Thin film methods and X ray energy dispersive technique were applied to analyze sulfate-containing particles inBeijing in order to examine their features and sources. Atmospheric aerosol particles were collected on el...Thin film methods and X ray energy dispersive technique were applied to analyze sulfate-containing particles inBeijing in order to examine their features and sources. Atmospheric aerosol particles were collected on electron microscope meshes according to two size ranges: coarse particles (r>0.5μm) and fine particles (0.5μm>r>0. 1μm) by using a two-stage impactor. It was found that more than seventy percent of the fine particles and about twenty percentof the coarse particles were sulfate-containing particles. These particles were formed mainly through heterogeneousnucleation. The element composition analyses revealed that the atmospheric aerosol particles in Beijing were domi-nated by crustal particles and construction dust.展开更多
The vertical and horizontal propagation of internal gravity waves forced by a local thermal source at the lowerboundary is examined using the irrotational two-dimensional model developed by Zhang et al. (1995).The sou...The vertical and horizontal propagation of internal gravity waves forced by a local thermal source at the lowerboundary is examined using the irrotational two-dimensional model developed by Zhang et al. (1995).The sourcegenerates waves with the same absolute frequency 1/15 d-1 but different wavenumber.Internal gravity waves withwide spreading frequencies and wavenumbers appear due to wave-wave interactions. The foreced waves iW (westward-propagating with wavenumber 1)and iE (eastward-propagating with wavenumber 1),whose absolute phasespeeds are 31 m s-1,are predominant. Other forced waves with smaller phase speeds are relatively weaker.Thesewaves interact with the zonal mean flow,causing the flow to alternate with easterly and westerly with a 32-month period. The absolute maximum wind speeds of easterly and westerly are 35 m s-l which is larger than the largest phasespeed of forced waves. The forced waves iE and iW may accelerate easterly and westerly up to i 31 m s',respectively.The excessive accelerations are due to the self--acceleration of waves iE and iW or newly generated highfrequency waves iE and IW.The horizontal propagation of the waves are mainly affected by the forcing and wave--flow interactions whichlead to fast-slow variations of wave phase speed and amplitude.展开更多
A zonalwetiCal two-dimensional equatorial model is used to study the PO ̄ty that the long Period oSCillation of the zonal mean now occurring in the lower equatorial stratosphere(QBO) is cause by local thermal activihe...A zonalwetiCal two-dimensional equatorial model is used to study the PO ̄ty that the long Period oSCillation of the zonal mean now occurring in the lower equatorial stratosphere(QBO) is cause by local thermal activihes at the tropiCal tropopause.The model sumesfully reproduces Q ̄like o ̄tions of the zonal mean now,suggeshng that the lOCal heating or cooling at the trOPical trOPOpose is Probably the main  ̄n of QBO,s generahon. The analysis of the dependence of the oedllahon on the wave foeing iudicatw that the o ̄hon is not areaible to the forCing scale.The model can reproduce QBO--like oscillahons with any forCing ̄if the forcing Period and amplitude take appropriate valuex, proving that the inaneal cavity waves ge ̄od by lOCal thermal sough take much important roles in QBO.展开更多
文摘Thin film methods and X ray energy dispersive technique were applied to analyze sulfate-containing particles inBeijing in order to examine their features and sources. Atmospheric aerosol particles were collected on electron microscope meshes according to two size ranges: coarse particles (r>0.5μm) and fine particles (0.5μm>r>0. 1μm) by using a two-stage impactor. It was found that more than seventy percent of the fine particles and about twenty percentof the coarse particles were sulfate-containing particles. These particles were formed mainly through heterogeneousnucleation. The element composition analyses revealed that the atmospheric aerosol particles in Beijing were domi-nated by crustal particles and construction dust.
文摘The vertical and horizontal propagation of internal gravity waves forced by a local thermal source at the lowerboundary is examined using the irrotational two-dimensional model developed by Zhang et al. (1995).The sourcegenerates waves with the same absolute frequency 1/15 d-1 but different wavenumber.Internal gravity waves withwide spreading frequencies and wavenumbers appear due to wave-wave interactions. The foreced waves iW (westward-propagating with wavenumber 1)and iE (eastward-propagating with wavenumber 1),whose absolute phasespeeds are 31 m s-1,are predominant. Other forced waves with smaller phase speeds are relatively weaker.Thesewaves interact with the zonal mean flow,causing the flow to alternate with easterly and westerly with a 32-month period. The absolute maximum wind speeds of easterly and westerly are 35 m s-l which is larger than the largest phasespeed of forced waves. The forced waves iE and iW may accelerate easterly and westerly up to i 31 m s',respectively.The excessive accelerations are due to the self--acceleration of waves iE and iW or newly generated highfrequency waves iE and IW.The horizontal propagation of the waves are mainly affected by the forcing and wave--flow interactions whichlead to fast-slow variations of wave phase speed and amplitude.
文摘A zonalwetiCal two-dimensional equatorial model is used to study the PO ̄ty that the long Period oSCillation of the zonal mean now occurring in the lower equatorial stratosphere(QBO) is cause by local thermal activihes at the tropiCal tropopause.The model sumesfully reproduces Q ̄like o ̄tions of the zonal mean now,suggeshng that the lOCal heating or cooling at the trOPical trOPOpose is Probably the main  ̄n of QBO,s generahon. The analysis of the dependence of the oedllahon on the wave foeing iudicatw that the o ̄hon is not areaible to the forCing scale.The model can reproduce QBO--like oscillahons with any forCing ̄if the forcing Period and amplitude take appropriate valuex, proving that the inaneal cavity waves ge ̄od by lOCal thermal sough take much important roles in QBO.