Valuable dropsonde data were obtained from multiple field campaigns targeting tropical cyclones,namely Higos,Nangka,Saudel,and Atsani,over the western North Pacific by the Hong Kong Observatory and Taiwan Central Weat...Valuable dropsonde data were obtained from multiple field campaigns targeting tropical cyclones,namely Higos,Nangka,Saudel,and Atsani,over the western North Pacific by the Hong Kong Observatory and Taiwan Central Weather Bureau in 2020.The conditional nonlinear optimal perturbation(CNOP)method has been utilized in real-time to identify the sensitive regions for targeting observations adhering to the procedure of real-time field campaigns for the first time.The observing system experiments were conducted to evaluate the effect of dropsonde data and CNOP sensitivity on TC forecasts in terms of track and intensity,using the Weather Research and Forecasting model.It is shown that the impact of assimilating all dropsonde data on both track and intensity forecasts is case-dependent.However,assimilation using only the dropsonde data inside the sensitive regions displays unanimously positive effects on both the track and intensity forecast,either of which obtains comparable benefits to or greatly reduces deterioration of the skill when assimilating all dropsonde data.Therefore,these results encourage us to further carry out targeting observations for the forecast of tropical cyclones according to CNOP sensitivity.展开更多
The characteristics and climatology of funnel clouds in Alaska were examined using operational radiosondes, surface meteorological observations, and reanalysis data. Funnel clouds occurred under weak synoptic forcing ...The characteristics and climatology of funnel clouds in Alaska were examined using operational radiosondes, surface meteorological observations, and reanalysis data. Funnel clouds occurred under weak synoptic forcing between May and September between 11 am and 6 pm Alaska Daylight Time with a maximum occurrence in July. They occurred under Convective Available Potential Energy >500 J·kg-1 and strong low-level wind shear. Characteristic atmospheric profiles during funnel cloud events served to develop a retrieval algorithm based on similarity testing. Out of more than 129,000 soundings between 1971 and 2014, 2724, 442, and 744 profiles were similar to the profiles of observed funnel cloud events in the Interior, Alaska West Coast, and Anchorage regions. While the number of reported funnel clouds has increased since 2000, the frequency of synoptic situations favorable for such events has decreased.展开更多
Three supercell storms on 24 June 2004（0624）,28 June 2003（0628）,and 27 September 2002（0927） induced different damages in Shandong Province.Storm 0927 was inferior in size and intensity to storms 0628 and 0624.Th...Three supercell storms on 24 June 2004（0624）,28 June 2003（0628）,and 27 September 2002（0927） induced different damages in Shandong Province.Storm 0927 was inferior in size and intensity to storms 0628 and 0624.The structure and evolvement of the three storms were analyzed in detail based on the WSR98D radar data in combination with weather charts.The results show that mesoscale surface convergence triggered release of instable energy,which resulted in severe convection.During the development stage,storms 0927,0628,and 0624 displayed multi-cell propagation,single-cell evolution,and multi-cell mergence,respectively.The storm tracks were similar：they were all right-moving supercell storms,i.e.,moving at an angle of 30°-70° to the right of the mean wind and at a speed of about 45%-70% of the mean wind speed.In the mature stage,the maximum reflectivity appeared at the low level in storm 0927,mid level in storm 0628,and mid-upper level in storm 0624.These storms possessed almost all typical features of supercell storms：weak echo region（WER）,bounded weak echo region（BWER）,and mesocyclone.An organized mesocyclone formed at the middle height of an updraft,deepened gradually downward and upward,and became a typical mid-level mesocyclone with strong updrafts.The vertical structures of airflows in the three storms were similar,i.e.,significant convergence at low level,nearly pure rotation at mid level,and divergent rotation at upper level.However,signatures of mid-level horizontal airflows in the three storms were different：at mid level,there was a single vortex in storm 0628,but a double-vortex flow pattern was seen in storms 0927 and 0624.The horizontal structure of the double-vortex flow was hard to be blown away by the environmental airflow,and thus the storms could persist for a longer period of time than the single vortex storm.展开更多
This report synthesizes global tropical cyclone(TC)tornado research and operational practices to date.Tornadoes are one of the secondary(and lesser researched)hazards contributing to the devastation TCs leave in their...This report synthesizes global tropical cyclone(TC)tornado research and operational practices to date.Tornadoes are one of the secondary(and lesser researched)hazards contributing to the devastation TCs leave in their wake.While gale-force winds and storm surge produce the majority of damage and fatalities globally,TC tornadoes also pose a fatal threat,complicating evacuation plans and protective actions as the storm moves inland.Climatological studies characterize TC-spawned tornadoes as usually weak and short-lived,primarily originating from miniature supercells in the outer rainbands.These tornadic features pose challenges to forecasting and radar detection.Additionally,TC tornadoes can pose a threat to communities 12 h prior to and beyond 48 h after a TC makes landfall.Research,both basic and operational,has increased globally over the last few years in efforts to move from a climatological to ingredientsbased approach to detect and forecast TC tornadoes.While the United States has led the charge,given the increased exposure to tornadoes year round,other nations such as China,Japan,and Australia have increased their efforts to record and detect TC tornadoes.Despite these advancements,more work needs to be done globally to understand the TC environment conducive for tornadic activity.Recommendations for future forecasting and research for TC tornadoes include i)develop a comprehensive global tornado database to improve research and forecasting efforts;ii)apply innovative technology to detect tornadoes;and iii)conduct field campaigns to thoroughly sample TC tornado environments,particularly along coastlines.展开更多
基金jointly sponsored by the National Nature Scientific Foundation of China(Grant.Nos.41930971 and 41775061)the National Key Research and Development Program of China(Grant No.2018YFC1506402)。
文摘Valuable dropsonde data were obtained from multiple field campaigns targeting tropical cyclones,namely Higos,Nangka,Saudel,and Atsani,over the western North Pacific by the Hong Kong Observatory and Taiwan Central Weather Bureau in 2020.The conditional nonlinear optimal perturbation(CNOP)method has been utilized in real-time to identify the sensitive regions for targeting observations adhering to the procedure of real-time field campaigns for the first time.The observing system experiments were conducted to evaluate the effect of dropsonde data and CNOP sensitivity on TC forecasts in terms of track and intensity,using the Weather Research and Forecasting model.It is shown that the impact of assimilating all dropsonde data on both track and intensity forecasts is case-dependent.However,assimilation using only the dropsonde data inside the sensitive regions displays unanimously positive effects on both the track and intensity forecast,either of which obtains comparable benefits to or greatly reduces deterioration of the skill when assimilating all dropsonde data.Therefore,these results encourage us to further carry out targeting observations for the forecast of tropical cyclones according to CNOP sensitivity.
基金the National Science Foundation(NSF),the SOARS program,the Gwichyaa Zhee Gwich’in Tribal Government,and SLOAN for financial support.
文摘The characteristics and climatology of funnel clouds in Alaska were examined using operational radiosondes, surface meteorological observations, and reanalysis data. Funnel clouds occurred under weak synoptic forcing between May and September between 11 am and 6 pm Alaska Daylight Time with a maximum occurrence in July. They occurred under Convective Available Potential Energy >500 J·kg-1 and strong low-level wind shear. Characteristic atmospheric profiles during funnel cloud events served to develop a retrieval algorithm based on similarity testing. Out of more than 129,000 soundings between 1971 and 2014, 2724, 442, and 744 profiles were similar to the profiles of observed funnel cloud events in the Interior, Alaska West Coast, and Anchorage regions. While the number of reported funnel clouds has increased since 2000, the frequency of synoptic situations favorable for such events has decreased.
基金Supported by the National Natural Science Foundation of China under Grant No. 40575012Department of Science and Technology of Shandong Province under Grant No. 2007GG20008001
文摘Three supercell storms on 24 June 2004（0624）,28 June 2003（0628）,and 27 September 2002（0927） induced different damages in Shandong Province.Storm 0927 was inferior in size and intensity to storms 0628 and 0624.The structure and evolvement of the three storms were analyzed in detail based on the WSR98D radar data in combination with weather charts.The results show that mesoscale surface convergence triggered release of instable energy,which resulted in severe convection.During the development stage,storms 0927,0628,and 0624 displayed multi-cell propagation,single-cell evolution,and multi-cell mergence,respectively.The storm tracks were similar：they were all right-moving supercell storms,i.e.,moving at an angle of 30°-70° to the right of the mean wind and at a speed of about 45%-70% of the mean wind speed.In the mature stage,the maximum reflectivity appeared at the low level in storm 0927,mid level in storm 0628,and mid-upper level in storm 0624.These storms possessed almost all typical features of supercell storms：weak echo region（WER）,bounded weak echo region（BWER）,and mesocyclone.An organized mesocyclone formed at the middle height of an updraft,deepened gradually downward and upward,and became a typical mid-level mesocyclone with strong updrafts.The vertical structures of airflows in the three storms were similar,i.e.,significant convergence at low level,nearly pure rotation at mid level,and divergent rotation at upper level.However,signatures of mid-level horizontal airflows in the three storms were different：at mid level,there was a single vortex in storm 0628,but a double-vortex flow pattern was seen in storms 0927 and 0624.The horizontal structure of the double-vortex flow was hard to be blown away by the environmental airflow,and thus the storms could persist for a longer period of time than the single vortex storm.
文摘This report synthesizes global tropical cyclone(TC)tornado research and operational practices to date.Tornadoes are one of the secondary(and lesser researched)hazards contributing to the devastation TCs leave in their wake.While gale-force winds and storm surge produce the majority of damage and fatalities globally,TC tornadoes also pose a fatal threat,complicating evacuation plans and protective actions as the storm moves inland.Climatological studies characterize TC-spawned tornadoes as usually weak and short-lived,primarily originating from miniature supercells in the outer rainbands.These tornadic features pose challenges to forecasting and radar detection.Additionally,TC tornadoes can pose a threat to communities 12 h prior to and beyond 48 h after a TC makes landfall.Research,both basic and operational,has increased globally over the last few years in efforts to move from a climatological to ingredientsbased approach to detect and forecast TC tornadoes.While the United States has led the charge,given the increased exposure to tornadoes year round,other nations such as China,Japan,and Australia have increased their efforts to record and detect TC tornadoes.Despite these advancements,more work needs to be done globally to understand the TC environment conducive for tornadic activity.Recommendations for future forecasting and research for TC tornadoes include i)develop a comprehensive global tornado database to improve research and forecasting efforts;ii)apply innovative technology to detect tornadoes;and iii)conduct field campaigns to thoroughly sample TC tornado environments,particularly along coastlines.
