An outbreak of powerful tornadoes tore through multiple states in the central and southern United States from 10 to 11 December 2021.It is claimed the deadliest tornado outbreak that has taken place on December days.T...An outbreak of powerful tornadoes tore through multiple states in the central and southern United States from 10 to 11 December 2021.It is claimed the deadliest tornado outbreak that has taken place on December days.The National Oceanic and Atmospheric Administration had confirmed 66 tornadoes as of 21 December,producing at least 90 fatalities.Most tornadoes occurred at night and thus they were difficult to be visually located,which directly increases the risk for local residents.Two violent nighttime tornadoes were rated category 4 on the enhanced Fujita scale(EF4).Although a high death toll was caused during this event,the operational service actually presented an excellent performance.This tornado outbreak has aroused extensive discussion from both the public and the research community in China.This paper presents a brief discussion on the formation environment and warning services of the tornado outbreak.Recall the deadliest violent tornado in the past 45 years in China,the radar-based tornadic vortex signatures at the locations with EF4 damages show a comparable strength with those in the current cases.Some views on the tornado warning issuance and receiving and damage surveys in China are also presented.展开更多
The predictability of dangerous atmospheric phenomena such as tornado outbreaks has generally been limited to a week or less. However, recent work has demonstrated the importance of the Rossby wavetrain phasing over t...The predictability of dangerous atmospheric phenomena such as tornado outbreaks has generally been limited to a week or less. However, recent work has demonstrated the importance of the Rossby wavetrain phasing over the United States in establishing outbreak-favorable environments. The predictability of Rossby wavetrain phasing is strongly related to numerous climate-scale interannual variability indices, which are predictable many months in advance. To formalize the relationship between interannual variability indices and seasonal tornado outbreak frequency, indices derived from monthly mean Northern Hemisphere 500-hPa and 1000-hPa geopotential height fields and Ni？o 3.4 indices for ENSO phase were compared to annual tornado outbreak seasonal frequencies. Statistical models predicting seasonal outbreak frequency were established using linear（stepwise multivariate linear regressione SMLR） and nonlinear（support vector regressione SVR） statistical modeling techniques.The stepwise methodology revealed predictors that are important in establishing outbreak-favorable environments at long lead times. Additionally, the results of the statistical modeling revealed that the nonlinear SVR technique reduced root mean square errors produced by the control SMLR technique by 28% and provided more consistent forecasts. A preliminary physical analysis revealed that years with high outbreak frequencies were associated with the presence of 500-mb troughs over the central and western US during the peak of outbreak season, while lower frequencies were consistent with ridging over the US or northwest flow over the Plains. These patterns support the results of the statistical modeling, which demonstrate the utility of geopotential height variability as a predictability measure of outbreak frequency.展开更多
The majority of tornado fatalities occur during severe thunderstorm occurrences that produce a large number of tornadoes,termed tornado outbreaks.This study used extreme value theory to estimate the impact of tornado ...The majority of tornado fatalities occur during severe thunderstorm occurrences that produce a large number of tornadoes,termed tornado outbreaks.This study used extreme value theory to estimate the impact of tornado outbreaks on fatalities while accounting for climate and demographic factors.The findings indicate that the number of fatalities increases with the increase of tornado outbreaks.Additionally,this study undertook a counterfactual analysis to determine what would have been the probability of a tornado outbreak under various climatic and demographic scenarios.The results of the counterfactual study indicate that the likelihood of increased mortality increases as the population forecast grows.Intensified El Niño events,on the other hand,reduce the likelihood of further fatalities.La Niña events are expected to increase probability of fatalities.展开更多
Confirming tornado occurrence and estimating tornado intensity are quite challenging,especially for long-track tornadoes and tornado outbreaks,because of the inefficiency or absence of on-site damage surveys,especiall...Confirming tornado occurrence and estimating tornado intensity are quite challenging,especially for long-track tornadoes and tornado outbreaks,because of the inefficiency or absence of on-site damage surveys,especially in sparsely populated regions,which brings about large uncertainties in the tornado record.Some potential methods to alleviate this uncertainty in tornado records have been introduced,such as reports from tornado enthusiasts,trawling of social media sites,and spaceborne photography,which have been shown to be efficient in collecting damage information and depicting the damage swath and ascertaining tornado records.Unmanned aerial vehicles may help in effectively rating tornado intensities.Since 2021,some of these methods have been being tested or are under operation at the China Meteorological Administration Tornado Key Laboratory and the Foshan Tornado Research Center,and have proved to be effective.They have great potential in advancing tornado or downburst damage surveys nationally or worldwide,as well as assessing tornado climatologies,especially in sparsely populated regions such as Northeast China.展开更多
基金Radar Application and Short-term Severe-weather Predictions and Warnings Technology Program(GRMCTD202002)Foshan Innovation Driving and Assistance Project(2021002)+1 种基金Science and Technology Planning Project of Guangdong Province(2019B020208015)Foshan Science and Technology Project in Social Field(2120001008761)。
文摘An outbreak of powerful tornadoes tore through multiple states in the central and southern United States from 10 to 11 December 2021.It is claimed the deadliest tornado outbreak that has taken place on December days.The National Oceanic and Atmospheric Administration had confirmed 66 tornadoes as of 21 December,producing at least 90 fatalities.Most tornadoes occurred at night and thus they were difficult to be visually located,which directly increases the risk for local residents.Two violent nighttime tornadoes were rated category 4 on the enhanced Fujita scale(EF4).Although a high death toll was caused during this event,the operational service actually presented an excellent performance.This tornado outbreak has aroused extensive discussion from both the public and the research community in China.This paper presents a brief discussion on the formation environment and warning services of the tornado outbreak.Recall the deadliest violent tornado in the past 45 years in China,the radar-based tornadic vortex signatures at the locations with EF4 damages show a comparable strength with those in the current cases.Some views on the tornado warning issuance and receiving and damage surveys in China are also presented.
基金supported by the National Science Foundation under Grant No.DGE-0947419 at Mississippi State University
文摘The predictability of dangerous atmospheric phenomena such as tornado outbreaks has generally been limited to a week or less. However, recent work has demonstrated the importance of the Rossby wavetrain phasing over the United States in establishing outbreak-favorable environments. The predictability of Rossby wavetrain phasing is strongly related to numerous climate-scale interannual variability indices, which are predictable many months in advance. To formalize the relationship between interannual variability indices and seasonal tornado outbreak frequency, indices derived from monthly mean Northern Hemisphere 500-hPa and 1000-hPa geopotential height fields and Ni？o 3.4 indices for ENSO phase were compared to annual tornado outbreak seasonal frequencies. Statistical models predicting seasonal outbreak frequency were established using linear（stepwise multivariate linear regressione SMLR） and nonlinear（support vector regressione SVR） statistical modeling techniques.The stepwise methodology revealed predictors that are important in establishing outbreak-favorable environments at long lead times. Additionally, the results of the statistical modeling revealed that the nonlinear SVR technique reduced root mean square errors produced by the control SMLR technique by 28% and provided more consistent forecasts. A preliminary physical analysis revealed that years with high outbreak frequencies were associated with the presence of 500-mb troughs over the central and western US during the peak of outbreak season, while lower frequencies were consistent with ridging over the US or northwest flow over the Plains. These patterns support the results of the statistical modeling, which demonstrate the utility of geopotential height variability as a predictability measure of outbreak frequency.
文摘The majority of tornado fatalities occur during severe thunderstorm occurrences that produce a large number of tornadoes,termed tornado outbreaks.This study used extreme value theory to estimate the impact of tornado outbreaks on fatalities while accounting for climate and demographic factors.The findings indicate that the number of fatalities increases with the increase of tornado outbreaks.Additionally,this study undertook a counterfactual analysis to determine what would have been the probability of a tornado outbreak under various climatic and demographic scenarios.The results of the counterfactual study indicate that the likelihood of increased mortality increases as the population forecast grows.Intensified El Niño events,on the other hand,reduce the likelihood of further fatalities.La Niña events are expected to increase probability of fatalities.
基金supported by the National Natural Science Foundation of China(Grant Nos.42275006 and 42030604)the Science and Technology Research Project in Social Field of Foshan(Grant No.2120001008761)。
文摘Confirming tornado occurrence and estimating tornado intensity are quite challenging,especially for long-track tornadoes and tornado outbreaks,because of the inefficiency or absence of on-site damage surveys,especially in sparsely populated regions,which brings about large uncertainties in the tornado record.Some potential methods to alleviate this uncertainty in tornado records have been introduced,such as reports from tornado enthusiasts,trawling of social media sites,and spaceborne photography,which have been shown to be efficient in collecting damage information and depicting the damage swath and ascertaining tornado records.Unmanned aerial vehicles may help in effectively rating tornado intensities.Since 2021,some of these methods have been being tested or are under operation at the China Meteorological Administration Tornado Key Laboratory and the Foshan Tornado Research Center,and have proved to be effective.They have great potential in advancing tornado or downburst damage surveys nationally or worldwide,as well as assessing tornado climatologies,especially in sparsely populated regions such as Northeast China.
