In this paper,the authors present the statistical characteristics of the buoyancy of outer-core convective-scale updrafts in numerically simulated sheared tropical cyclones(TCs).The total buoyancy is predominantly pos...In this paper,the authors present the statistical characteristics of the buoyancy of outer-core convective-scale updrafts in numerically simulated sheared tropical cyclones(TCs).The total buoyancy is predominantly positive in weak-to-strong ambient vertical shears,whereas much of the total buoyancy under an extreme shear environment becomes negative.Thermal buoyancy positively contributes to the total buoyancy value.For weakly and moderately sheared TCs,the updraft buoyancy is statistically significantly stronger downshear but smaller upshear.Such a downshear preference of strong buoyancy becomes less evident as the shear magnitude increases.The total buoyancy of updrafts shows a decreasing tendency with radius.Both thermal and dynamic buoyancy do not significantly correlate with vertically averaged vertical mass fluxes.This also leads to no significant correlation between the total buoyancy and vertical mass fluxes of outer-core updrafts.展开更多
Astronomical extreme events or phenomena include black holes as well as nebulae systems that resemble the Milky Way. Meteorological extreme events or phenomena include tornadoes and tropical cyclones. The new high ene...Astronomical extreme events or phenomena include black holes as well as nebulae systems that resemble the Milky Way. Meteorological extreme events or phenomena include tornadoes and tropical cyclones. The new high energy state of matter expanding outwards by spin jets from the two poles of an astronomical black hole, the new high energy state of matter in a funnel-shaped vortex showed a meteorological tornado expanding downwards from a rotated disk of cumulonimbus clouds, the new high energy state of matter in a tropical cyclone and the new high energy state of a nebulae system converging celestial materials are phenomena across disciplines and multiple time-space scales that have not yet been physically explained. In this paper, the theory of orthogonal collision in the rotational contraction continuum is used to unify the understanding of diverse extreme events or phenomena through a single dynamical mechanism, offering insights into natural processes across disciplines. In the field of astronomy, the orthogonal collision of two-beam rotating and contracting particles or stars associated with centripetal forces forms a new high-energy state of matter at the collision point and the new high-energy particles have expanding forces outward to both sides of the collision plane. In the field of meteorology, the orthogonal collision of multiple horizontally rotating and contracting airflows associated with centripetal forces forms a new high energy state of matter at the collision point as well as an updraft force and a downdraft force vertically. The updraft force and downdraft force formed by the collision of anomalous wet airflows in the lower atmosphere can well indicate tornado, thunderstorm and extreme precipitation. The orthogonal collision theory can be applied to explain new states of matter in disciplines from the astronomical scale to the meteorological scale and the Planck scale.展开更多
Hurricane Ida ferociously affected many south-eastern and eastern parts of the United States,making it one of the strongest hurricanes in recent years.Advanced forecast and warning tool has been used to track the path...Hurricane Ida ferociously affected many south-eastern and eastern parts of the United States,making it one of the strongest hurricanes in recent years.Advanced forecast and warning tool has been used to track the path of the ex-Hurricane,Ida,as it left New Orleans on its way towards the northeast,accurately predicting significant supercell development above New York City on September 01,2021.This advanced method accurately detected the area with the highest possible level of convective instability with 24-h lead time and even Level 5,devised in the categorical outlooks legend of the system.Therefore,an extreme level implied a very high probability of the local-scale hazard occurring above the NYC.Cloud model output fields(updrafts and downdrafts,wind shear,near-surface convergence,the vertical component of relative vorticity)show the rapid development of a strong supercell storm with rotating updrafts and a mesocyclone.The characteristic hook-shaped echo signature visible in the reflectivity patterns indicates a signal for a highly precipitable(HP)supercell with the possibility of tornado initiation.Open boundary conditions represent a good basis for simulating a tornado that evolved from a supercell storm,initialized with initial data obtained from a real-time simulation in the period when the bow echo and tornado-like signature occurred.Тhe modeled results agree well with the observations.展开更多
Differences in rainfall budgets between convective and stratiform regions of a torrential rainfall event were investigated using high-resolution simulation data produced by the Weather Research and Forecasting(WRF) mo...Differences in rainfall budgets between convective and stratiform regions of a torrential rainfall event were investigated using high-resolution simulation data produced by the Weather Research and Forecasting(WRF) model. The convective and stratiform regions were reasonably separated by the radar-based convective–stratiform partitioning method, and the threedimensional WRF-based precipitation equation combining water vapor and hydrometeor budgets was further used to analyze the rainfall budgets. The results showed that the magnitude of precipitation budget processes in the convective region was one order larger than that in the stratiform region. In convective/stratiform updraft regions, precipitation was mainly from the contribution of moisture-related processes, with a small negative contribution from cloud-related processes. In convective/stratiform downdraft regions, cloud-related processes played positive roles in precipitation, while moisture-related processes made a negative contribution. Moisture flux convergence played a dominant role in the moisture-related processes in convective or stratiform updraft regions, which was closely related to large-scale dynamics. Differences in cloud-related processes between convective and stratiform regions were more complex compared with those in moisture-related processes.Both liquid-and ice-phase microphysical processes were strong in convective/stratiform updraft regions, and ice-phase processes were dominant in convective/stratiform downdraft regions. There was strong net latent heating within almost the whole troposphere in updraft regions, especially in the convective updraft region, while the net latent heating(cooling) mainly existed above(below) the zero-layer in convective/stratiform downdraft regions.展开更多
The impact of the subtropical high (STH) on precipitation was investigated on a daily timescale using matched NCEP and the Global Precipitation Climatology Project (GPCP) datasets.Comparison of the conditional probabi...The impact of the subtropical high (STH) on precipitation was investigated on a daily timescale using matched NCEP and the Global Precipitation Climatology Project (GPCP) datasets.Comparison of the conditional probability (intensity) of precipitation under STH condi-tions with that under non-STH conditions suggests that the presence of the STH conditions has a limited impact on local precipitation.In the West Pacific Subtropical High (WPSH) and the North Atlantic Subtropical High (NASH),precipitation was only 30% lower under STH conditions than under non-STH conditions.The STH conditions had somewhat more impact on precipitation intensity,but it was still 50% less than the intensity under non-STH conditions (mean of roughly 5 mm d 1).Pre-cipitation under STH conditions was found to be highly correlated with vertical motion.Active updrafts occurring even under STH conditions are essential for frequent oc-currences and moderate intensities of precipitation.展开更多
The variation of toxic pollutants emission during a feeding cycle was examined by field monitoring from a batch feeding updraft fixed bed gasifier for disposing rural domestic solid waste. Results showed that the cont...The variation of toxic pollutants emission during a feeding cycle was examined by field monitoring from a batch feeding updraft fixed bed gasifier for disposing rural domestic solid waste. Results showed that the content of oxygen in flue gas gradually increased, while SO_2 and HCl in flue gas decreased with time after feeding in a whole feeding cycle. Although large amount of CO was produced during the gasifying, low CO content in flue gas could be obtained after the heat treatment with an electric heating device. The distribution characteristics of dioxin congeners in flue gas indicted the re-synthesis of dioxins after flue gas heating, and the increase of oxygen promoted the synthesis of dioxins. The emission content of dioxins could meet the standard(0.1 ng I-TEQ·m^(-3),GB18458-2014) of China when the oxygen content was controlled below 8.3%. Hence, for a batch feeding gasifier,low oxygen condition should be offered by reducing air intake at the later stage of feeding cycle in order to decrease the re-synthesis of dioxins after the flue gas heating.展开更多
The purpose of this study is to improve the efficiency of the power generation system of a solar tower using fluid dynamics. The power generation system of a solar tower can be designed and constructed at relatively l...The purpose of this study is to improve the efficiency of the power generation system of a solar tower using fluid dynamics. The power generation system of a solar tower can be designed and constructed at relatively low cost. However, the energy output tends to be low for its physical size compared with other renewable energy production systems. The technical and scientific improvement of these types of generation systems has lost its momentum since the shutdown of the wellknown Spanish pilot plant “Manzanares Solar Chimney” in 1989, although it still has the potential to play a role in renewable energy in the future. We have focused on the tower component of the system to seek possible enhancements of the power output of the internal turbine. As a result of our fluid dynamic shape optimization, a diffuser-shaped tower was employed to increase the internal flow speed of a scaled model. The results show a remarkable improvement in the power output of the internal wind turbine.展开更多
The original online version of this article (Masataka Motoyama, Kenichiro Sugitani, Yuji Ohya, et al. (2014) “Improving the Power Generation Performance of a Solar Tower Using Thermal Updraft Wind”, 2014, 6, 362-370...The original online version of this article (Masataka Motoyama, Kenichiro Sugitani, Yuji Ohya, et al. (2014) “Improving the Power Generation Performance of a Solar Tower Using Thermal Updraft Wind”, 2014, 6, 362-370. http://dx.doi.org/10.4236/epe.2014.611031) was published in October, 2014.The author wishes to correct the following error in text and Figures 9-11.展开更多
Dual-Doppler radar detection and wind-field retrieval techniques are crucial for capturing small-scale structures within convective systems.The spatiotemporal resolution of radar data is a key factor influencing the a...Dual-Doppler radar detection and wind-field retrieval techniques are crucial for capturing small-scale structures within convective systems.The spatiotemporal resolution of radar data is a key factor influencing the accuracy of wind-field observations.Recently,an advanced X-band phased-array weather radar system was deployed in Foshan,Guangdong Province,China,comprising a central collaborative control unit and multiple networked phased-array radar front-ends.These radar front-ends work together to scan a common area,achieving a maximum data time difference of 5 s and a volume scan interval of 30 s,thereby providing three-dimensional wind-field data with higher spatiotemporal resolution and greater accuracy than achieved using traditional methods.This study utilized the X-band phased-array weather radar system to analyze the development of a substantial hailstorm that occurred over Foshan on 26 March 2022.Analysis indicated that hail cloud activity intensified considerably after 1442 local time,with the maximum reflectivity factor exceeding 60 dBZ above the altitude of the-20℃ level,and reflectivity continued to increase over the subsequent 12 min.More precise information on the flow-field structure of the storm was obtained by examining the X-band radar data.The temporal and vertical variations in the maximum reflectivity factor,updraft velocity,vertical wind shear,and horizontal wind speed within a hailstorm cloud were scrutinized.The results show that the altitude,intensity,and range of the main updraft area increased as the storm core ascended.Concurrently,the vertical wind shear at mid-lower levels of the storm became more pronounced as the altitude of the strong radar echo center increased prior to the peak of the updraft.Therefore,a new hail warning index was developed by using the vertical wind shear,and the index can be used to issue warnings up to 12 min earlier than achievable using traditional methods detecting increases in hailstorm intensity.展开更多
Devastating tornadoes in China have received growing attention in recent years, but little is known about their formation, structure, and evolution on the tornadic scale. Most of these tornadoes develop within the Eas...Devastating tornadoes in China have received growing attention in recent years, but little is known about their formation, structure, and evolution on the tornadic scale. Most of these tornadoes develop within the East Asian monsoon regime, in an environment quite different from tornadoes in the U.S. In this study, we used an idealized, highresolution（25-m grid spacing） numerical simulation to investigate the deadly EF4（Enhanced Fujita scale category 4）tornado that occurred on 23 June 2016 and claimed 99 lives in Yancheng, Jiangsu Province. A tornadic supercell developed in the simulation that had striking similarities to radar observations. The violent tornado in Funing County was reproduced, exceeding EF4（74 ms–1）, consistent with the on-site damage survey. It was accompanied by a funnel cloud that extended to the surface, and exhibited a double-helix vorticity structure. The signal of tornado genesis was found first at the cloud base in the pressure perturbation field, and then developed both upward and downward in terms of maximum vertical velocity overlapping with the intense vertical vorticity centers. The tornado＇s demise was found to accompany strong downdrafts overlapping with the intense vorticity centers. One of the interesting findings of this work is that a violent surface vortex was able to be generated and maintained, even though the simulation employed a free-slip lower boundary condition. The success of this simulation, despite using an idealized numerical approach, provides a means to investigate more historical tornadoes in China.展开更多
The rate of neutralized charge by lightning（RNCL） is an important parameter indicating the intensity of lightning activity.The total charging rate（CR）,the CR of one kind of polarity（e.g.,negative） charge（CROP）...The rate of neutralized charge by lightning（RNCL） is an important parameter indicating the intensity of lightning activity.The total charging rate（CR）,the CR of one kind of polarity（e.g.,negative） charge（CROP）,and the outflow rate of charge on precipitation（ORCP） are proposed as key factors impacting RNCL,based on the principle of conservation of one kind of polarity charge in a thunderstorm.In this paper,the impacts of updraft on CR and CROP are analyzed by using a 3D cloud resolution model for a strong storm that occurred in Beijing on 6 September 2008.The results show that updraft both promotes and inhibits RNCL at the same time.（1） Updraft always has a positive influence on CR.The correlation coefficient between the updraft volume and CR can reach 0.96.Strengthening of the updraft facilitates strengthening of RNCL through this positive influence.（2） Strengthening of the updraft also promotes reinforcement of CROP.The correlation coefficient between the updraft volume and CROP is high（about0.9）,but this promotion restrains the strengthening of RNCL because the strengthening of CROP will,most of the time,inhibit the increasing of RNCL.（3） Additionally,increasing of ORCP depresses the strengthening of RNCL.In terms of magnitude,the peak of ORCP is equal to the peak of CR.Because precipitation mainly appears after the lightning activity finishes,the depression effect of ORCP on RNCL can be ignored during the active lightning period.展开更多
The purpose of this study was to understand the reasons why frequent positive cloud-to-ground(+CG) flashes occur in severe thunderstorms. A three-dimensional dynamics-electrification coupled model was used to simulate...The purpose of this study was to understand the reasons why frequent positive cloud-to-ground(+CG) flashes occur in severe thunderstorms. A three-dimensional dynamics-electrification coupled model was used to simulate a severe thunderstorm to permit analysis of the conditions that might easily cause +CG flashes. The results showed that strong updrafts play an important role in the occurrence of intracloud flashes. However, frequent +CG flashes require not only strong updrafts but also strong downdrafts in the lower cloud region, conditions that correspond to the later phase of the mature stage and the period of the heaviest solid precipitation of a thunderstorm. During this stage, strong updrafts elevated each charge area in the updraft region to a higher level, which resulted in an inverted tripole charge structure. A wide mid-level region of strong positive charge caused largely by positively charged graupel, presented in the middle of the updraft region because of a non-inductive ice-ice collisional charging mechanism. The charge structure in the downdraft region was consistently more complex and revealed several vertically stacked charge regions, alternating in polarity. Much of the graupel/hail outside the updrafts was lowered to cloud-base by strong downdrafts. In this area, the graupel/hail was charged negatively because of the transportation of negatively charged graupel/hail from higher regions of negative charge in the updrafts, and via the inductive charging mechanism of collisions between graupel/hail and cloud droplets at the bottom of the cloud. Consequently, a large region of negative charge formed near the ground. This meant that +CG flashes were initiated more easily in the lower inverted dipole, i.e., the middle region of positive charge and lower region of negative charge. Frequent +CG flashes began almost synchronously with dramatic increases in the storm updrafts, hail volume, and total flash rate. Therefore, the occurrence of +CG flashes appears a good indicator of storm intensification and it could have some use as a predictor of severe weather in the form of hail.展开更多
Mêdog County,with its mountains and valleys,is located in the southeastern Tibetan Plateau(TP)and at the lower reaches of the Yarlung Zangbo River.This area has the highest annual rainfall amount over the TP,and ...Mêdog County,with its mountains and valleys,is located in the southeastern Tibetan Plateau(TP)and at the lower reaches of the Yarlung Zangbo River.This area has the highest annual rainfall amount over the TP,and in situ measurements are very scarce due to frequent debris flows and transportation difficulties.A monitoring campaign focused on cloud and precipitation observations was established in Mêdog in 2019 as a part of the Second Tibetan Plateau Scientific Expedition and Research Program.This paper evaluates the accuracy of micro rain radar(MRR)measurements and investigates the variations in precipitation vertical structure in Mêdog using observations collected from the MRR,disdrometer,and rain gauges in summer 2021.The measurements from the three instruments show a strong consistency,with correlation coefficients exceeding 0.93.Although the profiles of integral rain parameters for different rain rate categories in Mêdog are similar to those in other regions,the vertical evolution of raindrop size distributions shows significant differences.For lightest rain,the evaporation of small raindrops and breakup of large raindrops are clear during their descent.For the rainfall rate category of 0.2–2.0 mm h−1(2.0–20.0 mm h−1),concentrations of small and medium(large)drops show almost uniform vertical structures,while the large(medium)drop number displays a positive(negative)gradient.A disturbance at height of 1.5–2.0 km above ground level(AGL)is observed in the heavy rainfall due to strong updrafts.In general,the MRR measurements in Mêdog are robust.The raindrop breakup process is more apparent in Mêdog than in other regions,resulting in high concentration of sizelimited raindrops.In addition,it is found that the interaction between steep terrain and Mêdog convective rain causes the strong updrafts between 1.5 and 2.0 km AGL.展开更多
An updraft gasifier was employed to treat 3 kg of dried rice husk per batch with different types of gasifying agents such as air,steam/air,and air with dolomite catalyst addition at various operating conditions.The H2...An updraft gasifier was employed to treat 3 kg of dried rice husk per batch with different types of gasifying agents such as air,steam/air,and air with dolomite catalyst addition at various operating conditions.The H2 content,low heating value,and H2/CO ratio in syngas were compared to determine the most effective solution to enhance the H2 production from rice husk gasification.The presence of dolomite in air gasification produced the highest H2 content in the product gas,up to 15.4 mol%,followed by 7.08 and 3.6 mol%when steam/air and air standalone were used as gasifying agents,respectively.The higher low heating value of syngas 5.1 MJ/Nm3 was observed in catalytic air gasification compared to 3.6 MJ/Nm3 when steam was added.The optimal operation condition was reported at an airflow rate of 3 m3/h and a catalyst mixing ratio of 15%.展开更多
Based on the National Centers for Envioromental Prediction（NCEP）Reanalysis 2 daily data and the Global Precipitation Climatology Project（GPCP）1 Degree Daily（1DD）precipitation data from 1997 to 2006,seasonal char...Based on the National Centers for Envioromental Prediction（NCEP）Reanalysis 2 daily data and the Global Precipitation Climatology Project（GPCP）1 Degree Daily（1DD）precipitation data from 1997 to 2006,seasonal characteristics of precipitation occurring in the core area of the subtropical high（STH）were investigated by the frequency analysis method.The results indicate that precipitation occurs in the core area of the STH in each season,which is inconsistent with the common knowledge.In summer,there exists 40%–80%of the precipitation frequency in the STH,against less than 50%in other seasons.Generally,the seasonal mean rain rate inside the STH is about 1–2 mm day -1 in winter and less than 4 mm day -1 in summer,which contributes to about 30%–90%of the local total precipitation.In summer,such a contribution is about 50%–90%,and it is less than 40%in other seasons.Statistically,the occurrence frequency of the updraft within the core area of the STH varies from 25%to 75%in summer and less than 25%in other seasons. The results also reveal that there is about 30%of the STH frequency over the eastern China in summer, and the corresponding precipitation and updraft frequencies are 25%and 15%respectively.This is the so-called unique precipitation pattern in summer in eastern China,i.e.,precipitation is controlled by the core of the STH. Additionally,more than half of the precipitation occurring in the STH is accompanied with updraft at 500 hPa while less than half is with downdraft at 500 hPa.The former may represent deep precipitation whereas the latter may hint shallow precipitation in the core area of the STH.展开更多
During a hailstorm event,near-surface meso-γvortices along a convergence line interact with hail cells.Herein we investigate this interaction by using observational data and a high-resolution simulation of a hailstor...During a hailstorm event,near-surface meso-γvortices along a convergence line interact with hail cells.Herein we investigate this interaction by using observational data and a high-resolution simulation of a hailstorm that occurred over Taizhou(Zhejiang,China)on 19 March 2014.The 10-m surface wind data from automatic weather stations show that several meso-γvortices or vortex-like disturbances existed over the convergence zone and played a vital role in the evolution of the hailstorm and the location of the hail.The model results agree with the observations and present a closer correlation between the hail and the low-level meso-γvortices than those observed.The model simulation indicates that such low-level meso-γvortices can be used to predict the next 10-min hail fallout zone.The lowlevel meso-γvortices originated over the convergence zone and then fed back into the convergence field and provoked a stronger updraft.Vorticity was initiated primarily by stretching and was extended by tilting.A three-dimensional(3-D)flow analysis shows that the existence of low-level meso-γvortices could help enhance a local updraft.Furthermore,the simulation reveals that the low-level meso-γvortices formed in the bounded weak echo region(WER)at the front of the hail cell,enhancing convergence and strengthening updrafts.Graupel was broadly located between the 0°C isothermal line and the top of the clouds,roughly between the 0 and-20°C isothermal lines.Accordingly,the hailstones grew rapidly.The suitable environment and the positive effect of the meso-γvortices on the updrafts enabled hailstorm formation.展开更多
基金supported by the National Key Research and Development Program of China [grant numbers 2017YFC1501601 and 2015CB452803]the National Natural Science Foundation of China [grant numbers41475058,41730961,and 41875054]+1 种基金the Basic Research Fund of the Chinese Academy of Meteorological Sciences[grant number 2016Z003]the Top-notch Academic Programs Project of Jiangsu Higher Education Institutions(TAPP)
文摘In this paper,the authors present the statistical characteristics of the buoyancy of outer-core convective-scale updrafts in numerically simulated sheared tropical cyclones(TCs).The total buoyancy is predominantly positive in weak-to-strong ambient vertical shears,whereas much of the total buoyancy under an extreme shear environment becomes negative.Thermal buoyancy positively contributes to the total buoyancy value.For weakly and moderately sheared TCs,the updraft buoyancy is statistically significantly stronger downshear but smaller upshear.Such a downshear preference of strong buoyancy becomes less evident as the shear magnitude increases.The total buoyancy of updrafts shows a decreasing tendency with radius.Both thermal and dynamic buoyancy do not significantly correlate with vertically averaged vertical mass fluxes.This also leads to no significant correlation between the total buoyancy and vertical mass fluxes of outer-core updrafts.
文摘Astronomical extreme events or phenomena include black holes as well as nebulae systems that resemble the Milky Way. Meteorological extreme events or phenomena include tornadoes and tropical cyclones. The new high energy state of matter expanding outwards by spin jets from the two poles of an astronomical black hole, the new high energy state of matter in a funnel-shaped vortex showed a meteorological tornado expanding downwards from a rotated disk of cumulonimbus clouds, the new high energy state of matter in a tropical cyclone and the new high energy state of a nebulae system converging celestial materials are phenomena across disciplines and multiple time-space scales that have not yet been physically explained. In this paper, the theory of orthogonal collision in the rotational contraction continuum is used to unify the understanding of diverse extreme events or phenomena through a single dynamical mechanism, offering insights into natural processes across disciplines. In the field of astronomy, the orthogonal collision of two-beam rotating and contracting particles or stars associated with centripetal forces forms a new high-energy state of matter at the collision point and the new high-energy particles have expanding forces outward to both sides of the collision plane. In the field of meteorology, the orthogonal collision of multiple horizontally rotating and contracting airflows associated with centripetal forces forms a new high energy state of matter at the collision point as well as an updraft force and a downdraft force vertically. The updraft force and downdraft force formed by the collision of anomalous wet airflows in the lower atmosphere can well indicate tornado, thunderstorm and extreme precipitation. The orthogonal collision theory can be applied to explain new states of matter in disciplines from the astronomical scale to the meteorological scale and the Planck scale.
文摘Hurricane Ida ferociously affected many south-eastern and eastern parts of the United States,making it one of the strongest hurricanes in recent years.Advanced forecast and warning tool has been used to track the path of the ex-Hurricane,Ida,as it left New Orleans on its way towards the northeast,accurately predicting significant supercell development above New York City on September 01,2021.This advanced method accurately detected the area with the highest possible level of convective instability with 24-h lead time and even Level 5,devised in the categorical outlooks legend of the system.Therefore,an extreme level implied a very high probability of the local-scale hazard occurring above the NYC.Cloud model output fields(updrafts and downdrafts,wind shear,near-surface convergence,the vertical component of relative vorticity)show the rapid development of a strong supercell storm with rotating updrafts and a mesocyclone.The characteristic hook-shaped echo signature visible in the reflectivity patterns indicates a signal for a highly precipitable(HP)supercell with the possibility of tornado initiation.Open boundary conditions represent a good basis for simulating a tornado that evolved from a supercell storm,initialized with initial data obtained from a real-time simulation in the period when the bow echo and tornado-like signature occurred.Тhe modeled results agree well with the observations.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA23090101)the Key Research Program of the Chinese Academy of Sciences (Grant No. KZZD-EW-05-01)the National Basic Research Program of China (973 Program) (Grant No. 2015CB452804)
文摘Differences in rainfall budgets between convective and stratiform regions of a torrential rainfall event were investigated using high-resolution simulation data produced by the Weather Research and Forecasting(WRF) model. The convective and stratiform regions were reasonably separated by the radar-based convective–stratiform partitioning method, and the threedimensional WRF-based precipitation equation combining water vapor and hydrometeor budgets was further used to analyze the rainfall budgets. The results showed that the magnitude of precipitation budget processes in the convective region was one order larger than that in the stratiform region. In convective/stratiform updraft regions, precipitation was mainly from the contribution of moisture-related processes, with a small negative contribution from cloud-related processes. In convective/stratiform downdraft regions, cloud-related processes played positive roles in precipitation, while moisture-related processes made a negative contribution. Moisture flux convergence played a dominant role in the moisture-related processes in convective or stratiform updraft regions, which was closely related to large-scale dynamics. Differences in cloud-related processes between convective and stratiform regions were more complex compared with those in moisture-related processes.Both liquid-and ice-phase microphysical processes were strong in convective/stratiform updraft regions, and ice-phase processes were dominant in convective/stratiform downdraft regions. There was strong net latent heating within almost the whole troposphere in updraft regions, especially in the convective updraft region, while the net latent heating(cooling) mainly existed above(below) the zero-layer in convective/stratiform downdraft regions.
基金supported by Special Funds for Public Welfare of China (Grant No.GYHY-QX-2007)the National Natural Science Foundation of China (Grant Nos.40730950,40675027,and 40805007)
文摘The impact of the subtropical high (STH) on precipitation was investigated on a daily timescale using matched NCEP and the Global Precipitation Climatology Project (GPCP) datasets.Comparison of the conditional probability (intensity) of precipitation under STH condi-tions with that under non-STH conditions suggests that the presence of the STH conditions has a limited impact on local precipitation.In the West Pacific Subtropical High (WPSH) and the North Atlantic Subtropical High (NASH),precipitation was only 30% lower under STH conditions than under non-STH conditions.The STH conditions had somewhat more impact on precipitation intensity,but it was still 50% less than the intensity under non-STH conditions (mean of roughly 5 mm d 1).Pre-cipitation under STH conditions was found to be highly correlated with vertical motion.Active updrafts occurring even under STH conditions are essential for frequent oc-currences and moderate intensities of precipitation.
基金Supported by the Science and Technology Planning Project of Guangdong Province,China(2013B090600134)the National Natural Science Foundation of China(51608223)the Fund for Basic Scientific Research Business of Central Institutes of Environmental Protection(PM-zx 703-201602-050)
文摘The variation of toxic pollutants emission during a feeding cycle was examined by field monitoring from a batch feeding updraft fixed bed gasifier for disposing rural domestic solid waste. Results showed that the content of oxygen in flue gas gradually increased, while SO_2 and HCl in flue gas decreased with time after feeding in a whole feeding cycle. Although large amount of CO was produced during the gasifying, low CO content in flue gas could be obtained after the heat treatment with an electric heating device. The distribution characteristics of dioxin congeners in flue gas indicted the re-synthesis of dioxins after flue gas heating, and the increase of oxygen promoted the synthesis of dioxins. The emission content of dioxins could meet the standard(0.1 ng I-TEQ·m^(-3),GB18458-2014) of China when the oxygen content was controlled below 8.3%. Hence, for a batch feeding gasifier,low oxygen condition should be offered by reducing air intake at the later stage of feeding cycle in order to decrease the re-synthesis of dioxins after the flue gas heating.
文摘The purpose of this study is to improve the efficiency of the power generation system of a solar tower using fluid dynamics. The power generation system of a solar tower can be designed and constructed at relatively low cost. However, the energy output tends to be low for its physical size compared with other renewable energy production systems. The technical and scientific improvement of these types of generation systems has lost its momentum since the shutdown of the wellknown Spanish pilot plant “Manzanares Solar Chimney” in 1989, although it still has the potential to play a role in renewable energy in the future. We have focused on the tower component of the system to seek possible enhancements of the power output of the internal turbine. As a result of our fluid dynamic shape optimization, a diffuser-shaped tower was employed to increase the internal flow speed of a scaled model. The results show a remarkable improvement in the power output of the internal wind turbine.
文摘The original online version of this article (Masataka Motoyama, Kenichiro Sugitani, Yuji Ohya, et al. (2014) “Improving the Power Generation Performance of a Solar Tower Using Thermal Updraft Wind”, 2014, 6, 362-370. http://dx.doi.org/10.4236/epe.2014.611031) was published in October, 2014.The author wishes to correct the following error in text and Figures 9-11.
基金Supported by the Joint Fund Project of National Natural Science Foundation of China(U2142210).
文摘Dual-Doppler radar detection and wind-field retrieval techniques are crucial for capturing small-scale structures within convective systems.The spatiotemporal resolution of radar data is a key factor influencing the accuracy of wind-field observations.Recently,an advanced X-band phased-array weather radar system was deployed in Foshan,Guangdong Province,China,comprising a central collaborative control unit and multiple networked phased-array radar front-ends.These radar front-ends work together to scan a common area,achieving a maximum data time difference of 5 s and a volume scan interval of 30 s,thereby providing three-dimensional wind-field data with higher spatiotemporal resolution and greater accuracy than achieved using traditional methods.This study utilized the X-band phased-array weather radar system to analyze the development of a substantial hailstorm that occurred over Foshan on 26 March 2022.Analysis indicated that hail cloud activity intensified considerably after 1442 local time,with the maximum reflectivity factor exceeding 60 dBZ above the altitude of the-20℃ level,and reflectivity continued to increase over the subsequent 12 min.More precise information on the flow-field structure of the storm was obtained by examining the X-band radar data.The temporal and vertical variations in the maximum reflectivity factor,updraft velocity,vertical wind shear,and horizontal wind speed within a hailstorm cloud were scrutinized.The results show that the altitude,intensity,and range of the main updraft area increased as the storm core ascended.Concurrently,the vertical wind shear at mid-lower levels of the storm became more pronounced as the altitude of the strong radar echo center increased prior to the peak of the updraft.Therefore,a new hail warning index was developed by using the vertical wind shear,and the index can be used to issue warnings up to 12 min earlier than achievable using traditional methods detecting increases in hailstorm intensity.
基金Supported by the National Natural Science Foundation of China(41705028,41405095,and 41405006)Basic Research Fund of the Chinese Academy of Meteorological Sciences[2017Y018,2015Z003,and 2017Z017(2017LASW-A02)]
文摘Devastating tornadoes in China have received growing attention in recent years, but little is known about their formation, structure, and evolution on the tornadic scale. Most of these tornadoes develop within the East Asian monsoon regime, in an environment quite different from tornadoes in the U.S. In this study, we used an idealized, highresolution（25-m grid spacing） numerical simulation to investigate the deadly EF4（Enhanced Fujita scale category 4）tornado that occurred on 23 June 2016 and claimed 99 lives in Yancheng, Jiangsu Province. A tornadic supercell developed in the simulation that had striking similarities to radar observations. The violent tornado in Funing County was reproduced, exceeding EF4（74 ms–1）, consistent with the on-site damage survey. It was accompanied by a funnel cloud that extended to the surface, and exhibited a double-helix vorticity structure. The signal of tornado genesis was found first at the cloud base in the pressure perturbation field, and then developed both upward and downward in terms of maximum vertical velocity overlapping with the intense vertical vorticity centers. The tornado＇s demise was found to accompany strong downdrafts overlapping with the intense vorticity centers. One of the interesting findings of this work is that a violent surface vortex was able to be generated and maintained, even though the simulation employed a free-slip lower boundary condition. The success of this simulation, despite using an idealized numerical approach, provides a means to investigate more historical tornadoes in China.
基金Supported by the National Natural Science Foundation of China(41205001)National(Key)Basic Research and Development(973)Program of China(2014CB441406)+1 种基金National Major Scientific Instruments and Equipment Development Special(61327810)Basic Research Funds of CAMS(2012Y005 and 2013Z006)
文摘The rate of neutralized charge by lightning（RNCL） is an important parameter indicating the intensity of lightning activity.The total charging rate（CR）,the CR of one kind of polarity（e.g.,negative） charge（CROP）,and the outflow rate of charge on precipitation（ORCP） are proposed as key factors impacting RNCL,based on the principle of conservation of one kind of polarity charge in a thunderstorm.In this paper,the impacts of updraft on CR and CROP are analyzed by using a 3D cloud resolution model for a strong storm that occurred in Beijing on 6 September 2008.The results show that updraft both promotes and inhibits RNCL at the same time.（1） Updraft always has a positive influence on CR.The correlation coefficient between the updraft volume and CR can reach 0.96.Strengthening of the updraft facilitates strengthening of RNCL through this positive influence.（2） Strengthening of the updraft also promotes reinforcement of CROP.The correlation coefficient between the updraft volume and CROP is high（about0.9）,but this promotion restrains the strengthening of RNCL because the strengthening of CROP will,most of the time,inhibit the increasing of RNCL.（3） Additionally,increasing of ORCP depresses the strengthening of RNCL.In terms of magnitude,the peak of ORCP is equal to the peak of CR.Because precipitation mainly appears after the lightning activity finishes,the depression effect of ORCP on RNCL can be ignored during the active lightning period.
基金supported by the National Key Basic Research Program of China (Grant No. 2014CB441403)the National Natural Science Foundation of China (Grant No. 41275008)+1 种基金R&D Special Fund for Public Welfare Industry (Grant No. GYHY201306069)Open Project of Key Laboratory of Meteorological Disaster of Ministry of Education (Grant No. KLME1004)
文摘The purpose of this study was to understand the reasons why frequent positive cloud-to-ground(+CG) flashes occur in severe thunderstorms. A three-dimensional dynamics-electrification coupled model was used to simulate a severe thunderstorm to permit analysis of the conditions that might easily cause +CG flashes. The results showed that strong updrafts play an important role in the occurrence of intracloud flashes. However, frequent +CG flashes require not only strong updrafts but also strong downdrafts in the lower cloud region, conditions that correspond to the later phase of the mature stage and the period of the heaviest solid precipitation of a thunderstorm. During this stage, strong updrafts elevated each charge area in the updraft region to a higher level, which resulted in an inverted tripole charge structure. A wide mid-level region of strong positive charge caused largely by positively charged graupel, presented in the middle of the updraft region because of a non-inductive ice-ice collisional charging mechanism. The charge structure in the downdraft region was consistently more complex and revealed several vertically stacked charge regions, alternating in polarity. Much of the graupel/hail outside the updrafts was lowered to cloud-base by strong downdrafts. In this area, the graupel/hail was charged negatively because of the transportation of negatively charged graupel/hail from higher regions of negative charge in the updrafts, and via the inductive charging mechanism of collisions between graupel/hail and cloud droplets at the bottom of the cloud. Consequently, a large region of negative charge formed near the ground. This meant that +CG flashes were initiated more easily in the lower inverted dipole, i.e., the middle region of positive charge and lower region of negative charge. Frequent +CG flashes began almost synchronously with dramatic increases in the storm updrafts, hail volume, and total flash rate. Therefore, the occurrence of +CG flashes appears a good indicator of storm intensification and it could have some use as a predictor of severe weather in the form of hail.
基金Supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(2019QZKK0105)National Key Research and Development Program of China(2018YFC1505702).
文摘Mêdog County,with its mountains and valleys,is located in the southeastern Tibetan Plateau(TP)and at the lower reaches of the Yarlung Zangbo River.This area has the highest annual rainfall amount over the TP,and in situ measurements are very scarce due to frequent debris flows and transportation difficulties.A monitoring campaign focused on cloud and precipitation observations was established in Mêdog in 2019 as a part of the Second Tibetan Plateau Scientific Expedition and Research Program.This paper evaluates the accuracy of micro rain radar(MRR)measurements and investigates the variations in precipitation vertical structure in Mêdog using observations collected from the MRR,disdrometer,and rain gauges in summer 2021.The measurements from the three instruments show a strong consistency,with correlation coefficients exceeding 0.93.Although the profiles of integral rain parameters for different rain rate categories in Mêdog are similar to those in other regions,the vertical evolution of raindrop size distributions shows significant differences.For lightest rain,the evaporation of small raindrops and breakup of large raindrops are clear during their descent.For the rainfall rate category of 0.2–2.0 mm h−1(2.0–20.0 mm h−1),concentrations of small and medium(large)drops show almost uniform vertical structures,while the large(medium)drop number displays a positive(negative)gradient.A disturbance at height of 1.5–2.0 km above ground level(AGL)is observed in the heavy rainfall due to strong updrafts.In general,the MRR measurements in Mêdog are robust.The raindrop breakup process is more apparent in Mêdog than in other regions,resulting in high concentration of sizelimited raindrops.In addition,it is found that the interaction between steep terrain and Mêdog convective rain causes the strong updrafts between 1.5 and 2.0 km AGL.
文摘An updraft gasifier was employed to treat 3 kg of dried rice husk per batch with different types of gasifying agents such as air,steam/air,and air with dolomite catalyst addition at various operating conditions.The H2 content,low heating value,and H2/CO ratio in syngas were compared to determine the most effective solution to enhance the H2 production from rice husk gasification.The presence of dolomite in air gasification produced the highest H2 content in the product gas,up to 15.4 mol%,followed by 7.08 and 3.6 mol%when steam/air and air standalone were used as gasifying agents,respectively.The higher low heating value of syngas 5.1 MJ/Nm3 was observed in catalytic air gasification compared to 3.6 MJ/Nm3 when steam was added.The optimal operation condition was reported at an airflow rate of 3 m3/h and a catalyst mixing ratio of 15%.
基金the Special Funds for Public Welfare of China under Grant No.GYHY200706032the National Natural Science Foundation of China under Grant Nos.40730950,40605010,and 40675027
文摘Based on the National Centers for Envioromental Prediction（NCEP）Reanalysis 2 daily data and the Global Precipitation Climatology Project（GPCP）1 Degree Daily（1DD）precipitation data from 1997 to 2006,seasonal characteristics of precipitation occurring in the core area of the subtropical high（STH）were investigated by the frequency analysis method.The results indicate that precipitation occurs in the core area of the STH in each season,which is inconsistent with the common knowledge.In summer,there exists 40%–80%of the precipitation frequency in the STH,against less than 50%in other seasons.Generally,the seasonal mean rain rate inside the STH is about 1–2 mm day -1 in winter and less than 4 mm day -1 in summer,which contributes to about 30%–90%of the local total precipitation.In summer,such a contribution is about 50%–90%,and it is less than 40%in other seasons.Statistically,the occurrence frequency of the updraft within the core area of the STH varies from 25%to 75%in summer and less than 25%in other seasons. The results also reveal that there is about 30%of the STH frequency over the eastern China in summer, and the corresponding precipitation and updraft frequencies are 25%and 15%respectively.This is the so-called unique precipitation pattern in summer in eastern China,i.e.,precipitation is controlled by the core of the STH. Additionally,more than half of the precipitation occurring in the STH is accompanied with updraft at 500 hPa while less than half is with downdraft at 500 hPa.The former may represent deep precipitation whereas the latter may hint shallow precipitation in the core area of the STH.
基金Supported by the National Natural Science Foundation of China(41175047)National Key Basic Research and Development Program of China(2013CB430104)+3 种基金Forecaster Special Project of China Meteorological Administration Forecaster(CMAYBY2019-47)Zhejiang Science and Technology Plan Project(2016QN02)Major Project of Zhejiang Provincial Department of Science and Technology(2017C03035)Hangzhou Weather Bureau(ZJZBC-19-9103)。
文摘During a hailstorm event,near-surface meso-γvortices along a convergence line interact with hail cells.Herein we investigate this interaction by using observational data and a high-resolution simulation of a hailstorm that occurred over Taizhou(Zhejiang,China)on 19 March 2014.The 10-m surface wind data from automatic weather stations show that several meso-γvortices or vortex-like disturbances existed over the convergence zone and played a vital role in the evolution of the hailstorm and the location of the hail.The model results agree with the observations and present a closer correlation between the hail and the low-level meso-γvortices than those observed.The model simulation indicates that such low-level meso-γvortices can be used to predict the next 10-min hail fallout zone.The lowlevel meso-γvortices originated over the convergence zone and then fed back into the convergence field and provoked a stronger updraft.Vorticity was initiated primarily by stretching and was extended by tilting.A three-dimensional(3-D)flow analysis shows that the existence of low-level meso-γvortices could help enhance a local updraft.Furthermore,the simulation reveals that the low-level meso-γvortices formed in the bounded weak echo region(WER)at the front of the hail cell,enhancing convergence and strengthening updrafts.Graupel was broadly located between the 0°C isothermal line and the top of the clouds,roughly between the 0 and-20°C isothermal lines.Accordingly,the hailstones grew rapidly.The suitable environment and the positive effect of the meso-γvortices on the updrafts enabled hailstorm formation.
