Significant anomalous tracks were observed when the severe tropical storm Goni （0907） and typhoon Morakot （0908） in September 2009 were evaluated in short distances. The relationship between the two is regarded as...Significant anomalous tracks were observed when the severe tropical storm Goni （0907） and typhoon Morakot （0908） in September 2009 were evaluated in short distances. The relationship between the two is regarded as a case of binary interaction. Based on an MM5 model （fifth=generation mesoscale model of Pennsylvania State University-National Center for Atmospheric Research）, in this study a series of sensitivity experiments were designed to determine the binary interaction between them. The sensitivity of the storm characteristics to the binary interaction was demonstrated through modeling experiments with different TC intensities and sizes based on the bogus vortices initialization. Furthermore, the contributions of large-scale environmental flow and the effects of interaction between the motions of the cyclones were distinguished by numerical experiments using only one of the TC vortices. Results from these experiments show that Morakot （0908） had a greater impact on the motion of Goni （0907）, whereas Goni （0907） had a relatively limited impact on Morakot （0908）. At the upper level, the northeasterly jet flow in the third quadrant of Morakot （0908） enhanced the upper-level divergence of Goni （0907） and had an important role in maintaining and increasing Goni＇s （0907） intensity. And at the lower level, Morakot （0908）, with strong convergence and ascending airflow, made a stable transport channel of southwesterly warm and wet flow, thus supporting the lower-level water vapor convergence of Goni （0907）. Goni （0907）, which was located upriver of the southwesterly flow, intercepted part of the water vapor transportation in the southwesterly flow, causing the water vapor convergence to strengthen while the water vapor convergence of Morakot （0908） weakened.展开更多
Tropical cyclones(TCs) Lionrock,Kompasu,and Namtheun were formed successively within 40 hours in 2010.Over the next several days afterwards,these TCs exhibited unusual movements which made operational prediction diffi...Tropical cyclones(TCs) Lionrock,Kompasu,and Namtheun were formed successively within 40 hours in 2010.Over the next several days afterwards,these TCs exhibited unusual movements which made operational prediction difficult.Verifications are performed on the forecasts of the tracks of these TCs with six operational models,including three global and three regional models.Results showed that the trends of TC tracks could be reproduced by these models,whereas trajectory turning points and landfall locations were not simulated effectively.The special track of Lionrock should be associated with its direct interaction with Namtheun,according to a conceptual model of binary TC interaction.By contrast,the relation between Kompasu and Namtheun satisfied the criteria for a semi-direct interaction.Numerical experiments based on the Global and Regional Assimilation and Prediction System-Tropical Cyclone forecast Model(GRAPES-TCM) further confirmed the effect of Namtheun on the unusual tracks of Lionrock and Kompasu.Finally,the physical mechanism of binary TC interaction was preliminarily proposed.展开更多
Given time-independent monthly mean sea temperature,numerical simulation was done of the path of the tropical cyclone Forrest and its related physical quantity field in terms of the improved version of the σ-coordina...Given time-independent monthly mean sea temperature,numerical simulation was done of the path of the tropical cyclone Forrest and its related physical quantity field in terms of the improved version of the σ-coordinate 10-level primitive equation model for tropical cyclones developed by the Guangzhou Institute of Marine Meteorology.Results suggest the similarity between the simulated and observed physical quantity fields except that the simulated path was to the right of the observed,with the deviation increasing with time. Sea and tropical cyclone,in effect,interact mutually.In an attempt to compare the results from coupling and uncoupling experiments,an oceanic mixed layer model was formulated based on experiments with sea response to cy- clone and integrated in synchronous coupling with the aforementioned version of tropical cyclones,the computational domain covering the western North Pacific with the coastal configuration involved.The coupling experiment shows that the negative feedback of the interaction between sea and mature cyclone leads to weaker sea response as compared to the uncoupling case.Except for the location of the divergence core of oceanic current,the mixed layer depth and inhomogeneous distribution of sea surface temperature (SST) caused by the cyclone-core position and intensity,the val- ues of the maximum oceanic current,departure of the mixed layer depth and SST drop were smaller in the coupling than in the uncoupling case,and so was the maximum wind near the cyclone core.The path from the coupling run is to the left of the course in the uncoupling experiment but closer to the observed one though remaining somewhat leftward. Even on a scale of less than 3 days,the effects of sea and sea-cyclone interaction on the cyclone were by no means negli- gible.展开更多
The barotropic primitive equations model is used in a numerical study of a tropical cyclone crossing the Subtropical high. It is revealed that apart from its own characteristics, sensitive factors having immediate eff...The barotropic primitive equations model is used in a numerical study of a tropical cyclone crossing the Subtropical high. It is revealed that apart from its own characteristics, sensitive factors having immediate effects on the motion of the tropical cyclone also include its radial distance from the center of the subtropical high, the variation in latitudinal location and intensity. A complex mechanism for nonlinear interactions among the tropical,subtropical high and β effect is also shown in the experiment, and expected to serve for the diagnosis and prediction of abnormal motion.展开更多
The surface flux exchange associated with the exchange coefficients and upper ocean conditions is essential to the development of tropical cyclones(TCs).Using the Weather Research and Forecasting(WRF)model,the present...The surface flux exchange associated with the exchange coefficients and upper ocean conditions is essential to the development of tropical cyclones(TCs).Using the Weather Research and Forecasting(WRF)model,the present study has investigated the impact of exchange coefficients and ocean coupling during Super Typhoon Saomai(2006).Firstly,two experiments with different formula of roughness are conducted.The experiment with the Donelan formula for drag coefficient(C_(d))and ramped formula for enthalpy coefficient(C_(k))can simulate stronger intensity compared to other experiments due to the increased surface wind and enthalpy fluxes.That is because the new formulas allows for a smaller C_(d)and larger C_(k)in the high wind regime than the former formulas did.Moreover,two coupled simulations between WRF and a one-dimensional ocean model are conducted to examine the feedback of sea surface cooling to the TC.In the experiments with a horizontal uniform mixed layer depth of 70 m,the sea surface cooling is too weak to change the evolution of TC.While in the experiment with an input mixed layer calculated using the Hybrid Coordinate Ocean Model(HYCOM)data,the significant sea surface cooling induces obvious impact on TC intensity and structure.Under the negative feedback of sea surface cooling,the sensible and latent heat fluxes decreases,especially in the right part of Saomai(2006).The negative feedback with coupled ocean model plays a vital role in simulating the intensity and structure of TC.展开更多
Recent studies found that in the context of global warming, the observed tropical cyclones （TCs） exhibit signific-ant poleward migration trend in terms of the mean latitude where TCs reach their lifetime-maximum int...Recent studies found that in the context of global warming, the observed tropical cyclones （TCs） exhibit signific-ant poleward migration trend in terms of the mean latitude where TCs reach their lifetime-maximum intensity in the western North Pacific （WNP）. This poleward migration of TC tracks can be attributed to not only anthropogenic for-cing （e.g., continuous increase of sea surface temperature （SST））, but also impacts of other factors （e.g., natural vari- ability）. In the present study, to eliminate the impacts of other factors and thus focus on the impact of unvaried SST on climatological WNP TC tracks, the mesoscale Weather Research and Forecasting （WRF） model is used to con- duct a suite of idealized sensitivity experiments with increased SST. Comparisons among the results of these experi- ments show the possible changes in climatological TC track, TC track density, and types of TC track in the context of SST increase. The results demonstrate that under the warmer SST conditions, the climatological mean TC track sys-tematically shifts poleward significantly in the WNP, which is consistent with the previous studies. Meanwhile, the ocean warming also leads to the decreased （increased） destructive potential of TCs in low （middle） latitudes, and thus northward migration of the region where TCs have the largest impact. Further results imply the possibility that under the ocean warming, the percentage of TCs with westward/northwestward tracks decreases/increases distinctly.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 41005029)the National Public Benefit (Meteorology) Research Foundation of China (Grant No.GYHY201106004)
文摘Significant anomalous tracks were observed when the severe tropical storm Goni （0907） and typhoon Morakot （0908） in September 2009 were evaluated in short distances. The relationship between the two is regarded as a case of binary interaction. Based on an MM5 model （fifth=generation mesoscale model of Pennsylvania State University-National Center for Atmospheric Research）, in this study a series of sensitivity experiments were designed to determine the binary interaction between them. The sensitivity of the storm characteristics to the binary interaction was demonstrated through modeling experiments with different TC intensities and sizes based on the bogus vortices initialization. Furthermore, the contributions of large-scale environmental flow and the effects of interaction between the motions of the cyclones were distinguished by numerical experiments using only one of the TC vortices. Results from these experiments show that Morakot （0908） had a greater impact on the motion of Goni （0907）, whereas Goni （0907） had a relatively limited impact on Morakot （0908）. At the upper level, the northeasterly jet flow in the third quadrant of Morakot （0908） enhanced the upper-level divergence of Goni （0907） and had an important role in maintaining and increasing Goni＇s （0907） intensity. And at the lower level, Morakot （0908）, with strong convergence and ascending airflow, made a stable transport channel of southwesterly warm and wet flow, thus supporting the lower-level water vapor convergence of Goni （0907）. Goni （0907）, which was located upriver of the southwesterly flow, intercepted part of the water vapor transportation in the southwesterly flow, causing the water vapor convergence to strengthen while the water vapor convergence of Morakot （0908） weakened.
基金"973"Project(2009CB421500,2013CB430305)National Natural Science Foundation of China(40921160381,40705024,40875039)+1 种基金Special Scientific Research Fund of Meteorological Public Welfare of China(GYHY201006007,GYHY201006008,GYHY201006016)Shanghai Typhoon Research Foundation(2010ST09)
文摘Tropical cyclones(TCs) Lionrock,Kompasu,and Namtheun were formed successively within 40 hours in 2010.Over the next several days afterwards,these TCs exhibited unusual movements which made operational prediction difficult.Verifications are performed on the forecasts of the tracks of these TCs with six operational models,including three global and three regional models.Results showed that the trends of TC tracks could be reproduced by these models,whereas trajectory turning points and landfall locations were not simulated effectively.The special track of Lionrock should be associated with its direct interaction with Namtheun,according to a conceptual model of binary TC interaction.By contrast,the relation between Kompasu and Namtheun satisfied the criteria for a semi-direct interaction.Numerical experiments based on the Global and Regional Assimilation and Prediction System-Tropical Cyclone forecast Model(GRAPES-TCM) further confirmed the effect of Namtheun on the unusual tracks of Lionrock and Kompasu.Finally,the physical mechanism of binary TC interaction was preliminarily proposed.
基金The project is supported by the National Key Program of Science and Technology of China during 1991-1995 under Grant No. 85-906-07.
文摘Given time-independent monthly mean sea temperature,numerical simulation was done of the path of the tropical cyclone Forrest and its related physical quantity field in terms of the improved version of the σ-coordinate 10-level primitive equation model for tropical cyclones developed by the Guangzhou Institute of Marine Meteorology.Results suggest the similarity between the simulated and observed physical quantity fields except that the simulated path was to the right of the observed,with the deviation increasing with time. Sea and tropical cyclone,in effect,interact mutually.In an attempt to compare the results from coupling and uncoupling experiments,an oceanic mixed layer model was formulated based on experiments with sea response to cy- clone and integrated in synchronous coupling with the aforementioned version of tropical cyclones,the computational domain covering the western North Pacific with the coastal configuration involved.The coupling experiment shows that the negative feedback of the interaction between sea and mature cyclone leads to weaker sea response as compared to the uncoupling case.Except for the location of the divergence core of oceanic current,the mixed layer depth and inhomogeneous distribution of sea surface temperature (SST) caused by the cyclone-core position and intensity,the val- ues of the maximum oceanic current,departure of the mixed layer depth and SST drop were smaller in the coupling than in the uncoupling case,and so was the maximum wind near the cyclone core.The path from the coupling run is to the left of the course in the uncoupling experiment but closer to the observed one though remaining somewhat leftward. Even on a scale of less than 3 days,the effects of sea and sea-cyclone interaction on the cyclone were by no means negli- gible.
文摘The barotropic primitive equations model is used in a numerical study of a tropical cyclone crossing the Subtropical high. It is revealed that apart from its own characteristics, sensitive factors having immediate effects on the motion of the tropical cyclone also include its radial distance from the center of the subtropical high, the variation in latitudinal location and intensity. A complex mechanism for nonlinear interactions among the tropical,subtropical high and β effect is also shown in the experiment, and expected to serve for the diagnosis and prediction of abnormal motion.
基金National Key R&D Program of China(2020YFE0201900)Fundamental Research Funds for the Central Universities(No.020714380171)+4 种基金Open Grants of the State Key Laboratory of Severe Weather(2021LASW-A01)Open Fund of the State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography,MNR(QNHX1809)Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(311021001)Zhejiang Provincial Key Research and Development Project(2021C03186)Oceanic Interdisciplinary Program of Shanghai Jiao Tong University(SL2020MS032)。
文摘The surface flux exchange associated with the exchange coefficients and upper ocean conditions is essential to the development of tropical cyclones(TCs).Using the Weather Research and Forecasting(WRF)model,the present study has investigated the impact of exchange coefficients and ocean coupling during Super Typhoon Saomai(2006).Firstly,two experiments with different formula of roughness are conducted.The experiment with the Donelan formula for drag coefficient(C_(d))and ramped formula for enthalpy coefficient(C_(k))can simulate stronger intensity compared to other experiments due to the increased surface wind and enthalpy fluxes.That is because the new formulas allows for a smaller C_(d)and larger C_(k)in the high wind regime than the former formulas did.Moreover,two coupled simulations between WRF and a one-dimensional ocean model are conducted to examine the feedback of sea surface cooling to the TC.In the experiments with a horizontal uniform mixed layer depth of 70 m,the sea surface cooling is too weak to change the evolution of TC.While in the experiment with an input mixed layer calculated using the Hybrid Coordinate Ocean Model(HYCOM)data,the significant sea surface cooling induces obvious impact on TC intensity and structure.Under the negative feedback of sea surface cooling,the sensible and latent heat fluxes decreases,especially in the right part of Saomai(2006).The negative feedback with coupled ocean model plays a vital role in simulating the intensity and structure of TC.
基金Supported by the National Natural Science Foundation of China(41430426 and 41605072)Natural Science Foundation of Jiangsu(BK20160768)
文摘Recent studies found that in the context of global warming, the observed tropical cyclones （TCs） exhibit signific-ant poleward migration trend in terms of the mean latitude where TCs reach their lifetime-maximum intensity in the western North Pacific （WNP）. This poleward migration of TC tracks can be attributed to not only anthropogenic for-cing （e.g., continuous increase of sea surface temperature （SST））, but also impacts of other factors （e.g., natural vari- ability）. In the present study, to eliminate the impacts of other factors and thus focus on the impact of unvaried SST on climatological WNP TC tracks, the mesoscale Weather Research and Forecasting （WRF） model is used to con- duct a suite of idealized sensitivity experiments with increased SST. Comparisons among the results of these experi- ments show the possible changes in climatological TC track, TC track density, and types of TC track in the context of SST increase. The results demonstrate that under the warmer SST conditions, the climatological mean TC track sys-tematically shifts poleward significantly in the WNP, which is consistent with the previous studies. Meanwhile, the ocean warming also leads to the decreased （increased） destructive potential of TCs in low （middle） latitudes, and thus northward migration of the region where TCs have the largest impact. Further results imply the possibility that under the ocean warming, the percentage of TCs with westward/northwestward tracks decreases/increases distinctly.
