Based on the analysis of multiple tropical cyclone(MTC)events in the South China Sea and Northwest Pacific Ocean during 1979-2019,this study classfies periods of the tropical cyclone(TC)events into active,normal,and i...Based on the analysis of multiple tropical cyclone(MTC)events in the South China Sea and Northwest Pacific Ocean during 1979-2019,this study classfies periods of the tropical cyclone(TC)events into active,normal,and inactive phases.To analyze the spatial distribution of associated anomalous variables and indices,an anomaly-based variable model is employed.Anomalies of 850 hPa vorticity,850 hPa water vapor flux divergence,and 400 hPa vertical velocity are selected as optimal predictors with physical significance.From these predictors,a physical model for the original MTC development is established.The results show that during the period of MTC development,a stable warm-core anomaly persists at 300 hPa,with a“warm tongue”extending downward as far as 700 hPa.The upper-level high-pressure anomaly center does not completely overlap with the low-pressure anomaly center at lower levels until TC genesis approaches.In addition,the 500-1000 hPa water vapor flux initially exhibits a negative anomaly,which facilitates water vapor to accumulate.A negative vertical velocity anomaly then develops,promoting the upward motion that gradually stabilizes and expands to a wider range.Ultimately,these processes lead to the formation of a positive vorticity anomaly,signifying a TC’s formation.Among the three key factors,the water vapor flux divergence anomaly serves as the primary indicator for extended-range monitoring and forecasting of MTC events.It accounts for the highest proportion of TCs,with its anomaly values most frequently exceeding the critical thresholds at TC genesis locations.Meanwhile,the water vapor flux divergence anomaly also provides the earliest anomalous signal and demonstrates the most sustained and stable indicative effect.展开更多
A generalized wave-activity density, which is defined as an absolute value of production of three-dimensional vorticity vector perturbation and gradient of general potential temperature perturbation, is introduced and...A generalized wave-activity density, which is defined as an absolute value of production of three-dimensional vorticity vector perturbation and gradient of general potential temperature perturbation, is introduced and its wave-activity law is derived in Cartesian coordinates. Constructed in an agoestrophic and nonhydrostatie dynamical framework, the generalized wave-activity law may be applicable to diagnose mesoscale weather systems leading to heavy rainfall. The generalized wave-activity density and wave-activity flux divergence were calculated with the objective analysis data to investigate the character of wave activity over heavy-rainfall regions. The primary dynamical processes responsible for disturbance associated with heavy rainfall were also analyzed. It was shown that the generalized wave-activity density was closely correlated to the observed 6-h accumulative rainfall. This indicated that the wave activity or disturbance was evident over the frontal and landfall-typhoon heavy-rainfall regions in middle and lower troposphere. For the landfall-typhoon rainband, the portion of generalized wave-activity flux divergence, denoting the interaction between the basic-state cyclonic circulation of landfall typhoon and mesoscale waves, was the primary dynamic process responsible for the evolution of generalized wave-activity density.展开更多
Anomalous characteristics of the atmospheric water cycle structure are highly significant to the mechanisms of seasonal-scale meteorological droughts.They also play an important role in the identification of indicativ...Anomalous characteristics of the atmospheric water cycle structure are highly significant to the mechanisms of seasonal-scale meteorological droughts.They also play an important role in the identification of indicative predictors of droughts.To better understand the causes of seasonal meteorological droughts in the middle and lower reaches of the Yangtze River(MLRYR),characteristics of the atmospheric water cycle structure at different drought stages were determined using standardized anomalies.The results showed that the total column water vapor(TCWV)was anomalously low during drought occurrence periods.In contrast,there were no anomalous signals at the drought persistence and recovery stages in the MLRYR.Moreover,there was no significant temporal correlation between the TCWV anomaly and seasonal-scale drought index(the 3-month standardized precipitation index(SPI_(3))).During drought events,water vapor that mainly originated from the Bay of Bengal was transported southwest of the MLRYR.Meanwhile,the anomalous signal of water vapor transport was negative at the drought appearance stage.At the drought persistence stage,the negative anomalous signal was the most significant.Water vapor flux divergence in the MLRYR showed significant positive anomalous signals during drought events,and the signal intensity shifted from an increasing to a decreasing trend at different drought stages.In addition,a significant positive correlation existed between the anomaly of water vapor flux divergence and regional SPI_(3).Overall,water vapor flux divergence is more predictive of droughts in the MLRYR.展开更多
National Centers for Environment Prediction (NCEP) reanalysis data, automatic observation data, FY-2E satellite data and Doppler radar data are used to analyze a short-time local heavy rain in Yulin city, Shaanxi, Chi...National Centers for Environment Prediction (NCEP) reanalysis data, automatic observation data, FY-2E satellite data and Doppler radar data are used to analyze a short-time local heavy rain in Yulin city, Shaanxi, China on August 7, 2018. The result shows that the strong convective weather occurred in peripheral subtropical high over west pacific, being caused by short wave disturbance, and surface convergence lines with positive pressure variation are corresponding to areas of short-time heavy precipitation. The degree of temperature change in cold pool caused by thunderstorm may decide the intensity of a short-time rainfall, and local topography plays an important role in extreme precipitation. Local water vapour accumulation and water vapour flux convergence in the middle and lower layers support adequate moisture condition in the process. Moving direction and development direction of mesocale convective cloud are in a line to develop the train effect, leading to local short-time heavy rain in Yulin city, Shaanxi, China.展开更多
Based on observational and reanalysis data,the relationships between the eastern Pacific(EP)and central Pacific(CP)types of El Niño−Southern Oscillation(ENSO)during the developing summer and the South Asian summe...Based on observational and reanalysis data,the relationships between the eastern Pacific(EP)and central Pacific(CP)types of El Niño−Southern Oscillation(ENSO)during the developing summer and the South Asian summer monsoon(SASM)are examined.The roles of these two types of ENSO on the SASM experienced notable multidecadal modulation in the late 1970s.While the inverse relationship between the EP type of ENSO and the SASM has weakened dramatically,the CP type of ENSO plays a far more prominent role in producing anomalous Indian monsoon rainfall after the late 1970s.The drought-producing El Niño warming of both the EP and CP types can excite anomalous rising motion of the Walker circulation concentrated in the equatorial central Pacific around 160°W to the date line.Accordingly,compensatory subsidence anomalies are evident from the Maritime Continent to the Indian subcontinent,leading to suppressed convection and decreased precipitation over these regions.Moreover,anomalously less moisture flux into South Asia associated with developing EP El Niño and significant northwesterly anomalies dominating over southern India accompanied by developing CP El Niño,may also have been responsible for the Indian monsoon droughts during the pre-1979 and post-1979 sub-periods,respectively.El Niño events with the same“flavor”may not necessarily produce consistent Indian monsoon rainfall anomalies,while similar Indian monsoon droughts may be induced by different types of El Niño,implying high sensitivity of monsoonal precipitation to the detailed configuration of ENSO forcing imposed on the tropical Pacific.展开更多
[Objective] The research aimed to analyze a rainstorm process in Chongqing. [Methed] Based on precipitation product datasets and NCEP reanalysis data, synoptic situation and diagnostic analysis of a heavy rain process...[Objective] The research aimed to analyze a rainstorm process in Chongqing. [Methed] Based on precipitation product datasets and NCEP reanalysis data, synoptic situation and diagnostic analysis of a heavy rain process during 11 -12 May, 2012 in Chongqing were made, and the diagnostic analysis included dynamic and vapor conditions, instability index, vapor helicity and vapor divergence flux. [ Result] The east-south moving short wave trough and east-north moving southwest vortex were the main synoptic systems causing the heavy rain; the positive vorticity advection before trough and after ridge helped the ascending motion from surface; the southwest stream at 700 hPa provided vapor and energy, promoting and maintaining the intense development of convection; the higher vapor helicity and lower vapor divergence flux were well corresponding with higher precipitation area, and had well temporal correlation, which was significant for forecast of precipitation area and its development; the ascended warm wet stream on the lower air came across the cold air on the upper air, triggering the heavy rain; the Kindex and A index were significant for the heavy rain forecasting. [ Conclusion] The research could provide some references for research and forecast of future rainstorm process in Sichuan and Chongqing.展开更多
The notion of the inner product of vectors is extended to tensors of different orders, which may replace the vector product usually. The essences of the differential and the codiffcrential forms are pointed out： they...The notion of the inner product of vectors is extended to tensors of different orders, which may replace the vector product usually. The essences of the differential and the codiffcrential forms are pointed out： they represent the tangent surface and the normal surface fluxes of a tensor, reslpetivcly. The definitions of the divergence and the curl of a 2D surface flux of a tensor arc obtained. Maxwell＇s equations, namely, the constraction law of field, which were usually established based on two conservation laws of electric charge and imaginary magnetic charge, are derived by the author only by using one conservation law （ mass or fluid flux quantity and so on） and the feature of central field （or its composition）. By the feature of central field （or its composition）, the curl of 2D flux is zero. Both universality of gauge field and the difficulty of magnetic monopole theory （ a magnetic monopole has no effect on electric current just like a couple hasing no effect on the sum of forces） axe presented： magnetic monopole has no the feature of magnet. Finally it is pointed out that the base of relation of mass and energy is already involved in Maxwell＇s equations.展开更多
基金Guidance Project for Industrial Technology Develop-ment and Application Plan of Fujian Province(2024Y0075)Natural Science Foundation of Fujian Province(2022J01441,2024J011139,2022J011077)+3 种基金Innovation and development Project of the China Meteorological Administration(CXFZ2024J024)National Natural Science Foundation of China(42205048)Science Foundation of the Fujian Meteorological Bureau(2023Q04)Meteorological Services Research Project of the China Meteorological Administration(JCZX202409)。
文摘Based on the analysis of multiple tropical cyclone(MTC)events in the South China Sea and Northwest Pacific Ocean during 1979-2019,this study classfies periods of the tropical cyclone(TC)events into active,normal,and inactive phases.To analyze the spatial distribution of associated anomalous variables and indices,an anomaly-based variable model is employed.Anomalies of 850 hPa vorticity,850 hPa water vapor flux divergence,and 400 hPa vertical velocity are selected as optimal predictors with physical significance.From these predictors,a physical model for the original MTC development is established.The results show that during the period of MTC development,a stable warm-core anomaly persists at 300 hPa,with a“warm tongue”extending downward as far as 700 hPa.The upper-level high-pressure anomaly center does not completely overlap with the low-pressure anomaly center at lower levels until TC genesis approaches.In addition,the 500-1000 hPa water vapor flux initially exhibits a negative anomaly,which facilitates water vapor to accumulate.A negative vertical velocity anomaly then develops,promoting the upward motion that gradually stabilizes and expands to a wider range.Ultimately,these processes lead to the formation of a positive vorticity anomaly,signifying a TC’s formation.Among the three key factors,the water vapor flux divergence anomaly serves as the primary indicator for extended-range monitoring and forecasting of MTC events.It accounts for the highest proportion of TCs,with its anomaly values most frequently exceeding the critical thresholds at TC genesis locations.Meanwhile,the water vapor flux divergence anomaly also provides the earliest anomalous signal and demonstrates the most sustained and stable indicative effect.
基金National Basic Research Program of China (2009CB421505)National Natural Sciences Foundations of China (40875032)
文摘A generalized wave-activity density, which is defined as an absolute value of production of three-dimensional vorticity vector perturbation and gradient of general potential temperature perturbation, is introduced and its wave-activity law is derived in Cartesian coordinates. Constructed in an agoestrophic and nonhydrostatie dynamical framework, the generalized wave-activity law may be applicable to diagnose mesoscale weather systems leading to heavy rainfall. The generalized wave-activity density and wave-activity flux divergence were calculated with the objective analysis data to investigate the character of wave activity over heavy-rainfall regions. The primary dynamical processes responsible for disturbance associated with heavy rainfall were also analyzed. It was shown that the generalized wave-activity density was closely correlated to the observed 6-h accumulative rainfall. This indicated that the wave activity or disturbance was evident over the frontal and landfall-typhoon heavy-rainfall regions in middle and lower troposphere. For the landfall-typhoon rainband, the portion of generalized wave-activity flux divergence, denoting the interaction between the basic-state cyclonic circulation of landfall typhoon and mesoscale waves, was the primary dynamic process responsible for the evolution of generalized wave-activity density.
基金supported by the National Key Research and Development Program of China(Grants No.2019YFC0409000,2017YFC1502403,and 2018YFC0407701)the Fundamental Research Funds for the Central Universities(Grant No.B200204045).
文摘Anomalous characteristics of the atmospheric water cycle structure are highly significant to the mechanisms of seasonal-scale meteorological droughts.They also play an important role in the identification of indicative predictors of droughts.To better understand the causes of seasonal meteorological droughts in the middle and lower reaches of the Yangtze River(MLRYR),characteristics of the atmospheric water cycle structure at different drought stages were determined using standardized anomalies.The results showed that the total column water vapor(TCWV)was anomalously low during drought occurrence periods.In contrast,there were no anomalous signals at the drought persistence and recovery stages in the MLRYR.Moreover,there was no significant temporal correlation between the TCWV anomaly and seasonal-scale drought index(the 3-month standardized precipitation index(SPI_(3))).During drought events,water vapor that mainly originated from the Bay of Bengal was transported southwest of the MLRYR.Meanwhile,the anomalous signal of water vapor transport was negative at the drought appearance stage.At the drought persistence stage,the negative anomalous signal was the most significant.Water vapor flux divergence in the MLRYR showed significant positive anomalous signals during drought events,and the signal intensity shifted from an increasing to a decreasing trend at different drought stages.In addition,a significant positive correlation existed between the anomaly of water vapor flux divergence and regional SPI_(3).Overall,water vapor flux divergence is more predictive of droughts in the MLRYR.
文摘National Centers for Environment Prediction (NCEP) reanalysis data, automatic observation data, FY-2E satellite data and Doppler radar data are used to analyze a short-time local heavy rain in Yulin city, Shaanxi, China on August 7, 2018. The result shows that the strong convective weather occurred in peripheral subtropical high over west pacific, being caused by short wave disturbance, and surface convergence lines with positive pressure variation are corresponding to areas of short-time heavy precipitation. The degree of temperature change in cold pool caused by thunderstorm may decide the intensity of a short-time rainfall, and local topography plays an important role in extreme precipitation. Local water vapour accumulation and water vapour flux convergence in the middle and lower layers support adequate moisture condition in the process. Moving direction and development direction of mesocale convective cloud are in a line to develop the train effect, leading to local short-time heavy rain in Yulin city, Shaanxi, China.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.41405058 and 41861144015)the National Key R&D Program of China(2017YFA0603201).
文摘Based on observational and reanalysis data,the relationships between the eastern Pacific(EP)and central Pacific(CP)types of El Niño−Southern Oscillation(ENSO)during the developing summer and the South Asian summer monsoon(SASM)are examined.The roles of these two types of ENSO on the SASM experienced notable multidecadal modulation in the late 1970s.While the inverse relationship between the EP type of ENSO and the SASM has weakened dramatically,the CP type of ENSO plays a far more prominent role in producing anomalous Indian monsoon rainfall after the late 1970s.The drought-producing El Niño warming of both the EP and CP types can excite anomalous rising motion of the Walker circulation concentrated in the equatorial central Pacific around 160°W to the date line.Accordingly,compensatory subsidence anomalies are evident from the Maritime Continent to the Indian subcontinent,leading to suppressed convection and decreased precipitation over these regions.Moreover,anomalously less moisture flux into South Asia associated with developing EP El Niño and significant northwesterly anomalies dominating over southern India accompanied by developing CP El Niño,may also have been responsible for the Indian monsoon droughts during the pre-1979 and post-1979 sub-periods,respectively.El Niño events with the same“flavor”may not necessarily produce consistent Indian monsoon rainfall anomalies,while similar Indian monsoon droughts may be induced by different types of El Niño,implying high sensitivity of monsoonal precipitation to the detailed configuration of ENSO forcing imposed on the tropical Pacific.
基金Supported by National Natural Science Foundation of China(41175046,41205009)
文摘[Objective] The research aimed to analyze a rainstorm process in Chongqing. [Methed] Based on precipitation product datasets and NCEP reanalysis data, synoptic situation and diagnostic analysis of a heavy rain process during 11 -12 May, 2012 in Chongqing were made, and the diagnostic analysis included dynamic and vapor conditions, instability index, vapor helicity and vapor divergence flux. [ Result] The east-south moving short wave trough and east-north moving southwest vortex were the main synoptic systems causing the heavy rain; the positive vorticity advection before trough and after ridge helped the ascending motion from surface; the southwest stream at 700 hPa provided vapor and energy, promoting and maintaining the intense development of convection; the higher vapor helicity and lower vapor divergence flux were well corresponding with higher precipitation area, and had well temporal correlation, which was significant for forecast of precipitation area and its development; the ascended warm wet stream on the lower air came across the cold air on the upper air, triggering the heavy rain; the Kindex and A index were significant for the heavy rain forecasting. [ Conclusion] The research could provide some references for research and forecast of future rainstorm process in Sichuan and Chongqing.
文摘The notion of the inner product of vectors is extended to tensors of different orders, which may replace the vector product usually. The essences of the differential and the codiffcrential forms are pointed out： they represent the tangent surface and the normal surface fluxes of a tensor, reslpetivcly. The definitions of the divergence and the curl of a 2D surface flux of a tensor arc obtained. Maxwell＇s equations, namely, the constraction law of field, which were usually established based on two conservation laws of electric charge and imaginary magnetic charge, are derived by the author only by using one conservation law （ mass or fluid flux quantity and so on） and the feature of central field （or its composition）. By the feature of central field （or its composition）, the curl of 2D flux is zero. Both universality of gauge field and the difficulty of magnetic monopole theory （ a magnetic monopole has no effect on electric current just like a couple hasing no effect on the sum of forces） axe presented： magnetic monopole has no the feature of magnet. Finally it is pointed out that the base of relation of mass and energy is already involved in Maxwell＇s equations.
