Short-duration heavy rainfall(SHR),as delineated by the National Meteorological Center of the China Me-teorological Administration,is characterized by hourly rainfall amounts no less than 20.0 mm.SHR is one of the mos...Short-duration heavy rainfall(SHR),as delineated by the National Meteorological Center of the China Me-teorological Administration,is characterized by hourly rainfall amounts no less than 20.0 mm.SHR is one of the most common convective weather phenomena that can cause severe damage.Short-range forecasting of SHR is an important part of operational severe weather prediction.In the present study,an improved objective SHR forecasting scheme was developed by adopting the ingredients-based methodology and using the fuzzy logic approach.The 1.0°×1.0°National Centers for Environmental Prediction(NCEP)final analysis data and the ordinary rainfall(0.1-19.9 mm h-1)and SHR observational data from 411 stations were used in the improved scheme.The best lifted index,the total precipitable water,the 925 hPa specific humidity(Q 925),and the 925 hPa divergence(DIV 925)were selected as predictors based on objective analysis.Continuously distributed membership functions of predictors were obtained based on relative frequency analysis.The weights of predictors were also objectively determined.Experiments with a typhoon SHR case and a spring SHR case show that the main possible areas could be captured by the improved scheme.Verification of SHR forecasts within 96 hours with NCEP global forecasts 1.0°×1.0°data initiated at 08:00 Beijing Time during the warm seasons in 2015 show the results were improved from both deterministic and probabilistic perspectives.This study provides an objectively feasible choice for short-range guidance forecasts of SHR.The scheme can be applied to other convective phenomena.展开更多
Composite radar reflectivity data during April-September 2011-2015 are used to investigate and classify storms in south China(18-27°N;105-120°E). The storms appear most frequently in May. They are either lin...Composite radar reflectivity data during April-September 2011-2015 are used to investigate and classify storms in south China(18-27°N;105-120°E). The storms appear most frequently in May. They are either linear;cellular or nonlinear systems, taking up 29.45%, 24.51% and 46.04%, respectively, in terms of morphology. Linear systems are subdivided into six morphologies: trailing stratiform precipitation(TS), bow echoes(BE), leading stratiform precipitation(LS), embedded line(EL), no stratiform precipitation(NS) and parallel stratiform precipitation(PS). The TS and NS modes have the highest frequencies but there are only small samples of LS(0.61%) and PS(0.79%) modes.Severe convective wind(≥17m s-1at surface level) accounts for the highest percentage(35%) of severe convective weather events produced by cellular systems including individual cells(IC) and clusters of cells(CC). Short-duration heavy rainfall(≥50 mm h-1) and severe convective wind are the most common severe weather associated with TS and BE modes. Comparison of environmental physical parameters shows that cellular convection systems tend to occur in the environment with favorable thermal condition, substantial unstable energy and low precipitable water from the surface to300 hPa(PWAT). However, the environmental conditions favoring the initiation of linear systems feature strong vertical wind shear, high PWAT, and intense convective inhibition. The environmental parameters favoring the initiation of nonlinear systems are between those of the other two types of morphology.展开更多
Based on the hourly precipitation data at 176 observational stations over south China and the hourly ERA5reanalysis data during the 40-yr period of 1981-2020, we analyzed the universal characteristics of moisture tran...Based on the hourly precipitation data at 176 observational stations over south China and the hourly ERA5reanalysis data during the 40-yr period of 1981-2020, we analyzed the universal characteristics of moisture transport and their associated background circulations for four types of regional extreme precipitation events(REPEs) over south China. Main findings are shown as follow.(i) The wind that transported moisture for the REPEs over south China featured a notable diurnal variation, which was consistent with the variations of the precipitation.(ii) Four types of REPEs could be determined, among which the southwest type(SWT) and the southeast type(SET) accounted for ~92%and ~5.7%, respectively, ranking the first and second, respectively.(iii) Trajectory analyses showed that the air particles of the SWT-REPEs had the largest specific humidity and experienced the most intense ascending motion, and therefore their precipitation was the strongest among the four types.(iv) South China was dominated by notable moisture flux convergence for the four types of REPEs, but their moisture transport was controlled by different flow paths.(v)Composite analyses indicated that the background circulation of the four types of REPEs showed different features,particularly for the intensity, location and coverage of a western Pacific subtropical high. For the SWT-REPEs, their moisture transport was mainly driven by a lower-tropospheric strong southwesterly wind band in the low-latitude regions. Air particles for this type of REPEs mainly passed over the Indochina Peninsula and South China Sea. For the SET-REPEs, their moisture transport was mainly steered by a strong low-tropospheric southeasterly wind northeast of a transversal trough. Air particles mainly passed over the South China Sea for this type of REPEs.展开更多
基金Key R&D Program of Xizang Autonomous Region(XZ202101ZY0004G)National Natural Science Foundation of China(U2142202)+1 种基金National Key R&D Program of China(2022YFC3004104)Key Innovation Team of China Meteor-ological Administration(CMA2022ZD07)。
文摘Short-duration heavy rainfall(SHR),as delineated by the National Meteorological Center of the China Me-teorological Administration,is characterized by hourly rainfall amounts no less than 20.0 mm.SHR is one of the most common convective weather phenomena that can cause severe damage.Short-range forecasting of SHR is an important part of operational severe weather prediction.In the present study,an improved objective SHR forecasting scheme was developed by adopting the ingredients-based methodology and using the fuzzy logic approach.The 1.0°×1.0°National Centers for Environmental Prediction(NCEP)final analysis data and the ordinary rainfall(0.1-19.9 mm h-1)and SHR observational data from 411 stations were used in the improved scheme.The best lifted index,the total precipitable water,the 925 hPa specific humidity(Q 925),and the 925 hPa divergence(DIV 925)were selected as predictors based on objective analysis.Continuously distributed membership functions of predictors were obtained based on relative frequency analysis.The weights of predictors were also objectively determined.Experiments with a typhoon SHR case and a spring SHR case show that the main possible areas could be captured by the improved scheme.Verification of SHR forecasts within 96 hours with NCEP global forecasts 1.0°×1.0°data initiated at 08:00 Beijing Time during the warm seasons in 2015 show the results were improved from both deterministic and probabilistic perspectives.This study provides an objectively feasible choice for short-range guidance forecasts of SHR.The scheme can be applied to other convective phenomena.
基金National Key Research and Development Program of China(2019YFC1510400)National Natural Science Foundation of China(41975056,41675045)。
文摘Composite radar reflectivity data during April-September 2011-2015 are used to investigate and classify storms in south China(18-27°N;105-120°E). The storms appear most frequently in May. They are either linear;cellular or nonlinear systems, taking up 29.45%, 24.51% and 46.04%, respectively, in terms of morphology. Linear systems are subdivided into six morphologies: trailing stratiform precipitation(TS), bow echoes(BE), leading stratiform precipitation(LS), embedded line(EL), no stratiform precipitation(NS) and parallel stratiform precipitation(PS). The TS and NS modes have the highest frequencies but there are only small samples of LS(0.61%) and PS(0.79%) modes.Severe convective wind(≥17m s-1at surface level) accounts for the highest percentage(35%) of severe convective weather events produced by cellular systems including individual cells(IC) and clusters of cells(CC). Short-duration heavy rainfall(≥50 mm h-1) and severe convective wind are the most common severe weather associated with TS and BE modes. Comparison of environmental physical parameters shows that cellular convection systems tend to occur in the environment with favorable thermal condition, substantial unstable energy and low precipitable water from the surface to300 hPa(PWAT). However, the environmental conditions favoring the initiation of linear systems feature strong vertical wind shear, high PWAT, and intense convective inhibition. The environmental parameters favoring the initiation of nonlinear systems are between those of the other two types of morphology.
基金National Key Research and Development Program of China(2019YFC1510400)National Natural Science Foundation of China(42075002)。
文摘Based on the hourly precipitation data at 176 observational stations over south China and the hourly ERA5reanalysis data during the 40-yr period of 1981-2020, we analyzed the universal characteristics of moisture transport and their associated background circulations for four types of regional extreme precipitation events(REPEs) over south China. Main findings are shown as follow.(i) The wind that transported moisture for the REPEs over south China featured a notable diurnal variation, which was consistent with the variations of the precipitation.(ii) Four types of REPEs could be determined, among which the southwest type(SWT) and the southeast type(SET) accounted for ~92%and ~5.7%, respectively, ranking the first and second, respectively.(iii) Trajectory analyses showed that the air particles of the SWT-REPEs had the largest specific humidity and experienced the most intense ascending motion, and therefore their precipitation was the strongest among the four types.(iv) South China was dominated by notable moisture flux convergence for the four types of REPEs, but their moisture transport was controlled by different flow paths.(v)Composite analyses indicated that the background circulation of the four types of REPEs showed different features,particularly for the intensity, location and coverage of a western Pacific subtropical high. For the SWT-REPEs, their moisture transport was mainly driven by a lower-tropospheric strong southwesterly wind band in the low-latitude regions. Air particles for this type of REPEs mainly passed over the Indochina Peninsula and South China Sea. For the SET-REPEs, their moisture transport was mainly steered by a strong low-tropospheric southeasterly wind northeast of a transversal trough. Air particles mainly passed over the South China Sea for this type of REPEs.
