A mesoscale coupled atmosphere–ocean model has been developed based on the GRAPES（Global and Regional Assimilation and Prediction System） regional typhoon model（GRAPES_TYM） and ECOM-si（estuary, coast and ocean m...A mesoscale coupled atmosphere–ocean model has been developed based on the GRAPES（Global and Regional Assimilation and Prediction System） regional typhoon model（GRAPES_TYM） and ECOM-si（estuary, coast and ocean model（semi-implicit））. Coupling between the typhoon and ocean models was conducted by exchanging wind stress, heat, moisture fluxes, and sea surface temperatures（SSTs） using the coupler OASIS3.0. Numerical prediction experiments were run with and without coupling for the case of Typhoon Muifa in the western North Pacific. To investigate the impact of using more accurate SST information on the simulation of the track and the intensity of Typhoon Muifa, experiments were also conducted using increased SST resolution in the initial condition field of the control test. The results indicate that increasing SST resolution in the initial condition field somewhat improved the intensity forecast, and use of the coupled model improved the intensity forecast significantly, with mean absolute errors in maximum wind speed within 48 and 72 h reduced by 32% and 20%, respectively. Use of the coupled model also resulted in less pronounced over-prediction of the intensity of Typhoon Muifa by the GRAPES_TYM. Moreover, the effects of using the coupled model on the intensity varied throughout the different stages of the development of Muifa owing to changes in the oceanic mixed layer depth. The coupled model had pronounced effects during the later stage of Muifa but had no obvious effects during the earlier stage. The SSTs predicted by the coupled model decreased by about 5–6℃ at most after the typhoon passed, in agreement with satellite data. Furthermore, based on analysis on the sea surface heat flux, wet static energy of the boundary layer, atmospheric temperature, and precipitation forecasted by the coupled model and the control test, the simulation results of this coupled atmosphere–ocean model can be considered to reasonably reflect the primary mechanisms underlying the interactions between tropical cyclones and oceans.展开更多
POM (Princeton ocean model) tentatively taken as the ocean part of an ocean-land atmosphere coupled modcl is verified for the ultimate purpose of studying the landfall process of tropical cyclone (TC) in the western N...POM (Princeton ocean model) tentatively taken as the ocean part of an ocean-land atmosphere coupled modcl is verified for the ultimate purpose of studying the landfall process of tropical cyclone (TC) in the western North Pacific. The POM is tested with monthly mean wind stress in the summer and given lateral boundary conditions. The results indicate that the equilibrium state of the ocean is in accordance with the climate mean, with the error in sea surface temperature (salinity) less than 0.5 ℃ (0.5). The simulated occan currents are reasonable as well.Several numerical experiments are designed to verify the oceanic response to a stationary or moving TC. It is found that the results agree fairly well with the previous work, including both the drop magnitude and the distribution ofsca temperature. Compared with the simple two-layer ocean model used by some other studies, the response of the ocean to a TC is more logical here. The model is also verified in a real case with a TC passing the neighborhood of a buoy station. It is shown that the established ocean model can basically reproduce the sea surface temperature change as observed.展开更多
Impacts of the four-dimensional variation （4DVAR） assimilation of Tropical Rainfall Measuring Mission （TRMM）/TMI surface rainfall rate （SRR） on the initialization and simulation of TC Danas in 2001 are studied. ...Impacts of the four-dimensional variation （4DVAR） assimilation of Tropical Rainfall Measuring Mission （TRMM）/TMI surface rainfall rate （SRR） on the initialization and simulation of TC Danas in 2001 are studied. A number of sensitivity experiments are designed to evaluate the performance of assimilation during the particular stage when Danas developed from a tropical depression towards a typhoon, as well as an abrupt turning. Under the dynamic and thermodynamic constraints of meso-scale model and the 4DVAR, the TRMM SRR data are directly assimilated in high horizontal resolution （ 18 kin）. On the basis of the adjustment of initial model field, 4DVAR of TRMM SRR considerably improved the depiction of TC＇ s structure and rainfall. The same explanation can also be given to the enhancement of simulation on TC＇ s intensity and track. In comparison with the popular idea of twice steps of SRR assimilation, namely, 4DVAR pins 1DVAR, the retrieval error is expected to be avoided in the procedure of direct 4DVAR. In addition, the TRMM SRR 4DVAR within a high-resolution model can take into account as much information as observed and is expected to be performed in operational use if the observed rainfall data are routinely available.展开更多
China is one of the countries most severely suffering from tropical cyclones. The exact and timely forecasting and warning is of significant importance in fighting against tropical cyclones and mitigating their impact...China is one of the countries most severely suffering from tropical cyclones. The exact and timely forecasting and warning is of significant importance in fighting against tropical cyclones and mitigating their impacts on China. The numerical weather prediction （NWP） system for tropical cyclone rainfall and strong wind is going to play a more and more important role. There is also a need for timely and user friendly modem warning services in order to provide the governments and relevant authorities at all levels and general public with typhoon forecasts and information about the associated disasters and response strategy services.展开更多
Typhoon Imbudo was a super-typhoon over the northwestern Pacific in 2003. It caused tremendous damage when it made landfalls in the Philippines and China. This paper documents observational analyses of Typhoon Imbudo ...Typhoon Imbudo was a super-typhoon over the northwestern Pacific in 2003. It caused tremendous damage when it made landfalls in the Philippines and China. This paper documents observational analyses of Typhoon Imbudo during its landfall in China. All available observations are used to study its motion, intensity changes, convection, structure and precipitation. Best-track data indicate that Imbudo moved west-northwestward until 1800 UTC 23 July and then turned northwestward. FNL (final) analysis data show that the motion of Imbudo is dominated by changes of the subtropical high. At Imbudo's mature stage, the minimum sea level pressure dropped to 910 hPa and the maximum sustained winds were as high as 67 m s 1, which is the intensity of a super-typhoon. The surface wind field exhibited asymmetric characteristics. Polar-orbiting satellite imagery also manifested convective asymmetry before Imbudo made landfall in China. Analyzed the vertical wind shear, it is shown that the convection has a downshear-left pattern. All kinds of precipitation data were used to identify the asymmetric characteristic of the rainfall associated with the Imbudo. The maximum rainfalls were located in the southern boundary area between Guangxi and Guangdong. However, the lack of in situ observations limited further analyses of this typhoon.展开更多
基金The National Basic Research and Development Program(973 Program)of China under contract No.2009CB421506the National Natural Science Foundation of China under contract No.40975035China Meteorological Administration GRAPES Research Fund
文摘A mesoscale coupled atmosphere–ocean model has been developed based on the GRAPES（Global and Regional Assimilation and Prediction System） regional typhoon model（GRAPES_TYM） and ECOM-si（estuary, coast and ocean model（semi-implicit））. Coupling between the typhoon and ocean models was conducted by exchanging wind stress, heat, moisture fluxes, and sea surface temperatures（SSTs） using the coupler OASIS3.0. Numerical prediction experiments were run with and without coupling for the case of Typhoon Muifa in the western North Pacific. To investigate the impact of using more accurate SST information on the simulation of the track and the intensity of Typhoon Muifa, experiments were also conducted using increased SST resolution in the initial condition field of the control test. The results indicate that increasing SST resolution in the initial condition field somewhat improved the intensity forecast, and use of the coupled model improved the intensity forecast significantly, with mean absolute errors in maximum wind speed within 48 and 72 h reduced by 32% and 20%, respectively. Use of the coupled model also resulted in less pronounced over-prediction of the intensity of Typhoon Muifa by the GRAPES_TYM. Moreover, the effects of using the coupled model on the intensity varied throughout the different stages of the development of Muifa owing to changes in the oceanic mixed layer depth. The coupled model had pronounced effects during the later stage of Muifa but had no obvious effects during the earlier stage. The SSTs predicted by the coupled model decreased by about 5–6℃ at most after the typhoon passed, in agreement with satellite data. Furthermore, based on analysis on the sea surface heat flux, wet static energy of the boundary layer, atmospheric temperature, and precipitation forecasted by the coupled model and the control test, the simulation results of this coupled atmosphere–ocean model can be considered to reasonably reflect the primary mechanisms underlying the interactions between tropical cyclones and oceans.
基金sponsored by the National Natural Science Foundation of China under contrct Nos 40575030,40275018 and 49975014.
文摘POM (Princeton ocean model) tentatively taken as the ocean part of an ocean-land atmosphere coupled modcl is verified for the ultimate purpose of studying the landfall process of tropical cyclone (TC) in the western North Pacific. The POM is tested with monthly mean wind stress in the summer and given lateral boundary conditions. The results indicate that the equilibrium state of the ocean is in accordance with the climate mean, with the error in sea surface temperature (salinity) less than 0.5 ℃ (0.5). The simulated occan currents are reasonable as well.Several numerical experiments are designed to verify the oceanic response to a stationary or moving TC. It is found that the results agree fairly well with the previous work, including both the drop magnitude and the distribution ofsca temperature. Compared with the simple two-layer ocean model used by some other studies, the response of the ocean to a TC is more logical here. The model is also verified in a real case with a TC passing the neighborhood of a buoy station. It is shown that the established ocean model can basically reproduce the sea surface temperature change as observed.
基金the National Natural Science Foundation of China contract Nos 40275018,49975014,40333025the public welfare project sponsored by the Ministry of Science and Technology of China under contract No.2005DIB3J104.
文摘Impacts of the four-dimensional variation （4DVAR） assimilation of Tropical Rainfall Measuring Mission （TRMM）/TMI surface rainfall rate （SRR） on the initialization and simulation of TC Danas in 2001 are studied. A number of sensitivity experiments are designed to evaluate the performance of assimilation during the particular stage when Danas developed from a tropical depression towards a typhoon, as well as an abrupt turning. Under the dynamic and thermodynamic constraints of meso-scale model and the 4DVAR, the TRMM SRR data are directly assimilated in high horizontal resolution （ 18 kin）. On the basis of the adjustment of initial model field, 4DVAR of TRMM SRR considerably improved the depiction of TC＇ s structure and rainfall. The same explanation can also be given to the enhancement of simulation on TC＇ s intensity and track. In comparison with the popular idea of twice steps of SRR assimilation, namely, 4DVAR pins 1DVAR, the retrieval error is expected to be avoided in the procedure of direct 4DVAR. In addition, the TRMM SRR 4DVAR within a high-resolution model can take into account as much information as observed and is expected to be performed in operational use if the observed rainfall data are routinely available.
文摘China is one of the countries most severely suffering from tropical cyclones. The exact and timely forecasting and warning is of significant importance in fighting against tropical cyclones and mitigating their impacts on China. The numerical weather prediction （NWP） system for tropical cyclone rainfall and strong wind is going to play a more and more important role. There is also a need for timely and user friendly modem warning services in order to provide the governments and relevant authorities at all levels and general public with typhoon forecasts and information about the associated disasters and response strategy services.
基金This work was partly supported by the National Nature Science Foundation of China under the grant numbers of 40275033 and 40240420564the open project of the Shanghai Hphoon Institute.
文摘Typhoon Imbudo was a super-typhoon over the northwestern Pacific in 2003. It caused tremendous damage when it made landfalls in the Philippines and China. This paper documents observational analyses of Typhoon Imbudo during its landfall in China. All available observations are used to study its motion, intensity changes, convection, structure and precipitation. Best-track data indicate that Imbudo moved west-northwestward until 1800 UTC 23 July and then turned northwestward. FNL (final) analysis data show that the motion of Imbudo is dominated by changes of the subtropical high. At Imbudo's mature stage, the minimum sea level pressure dropped to 910 hPa and the maximum sustained winds were as high as 67 m s 1, which is the intensity of a super-typhoon. The surface wind field exhibited asymmetric characteristics. Polar-orbiting satellite imagery also manifested convective asymmetry before Imbudo made landfall in China. Analyzed the vertical wind shear, it is shown that the convection has a downshear-left pattern. All kinds of precipitation data were used to identify the asymmetric characteristic of the rainfall associated with the Imbudo. The maximum rainfalls were located in the southern boundary area between Guangxi and Guangdong. However, the lack of in situ observations limited further analyses of this typhoon.
