This study utilizes data from a 3D lightning location system,polarimetric radar,and current measurements from channels of triggered lightning flashes(TLFs)to analyze the structural characteristics of the parent thunde...This study utilizes data from a 3D lightning location system,polarimetric radar,and current measurements from channels of triggered lightning flashes(TLFs)to analyze the structural characteristics of the parent thunderstorms associated with negative TLFs in South China.The triggered-flash region(TFR)displays distinct stratiform cloud characteristics,including lower radar reflectivity heights and a predominance of ice crystals and dry snow above the 0℃ layer.In contrast,the thunderstorm convection core region(CCR)tends to have more graupel particles in the mixed-phase layers and exhibits an ice-water content peak approximately 3.4 times that of the TFR.The charge regions involved in discharges in TFRs exhibit a dipolar charge structure,with the-5℃ layer roughly dividing the upper positive and lower negative charge regions.Conversely,the CCRs feature a typical tripolar charge structure.The dominant dipole charge structure in the TFR results in an increase in the negative charge field below the negative charge region with height,providing a necessary condition for successfully triggering negative TLFs.Furthermore,the horizontal extent of TLFs is positively correlated with their duration and charge transfer.Regions where TLF channels with larger charge transfers propagate tend to have greater maximum radar reflectivity but lower average radar reflectivity compared to regions with TLFs with smaller charge transfer.展开更多
Thunderstorm wind gusts are small in scale,typically occurring within a range of a few kilometers.It is extremely challenging to monitor and forecast thunderstorm wind gusts using only automatic weather stations.There...Thunderstorm wind gusts are small in scale,typically occurring within a range of a few kilometers.It is extremely challenging to monitor and forecast thunderstorm wind gusts using only automatic weather stations.Therefore,it is necessary to establish thunderstorm wind gust identification techniques based on multisource high-resolution observations.This paper introduces a new algorithm,called thunderstorm wind gust identification network(TGNet).It leverages multimodal feature fusion to fuse the temporal and spatial features of thunderstorm wind gust events.The shapelet transform is first used to extract the temporal features of wind speeds from automatic weather stations,which is aimed at distinguishing thunderstorm wind gusts from those caused by synoptic-scale systems or typhoons.Then,the encoder,structured upon the U-shaped network(U-Net)and incorporating recurrent residual convolutional blocks(R2U-Net),is employed to extract the corresponding spatial convective characteristics of satellite,radar,and lightning observations.Finally,by using the multimodal deep fusion module based on multi-head cross-attention,the temporal features of wind speed at each automatic weather station are incorporated into the spatial features to obtain 10-minutely classification of thunderstorm wind gusts.TGNet products have high accuracy,with a critical success index reaching 0.77.Compared with those of U-Net and R2U-Net,the false alarm rate of TGNet products decreases by 31.28%and 24.15%,respectively.The new algorithm provides grid products of thunderstorm wind gusts with a spatial resolution of 0.01°,updated every 10minutes.The results are finer and more accurate,thereby helping to improve the accuracy of operational warnings for thunderstorm wind gusts.展开更多
In August 2019,accompanied by an Arctic warming event,elevated thunderstorms crossed over the North Pole(NP)and produced lightning.The northernmost stroke occurred less than 50 km from the NP,marking the closest strok...In August 2019,accompanied by an Arctic warming event,elevated thunderstorms crossed over the North Pole(NP)and produced lightning.The northernmost stroke occurred less than 50 km from the NP,marking the closest stroke to the NP ever recorded.Using ERA5 reanalysis data and satellite observations,we investigated the background and development mechanism of this event.Warm and moist air from low latitudes was transported northward to the vicinity of the North Pole by the 850-h Pa jet,resulting in convergence.Through the combined effects of frontal lifting and the presence of underlying cold air,the warm and moist air was lifted to heights above the melting layer,triggering elevated thunderstorms above the frontal boundary.These findings describe a strong link between warming events and thunderstorms,revealing the formation mechanisms of elevated thunderstorms in the Arctic.In the context of rapid Arctic warming,this study provides preliminary insights into the meteorological conditions conducive to thunderstorm formation in the region.展开更多
Thunderstorm detection based on the Atmospheric Electric Field(AEF)has evolved from time-domain models to space-domain models.It is especially important to evaluate and determine the particularly Weather Attribute(WA)...Thunderstorm detection based on the Atmospheric Electric Field(AEF)has evolved from time-domain models to space-domain models.It is especially important to evaluate and determine the particularly Weather Attribute(WA),which is directly related to the detection reliability and authenticity.In this paper,a strategy is proposed to integrate three currently competitive WA's evaluation methods.First,a conventional evaluation method based on AEF statistical indicators is selected.Subsequent evaluation approaches include competing AEF-based predicted value intervals,and AEF classification based on fuzzy c-means.Different AEF attributes contribute to a more accurate AEF classification to different degrees.The resulting dynamic weighting applied to these attributes improves the classification accuracy.Each evaluation method is applied to evaluate the WA of a particular AEF,to obtain the corresponding evaluation score.The integration in the proposed strategy takes the form of a score accumulation.Different cumulative score levels correspond to different final WA results.Thunderstorm imaging is performed to visualize thunderstorm activities using those AEFs already evaluated to exhibit thunderstorm attributes.Empirical results confirm that the proposed strategy effectively and reliably images thunderstorms,with a 100%accuracy of WA evaluation.This is the first study to design an integrated thunderstorm detection strategy from a new perspective of WA evaluation,which provides promising solutions for a more reliable and flexible thunderstorm detection.展开更多
Changes in the Atmospheric Electric Field Signal(AEFS)are highly correlated with weather changes,especially with thunderstorm activities.However,little attention has been paid to the ambiguous weather information impl...Changes in the Atmospheric Electric Field Signal(AEFS)are highly correlated with weather changes,especially with thunderstorm activities.However,little attention has been paid to the ambiguous weather information implicit in AEFS changes.In this paper,a Fuzzy C-Means(FCM)clustering method is used for the first time to develop an innovative approach to characterize the weather attributes carried by AEFS.First,a time series dataset is created in the time domain using AEFS attributes.The AEFS-based weather is evaluated according to the time-series Membership Degree(MD)changes obtained by inputting this dataset into the FCM.Second,thunderstorm intensities are reflected by the change in distance from a thunderstorm cloud point charge to an AEF apparatus.Thus,a matching relationship is established between the normalized distance and the thunderstorm dominant MD in the space domain.Finally,the rationality and reliability of the proposed method are verified by combining radar charts and expert experience.The results confirm that this method accurately characterizes the weather attributes and changes in the AEFS,and a negative distance-MD correlation is obtained for the first time.The detection of thunderstorm activity by AEF from the perspective of fuzzy set technology provides a meaningful guidance for interpretable thunderstorms.展开更多
Based on the number of asthmatic children in the Children's Hospital of Yulin City,the monitoring data of daily pollen concentration,and routine meteorological and environmental monitoring data of Yulin City from ...Based on the number of asthmatic children in the Children's Hospital of Yulin City,the monitoring data of daily pollen concentration,and routine meteorological and environmental monitoring data of Yulin City from 2020 to 2022,the meteorological and environmental conditions of a thunderstorm asthma event in Yulin City in northern Shaanxi on September 9,2022 were analyzed.The results show that the strong convective weather was accompanied by a strong thunderstorm,lightning,gusts,short-time heavy precipitation and small hail,and the convective activity lasted for nearly 7 h.The short-term abrupt change of allergenic substances such as artemisia pollen caused by lightning,gusts and precipitation,the sudden drop in temperature,the inversion near the surface and the stimulation of cold air were the key meteorological conditions for the subsequent outbreak of asthma.In early September in 2022,the daily average pollen concentration in Yulin City was up to 1067.9 particles/1000 mm^(2),which was 113.3%and 41.2%higher than that of the same period in 2021 and 2020,respectively.The day before the thunderstorm,the pollen concentration soared to 2680 particles/1000 mm^(2),reaching the maximum of the year.The synergistic effect of the thunderstorm event and the sharp increase in pollen concentration on the previous day provided the background of heavy pollen pollution for this outbreak of thunderstorm asthma.O_(3)concentration was consistently high on the day of thunderstorm and the day before,and the peaks of O_(3)and PM 10 concentration appeared subsequently in the afternoon of the day,which became the background of air pollution for the asthma outbreak.展开更多
Based on the lightning monitoring data, automatic and routine weather station observation data in spring （March-May） of 2013 of Sichuan Province, the corresponding relationship between the spatial distribution and t...Based on the lightning monitoring data, automatic and routine weather station observation data in spring （March-May） of 2013 of Sichuan Province, the corresponding relationship between the spatial distribution and the different regions, and the characteristics of atmospheric circulation and evolution of influence the sys- tem were analyzed and summarized. The results show that： the lightning and thunderstorm showed great regional differences in the spring of 2013 in Sichuan Province and the thunderstorm activity period was not the same in different areas. Because of the change of atmospheric circulation, the influence system from March to May corresponding to the thunderstorms in Sichuan tended to be volatile, also.展开更多
By dint of natural orthogonal function(EOF) decomposition,correlation and trend analysis methods,the temporal and spatial variation characteristics of thunderstorms in recent 46 years in Henan Province were analyzed.T...By dint of natural orthogonal function(EOF) decomposition,correlation and trend analysis methods,the temporal and spatial variation characteristics of thunderstorms in recent 46 years in Henan Province were analyzed.The result showed that the thunderstorms in Henan Province decreased gradually from the northwest region to the southeast region and the frequency of thunderstorms in the southeast area was relatively high.The thunderstorm intensity area was in its horizontal distribution.Thunderstorms acted relative actively in 60s and tended to dwindle in the end of 80s.While in recent years,the thunderstorms tended to increase and started act frequently.Since March to August in every year,thunderstorms multiplied in each region and decreased after September.The period between 16:00 to 20:00 was the high peak hours of thunderstorms every year.Thunderstorms distribution in Henan Province had pretty good consistence,increasing and decreasing at the same time.The annual variation of thunderstorms showed an unobvious decreasing tendency.展开更多
Three summer thunderstorms in the eastern region of China were analyzed in detail using multiple data, including Doppler radar, lightning location network, TRMM （Tropical Rainfall Measuring Mission）, MT- SAT （Multi...Three summer thunderstorms in the eastern region of China were analyzed in detail using multiple data, including Doppler radar, lightning location network, TRMM （Tropical Rainfall Measuring Mission）, MT- SAT （Multi-Function Transport Satellite） images, NCEP （National Centers for Environmental Prediction） Reanalysis, and radiosonde. Two of the three storms were sprite-producing and the other was non-sprite- producing. The two sprite-producing storms occurred on 1 2 August and 2~28 July 2007, producing 16 and one sprite, respectively. The non-sprite-producing storm occurred on 29-30 July 2007. The major ob- jective of the study was to try to find possible differences between sprite-producing and non-sprite producing storms using the multiple datasets. The results showed that the convection in the 1-2 August storm was the strongest compared with the other storms, and it produced the largest number of sprites. Precipitation ice, cloud ice and cloud water content in the convective regions in the 1-2 August storm were larger than in the other two storms, but the opposite was true in the weak convective regions. The storm microphysical prop- erties along lines through parent CG （cloud-to-ground lightning） locations showed no special characteristics related to sprites. The flash rate evolution in the 1-2 August storm provided additional confirmation that major sprite activity coincides with a rapid decrease in the negative CG flash rate. However, the evolution curve of the CG flash rate was erratic in the sprite-producing storm on 27-28 July, which was significantly different from that in the 1 2 August storm. The average positive CG peak current in sprite-producing storms was larger than that in the non-sprite-producing one.展开更多
The Tibetan Plateau, with an average altitude above 4000 m, is the highest and largest plateau in the world. The frequency of thunderstorms in this region is extremely high. Many indices are used in operational foreca...The Tibetan Plateau, with an average altitude above 4000 m, is the highest and largest plateau in the world. The frequency of thunderstorms in this region is extremely high. Many indices are used in operational forecasting to assess the stability of the atmosphere and predict the probability of severe thunderstorm development. One of the disadvantages of many of these indices is that they are mainly based on observations from plains. However, considering the Plateau＇s high elevation, most convective parameters cannot be applied directly, or their application is ineffective. The pre-convective environment on thunderstorm days in this region is investigated based on sounding data obtained throughout a five-year period（2006–10）.Thunderstorms occur over the Tibetan Plateau under conditions that differ strikingly from those in plains. On this basis,stability indices, such as the Showalter index（including SI and SICCL）, and the K index are improved to better assess the thunderstorm environments on the Plateau. Verification parameters, such as the true-skill statistic（TSS） and Heidke skill score（HSS）, are adopted to evaluate the optimal thresholds and relative forecast skill for each modified index. Lastly, the modified indices are verified with a two-year independent dataset（2011–12）, showing satisfactory results for the modified indices. For determining whether or not a thunderstorm day is likely to occur, we recommend the modified SICCLindex.展开更多
Thunderstorms of pre-monsoon season (April – May) over Kolkata (22° 32’N, 88° 20’E), India are invariably accompanied with lightning flashes, high wind gusts, torrential rainfall, occasional hail and torn...Thunderstorms of pre-monsoon season (April – May) over Kolkata (22° 32’N, 88° 20’E), India are invariably accompanied with lightning flashes, high wind gusts, torrential rainfall, occasional hail and tornadoes which significantly affect the life and property on the ground and aviation aloft. The societal and economic impact due to such storms made accurate prediction of the weather phenomenon a serious concern for the meteorologists of India. The initiation of such storms requires sufficient moisture in lower troposphere, high surface temperature, conditional instability and a source of lift to initiate the convection. Convective available potential energy (CAPE) is a measure of the energy realized when conditional instability is released. It plays an important role in meso-scale convective systems. Convective inhibition energy (CINE) on the other hand acts as a possible barrier to the release of convection even in the presence of high value of CAPE. The main idea of the present study is to see whether a consistent quantitative range of CAPE and CINE can be identified for the prevalence of such thunderstorms that may aid in operational forecast. A statistical – fuzzy coupled method is implemented for the purpose. The result reveals that a definite range of CINE within 0 – 150 Jkg-1 is reasonably pertinent whereas no such range of CAPE depicts any consistency for the occurrence of severe thunderstorms over Kolkata. The measure of CINE mainly depends upon the altitude of the level of free convection (LFC), surface temperature (T) and surface mixing ratio (q). The box-and-whisker plot of LFC, T and q are drawn to select the most dependable parameter for the consistency of CINE in the prevalence of such thunderstorms. The skills of the parameters are evaluated through skill score analyses. The percentage error during validation with the observation of 2010 is estimated to be 0% for the range of CINE and 3.9% for CAPE.展开更多
The electrical characteristics of thunderstorms in three different altitude regions of the Chinese inland plateau have been analyzed in this paper. The results show, according to the polarity of the surface electric ...The electrical characteristics of thunderstorms in three different altitude regions of the Chinese inland plateau have been analyzed in this paper. The results show, according to the polarity of the surface electric （E） field, that the thunderstorms can be divided into two categories in the study regions： one showing the normal tripole electrical charge structure （normal-type）, and the other showing the special tripole charge structure with a larger-than-usual lower positive charge center （LPCC） at the base of thunderstorm （special-type）, where the induced surface E field is controlled by the LPCC when a thunderstorm is overhead. We find that the two types of thunderstorms have different occurrences in different regions, and the percentage of special-type thunderstorms increases with the altitude. On the whole, the flash rate of thunderstorms is quite low, and the mean value is about 1-3 fl/min, while the flash rate of special-type is slightly greater than that of the normal-type thunderstorm. The statistical results of cloud-to-ground flash （CG） numbers indicate that the ratio of ＋CG flash increases with the altitude, with the value about 14.7 percent through 25.4 percent.展开更多
Thunderstorm gusts are a common form of severe convective weather in the warm season in North China,and it is of great importance to correctly forecast them.At present,the forecasting of thunderstorm gusts is mainly b...Thunderstorm gusts are a common form of severe convective weather in the warm season in North China,and it is of great importance to correctly forecast them.At present,the forecasting of thunderstorm gusts is mainly based on traditional subjective methods,which fails to achieve high-resolution and high-frequency gridded forecasts based on multiple observation sources.In this paper,we propose a deep learning method called Thunderstorm Gusts TransU-net(TGTransUnet)to forecast thunderstorm gusts in North China based on multi-source gridded product data from the Institute of Urban Meteorology(IUM)with a lead time of 1 to 6 h.To determine the specific range of thunderstorm gusts,we combine three meteorological variables:radar reflectivity factor,lightning location,and 1-h maximum instantaneous wind speed from automatic weather stations(AWSs),and obtain a reasonable ground truth of thunderstorm gusts.Then,we transform the forecasting problem into an image-to-image problem in deep learning under the TG-TransUnet architecture,which is based on convolutional neural networks and a transformer.The analysis and forecast data of the enriched multi-source gridded comprehensive forecasting system for the period 2021–23 are then used as training,validation,and testing datasets.Finally,the performance of TG-TransUnet is compared with other methods.The results show that TG-TransUnet has the best prediction results at 1–6 h.The IUM is currently using this model to support the forecasting of thunderstorm gusts in North China.展开更多
The influences of large areas of semi-unbounded cold water surface on the evolution, propagation and precipitation production of thunderstorms are simulated by using a fully elastic three-dimensional numerical hailsto...The influences of large areas of semi-unbounded cold water surface on the evolution, propagation and precipitation production of thunderstorms are simulated by using a fully elastic three-dimensional numerical hailstorm model. Real sounding profiles for temperature, humidity and wind are employed. The model has successfully simulated the significant modification of the propagation path of thunderstorms near the cold water area. The path change can be either' along-bank' or' toward-bank', depending on the position of the storm system relative to convergence zone of the water-land circulation. The simulations also show that thunderstorms developing or propagating within the convergence zone of local circulation will be intensified and produce much heavier hail, whereas those over cold water surface or the air that has been cooled by the water will be strongly inhibited.The influence of the cold water surface on thunderstorm characters is largely dependent upon the direction and intensity of the low-level wind.展开更多
[Objective] The study aimed to discuss the distribution characteristics of thunderstorms in Xuzhou City. [Method] Based on thunder- storm observation data during 1978 -2008 provided by Jiuli Mountain station, beginnin...[Objective] The study aimed to discuss the distribution characteristics of thunderstorms in Xuzhou City. [Method] Based on thunder- storm observation data during 1978 -2008 provided by Jiuli Mountain station, beginning and ending months, days, duration, frequency, hours and direction of thunderstorms in Xuzhou were analyzed. [ Result] From 1978 to 2008, there were obvious annual variations in thunderstorm days in Xuzhou City. Thunderstorm days were more in July and August compared with other months, while there were no thunderstorms in January and De- comber. Thunderstorms began earliest in February and ended latest in November, with a long span. The longest duration of thunderstorms reached 259 d, accounting for 71% of total days of a year. The maximum frequency of thunderstorms （64） appeared in 1995, and the maximum hours of thunderstorms （4 048 h） appeared in 2003. Thunderstorms occurred most frequently in the southwest, followed by SE and NW. [ Conclusion] The research could provide scientific references for the prevention and control of lightning strokes in Xuzhou in future.展开更多
Based on daily data of thunderstorms during 1967 -2012 from the national meteorological station in Doumen District of Zhuhai City, the climatic characteristics of thunderstorms in Doumen District were analyzed using c...Based on daily data of thunderstorms during 1967 -2012 from the national meteorological station in Doumen District of Zhuhai City, the climatic characteristics of thunderstorms in Doumen District were analyzed using climate tendency rate, sliding t test, trend analysis and experience frequency, The results showed that annual thunderstorm days in Doumen District showed a decreasing trend in recent 46 years; thunderstorms appeared in the whole year; monthly thunderstorm days had two peaks; thunderstorms occurred frequently in summer, especially in August, while thunderstorm days were the least in winter; annual thunderstorm days in Doumen District declined sharply in 1984; most thunderstorms began from middle February to late March and ended from late September to middle November; thunderstorms in Doumen District lasted for a long term, and there was a great change in thunderstorm duration in different years.展开更多
The observation, in the past, that a thunderstorm perturbed the transmissions of an old vacuum tubes radio with noise discharges in correspondence with lightnings, suggested the possibility of radio-acoustic study of ...The observation, in the past, that a thunderstorm perturbed the transmissions of an old vacuum tubes radio with noise discharges in correspondence with lightnings, suggested the possibility of radio-acoustic study of thunderstorms. The noise discharges appeared to convey not only information about lightnings, but also about any other thunderstorm electromagnetic phenomena generating noise discharges. The low-cost instrumentation involved in the radio-acoustic study, comprised a radio Telefunken mod. T33B, a 15 m long indoor wire antenna, a mobile telephone Samsung Galaxy S20 FE 5G provided with the recorder App Enregistreur vocal, a computer HP Pavillion dv5-1254eg and the s/w audio analyser Audacity. A first thunderstorm on 20 June 2023 and a second thunderstorm on 22 June 2023, both above Munich, were radio-acoustic studied. The second thunderstorm was more active than the first and released much more energy.展开更多
Based on the 1951-2007 thunderstorms in Jiangsu,a study is conducted for their climate trends,periodicity,spatiotemporal patterns,and the distributions of the first and last days of the thunderstorms at different guar...Based on the 1951-2007 thunderstorms in Jiangsu,a study is conducted for their climate trends,periodicity,spatiotemporal patterns,and the distributions of the first and last days of the thunderstorms at different guarantee rates (GRs) using climate tendency rate,wavelet analysis,and GR for diagnosis.Results suggest that the inter-annual number of thunderstorm days (TSDs) exhibits a decreasing trend in this province.The trend is displayed mainly in the decreasing TSD number in summer and autumn except in spring,when the variation is not significant in the study period.In this province,the TSD number declines by ～2 days per 10 years.On an inter-annual basis,the pronounced positive departures of the number take place chiefly in the early 1960s,the late 1960s to the early-mid-1970s,the late 1980s,and the late 1990s compared with the negative anomalies dominant in the late 1970s to the mid-1980s,the mid-to-late-1990s,and the late 1990s to 2007.There are vast differences in the initial and ending days at diverse GRs in different areas of the province.At 50% GR,the earliest (last) days occur from mid-March to early April (early to late September) while at 80% GR,the initial (last) days are from late March to early May (early to late October).For the distribution of periods,the periods >8-10 years are relatively stable for the entire province.Based on 1951-2007 period analysis,the region north (south) of the Huaihe River experiences TSDs less (more) than normal days in recent years.展开更多
In this study,we examine the dynamics and microphysical structures of a deep compact thunderstorm event driving cloud-to-ground(CG)lightning over the Nanjing area located within the Yangtze-Huai River Basin(YHRB)durin...In this study,we examine the dynamics and microphysical structures of a deep compact thunderstorm event driving cloud-to-ground(CG)lightning over the Nanjing area located within the Yangtze-Huai River Basin(YHRB)during the monsoon break period.The microphysical structures combined with the dynamics in the glaciated,mixed-phase,and warm-phase layers during the formative,intensifying,and mature stages of the thunderstorm were first investigated using C-band polarimetric radar and CG lightning observations.The results show that the mature phase of the thunderstorm produced a local cold pool,which collided with a southerly warm wind,resulting in a strong updraft.The strong updraft favored the lifting of raindrops to the mixed-phase region to form abundant supercooled liquid water and graupel.From the formative stage to the developing stage and further to the mature stage,increased ZH-and reduced ZDR-values within the mixed-phase region are found,especially within the strong updraft region(>5 m s^(-1)).This phenomenon suggests that supercooled raindrops evolved into large hydrometeors(graupel and hail),indicative of a strong riming process.The signatures within this region are consistent with a favorable environment for thunderstorm electrification and generate the most frequent lightning during the thunderstorm life cycle.展开更多
This paper presents an analysis of spatial and temporal variation of rainfall and thunderstorm occurrence over Ken-ya from January 1987 to December 2017.The meteorological data used were obtained from the Kenya Meteor...This paper presents an analysis of spatial and temporal variation of rainfall and thunderstorm occurrence over Ken-ya from January 1987 to December 2017.The meteorological data used were obtained from the Kenya Meteorological Department(KMD)for the same period.This included the monthly thunderstorm occurrences and rainfall amounts of 26 synoptic stations across the country.The characteristics of monthly,seasonal and annual frequency results were presented on spatial maps while Time series graphs were used to display the pattern for annual cycle,seasonal varia-tions and the inter-annual variability of rainfall amounts and thunderstorm occurrences.A well-known non-parametric statistical method Mann Kendall(MK)trend test was used to determine and compare the statistical significance of the trends.Thunderstorm frequencies over the Eastern,Central and Coast regions of the country showed a bimodal pattern with high frequencies coinciding with March-April-May(MAM)and October-November-December(OND)rainy sea-sons.Very few thunderstorm days were detected over June-July-August(JJA)season.The areas to the western part of the country,near Lake Victoria,had the highest thunderstorm frequencies in the country over the three seasons:MAM,JJAS and OND.The annual frequency showed a quasi-unimodal pattern.These places near Lake Victoria showed sig-nificantly increasing thunderstorm trends during the MAM and OND seasons irrespective of the rainfall trends.This shows the effects of Lake Victoria over these areas,and it acts as a continuous source of moisture for thunderstorm for-mation.However,most stations across the country showed a reducing trend of thunderstorm frequency during MAM and JJA seasons.The importance of these findings is that they could support various policy makers,and users of cli-mate information,especially in the agriculture and aviation industries.展开更多
基金funded by the Natural Science Foundation of China(Grant No.U2342215)Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province(Grant No.SCSF202302)。
文摘This study utilizes data from a 3D lightning location system,polarimetric radar,and current measurements from channels of triggered lightning flashes(TLFs)to analyze the structural characteristics of the parent thunderstorms associated with negative TLFs in South China.The triggered-flash region(TFR)displays distinct stratiform cloud characteristics,including lower radar reflectivity heights and a predominance of ice crystals and dry snow above the 0℃ layer.In contrast,the thunderstorm convection core region(CCR)tends to have more graupel particles in the mixed-phase layers and exhibits an ice-water content peak approximately 3.4 times that of the TFR.The charge regions involved in discharges in TFRs exhibit a dipolar charge structure,with the-5℃ layer roughly dividing the upper positive and lower negative charge regions.Conversely,the CCRs feature a typical tripolar charge structure.The dominant dipole charge structure in the TFR results in an increase in the negative charge field below the negative charge region with height,providing a necessary condition for successfully triggering negative TLFs.Furthermore,the horizontal extent of TLFs is positively correlated with their duration and charge transfer.Regions where TLF channels with larger charge transfers propagate tend to have greater maximum radar reflectivity but lower average radar reflectivity compared to regions with TLFs with smaller charge transfer.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3004104)the National Natural Science Foundation of China(Grant No.U2342204)+4 种基金the Innovation and Development Program of the China Meteorological Administration(Grant No.CXFZ2024J001)the Open Research Project of the Key Open Laboratory of Hydrology and Meteorology of the China Meteorological Administration(Grant No.23SWQXZ010)the Science and Technology Plan Project of Zhejiang Province(Grant No.2022C03150)the Open Research Fund Project of Anyang National Climate Observatory(Grant No.AYNCOF202401)the Open Bidding for Selecting the Best Candidates Program(Grant No.CMAJBGS202318)。
文摘Thunderstorm wind gusts are small in scale,typically occurring within a range of a few kilometers.It is extremely challenging to monitor and forecast thunderstorm wind gusts using only automatic weather stations.Therefore,it is necessary to establish thunderstorm wind gust identification techniques based on multisource high-resolution observations.This paper introduces a new algorithm,called thunderstorm wind gust identification network(TGNet).It leverages multimodal feature fusion to fuse the temporal and spatial features of thunderstorm wind gust events.The shapelet transform is first used to extract the temporal features of wind speeds from automatic weather stations,which is aimed at distinguishing thunderstorm wind gusts from those caused by synoptic-scale systems or typhoons.Then,the encoder,structured upon the U-shaped network(U-Net)and incorporating recurrent residual convolutional blocks(R2U-Net),is employed to extract the corresponding spatial convective characteristics of satellite,radar,and lightning observations.Finally,by using the multimodal deep fusion module based on multi-head cross-attention,the temporal features of wind speed at each automatic weather station are incorporated into the spatial features to obtain 10-minutely classification of thunderstorm wind gusts.TGNet products have high accuracy,with a critical success index reaching 0.77.Compared with those of U-Net and R2U-Net,the false alarm rate of TGNet products decreases by 31.28%and 24.15%,respectively.The new algorithm provides grid products of thunderstorm wind gusts with a spatial resolution of 0.01°,updated every 10minutes.The results are finer and more accurate,thereby helping to improve the accuracy of operational warnings for thunderstorm wind gusts.
基金supported by the National Key Research and Development Program of China(2023YFC3007703)National Natural Science Foundation of China(Grant Nos.41675066,42394122)+1 种基金CAS Project of Stable Support for Youth Team in Basic Research Field(YSRR-018)the Chinese Meridian Project。
文摘In August 2019,accompanied by an Arctic warming event,elevated thunderstorms crossed over the North Pole(NP)and produced lightning.The northernmost stroke occurred less than 50 km from the NP,marking the closest stroke to the NP ever recorded.Using ERA5 reanalysis data and satellite observations,we investigated the background and development mechanism of this event.Warm and moist air from low latitudes was transported northward to the vicinity of the North Pole by the 850-h Pa jet,resulting in convergence.Through the combined effects of frontal lifting and the presence of underlying cold air,the warm and moist air was lifted to heights above the melting layer,triggering elevated thunderstorms above the frontal boundary.These findings describe a strong link between warming events and thunderstorms,revealing the formation mechanisms of elevated thunderstorms in the Arctic.In the context of rapid Arctic warming,this study provides preliminary insights into the meteorological conditions conducive to thunderstorm formation in the region.
基金supported in part by the National Natural Science Foundation of China under Grant 62171228in part by the National Key R&D Program of China under Grant 2021YFE0105500in part by the Program of China Scholarship Council under Grant 202209040027。
文摘Thunderstorm detection based on the Atmospheric Electric Field(AEF)has evolved from time-domain models to space-domain models.It is especially important to evaluate and determine the particularly Weather Attribute(WA),which is directly related to the detection reliability and authenticity.In this paper,a strategy is proposed to integrate three currently competitive WA's evaluation methods.First,a conventional evaluation method based on AEF statistical indicators is selected.Subsequent evaluation approaches include competing AEF-based predicted value intervals,and AEF classification based on fuzzy c-means.Different AEF attributes contribute to a more accurate AEF classification to different degrees.The resulting dynamic weighting applied to these attributes improves the classification accuracy.Each evaluation method is applied to evaluate the WA of a particular AEF,to obtain the corresponding evaluation score.The integration in the proposed strategy takes the form of a score accumulation.Different cumulative score levels correspond to different final WA results.Thunderstorm imaging is performed to visualize thunderstorm activities using those AEFs already evaluated to exhibit thunderstorm attributes.Empirical results confirm that the proposed strategy effectively and reliably images thunderstorms,with a 100%accuracy of WA evaluation.This is the first study to design an integrated thunderstorm detection strategy from a new perspective of WA evaluation,which provides promising solutions for a more reliable and flexible thunderstorm detection.
基金supported in part by the National Natural Science Foundation of China under Grant 62171228in part by the National Key R&D Program of China under Grant 2021YFE0105500in part by the Program of China Scholarship Council under Grant 202209040027。
文摘Changes in the Atmospheric Electric Field Signal(AEFS)are highly correlated with weather changes,especially with thunderstorm activities.However,little attention has been paid to the ambiguous weather information implicit in AEFS changes.In this paper,a Fuzzy C-Means(FCM)clustering method is used for the first time to develop an innovative approach to characterize the weather attributes carried by AEFS.First,a time series dataset is created in the time domain using AEFS attributes.The AEFS-based weather is evaluated according to the time-series Membership Degree(MD)changes obtained by inputting this dataset into the FCM.Second,thunderstorm intensities are reflected by the change in distance from a thunderstorm cloud point charge to an AEF apparatus.Thus,a matching relationship is established between the normalized distance and the thunderstorm dominant MD in the space domain.Finally,the rationality and reliability of the proposed method are verified by combining radar charts and expert experience.The results confirm that this method accurately characterizes the weather attributes and changes in the AEFS,and a negative distance-MD correlation is obtained for the first time.The detection of thunderstorm activity by AEF from the perspective of fuzzy set technology provides a meaningful guidance for interpretable thunderstorms.
基金Supported by the People's Government of Yulin City(2023-SF-09)Yulin Meteorological Bureau(2024Y-02)Open Research Fund Project of Key Laboratory of Ecological Environment and Meteorology in the Qinling Mountains and Loess Plateau(2022Y-21).
文摘Based on the number of asthmatic children in the Children's Hospital of Yulin City,the monitoring data of daily pollen concentration,and routine meteorological and environmental monitoring data of Yulin City from 2020 to 2022,the meteorological and environmental conditions of a thunderstorm asthma event in Yulin City in northern Shaanxi on September 9,2022 were analyzed.The results show that the strong convective weather was accompanied by a strong thunderstorm,lightning,gusts,short-time heavy precipitation and small hail,and the convective activity lasted for nearly 7 h.The short-term abrupt change of allergenic substances such as artemisia pollen caused by lightning,gusts and precipitation,the sudden drop in temperature,the inversion near the surface and the stimulation of cold air were the key meteorological conditions for the subsequent outbreak of asthma.In early September in 2022,the daily average pollen concentration in Yulin City was up to 1067.9 particles/1000 mm^(2),which was 113.3%and 41.2%higher than that of the same period in 2021 and 2020,respectively.The day before the thunderstorm,the pollen concentration soared to 2680 particles/1000 mm^(2),reaching the maximum of the year.The synergistic effect of the thunderstorm event and the sharp increase in pollen concentration on the previous day provided the background of heavy pollen pollution for this outbreak of thunderstorm asthma.O_(3)concentration was consistently high on the day of thunderstorm and the day before,and the peaks of O_(3)and PM 10 concentration appeared subsequently in the afternoon of the day,which became the background of air pollution for the asthma outbreak.
文摘Based on the lightning monitoring data, automatic and routine weather station observation data in spring （March-May） of 2013 of Sichuan Province, the corresponding relationship between the spatial distribution and the different regions, and the characteristics of atmospheric circulation and evolution of influence the sys- tem were analyzed and summarized. The results show that： the lightning and thunderstorm showed great regional differences in the spring of 2013 in Sichuan Province and the thunderstorm activity period was not the same in different areas. Because of the change of atmospheric circulation, the influence system from March to May corresponding to the thunderstorms in Sichuan tended to be volatile, also.
基金Supported by Scientific Research Special Fund for Public Welfare Industry (GYHY 200806014)Nanjing University of Information Science & Technology Program (E30JG0730)
文摘By dint of natural orthogonal function(EOF) decomposition,correlation and trend analysis methods,the temporal and spatial variation characteristics of thunderstorms in recent 46 years in Henan Province were analyzed.The result showed that the thunderstorms in Henan Province decreased gradually from the northwest region to the southeast region and the frequency of thunderstorms in the southeast area was relatively high.The thunderstorm intensity area was in its horizontal distribution.Thunderstorms acted relative actively in 60s and tended to dwindle in the end of 80s.While in recent years,the thunderstorms tended to increase and started act frequently.Since March to August in every year,thunderstorms multiplied in each region and decreased after September.The period between 16:00 to 20:00 was the high peak hours of thunderstorms every year.Thunderstorms distribution in Henan Province had pretty good consistence,increasing and decreasing at the same time.The annual variation of thunderstorms showed an unobvious decreasing tendency.
基金supported jointly by Strategic Priority Research Program on Space Science(Grant No.XDA04072400)Project Supported by the Specialized Research Fund for State Key Laboratories,Youth Innovation Promotion Association,CAS,National Basic Research Program of China(973 Program,Grant No.2010CB428602)+2 种基金the Special Fund for Public Welfare Industry(GYHY201006005-07)National Natural Science Foundation of China(Grant Nos.41374153,40930949,40804028)Beijing Natural Science Foundation
文摘Three summer thunderstorms in the eastern region of China were analyzed in detail using multiple data, including Doppler radar, lightning location network, TRMM （Tropical Rainfall Measuring Mission）, MT- SAT （Multi-Function Transport Satellite） images, NCEP （National Centers for Environmental Prediction） Reanalysis, and radiosonde. Two of the three storms were sprite-producing and the other was non-sprite- producing. The two sprite-producing storms occurred on 1 2 August and 2~28 July 2007, producing 16 and one sprite, respectively. The non-sprite-producing storm occurred on 29-30 July 2007. The major ob- jective of the study was to try to find possible differences between sprite-producing and non-sprite producing storms using the multiple datasets. The results showed that the convection in the 1-2 August storm was the strongest compared with the other storms, and it produced the largest number of sprites. Precipitation ice, cloud ice and cloud water content in the convective regions in the 1-2 August storm were larger than in the other two storms, but the opposite was true in the weak convective regions. The storm microphysical prop- erties along lines through parent CG （cloud-to-ground lightning） locations showed no special characteristics related to sprites. The flash rate evolution in the 1-2 August storm provided additional confirmation that major sprite activity coincides with a rapid decrease in the negative CG flash rate. However, the evolution curve of the CG flash rate was erratic in the sprite-producing storm on 27-28 July, which was significantly different from that in the 1 2 August storm. The average positive CG peak current in sprite-producing storms was larger than that in the non-sprite-producing one.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41275128, 41375063 and 41206163)the Chengdu Institute of Plateau Meteorology Foundation
文摘The Tibetan Plateau, with an average altitude above 4000 m, is the highest and largest plateau in the world. The frequency of thunderstorms in this region is extremely high. Many indices are used in operational forecasting to assess the stability of the atmosphere and predict the probability of severe thunderstorm development. One of the disadvantages of many of these indices is that they are mainly based on observations from plains. However, considering the Plateau＇s high elevation, most convective parameters cannot be applied directly, or their application is ineffective. The pre-convective environment on thunderstorm days in this region is investigated based on sounding data obtained throughout a five-year period（2006–10）.Thunderstorms occur over the Tibetan Plateau under conditions that differ strikingly from those in plains. On this basis,stability indices, such as the Showalter index（including SI and SICCL）, and the K index are improved to better assess the thunderstorm environments on the Plateau. Verification parameters, such as the true-skill statistic（TSS） and Heidke skill score（HSS）, are adopted to evaluate the optimal thresholds and relative forecast skill for each modified index. Lastly, the modified indices are verified with a two-year independent dataset（2011–12）, showing satisfactory results for the modified indices. For determining whether or not a thunderstorm day is likely to occur, we recommend the modified SICCLindex.
文摘Thunderstorms of pre-monsoon season (April – May) over Kolkata (22° 32’N, 88° 20’E), India are invariably accompanied with lightning flashes, high wind gusts, torrential rainfall, occasional hail and tornadoes which significantly affect the life and property on the ground and aviation aloft. The societal and economic impact due to such storms made accurate prediction of the weather phenomenon a serious concern for the meteorologists of India. The initiation of such storms requires sufficient moisture in lower troposphere, high surface temperature, conditional instability and a source of lift to initiate the convection. Convective available potential energy (CAPE) is a measure of the energy realized when conditional instability is released. It plays an important role in meso-scale convective systems. Convective inhibition energy (CINE) on the other hand acts as a possible barrier to the release of convection even in the presence of high value of CAPE. The main idea of the present study is to see whether a consistent quantitative range of CAPE and CINE can be identified for the prevalence of such thunderstorms that may aid in operational forecast. A statistical – fuzzy coupled method is implemented for the purpose. The result reveals that a definite range of CINE within 0 – 150 Jkg-1 is reasonably pertinent whereas no such range of CAPE depicts any consistency for the occurrence of severe thunderstorms over Kolkata. The measure of CINE mainly depends upon the altitude of the level of free convection (LFC), surface temperature (T) and surface mixing ratio (q). The box-and-whisker plot of LFC, T and q are drawn to select the most dependable parameter for the consistency of CINE in the prevalence of such thunderstorms. The skills of the parameters are evaluated through skill score analyses. The percentage error during validation with the observation of 2010 is estimated to be 0% for the range of CINE and 3.9% for CAPE.
基金supported by National Natural Science Foundation of China (Grant No. 40905001, 40775004)the Main Direction Program of the Knowledge Innovation of Chinese Academy of Sciences (Grant No.KZCX2-YW-206)
文摘The electrical characteristics of thunderstorms in three different altitude regions of the Chinese inland plateau have been analyzed in this paper. The results show, according to the polarity of the surface electric （E） field, that the thunderstorms can be divided into two categories in the study regions： one showing the normal tripole electrical charge structure （normal-type）, and the other showing the special tripole charge structure with a larger-than-usual lower positive charge center （LPCC） at the base of thunderstorm （special-type）, where the induced surface E field is controlled by the LPCC when a thunderstorm is overhead. We find that the two types of thunderstorms have different occurrences in different regions, and the percentage of special-type thunderstorms increases with the altitude. On the whole, the flash rate of thunderstorms is quite low, and the mean value is about 1-3 fl/min, while the flash rate of special-type is slightly greater than that of the normal-type thunderstorm. The statistical results of cloud-to-ground flash （CG） numbers indicate that the ratio of ＋CG flash increases with the altitude, with the value about 14.7 percent through 25.4 percent.
基金supported in part by the Beijing Natural Science Foundation(Grant No.8222051)the National Key R&D Program of China(Grant No.2022YFC3004103)+2 种基金the National Natural Foundation of China(Grant Nos.42275003 and 42275012)the China Meteorological Administration Key Innovation Team(Grant Nos.CMA2022ZD04 and CMA2022ZD07)the Beijing Science and Technology Program(Grant No.Z221100005222012).
文摘Thunderstorm gusts are a common form of severe convective weather in the warm season in North China,and it is of great importance to correctly forecast them.At present,the forecasting of thunderstorm gusts is mainly based on traditional subjective methods,which fails to achieve high-resolution and high-frequency gridded forecasts based on multiple observation sources.In this paper,we propose a deep learning method called Thunderstorm Gusts TransU-net(TGTransUnet)to forecast thunderstorm gusts in North China based on multi-source gridded product data from the Institute of Urban Meteorology(IUM)with a lead time of 1 to 6 h.To determine the specific range of thunderstorm gusts,we combine three meteorological variables:radar reflectivity factor,lightning location,and 1-h maximum instantaneous wind speed from automatic weather stations(AWSs),and obtain a reasonable ground truth of thunderstorm gusts.Then,we transform the forecasting problem into an image-to-image problem in deep learning under the TG-TransUnet architecture,which is based on convolutional neural networks and a transformer.The analysis and forecast data of the enriched multi-source gridded comprehensive forecasting system for the period 2021–23 are then used as training,validation,and testing datasets.Finally,the performance of TG-TransUnet is compared with other methods.The results show that TG-TransUnet has the best prediction results at 1–6 h.The IUM is currently using this model to support the forecasting of thunderstorm gusts in North China.
基金This work is supported by LASG, IAP, Chinese Academy of Sciences.
文摘The influences of large areas of semi-unbounded cold water surface on the evolution, propagation and precipitation production of thunderstorms are simulated by using a fully elastic three-dimensional numerical hailstorm model. Real sounding profiles for temperature, humidity and wind are employed. The model has successfully simulated the significant modification of the propagation path of thunderstorms near the cold water area. The path change can be either' along-bank' or' toward-bank', depending on the position of the storm system relative to convergence zone of the water-land circulation. The simulations also show that thunderstorms developing or propagating within the convergence zone of local circulation will be intensified and produce much heavier hail, whereas those over cold water surface or the air that has been cooled by the water will be strongly inhibited.The influence of the cold water surface on thunderstorm characters is largely dependent upon the direction and intensity of the low-level wind.
文摘[Objective] The study aimed to discuss the distribution characteristics of thunderstorms in Xuzhou City. [Method] Based on thunder- storm observation data during 1978 -2008 provided by Jiuli Mountain station, beginning and ending months, days, duration, frequency, hours and direction of thunderstorms in Xuzhou were analyzed. [ Result] From 1978 to 2008, there were obvious annual variations in thunderstorm days in Xuzhou City. Thunderstorm days were more in July and August compared with other months, while there were no thunderstorms in January and De- comber. Thunderstorms began earliest in February and ended latest in November, with a long span. The longest duration of thunderstorms reached 259 d, accounting for 71% of total days of a year. The maximum frequency of thunderstorms （64） appeared in 1995, and the maximum hours of thunderstorms （4 048 h） appeared in 2003. Thunderstorms occurred most frequently in the southwest, followed by SE and NW. [ Conclusion] The research could provide scientific references for the prevention and control of lightning strokes in Xuzhou in future.
文摘Based on daily data of thunderstorms during 1967 -2012 from the national meteorological station in Doumen District of Zhuhai City, the climatic characteristics of thunderstorms in Doumen District were analyzed using climate tendency rate, sliding t test, trend analysis and experience frequency, The results showed that annual thunderstorm days in Doumen District showed a decreasing trend in recent 46 years; thunderstorms appeared in the whole year; monthly thunderstorm days had two peaks; thunderstorms occurred frequently in summer, especially in August, while thunderstorm days were the least in winter; annual thunderstorm days in Doumen District declined sharply in 1984; most thunderstorms began from middle February to late March and ended from late September to middle November; thunderstorms in Doumen District lasted for a long term, and there was a great change in thunderstorm duration in different years.
文摘The observation, in the past, that a thunderstorm perturbed the transmissions of an old vacuum tubes radio with noise discharges in correspondence with lightnings, suggested the possibility of radio-acoustic study of thunderstorms. The noise discharges appeared to convey not only information about lightnings, but also about any other thunderstorm electromagnetic phenomena generating noise discharges. The low-cost instrumentation involved in the radio-acoustic study, comprised a radio Telefunken mod. T33B, a 15 m long indoor wire antenna, a mobile telephone Samsung Galaxy S20 FE 5G provided with the recorder App Enregistreur vocal, a computer HP Pavillion dv5-1254eg and the s/w audio analyser Audacity. A first thunderstorm on 20 June 2023 and a second thunderstorm on 22 June 2023, both above Munich, were radio-acoustic studied. The second thunderstorm was more active than the first and released much more energy.
基金Social Development Program of Jiangsu Science and Technology (BS2007088)
文摘Based on the 1951-2007 thunderstorms in Jiangsu,a study is conducted for their climate trends,periodicity,spatiotemporal patterns,and the distributions of the first and last days of the thunderstorms at different guarantee rates (GRs) using climate tendency rate,wavelet analysis,and GR for diagnosis.Results suggest that the inter-annual number of thunderstorm days (TSDs) exhibits a decreasing trend in this province.The trend is displayed mainly in the decreasing TSD number in summer and autumn except in spring,when the variation is not significant in the study period.In this province,the TSD number declines by ～2 days per 10 years.On an inter-annual basis,the pronounced positive departures of the number take place chiefly in the early 1960s,the late 1960s to the early-mid-1970s,the late 1980s,and the late 1990s compared with the negative anomalies dominant in the late 1970s to the mid-1980s,the mid-to-late-1990s,and the late 1990s to 2007.There are vast differences in the initial and ending days at diverse GRs in different areas of the province.At 50% GR,the earliest (last) days occur from mid-March to early April (early to late September) while at 80% GR,the initial (last) days are from late March to early May (early to late October).For the distribution of periods,the periods >8-10 years are relatively stable for the entire province.Based on 1951-2007 period analysis,the region north (south) of the Huaihe River experiences TSDs less (more) than normal days in recent years.
基金primarily supported by the National Natural Science Foundation of China(Grant Nos.42025501,41805025,42175005,and 61827901)the National Key R&D Program of China(2022YFC3003905)+5 种基金the National Key Laboratory on Electromagnetic Environmental Effects and Electro-optical Engineering(NO.JCKYS61422062101)the Meteorological Union Fund of the National Natural Science Foundation of China(U2142203)the Foundation of Jiangsu Provincial Meteorological Bureau(KM202308)The Open Grants of China Meteorological Administration Radar Meteorology Key Laboratory(2023LRMB04)S&T Development Fund of NJIAS(KJF202307)the Open Research Program of the State Key Laboratory of Severe Weather(2022LASW-A01)。
文摘In this study,we examine the dynamics and microphysical structures of a deep compact thunderstorm event driving cloud-to-ground(CG)lightning over the Nanjing area located within the Yangtze-Huai River Basin(YHRB)during the monsoon break period.The microphysical structures combined with the dynamics in the glaciated,mixed-phase,and warm-phase layers during the formative,intensifying,and mature stages of the thunderstorm were first investigated using C-band polarimetric radar and CG lightning observations.The results show that the mature phase of the thunderstorm produced a local cold pool,which collided with a southerly warm wind,resulting in a strong updraft.The strong updraft favored the lifting of raindrops to the mixed-phase region to form abundant supercooled liquid water and graupel.From the formative stage to the developing stage and further to the mature stage,increased ZH-and reduced ZDR-values within the mixed-phase region are found,especially within the strong updraft region(>5 m s^(-1)).This phenomenon suggests that supercooled raindrops evolved into large hydrometeors(graupel and hail),indicative of a strong riming process.The signatures within this region are consistent with a favorable environment for thunderstorm electrification and generate the most frequent lightning during the thunderstorm life cycle.
文摘This paper presents an analysis of spatial and temporal variation of rainfall and thunderstorm occurrence over Ken-ya from January 1987 to December 2017.The meteorological data used were obtained from the Kenya Meteorological Department(KMD)for the same period.This included the monthly thunderstorm occurrences and rainfall amounts of 26 synoptic stations across the country.The characteristics of monthly,seasonal and annual frequency results were presented on spatial maps while Time series graphs were used to display the pattern for annual cycle,seasonal varia-tions and the inter-annual variability of rainfall amounts and thunderstorm occurrences.A well-known non-parametric statistical method Mann Kendall(MK)trend test was used to determine and compare the statistical significance of the trends.Thunderstorm frequencies over the Eastern,Central and Coast regions of the country showed a bimodal pattern with high frequencies coinciding with March-April-May(MAM)and October-November-December(OND)rainy sea-sons.Very few thunderstorm days were detected over June-July-August(JJA)season.The areas to the western part of the country,near Lake Victoria,had the highest thunderstorm frequencies in the country over the three seasons:MAM,JJAS and OND.The annual frequency showed a quasi-unimodal pattern.These places near Lake Victoria showed sig-nificantly increasing thunderstorm trends during the MAM and OND seasons irrespective of the rainfall trends.This shows the effects of Lake Victoria over these areas,and it acts as a continuous source of moisture for thunderstorm for-mation.However,most stations across the country showed a reducing trend of thunderstorm frequency during MAM and JJA seasons.The importance of these findings is that they could support various policy makers,and users of cli-mate information,especially in the agriculture and aviation industries.
