Low-frequency phenomena in the atmosphere are intimately related to stationary waves and, in a sense, the former may even be viewed as the time-varying part of the quasi-stationary waves themselves, Much attention has...Low-frequency phenomena in the atmosphere are intimately related to stationary waves and, in a sense, the former may even be viewed as the time-varying part of the quasi-stationary waves themselves, Much attention has been focused on nonlinear interactions in the conceptual study on stationary waves. Linear and nonlinear primitive-equation baroclinic spectral models are adopted to investigate the response of stationary waves to large- scale mechanical forcing and steady-state thermal forcing, both idealized and realistic, followed by calculations of the EP fluxes and three-dimensional wave activity fluxes (Plumb, 1985) for both the linear and nonlinear solu- tions. Results show that when the forcing source grows intense enough to be comparable to the real one, non- linear interaction becomes very important, especially for the maintenance of tropical and polar stationary waves. Care should be taken, however, in using the EP flux and Plumb's 3-D flux for diagnostic analysis of observational data as they are highly sensitive to nonlinear interaction.展开更多
In terms of the expansion by extended empirical orthogonal function (EEOF) with data of ECMWF WMO and of outgoing longwave radiation(OLR) furnished by the NOAA polar-orbiting satellite,a study is made of November 1981...In terms of the expansion by extended empirical orthogonal function (EEOF) with data of ECMWF WMO and of outgoing longwave radiation(OLR) furnished by the NOAA polar-orbiting satellite,a study is made of November 1981 to March 1982 low-frequency (30--60 day)summer monsoon activity in the Indone- sian-North Australian zone (INAZ) together with its relation to atmospheric circulations in the Northern and Southern Hemispheres. Results show that at 850 hPa the southward blowing low-frequency NE(SW)wind from the eastern Asian coast changes, after crossing the euqator, to summer NW (SE) monsoon in the INAZ, which, when converging with (diverging from) the western-Australian enforced low-frequency SW (NE) wind, brings about strengthened (weakened) convection in the summer monsoon area and its eastward advance, with corresponding low- frequency variation shown in 850 hPa geopotential height. These outcomes are similar to those from the study of non-filtered actual observations, leading to the conclusion that the component of low-frequency variation illustrates major features characteristic of the variation in the tropical circulation.展开更多
In this paper,by using spectral method,the monthly-and seasonal-scale atmospheric diabatic heat flow(ADHF) departure fields are diagnosed in the period of 1964—1985 with 6 El Nino years and 6 anti-El Nino years over ...In this paper,by using spectral method,the monthly-and seasonal-scale atmospheric diabatic heat flow(ADHF) departure fields are diagnosed in the period of 1964—1985 with 6 El Nino years and 6 anti-El Nino years over the Northern hemisphere(NH).The results show that El Nino phenomena have pronounced influence on the ADHF depar- ture fields.The response of atmosphere exhibits a preferred arrangement of organizing positive and negative departure centers at low,middle and high latitudes.In anti-El Nino years,the response has the same forms as in El Nino years, but departure centers are opposite in phase.Furthermore,ADHF departure shows low-frequency oscillation in El Nino years and anti-El Nino years.The center of difference in departure between El Nino and anti-El Nino years displays a bi-monthly oscillation. Finally,through air-sea correlation analysis,it is pointed out that the SST anomaly is the most important cause for ADHF anomaly.展开更多
Based on the conservation of entropy and potential vorticity in adiabatic atmospheric motion without the consideration of friction,calculation is made of the trajectory of a particle on an isentropic surface by use of...Based on the conservation of entropy and potential vorticity in adiabatic atmospheric motion without the consideration of friction,calculation is made of the trajectory of a particle on an isentropic surface by use of the data of FGGE III-b.Results of several calculation schemes of the trajectory discussed show that the local data interpolation and Runge-Kutta time-integral scheme is the best.The calculated trajectory reflects the large-scale atmospheric motion only and the small-scale motion emerges as a deviation term of the calculated trajectory.And then the outbreak and propagation of planetary wave are studied by means of the deformation of a material line,with the result showing that the material line can be tracked in the trop- osphere only in a few days,beyond which the interaction between the small-scale waves and large-scale motion leads to its dramatical twisting and deformation.Therefore,the Lagrangian method is assumed to be an effective means of diagnostic research in the nonlinear intcraction in atmospheric circulation,in addition to the general study of the atmospheric circulation.展开更多
文摘Low-frequency phenomena in the atmosphere are intimately related to stationary waves and, in a sense, the former may even be viewed as the time-varying part of the quasi-stationary waves themselves, Much attention has been focused on nonlinear interactions in the conceptual study on stationary waves. Linear and nonlinear primitive-equation baroclinic spectral models are adopted to investigate the response of stationary waves to large- scale mechanical forcing and steady-state thermal forcing, both idealized and realistic, followed by calculations of the EP fluxes and three-dimensional wave activity fluxes (Plumb, 1985) for both the linear and nonlinear solu- tions. Results show that when the forcing source grows intense enough to be comparable to the real one, non- linear interaction becomes very important, especially for the maintenance of tropical and polar stationary waves. Care should be taken, however, in using the EP flux and Plumb's 3-D flux for diagnostic analysis of observational data as they are highly sensitive to nonlinear interaction.
基金The study is jointly supported by National Natural Science Foundation of Chinathe State Meteorological Administration Monsoon Research Funds.
文摘In terms of the expansion by extended empirical orthogonal function (EEOF) with data of ECMWF WMO and of outgoing longwave radiation(OLR) furnished by the NOAA polar-orbiting satellite,a study is made of November 1981 to March 1982 low-frequency (30--60 day)summer monsoon activity in the Indone- sian-North Australian zone (INAZ) together with its relation to atmospheric circulations in the Northern and Southern Hemispheres. Results show that at 850 hPa the southward blowing low-frequency NE(SW)wind from the eastern Asian coast changes, after crossing the euqator, to summer NW (SE) monsoon in the INAZ, which, when converging with (diverging from) the western-Australian enforced low-frequency SW (NE) wind, brings about strengthened (weakened) convection in the summer monsoon area and its eastward advance, with corresponding low- frequency variation shown in 850 hPa geopotential height. These outcomes are similar to those from the study of non-filtered actual observations, leading to the conclusion that the component of low-frequency variation illustrates major features characteristic of the variation in the tropical circulation.
文摘In this paper,by using spectral method,the monthly-and seasonal-scale atmospheric diabatic heat flow(ADHF) departure fields are diagnosed in the period of 1964—1985 with 6 El Nino years and 6 anti-El Nino years over the Northern hemisphere(NH).The results show that El Nino phenomena have pronounced influence on the ADHF depar- ture fields.The response of atmosphere exhibits a preferred arrangement of organizing positive and negative departure centers at low,middle and high latitudes.In anti-El Nino years,the response has the same forms as in El Nino years, but departure centers are opposite in phase.Furthermore,ADHF departure shows low-frequency oscillation in El Nino years and anti-El Nino years.The center of difference in departure between El Nino and anti-El Nino years displays a bi-monthly oscillation. Finally,through air-sea correlation analysis,it is pointed out that the SST anomaly is the most important cause for ADHF anomaly.
文摘Based on the conservation of entropy and potential vorticity in adiabatic atmospheric motion without the consideration of friction,calculation is made of the trajectory of a particle on an isentropic surface by use of the data of FGGE III-b.Results of several calculation schemes of the trajectory discussed show that the local data interpolation and Runge-Kutta time-integral scheme is the best.The calculated trajectory reflects the large-scale atmospheric motion only and the small-scale motion emerges as a deviation term of the calculated trajectory.And then the outbreak and propagation of planetary wave are studied by means of the deformation of a material line,with the result showing that the material line can be tracked in the trop- osphere only in a few days,beyond which the interaction between the small-scale waves and large-scale motion leads to its dramatical twisting and deformation.Therefore,the Lagrangian method is assumed to be an effective means of diagnostic research in the nonlinear intcraction in atmospheric circulation,in addition to the general study of the atmospheric circulation.
