precipitation are close to the observation, too. The average liquid water and ice water path of the control group (without hail) in the simulated area is larger than that of the experimental group (including hail). The rising speed of the convective core area in the experimental group slightly increases during convective development but decreases at other times. When hail occurs, the melting and heat absorption in the experimental group is stronger than in the control group. This might be due to the stronger falling speed of hail compared to that of other water condensates, which suppresses the development of convection during the falling process of hail. In addition, increasing the hail amount can affect convective precipitation. The proportion of moderate rain ［1-10 mm·(24 h)-1］ area to the total precipita-tion area in the experimental group decreases, while the proportion of heavy rain and above ［>10 mm·(24 h)-1］ area to the total precipitation area slightly increases. In terms of precipitation amount, with the increased hail, there is no significant change in the intensity of medium-to-light precipitation, but the intensity of heavy rain and above increases.
2025, 51(2):191-206.
DOI: 10.7519/j.issn.1000-0526.2024.110501
Abstract:
Focusing on the thunderstorm gale process in Liaoning on 6 July 2023, based on the X-band phased array radar data, this paper analyzes the impact mechanisms of meso-γ scale vortex (MV) on merged bow echo and thunderstorm gales which occurred under the background of Northeast China cold vortex. The results show that the thunderstorm gale area in Liaoning Province was located in the southeast quadrant of the Northeast China cold vortex, influenced by low-level shear lines and low-level jet streams. The beneficial environment condition such as extreme temperature difference between 850 hPa and 500 hPa was conducive to the occurrence of thunderstorm gales. The relative humidity near the ground at night was close to 70%, which was not conducive to the formation of strong cold pools. Therefore, there was no bow-shaped pattern in squall lines and the thunderstorm gales were very scattered at this time. Subsequently, the squall line merged with the isolation storm, with shallow MV generated at the merging height, and the rear-inflow jet (RIJ) was weakened. The micro downburst near MV created a strong cold pool near the ground. Under the joint stretching effect of the rising airflow at the edge of the cold pool and the original rising airflow of the storm, the MV stretched upward and strengthened. The ZDR column formed over the MV, indicating the presence of strong updrafts in this area. Although the storm at the MV showed a bow-shaped pattern during this period, there were no thunderstorm gales below the MV. When the rotation of MV weakened, there was a rapid decrease in the scale and concentration of precipitation particles within the storm. The evaporation of precipitation led to the formation of even stronger and larger cold pools on the ground, and the fast development of RIJ below the MV, leading to the concentration of thunderstorm gales in the strong cold pool and RIJ below the MV. The ground strong winds were not caused by the strengthening of MV development, but rather the result of RIJ’s downward development and hydrometeor evaporation.
Focusing on the thunderstorm gale process in Liaoning on 6 July 2023, based on the X-band phased array radar data, this paper analyzes the impact mechanisms of meso-γ scale vortex (MV) on merged bow echo and thunderstorm gales which occurred under the background of Northeast China cold vortex. The results show that the thunderstorm gale area in Liaoning Province was located in the southeast quadrant of the Northeast China cold vortex, influenced by low-level shear lines and low-level jet streams. The beneficial environment condition such as extreme temperature difference between 850 hPa and 500 hPa was conducive to the occurrence of thunderstorm gales. The relative humidity near the ground at night was close to 70%, which was not conducive to the formation of strong cold pools. Therefore, there was no bow-shaped pattern in squall lines and the thunderstorm gales were very scattered at this time. Subsequently, the squall line merged with the isolation storm, with shallow MV generated at the merging height, and the rear-inflow jet (RIJ) was weakened. The micro downburst near MV created a strong cold pool near the ground. Under the joint stretching effect of the rising airflow at the edge of the cold pool and the original rising airflow of the storm, the MV stretched upward and strengthened. The ZDR column formed over the MV, indicating the presence of strong updrafts in this area. Although the storm at the MV showed a bow-shaped pattern during this period, there were no thunderstorm gales below the MV. When the rotation of MV weakened, there was a rapid decrease in the scale and concentration of precipitation particles within the storm. The evaporation of precipitation led to the formation of even stronger and larger cold pools on the ground, and the fast development of RIJ below the MV, leading to the concentration of thunderstorm gales in the strong cold pool and RIJ below the MV. The ground strong winds were not caused by the strengthening of MV development, but rather the result of RIJ’s downward development and hydrometeor evaporation.
WANG Xiaoci
,
TIAN Gang
,
MENG Yingjie
,
WANG Haiyan
,
WANG Jizhu
,
ZHOU Yunyi
,
XU Weili
,
QI Haixia
2025, 51(2):207-220.
DOI: 10.7519/j.issn.1000-0526.2024.122301
Abstract:
Based on the NCAR/NCEP reanalysis data and conventional meteorological and hydrological observation data, 15 cases of numbered floods in the upper reaches of the Hanjiang River in the autumn flood season are taken as the research object to study the characteristics of flood peak patterns and the evolution laws of corresponding weather systems, and a weather conceptual model of flood-causing rainstorm is constructed. The results shown that during the autumn flood season, single peak flood processes occur most frequently in the upper reaches of the Hanjiang River, and the flood hydrograph has diversity. The bimodal pattern has a large flood volume, high peak, and rapid rise and fall of water level, with a mostly pointed and thin shape. The multi-peak flood has the largest volume and longest duration, with varying peak heights. The duration of the unimodal flood process is short, and the daily accumulated precipitation fluctuates greatly, with rapid peak formation, and all of them are sharp and thin. The duration of the bimodal process is generally no less than 11 d, the interval between rainstorm processes is short, the difference between the main peak and the secondary peak is small, and the peak value is more than 20 000 m3·s-1. The duration of the multi-peak precipitation process is the longest, and in the continuous cloudy and rainy weather can last for more than 20 d, but the main peak value is lower than that of the bimodal pattern. From the perspective of large-scale circulation patterns, in mid to high latitudes, there are generally three more obvious pattern adjustments in the bimodal pattern, with a larger meridional degree of circulation. There are fewer adjustments to the multi-peak circulation pattern, and the southern side of Lake Baikal is mostly characterized by small trough and ridge activities. There is no significant adjustment in the unimodal pattern. In the middle and low latitudes, the western Pacific subtropical high with multiple peaks moves most strongly westward, without typhoon or tropical cyclone activities. The bimodal subtropical high oscillates frequently from east to west, often involving tropical cyclones. The unimodal pattern is often accompanied by the merging of continental and oceanic high-pressure systems, with few activities of typhoons or tropical cyclones. The weather conceptual models of flood-causing rainstorm in the upper reaches of the Hanjiang River during the autumn flood season can be divided into five categories: high trough jet forcing (A-Ⅰ), high trough low vortex shear (A-Ⅲ), subtropical high periphery jet forcing (B-Ⅰ), subtropical high periphery southerly flow weak forcing (B-Ⅱ) and subtropical high interior low vortex shear (C-Ⅲ). Bimodal floods are mostly dominated by pattern A, while multimodal floods are mostly dominated by pattern B, with both single peak pattern A and pattern B appearing, and pattern C is only unique to single peak pattern. In addition, ground pattern Ⅰ and pattern Ⅱ are often combined with A-Ⅰ, A-Ⅲ, B-Ⅰ, etc. When the three-layer weather system is well configured, the probability of flooding will be significantly increased.
Based on the NCAR/NCEP reanalysis data and conventional meteorological and hydrological observation data, 15 cases of numbered floods in the upper reaches of the Hanjiang River in the autumn flood season are taken as the research object to study the characteristics of flood peak patterns and the evolution laws of corresponding weather systems, and a weather conceptual model of flood-causing rainstorm is constructed. The results shown that during the autumn flood season, single peak flood processes occur most frequently in the upper reaches of the Hanjiang River, and the flood hydrograph has diversity. The bimodal pattern has a large flood volume, high peak, and rapid rise and fall of water level, with a mostly pointed and thin shape. The multi-peak flood has the largest volume and longest duration, with varying peak heights. The duration of the unimodal flood process is short, and the daily accumulated precipitation fluctuates greatly, with rapid peak formation, and all of them are sharp and thin. The duration of the bimodal process is generally no less than 11 d, the interval between rainstorm processes is short, the difference between the main peak and the secondary peak is small, and the peak value is more than 20 000 m3·s-1. The duration of the multi-peak precipitation process is the longest, and in the continuous cloudy and rainy weather can last for more than 20 d, but the main peak value is lower than that of the bimodal pattern. From the perspective of large-scale circulation patterns, in mid to high latitudes, there are generally three more obvious pattern adjustments in the bimodal pattern, with a larger meridional degree of circulation. There are fewer adjustments to the multi-peak circulation pattern, and the southern side of Lake Baikal is mostly characterized by small trough and ridge activities. There is no significant adjustment in the unimodal pattern. In the middle and low latitudes, the western Pacific subtropical high with multiple peaks moves most strongly westward, without typhoon or tropical cyclone activities. The bimodal subtropical high oscillates frequently from east to west, often involving tropical cyclones. The unimodal pattern is often accompanied by the merging of continental and oceanic high-pressure systems, with few activities of typhoons or tropical cyclones. The weather conceptual models of flood-causing rainstorm in the upper reaches of the Hanjiang River during the autumn flood season can be divided into five categories: high trough jet forcing (A-Ⅰ), high trough low vortex shear (A-Ⅲ), subtropical high periphery jet forcing (B-Ⅰ), subtropical high periphery southerly flow weak forcing (B-Ⅱ) and subtropical high interior low vortex shear (C-Ⅲ). Bimodal floods are mostly dominated by pattern A, while multimodal floods are mostly dominated by pattern B, with both single peak pattern A and pattern B appearing, and pattern C is only unique to single peak pattern. In addition, ground pattern Ⅰ and pattern Ⅱ are often combined with A-Ⅰ, A-Ⅲ, B-Ⅰ, etc. When the three-layer weather system is well configured, the probability of flooding will be significantly increased.
2025, 51(2):221-228.
DOI: 10.7519/j.issn.1000-0526.2024.102601
Abstract:
The atmospheric attenuation characteristics of the FY-3 precipitation measurement radar external calibration test field were analyzed based on sounding data from the National High Altitude Meteorological Observatory in Xilinhot throughout 2023. A quick method for estimating atmospheric attenuation has been established by exploring the relationship between total precipitation water and attenuation. The results indicate that the annual variation of oxygen attenuation is very small, while water vapor attenuation has obvious seasonal characteristics. In addition, the attenuation of water vapor is closely related to the total amount of water vapor. The attenuation of water vapor in Ku-band is numerically equivalent to approximately 1/250 of the total amount of water vapor, and the attenuation of water vapor in Ka-band is approximately 4 times that of the Ku-band. Moreover, there is good consistency between the attenuation estimated by the quick method and the attenuation calculated by the normal method, which indicates that the quick method is reasonable and feasible. The calculation and analysis of atmospheric attenuation could lay a foundation for the smooth implementation of precipitation radar external calibration experiments.
The atmospheric attenuation characteristics of the FY-3 precipitation measurement radar external calibration test field were analyzed based on sounding data from the National High Altitude Meteorological Observatory in Xilinhot throughout 2023. A quick method for estimating atmospheric attenuation has been established by exploring the relationship between total precipitation water and attenuation. The results indicate that the annual variation of oxygen attenuation is very small, while water vapor attenuation has obvious seasonal characteristics. In addition, the attenuation of water vapor is closely related to the total amount of water vapor. The attenuation of water vapor in Ku-band is numerically equivalent to approximately 1/250 of the total amount of water vapor, and the attenuation of water vapor in Ka-band is approximately 4 times that of the Ku-band. Moreover, there is good consistency between the attenuation estimated by the quick method and the attenuation calculated by the normal method, which indicates that the quick method is reasonable and feasible. The calculation and analysis of atmospheric attenuation could lay a foundation for the smooth implementation of precipitation radar external calibration experiments.
2025, 51(2):229-238.
DOI: 10.7519/j.issn.1000-0526.2024.102901
Abstract:
Waterlogging damage is the main limiting factor for stable and high yield of summer maize in Anhui Province. Soil moisture is a direct indicator of agricultural drought and flood conditions. The current density and accuracy of soil moisture observation stations can not satisfy the requirements of drought and flood monitoring, early warning and assessment. To construct a waterlogging index that can reflect the daily changes of soil moisture for summer maize during the seedling stage, based on daily meteorological data, geographic information, and summer maize disaster data of 20 counties (districts) in the northern part of Anhui Province from 1981 to 2020, this paper uses the daily standardized antecedent precipitation evapotranspiration index (SAPEI) in characterizing soil relative humidity. In addition, combined with the industry standard grades of waterlogging for summer maize, the dominant indicators and auxiliary indexes of waterlogging for summer maize during the seedling stage are established. The verified accuracy of the indexes exceeds 90%. The temporal manifestation of waterlogging during the seedling stage of summer maize in northern Anhui is as follows. The most severe period is from 1991 to 2000 and the period from 2001 to 2010 comes the second. 2003 is the year most serious waterlogging in the past 40 years. In spatial distribution, the frequency of waterlogging in the area along the Huaihe River is higher than that in the area north to the Huaihe River. Strengthening the research on monitoring and early warning technology for maize waterlogging and conducting quantitative assessments of regional waterlogging for maize is of great significance to ensure food security in Anhui Province.
Waterlogging damage is the main limiting factor for stable and high yield of summer maize in Anhui Province. Soil moisture is a direct indicator of agricultural drought and flood conditions. The current density and accuracy of soil moisture observation stations can not satisfy the requirements of drought and flood monitoring, early warning and assessment. To construct a waterlogging index that can reflect the daily changes of soil moisture for summer maize during the seedling stage, based on daily meteorological data, geographic information, and summer maize disaster data of 20 counties (districts) in the northern part of Anhui Province from 1981 to 2020, this paper uses the daily standardized antecedent precipitation evapotranspiration index (SAPEI) in characterizing soil relative humidity. In addition, combined with the industry standard grades of waterlogging for summer maize, the dominant indicators and auxiliary indexes of waterlogging for summer maize during the seedling stage are established. The verified accuracy of the indexes exceeds 90%. The temporal manifestation of waterlogging during the seedling stage of summer maize in northern Anhui is as follows. The most severe period is from 1991 to 2000 and the period from 2001 to 2010 comes the second. 2003 is the year most serious waterlogging in the past 40 years. In spatial distribution, the frequency of waterlogging in the area along the Huaihe River is higher than that in the area north to the Huaihe River. Strengthening the research on monitoring and early warning technology for maize waterlogging and conducting quantitative assessments of regional waterlogging for maize is of great significance to ensure food security in Anhui Province.
2025, 51(2):239-248.
DOI: 10.7519/j.issn.1000-0526.2024.112601
Abstract:
To effectively utilize the characteristics of atmospheric electric field signals and improve the precision of lightning risk warning, using data from an atmospheric electric field instrument installed on a 500 m-height platform at the Guangzhou Tower within a 20 km (radius) range, this paper analyzes the full day (00:00 BT-24:00 BT) data from 83 days with thunderstorm processes and 123 days with non-thunderstorm processes corresponding to the instrument in 2021 and 2022, and then proposes a lightning risk warning method combining time-frequency domain features and one-dimensional Morpho based on the fusion of enhanced empirical wavelet transform and adaptive Savitzky-Golay (EEWT-ASG). This proposed method uses the spectral width first-order backward difference and mean square error of time-frequency domain features as warning and judgment features for lightning and non-lightning processes, and energy difference is used as a feature for judging the release of warnings. Through selecting samples for effectiveness testing in this article, the proposed lightning risk warning method achieves an accuracy (POD) of 77.11% during thunderstorms, and also has the lowest false alarm ratio (40.00%) and highest critical success index (0.51) performance. Besides, an average warning lead time of 22.27 min is achieved. During non-thunderstorm processes, POD reaches 90.24%. Most warnings have a delay time of 0-40 min, with an average delay time of 32 min. According to the comparison with previous algorithm models, the method proposed in this paper for warning and relief can meet the needs of lightning risk warning in industries with high lightning impact.
To effectively utilize the characteristics of atmospheric electric field signals and improve the precision of lightning risk warning, using data from an atmospheric electric field instrument installed on a 500 m-height platform at the Guangzhou Tower within a 20 km (radius) range, this paper analyzes the full day (00:00 BT-24:00 BT) data from 83 days with thunderstorm processes and 123 days with non-thunderstorm processes corresponding to the instrument in 2021 and 2022, and then proposes a lightning risk warning method combining time-frequency domain features and one-dimensional Morpho based on the fusion of enhanced empirical wavelet transform and adaptive Savitzky-Golay (EEWT-ASG). This proposed method uses the spectral width first-order backward difference and mean square error of time-frequency domain features as warning and judgment features for lightning and non-lightning processes, and energy difference is used as a feature for judging the release of warnings. Through selecting samples for effectiveness testing in this article, the proposed lightning risk warning method achieves an accuracy (POD) of 77.11% during thunderstorms, and also has the lowest false alarm ratio (40.00%) and highest critical success index (0.51) performance. Besides, an average warning lead time of 22.27 min is achieved. During non-thunderstorm processes, POD reaches 90.24%. Most warnings have a delay time of 0-40 min, with an average delay time of 32 min. According to the comparison with previous algorithm models, the method proposed in this paper for warning and relief can meet the needs of lightning risk warning in industries with high lightning impact.
2025, 51(2):249-256.
DOI: 10.7519/j.issn.1000-0526.2025.011801
Abstract:
The main features of the atmospheric circulation in November 2024 are as follows. The polar vortex in the Northern Hemisphere exhibited a dipole pattern, with the primary center located in the region from north Asia to the area east of Novaya Zemlya, stronger than the long-term average for the same period. The Eurasian mid-to-high latitudes gradually transitioned from a “two ridges and one trough” pattern to a “two troughs and one ridge” pattern. China’s mid-to-high latitudes were controlled by a weak meridional circulation and a high-pressure ridge with fewer upper-level trough activities, resulting in less frequent and weaker cold air processes affecting China, so the national average temperature was significantly higher than normal. The subtropical high was stronger. In November, the national average temperature was 5.2℃, 1.9℃ higher than the long-term average, making it the warmest November since 1961.
The national average precipitation was 21.2 mm,
5% more than that in the same period of normal years. The first cold wave and snowfall weather process occurred in the last dekad of November. Additionally, there were 4 typhoons generated in the Northwest Pacific and the South China Sea in November, 1.8 typhoons more than before. As the result of the static weather condition, there were three fog haze events in November.
The main features of the atmospheric circulation in November 2024 are as follows. The polar vortex in the Northern Hemisphere exhibited a dipole pattern, with the primary center located in the region from north Asia to the area east of Novaya Zemlya, stronger than the long-term average for the same period. The Eurasian mid-to-high latitudes gradually transitioned from a “two ridges and one trough” pattern to a “two troughs and one ridge” pattern. China’s mid-to-high latitudes were controlled by a weak meridional circulation and a high-pressure ridge with fewer upper-level trough activities, resulting in less frequent and weaker cold air processes affecting China, so the national average temperature was significantly higher than normal. The subtropical high was stronger. In November, the national average temperature was 5.2℃, 1.9℃ higher than the long-term average, making it the warmest November since 1961.
The national average precipitation was 21.2 mm,
5% more than that in the same period of normal years. The first cold wave and snowfall weather process occurred in the last dekad of November. Additionally, there were 4 typhoons generated in the Northwest Pacific and the South China Sea in November, 1.8 typhoons more than before. As the result of the static weather condition, there were three fog haze events in November.
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ISSN:1000-0526 CN:11-2282/P